Hypotension produced by powerful peripheral adrenergic blocking agents, chlorpromazine, or pheochromocytomectomy may also require more intensive therapy. If the drop size of the infusion system varies from the 20 dropsy per mL, the dose must be adjusted accordingly. The rate of wflow is then adjusted until the desired blood pressure level is obtained. Hypertension should be avoided. The blood pressure should be checked frequently.
Arrhythmias are rare.
Spinal Anesthesia - Hypotension Routine parenteral use of phenylephrine hydrochloride has been recommended for the prophylaxis and treatment of hypotension during spinal anesthesia. It is best administered subcutaneously or intramuscularly three or four minutes before injection of the spinal anesthetic. For hypotensive emergencies during spinal anesthesia, phenylephrine hydrochloride may be injected intravenously, using an initial dose of 0.2 mg. Any subsequent dose should not exceed the previous dose by more than 0.1 mg to 0.2 mg and no more than 0.5 mg should be administered in a single dose. To combat hypotension during spinal anesthesia in children, a dose of 0.5 mg to 1 mg per 25 pounds body weight, administered subcutaneously or intramuscularly, is recommended.