Best anaesthetic drug strategy for morbidly obese patients. Curr Opin Anaesthesiol. 2016;29:119-128. [PMID: 26658181 DOI: 10.1097/aco.0000000000000286]

High and low body mass index increases the risk of short-term postoperative complications following total shoulder arthroplasty

Background

Several studies have investigated the impact of body mass index (BMI) on total shoulder arthroplasty (TSA) outcomes and reported contrasting results. Therefore, this study aims to better understand the impact of BMI on 30-day post-TSA outcomes by performing a comprehensive risk stratification based on BMI using a large national database.

Methods

All patients undergoing TSA, both anatomic and reverse, between 2015 and 2019 were queried from the American College of Surgeons National Surgical Quality Improvement Program database. The study population was stratified into 6 cohorts: BMI < 18.5 kg/m2 (underweight), BMI of 18.5-24.9 kg/m2 (reference cohort), BMI of 25.0-29.9 kg/m2 (overweight), BMI of 30.0-39.9 kg/m2 (obese), BMI of 40.0-49.9 kg/m2 (morbidly obese), and BMI ≥ 50.0 kg/m2 (super-morbidly obese). Postoperative complications within 30 days of surgery were collected. Multivariate logistic regression was conducted to investigate the association between BMI values and postoperative complications. Additionally, to facilitate a direct comparison with existing literature, and further validate our study methodology, a subgroup analysis with multivariate logistic regression was made comparing 2 groups: BMIs > 30 kg/m2 and BMIs < 30 kg/m2. Odds ratios (ORs) were reported with a 95% confidence interval. The level of statistical significance was set at P < .05. The analyses were conducted using SPSS 26.0.

Results

A total of 22,542 patients undergoing TSA between 2015 and 2019 were reported in the database. Of these, 410 patients did not have reported BMIs, leaving 22,132 patients for the analysis (1.8% attrition bias). The underweight cohort had a greater likelihood of mortality (OR, 6.184; P = .008) and nonhome discharge (OR, 1.824; P = .008). The morbidly obese cohort had a greater likelihood of developing wound infections (OR, 5.254; P < .002). The super-morbidly obese cohort presented a greater likelihood of developing wound infections (OR, 13.431; P = .002) and nonhome discharge (OR, 1.525; P = .035).

Conclusion

Patients with BMI less than 18 and more than 40 were associated with an increased incidence of 30-day postoperative TSA complications such as wound infection, nonhome discharge, and mortality. Based on these findings, preoperative risk stratification based on BMI remains an important part of elective surgery.

Postoperative pain trajectory and opioid requirements after laparoscopic bariatric surgery: a single-centre historical cohort study

PURPOSE

Concerns around delayed emergence and opioid-induced ventilatory impairment in bariatric surgery can lead to intraoperative reliance on short-acting opioids and avoidance of long-acting analgesics with potential sedative effects. Nevertheless, an overly-conservative intraoperative analgesic strategy may result in significant pain at emergence and higher opioid requirements in later phases of care. We sought to establish the pattern of intraoperative analgesic use in bariatric surgical patients as well as their postoperative pain trajectory and opioid requirements.

METHODS

We undertook a single-centre historical cohort study. We explored associations between intraoperative analgesic interventions and pain scores and opioid requirements in postanesthesia care units (PACUs), and associations between the quality of analgesia at emergence and subsequent pain and patient-centred recovery outcomes.

RESULTS

We extracted perioperative data for 939 patients who underwent bariatric metabolic surgery between January 2018 and October 2019. Only 39% of patients received long-acting opioids intraoperatively and there was minimal use of nonopioid analgesic adjuncts. Nearly 80% of patients reported moderate-to-severe pain on PACU arrival; 97% of patients received intravenous opioids for rescue analgesia (mean dose, 31 mg oral morphine equivalents). Lower pain scores at PACU admission and discharge were associated with subsequent lower inpatient pain scores, lower opioid requirements, shorter time to ambulation, and shorter length of hospital stay.

CONCLUSION

In bariatric surgical patients, effective intraoperative analgesic strategies that improve early pain control may have an impact on recovery and pain experience. Judicious use of intraoperative opioids coupled with opioid-sparing multimodal analgesic techniques should be considered and balanced against concerns regarding opioid-related adverse effects in this patient population.

Nociception Effect on Frontal Electroencephalogram Waveform and Phase-Amplitude Coupling in Laparoscopic Surgery

BACKGROUND

Electroencephalographic pattern changes during anesthesia reflect the nociception-analgesia balance. Alpha dropout, delta arousal, and beta arousal with noxious stimulation have been described during anesthesia; however, data on the reaction of other electroencephalogram signatures toward nociception are scarce. Analyzing the effects of nociception on different electroencephalogram signatures may help us find new nociception markers in anesthesia and understand the neurophysiology of pain in the brain. This study aimed to analyze the electroencephalographic frequency pattern and phase-amplitude coupling change during laparoscopic surgeries.

METHODS

This study evaluated 34 patients who underwent laparoscopic surgery. The electroencephalogram frequency band power and phase-amplitude coupling of different frequencies were analyzed across 3 stages of laparoscopy: incision, insufflation, and opioid stages. Repeated-measures analysis of variance with a mixed model and the Bonferroni method for multiple comparisons were used to analyze the changes in the electroencephalogram signatures between the preincision and postincision/postinsufflation/postopioid phases.

RESULTS

During noxious stimulation, the frequency spectrum showed obvious decreases in the alpha power percentage after the incision (mean ± standard error of the mean [SEM], 26.27 ± 0.44 and 24.37 ± 0.66; P < .001) and insufflation stages (26.27 ± 0.44 and 24.40 ± 0.68; P = .002), which recovered after opioid administration. Further phase-amplitude analyses showed that the modulation index (MI) of the delta-alpha coupling decreased after the incision stage (1.83 ± 0.22 and 0.98 ± 0.14 [MI × 10 3 ]; P < .001), continued to be suppressed during the insufflation stage (1.83 ± 0.22 and 1.17 ± 0.15 [MI × 10 3 ]; P = .044), and recovered after opioid administration.

CONCLUSIONS

Alpha dropout during noxious stimulation is observed in laparoscopic surgeries under sevoflurane. In addition, the modulation index of delta-alpha coupling decreases during noxious stimulation and recovers after the administration of rescue opioids. Phase-amplitude coupling of the electroencephalogram may be a new approach for evaluating the nociception-analgesia balance during anesthesia.

Effect of magnesium sulfate on oxygenation and lung mechanics in morbidly obese patients undergoing bariatric surgery: a prospective double-blind randomized clinical trial

BACKGROUND

Respiratory mechanics are often significantly altered in morbidly obese patients and magnesium sulfate (MgSO4) is a promising agent for managing several respiratory disorders. This study aimed to examine the effects of MgSO4 infusions on arterial oxygenation and lung mechanics in patients with morbid obesity undergoing laparoscopic bariatric surgery.

METHODS

Forty patients with morbid obesity aged 21-60 years scheduled for laparoscopic bariatric surgery under general anesthesia were randomly allocated to either the control (normal saline infusion) or MgSO4 group (30 mg/kg lean body weight [LBW] of 10% MgSO4 in 100 ml normal saline intravenously over 30 min as a loading dose, followed by 10 mg/kg LBW/h for 90 min). The primary outcome was intraoperative arterial oxygenation (ΔPaO2/FiO2). Secondary outcomes included intraoperative static and dynamic compliance, dead space, and hemodynamic parameters.

RESULTS

At 90 min intraoperatively, the Δ PaO2/FiO2 ratio and the Δ dynamic lung compliance were statistically significantly higher in the MgSO4 group (mean ± SE: 16.1 ± 1.0, 95% CI [14.1, 18.1] and 8.4 ± 0.5 ml/cmH2O, 95% CI [7.4, 9.4]), respectively), and the Δ dead space (%) was statistically significantly lower in the MgSO4 group (mean ± SE: -8.0 ± 0.3%, 95% CI [-8.6, -7.4]) (P < 0.001). No significant differences in static compliance were observed.

CONCLUSIONS

Although MgSO4 significantly preserved arterial oxygenation and maintained dynamic lung compliance and dead space in patients with morbid obesity, the clinical relevance is minimal. This study failed to adequately reflect the clinical importance of these results.

[Anesthesia in obesity surgery : Recommendations from the practice for the practice]

BACKGROUND

Due to unsuccessful conservative treatment concepts and the steady increase in the prevalence of obesity, obesity surgery has gained importance worldwide. In Germany alone, around 20,000 surgical operations for obesity are performed each year. In addition to patient history and physical examination a close interdisciplinary cooperation taking into account the currently applicable standards and guidelines of the professional societies are prerequisites for best patient care and to evaluate and mitigate patient risks.

AIM

The aim of this work was to compile and consent experiences of experts in the implementation of applicable standards and guidelines for anesthesia in obesity surgery for daily clinical practice.

METHOD

Anesthesiologists from five bariatric centers, comprising about 10% of the obesity surgery caseload of Germany per year, have collated their clinical experiences to agree on a consensus for procedures. The procedures for preoperative patient evaluation, drug premedication and PONV prophylaxis, induction of anesthesia and drug dosage recommendations for anesthetics were consented based on the authors' practice.

RESULTS AND CONCLUSION

The procedures described herein were developed as part of a joint work process. The authors describe a practically applicable approach to the anesthesiological care of obesity surgery patients and recommend using a pragmatic formula for dosing the medication calculated on the basis of total body weight (TBW).

Enhanced recovery after bariatric surgery: an Italian consensus statement

Background

Enhanced recovery after bariatric surgery (ERABS) is an approach developed to improve outcomes in obese surgical patients. Unfortunately, it is not evenly implemented in Italy. The Italian Society for the Surgery of Obesity and Metabolic Diseases and the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care joined in drafting an official statement on ERABS.

Methods

To assess the effectiveness and safety of ERABS and to develop evidence-based recommendations with regard to pre-, intra-, and post-operative care for obese patients undergoing ERABS, a 13-member expert task force of surgeons and anesthesiologists from Italian certified IFSO center of excellence in bariatric surgery was established and a review of English-language papers conducted. Oxford 2011 Levels of Evidence and U.S. Preventive Services Task Force Grade Definitions were used to grade the level of evidence and the strength of recommendations, respectively. The supporting evidence and recommendations were reviewed and discussed by the entire group at meetings to achieve a final consensus.

Results

Compared to the conventional approach, ERABS reduces the length of hospital stay and does not heighten the risk of major post-operative complications, re-operations, and hospital re-admissions, nor does it increase the overall surgical costs. A total of 25 recommendations were proposed, covering pre-operative evaluation and care (7 items), intra-operative management (1 item, 11 sub-items), and post-operative care and discharge (6 items).

Conclusions

ERABS is an effective and safe approach. The recommendations allow the proper management of obese patients undergoing ERABS for a better outcome.

Practical Estimation of Ideal Body Weight and Normalized Lean Weight

Simple formulas for estimating ideal body weight (IBW) and normalized lean weight (NLW) are proposed here. The equations are as follows:[Formula: see text][Formula: see text]where W is equal to total patient weight in kilograms and BMI is the body mass index in units of kg/m². The calculated values are equivalent for practical purposes to previously published formulas.

Evaluation of super-obesity and super-super-obesity as risk factors for difficult intubation in patients undergoing bariatric surgery

BACKGROUND

Super-obesity is a serious disorder which requires bariatric surgery. The association of super-obesity and difficult intubation was not adequately established.

OBJECTIVES

To determine if super-obesity and super-super-obesity are associated with difficult intubation or not.

SETTING

University Hospital.

METHODS

A cohort of obese patients scheduled for bariatric surgery was prospectively recruited. Super-obesity and super-super-obesity were defined as body mass index ≥50 kg/m² and 60 kg/m², respectively. Intubation difficulty was assessed by 2 methods: (1) intubation difficulty scale; (2) number of intubation attempts. Risk factors for difficult intubation were recorded. Univariate and multivariate analysis for risk factors for difficult intubation and difficult mask ventilation were performed.

RESULTS

A total of 658 patients were enrolled in the study including 205 (31%) super-obese and 52 (8%) super-super-obese patients. Ninety-nine (15%) patients required more than 1 intubation attempt, while 215 (33%) patients had intubation difficulty scale ≥5. Ninety-four (14.4%) patients had mask ventilation of moderate difficulty, while only 2 (.3%) patients needed 2-person ventilation. The independent risk factors for difficult intubation using the two stated definitions were STOP-Bang and Mallampati score values. The independent risk factors for mask ventilation of moderate difficulty were STOP-Bang score, Mallampati score, and limited neck extension.

CONCLUSION

Within obese patients, neither super-obesity nor super-super-obesity was associated with difficult intubation or difficult mask ventilation. High STOP-Bang and Mallampati score are the independent factors for difficult intubation.

High-Frequency Heart Rate Variability Index: A Prospective, Observational Trial Assessing Utility as a Marker for the Balance Between Analgesia and Nociception Under General Anesthesia

BACKGROUND

Maintaining a balance between nociception and analgesia perioperatively reduces morbidity and improves outcomes. Current intraoperative analgesic strategies are based on subjective and nonspecific parameters. The high-frequency heart rate (HR) variability index is purported to assess the balance between nociception and analgesia in patients under general anesthesia. This prospective observational study investigated whether intraoperative changes in the high-frequency HR variability index correlate with clinically relevant nociceptive stimulation and the addition of analgesics.

METHODS

Instantaneous and mean high-frequency HR variability indexes were measured continuously in 79 adult subjects undergoing general anesthesia for laparoscopic cholecystectomy. The indexes were compared just before and 2 minutes after direct laryngoscopy, orogastric tube placement, first skin incision, and abdominal insufflation and just before and 6 minutes after the administration of IV hydromorphone.

RESULTS

Data from 65 subjects were included in the final analysis. The instantaneous index decreased after skin incision ([SEM], 58.7 [2.0] vs 47.5 [2.0]; P < .001) and abdominal insufflation (54.0 [2.0] vs 46.3 [2.0]; P = .002). There was no change in the instantaneous index after laryngoscopy (47.2 [2.2] vs 40.3 [2.3]; P = .026) and orogastric tube placement (49.8 [2.3] vs 45.4 [2.0]; P = .109). The instantaneous index increased after hydromorphone administration (58.2 [1.9] vs 64.8 [1.8]; P = .003).

CONCLUSIONS

In adult subjects under general anesthesia for laparoscopic cholecystectomy, changes in the high-frequency HR variability index reflect alterations in the balance between nociception and analgesia. This index might be used intraoperatively to titrate analgesia for individual patients. Further testing is necessary to determine whether the intraoperative use of the index affects patient outcomes.

Choice of Perioperative Anesthetic Medications in Patients Undergoing Bariatric Surgery

The prevalence of obesity is increasing globally. Rational perioperative anesthetic drug selection and administration require knowledge of how obesity interacts with those drugs. In this review, we summarize different aspects of the anesthetic agents, including pharmacokinetics (PK), pharmacodynamics (PD) and clinical application of the most commonly used medications with particular focus on the enhanced recovery of the obese patient.

Awareness during emergence from anesthesia: Features and future research directions

The anesthesia awareness with recall (AAWR) phenomenon represents a complication of general anesthesia consisting of memorization of intraoperative events reported by the patient immediately after the end of surgery or at a variable distance from it. Approximately 20% of AAWR cases occur during emergence from anesthesia. Clinically, these unexpected experiences are often associated with distress especially due to a sense of paralysis. Indeed, although AAWR at the emergence has multiple causes, in the majority of cases the complication develops when the anesthesia plan is too early lightened at the end of anesthesia and there is a lack of use, or misuse, of neuromuscular monitoring with improper management of the neuromuscular block. Because the distress caused by the sense of paralysis represents an important predictor for the development of severe psychological complications, the knowledge of the phenomenon, and the possible strategies for its prophylaxis are aspects of considerable importance. Nevertheless, a limited percentage of episodes of AAWR cannot be prevented. This paradox holds also during the emergence phase of anesthesia which represents a very complex neurophysiological process with many aspects yet to be clarified.

Propofol Sedation for Intragastric Balloon Removal: Looking for the Optimal Body Weight Descriptor

AIM

Sedation is considered as a prerequisite for the safe and effective conclusion of Bioenterics Intragastric Balloon (BIB) removal (our aim was to ascertain the most appropriate body size scalars for propofol dosing and assess the efficacy and safety of a sedative approach involving the infusion of propofol for BIB removal.

METHOD

Retrospective analysis of prospectively collected data of 414 adults scheduled to undergo BIB removal. Our primary end-point was to delineate the relationship between propofol dosing and body size descriptors namely body mass index, total body weight, ideal body weight, lean body weight (LBW) and normalized LBW. Sedative efficacy of this practice, anesthesia or procedural-related adverse events and patients' satisfaction level served as secondary outcome parameters.

RESULTS

Propofol dose (mg/kg/min) was positively related to all body weight descriptors in an important manner (p < 0.001). Among them, LBW was singled out as the body size descriptor to best capture the appropriate needs of propofol (R2 = 0.432; p = 0.000). Hypoxemia, hemodynamic compromise, gastroesophageal reflux or moderate movement occurred rarely; all of them were readily reversed. The majority of participants had no recollection of the noxious phase of the procedure or declared at least adequately satisfied from the experience (84% and 95%, respectively).

CONCLUSION

LBW could serve as relatively more accurate dosing scalar compared to actual or ideal body weight descriptors, in obese individuals undergoing BIB removal under propofol sedation. The conscious/deep sedation based on propofol infusion emerges as a feasible and efficacious sedative approach for this procedure.

[Drugs for intravenous induction of anesthesia: propofol]

In a series of articles dealing with hypnotics for induction of anesthesia, this article describes the development and current value of propofol. Its significance far exceeds that of a pure induction hypnotic (sedation in diagnostic and therapeutic procedures and on the intensive care unit). Propofol is also used for sedation in diagnostic and therapeutic procedures and on the intensive care unit. In the field of induction of anesthesia, the alternatives are barely used. Some contraindications are still controversial whereas others are no longer sufficiently anchored in the users' awareness (widespread off-label use). Adverse effects, such as injection pain, infection risk and propofol-related infusion syndrome (PRIS) could be significantly reduced by pharmacovigilance. With appropriate caution nearly the whole spectrum of anesthesiology patients can be treated using propofol. The hemodynamic side effects and the rare but potentially fatal PRIS are limitations. Further developments address the water solubility and the solubilizing agents of propofol.

Anaesthetists' drug dosing practices in class III obese surgical patients: A bi-national survey

Class III obese (body mass index ≥ 40 kg/m2) patients, now regularly encountered clinically, have increased perioperative risks, including potentially from suboptimal drug dosing. However, current dosing guidelines are based on low-level evidence and may not be widely accepted. This study aimed to investigate anaesthetists’ dosing practices for class III obese surgical patients, explore if they had experienced an increased incidence of adverse events potentially related to drug dosing with these patients and assess which resources they consulted for dosing advice in this population. An electronic survey was emailed to 1000 randomly selected members of the Australian and New Zealand College of Anaesthetists. Data were summarised and the Pearson’s χ2 test was used to compare respondents’ genders, geographic locations and seniority designations with the greater Australian and New Zealand College of Anaesthetists’ membership. There were 230 completed responses (response rate 23%). A large proportion (46%–76%) of respondents indicated they dose class III obese patients in keeping with current recommendations; however, substantial heterogeneity in dosing practices was found. Lean body weight was the most frequently used regimen for dosing propofol, non-depolarising muscle relaxants, sugammadex and opioids, whereas total body weight was most frequently used for suxamethonium. Nearly 70% of respondents reported using at least one resource to assist their dosing practices in obesity. Importantly, increased incidences of adverse events in class III obese patients related to drug dosing were commonly experienced by respondents. Until higher-level evidence is available for dosing class III obese patients, anaesthetists should consider current recommendations and exercise increased attention to dosing. Further clinician education may assist in optimising dosing in this patient group.

Evaluation of the effects of dexmedetomidine infusion on oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease

Background

Dexmedetomidine infusion improves oxygenation and lung mechanics in patients with chronic obstructive lung disease; however, its effect in patients with restrictive lung disease has not been thoroughly investigated yet. The aim of this work was to evaluate the effects of dexmedetomidine infusion on oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease.

Methods

Forty-two morbidly obese patients scheduled for bariatric surgery were included in the study. Patients were randomized to receive either dexmedetomidine infusion at a bolus dose of 1mcg/Kg followed by infusion at 1 mcg/Kg/hour for 90 min (Dexmedetomidine group), or normal saline infusion (Control group). Both groups were compared with regard to: oxygenation {P/F ratio: PaO₂/fraction of inspired oxygen (FiO₂)}, lung compliance, dead space, plateau pressure, blood pressure, and heart rate.

Results

Dexmedetomidine group showed significant improvement of the PaO₂/FiO₂ ratio, and higher lung compliance compared to control group by the end of drug infusion. Dexmedetomidine group demonstrated decreased dead space, plateau pressure, blood pressure, and heart rate compared to control group by the end of drug infusion.

Conclusion

A 90-min dexmedetomidine infusion resulted in moderate improvement in oxygenation and lung mechanics in morbidly obese patients with restrictive lung disease.

Trial registration

clinicaltrials.gov: NCT02843698 on 20 July 2016.

Reliability of body-weight scalars on the assessment of propofol induction dose in obese patients

BACKGROUND

Obese patients require specific perioperative care when compared with non-obese patients. The present study aimed to analyse the ability of size descriptors to estimate propofol induction dose in class II and III obese patients.

METHODS

A cross-sectional study on adult patients with body mass index (BMI) equal to or greater than 35 kg/m² and on adult patients with BMI lower than 35 kg/m² was carried out. General anaesthesia was induced with remifentanil, propofol and rocuronium. Propofol infusion was started at 2000 mg/h until loss of consciousness. Bioelectrical impedance analysis and Brice modified interview was completed during pre- and post-operative evaluation, respectively. Measurements of propofol plasma concentration were performed using gas chromatography/ion trap-mass spectrometry.

RESULTS

Forty patients were enrolled in the study. The median values of fat free mass (FFM) in BMI < 35 kg/m² and BMI ≥ 35 kg/m² groups were 70% and 55% of total body weight, respectively. Our results did not demonstrate a strong correlation level between the studied size descriptors and propofol induction dose in both groups. Nevertheless, when propofol doses were normalized by FFM, an apparent convergence of the empirical cumulative distribution functions was observed.

CONCLUSION

None of the size descriptors was seen to be an effective predictor of the propofol induction dose in class II and III obese patients when a fixed infusion rate was used. Due to the observed variability between patients, guiding propofol induction dose against a clinical endpoint of unconsciousness appears more appropriate in order to avoid side effects related both with under or overdosing of propofol.

Factors affecting the early post-operative prognosis in morbidly obese surgical patients after laparoscopic sleeve gastrectomy - a retrospective cohort study

Background

The number of morbidly obese patients who have undergone bariatric surgery has been gradually increasing in Japan. These obese patients are often complicated with metabolic, cardiac, respiratory, and other diseases. The aim of this study was to analyze the perioperative clinical course in a retrospective cohort with respect to the utility of anesthesia management in order to prevent longer hospital stays after surgery.

Findings

Sixty-seven morbidly obese patients who had undergone sleeve gastrectomy were divided into two groups, based upon the duration of postoperative hospital stay; group S was comprised of the patients who were discharged within 5 days after surgery (n = 57) and group L was comprised of those who were discharged after 6 days or more (n = 10). The mean duration of the hospital stay was 4.8 ± 0.4 days and 7.8 ± 1.4 days in groups S and L, respectively. Multivariate logistic regression analysis showed that prolonged anesthesia was a predictor of a longer postoperative hospital stay (p < 0.05). While the difference in BMI was not significantly different, the percentage of patients with BMI ≥ 50 was 12 and 30% in groups S and L, respectively.

Conclusions

Longer duration of anesthesia affected the duration of postoperative hospital stay in morbidly obese patients undergoing sleeve gastrectomy. In addition, patients with BMI ≥ 50 might be at risk of longer hospitalization after surgery.

The obese patient undergoing nonbariatric surgery

PURPOSE OF REVIEW

This article provides the reader with recent findings on the pathophysiology of comorbidities in the obese, as well as evidence-based treatment options to deal with perioperative respiratory challenges.

RECENT FINDINGS

Our understanding of obesity-associated asthma, obstructive sleep apnea, and obesity hypoventilation syndrome is still expanding. Routine screening for obstructive sleep apnea using the STOP-Bang score might identify high-risk patients that benefit from perioperative continuous positive airway pressure and close postoperative monitoring. Measures to most effectively support respiratory function during induction of and emergence from anesthesia include optimal patient positioning and use of noninvasive positive pressure ventilation. Appropriate mechanical ventilation settings are under investigation, so that only the use of protective low tidal volumes could be currently recommended. A multimodal approach consisting of adjuvants, as well as regional anesthesia/analgesia techniques reduces the need for systemic opioids and related respiratory complications.

SUMMARY

Anesthesia of obese patients for nonbariatric surgical procedures requires knowledge of typical comorbidities and their respective treatment options. Apart from cardiovascular diseases associated with the metabolic syndrome, awareness of any pulmonary dysfunction is of paramount. A multimodal analgesia approach may be useful to reduce postoperative pulmonary complications.

Perioperative Care of the Obese Cardiac Surgical Patient

Morbid obesity is associated with impairment of cardiovascular, pulmonary, gastrointestinal, and renal physiology with significant perioperative consequences and has been linked with higher morbidity and mortality after cardiac surgery. Cardiac surgery patients have a higher incidence of difficult airway and difficult laryngoscopy than general surgery patients do, and obesity is associated with difficult mask ventilation and direct laryngoscopy. Positioning injuries occur more frequently because obese patients are at greater risk of pressure injury, such as rhabdomyolysis and compartment syndrome. Despite the association between obesity and several chronic disease states, the effects of obesity on perioperative outcomes are conflicting. Studies examining outcomes of overweight and obese patients in cardiac surgery have reported varying results. An "obesity paradox" has been described, in which the mortality for overweight and obese patients is lower compared with patients of normal weight. This review describes the physiologic abnormalities and clinical implications of obesity in cardiac surgery and summarizes recommendations for anesthesiologists to optimize perioperative care of the obese cardiac surgical patient.

Morbid Obesity Alters Both Pharmacokinetics and Pharmacodynamics of Propofol: Dosing Recommendation for Anesthesia Induction

The prevalence of obesity has markedly increased worldwide. Obese patients pose significant challenges to anesthesiologists with regard to accurate dosing of anesthetics due to potentially altered pharmacokinetics (PK). Here we determined the PK and pharmacodynamics (PD) of propofol for anesthesia induction in morbidly obese (MO) subjects (body mass index >35 kg/m(2)) at two dosing regimens: dosing based on total body weight and lean body weight (LBW), respectively. The propofol pharmacokinetic profile was well fitted with a two-compartment model. Both elimination clearance (223%-243% of controls, who had a body mass index <25 kg/m(2); P < 0.01) and peripheral compartment volume (156%-180% of controls; P < 0.01) were significantly increased in MO subjects, resulting in an equal or decreased propofol level in plasma (total body weight-based dosing). Furthermore, propofol PD (measured by the bispectral index) was adequately described by a PK/PD model that linked an effect compartment to the two-compartment PK model through a sigmoidal Emax model. All PD parameters except EC50 values (the half maximal effect concentration) were similar (P > 0.05) between MO subjects and controls. Morbid obesity led to a significant decrease (37.9%-38.6%; P < 0.01) in EC50 values, which suggests increased brain sensitivity to propofol in the MO population. Moreover, dose reduction (i.e., dosing based on LBW) generated identical anesthetic effects in MO subjects compared with controls. In conclusion, morbid obesity significantly altered both PK and PD of propofol. LBW was a better weight-based dosing scalar for anesthesia induction with propofol in MO subjects.