Electrolyte measurements during inhospital cardiopulmonary resuscitation

Although electrolyte levels are commonly determined during inhospital CPR, the clinical usefulness of these measurements is questionable. Electrolyte and digoxin levels were obtained from 99 patients during resuscitative efforts. Measurements were examined for association with pre and postarrest values, outcome from arrest, and presence or absence of refractory ventricular arrhythmias. While BUN and creatinine (Cr) values correlated closely with pre and postarrest levels (r2 greater than 50%), Na, K, and Ca measurements were less reflective (r2 less than 50%). When electrolyte levels obtained during CPR were correlated with outcome, linear regression showed a consistent trend for higher levels in patients who subsequently died (K p less than .001; Mg p less than .02; Na p less than .025; Ca p less than .02; BUN p less than .02; Cr p less than .025). Finally, among the 12 patients with documented refractory ventricular arrhythmias, there appeared to be little association with K, Mg, and digoxin abnormalities observed during resuscitative efforts. These results suggest that electrolyte levels during CPR are strongly affected by metabolic disturbances and therapeutic interventions, and consequently, the clinical usefulness of these measurements may be limited.