Anesthesia for Liposuction and Abdominoplasty
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Chapter 2
Anesthesia for Liposuction and Abdominoplasty 2
Gary Dean Bennett
2.1 tered, the personnel to be involved in the care and mon-
Introduction itoring of the patient, the postoperative pain manage-
ment, and the discharge criteria used. Therefore, it is
Since the development of the first outpatient surgical incumbent on the surgeon to understand current stan-
program in 1966 and the first freestanding surgical dards of anesthesia practice. If the surgeon chooses to
centers in 1969, the number of surgeries performed assume the role of the anesthesiologist, then he or she
outside of the hospital setting has dramatically in- must adhere to the same standards that are applied to
creased. An estimated 70 % of all elective surgery is per- the anesthesiologist. While the morbidity and mortali-
formed in an outpatient setting [1], and more than 50 % ty of anesthesia has decreased [9, 10], risk awareness of
of aesthetic plastic surgeons perform most of their pro- anesthesia and surgery must not be relaxed.
cedures in an office setting [2].
The popularity of surgeries performed outside of
2.1.1
the hospital setting is a consequence of multiple fac-
The Surgical Facility
tors. Clearly, economic considerations play a major role
in the shift to ambulatory surgery. Because of greater The surgeon is largely responsible for deciding in
efficiency, these outpatient surgical units have greater which facility the procedure is to be performed. Surgi-
cost-effectiveness [3]. Advances in monitoring capabil- cal facilities may be divided into five main categories:
ities and the adoption of monitoring standards of the
1. Hospital-based inpatient
American Society of Anesthesiologists (ASA) are cred-
2. Hospital-associated ambulatory surgical unit
ited for a reduction of perioperative morbidity and
3. Freestanding surgical center with short-stay
mortality [4]. Advances in pharmacology have resulted
accommodation
in a greater diversity of anesthetic agents with rapid on-
4. Freestanding surgical centers without short-stay
set, shorter duration of action and reduced morbidity
accommodation
[5]. The advent of minimally invasive procedures has
5. Office based operating rooms.
further reduced the need for hospital-based surgeries.
Regulatory agencies such as the American Association Each of these choices has distinct advantages and dis-
of Accreditation of Ambulatory Surgery (AAAASF) and advantages. While convenient and economical, office
the Accreditation Association for Ambulatory Health based surgery is associated with three times the mor-
Care (AAAHC) have helped establish minimum stan- tality of surgeries performed at other types of facilities
dards of care for surgical locations where anesthesia is [11]. Ultimately, patient safety should be the para-
administered. Ambulatory anesthesia has even become mount factor in the final decision. Patients with a risk
a formal subspecialty of anesthesia with the establish- of ASA III undergoing major liposuction or large abdo-
ment of the Society of Ambulatory Anesthesia (SAM- minoplasty should preferentially be treated at hospital-
BA) in 1984. An evaluation of 1.1 million outpatients based or hospital-associated surgical units rather than
revealed that the mortality rate after ambulatory anes- office-based operating rooms [12 – 14].
thesia was 1.5 per 100,000 cases [6]. No deaths occurred If the intended surgical procedure requires general
in 319,000 patients who were monitored in accordance anesthesia or enough sedative-analgesic medication to
with ASA standards [7, 8]. increase the probability of loss of the patient’s life pre-
As a consequence of the shift away from hospital- serving protective reflexes (LPPRs), then, according to
based surgery, the surgeon has adopted a more impor- the law in some states, the surgical facility must be ac-
tant role in the medical decision making process with credited by one of the regulatory agencies (AAAASF or
respect to anesthesia. Frequently, the surgeon decides AAAHC) [15, 16].
on the location of surgery, the extent of the preopera- Regardless of which type of facility is selected or the
tive evaluation, the type of anesthesia to be adminis- type of anesthesia planned, the operating room must30 2 Anesthesia for Liposuction and Abdominoplasty
be equipped with the type of monitors required to ful- ative anesthesia preparation of the patient as an after-
fill the monitoring standards established by the ASA thought must be resisted. Even if an anesthesiologist or
[17], as well as proper resuscitative equipment and re- CRNA is to be involved later, the surgeon bears respon-
suscitative medications [18, 19]. The facility must be sibility for the initial evaluation and preparation of the
staffed by individuals with the training and expertise patient. Thorough preoperative evaluation and prepa-
required to assist in the care of the patient [19, 20]. ration by the surgeon increases the patient’s confi-
Emergency protocols must be established and re- dence, reduces costly and inconvenient last minute de-
hearsed [21]. Optimally, the surgical facility must have lays, and reduces overall perioperative risk to the pa-
ready access to a laboratory in the event a stat laborato- tient [30]. If possible, the preoperative evaluation
ry analysis is required. Finally, a transfer agreement should be performed with the assistance of a spouse,
with a hospital must be established in the event that an parent or significant other so that elements of the
unplanned admission is required [18, 19]. health history or recent symptoms may be more readily
recalled.
A comprehensive preoperative evaluation form is a
2.1.2
useful tool with which to begin the initial assessment.
Personnel
Information contained in the history alone may deter-
One of the most critical elements of successful surgical mine the diagnosis of the medical condition in nearly
outcomes is the personnel assisting the surgeon. Quali- 90 % of patients [31]. While a variety of forms are avail-
fied and experienced assistants may serve as valuable able in the literature, a checklist format to facilitate the
resources potentially reducing morbidity and improv- patient’s recall is probably the most effective [32]. Re-
ing efficiency of the operating room [22, 23]. With an gardless of which format is selected, information re-
office-based operating room the surgeon is responsible garding all prior medical conditions, prior surgeries
for selecting the operating room personnel. and types of anesthetics, current and prior medica-
An anesthesiologist or a Certified Nurse Anesthetist tions, adverse outcomes to previous anesthetics or oth-
(CRNA) may administer anesthesia. The surgeon may er medications, eating disorders, prior use of antiobesi-
prefer to perform the surgery using exclusively local ty medication, and use of dietary supplements, which
anesthesia without parenteral sedation, especially in could contain ephedra, should be disclosed by the pa-
limited liposuctions with the tumescent technique [24]. tient.
However, many surgeons add parenteral sedative or an- A family history of unexpected or early health con-
algesic medications with the local anesthetic. If the sur- ditions such as heart disease, or unexpected reactions,
geon chooses to administer parenteral sedative-analge- such as malignant hyperthermia, to anesthetics or oth-
sic medications, then another designated, licensed, er medications should not be overlooked. Finally, a
preferably experienced individual should monitor the complete review of systems is vital to identifying undi-
patient throughout the perioperative period [25]. Use agnosed, untreated, or unstable medical conditions
of unlicensed, untrained personnel to administer par- that could increase the risk of surgery or anesthesia.
enteral sedative analgesic medication and monitor pa- Last minute revelations of previously undisclosed
tients may increase the risk to the patient. It is also not symptoms, such as chest pain, should be avoided.
acceptable for the nurse monitoring the patient to dou- Indiscriminately ordered or routinely obtained pre-
ble as a circulating nurse [26]. Evidence suggests that operative laboratory testing is now considered to have
anesthesia related deaths more than double if the sur- limited value in the perioperative prediction of mor-
geon also administers the anesthesia [27]. Regardless of bidity and mortality [33 – 37]. In fact, one study showed
who delivers the anesthesia, the surgeon should prefer- no difference in morbidity in healthy patients without
ably maintain current Advanced Cardiac Life Support preoperative screening tests versus a control group
certification (ACLS) and all personnel assisting in the with the standard preoperative tests [38]. Multiple in-
operating room and recovery areas must maintain Ba- vestigations have confirmed that the preoperative his-
sic Life Support Certification [28]. At least one ACLS tory and physical examination is superior to laboratory
certified health provider must remain in the facility un-
til the patient has been discharged [29].
Table 2.1. Guidelines for preoperative testing in healthy pa-
tients (ASA 1 – 11). (Adapted from Roizen et al. [305])
2.1.3 Age Test
Preoperative Evaluation
12 – 40a CBC
The time and energy devoted to the preoperative prep- 40 – 60 CBC, EKG
aration of the surgical patient should be commensurate Greater than 60 CBC, BUN, glucose, ECG, CXR
with the efforts expended on the evaluation and prepa- a Pregnancy test for potentially childbearing females is sug-
ration for anesthesia. The temptation to leave preoper- gested2.1 Introduction 31
Table 2.2. Common indications for additional risk specific testing. (Adapted from Roizen et al. [306])
Electrocardiogram Chest X-ray Electrolytes, glucose, Urinalysis
liver function tests, BUN,
creatinine
History Coronary artery disease, congestive Bronchial asthma, con- Diabetes mellitus, chronic Diabetes mellitus,
heart failure, prior myocardial in- gestive heart failure, renal failure, chronic liver chronic renal dis-
farction, hypertension, hyperthy- chronic obstructive pul- disease, adrenal insuffi- ease, and recent
roidism, hypothyroidism, obesity, monary disease, pulmo- ciency, hypothyroidism, urinary tract in-
compulsive eating disorders, deep nary embolism hyperthyroidism, diuretic fection
venous thrombosis, pulmonary em- use, compulsive eating
bolism, smoking, chemotherapeutic disorders, diarrhea
agents, chemical dependency, chron-
ic liver disease
Symptoms Chest pain, shortness of breath, Chest pain, shortness of Dizziness, generalized Dysuria, urgency,
dizziness breath, wheezing, unex- fatigue or weakness frequency, and
plained weight loss, he- bloody urination
moptysis
Signs Abnormal heart rate or rhythm, hy- Cyanosis, wheezes, rales, Abnormal heart rate or
pertension, cyanosis, peripheral ede- rhonchi, decreased rhythm, peripheral ede-
ma, wheezing, rales, rhonchi breath sounds, peripher- ma, jaundice
al edema, abnormal
heart rate or rhythm
analysis in determining the clinical course of surgery
2.1.4
and anesthesia [39 – 43]. Newer guidelines for the ju-
Preoperative Risk Assessment
dicious use of laboratory screening are now widely
accepted. Table 2.1 outlines a general approach for The ultimate goals of establishing a patient’s level of risk
healthy patients not taking medications. Additional are to reduce the probability of perioperative morbidity
preoperative tests may be indicated for patients with and mortality. The preoperative evaluation is the cru-
prior medical conditions or risk factors for anesthesia cial component of determining the patient’s preopera-
and surgery (Table 2.2). tive risk level. There is compelling evidence to suggest
Consultation from other medical specialists should that the more coexisting medical conditions a patient
be obtained for patients with complicated or unstable has, the greater the risk for perioperative morbidity and
medical conditions. Patients with ASA III risk designa- mortality [25, 44]. Identification of preoperative medi-
tion should be referred to the appropriate medical spe- cal conditions helps reduce perioperative mortality.
cialist prior to elective surgery [25]. The consultant’s A variety of indexing systems have been proposed to
role is to determine if the patient has received optimal help stratify patients according to risk factors. One
treatment and if the medical condition is stable. Addi- such classification, first proposed in 1941 [45], later
tional preoperative testing may be considered neces- modified in 1961 by Dripps [46], and finally adopted by
sary by the consultant. The medical consultant should the ASA in 1984 (Table 2.3) [47], has emerged as the
also assist with stabilization of the medical condition in most widely accepted method of preoperative risk as-
the perioperative period if indicated. If the surgeon has sessment. Numerous studies have confirmed the value
concerns about a patient’s ability to tolerate anesthesia, of the ASA system in predicting which patients are at a
a telephone discussion with an anesthesiologist or even higher risk for morbidity [48] and mortality [49 – 51].
a formal preoperative anesthesia consultation may be Goldman and Caldera established a multifactorial in-
indicated. dex based on cardiac risk factors [52]. This index has
Certain risk factors, such as previously undiagnosed repeatedly demonstrated its usefulness in predicting
hypertension, cardiac arrhythmias, and bronchial perioperative mortality [53, 54]. Physicians should in-
asthma may be identified by a careful physical exami- corporate one of the acceptable risk classification sys-
nation. Preliminary assessment of head and neck anat- tems as an integral part of the preoperative evaluation.
omy to predict possible challenges in the event endo- Multiple authors have documented the association
tracheal intubation is required may serve as an early between morbidity and mortality and the type of sur-
warning to the anesthesiologist or CRNA even if a gen- gery [55 – 58]. The consensus of these studies confirms
eral anesthetic is not planned. For most ambulatory the increased risks of perioperative complications for
surgeries, the anesthesiologist or CRNA evaluates the more invasive surgeries, surgeries with multiple com-
patient on the morning of surgery. bined procedures, surgeries with prolonged duration,
and surgeries with significant blood loss [59]. While32 2 Anesthesia for Liposuction and Abdominoplasty
Table 2.3. The American Society of Anesthesiologists’ Physical index of suspicion for silent ischemia must be main-
Status Classification tained when assessing asymptomatic patients with risk
factors for heart disease, such as smoking, hyperten-
ASA Class I A healthy patient without systemic medical
or psychiatric illness sion, diabetes mellitus, obesity, hyperlipidemia, or
family history of severe heart disease. Patients with
ASA Class II A patient with mild, treated and stable
systemic medical or psychiatric illness known cardiac disease must be evaluated by the inter-
nist or cardiologist to ensure the medical condition is
ASA Class III A patient with severe systemic disease that
is not considered incapacitating optimally managed. When anesthesia is planned, pa-
tients with significant heart disease should preferen-
ASA Class IV A patient with severe systemic, incapacitat-
ing and life threatening disease not neces- tially undergo surgery at a hospital-based surgical unit
sarily correctable by medication or surgery rather than a physician’s office.
ASA Class V A patient considered moribund and not
Most studies have consistently demonstrated that
expected to live more than 24 h patients who have suffered previous myocardial infarc-
tions have a dramatically greater risk of reinfarction
and death if surgery is performed less than 6 months af-
studies correlating the amount of fat aspirate during li- ter the cardiac event [67 – 69]. More recent studies sug-
posuction or the amount of tissue removed during ab- gesting a lower rate of reinfarction [70, 71] involved pa-
dominoplasty with perioperative morbidity and mor- tients who were hospitalized in the intensive care unit
tality have not been performed, it would not be unrea- with invasive hemodynamic monitoring. These studies
sonable to extrapolate conclusions from the previous may not have relevance to patients undergoing elective
studies and apply them to abdominoplasty and lipo- ambulatory surgery. At this time, the prudent choice
suction. Liposuction surgeries with less than 1,500 ml remains to postpone elective surgeries for at least
fat aspirate are generally considered less invasive pro- 6 months after myocardial infarction.
cedures, while liposuctions aspirating more than Goldman et al. established a cardiac risk index [52]
3,000 ml are considered major surgical procedures which has been useful in identifying patients with in-
[19]. As blood loss exceeds 500 cc [59], or the duration termediate risk for cardiac complications in the periop-
of surgery exceeds 2 h, morbidity and mortality in- erative period [53]. Patients with a score greater than
crease [48, 60]. 13 should be referred to a cardiologist for preoperative
evaluation. Dipyridamole thallium scanning and dobu-
tamine stress echocardiography have proven useful in
2.2 predicting adverse perioperative cardiac events [72].
Anesthesia in Patients with Preexisting Disease One reliable and simple screening method to evaluate
cardiac status is exercise tolerance. The ability to in-
Over the past 30 years the morbidity and mortality of crease the heart rate to 85 % of the age-adjusted maxi-
surgery have steadily declined [10]. One hypothesis to mal heart rate is a reliable predictor of perioperative
explain this decline has been the greater recognition of cardiac morbidity [73].
preoperative risk factors and the improved periopera- Despite years of investigation, no one anesthetic
tive medical management of patients with coexisting technique or medication has emerged as the preferen-
diseases. Surgeons who perform outpatient surgery, es- tial method to reduce the incidence of perioperative
pecially office-based surgery, and particularly those complications in patients with cardiac disease [74, 75].
surgeons who choose to administer sedative or analge- Regardless of which anesthesia technique is selected,
sic medication, must appreciate how these medical scrupulous monitoring should serve as the framework
conditions may increase the risk of anesthesia in the for safe anesthetic management. Hemodynamic fluctu-
surgical patient. Furthermore, the surgeon should ations must be avoided to prevent ischemic episodes in
maintain a current, working understanding of the eval- the perioperative period.
uation and treatment of these medical conditions.
2.2.2
2.2.1 Obesity
Cardiac Disease
The current prevalence of obesity in the USA is esti-
Cardiac related complications, including myocardial mated to be 55 % of the population [76]. It is reasonable
infarction and congestive heart failure, are the leading to assume that patients undergoing major liposuction
cause of perioperative mortality [62, 63]. Most patients or abdominoplasty have a greater incidence of obesity.
with heart disease can be identified with a careful pre- The most widely accepted method of quantifying the
operative history and physical [64]. Since 80 % of all ep- level of obesity is the body mass index (BMI), which is
isodes of myocardial ischemia are silent [65, 66], a high determined by weight (kg)/height (m)2. Patients with a2.2 Anesthesia in Patients with Preexisting Disease 33
BMI over 30 are considered obese, while a BMI over 35 pnea, chest pain, and irregular heart rate, murmur, and
indicates morbid obesity [77]. edema, some patients remain asymptomatic [91].
The risk factors associated with obesity such as dia- Patients who have developed pulmonary hyperten-
betes mellitus, hypertension, heart disease, sleep ap- sion and valvular heart disease as a result of these med-
nea, and occult liver disease [78] should concern clini- ications are predisposed to fatal cardiac arrhythmias,
cians administering anesthesia to patients with obesity. congestive heart failure, and intractable hypotension.
A thorough preoperative evaluation must rule out these Some authors advocate a cardiac evaluation with echo-
occult risk factors prior to elective surgery. cardiogram and continuous wave Doppler imaging
Anatomical abnormalities make airway control with color-flow examination for any patient who has
challenging [79] and endotracheal intubation hazard- taken these antiobesity medications prior to surgery.
ous [80]. The combination of a higher gastric volume Sustained hypotension may not respond to ephedrine,
and lower pH with a higher frequency of esophageal re- a popular vasopressor. Phenylephrine is the treatment
flux results in a higher risk of pulmonary aspiration of choice for hypotension in these patients [91].
[81]. Pulmonary function can be severely restricted
even in an upright position [82]. However, in the supine
2.2.3
position, pulmonary function is further reduced [83].
Hypertension
Pulmonary function is further compromised in the
anesthetized patient. Because of these cardiopulmo- Early studies revealed a significantly increased risk of
nary abnormalities, obese patients develop hypoxemia perioperative mortality in patients with untreated hy-
more quickly [84]. This respiratory impairment may pertension [92, 93]. The reduction in mortality from
persist up to 4 days after surgery [85]. Even distribu- cardiovascular and cerebral vascular disease resulting
tion and metabolism of medications vary significantly from proper treatment of hypertension has been widely
and often unpredictably in the obese patient [86]. accepted [94 – 96]. Although somewhat controversial,
Given the increased risk of perioperative morbidity most authors concur that preoperative stabilization of
and mortality of anesthesia, morbidly obese patients hypertension reduces perioperative cardiovascular
(BMI greater than 35) undergoing major surgery and complications such as ischemia [97 – 99]. Patients with
anesthesia of any type should preferentially be restrict- undiagnosed or poorly controlled hypertension should
ed to a hospital based surgical facility. In general, these be identified early in the preoperative preparation pro-
patients should not be considered candidates for am- cess and referred to the family physician or internist for
bulatory surgery. Anesthesia delivered in the office set- evaluation and treatment.
ting should be restricted to patients with a BMI less Physicians should not mistakenly attribute severe
than 35. hypertension to the patient’s preoperative anxiety.
Premedication with metaclopromide, a dopamine Because of the risk of rebound hypertension, antihy-
receptor antagonist, increases gastric motility and low- pertension medications should be continued up to the
er esophageal sphincter tone. A histamine receptor- morning of surgery [100], except for angiotensin-con-
blocking agent such as ranitidine used with metaclo- verting (ACE) inhibitors, which have been associated
promide the evening before and on the morning of sur- with hypotension during induction of general anesthe-
gery reduces the risk of pulmonary aspiration [87]. sia [101].
Because of the increased risks of deep venous Mild to moderate perioperative hypertension may
thrombosis (DVT) [88] and pulmonary embolism (PE) be a response to inadequate general or local anesthesia
[89], prophylactic measures such as lower extremity or pain control. In these cases, pain is usually accompa-
pneumatic compression devices and early ambulation nied by other signs, such as the patient’s complaints, in
should be used. the case of anesthesia for the conscious patient, tachy-
An undetermined number of patients self-adminis- cardia, and tachypnea. If hypertension persists despite
ter herbal dietary supplements. Many of these supple- additional local anesthetic or analgesic medication,
ments contain ephedra alkaloids, which may predispo- then treatment of the blood pressure is indicated. Mod-
se the patient to perioperative hypertension and cardi- erate to severe blood pressure elevations occurring
ac arrhythmias [90]. Some herbals may result in the in- during the surgery or during recovery should be treat-
creased incidence of bleeding from coumadin-like sub- ed using one or more of the antihypertensive agents
stances. Antiobesity medications such as aminorex fu- available.
marate, dexfenfluramine (Redux), fenfluramine (pon- Perioperative hypertension, especially if the hyper-
damin) and phentermine (Ionamin, Adipex-P, Fastin, tension is accompanied by tachycardia, may be treated
Oby-Cap, Obenix, Oby-trim, Zantryl) are associated with a beta-adrenergic blocking agent such as propran-
with pulmonary hypertension and valvular heart dis- olol in judiciously administered, intravenous doses of
ease, even with as little as 2 months of use. While most 0.5 mg at 10- to 15-min intervals. Even small doses of a
patients develop symptoms such as palpitations, dys- beta-adrenergic blocking agent have been shown to re-34 2 Anesthesia for Liposuction and Abdominoplasty
duce the incidence of cardiac ischemia [99]. Labetolol, sulin and patients with type II diabetes should not take
an antihpertensive agent with combined alpha-adren- the oral hypoglycemia agents on the morning of sur-
ergic and beta-adrenergic blocking properties, admin- gery. Diabetic patients should be scheduled the first
istered in 5 – 10 mg doses every 10 min, is also a safe case in the morning to minimize the risk of hypoglyce-
and effective alternative for treating both hypertension mia during the NPO period. After the patient arrives,
and tachycardia [102]. preoperative fasting glucose should be checked and
Nifedipine (10 mg s.l.), a potent systemic and coro- then an infusion of 5 % dextrose is generally initiated at
nary arteriolar dilator, effectively reduces blood pres- 1 – 2 ml/kg/h and continued until oral fluids are tolerat-
sure, and may be administered in a conscious patient. ed in the recovery period. Usually, one-half of the pa-
The effect of nifedipine may be additive if given with tient’s scheduled dose of insulin is administered after
narcotics or inhalational anesthetic agents. Because ni- the intravenous dextrose is begun [112].
fedipine and lidocaine are both highly protein bound, For surgeries longer than 2 h, at least one peripheral
caution must be exercised when administering nifedi- blood glucose should be measured, especially if the pa-
pine after high dose lidocaine tumescent anesthesia has tient is receiving general anesthesia. Blood glucose
been administered to avoid possible toxic effects of the above 200 mg/dl may be effectively managed with a
lidocaine [103]. sliding scale of insulin [113]. Treatment regimens di-
For severe hypertension, hydralazine, a potent vaso- rected toward tighter control of the blood sugar, such as
dilator, may be useful in 2.5 – 5 mg doses intravenously continuous insulin infusions, do not necessarily im-
at 10 – 15 min intervals. The effects of hydralazine may prove the perioperative outcome [114, 115]. It is imper-
be delayed up to 20 min and its effects prolonged. Hy- ative that, prior to discharge, patients are able to toler-
dralazine may cause tachycardia or hypotension, espe- ate oral intake without nausea and vomiting. A final
cially if the patient is hypovolemic [104]. glucose level should be checked prior to discharge.
2.2.4 2.2.5
Diabetes Mellitus Pulmonary Disease
Although patients with diabetes mellitus have a sub- Bronchial asthma, chronic bronchitis, chronic obstruc-
stantially increased surgical mortality rate than non- tive pulmonary disease, obesity, history of smoking,
diabetic patients [105], these complications are more and recent upper respiratory infection are the most
likely to be a consequence of the end-organ disease common medical conditions which may influence pul-
such as cardiovascular disease, renal disease, and al- monary function in the perioperative period. An esti-
tered wound healing [106 – 108]. While evidence sug- mated 4.5 % of the population may suffer some form of
gests that tight control of blood sugar in insulin-depen- reactive airway disease [116]. If these medical condi-
dent diabetics slows the progression of end-organ dis- tions are identified in the preoperative history, a thor-
ease [109], tight control is associated with additional ough evaluation of the patient’s pulmonary function
risks such as hypoglycemia and even death [110]. should ensure. As with other medical conditions, a
The preoperative evaluation should identify diabetic careful history may help separate patients with these
patients with poor control as well as medical condi- medical conditions into low and high risk groups, espe-
tions associated with diabetes such as cardiovascular cially since the degree of preoperative respiratory dys-
disease and renal insufficiency. Diabetic patients have a pnea closely correlates with postoperative mortality
greater incidence of silent myocardial ischemia [111]. [117]. Using a simple grading scale, the patients’ preop-
Minimum preoperative analysis includes fasting blood erative pulmonary function can be estimated (Ta-
sugar, glycosylated hemoglobin, electrolytes, BUN, cre- ble 2.4).
atinine and EKG. If any doubt exists regarding the pa- Patients with level 2 dyspnea or greater should be re-
tient’s medical stability, consultation should be ob- ferred to a pulmonologist for more complete evalua-
tained from the diabetologist, cardiologist, or nephrol-
ogist if needed. Patients with brittle diabetes or with
other coexisting medical conditions should be referred Table 2.4. Grade of dyspnea while walking. (Adapted from
to a hospital-based surgical unit, especially if general Boushy et al. [117])
anesthesia is contemplated. Level Clinical response
The goal of perioperative management of stable type
0 No dyspnea
I or type II diabetic patients is primarily to avoid hypo- 1 Dyspnea with fast walking only
glycemia. Although patients are generally NPO after 2 Dyspnea with one or two blocks walking
midnight prior to surgery, a glass of clear juice may be 3 Dyspnea with mild exertion (walking around the
taken up to 2 h prior to surgery to avoid hypoglycemia. house)
4 Dyspnea at rest
Patients with type I diabetes should not administer in-2.2 Anesthesia in Patients with Preexisting Disease 35
tion and possibly further medical stabilization. The patients may suffer significant and sustained hypox-
benefits of elective surgery in patients with level 3 and emia. As a result of the pathophysiology of OSA, pa-
4 dyspnea should be carefully weighed against the in- tients develop left and right ventricular hypertrophy
creased risks. Certainly, this group of patients would [126]. Consequently, patients have a higher risk of ven-
not be considered good candidates for outpatient sur- tricular dysarrhythmias and myocardial infarction
gery. [127].
Since upper respiratory infection (URI) may alter Most medications used during anesthesia, including
pulmonary function for up to 5 weeks [118], major sur- sedatives such as diazepam and midazolam, hypnotics
gery requiring general endotracheal anesthesia should such as propofol, and analgesics such as fentanyl, me-
be postponed, especially if the patient suffers residual peridine and morphine, increase the risk of airway ob-
systems, such as fevers, chills, coughing and sputum struction and respiratory depression in patients with
production, until the patient is completely asymptom- OSA [128]. Death may occur suddenly and silently in
atic. patients with inadequate monitoring [129]. A combina-
While many studies confirm that patients who tion of anatomical abnormalities make airway manage-
smoke more than one to two packs of cigarettes daily ment, including mask ventilation and endotracheal in-
have a higher risk of perioperative respiratory compli- tubation, especially challenging in obese patients with
cations than non-smokers, cessation of smoking in the OSA [130]. Perioperative monitoring, including visual
immediate preoperative period may not improve pa- observation, must be especially vigilant to avoid peri-
tients’ outcome. In fact, patients’ risk of perioperative operative respiratory arrest in patients with OSA.
complications may actually increase if smoking is For patients with severe OSA, particularly those
stopped immediately prior to surgery. A full 8 weeks with additional coexisting medical conditions such as
may be required to successfully reduce perioperative cardiac or pulmonary disease, surgery performed on
pulmonary risk [119]. an outpatient basis is not appropriate. For these high-
If the physical examination of asthmatic patients re- risk patients, monitoring should continue in the inten-
veals expiratory wheezing, conventional wisdom dic- sive care unit until the patient no longer requires par-
tates that potentially reversible bronchospasm should enteral analgesics. If technically feasible, regional anes-
be optimally treated prior to surgery. Therapeutic thesia may be preferable in patients with severe OSA.
agents include inhaled or systemic, selective beta-ad- Postoperatively, patients with any history of OSA
renergic receptor type-2 agonists (albuterol) as a sole should not be discharged if they appear lethargic or
agent or in combination with anticholinergic (ipratro- somnolent [131].
pium) and locally active corticosteroid (beclomethaso- During the preoperative evaluation of the obese pa-
ne dipropronate) medications [120]. Continuing the tient, a presumptive diagnosis of OSA may be made if
asthmatic medications up to the time of surgery [121] the patient has a history of loud snoring, long pauses of
and postoperative use of incentive spirometry [122] has breathing during sleep, as reported by the spouse, or
been shown to reduce postoperative pulmonary com- daytime somnolence [132]. If OSA is suspected, pa-
plications. tients should be referred for a sleep study to evaluate
With regard to treated stable pulmonary disease, the severity of the condition.
there are no conclusive, prospective, randomized stud-
ies to indicate which anesthesia technique or medica-
2.2.7
tions would improve patient outcome.
Malignant Hyperthermia Susceptibility
Patients with susceptibility to malignant hyperthermia
2.2.6
(MH) can be successfully managed on an outpatient
Obstructive Sleep Apnea
basis after 4 h of postoperative monitoring [133]. Trig-
According to the National Commission on Sleep Disor- gering agents include volatile inhalation agents such as
ders Research, approximately 18 million Americans halothane, enflurane, desflurane, isoflurane and sevof-
suffer with obstructive sleep apnea (OSA). Unfortu- lurane. Even trace amounts of these agents lingering in
nately, the majority of patients with OSA remain undi- an anesthesia machine or breathing circuit may precip-
agnosed [123]. The incidence of sleep apnea increases itate an MH crisis. Succinylcholine and chlopromazine
among obese patients [124]. Since the target popula- are other commonly used medications, which are
tion for major liposuction and abdominoplasty in- known triggers of MH. However, many non-triggering
cludes patients with morbid obesity, concern about medications may be safely used for local anesthesia, se-
OSA becomes more germane. dation-analgesia, postoperative pain control, and even
OSA is a result of a combination of excessive pha- general anesthesia [134]. Nevertheless, anesthesia for
ryngeal adipose tissue and inadequate pharyngeal soft patients suspected of having MH susceptibility should
tissue support [125]. During episodes of sleep apnea, not be performed in an office-based setting. A stan-36 2 Anesthesia for Liposuction and Abdominoplasty
dardized protocol to manage MH (available from the [139] and the possible cytochrome inhibition of con-
Malignant Hyperthermia Association of the United comitantly administered medications [140]. The maxi-
States, MHAUS) and supplies of dantrolene and cold in- mum tolerable limits of local anesthetics have been re-
travenous fluids should be available for all patients. defined with the development of the tumescent anes-
Preferably, patients with MH susceptibility should thetic technique [141]. Lidocaine doses up to 35 mg/kg
be referred to an anesthesiologist for prior consulta- were found to be safe, if administered in conjunction
tion. Intravenous dantrolene [135] and iced intrave- with dilute epinephrine during liposuction [142]. With
nous fluids are still the preferred treatment. MHAUS the tumescent technique, peak plasma levels occur
may be contacted at 800 – 98MHAUS and the MH hotli- 6 – 24 h after administration [142, 143]. More recently,
ne is 800-MH-HYPER. doses up to 55 mg/kg have been found to be within the
therapeutic safety margin [144]. However, recent guide-
lines by the American Academy of Cosmetic Surgery
2.3 recommend a maximum dose of 45 – 50 mg/kg [29].
Anesthesia for Liposuction and Abdominoplasty Since lidocaine is predominantly eliminated by he-
patic metabolism, specifically, cytochrome oxidase
Anesthesia may be divided into four broad categories: P450 34A, drugs that inhibit this microsomal enzyme
local anesthesia, local anesthesia combined with seda- may increase the potential of lidocaine toxicity [140,
tion, regional anesthesia and general anesthesia. The 145]. Table 2.6 lists some of the more common medica-
ultimate decision to select the type of anesthesia de- tions, which inhibit the cytochrome oxidase system.
pends on the type and extent of the surgery planned, Propofol and Versed, commonly used medications for
the patient’s underlying health condition and the psy- sedation and hypnosis during liposuction, are also
chological disposition of the patient. For example, a known to be cytochrome P450 inhibitors. However,
limited liposuction of less than 500 ml of fat from a since the duration of action of these drugs is only
small area in a healthy patient, with limited anxiety, 1 – 4 h, the potential inhibition should not interfere
could certainly be performed using strictly local anes- with lidocaine at the peak serum level 6 – 12 h later. Lo-
thesia without sedation. As the scope of the surgery rezepam is a sedative which does not interfere with cy-
broadens, or the patient’s anxiety level increases, the lo- tochrome oxidase and is preferred by some authors
cal anesthesia may be supplemented with oral or par- [146].
enteral analgesic or anxiolytic medication.
Table 2.6. Medications inhibiting cytochrome oxidase P450
2.3.1 3A4 (Shiffman [140])
Local Anesthesia
Amiodarone Fluoxetine Nifedipine
A variety of local anesthetics are available for infiltra- Atenolol Itraconazole Paroxetine
Carbamazepine Isoniazide Pentoxifylline
tive anesthesia. The selection of the local anesthetic de-
Cimetidine Labetolol Pindolol
pends on the duration of anesthesia required and the Clarithromycin Ketoconazole Propofol
volume of anesthetic needed. Chloramphenicol Methadone Propranolol
The traditionally accepted, pharmacological pro- Cyclosporin Methyprednisolone Quinidine
files of common anesthetics used for infiltrative anes- Danazol Metoprolol Sertraline
Dexamethasone Miconazole Tetracyline
thesia for adults are summarized in Table 2.5. The max- Diltiazam Midazolam Terfenidine
imum doses may vary widely depending on the type of Erythromycin Nadolol Thyroxine
tissue injected [136], the rate of administration [137], Fluconazole Nefazodone Timolol
the age, underlying health, and body habitus of the pa- Flurazepam Nicardipine Triazolam
Verapamil
tient [138], the degree of competitive protein binding
Table 2.5. Clinical pharmacology of common local anesthetics for infiltrative anesthesia. (Adapted from Covino and Wildsmith
[61])
Agent Concen- Without epinephrine With epinephrine
tration ( %) Duration of action (min) Maximum Duration of action (min) Maximum
mg/kg total mg total ml dose mg/kg total mg/kg total ml dose
Lidocaine 1.0 30 – 60 4 300 30 120 7 500 50
Mepivacaine 1.0 45 – 90 4 300 30 120 7 500 50
Etidocaine 0.5 120 – 180 4 300 60 180 5.5 400 80
Bupivacaine 0.25 120 – 240 2.5 185 75 180 3 225 90
Ropivacaine 0.2 120 – 360 2.7 200 8 120 – 360 2.7 200 802.3 Anesthesia for Liposuction and Abdominoplasty 37 Certainly, significant toxicity has been associated [156] is uncomfortably close to the maximum serum with high doses of lidocaine as a result of tumescent an- levels reported by Ostad et al. [140] of 3.4 and 3.6 µg/ml esthesia during liposuction [146]. The systemic toxicity following tumescent lidocaine doses of 51.3 and of local anesthetic has been directly related to the se- 76.7 mg/kg respectively. Similar near toxic levels were rum concentration by many authors [139, 142 – 144, reported in individual patients receiving about 35 mg/ 146 – 148]. Early signs of toxicity, usually occurring at kg of lidocaine by Samdal et al. [157]. Pitman [158] re- serum levels of about 3 – 4 µg/ml for lidocaine, include ported that toxic manifestations occurred 8 h postoper- circumoral numbness and lightheadedness, and tinni- atively after a total dose of 48.8 mg/kg which resulted tus. As the serum concentration increases toward 8 µg/ from a 12-h plasma lidocaine level of 3.7 µg/kg. Ostad et ml, tachycardia, tachypnea, confusion, disorientation, al. [140] concludes that because of the poor correlation visual disturbance, muscular twitching and cardiac de- of lidocaine doses with the plasma lidocaine levels, an pression may occur. At still higher serum levels above extrapolation of the maximum safe dose of lidocaine 8 µg/ml, unconsciousness and seizures may ensue. for liposuction cannot be determined. Given the devas- Complete cardiorespiratory arrest may occur between tating consequences of lidocaine toxicity, physicians 10 and 20 µg/ml [139, 146, 147]. However, the toxicity of must exercise extreme caution while attempting to lidocaine may not always correlate exactly with the push the acceptable safe limits to ever-higher levels of plasma level of lidocaine presumably because of the tumescent anesthesia. Physicians must consider the variable extent of protein binding in each patient and important variables affecting susceptibility of individ- the presence of active metabolites [139] and other fac- ual patients to lidocaine toxicity before “boldly going tors already discussed including the age, ethnicity, where no surgeon has gone before”, especially since health, and body habitus of the patient, and additional plasma lidocaine levels typically peak after the patient medications. is at home. Ropivacaine, a long lasting local anesthetic, has less Patients who report previous allergies to anesthetics cardiovascular toxicity than bupivacaine and may be a may present a challenge to surgeons performing lipo- safer alternative to bupivacaine if a local anesthetic of suction. Although local anesthetics of the aminoester longer duration is required [149, 150]. The cardiovas- class such as procaine are associated with allergic reac- cular toxicity of bupivacaine and etidocaine is much tions, true allergic phenomena to local anesthetics of greater than that of lidocaine [149 – 151]. While bupiva- the aminoamide class, such as lidocaine, are extremely caine toxicity has been associated with sustained ven- rare [158, 159]. Allergic reactions may occur to the pre- tricular tachycardia and sudden profound cardiovascu- servative in the multidose vials. Tachycardia and gener- lar collapse [152, 153], the incidence of ventricular alized flushing may occur with rapid absorption of the dysarrhythmias has not been as widely acknowledged epinephrine contained in some standard local anes- with lidocaine or mepivacaine toxicity. In fact, ventric- thetic preparations. The development of vasovagal re- ular tachycardia of fibrillation was not observed despite actions after injections of any kind may cause hypoten- the use of supraconvulsant doses of intravenous doses sion, bradycardia, diaphoresis, pallor, nausea, and loss of lidocaine, etidocaine, or mepivacaine in the animal of consciousness. These adverse reactions may be mis- model [150]. interpreted by the patient and even the physician as al- Indeed, during administration of infiltrative lido- lergic reactions [159]. A careful history from the pa- caine anesthesia, rapid anesthetic injection into a high- tient describing the apparent reaction usually clarifies ly vascular area or accidental intravascular injection the cause. If there is still concern about the possibility leading to sudden toxic levels of anesthetics resulting in of true allergy to local anesthetic, then the patient sudden onset of seizures or even cardiac arrest or car- should be referred to an allergist for skin testing. diovascular collapse has been documented [154, 155]. In the event of a seizure following a toxic dose of lo- One particularly disconcerting case presented by cal anesthetic, proper airway management and main- Christie confirms the fatal consequence of a lidocaine taining oxygenation is critical. Seizure activity may be injection of 200 mg in a healthy patient [156]. Seizure aborted with intravenous diazepam (10 – 20 mg), mida- and death occurred following a relatively low dose of li- zolam (5 – 10 mg), or thiopental (100 – 200 mg). docaine and a serum level of only 0.4 mg/100 ml or Although the ventricular arrhythmias associated 4 µg/ml. A second patient suffered cardiac arrest with a with bupivacaine toxicity are notoriously intractable blood level of 0.58 mg/100 ml or 5 µg/ml [156]. Al- [152, 153], treatment is still possible using large doses though continued postmortem metabolism may artifi- of atropine, epinephrine and bretylium [161, 162]. cially reduce serum lidocaine levels, the reported se- Some studies indicate that lidocaine should not be used rum levels associated with mortality in these patients [163]. Pain associated with local anesthetic administra- were well below the 8 – 20 µg/ml considered necessary tion is due to the pH of the solution and may be reduced to cause seizures, myocardial depression, and cardiore- by the addition of 1 mEq of sodium bicarbonate to spiratory arrest. The 4 µg/ml level reported by Christie 10 ml of anesthetic [164].
38 2 Anesthesia for Liposuction and Abdominoplasty
EMLA (eutectic mixture of local anesthetics), a com- of general anesthesia [166]. During general anesthesia
bination of lidocaine and prilocaine, may provide ef- the patient most likely loses the LPPRs.
fective topical anesthesia over smaller areas such as the In actual practice, the delineation between the levels
face. However, an occlusive dressing must be applied, of sedation becomes challenging at best. The loss of
and at least 60 min is required for adequate anesthesia consciousness occurs as a continuum. With each incre-
[165]. Except for small, localized surgical procedures, mental change in the level of consciousness, the likeli-
topical anesthetics do not have a wide application for li- hood of loss of LPPRs increases. Since the definition of
posuction or abdominoplasty. conscious sedation is vague, current ASA guidelines
consider the term sedation-analgesia a more relevant
term than conscious sedation [25]. The term sedative-
2.3.2
analgesic medication (SAM) has been adopted by some
Sedative-Analgesic Medication (SAM)
facilities. Monitored anesthesia care (MAC) has been
Most liposuctions are performed with a combination of generally defined as the medical management of pa-
local tumescent anesthesia and supplemental sedative- tients receiving local anesthesia during surgery with or
analgesic medications (SAM) administered orally without the use of supplemental medications. MAC
(p.o.), intramuscularly (i.m.), or intravenously (i.v.). usually refers to services provided by the anesthesiolo-
Abdominoplasties performed under local or regional gist or the Certified Registered Nurse Anesthetist
anesthesia generally require SAM. The goals of admin- (CRNA). The term “local standby” is no longer used
istering supplemental medications are to reduce anxi- because it mischaracterizes the purpose and activity of
ety (anxiolysis), the level of consciousness (sedation), the anesthesiologist or CRNA.
unanticipated pain (analgesia), and, in some cases, to Surgical procedures performed using a combination
eliminate recall of the surgery (amnesia). of local anesthetic and SAM usually have a shorter re-
Sedation may be defined as the reduction of the level covery time than similar procedures performed under
of consciousness usually resulting from pharmacologi- regional or general anesthesia [167]. Using local anes-
cal intervention. The level of sedation may be further thesia alone, without the benefit of supplemental medi-
divided into three broad categories, conscious seda- cation is associated with a greater risk of cardiovascu-
tion, deep sedation, and general anesthesia. The term lar and hemodynamic perturbations such as tachycar-
conscious sedation has evolved to distinguish a lighter dia, arrhythmias, and hypertension particularly in pa-
state of anesthesia with a higher level of mental func- tients with preexisting cardiac disease or hypertension
tioning whereby the life-preserving protective reflexes [168]. Patients usually prefer sedation while undergo-
are independently and continuously maintained. Fur- ing surgery with local anesthetics [169]. While the ad-
thermore, the patient is able to respond appropriately dition of sedatives and analgesics during surgery using
to physical and verbal stimulation [166]. local anesthesia seems to have some advantages, use of
Life preserving protective reflexes (LPPRs) may be SAM during local anesthesia is certainly not free of
defined as the involuntary physical and physiological risk. A study by the Federated Ambulatory Surgical As-
responses that maintain the patient’s life which, if inter- sociation concluded that local anesthesia, with supple-
rupted, result in inevitable and catastrophic physiolog- mental medications, was associated with more than
ical consequences. The most obvious examples of twice the number of complications than with local an-
LPPRs are the ability to maintain an open airway, swal- esthesia alone. Furthermore, local anesthesia with
lowing, coughing, gagging, and spontaneous breath- SAM was associated with greater risks than general an-
ing. Some involuntary physical movements such as esthesia [60]. Significant respiratory depression as de-
head turning or attempts to assume an erect posture termined by the development of hypoxemia, hypercar-
may be considered LPPRs if these reflex actions occur bia, and respiratory acidosis often occurs in patients af-
in an attempt to improve airway patency such as expel- ter receiving minimal doses of medications. This respi-
ling oropharyngeal contents. The myriad of homeo- ratory depression persists even in the recovery period
static mechanisms to maintain blood pressure, heart [170, 171].
function and body temperature may even be consid- One explanation for the frequency of these compli-
ered LPPRs. cations is the wide variability of patients’ responses to
As the level of consciousness is further depressed to these medications. Up to 20-fold differences in the dose
the point that the patient is not able to respond pur- requirements for some medications such as diazepam,
posefully to verbal commands or physical stimulation, and up to 5-fold variations for some narcotics such as
the patient enters into a state referred to as deep seda- fentanyl, have been documented in some patients [172,
tion. In this state, there is a significant probability of 173]. Even small doses of fentanyl as low as 2 µg/kg,
loss of LPPRs. Ultimately, as total loss of consciousness considered by many physicians as subclinical, produce
occurs and the patient no longer responds to verbal respiratory depression for more than 1 h in some pa-
command or painful stimuli, the patient enters a state tients [174]. Combinations of even small doses of seda-2.3 Anesthesia for Liposuction and Abdominoplasty 39
tives, such as midazolam, and narcotics, such as fenta- during local anesthesia to decrease pain associated
nyl, may act synergistically (effects greater than an ad- with local anesthetic injection or unanticipated break-
ditive effect) in producing adverse side effects such as through pain. Fentanyl has the advantage of rapid onset
respiratory depression and hemodynamic instability and duration of action of less than 60 min. However,
[175]. The clearance of many medications may vary de- because of synergistic action with sedative agents, even
pending on the amount and duration of administra- doses of 25 – 50 µg can result in respiratory depression
tion, a phenomenon known as context-sensitive half- [183]. Other medications with sedative and hypnotic
life. The net result is increased sensitivity and duration effects such as a barbiturate, ketamine, or propofol are
of action to medication for longer surgical cases [176]. often added. Adjunctive analgesics such as ketorolac
Because of these variations and interactions, predicting may be administered for addition of analgesic activity.
any given patient’s dose response is a daunting task. Pa- As long as the patient is carefully monitored, several
tients appearing awake and responsive may, in an in- medications may be titrated together to achieve the ef-
stant, slip into unintended levels of deep sedation with fects required for the patient characteristics and the
greater potential of loss of LPPRs. Careful titration of complexity of the surgery. Fixed combinations of medi-
these medications to the desired effect combined with cations are not advised [25].
vigilant monitoring are the critical elements in avoid- More potent narcotic analgesics with rapid onset of
ing complications associated with the use of SAM. action and even shorter duration of action than fenta-
Supplemental medication may be administered via nyl include sufenanil, alfenanil, and remifenanil and
multiple routes including oral, nasal, transmucosal, may be administered using intermittent boluses or con-
transcutaneous, intravenous, intramuscular and rectal. tinuous infusion in combination with other sedative or
While intermittent bolus has been the traditional hypnotic agents. However, extreme caution and scru-
method to administer medication, continuous infusion pulous monitoring is required when these potent nar-
and patient controlled delivery result in comparable cotics are used because of the risk of respiratory arrest
safety and patient satisfaction [177, 178]. [184, 185]. Use of these medications should be restrict-
Benzodiazepines such as diazepam, midazolam and ed to the anesthesiologist or the CRNA. A major disad-
lorezepam remain popular for sedation and anxiolysis. vantage of narcotic medication is the perioperative
Patients and physicians especially appreciate the potent nausea and vomiting [186].
amnestic effects of this class of medications, especially Many surgeons feel comfortable administering SAM
midazolam. The disadvantages of diazepam include the to patients. Others prefer to use the services of an anes-
higher incidence of pain on intravenous administra- thesiologist or CNRA. Prudence dictates that for pro-
tion, the possibility of phlebitis [179], and the pro- longed or complicated surgeries or for patients with
longed half-life of up to 20 – 50 h. Moreover, diazepam significant risk factors, the participation of the anes-
has active metabolites which may prolong the effects of thesiologist or CRNA during MAC anesthesia is prefer-
the medication even into the postoperative recovery able. Regardless of who administers the anesthetic
time [180]. Midazolam, however, is more rapidly me- medications, the monitoring must have the same level
tabolized, allowing for a quicker and more complete re- of vigilance.
covery for outpatient surgery [180]. Because the seda- Propofol, a member of the alkylphenol family, has
tive, anxiolytic and amnestic effects of midazolam are demonstrated its versatility as a supplemental sedative-
more profound than other benzodiazepines and the re- hypnotic agent for local anesthesia and of regional an-
covery is more rapid, patient acceptance is usually esthesia. Propofol may be used alone or in combination
higher [181]. Since lorezepam is less affected by medi- with a variety of other medications. Rapid metabolism
cations altering cytochrome P459 metabolism [182], it and clearance results in faster and more complete re-
has been recommended as the sedative of choice of li- covery with less postoperative hangover than other
posuctions which require a large dose lidocaine tumes- sedative-hypnotic medications such as midazolam and
cent anesthesia [146]. The disadvantage of lorezepam is methohexital [187, 188]. The documented antiemetic
the slower onset of action and the 11 – 22 h elimination properties of propofol yield added benefits of this med-
half-life, making titration cumbersome and postopera- ication [189]. The disadvantages of propofol include
tive recovery prolonged [180]. pain on intravenous injection and the lack of amnestic
Generally, physicians who use SAM titrate a combi- effect [190]. However, the addition of 3 ml of 2 % lido-
nation of medications from different classes to tailor caine to 20 ml of propofol virtually eliminates the pain
the medications to the desired level of sedation and an- on injection with no added risk. If an amnestic re-
algesia for each patient. Use of pre-packaged combina- sponse is desired, a small dose of a benzodiazepine,
tions of medications defeats the purpose of the selec- such as midazolam (5 mg i.v.), given in combination
tive control of each medication. Typically, sedatives with propofol, provides the adequate amnesia. Rapid
such as the benzodiazepines are combined with narcot- administration of propofol may be associated with sig-
ic analgesics such as fentanyl, meperidine, or morphine nificant hypotension, decreased cardiac output [191],You can also read
