From the Guidelines
Propofol should be dosed based on lean body weight (LBW) for maintenance, especially in obese patients, to avoid overdosing and minimize the risk of hemodynamic instability. When calculating the dose of propofol, it is essential to consider the patient's lean body weight, as the pharmacodynamic effects of propofol correlate better with lean tissue than with total body weight 1. For induction, the standard adult dose is 1.5-2.5 mg/kg of total body weight. However, for maintenance infusions, particularly in obese patients (BMI >30), using lean body weight or ideal body weight is recommended at rates of 25-75 mcg/kg/min 1.
Key Considerations
- Propofol is lipophilic and distributes into adipose tissue, but its pharmacodynamic effects correlate better with lean tissue 1.
- Using total body weight for maintenance dosing in obese patients can lead to excessive sedation, prolonged recovery times, and increased risk of hemodynamic instability including hypotension 1.
- The clinical endpoint (level of sedation or anesthesia) should always guide titration regardless of the weight-based calculation used, with close monitoring of vital signs and sedation depth.
- Lean body weight can be calculated using the formula: LBW (kg) = 6680 + (216 BMI (kg.m²)) for men and LBW (kg) = 8780 + (244 BMI (kg.m²)) for women 1.
Recommendations
- Use lean body weight or ideal body weight for maintenance dosing of propofol in obese patients (BMI >30) 1.
- Avoid using total body weight for maintenance dosing in obese patients to minimize the risk of overdosing and hemodynamic instability 1.
- Monitor vital signs and sedation depth closely during propofol infusion, and adjust the dose accordingly 1.
From the FDA Drug Label
Adults Propofol clearance ranges from 23 mL/kg/min to 50 mL/kg/min (1. 6 L/min to 3. 4 L/min in 70 kg adults). Propofol has a steady-state volume of distribution (10-day infusion) approaching 60 L/kg in healthy adults. The dosing of propofol is based on total body weight, as indicated by the units of measurement for clearance (mL/kg/min) and volume of distribution (L/kg) 2.
- Key points:
- Clearance is expressed in mL/kg/min
- Volume of distribution is expressed in L/kg There is no direct information in the label to suggest that propofol is dosed on lean body mass.
From the Research
Propofol Dosing in Morbidly Obese Patients
- The appropriate dosing of propofol in morbidly obese patients is a topic of ongoing research, with studies suggesting that dosing based on lean body weight (LBW) or fat-free mass (FFM) may be more accurate than dosing based on total body weight (TBW) 3, 4, 5, 6, 7.
- A study published in 2011 found that LBW is a more appropriate weight-based scalar for propofol infusion for induction of general anesthesia in morbidly obese subjects 3.
- Another study published in 2016 found that morbid obesity significantly altered both the pharmacokinetics and pharmacodynamics of propofol, and that LBW was a better weight-based dosing scalar for anesthesia induction with propofol in morbidly obese subjects 4.
- A 2017 study compared propofol dosing based on LBW and bispectral index (BIS) targeting, and found that patients in the LBW group required additional propofol to achieve an observer's assessment alertness/sedation scale (OAA/S) score of 0 5.
- A 2020 study found that the optimal dose of propofol for anesthesia induction in morbidly obese patients was 2.310-3.567 mg/kg when calculated based on LBW 6.
- A 2023 study compared propofol dosing based on FFM and ideal body weight (IBW), and found that dosing based on FFM was more favorable in terms of the adequacy of anesthesia 7.
Key Findings
- LBW or FFM may be a more accurate basis for propofol dosing in morbidly obese patients than TBW 3, 4, 5, 6, 7.
- Morbid obesity can alter the pharmacokinetics and pharmacodynamics of propofol, leading to changes in dosing requirements 4.
- The optimal dose of propofol for anesthesia induction in morbidly obese patients may vary depending on the specific dosing regimen and patient population 5, 6.