Propofol for IV Induction: Three Key Side Effects
Propofol is the recommended primary agent for intravenous induction of anesthesia, with three major side effects: hypotension (20-30% decrease in systolic/diastolic blood pressure), respiratory depression including apnea (occurring in 15.4% of patients), and pain on injection (affecting up to 30% of patients). 1, 2, 3
Why Propofol is the Preferred Choice
The American Society of Anesthesiologists specifically recommends propofol as the primary agent for intravenous induction, administered at 2 mg/kg for standard patients 1. This recommendation is based on propofol's rapid onset (30-45 seconds), predictable effects, and rapid recovery profile that distinguishes it from traditional anesthetic regimens 3, 4.
The Three Major Side Effects
1. Cardiovascular Depression (Hypotension)
Propofol causes dose-dependent myocardial depression and vasodilation, resulting in approximately 20-30% decreases in both systolic and diastolic blood pressure with minimal change in heart rate 2, 5. This effect occurs through:
Critical management: Have vasopressors immediately available (ephedrine or metaraminol) before induction 3. This hypotensive effect is particularly pronounced in volume-depleted patients and those with cardiac disease 6, 2.
2. Respiratory Depression and Apnea
Propofol temporarily depresses respiration, with apnea occurring in 15.4% of patients following intravenous administration 7. Additional respiratory effects include:
- Decreased tidal volume and respiratory rate (23.3% of IV patients) 7
- Depression of ventilatory response to carbon dioxide for 15 minutes or more 7
- Higher risk when combined with other CNS depressants, particularly opioids 7
The majority of serious adverse effects involving oxygenation and ventilation occur when midazolam or other sedatives are combined with medications capable of depressing the central nervous system 7. The incidence is particularly elevated in procedures involving the airway without endotracheal tube protection 2.
3. Pain on Injection
Pain during injection occurs in up to 30% of patients receiving intravenous bolus of propofol 3. This remains a persistent problem even with the newer emulsion formulations 8. Additional injection site reactions include:
Dosing Adjustments to Minimize Side Effects
Standard dosing: 2 mg/kg for healthy patients, administered slowly at approximately 20 mg every 10 seconds 1.
Reduced dosing: 0.5-1.5 mg/kg for elderly, debilitated, or ASA III-IV patients using slow administration 1. The elderly demonstrate marked sensitivity to propofol's cardiovascular effects, requiring closer monitoring for hypotension 9.
Common Pitfalls to Avoid
- Never use propofol in patients with egg, soy, or sulfite allergies (contains 10% soybean oil and 1.2% purified egg phosphatide) 3
- Avoid bolus dosing during maintenance to prevent hemodynamic instability 9
- Do not use in volume-depleted patients without adequate resuscitation as hypotension will be exacerbated 6
- Exercise extreme caution when combining with opioids or other CNS depressants due to synergistic respiratory depression 7, 2
Comparative Context
While propofol causes more cardiovascular depression than etomidate (which has minimal effects on cardiovascular regulation) 2, it offers significant advantages including reduced postoperative nausea and vomiting compared to volatile anesthetics 2, 9. In pediatric comparisons, propofol caused a mean 25% decrease in systolic blood pressure versus 15% with midazolam 7.