Effect of Gender on Propofol Requirement

Total intravenous anaesthesia (TIVA) has emerged as a viable alternative to inhalational general anaesthesia (GA). Progress into TIVA is much desirable for continued development of precision GA. To this effect, Propofol is a key intravenous agent because of its favorable pharmacokinetic (PK) and pharmacodynamic (PD) profile and broad administration applicability with different methods of delivery: manual and target-controlled infusion [TCI].

The evidence on gender differences during manual/TCI Propofol TIVA suggests that females as compared to males have increased requirement of Propofol and yet have a faster time to recovery from anaesthesia. A 5-10% excess body fat and 15-20% decreased water content in females as compared to males' results in an increase in volume of distribution (Vd) of lipophilic drugs (e.g., Propofol), which consequently necessitates a higher rate of delivery of the Propofol infusion to achieve the same plasma concentration (as males) for clinically acceptable depth-of-anaesthesia. Whereas an increased Propofol sensitivity results in early awakening from anaesthesia.

The studies on gender differences in Propofol requirements and recovery from anaesthesia are largely based on semi-objective methods of Propofol TIVA administration (manual/TCI). The human element in titration and control of manual/TCI delivery of Propofol TIVA in above studies may be a limiting and a confounding factor in interpretating the actual difference induced by the 'gender' context. Whilst processed electroencephalogram (EEG) monitoring (Bispectral index [BIS], entropy, Narcotrend®) facilitates control of Propofol TIVA; it may still be imprecise due to subjective differences in understanding and execution of Propofol TIVA.

A recent advance in Propofol TIVA delivery is the development of automated anaesthesia delivery systems such as closed loop anaesthesia delivery system (CLADS). These systems administer Propofol actuated, titrated, and controlled by patients' processed electroencephalogram (EEG) response as generated by continuously monitored bispectral index (BIS) score. Current evidence suggests that automated Propofol TIVA delivery systems such as closed loop anaesthesia delivery system (CLADS) facilitate precision administration of Propofol than its TCI/manual counterparts.

Despite a plethora of evidence on effectiveness of Propofol TIVA, gender differences in Propofol PK and PD have not been evaluated while using automated systems of delivery. With the premise that widely researched and precise automated closed-loop anaesthesia delivery system (CLADS) has clear advantages (lower 'operator' dependence and inclusion of 'patient' factor) over manual/TCI mode; it is likely that Propofol TIVA administered by CLADS will lend greater objectivity in qualifying and quantifying the inter-gender differences in Propofol consumption and recovery from anaesthesia. The proposed observational study is planned to explore the gender differences in Propofol consumption and recovery from anaesthesia following CLADS controlled Propofol TIVA.

Inclusion criteria

• Age 18-60 years.
• ASA physical status I and II.
• Patients undergoing elective surgeries of minimum 1 hour duration.

Exclusion criteria

• Uncompensated cardiovascular disease (e.g., uncontrolled hypertension, systolic and diastolic dysfunction)
• Hepatic dysfunction (liver enzymes > 2 times the normal range)
• Renal dysfunction (serum creatinine > 1.4 mg/dl)
• Psychiatric or neurological disorder
• Uncontrolled endocrinology disease (diabetes mellitus, hypothyroidism)
• Known allergy/hypersensitivity to the study drug
• History of recent intake of sedative medication or anti-psychotic medication
• Drug dependence/substance abuse
• Requirement of postoperative ventilation
• Refusal to informed consent