A study of serum and myocardial digitoxin concentrations in man during cardiac arrest.
In 22 digitalized (of a total of 39) patients studied at random by radioimmunoassay during cardiac arrest, the mean serum digoxin concentration was 2.6 (+/- 1.86, range 0.6-8.2) ng/ml, significantly higher (P less than 0.001) than the "eudigitalized" concentration (1.3 +/- 0.52, range 0.5-2.3 ng/ml) determined under carefully standardized conditions in a non-toxic population. Half of the arrest patients had serum digoxin levels in the toxic range (2.4 ng/ml or above), mainly due to significant renal failure (mean serum creatinine concentration 2.9 +/- 2.66 v. 1 +/- 0.26 mg/dl for non-toxic subjects, P less than 0.001), partly due to a higher mean daily digoxin dose (0.40 v 0.31 mg/day, P less than 0.05) and frequently associated with potent diuretic therapy (73 v 54%). A smaller fraction of digitalized patients survived, both short- (27%) and long-term (14%), than did non-digitalized subjects (35% and 26%, respectively). The mean myocardial digoxin concentration was 150 (+/- 63.3, range 52-252) ng/g with an average myocardial/serum ratio of 62.5 (range 38-91). There were significant positive correlations between the serum digoxin and left-ventricular myocardial digoxin concentration (r=0.8107, P less than 0.01) or serum creatinine concentration (r=0.4637, P less than 0.001).