The Annals of Thoracic Surgery, Vol 22, 557-571, Copyright © 1976 by The Society of Thoracic Surgeons
Myocardial injury associated with potassium arrest
RM Engelman, G Baumann, AD Boyd and F Kaplan
The relative efficacy of potassium-induced ischemic arrest using buffered,
isosmotic potassium (25 mEq/liter) was compared with hypothermic arrest in
an experimental protocol employing an intact canine heart preparation.
Myocardial function (LVSW, dp/dt max), serum creatine phosphokinase levels,
myocardial perfusion, and light and electron microscopical examination of
the heart were assessed in five groups of 5 dogs each. There was one
control group (90 minutes of bypass, no anoxia) and four experimental
groups, each subjected to 1 hour of ischemic arrest and 30 minutes of
reperfusion, comparing normothermic ischemic arrest (NIA), hypothermic
ischemic arrest (myocardial temperature less than 25 degrees C) (HIA),
normothermic potassium arrest (NKA), and hypothermic potassium arrest
(HKA). Myocardial function decreased significantly following NIA and NKA
but remained essentially equal in the control, HIA and HKA groups. Serum
creatine phosphokinase analysis documented a significant increase in each
group of animals: 2,250 mU after NIA, 1,778 mU after NKA, 1,388 mU after
HIA, 1,220 mU after HKA, and 838 mU after control bypass. Left ventricular
myocardial perfusion was unmeasurably low after NIA, reduced to 111 m/100
gm of tissue/min after NKA, and increased to 165 to 188 ml/100 gm/min in
the control, HIA and HKA groups. Electron microscopical studies showed a
range of myocardial changes, from probably irreversible damage after NIA to
similar but less diffuse changes after NKA, and to potentially reversible
changes after HKA and HIA with the least alteration from control after HIA.
The results indicate that potassium arrest alone is not as effective as
hypothermia in preventing ischemic injury, and the combination of
hypothermia with a single 150 cc administration of potassium (25 mEq/liter)
does not appear to provide significant additional protection.
