Can Exertional Rhabdomyolysis be Managed in an Ambulatory Setting?

Abstract

Background

Rhabdomyolysis is a condition caused by the breakdown of skeletal muscles, leading to the release of intracellular contents. It is characterised by the triad of myalgia, muscle weakness and myoglobinuria. Traditionally, patients with this condition are hospitalized for intravenous hydration and monitoring. The objective of our study is to determine alternative safe disposition options for this condition.

Method

We conducted a retrospective observational study of 90 patients with exertional rhabdomyolysis admitted to an acute short stay ward (under 24 hours) through the Emergency Department (ED) of a tertiary restructured hospital between December 2020 and January 2022. Rhabdomyolysis was defined as a creatine kinase (CK) level > 1,000 U/L. Data collected included the presence of risk factors, symptoms, and laboratory values at presentation. Outcomes included time to downtrend of CK count, new-onset renal function impairment, and duration to renal function impairment (if present).

Results

The majority of our study cohort were young and female (60/90, 67%), with a median age of 26 years. Most patients presented to the ED within 3 days of the triggering event (median: 3, interquartile range [IQR]: 2-3). All patients experienced muscle pain (90/90, 100%). At presentation, their potassium levels were normal (90/90, 100%; median: 4.0, IQR: 3.7–4.2). The majority had CK levels of > 20,000 U/L (82/90, 91%), abnormal liver function (90/90, 100%) and renal impairment (1/90, 1%). During admission to the short stay ward, one additional patient developed renal function impairment. CK peaked on days 4-5 after the triggering event, with a median downtrend time of 6 days (IQR: 5-9).

Conclusion

Patients with exertional rhabdomyolysis who have no risk factors and can maintain oral hydration can be managed in an ambulatory setting with regular follow-up. This disposition can reduce the use of hospital resources.

Introduction

Exertional rhabdomyolysis, also referred to as exercise-induced rhabdomyolysis, is a potentially life-threatening condition. It results from skeletal muscle damage with the release of intracellular toxins into the systemic circulation.¹

Rhabdomyolysis is characterised by the triad of my-algia, muscle weakness (presented as difficulty in walking in our cohort), and dark urine due to myoglobinuria. The commonly recommended criterion for diagnosing rhab-domyolysis is a creatine kinase (CK) level > 1,000 U/L or five times the upper limit of normal.³ In this study, we defined rhabdomyolysis as CK levels > 1,000 U/L.

Traditionally, these patients are hospitalized for intravenous hydration and monitoring.^1,2,4 However, we noted that most patients had positive outcomes with conservative management i.e., intravenous hy-dration and monitoring.^2,4 This prompted us to review the current practice of “hospitalization.”

We reviewed 90 patients at a tertiary hospi-tal who were admitted to an acute short stay ward through their emergency department (ED) with a diagnosis of exertional rhabdomyolysis. Our aim was to determine whether patients with exertional rhabdo-myolysis can be safely discharged from the ED.^1,4

Methods

We conducted a retrospective observational study of 90 patients who were admitted to an acute short stay ward through the ED (average 110,000 annual visits) with a diagnosis of exertional rhabdo-myolysis. The diagnosis of exertional rhabdomyolysis was defined as patients with symptoms of muscle pain, difficulty walking, dark coloured urine and elevated CK levels > 1,000 U/L. Patients who were transferred to other hospitals or discharged against medical advice were excluded.

Our patients were followed up from their pre-sentation at the ED to the resolution of rhabdomyoly-sis. We extracted demographic and disease-relevant data from the point of presentation at the ED until discharge from follow up. Anonymised data without any identifiers were drawn from an administrative database by a third party uninvolved with the study. We compared two disposition routes: direct discharge from the short stay ward versus admission to an inpa-tient ward and then discharge.

We also studied these outcomes:

1. Duration of downtrending of CK levels from their triggering events

2. The presence of new-onset renal function impair-ment (defined as a creatinine level > 112 µmol/L based on our local hospital laboratory criteria or above the baseline value for patients with pre-ex-isting chronic kidney disease)

3. Admission to high dependency (HD) or intensive care unit (ICU)

4. Dialysis

This study was reviewed and exempted from ethics review by the National Healthcare Group do-main specific review board (Institutional Review Board [IRB] number: 2024/00037).

Results

Our cohort consisted of 90 patients (Table 1). The majority of patients were young and female (60/90, 67%). The median age was 26 years (inter-quartile range [IQR]: 23–29). Four percent had under-lying risk factors: 1% (1/90) had history of previous rhabdomyolysis, 2% (2/90) had diabetes mellitus, 1% (1/90) had thyroid nodule.

Table 1. Cohort characteristics (N = 90).

Characteristics	Valuea
Age (years)	26 (23-29)
Gender
Female	60 (67)
Male	30 (33)
Risk factors
History of previous rhabdomyolysis	1 (1)
Diabetes Mellitus	2 (2)
Thyroid disorder	1 (1)
Days from triggering event to ED visit	3 (2-3)
Symptoms at ED visit
Muscle pain	90 (100)
Difficulty walking (n = 80; 10 missing)	78 (98)
Dark-coloured urine (n = 86; 4 missing)	71 (83)
Lab values at ED visit
Creatine kinase (U/L)	61,378 (39,066–82,235)
Creatinine (µmol/L) > 112	1 (1)
Alanine aminotransferase (U/L) > 30	89 (99)
Aspartate aminotransferase (U/L) > 42	90 (100)
Potassium (mmol/L)	4 (3.7–4.2)
Follow-up outcomes
Time to creatine kinase downturn (days)	6 (5-9)
Disposition: admitted	8 (9)

^aValues were present as number (%) or median (interquartile range). ED: emergency department; IQR: interquartile range.

The majority presented to the ED within 3 days from the triggering event, with a mean of 3.0 (standard deviation: 1.0) and a median of 3 days (IQR: 2-3). Muscle pain was the earliest and most common symp-tom (90/90, 100%).

At presentation, their potassium levels (90/90, 100%) were normal (median: 4.0, IQR: 3.7–4.2). The majority had CK of > 20,000 U/L (82/90, 91%), abnor-mal liver function (90/90, 100%) and renal function im-pairment (1/90, 1%). While in the short stay ward, one additional patient developed renal function impairment.

In this cohort, CK was noted to peak on days 4 to 5 after the triggering events. The average time for CK levels to downtrend was 6 days (IQR: 5-9 days) (Fig. 1). One patient at ED presentation had renal function impairment with CK of 48,946 U/L (day 2 from trig-gering event) and a creatinine of 113 µmol/L. He was discharged well on day 4 from triggering event with CK of 45,301 U/L and creatinine of 82 µmol/L. Another patient who developed renal function impairment while in the short stay ward had presented at the ED on day 3 after the triggering event, with a creatinine level of 60 µmol/L (CK: 106,500 U/L), but this climbed to 160 µmol/L the next day (CK: 118,190 U/L). He was then transferred to the inpatient ward and discharged well 4 days later (CK: 92,320 U/L).

Fig. 1. Creatine kinase levels among rhabdomyolysis patients according to days from triggering event.

Median CK levels for those with renal function impairment were 77,723 U/L (IQR: 63,335–92,112), compared to those without (median: 61,378 U/L, IQR: 38,689-81,725). There was no correlation between renal function impairment and CK levels (p = 0.47). Our cohort received 2 L of intravenous fluid (median) over 6.8 hours (median).

Eight patients were admitted to an inpatient ward (8/90, 8%). All presented within 5 days from their triggering event (spinning). The reasons for the admissions were development of renal function im-pairment, persistent or worsening of symptoms, and up-trending of CK. All of them were discharged well following an uneventful inpatient stay. None of them required dialysis, admission to HD, or ICU.

Discussion

Our cohort included mostly young (median age 26), fit patients with symptomatic rhabdomyolysis after intense physical exertion (mostly spinning).⁴ Median CK levels for the 90 patients admitted to the short stay unit were over 60,000 U/L. All had good outcomes with no permanent renal function impair-ment. Eight patients were admitted from the short stay ward to an inpatient ward, likely representing clinician (and/or patient) anxiety in the absence of established guidance to support early discharge. We suggest that ambulatory management (with close fol-low-up) be considered as the default in most patients with exertional rhabdomyolysis. This can reduce the use of hospital resources.

Cervellin et al.⁵ commented that 50% of their patients did not complain of muscle pain or weakness (2 of the 3 classic triad symptoms together with dark urine). However, the majority of our patients (100%) presented to the ED because of muscle pain or weak-ness.

We observed CK levels to peak on day 4 or 5 and start downtrending on day 6 after the triggering event. It has been noted that abnormal levels of CK can persist for a substantial amount of time in exer-tional rhabdomyolysis, as in our study.¹ The literature shows that CK half-life is approximately 36 hours.⁶ However, no analysis of the CK half-life was done in this study, as our data were not geared towards a pharmokinetics study. The time points were not at fixed intervals, and intervals between CK readings were not uniform.

Two patients in the cohort developed acute renal function impairment, i.e., one in the ED (CK, 48,946 U/L) and the other one in the short stay ward (CK, 106,500 U/L). Both were discharged uneventfully. An elevated CK is the diagnostic criterion for rhabdomy-olysis but was not predictive of renal function impair-ment in our study.

All our patients (100%) had raised alanine ami-notransferase (ALT) and aspartate aminotransferase (AST). Both enzymes are located not only in the liver but also in skeletal muscles and other organs (heart, kidneys, pancreas, erythrocytes). Rhabdomyolysis is one of the representative conditions in which serum aminotransferases are elevated without significant liv-er disease, and AST is usually higher than ALT, as ob-served in our results. Therefore, raised levels of these enzymes during rhabdomyolysis are not indicative of hepatocellular necrosis.⁴

Fluid replacement is the keystone of rhabdomy-olysis treatment. This can be done via the intrave-nous or oral route (if patient can tolerate it). However, patients receiving fluid replacement therapy should be monitored closely to prevent complications such as fluid overload and metabolic acidosis.

Disposition of patients who present to an ED with exertional rhabdomyolysis could include:

1. Fluid therapy during the ED visit followed by dis-charge to home with regular follow-up.

2. Admission to a short stay ward for treatment be-fore discharge to home with regular follow-up.

Based on our results, we postulate that patients with exertional rhabdomyolysis without risk factors who are able to take in oral hydration can be managed in an ambulatory setting with regular follow-up.

There is also an opportunity for patient educa-tion on appropriate hydration and the warning signs and symptoms of rhabdomyolysis in centralized loca-tions of high-demand activities. These warnings can then alert patients to seek medical evaluation.

Conclusion

Patients with exertional rhabdomyolysis who have no risk factors and can tolerate oral hydration can be managed in an ambulatory setting with regular follow-up instead of being admitted.