Intraoperative Monitoring of the Obese Patient Undergoing Surgery: A Narrative Review

Abstract

With the increasing prevalence of obesity in the population, anaesthetists must confidently manage both the pathophysiological and technical challenges presented in bariatric and non-bariatric surgery. The intraoperative period represents an important opportunity to optimise and mitigate risk. However, there is little formal guidance on what intraoperative monitoring techniques should be used in this population. This narrative review collates the existing evidence for intraoperative monitoring devices in the obese patients. Although a number of non-invasive blood pressure monitors have been tested, an invasive arterial line remains the most reliable monitor if accurate, continuous monitoring is required. Goal-directed fluid therapy is recommended by clinical practice guidelines, but the methods tested to assess this had guarded applicability to the obese population. Transcutaneous carbon dioxide (CO 2 ) monitoring may offer additional benefit to standard capnography in this population. Individually titrated positive end expiratory pressure (PEEP) and recruitment manoeuvres improved intraoperative mechanics but yielded no benefit in the immediate postoperative period. Depth of anaesthesia monitoring appears to be beneficial in the perioperative period regarding recovery times and complications. Objective confirmation of reversal of neuromuscular blockade continues to be a central tenet of anaesthesia practice, particularly relevant to this group who have been characterised as an “at risk” extubation group. Where deep neuromuscular blockade is used, continuous neuromuscular blockade is suggested. Both obesity and the intraoperative context represent somewhat unstable search terms, as the clinical implications of the obesity phenotype are not uniform, and the type and urgency of surgery have significant impact on the intraoperative setting. This renders the generation of summary conclusions around what intraoperative monitoring techniques are suitable in this population highly challenging.

The Effect of Phonomyography Prototype for Intraoperative Neuromuscular Monitoring: A Preliminary Study

“…In any case, this result indicates that PMG could be utilized for dNMB monitoring, filling the research gap of PMG in this degree of muscle relaxation. Furthermore, it suggests the PMG prototype may hold the potential to be a reliable and sensitive neuromuscular-monitoring method for dNMB dependent surgery such as bariatric surgery, aneurysm surgery, and laryngeal microsurgery [40][41][42]. Yet, its efficacy and whether it could improve clinical outcomes of dNMB still need further investigation.…”

The patient with obesity and super-super obesity

“…Many studies in recent years have demonstrated the beneficial role of pulse oximetry and quantitative end tidal CO2 monitoring to assess adequacy of oxygenation and ventilation. [ 46 47 48 ] Although individual facilities worldwide vary in strategy, a major consideration should be utilizing this affordable technology in these higher risk patients as a best practice standard.…”