Original Contribution
Hypotension from spinal anesthesia in patients aged greater than 80 years is due to a decrease in systemic vascular resistance

https://doi.org/10.1016/j.jclinane.2011.07.014Get rights and content

Abstract

Study Objectives

To determine the exact mechanism underlying spinal anesthesia-induced hypotension in the elderly patient.

Design

Retrospective case-control study.

Setting

Operating room (OR) in a general hospital.

Measurements

Records from 60 consecutive patients over 80 years of age, who underwent hip fracture repair (intramedullary nail or compression hip screw) during spinal anesthesia were studied. After injection of isobaric 0.5% bupivacaine in the L3-L4 intervertebral space in the lateral decubitus position, patients were turned supine. Acetate Ringer’s solution (300 mL) was infused over 30 minutes after subarachnoid puncture. A decrease in systolic arterial pressure to less than 100 mmHg was treated with an intravenous injection of 5 mg ephedrine. The hypotension group (n=18) comprised patients who required ephedrine during the 30 minutes after the puncture, and the nonhypotension group (n=42) consisted of patients who maintained stable arterial pressure with crystalloid infusion only.

Measurements

Cardiac output (CO) and stroke volume variation (SVV) every 20 seconds using the Vigileo-FloTrac system continuously from arrival in the operating room (OR) to 30 minutes after the subarachnoid puncture were recorded. Serial changes in systemic vascular resistance (SVR), CO, and SVV from baseline after puncture were compared between the two groups.

Main Results

The decrease in SVR over 20 minutes after the puncture was significantly greater in the hypotension group than the nonhypotension group (P = 0.047). Cardiac output was stable in the two groups. Stroke volume variation in the first 10 minutes after the puncture increased to similar levels in the two groups, then decreased gradually to baseline. No significant differences were noted in circulatory parameters on arrival at the OR.

Conclusions

A decrease in SVR, not CO, is the main mechanism of hypotension seen during spinal anesthesia in elderly patients.

Introduction

Hip fracture in elderly patients is associated with high rates of morbidity and mortality [1]. Although spinal anesthesia has several benefits [2], [3], spinal anesthesia-induced hypotension may lead to myocardial ischemia [4] and a reduction in middle cerebral artery velocity caused by impaired cerebral autoregulation [5]. Spinal anesthesia-induced hypotension is due to a decrease in systemic vascular resistance (SVR) associated with sympathetic block and vasodilation [6], [7], [8], especially when the sensory block level spreads to T5 or greater [9]. The hypotension is also due to a decrease in cardiac output (CO) with redistribution of the central volume to the lower extremities and splanchnic beds. However, Rooke et al [6] argued that the primary mechanism of spinal anesthesia-induced hypotension was a decrease in SVR while CO is preserved, even in patients with poor left ventricular function. Crystalloid intravascular volume administration prevents a decrease in CO regardless of preloading [10] or coloading [11], [12], [13] in spinal anesthesia. Although these reports targeted elderly patients, mean patient age in these reports ranged from 60 to 74 years; middle-aged patients also were included in some studies. The main aim of our study was to determine whether a decrease in SVR or CO was the main etiology of spinal anesthesia- induced hypotension in elderly subjects (> 80 yrs of age).

Section snippets

Materials and methods

The study protocol was approved by the Human Ethics Review Committee of Kansai Denryoku Hospital and written, informed consent form was obtained. We investigated all anesthetic records from August 2008 to April 2010 for consecutive elderly patients (age > 80 yrs) who underwent hip fracture repair (intramedullary nail or compression hip screw) during spinal anesthesia.

Results

Based on a power analysis, 18 patients were estimated to be needed in the hypotension group. The 18th patient of the hypotension group was admitted in April 2010. In comparison, 44 patients were included in the nonhypotension group during the study period (between August 2008 and April 2010). Two patients were excluded from analysis due to the development of atrial fibrillation during the study period. Accordingly, we compared the perioperative factors of 18 patients in the hypotension group

Discussion

Spinal anesthesia-induced hypotension in elderly patients, similar to younger patients, is caused primarily by a decrease in SVR [6], [7], [8]. The decrease in SVR during the first 20 minutes after spinal anesthesia was significantly greater in the hypotension group than the nonhypotension group. On the other hand, CO was well maintained in both groups [10], [11], [12], [13], even though cardiac reserve is expected to diminish with age [14]. One possible mechanism for the maintenance of CO is

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