We included K + as a continuous variable in this model. The relationship of the K + value to an ECG with “any abnormality suggestive of hyperkalemia” and to short-term adverse events was determined using binary logistic regression. We analyzed each variable separately and calculated relative risk (RR). Fisher’s exact test was used for analysis involving less than five events. Data Analysisįor the association of short-term adverse events with specific ECG abnormalities, we used the Pearson chi-square statistic. Calcium chloride or gluconate administered solely for asymptomatic bradycardia, an abnormal ECG or high potassium value was not recorded as an adverse event. Symptomatic bradycardia was defined as bradycardia requiring treatment with calcium chloride, calcium gluconate, atropine, epinephrine, dopamine and/or pacing for symptoms of hypotension, syncope, chest pain, dyspnea and/or altered mental status. We defined an adverse event as symptomatic bradycardia, ventricular tachycardia, ventricular fibrillation, cardiopulmonary resuscitation (CPR) and/or death. The presence or absence of an adverse event within six hours of the laboratory measurement of a K + ≥6.5 mEq/L (regardless of treatment status) was determined. We categorized ECGs as having “any abnormality suggestive of hyperkalemia” if one or more of the following were present: (1) peaked T waves (2) PR prolongation (3) QRS prolongation (4) bradycardia (HR<50 bpm) (5) 2 nd or 3 rd degree heart block (6) junctional rhythm (7) ventricular escape rhythm or (8) ventricular tachycardia. In the scenario where the ECG reviewers disagreed on the rhythm, type of intraventricular conduction delay, or whether T waves were peaked or not, then we used the attending cardiologist reading. Similarly, we categorized the ECG as “QRS prolongation” if the QRS duration was >110 ms, and either there was no previous ECG for comparison or the QRS duration was 110 ms, then the ECG was categorized as “QRS prolongation” if the current QRS duration was longer than the previous QRS duration. An increased likelihood of short-term adverse event was found for hyperkalemic patients whose ECG demonstrated QRS prolongation (relative risk 4.74, 95% CI ), bradycardia (HR200 ms, and either there was no previous ECG for comparison or the PR interval was 200 ms, then the ECG was categorized as “PR prolongation” if the current PR interval was longer than the previous PR interval. All patients who had a short-term adverse event had a preceding ECG that demonstrated at least one hyperkalemic abnormality (100%, 95% confidence interval ). All adverse events occurred prior to treatment with calcium and all but one occurred prior to K +-lowering intervention. Adverse events occurred within six hours in 28 patients (15%): symptomatic bradycardia (n=22), death (n=4), ventricular tachycardia (n=2) and CPR (n=2). We included a total of 188 patients with severe hyperkalemia in the final study group. Relative risk was calculated to determine the association between specific hyperkalemic ECG abnormalities and short-term adverse events. Two emergency physicians blinded to study objective independently examined each ECG for rate, rhythm, peaked T wave, PR interval duration and QRS complex duration. We defined adverse events as symptomatic bradycardia, ventricular tachycardia, ventricular fibrillation, cardiopulmonary resuscitation (CPR) and/or death. A chart review identified patient demographics, concurrent laboratory values, ECG within one hour of K+ measurement, treatments and occurrence of adverse events within six hours of ECG. We collected records of all adult patients with potassium (K+) ≥6.5 mEq/L in the hospital laboratory database from August 15, 2010, through January 30, 2015.
This study analyzes the association between specific hyperkalemic ECG abnormalities and the development of short-term adverse events in patients with severe hyperkalemia.
However, there is a paucity of evidence to support this practice. The electrocardiogram (ECG) is often used to identify which hyperkalemic patients are at risk for adverse events.
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