Some of the changes associated with electrolyte abnormalities are universal to critically ill patients, underscoring the importance of ECG monitoring in the ICU to identify issues early on and move patients toward the appropriate treatment.
Electrolyte Abnormalities on ECG
Symptoms related to electrolyte imbalance are often vague, but ECG findings can provide a means of early detection, as an educational resource from the Clerkship Directors in Emergency Medicine explains.2 ECG can indicate potential electrolyte derangements even before lab results are returned—from the tall, peaked T waves most visible in the precordial leads in early hyperkalemia, to the T-wave inversions that can progress into a prolonged QTc and mild ST depression with progressive degrees of hypokalemia, to the shortening of the QT interval typical of hypercalcemia.
In addition, according to ARUP Consult, hypocalcemia prolongs the QT interval.3 Severe hypercalcemia and severe hypermagnesemia can induce heart block and possibly cardiac arrest, and hypomagnesemia has been associated with widening QRS or QT, peaked T waves, and premature ventricular contractions. Moreover, both hypercalcemia and hypokalemia can prolong the PR interval, and hyperkalemia correlates with a widening of the QRS and ventricular tachycardia.
Electrolyte disorders that lengthen the QT interval possibly will trigger the development of torsades de pointes.
Hypokalemia in the ICU Setting
As a StatPearls review article notes, electrolyte imbalance can occur in any critical illness of a systemic nature, including COVID-19, and these abnormalities can be arrhythmogenic.4 Patients with underlying cardiac disease are more vulnerable to the development of such arrhythmias.
Hypokalemia appears to be of particular concern for patients with COVID-19 due to the interaction of SARS-CoV-2 with the renin-angiotensin system. Additionally, hypokalemia can worsen glucose control in patients who have both diabetes and COVID-19, according to a review published in Diabetes & Metabolic Syndrome: Clinical Research & Reviews.5
A report from Wenzhou, China, in JAMA Network Open revealed that out of 175 patients who had been admitted with COVID-19 by February 15, 2020, 18% had severe hypokalemia, and 37% had nonsevere hypokalemia.6 Abnormal ECG findings were seen in 16% of patients with nonsevere hypokalemia and 48% of those with severe hypokalemia. Severity of hypokalemia was correlated with severity of COVID-19 illness, which could lead to longer hospital stays, more frequent usage of antiviral medications (such as lopinavir or ritonavir), and longer durations of PCR-positive results.
Another study, conducted in Italy and published in Clinical and Experimental Nephrology, confirmed the high frequency of hypokalemia, which was detected in 41% of patients who were hospitalized with COVID-19 but not transferred to the ICU.7 The authors recommend that "low potassium level should be supplemented . . . and a careful assessment of the ECG should be performed, especially in concomitance of potentially arrhythmogenic drugs."
Early in the pandemic, many patients with COVID-19 reported gastrointestinal signs and symptoms.8 These included abdominal pain, nausea/vomiting, diarrhea, and liver enzyme abnormalities. Patients with vomiting and/or diarrhea are at particular risk of electrolyte imbalance, which may be apparent on ECG at presentation. Careful consideration should be given to detection and correction of electrolytes in these patients.
COVID-19 may be associated with other electrolyte abnormalities as well. A study in Internal and Emergency Medicine showed that both hypokalemia and hyponatremia were more common among COVID-19 patients admitted to the emergency department.9
ECG for Cardiac Triage
As a review article in the NEJM states, the majority of patients in whom COVID-19 is suspected should have a baseline ECG performed upon presentation.10 In addition to detecting other cardiac complications with ECG manifestations, this baseline ECG can identify electrolyte deficiencies like hypokalemia, allowing for correction upon presentation. Laboratory testing should include a comprehensive metabolic panel and a complete blood count for all critically ill patients who are hospitalized, including those with COVID-19.
The use of diagnostic ECG is a long-established and powerful tool for assessing patients with a wide range of presentations. It can reveal myocardial ischemia and infarction, other forms of myocardial injury such as myocarditis or arrhythmias, and electrolyte abnormalities, among other conditions. Any of these ECG findings may be present in patients admitted with critical illnesses, including COVID-19. This emphasizes the importance of obtaining a baseline ECG in critically ill patients, such as those with COVID-19, and highlights the utility of ECG monitoring in the ICU for guideline-directed cardiac triage.
References:
1. Bangalore S, Sharma A, Slotwiner A, et al. ST-segment elevation in patients with COVID-19 – a case series. New England Journal of Medicine. June 2020; 382: 2478-2480. https://www.nejm.org/doi/full/10.1056/NEJMc2009020
2. Society for Academic Emergency Medicine. Electrolyte abnormalities. SAEM.org. https://www.saem.org/about-saem/academies-interest-groups-affiliates2/cdem/for-students/online-education/m3-curriculum/group-electrocardiogram-(ecg)-rhythm-recognition/electrolyte-abnormalities. Accessed April 28, 2022.
3. ARUP Consult. Life-threatening electrolyte abnormalities. ARUPConsult.com. https://arupconsult.com/content/electrolyte-abnormalities-life-threatening. Accessed April 28, 2022.
4. Basu-Ray I, et al. 2022 Jan 15. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. https://pubmed.ncbi.nlm.nih.gov/32310612/
5. Pal R, Bhadada SK. COVID-19 and diabetes mellitus: an unholy interaction of two pandemics. Diabetes & Metabolic Syndrome: Clinical Research & Reviews. August 2020; 14(4): 513-517. https://www.sciencedirect.com/science/article/pii/S1871402120301144
6. Chen D, Li X, Song Q, et al. Assessment of hypokalemia and clinical characteristics in patients with coronavirus disease 2019 in Wenzhou, China. JAMA Network Open. June 2020; 3(6): e2011122. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2767008
7. Alfano G, Ferrari A, Fontana F, et al. Hypokalemia in patients with COVID-19. Clinical and Experimental Nephrology. January 2021; 25: 401-409. https://link.springer.com/article/10.1007/s10157-020-01996-4
8. Sultan S, Altayar O, Siddique SM, et al. AGA Institute rapid review of the gastrointestinal and liver manifestations of COVID-19, meta-analysis of international data, and recommendations for the consultative management of patients with COVID-19. Gastroenterology. July 2020; 159(1): 320-334. https://www.gastrojournal.org/article/S0016-5085(20)30593-X/fulltext
9. De Carvalho H, Richard MC, Chouihed T, et al. Electrolyte imbalance in COVID-19 patients admitted to the emergency department: a case-control study. Internal and Emergency Medicine. January 2021; 16: 1945-1950. https://link.springer.com/article/10.1007/s11739-021-02632-z
10. Gandhi RT, Lynch JB, del Rio C. Mild or moderate COVID-19. New England Journal of Medicine. October 2020; 383: 1757-1766. https://www.nejm.org/doi/full/10.1056/NEJMcp2009249