Hypotension and bradycardia after spinal anesthesia for hip fracture
74-year-old woman, 62 kg and 155 cm, admitted with a displaced femoral neck fracture after a fall at home; surgery is scheduled for the next morning. History: hypertension treated with atenolol 50 mg daily and ramipril 5 mg daily (ramipril withheld on the morning of surgery, atenolol continued), no angina, NT-proBNP 320 pg/mL, creatinine 118 micromol/L. Baseline blood pressure has been 150/80 mmHg. Spinal anesthesia is performed at L3-L4 with 2.5 mL of 0.5% hyperbaric bupivacaine. Ten minutes later the sensory block is at T8, blood pressure is 78/42 mmHg, heart rate 46/min, SpO2 96% on room air, and she is awake but nauseated and pale. She has received 500 mL of crystalloid and ephedrine 10 mg: blood pressure 90/50 mmHg, heart rate 50/min. A second 5 mg bolus of ephedrine is given; two minutes later the heart rate is 98/min, blood pressure 76/40 mmHg, and she says she feels worse.
1. Interpret the hemodynamic sequence and choose your next vasoactive drug, with dose, route and rationale.
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What is happening. The spinal produced a sympathectomy to T8: venodilation, reduced preload and reduced systemic vascular resistance. Heart rate 46/min with a high block is the Bezold-Jarisch pattern - reduced venous return triggers paradoxical vagal afferent firing, giving bradycardia and vasodilation together. Atenolol blunts the compensatory tachycardia, and the ramipril withdrawal does not restore angiotensin-mediated vasoconstriction within 24 hours.
Why ephedrine failed the second time. Ephedrine is an indirect agent: it releases noradrenaline and has both alpha and beta activity. In an elderly patient with a depleted sympathetic response, the beta effect dominates - heart rate rises to 98/min while the blood pressure falls further, because beta-2 vasodilation and increased myocardial oxygen demand outweigh the alpha-mediated vasoconstriction. Tachycardia with worsening hypotension after ephedrine means the drug is doing harm.
Next step: stop ephedrine. Start phenylephrine 50-100 micrograms IV boluses, or better, a phenylephrine infusion at 25-50 micrograms/min titrated to a MAP of 80-90 mmHg. Phenylephrine is a direct alpha-1 agonist: it restores vascular tone and venous return without beta-2 vasodilation, and the reflex bradycardia is usually acceptable at a heart rate of 50-60/min. If bradycardia persists below 45/min with hypotension, add atropine 0.3-0.6 mg IV. Give a further crystalloid bolus only if there is evidence of hypovolemia - the fracture itself can sequester blood - and reassess the block height and the surgical field for hidden bleeding, including a hemoglobin check.
2. Her baseline blood pressure is 150/80 mmHg. What MAP will you target, and how do you weigh that target against cardiac risk and the timing of surgery?
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Target. A MAP of 65 mmHg is the general floor, but in a chronically hypertensive elderly woman the autoregulatory curve is shifted right. Aim for a MAP of 80-90 mmHg - roughly within 20-25% of her baseline MAP of about 103 mmHg - and avoid swings in either direction. A MAP of 65 mmHg that would be acceptable in a young patient may cause cerebral and renal hypoperfusion here, while a MAP of 110 mmHg risks bleeding and myocardial strain.
Cardiac risk. She has hypertension, an NT-proBNP of 320 pg/mL and a creatinine of 118 micromol/L, so she is at elevated risk of perioperative cardiac events even without angina. Persistent tachycardia at 98/min with hypotension is the dangerous combination - it increases myocardial oxygen demand while coronary perfusion pressure falls. That is another argument for an alpha agonist rather than repeated ephedrine, and for an arterial line if the hemodynamics remain unstable. A cautious fluid strategy also matters: over-resuscitation in an elderly patient with possible diastolic dysfunction produces pulmonary edema without fixing the pressure.
Timing. Hip fracture surgery is best performed within 48 hours; delay increases mortality, pressure injury and delirium. Her ramipril is appropriately withheld, she is not on anticoagulation, and this is not a reason to postpone. The decision is not whether to operate but how to optimise hemodynamics, analgesia and temperature before and during transfer. Discuss the anesthetic plan with the team: a lighter spinal, a combined spinal-epidural, or general anesthesia with a working arterial line are all reasonable if the current hemodynamics cannot be stabilised.
3. Two hours later, with a phenylephrine infusion at 30 micrograms/min, blood pressure is 118/70 mmHg and heart rate 72/min, but she is confused and SpO2 is 91% on 4 L/min. How do you approach this?
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Treat this as a new problem, not as residual sedation. The differential is broad and several causes are rapidly fatal.
Airway and breathing first. Confusion plus desaturation in an elderly patient after a spinal is fat embolism, pulmonary embolism, aspiration, fluid overload or opioid-related hypoventilation until proven otherwise. Check the airway, auscultate, review the total opioid dose, and get an arterial blood gas and a chest radiograph. If she is hypoventilating, support ventilation rather than simply increasing oxygen.
Circulation and perfusion. Recheck the blood pressure and lactate. A falling blood pressure with confusion could be a bleed into the thigh, a retroperitoneal hematoma, or a myocardial infarction. Get an ECG and troponin.
Neurological causes. Delirium is common after hip fracture and is frequently multifactorial - pain, opioids, anticholinergics, urinary retention, constipation, hypoxia, electrolyte disturbance, and the fracture itself. Check a glucose, sodium, calcium and hemoglobin. Consider whether the phenylephrine infusion is excessive for her cerebral autoregulation; a MAP of 118 mmHg may be more than she needs. Also consider local anesthetic toxicity, although the spinal dose was small and the timing is late.
Action. Reduce the phenylephrine to target a MAP of 85-90 mmHg, correct hypoxia, review and reduce opioids, treat pain with multimodal non-opioid agents, screen for delirium with a validated tool, and involve the orthogeriatric team. Document the sequence; if the confusion persists, image the head and the pulmonary vasculature.