Context Although potassium is critical for normal
electrophysiology, the association between abnormal preoperative serum
potassium level and perioperative adverse events such as arrhythmias
has not been examined rigorously.
Objective To determine the prevalence of abnormal preoperative
serum potassium levels and whether such abnormal levels are associated
with adverse perioperative events.
Design and Setting Prospective, observational, case-control study
of data collected from 24 diverse US medical centers in a 2-year period
from September 1, 1991, to September 1, 1993.
Patients A total of 2402 patients (mean [SD] age, 65.1 [10.3]
years; 24% female) undergoing elective coronary artery bypass grafting
who were not enrolled in another protocol. The study population was
identified using systematic sampling of every nth patient, in
whichn was based on expected total number of procedures at
that center during the study period.
Main Outcome Measures Intraoperative and postoperative
arrhythmias, the need for cardiopulmonary resuscitation (CPR), cardiac
death, and death due to any cause prior to discharge, by preoperative
serum potassium level.
Results Perioperative arrhythmias occurred in 1290 (53.7%) of
2402 patients, with 238 patients (10.7%) having intraoperative
arrhythmias, 329 (13.7%) having postoperative nonatrial arrhythmias,
and 865 (36%) having postoperative atrial flutter or fibrillation. The
incidence of adverse outcomes was 3.6% for death, 2.0% for cardiac
death, and 3.5% for CPR. Serum potassium level less than 3.5 mmol/L
was a predictor of serious perioperative arrhythmia (odds ratio [OR],
2.2; 95% confidence interval [CI], 1.2-4.0), intraoperative
arrhythmia (OR, 2.0; 95% CI, 1.0-3.6), and postoperative atrial
fibrillation/flutter (OR, 1.7; 95% CI, 1.0-2.7), and these
relationships were unchanged after adjusting for confounders. The
significant univariate association between increased need for CPR and
serum potassium level less than 3.3 mmol/L (OR, 3.3; 95% CI, 1.2-9.5)
and greater than 5.2 mmol/L (OR, 3.0; 95% CI, 1.1-8.7) became
nonsignificant after adjusting for confounders.
Conclusions Perioperative arrhythmia and the need for CPR
increased as preoperative serum potassium level decreased below 3.5
mmol/L. Although interventional trials are required to determine
whether preoperative intervention mitigates these adverse associations,
preoperative repletion is low cost and low risk, and our data suggest
that screening and repletion be considered in patients scheduled for