Attenuation of Blood Pressure Response to Laryngoscopy and Tracheal Intutation with Sodium Nitroprusside

Abstract

The time course and magnitude of change in mean arterial pressure (MAP) and heart rate (HR) following a single rapid intravenous injection of 1 fig/kg and 2μg/kg of sodium nitroprusside (SNP) were determined in six anesthetized patients in the absence of concurrent stimulation produced by laryngoscopy or surgery. These data indicated that SNP administered 15 seconds before starting laryngoscopy would match the blood pressure lowering effects of SNP with the increase in blood pressure produced by laryngoscopy and tracheal intubation. The change in MAP and HR during and after laryngoscopy for tracheal intubation was determined in patients receiving 1 μg/kg (10 patients) or 2 μg/kg (10 patients) of SNP 15 seconds before starting laryngoscopy. These data were compared with data for 10 patients not receiving SNP. All patients studied were scheduled for elective saphenous vein to coronary artery bypass graft operations. Immediately after tracheal intubation the maximum increase in MAP above awake levels was 18 torr (p < 0.05) and 13 torr (p < 0.05) with 1 μg/ kg and 2 μg/kg of SNP, respectively, given 15 seconds before laryngoscopy whereas mean arterial pressure increased 40 torr (p < 0.05) after tracheal intubation in patients not given SNP. The magnitude of MAP increase was not significantly different with 1 μg/kg or 2 μg/kg of SNP (p > 0.05) whereas the increase without SNP was significantly greater (p < 0.05) than with prior SNP. SNP had no effect on the increase in HR associated with tracheal intubation. A single rapid intravenous injection of SNP (1 to 2 μg/kg) is a practical pharmacologic method to attenuate blood pressure increases during direct laryngoscopy and tracheal intubation. Prevention of hypertension during the sequence surrounding tracheal intubation is particularly important in patients with decreased myocardial reserve or intracranial pathology.