What is the required infusion rate of propofol (mcg/kg/min) for a 55kg female patient to achieve a target concentration of 2-3 mcg/mL?

Propofol Infusion Rate for Target Concentration of 2-3 mcg/mL in a 55kg Female

For a 55kg female patient to achieve a target propofol concentration of 2-3 mcg/mL, use an infusion rate of 25-50 mcg/kg/min (approximately 82.5-165 mg/hour), which corresponds to the maintenance dosing range established in clinical practice for moderate sedation. 1, 2

Target Concentration Evidence

• The target concentration of 2-3 mcg/mL aligns precisely with established clinical practice for endoscopic sedation. 1
• A recent 2024 study determined that the mean target propofol concentration for sedation during ERCP was 2.21 ± 0.42 µg/ml, which falls directly within your 2-3 mcg/mL target range. 3
• During endoscopic procedures, propofol plasma concentrations are typically titrated between 2-5 µg/mL to maintain patient cooperation and comfort, with 2.3 µg/mL being the median concentration used in closed-loop systems. 1

Specific Dosing Calculation for This Patient

For a 55kg female patient:

• Low end (2 mcg/mL target): Start at 25 mcg/kg/min = 82.5 mg/hour (1.375 mg/min) 2, 4
• Mid-range (2.5 mcg/mL target): Use 37.5 mcg/kg/min = 123.75 mg/hour (2.06 mg/min) 2
• High end (3 mcg/mL target): Titrate up to 50 mcg/kg/min = 165 mg/hour (2.75 mg/min) 2, 4

Initiation Protocol

Avoid bolus loading doses in this patient if there is any cardiovascular concern, as propofol causes dose-dependent hypotension through systemic vasodilation. 2

• If the patient is hemodynamically stable and a loading dose is deemed necessary, use only 5 mcg/kg/min over 5 minutes (approximately 16.5 mg total for this 55kg patient). 2, 4
• Begin maintenance infusion at 25 mcg/kg/min (82.5 mg/hour) immediately after any loading dose. 2
• For hemodynamically unstable patients, skip the loading dose entirely and start directly at 25 mcg/kg/min. 2, 4

Titration Strategy

• Titrate upward in increments of 5-10 mcg/kg/min every 5-10 minutes based on sedation level and clinical response. 2
• Monitor continuously for hypotension, as 5-7% of patients may experience transient desaturation below 90%. 1, 4
• Target light to moderate sedation (patient arousable and able to follow simple commands) rather than deep sedation to minimize complications. 2, 4

Age and Sex Considerations

Female patients and elderly patients require lower propofol doses due to pharmacokinetic differences. 5, 6

• The volume of the central compartment decreases with age, leading to higher peak plasma concentrations for a given dose. 5
• For patients older than 60 years, elimination clearance decreases linearly, necessitating dose reductions. 6
• If this 55kg female is elderly (>60 years), start at the lower end of the dosing range (20-25 mcg/kg/min) and titrate more cautiously. 5

Critical Safety Monitoring

Never exceed 70 mcg/kg/min (231 mg/hour for this 55kg patient) due to risk of Propofol Infusion Syndrome (PRIS). 2, 7, 8

• PRIS has approximately 1% incidence but carries up to 33% mortality. 7, 4
• Monitor for metabolic acidosis, hypertriglyceridemia, hypotension requiring increasing vasopressor support, arrhythmias, acute kidney injury, hyperkalemia, and rhabdomyolysis. 2, 7
• Continuous blood pressure monitoring is essential, especially if cardiovascular disease is present. 2
• If sedation is required beyond 48 hours, switch to dexmedetomidine (0.2-0.7 µg/kg/hr) or midazolam-based sedation to avoid PRIS risk. 7

Contraindications to Verify

• Confirm no egg or soybean allergies (propofol is dissolved in 10% lipid emulsion containing egg phosphatide and soybean oil). 2, 4
• Assess for defective lipid metabolism, pathological hyperlipidemia, lipoid nephrosis, or acute pancreatitis. 2

Nutritional Considerations

• Propofol provides 1.1 kcal/mL from lipid emulsion. 2, 4
• At 165 mg/hour (16.5 mL/hour of 1% solution), this delivers approximately 18 kcal/hour. 2
• Adjust nutritional requirements to prevent overfeeding with prolonged infusions. 2, 4

Common Pitfalls to Avoid

• Never give loading doses to hemodynamically unstable patients. 2, 4
• Never use doses >70 mcg/kg/min or prolonged infusions (>48 hours) without monitoring for PRIS. 2, 7
• Never fail to recognize early signs of PRIS such as unexplained metabolic acidosis. 2, 7
• Expect pain on injection through peripheral veins, though this rarely causes phlebitis. 4
• Do not forget that propofol causes dose-dependent hypotension, which is particularly problematic in hemodynamically unstable patients. 2