Vasopressor spinal anesthesia

Mephentermine (6) is another general adrenergic agonist with both direct and indirect activity. Mephentermine s therapeutic utility is as a parenteral vasopressor used to treat hypotension induced by spinal anesthesia or other drugs. 

Intramuscular vasopressors were evaluated in 108 patients undergoing elective cesarean section under spinal anesthesia in a randomized, double-blind, placebo-controlled comparison of phenylephrine 2 or 4 mg and ephedrine 45 mg, all given immediately after induction of spinal anesthesia [28 ]. Hypotension was defined as a 25% reduction in mean arterial pressure. Rescue intravenous boluses of ephedrine were given for hypotension, nausea, vomiting, or dizziness. Phenylephrine 4 mg was more effective in preventing hypotension than phenylephrine 2 mg or ephedrine and reduced mean arterial pressure more than phenylephrine 2 mg. 

In a randomized, double-blind comparison of boluses of phenylephrine 100 micrograms and ephedrine 10 mg for hypotension (systolic blood pressure below lOOmmHg) in 204 patients undergoing cesarean section under spinal anesthesia, umbilical arterial and venous pH and base excess were similar in the two groups [32 ]. In those who received ephedrine umbilical arterial and venous lactate concentrations were slightly higher and more patients had nausea or vomiting (13% versus 3.9%). Clinical neonatal outcomes were similar. The authors concluded that phenylephrine and ephedrine are both suitable vasopressors for use in non-elective cesarean sections. 

In a randomized, double-blind, controlled comparison of bolus intravenous phenylephrine 100 micrograms and ephedrine 5 mg in maintaining arterial blood pressure during elective section under spinal anesthesia in 62 healthy parturients, both vasopressors restored the systolic and diastolic pressures the mean Apgar scores were similar in the two groups [37 "]. 

The accidental injection of local anesthetics into the subarachnoid space can occur during paravertebral sympathetic blocks or stellate gangUon block. A total spinal anesthesia can result Treatment of this complication consists of immediate artificial ventilation and support of the circulation by intravascular fluids and vasopressors. To prevent such complications, precise CT control is mandatory with contrast medium test injection to confirm the exact position of the needle tip before any drug instillation. 

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