Objective To compare the outcomes of patients with and without a mean serum potassium (K+) level within the recommended range (3.5–4.5 mEq/L). Methods This prospective cohort study involved patients admitted to the medical intensive care unit (ICU) of Siriraj Hospital from May 2012 to February 2013. The patients’ baseline characteristics, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, serum K+ level, and hospital outcomes were recorded. Patients with a mean K+ level of 3.5 to 4.5 mEq/L and with all individual K+ values of 3.0 to 5.0 mEq/L were allocated to the normal K+ group. The remaining patients were allocated to the abnormal K+ group. Results In total, 160 patients were included. Their mean age was 59.3±18.3 years, and their mean APACHE II score was 21.8±14.0. The normal K+ group comprised 74 (46.3%) patients. The abnormal K+ group had a significantly higher mean APACHE II score, proportion of coronary artery disease, and rate of vasopressor treatment. An abnormal serum K+ level was associated with significantly higher ICU mortality and incidence of ventricular fibrillation. Conclusion Critically ill patients with abnormal K+ levels had a higher incidence of ventricular arrhythmia and ICU mortality than patients with normal K+ levels.
Background: “Rules of thumb” for the replacement of electrolytes, including magnesium, in critical care settings are used, despite minimal empirical validation of their ability to achieve a target serum concentration. This study’s purpose was to evaluate the effectiveness and safety surrounding magnesium replacement in medically, critically ill patients with mild-to-moderate hypomagnesemia. Methods: This was a single-center, retrospective, observational evaluation of episodes of intravenous magnesium replacement ordered for patients with mild-to-moderate hypomagnesemia (1.0-1.9 mEq/L) admitted to a medical intensive care unit from May 2014 to April 2016. The primary effectiveness outcome, achievement of target serum magnesium concentration (≥2 mEq/L) compared to expected achievement using a “rule of thumb” estimation that 1 g intravenous magnesium sulfate raises the magnesium concentration 0.15 mEq/L, was tested using 1-sample z test. Logistic regression analysis was conducted to assess the effect of infusion rate on target achievement. Results: Of 152 days on which magnesium replacements were provided for 72 patients, a follow-up serum magnesium concentration was checked within 24 hours in 89 (58.6%) episodes. Of these 89 episodes, serum magnesium concentration reached target in only 49 (59.8%) episodes compared to an expected 89 (100%; P < .0001). There was no significant association between infusion rate and achievement of the target serum magnesium concentration (odds ratio: 0.962, 95% confidence interval: 0.411-2.256). Conclusions: Medically, critically ill patients who received nonprotocolized magnesium replacement achieved the target serum magnesium concentration less frequently than the “rule of thumb” estimation predicted.