A 58-year-old man with hypertension and type 2 diabetes mellitus is scheduled for elective laparoscopic cholecystectomy. After induction with propofol 2 mg/kg and succinylcholine 1.5 mg/kg, his blood pressure drops from 140/90 mmHg to 85/50 mmHg within 2 minutes. Oxygen saturation remains 98% on 100% O₂. Heart rate is 62 bpm. There is no evidence of anaphylaxis, malignant hyperthermia, or acute blood loss. What is the most likely cause of hypotension in this patient?

Explanation

## Diagnosis: Propofol-Induced Hypotension **Key Point:** Propofol causes profound vasodilation and myocardial depression, leading to a rapid and significant drop in blood pressure within 1–2 minutes of induction. This is the most common cause of induction-related hypotension in healthy and comorbid patients. ### Mechanism of Propofol Hypotension 1. **Vasodilation** — Direct relaxation of vascular smooth muscle via GABA~A~ receptor potentiation and calcium channel inhibition 2. **Negative inotropism** — Reduced myocardial contractility and cardiac output 3. **Reduced sympathetic tone** — Blunting of baroreceptor reflex 4. **Timing** — Hypotension appears within 30–60 seconds and peaks at 1–2 minutes **High-Yield:** Propofol hypotension is **dose-dependent** and **reversible**. It is NOT accompanied by reflex tachycardia in most cases (unlike hypovolemia); bradycardia is common. ### Clinical Clues in This Case | Feature | Finding | Significance | |---------|---------|---------------| | **Timing** | Within 2 min of induction | Typical of propofol | | **Oxygen saturation** | 98% on 100% O₂ | Rules out hypoxia as primary cause | | **Heart rate** | 62 bpm (bradycardia) | Consistent with propofol; no reflex tachycardia | | **No anaphylaxis signs** | No rash, bronchospasm, or angioedema | Excludes allergic reaction | | **Succinylcholine given** | 1.5 mg/kg (normal dose) | Hyperkalemia unlikely in non-muscular patient | ### Management 1. **Immediate:** Reduce FiO₂ if needed; position supine with legs elevated 2. **Fluid bolus:** 500 mL crystalloid IV over 2–3 minutes 3. **Vasopressor:** Ephedrine 5–10 mg IV or phenylephrine 50–100 mcg IV 4. **Reduce propofol dose:** In elderly or hemodynamically unstable patients, use 1–1.5 mg/kg instead of 2 mg/kg **Clinical Pearl:** Propofol hypotension is self-limited and usually resolves within 2–3 minutes with supportive care and fluids. It does NOT indicate a contraindication to propofol in future anesthetics; dose reduction and co-induction with opioids (remifentanil, fentanyl) are preventive strategies. ### Why Other Options Are Wrong - **Succinylcholine hyperkalemia:** Would cause peaked T waves, widened QRS, and dysrhythmias on ECG; typically occurs 30–60 seconds after administration in susceptible patients (burns, crush injury, denervation). This patient has no risk factors. - **Anaphylaxis:** Would present with urticaria, bronchospasm, stridor, or facial edema; oxygen saturation would fall; heart rate would be elevated. - **Adrenal insufficiency:** Rare as a primary cause of induction hypotension; would manifest as refractory hypotension despite fluids and vasopressors over several minutes. [cite:Gupta 5e Ch 10]