Serum potassium (K+) levels outside the standard range of 3.5 to 5.0 mmol/L are associated with increased risk of cardiac arrhythmias.1–6 Significant hypokalemia is associated with Q-T interval prolongation and subsequent risk of ventricular fibrillation,7,8 while significant hyperkalemia is associated with peaked T waves and widened QRS complexes with subsequent risk for bradycardia and asystole.9,10 As such, both hypo- and hyperkalemic states can put patients at risk for sudden cardiac death.11,12 Patients with acute illness are at risk for K+ imbalance and cardiac arrhythmias.13–17 Mobility, activities of daily living, and exercise are frequently initiated by physical therapists (PTs) and occupational therapists (OTs) during hospitalization.18,19 An exhaustive search of recent literature via PubMed did not provide clear guidelines or identify specific suggested values for K+ in regard to safe provision of PT and OT service and/or mobilization of patients in an acute care setting; however, the American Physical Therapy Association's Academy of Acute Care provided a resource suggesting a symptom-based approach for treating patients with variable serum K+ levels.20,21 The current standard of practice at Henry Ford Hospital allows for provision of PT and OT interventions for patients with K+ levels of 3.1 to 5.9 mmol/L and is based on expert recommendations from the cardiology and nephrology departments within the institution and is included in the rehabilitation department's laboratory values competency manual.22 No serious adverse events in the treatment of these patients have been reported in greater than 10 years. However, there is a lack of compelling literature to demonstrate that PT and OT interventions pose no significant threat to this patient population. This study was designed to verify and validate our facility's guidelines that patients with serum K+ concentrations of 3.1 to 5.9 mmol/L can participate safely in acute PT and OT interventions without serious adverse events to ensure that all eligible patients receive rehabilitation (rehab) services when necessary and appropriate and to provide evidence that is critically lacking in the literature.
All patients admitted to Henry Ford Hospital with serum K+ levels of 3.1 to 5.9 mmol/L were eligible for inclusion in this study. Exclusion criteria omitted individuals with potassium levels of 3.0 mmol/L or less and 6.0 mmol/L or greater, as well as individuals who did not meet the specified guidelines for vital signs, hemoglobin, platelets, blood glucose, and troponin values outlined by the Henry Ford Hospital Rehab Services Lab Values Competency and Reference Manual as listed in Table 1.21,22 Those eligible to participate in the study were required to have heart rate and blood pressure monitored pre-, mid-, and post-treatment and documented in the daily therapy note.20–23 For the purposes of this project, abnormal K+ was subdivided into 2 groups: hypokalemia defined as K+ levels of 3.1 to 3.4 mmol/L, and hyperkalemia defined as K+ levels of 5.1 to 5.9 mmol/L. Normal K+ levels were defined as 3.5 to 5.0 mmol/L. Standard PT and OT services were defined as “interventions designed to address patient-specific impairments in musculoskeletal, neuromuscular, integumentary, cardiovascular, pulmonary, and/or cognitive systems causing limitations in mobility or restrictions in activities of daily living.” Treatment was terminated with onset or increase in any symptoms outlined in Table 1. Demographics collected included the following comorbidities: coronary artery disease, end-stage renal disease, chronic kidney disease, acute kidney injury, atrial fibrillation, hypertension, congestive heart failure, and chronic obstructive pulmonary disease. These were chosen to reflect the comorbidities most commonly associated with altered potassium levels and/or those frequently associated with electrolyte imbalance. The therapist also recorded the subject's hospital unit (differentiated by patient population, intensive care unit, general practice unit, and telemetry). These demographics and adverse outcomes were compared between subjects with normal K+ levels and those with hypo- or hyperkalemia. This study was approved by the Henry Ford Health System Institutional Review Board.
All data were categorical and presented as count and column percentages. Bivariate analyses were carried out using a 2 × 2 χ2 or Fisher exact test if an expected cell count was less than 5 and included K+ (normal/abnormal) versus the presence of each comorbidity, K+ (normal/abnormal) versus occurrence of each adverse event, and K+ (normal/abnormal) versus need for termination of treatment. Statistical significance was set at P < .05. All analyses were performed using SAS 9.4 (SAS Institute Inc, Cary, North Carolina).
A total of 380 subjects were enrolled in this study, including 68 subjects in intensive care units, 254 subjects in general practice units, and 58 subjects in a cardiology telemetry unit. The association between comorbidities and K+ is provided in Table 2. Thirty-seven percent of participants (n = 140) had abnormal K+ levels at the time of PT or OT intervention. Sixty-three percent of participants (n = 240) had normal K+ levels at the time of PT or OT intervention. Hypokalemia was present in 97 (26%) patient cases and hyperkalemia was present in 43 (11%) patient cases. No serious adverse events occurred in any study participant with normal or abnormal K+ levels. Minor adverse events occurred in 48 subjects. As expected, no adverse events occurred when highest level of mobility achieved was “nothing,” “sitting edge of bed,” or “marching in place.” During interventions that included “transfer from bed to chair,” 7 subjects experienced dyspnea and 1 subject experienced tachycardia. Two episodes of dyspnea were reported in subjects who achieved “standing” but not “marching in place.” Termination of intervention due to minor adverse events occurred in 8 (2%) subject cases. Significantly, all treatment sessions requiring termination were in the normal K+ group (n = 8, 3%) as compared with subjects with abnormal K+ (n = 0, 0%) (P = .029). Dyspnea was the only minor adverse event significantly higher in the group with abnormal K+ levels (n = 19, 14%) than in the group with normal K+ levels (n = 16, 7%) (P = .028). End-stage renal disease (P = .001) and hypertension (P = .024) were comorbidities found significantly higher in the abnormal K+ group. An analysis of the differences in K+ levels between units was completed and reported in Table 2; however, P values could not be determined because the number of categories exceeded the limits of the statistical analysis. Serious adverse events were defined as “deaths or cardiopulmonary arrests requiring resuscitation during a PT or OT session.” Minor adverse events were defined as “undesirable, but non-life threatening, physiologic signs or symptoms during a PT or OT session.” No serious adverse events were recorded in any group. Fifty-four subjects were reported to have at least 1 minor outcome (63 outcomes in total), but overall rates did not differ significantly between normal (n = 37, 15.5%) and abnormal K+ (n = 26, 16.4%) groups. However, a greater rate of PT or OT session termination due to minor adverse events occurred in the normal K+ group than in the groups with hyperkalemia (n = 12, 25.6%), hypokalemia (n = 14, 12.4%), and normokalemia (n = 37, 15.5%). Rates of adverse event by K+ strata are shown in Table 3. Highest level of mobility achieved by K+ strata is shown in Table 4.
The results of this study support the safe initiation of rehabilitation interventions for patients with serum K+ levels of 3.1 to 5.9 mmol/L. No subjects included in this study experienced any serious adverse events. Rates of minor adverse events did not differ significantly between normal and abnormal K+ groups; however, the specific cause for these events based on the data collected could not be determined.
Literature supports the association between abnormal serum K+ levels and increased risk for cardiac events.1,5,12,17 With increased myocardial demand brought about by increased activity level, K+ concentrations should be a significant consideration for PTs and OTs when making clinical decisions about whether to initiate therapeutic intervention.18 As far as we have found, this is the first study of its kind to investigate particular K+ levels at which initiation of PT and OT services is safe. It was designed with the intention that all patients who have potential to benefit from PT and OT interventions receive appropriate treatments at appropriate times. We were aware that telemetry monitoring is not routinely used for all patients in an acute care setting with abnormal K+ levels who may be at risk for developing arrhythmias. To address this concern, the subjects were monitored for signs and symptoms of arrhythmia (dizziness, dyspnea, blurred vision, significant change in heart rate or blood pressure, anginal pain, paresthesia, and nausea/vomiting),18,20–22 and data from these patients were included. Age, gender, and acuity-level demographics were not collected for this group of participants, and analysis of these statistics is suggested for future research.
Individuals included in this study were noted to have a wide variety of comorbidities, and the effect and interaction between comorbidities in relation to serum K+ levels could not be determined. Rates of these minor adverse events did not appear to be related to the difference between serum K+ concentrations in this sample population. The effect of specific comorbidities on K+ levels is not well understood in relation to activity and possible risk for developing potentially dangerous arrhythmias. Specific levels of mobility for patients with K+ in specific ranges have not been studied. Further research is needed to determine the most appropriate guidelines for the provision of PT and OT intervention for patients with specific diagnoses and at differing exercise intensities in a population with varying K+ levels.
Comprehensive patient demographics were not collected for this subject sample, which limits the ability of the results of the study to be generalized. Telemetry monitoring was not available for all subjects, which required the researchers to rely on vital signs and symptoms for the detection of onset of new arrhythmia. Timing of blood draws and laboratory analysis of serum potassium levels was not accounted for in relation to potential electrolyte-balancing intervention (ie, intravenous administration of supplemental K+ or provision of sodium polystyrene sulfonate/Kayexalate) and PT or OT intervention. It is possible that the low rate of adverse events was confounded by the patient selection criteria. As acute care clinicians are already aware, the practicality of providing intervention only for patients who would meet the exclusion criteria for this study is not always realistic. This may warrant investigation of the safety of PT and OT intervention for patients with abnormal K+ and stable hypo-/hypertension, and/or tachy-/bradycardia in future research.
This study suggests that PT and OT intervention in patients with serum K+ levels of 3.1 to 5.9 mmol/L is safe. Subjects in an acute care setting, with and without telemetry monitoring, participated in therapeutic activities without any serious adverse events. Patients with K+ levels of 3.1 to 5.9 mmol/L should not be excluded from receiving PT or OT services based solely on concern for cardiac arrhythmias related to this laboratory value.
The authors acknowledge Connie J. Kittleson, DPT, for study concept collaboration and the Department of Rehabilitation Services at Henry Ford Hospital for data collection.
1. Fisch C, Knoebel SB, Feigenbaum H, Greenspan K. Potassium and the monophasic action potential, electrocardiogram, conduction and arrhythmias. Prog Cardiovasc Dis. 1966;8:387–418.
2. Gettes L, Surawicz B. Effects of low and high concentrations of potassium on the simultaneously recorded Purkinje and ventricular action potentials of the perfused pig moderator band. Circ Res. 1968;23(6):717–729.
3. Surawicz B, Lepeschkin E. The electrocardiographic pattern of hypopotassaemia with and without hypokalemia. Circulation. 1953;8:801–810.
4. Grandi E, Sanguinetti MC, Bartos DC, et al Potassium channels in the heart: structure, function, and regulation. J Physiol. 2017;595(7):2209–2228.
5. Nicoll D, Lu C, Pignone M, McPhee S. Pocket Guide to Diagnostic Tests. 6th ed. New York, NY: McGraw-Hill; 2012.
6. Porter RS. The Merck Manual of Diagnosis and Therapy. 19th ed. Rahway, NJ: Merck; 2011.
7. Widimsky P. Hypokalemia and the heart. E-J ESC Council Cardiology Pract. 2008;7:9–12.
8. Macdonald JE, Struthers AD. What is the optimal serum potassium level in cardiovascular patients? J Am Coll Cardiol. 2004;43(2):155–161.
10. Ettinger PO, Regan TJ, Oldewurtel HA. Hyperkalemia, cardiac conduction, and the electrocardiogram: a review. Am Heart J. 1974;88(3):360–371.
11. Schulman M, Narins RG. Hypokalemia and cardiovascular disease. Am J Cardiol. 1990;65(10):4E–9E; discussion 22E-23E.
12. Gettes LS, Surawicz B, Kim KH. Role of myocardial K and Ca in initiation and inhibition of ventricular fibrillation. Am J Physiol. 1966;211(3):699–702.
13. Goyal A, Spertus JA, Gosch K, et al Serum potassium levels and mortality in acute myocardial infarction. JAMA. 2012;307(2):157–164.
14. Whar JA, Parks R, Boisvert D, et al Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. JAMA. 1999;281(23):2203–2210.
15. Cohen HW, Madhavan S, Alderman MH. High and low serum potassium associated with cardiovascular events in diuretic-treated patients. J Hypertens. 2001;19(7):1315–1323.
16. Mattsson N, Sadjadieh G, Kumarathurai P, Nielsen OW, Køber L, Sajadieh A. Ambulatory cardiac arrhythmias in relation to mild hypokalaemia and prognosis in community dwelling middle-aged and elderly subjects. Europace. 2016;18(4):585–591.
17. Patel RB, Tannenbaum S, Viana-Tejedor A, et al Serum potassium levels, cardiac arrhythmias, and mortality following non-ST-elevation myocardial infarction or unstable angina: insights from MERLIN-TIMI 36. Eur Heart J Acute Cardiovasc Care. 2017;6(1):18–25.
18. Pawlik AJ, Kress JP. Issues affecting the delivery of physical therapy services for individuals with critical illness. Phys Ther. 2013;93(2):256–265.
19. Vollman KM. Understanding critically ill patients hemodynamic response to mobilization: using the evidence to make it safe and feasible. Crit Care Nurs Q. 2013;36(1):17–27.
22. Henry Ford Hospital Department of Rehabilitation Services. Laboratory Values Manual. Detroit, MI: Henry Ford Hospital; 2017.
23. Lundberg G. It is time to extend the laboratory critical (panic) value system to include vital values. Med Gen Med. 2007;9(1):20.