No change in plasma potassium concentration during 10 minutes of apnoea: An observational study on potential organ donors.

BACKGROUND Acute acidosis can increase the plasma potassium concentration. However, data on the effects of acute respiratory acidosis on plasma potassium concentration are conflicting. This study aimed to determine whether acute respiratory acidosis induces an immediate increase in plasma potassium concentration. METHODS This observational study was conducted on participants undergoing apnoea testing prior to final radiological examination, registered in an internal quality registry at Oslo University Hospital between 25 April 2013 and 1 May 2020. A total of 124 donors were assessed for inclusion. Sixteen donors with blood glucose concentrations exceeding 10 mmol L-1 were excluded; finally, data from 108 donors were included in the study. The apnoea test, which is a standard neurological test performed in potential organ donors prior to radiological confirmation of ceased brain circulation, induces respiratory acidosis. The arterial plasma potassium concentration, pH and PaCO2 before and after the apnoea test were compared. Statistical analysis was conducted using the paired t test. RESULTS The pre-apnoea and post-apnoea mean plasma potassium concentrations were 3.79 (95% confidence intervals [CI] 3.70-3.87) and 3.79 mmol L-1 (95% CI 3.70-3.88), respectively. The mean difference was -0.002 mmol L-1 (95% CI -0.04 to 0.04); the difference was not significant. The pre-apnoea and post-apnoea mean pH were 7.39 and 7.21, respectively, and the mean difference was 0.175 (P < .01). The pre-apnoea and post-apnoea mean PaCO2 were 5.66 and 9.48 kPa, respectively, and the mean difference was -3.83 (P < .01). CONCLUSIONS Acute respiratory acidosis does not lead to rapid changes in plasma potassium concentration during apnoea testing in potential organ donors.