Cerebrospinal fluid acidosis complicating therapy of experimental cardiopulmonary arrest

Abstract

Cardiopulmonary resuscitation (CPR) may be followed by slow recovery of brain function. The possible role of bicarbonate therapy was assessed by analysis of arterial blood and cerebrospinal fluid (CSF) in 20 dogs during cardiac arrest and CPR. Samples were taken in the control period and every 5 minutes postarrest for 20 minutes. Group I received no postarrest CPR. Arterial pH fell from 7.37 to 7.31 (P < 0.01) and CSF pH from 7.34 to 6.94 (P < 0.001). Arterial pCO2 rose from 39 to 65 mm Hg (P < 0.005) and CSF pCO2 increased from 47 to 123 (P < 0.02). With CPR alone (group II) arterial pH decreased from 7.39 to 7.19 (P < 0.005), while arterial PCO2 and CSF pH and pCO2 were unchanged. CPR with bicarbonate therapy (mEq = weight in kg x 0.43 x 1.1 mEq/min of arrest) given every 5 minutes (group III), resulted in a rise in arterial pH from 7.41 to 7.81 (P < 0.02). Excess bicarbonate administration during CPR may result in a marked dissociation between arterial and CSF pH as a consequence of rapid CO2 diffusion across the blood brain barrier. Large amounts of NaHCO3 given during CPR may contribute to post CPR cerebral depression.