What is the recommended propofol (propofol) infusion rate in ml/hr for a 47 kg patient undergoing neurosurgery?

Propofol Infusion Rate for 47 kg Patient Undergoing Neurosurgery

For a 47 kg patient undergoing neurosurgery, administer propofol at 2.35-4.7 ml/hr (50-100 mcg/kg/min) for maintenance anesthesia, using a 10 mg/ml concentration.

Dosing Calculation

Standard maintenance infusion for neurosurgery is 50-100 mcg/kg/min 1, 2:

• Lower range (50 mcg/kg/min): 47 kg × 50 mcg/kg/min = 2,350 mcg/min = 2.35 mg/min = 2.35 ml/hr (using 10 mg/ml concentration)
• Upper range (100 mcg/kg/min): 47 kg × 100 mcg/kg/min = 4,700 mcg/min = 4.7 mg/min = 4.7 ml/hr (using 10 mg/ml concentration)

Initial Induction and Titration Strategy

Induction Phase

• Avoid rapid bolus dosing in neurosurgical patients 2
• Administer 20 mg every 10 seconds until induction onset (total 0.5-1.5 mg/kg = 23.5-70.5 mg for this patient) 2
• This slower induction minimizes hemodynamic instability and maintains cerebral perfusion pressure above 70 mmHg 3

Initial Maintenance Phase (First 10-15 minutes)

• Start at higher infusion rates of 150-200 mcg/kg/min (7.05-9.4 mg/min = 7.05-9.4 ml/hr) immediately following induction 2
• This translates to 7-9.4 ml/hr for the first 10-15 minutes for this 47 kg patient 2

Subsequent Maintenance Phase

• Decrease infusion by 30-50% after the first half-hour 2
• Target 50-100 mcg/kg/min (2.35-4.7 ml/hr) to optimize recovery times while maintaining adequate anesthesia 1, 2

Critical Neurosurgical Considerations

Cerebral Effects

• Propofol decreases cerebral blood flow, cerebral metabolic rate for oxygen, and intracranial pressure 3, 4
• Maintains cerebral perfusion pressure above 70 mmHg when administered properly 3
• The low intraoperative dosage (50-100 mcg/kg/min) is appropriate because intracerebral surgery is not inherently painful 4

Hemodynamic Management

• Have vasopressors immediately available (ephedrine or metaraminol) as propofol decreases cardiac output, systemic vascular resistance, and arterial pressure in a dose-dependent manner 1, 2
• Administer anticholinergic agents when increases in vagal tone are anticipated, as propofol can cause bradycardia 2
• The slower induction technique (20 mg every 10 seconds) minimizes the 10% decrease in mean arterial pressure typically seen with propofol 3

Adjunctive Analgesic Requirements

Propofol has no analgesic properties 5, therefore:

• Combine with short-acting opioids (fentanyl, alfentanil, sufentanil, or remifentanil) for analgesia during painful portions of surgery 1, 2
• Fentanyl 2 mcg/kg should be added before tracheal intubation, pin head holder application, and skin incision 3
• When propofol is the primary agent, maintenance rates should not be less than 100 mcg/kg/min (4.7 ml/hr for this patient) and must be supplemented with continuous opioid administration 2

Safety Monitoring Requirements

Continuous Monitoring

• Heart rate, blood pressure, and pulse oximetry must be monitored continuously 1, 5
• Use processed EEG monitoring (BIS 40-60) to prevent awareness and avoid excessive depth 1

Propofol Infusion Syndrome (PRIS) Prevention

• Avoid doses >70 mcg/kg/min (3.29 ml/hr for this patient) or prolonged infusions >48 hours 6, 5, 7
• Monitor for signs of PRIS: metabolic acidosis, hypertriglyceridemia, hypotension requiring increasing vasopressor support, arrhythmias, acute kidney injury, hyperkalemia, and rhabdomyolysis 6, 7
• PRIS has 33% mortality and can occur even at lower infusion rates (1.9-2.6 mg/kg/h has been reported fatal) 7

Common Pitfalls to Avoid

• Never use rapid bolus induction in neurosurgical patients, as this increases cardiorespiratory depression including hypotension, apnea, and oxygen desaturation 2
• Do not administer propofol alone without opioid supplementation during painful stimulation, as it lacks analgesic properties 5, 2
• Avoid using propofol in patients with egg, soy, or sulfite allergies 1, 5
• Do not forget to account for propofol's caloric contribution (1.1 kcal/ml) when calculating nutritional requirements for prolonged cases 6, 5
• Approximately 5-7% of patients may experience transient oxygen desaturation below 90% with propofol administration 6, 5