Adenosine infusion: a rational approach towards induced hypotension.

OBJECTIVES

To examine the systolic (SBP) and diastolic (DBP) blood pressure (mmHg) and heart rate (beats/min) responses to varying doses and rates of adenosine administration in awake and anesthetized swine.

DESIGN

Adult swine underwent sterile insertion of chronic carotid artery and jugular vein catheters. After recovery, baseline blood pressure and heart rate values were obtained. Three rates (mg/kg/min) of adenosine were infused in a randomized block design (low: 0.06 for 20 mins; medium: 0.12 for 10 mins; and high: 0.24 for 5 mins) to a total dose of 1.2 mg/kg. After 5 mins of infusion, three separate doses (0.3 mg/kg; 0.6 mg/kg; and 1.2 mg/kg) were compared.

RESULTS

In awake animals, only the highest dose significantly decreased (P < or = 0.0001) SBP by 21% and DBP by 43% while increasing heart rate by 32%. At this high dose, the rate of administration was compared. Medium rates significantly decreased (P < or = 0.0002) SPB by 18%, DBP by 33% and elevated heart rate by 27%. High rates caused even greater changes (SBP 21%, DBP 43%, heart rate 32%). The low rate did not alter SBP, DBP or heart rate. Anesthetized swine had a greater decrease in blood pressure, which was not accompanied by alterations in heart rate.

CONCLUSIONS

This study clarifies that the blood pressure and heart rate effects of adenosine are both dose and rate dependent in awake and anesthetized swine. The dose dependent responses can be controlled by the rate of administration. Heart rate increased only in the awake state, while in the anesthetized state no alteration of heart rate was observed. The greater decline in SBP and DBP found in anesthetized swine was likely due to the absence of compensatory increases in heart rate as was observed in awake animals.