March 1, 1977Cardiovascular Research31 citations
Effect of selected drugs and myocardial infarction on the disappearance of creatine kinase from the circulation in conscious dogs
View Full Paper
Key Result
Myocardial infarction altered the disappearance rate of creatine kinase by <10%, whereas large doses of Nembutal, morphine, or Valium decreased it markedly.
Structured PICO
Does myocardial infarction or administration of selected drugs alter the disappearance rate of creatine kinase from the circulation in conscious dogs?
P
Population
56 conscious dogs evaluated for the effects of myocardial infarction and selected drugs on the disappearance rate of creatine kinase from blood.
I
Intervention
Myocardial infarction (via left anterior descending coronary artery occlusion) and administration of selected drugs (Nembutal 30 mg/kg, morphine 2 mg/kg or 0.2 mg/kg, Valium 1 mg/kg or 0.1 mg/kg)
C
Comparator
Baseline state or low-dose drug administration
O
Outcome
Disappearance rate of creatine kinase (CK) from blood (kd)surrogate
Enzymatic estimates of infarct size using CK disappearance rate are not significantly affected by myocardial infarction itself, but can be markedly altered by high doses of commonly used drugs like morphine and Valium.
Abstract
Estimates of infarct size based on serial plasma creatine kinase (CK) changes have been made utilising the disappearance rate of CK from blood (kd) as one parameter. This study was performed to evaluate the effects on CK disappearance of myocardial infarction per se and selected drugs often used in the management of patients with myocardial infarction. Fifty-six conscious dogs were studied. Canine myocardial CK was isolated and radioactively labelled. Experiments were performed with intravenous injections of unlabelled CK or with radioactively labelled material. After injection, plasma CK activity declined monoexponentially (r = -0.95, n = 30) exceeding the rate of CK disappearance in vitro in whole blood or plasma. Three successive daily determinations of kd differed by less than or equal to 10% in the same dog (n = 5). Removal of radioactively labelled protein from plasma paralleled disappearance of plasma CK enzyme activity for several hours after i.v. injection of 14C-CK (n = 5). Myocardial infarction after occlusion of the left anterior descending coronary artery altered kd by less than 10% (n = 5) estimated after i.v. injection of 14C-CK. Administration of large doses of Nembutal (30 mg-kg-1), morphine (2 mg-kg-1), or Valium (1 mg-kg-1) decreased kd markedly (n = 17), but low doses of morphine (0-2 mg-kg-1) or Valium (0-1 mg-kg-1) did not substantially diminish kd. Thus, enzymatic estimates of infarct size are not likely to be influenced by changes in kd occurring during myocardial infarction. However, modification of estimates may be required when pharmacological interventions are employed, capable of altering CK disappearance.