Effect of calcium channel blockers on hemodynamic responses to defibrillation.
The hemodynamic response to sequences of ventricular fibrillation and defibrillation includes an adrenergic component that is important for the maintenance of blood pressure after successful defibrillation. Because calcium channel blocking drugs have antiadrenergic effects, we hypothesized that they might blunt the adrenergic response to defibrillation. Ventricular fibrillation was induced in 35 closed-chest dogs. Each received 4 to 7 direct current transthoracic shocks at three energy levels to determine defibrillation energy requirements. Heart rate and blood pressure were recorded. Energy sequences were repeated after 45 minutes of no intervention (control, n = 5) or after 45-minute infusions of diltiazem (0.1 mg/kg/min, n = 10), verapamil (0.1 mg/kg bolus plus 0.01 mg/kg/min, n = 10), or nifedipine (40 micrograms/min for 3 minutes plus 2 to 20 micrograms/min adjusted to maintain a 10 mm Hg drop in mean arterial pressure, n = 10). Our results show that the normal post-shock rise in mean arterial pressure was blunted by the calcium channel blockers diltiazem (systolic arterial pressure at 15 and 60 seconds post-shock, pre-drug versus post-drug: 102 +/- 9 versus 64 +/- 9 mm Hg and 113 +/- 10 versus 87 +/- 6 mm Hg; p less than 0.05) and verapamil (108 +/- 9 versus 78 +/- 12 mm Hg and 113 +/- 7 versus 90 +/- 10 mm Hg, p less than 0.05). There were no differences in blood pressure responses after nifedipine treatment or no drug. Heart rate responses were not altered by diltiazem or verapamil; after nifedipine administration, post-shock heart rates were slower.(ABSTRACT TRUNCATED AT 250 WORDS)
Hite
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PR
Cardiovascular Center, University of Iowa, Iowa City.
Schröder
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E
Kieso
R A
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Fox-Eastham
K
K
Kerber
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RE
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002304:Cardiac Pacing, Artificial; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D004554:Electric Countershock; D006329:Heart Conduction System / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D014693:Ventricular Fibrillation / Q000503:physiopathology*; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D014700:Verapamil; D004110:Diltiazem; D009543:Nifedipine