A Comparison of Nitroglycerin and Nitroprusside for Inducing Hypotension in Children

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Abstract
Intravenous nitroglycerin (NTG) and sodium nitroprusside (SNP) were compared as hypotensive agents in anesthetized children and adolescents. The drugs were studied in a prospective, randomized, double-blind fashion in 14 patients anesthetized with nitrous oxide: oxygen, morphine, and thiopental. NTG in doses as high as 40 .mu.g .cntdot. kg-1 .cntdot. min-1 was ineffective at decreasing mean arterial pressure (MAP) below 55 mmHg or causing a decrease in MAP greater than one-third of baseline values. SNP was uniformly successful at inducing hypotension in all patients, including those patients in whom NTG failed. The dose of SNP required to induce hypotension was 6-8 .mu.g .cntdot. kg-1 .cntdot. min-1. Both NTG and SNP decreased systemic vascular resistance, although SNP did so to a much greater degree than NTG (64% vs. 29%; P < 0.01). Only SNP increased cardiac index significantly (2.27 .+-. 0.35 to 4.44 .+-. 1.36; P < 0.003). Both drugs reflexly increased heart rate, necessitating the use of intravenous propranolol (range from 1 to 3 mg ) in all patients. Both drugs produced small decreases in arterial oxygen tension and increases in the average alveolar-arterial oxygen tension gradient (SNP, 44 .+-. 13 vs. NTG, 41 .+-. 6). SNP use was associated with a slight metabolite acidosis (pH = 7.38 .+-. 0.01; base excess [BE] = -6 .+-. 1). Neither drug produced any other untoward reaction. SNP appears to be the agent of choice for the reliable and sustained induction of deliberate hypotension in children and adolescents.