Unexplained hypotension after spinal anesthesia in a patient on an SGLT2 inhibitor
A 68-year-old man (BMI 31, type 2 diabetes, eGFR 52) is scheduled for open inguinal hernia repair under spinal anesthesia. His medications include empagliflozin 10 mg daily, metformin, lisinopril 20 mg, and atorvastatin. He has been fasting since midnight for a 07:30 case. Preoperative glucose is 118 mg/dL and he is asymptomatic. The anesthesiologist decides to proceed. After intrathecal bupivacaine 12 mg, sensory level reaches T6 within 10 minutes. Blood pressure falls from 148/82 to 82/44 mmHg with a heart rate of 58 bpm. A 500 mL crystalloid bolus and two doses of phenylephrine 100 mcg have minimally improved pressure. He is drowsy but arousable, and reports mild nausea.
1. Identify the most likely contributors to this patient's refractory hypotension and bradycardia, and explain how the perioperative medication regimen and fasting state alter your differential.
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The differential should integrate several interacting mechanisms rather than defaulting to "spinal hypotension" alone.
- Neuraxial sympathectomy: a T6 level blocks cardiac accelerator fibers (T1–T4) in some patients, producing bradycardia and reduced contractility alongside vasodilation. This is expected but usually responds to vasopressors and volume.
- ACE inhibitor effect: lisinopril taken the morning of surgery (or continued with a long half-life) blunts the angiotensin II response to sympathectomy, making hypotension deeper and more vasopressor-dependent. The 2014 ACC/AHA guidance permits continuation, but the clinician must anticipate reduced vasopressor responsiveness.
- Volume state: prolonged fasting plus an SGLT2 inhibitor causes mild osmotic diuresis and relative hypovolemia; the patient may already be down 500–1000 mL before the spinal.
- Euglycemic DKA risk: empagliflozin plus fasting plus surgical stress can produce ketoacidosis with normal or near-normal glucose. Nausea and drowsiness in a patient with a normal glucose should prompt consideration of ketones and an ABG, not just assumption of spinal-related nausea.
- Bradycardia with hypotension warrants atropine or ephedrine rather than repeated pure alpha agonism; phenylephrine can worsen reflex bradycardia.
Management: escalate to ephedrine or a low-dose epinephrine infusion if bradycardia persists, check point-of-care ketones and a blood gas, and consider canceling or converting to GA with invasive monitoring if the picture does not correct.
2. The surgeon requests that the case proceed and asks whether the SGLT2 inhibitor matters for a short hernia repair. Justify a perioperative plan that addresses the medication, monitoring, and disposition.
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The SGLT2 inhibitor is highly relevant even for a short case.
Evidence and guidance: Multiple society advisories (ASA, FDA, multisociety guidance) recommend holding SGLT2 inhibitors for at least 3–4 days before elective surgery because of the risk of euglycemic diabetic ketoacidosis (euDKA). The risk is driven by fasting, surgical stress, and reduced carbohydrate intake, not by hyperglycemia-glucose may be normal or only modestly elevated.
Plan:
- If the case is elective and can be delayed, postpone and hold empagliflozin for 3–4 days preoperatively, with a documented plan for glucose management.
- If proceeding emergently, check beta-hydroxybutyrate and a venous blood gas; if ketones are elevated or the patient is acidotic, cancel and treat.
- Intraoperatively, avoid prolonged fasting and consider dextrose-containing fluids to suppress ketogenesis. Monitor glucose hourly and check ketones if the patient becomes nauseated, tachypneic, or drowsy.
- Anticipate greater hypotension from combined ACE inhibitor and SGLT2 effects; have vasopressors ready and consider an arterial line if the hemodynamic picture is labile.
- Postoperatively, do not restart the SGLT2 inhibitor until the patient is eating and drinking reliably; monitor for euDKA in the first 24–48 hours.
Disposition: Given the refractory hypotension and drowsiness, a higher-acuity postoperative setting or extended observation is reasonable until the hemodynamic and metabolic picture is clear.