Anaesthetic Preparation of Obese Patients: Current Status on Optimal Work-up

Anesthesia for Morbidly Obese Patients

BACKGROUND

The prevalence of morbid obesity (BMI >35 kg/m2) has risen steadily in recent decades. With the corresponding rise in the number of bariatric operations, anesthesiologists deal with this patient group more commonly than before, particularly in specialized centers.

METHODS

This review is based on publications retrieved by a selective search in PubMed, including current guidelines and recommendations issued by specialist societies, as well as expert opinion.

RESULTS

In the anesthesiological care of morbidly obese patients, a preoperative assessment and risk stratification are just as important as the thoughtful selection of the anesthesia technique, the drugs used and their dosage, and perioperative management. A thorough understanding of the pathophysiological changes and comorbidities of morbid obesity and the associated risks is essential. The risk of pulmonary complications such as respiratory failure, hypoxia, and apnea is markedly higher in morbidly obese patients, especially those with obstructive sleep apnea. Short-acting, less lipophilic anesthetic drugs are particularly useful, as is multimodal pain therapy for the avoidance of high opiate doses. The indication for intensified postoperative monitoring depends on the patient's preexisting illnesses, the type of anesthesia, and the type of surgical procedure. Regional anesthetic techniques should be used if possible.

CONCLUSION

The perioperative care of morbidly obese patients presents special challenges. The anesthesiologist must be aware of potential comorbidities, specific risks, and pathophysiological changes in order to provide adequate care to this patient group.

Limited condylar mobility by ultrasonography predicts difficult direct laryngoscopy in morbidly obese patients: An observational study

Background and Aims

Unpredictable difficult laryngoscopy remains a challenge for anaesthesiologists, especially in morbidly obese patients. The present study aimed to determine the efficacy of different sonographic measures as predictors of difficult laryngoscopy in morbidly obese patients undergoing elective surgery.

Methods

This observational study evaluated 70 morbidly obese adult patients (body mass index >35 kg/m²) undergoing elective surgery under general anaesthesia with tracheal intubation. Pre-operative clinical and ultrasonographic variables (anterior condylar translation, tongue thickness, hyomental distance and oral cavity height) associated with difficult direct laryngoscopy ([Cormack Lehane (CL) grade>2]) were analysed. The primary outcome was to determine the efficacy of the above-mentioned sonographic measures as predictors of difficult laryngoscopy (CL grade >2). The secondary outcome compared ultrasonographic predictors with clinical predictors in morbidly obese patients for determining difficult direct laryngoscopy.

Results

Amongst the primary outcome measures, limited condylar mobility (anterior condylar translation <9.25 mm) [odds ratio (OR) 0.3, confidence interval (CI):1.04-1.22;P<0.001;area under curve (AUC):0.8] and increased tongue thickness >5.85 cm [OR: 3.2, CI: 1.05-10; P < 0.04; AUC: 0.73] were two independent sonographic predictors for difficult direct laryngoscopy by multivariate logistic regression and receiver operating characteristic curve analyses in morbidly obese patients. The secondary outcome suggested that as compared to clinical predictors such as Mallampati grade and thyromental distance, ultrasonographic variables such as tongue thickness and limited condylar mobility (sensitivity: 56.4%, 70.9%, 66.7% and 93.3%, respectively) better predicted difficult direct laryngoscopy in morbidly obese patients.

Conclusion

Limited condylar mobility and increased tongue thickness are independent sonographic predictors of difficult direct laryngoscopy in morbidly obese patients.

Perioperative mortality in bariatric surgery: meta-analysis

BACKGROUND

Bariatric surgery is an established treatment for severe obesity; however, fewer than 1 per cent of eligible patients undergo surgery. The perceived risk of surgery may contribute to the low uptake. The aim of this study was to determine perioperative mortality associated with bariatric surgery, comparing different operation types and data sources.

METHODS

A literature search of Ovid MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials was conducted to identify studies published between 1 January 2014 and 31 July 2020. Inclusion criteria were studies of at least 1000 patients reporting short-term mortality after bariatric surgery. Data were collected on RCTs. Meta-analysis was performed to establish overall mortality rates across different study types. The primary outcome measure was perioperative mortality. Different operation types were compared, along with study type, in subgroup analyses. The study was registered at PROSPERO (2019: CRD 42019131632).

RESULTS

Some 4356 articles were identified and 58 met the inclusion criteria. Data were available on over 3.6 million patients. There were 4707 deaths. Pooled analysis showed an overall mortality rate of 0.08 (95 per cent c.i. 0.06 to 0.10; 95 per cent prediction interval 0 to 0.21) per cent. In subgroup analysis, there was no statistically significant difference between overall, 30-day, 90-day or in-hospital mortality (P = 0.29). There was no significant difference in reported mortality for RCTs, large studies, national databases or registries (P = 0.60). The pooled mortality rates by procedure type in ascending order were: 0.03 per cent for gastric band, 0.05 per cent for sleeve gastrectomy, 0.09 per cent for one-anastomosis gastric bypass, 0.09 per cent for Roux-en-Y gastric bypass, and 0.41 per cent for duodenal switch (P < 0.001 between operations).

CONCLUSION

Bariatric surgery is safe, with low reported perioperative mortality rates.

Intraoperative lidocaine infusion and 24-hour postoperative opioid consumption in obese patients undergoing laparoscopic bariatric surgery

BACKGROUND

Bariatric surgery is the most effective long-term treatment for obesity. Opioid-sparing anesthesia and multimodal analgesia such as lidocaine infusion have been recommended in these patients to reduce opioid-related complications. However, evidence supporting its use for bariatric surgery population is limited.

OBJECTIVE

To investigate whether intraoperative lidocaine infusion is associated with decreasing opioid consumption in laparoscopic bariatric surgery.

SETTING

A university hospital, California, USA.

METHODS

In this retrospective cohort study, outcomes among consecutive obese patients undergoing laparoscopic bariatric surgery between January 2016 to December 2018 were evaluated to determine the impact of adjunctive intraoperative lidocaine infusion on 24-hour postoperative opioid consumption. Secondary outcomes, including opioid consumption during hospitalization, length of stay, and postoperative complications were determined. Post hoc analyses were performed exploring possible dose effects and drug-drug interactions. Univariable and multivariable analyses were performed to identify factors associated with opioid consumption.

RESULTS

Among 345 patients, 54 (15.7%) received intraoperative lidocaine infusion (L+) whereas 291 (84.3%) did not receive intraoperative lidocaine infusion (L-). Both L+ and L- groups shared similar demographic characteristics. The 24-hour postoperative opioid consumption was 17.6% lower in L+ (95% confidence interval -28.4 to -5.2, P = .007), but nonsignificantly lower in the multivariate model (12.8%, 95% confidence interval -24.4 to .5, P = .06). Opioid consumption during hospitalization, length of stay, and other clinically significant outcomes did not differ. However, subgroup analysis restricted to opioid-naïve patients indicated significantly reduced opioid consumption in the L+ group. Post hoc analysis suggested interaction between lidocaine and ketamine in decreasing 24-hour postoperative opioid consumption.

CONCLUSIONS

Intraoperative lidocaine infusion was not significantly associated with decreasing 24-hour postoperative opioid consumption in obese patients undergoing laparoscopic bariatric surgery.

Impact of body mass index on utilization of selected hospital resources for four common surgical procedures

BACKGROUND

Evidence about the impact of obesity on surgical resource consumption in the Australian setting is equivocal. Our objectives were to quantify the prevalence of obesity in four frequently performed surgical procedures and explore the association between body mass index (BMI) and hospital resource utilization including procedural duration, length of stay (LOS) and costs.

METHODS

A retrospective cohort study of patients undergoing four surgical procedures at a tertiary referral centre in New South Wales, between 1 January 2016 and 31 December 2016, was conducted. The four surgical procedures were total hip replacement, laparoscopic appendectomy, laparoscopic cholecystectomy and hysteroscopy with dilatation and curettage. Surgical groups were stratified according to BMI category.

RESULTS

A total of 699 patients were included in the study. The prevalence of obesity was significantly higher than local and national population estimates for all procedures except appendectomy. BMI was not associated with increased hospital resource utilization (procedural, anaesthetic or intensive care stay duration) in any of the four surgical procedures examined after controlling for age, gender and complexity. For other outcomes of hospital resource utilization (LOS and cost), the relationship was inconsistent across the four procedures examined. A high BMI was positively associated with higher LOS, medical costs and allied health costs in those who underwent an appendectomy, and critical care costs in those who underwent laparoscopic cholecystectomy.

CONCLUSION

Obesity was common in patients undergoing four frequently performed surgical procedures. The relationship between BMI and hospital resource utilization appears to be complex and varies across the four procedures examined.