Bariatric surgery has emerged as a crucial intervention in the management of morbid obesity
offering significant long-term benefits in terms of weight reduction and improvement of
obesity related comorbidities. However, the anaesthetic management of patients undergoing
bariatric procedures presents unique challenges due to altered pharmacokinetics, increased risk
of airway complications and heightened sensitivity to anaesthetic agents. Inhalational
anaesthesia and total intravenous anaesthesia (TIVA) are both widely used techniques for
inducing and maintaining general anaesthesia. Inhalational agents such as sevoflurane and
desflurane offer ease of administration and rapid titration but may be associated with
postoperative nausea and vomiting (PONV) and environmental pollution. On the other hand,
TIVA—most commonly using propofol with or without adjuncts like remifentanil—provides
a smoother recovery profile, reduced PONV, and better haemodynamic stability in these
patients.
TIVA, especially when delivered via target-controlled infusion (TCI), allows for precise
control of drug concentration at the effect site. This is particularly beneficial in obese patients,
where altered pharmacokinetics can impact drug distribution and metabolism.
Propofol a
widely used intravenous anaesthetic, is commonly administered using target -controlled
infusion systems to maintain stable anaesthesia. These systems rely on pharmacokinetics
models to predict drug concentration and guide infusion rates.
Amongst the various models
developed the Schnider and Eleveld effect site models are two prominent TCI frameworks
employed in clinical practice.
The Schnider model, established earlier, is tailored primarily for
average weight adults, while the more recent Eleveld model is population based and designed
to accommodate a broader range of patient characteristics including age weight and lean body
mass -making it potentially more suitable for obese patients4 which may not be available in all
TCI pumps. Weight correction formula for the same model is CBW=IBW+[0.4×(TBW IBW).
Although the Schnider model uses fixed ke0 while Eleveld uses variable ke0 based on
covariates like age and weight, weight correction formula has been derived for use with the
Schnider model and is widely used in the absence of Eleveld model.
LACUNAE IN EXISTING KNOWLEDGE
The Schnider model is designed to be a universal model across a broad population, however
real-world clinical validation specifically in morbidly obese patients undergoing bariatric
surgery is still limited. Similarly, despite the theoretical advantages of the Eleveld model in the
bariatric populations, there is a lack of robust clinical evidence directly comparing its
performance with the Schnider model in this specific group. This study aims to evaluate and
compare the efficacy, safety and recovery profiles of propofol TCI guided by the Eleveld versus
the Schnider model in adult patients undergoing bariatric surgery. |