Which of the following is a common side effect of spinal anesthesia?

Appeared in: RML MAINS 2025

Explanation

Spinal anesthesia involves injecting a local anesthetic into the subarachnoid space, which blocks sympathetic nerve fibers.
This sympathetic blockade causes widespread vasodilation (widening of blood vessels), leading to a decrease in systemic vascular resistance.
The result is a significant and often rapid drop in blood pressure, making hypotension the most frequent and immediate side effect.
This effect is so common that preventative measures, such as IV fluid preloading, are standard practice.

Option A: Spinal anesthesia causes vasodilation, which leads to a decrease, not an increase, in blood pressure.
Option C: While a reflex tachycardia can occur as a compensatory response to hypotension, bradycardia (slow heart rate) is a more common and concerning cardiac effect, especially with a high spinal block.
Option D: Fever is not a common or immediate side effect of single-shot spinal anesthesia.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Side Effects of Spinal Anesthesia as background academic context rather than a clinical decision trigger.
Nurses must anticipate hypotension following spinal anesthesia and ensure that IV fluids and vasopressor medications (like phenylephrine) are immediately available.
Critical nursing monitoring includes checking the patient's blood pressure every 1-2 minutes for the first 15 minutes after the block is administered, as this is the period of highest risk.
Proper patient positioning, specifically left uterine displacement for pregnant patients, is a key nursing intervention to prevent aortocaval compression and augment venous return, thereby mitigating the hypotensive effect.

How to Approach the Question

First, identify the core concept of the question: the physiological effects of spinal anesthesia.
Recall that spinal anesthesia involves injecting a local anesthetic into the subarachnoid space, which affects nerve roots, including those of the sympathetic nervous system.
Consider the primary function of the sympathetic nervous system in this context: maintaining vascular tone (vasoconstriction) and blood pressure.
Reason that blocking the sympathetic nervous system will cause the opposite effect: loss of vascular tone, leading to vasodilation.
Evaluate the options based on this physiological principle. Vasodilation directly causes a drop in blood pressure (hypotension).
Eliminate the other options: Hypertension is the opposite effect. Tachycardia is a possible secondary reaction but less common than bradycardia. Fever is not a direct, acute effect.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 68-90

E6 Pharmacology Nursing Lilley 11e Part 1 p. 200-202

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