Digital Library - Spinal Anesthesia

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Management of the Patient during Spinal Anesthetic

Spinal anesthesia can result in significant physiologic affects of on cardiovascular, respiratory and gastrointestinal systems.

Effects of Spinal Anesthesia on the Cardiovascular System

Hypotension:
Hypotension is diagnosed if a patientıs blood pressure decreases 20-25% below their baseline blood pressure. Hypotension induced by spinal or epidural anesthesia is caused by preganglionic block of sympathetic fibers in the anterior root resulting in peripheral vasodilation, reduction in venous return to the heart and a decrease in the cardiac output. If the sympathetic block extends to the level of T1-T4, the cardioaccelator nerves may be blocked leading to bradycardia.

Treatment:
1). Includes administration of IV fluids or slight head-down tilt with raising the legs to improve the venous return and the cardiac output.
2). Patient may need small incremental doses of ephedrine along with increasing the fluids.
3). Atropine 0.3 to 0.4 mg IV if there is bradycardia associated with hypotension.

Respiratory System:
High spinal anesthesia will be accompanied by intercostal paralysis and patient may complain of difficulty in breathing even though diaphragm is intact. The phrenic nerve arises from C3-C5 and is rarely blocked by a spinal anesthetic. The most common cause of apnea following spinal anesthesia is ischemia of the medullary centers resulting from severe hypotension. If respiratory paralysis occurs due to a high spinal, mechanical ventilation with either a bag and mask or endotracheal intubation is indicated.

Gastrointestinal Tract:
Because the sympathetic block results in unopposed parasympathetic activity, the intestines become contracted and hyperactive and sphincters are relaxed. In addition, nausea and vomiting can occur if hypotension occurs during high spinal anesthesia.

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