Preoperative increased heart rate is related to the blood pressure decrease during spinal anesthesia for cesarean delivery

ABSTRACT

BACKGROUND: Hypotension is a very common side effect of spinal anesthesia for cesarean delivery. If we can predict the degree of blood pressure decrease after spinal anesthesia, hypotension will be treated better. Tachycardia may reflect the effective circulatory volume deficit. We studied if preoperative heart rate can predict the degree of hypotension after spinal anesthesia. METHODS: Fifty-two parturients for elective cesarean delivery were enrolled and the gestation periods of all parturient were over 37 weeks. In the supine position, noninvasive blood pressure (BP) and heart rate (HR) were measured as baseline values. After change to the right decubitus position, spinal anesthesia was done. Hyperbaric bupivacaine 8 mg and fentanyl 15 microg were injected intrathecally through 26G spinal needle. After return to the wedged supine position, BP and HR were measured every minute until anesthetic level was fixed. If mean BP decreased below 70% value of baseline, ephedrine 5 mg was injected intravenously. The lowest mean BP, hypotension (<80% of baseline) and total ephedrine requirement were recorded. Retrospective analysis was done after grouping by baseline heart rate (below 80 vs. over 80 beats/min). RESULTS: The patients who had more rapid heart rate before anesthesia, tended to have more decrease of mean BP during spinal anesthesia (P < 0.001, R = 0.45). In retrospective group analysis, the incidence of hypotension was lower in low HR group (46% vs. 83%, P = 0.014). CONCLUSIONS: If preoperative heart rate is over 80 beats/min, careful management is required to prevent hypotension during spinal anesthesia for cesarean delivery.