ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 25, No. 2 Copyright © 1995, Institute for Clinical Science, Inc.

Myoglobin Clearance as an Early Indicator for Rhabdomyolysis-Induced Acute Renal Failure*!

IOANNIS D. LAIOS, Ph.D., ROGER CARUK, M.T., and ALAN H. B. WU, Ph.D.

Department of Pathology and Laboratory Medicine, Hartford Hospital, Hartford, CT 06102

ABSTRACT

Two cases are described to illustrate the use of the myoglobin clearance rate as a predictor of acute renal failure (ARF). Both patients suffered exten­ sive skeletal muscle injury characterized by high total creatine kinase and urine myoglobin. In the first case, a high myoglobin clearance at admission (27 mL/min) was accompanied by normal serum creatinine and creatinine clearances. This patient recovered without renal complications. The sec­ ond case also had normal serum creatinine and creatinine clearances at the initial presentation of symptoms, but was accompanied by a very low myo­ globin clearance (0.64 mL/min). Within 48 h, this patient developed acute renal failure, with creatinine rising from 1.5 to 5.8 mg/dL, and creatinine clearance dropping from 270 to 2.8 mL/min. Because myoglobin has been recognized as a cause of ARF, these cases help illustrate how the myoglo­ bin clearance rate might be used in evaluating patients with rhabdomy- olysis for the development ARF.

Introduction released in the serum and excreted in the u rin e .2 ,3 Rhabdomyolysis, the massive Myoglobin is a low molecular weight breakdowr of skeletal muscle, is charac­ (17800 Da), oxygen-binding protein of terized by elevated concentrations of striated (cardiac and skeletal) muscle . 1 serum and urine myoglobin and Unlike hemoglobin, myoglobin is not increased activity of muscle enzymes able to release oxygen except at such as creatine kinase.4 Excessive myo­ extremely low p 0 2. After injury to skele­ globin in the serum may lead to acute tal or cardiac muscle, myoglobin is renal failure; however, it is unclear how myoglobin exerts its nephrotoxicity. Myoglobin clearance can be used for * Presented in part at the Spring Meeting of the predicting which patients with rhabdo­ Association of Clinical Scientists, Newport, RI, May myolysis will progress to renal failure .5 12-15, 1993. Prophylactic treatment includes adminis­ t Send reprint requests to: Alan H. B. Wu, Ph.D., Department of Pathology, Hartford Hospital, 80 tration of osmotic diuretics (mannitol) to Seymour St., Hartford, CT 06102-5037. maintain urine flow along with adminis­ 179 0091-7370/95/0300-0179 $00.90 © Institute for Clinical Science, Inc. 180 LAIOS, CARUK, AND WU tration of i.v. fluids for the appropriate Other results of the initial laboratory studies were as follows: sodium, 143 mmol/L; potassium, 4.6 volume replacement, and alkalinization mmol/L; chloride, 102 mmol/L; carbon dioxide, 29 of urine (with sodium bicarbonate) for mmol/L; creatinine, 1.3 mg/dL; blood urea nitro­ preventing myoglobin precipitation in gen, 30 mg/dL; glucose 123 mg/dL; ionized cal­ cium, 1.15 mmol/L; magnesium, 0.96 mmol/L; the renal tubules.6 phosphorus, 1.4 mmol/L; hematocrit, 40.3 percent; Two similar cases of acute rhabdo- white-cell count, 10400 celIs/|j.L; platelet count, myolysis are presented to illustrate the 326000 platelets/p-L; prothrombin time, 11.6 sec­ onds; partial-thromboplastin time, 23.4 seconds; use of myoglobin clearance as an early total bilirubin 1.0 mg/dL; aspartate aminotrans­ indicator for myoglobinuria-induced ferase, 854 U/L; alanine aminotransferase, 151 U/L; acute renal failure. In both cases, very alkaline phosphatase, 120 U/L; amylase, 46 U/L; and lipase, 198 U/L. high concentrations of serum and urine Treatment with furosemide (40 mg PO qd), allo- myoglobin concentrations were recov­ purinol (300 mg PO qd), and potassium chloride (40 ered. Despite prospective treatment in meq PO qd) was started. Intravenous fluids with both cases, renal failure developed in added sodium bicarbonate were administered. Two days after admission his urine output was 1800 mL case # 2 and was avoided in case # 1 . in 8 hours with a myoglobin clearance of 27.1 Calculations of myoglobin clearances mL/min and a creatinine clearance of 95 mL/min (table I). He was diagnosed with bilateral lower leg were made to determine the usefulness compartment syndrome (compromised circulation of myoglobin measurements in serum in the leg muscles); two days after admission he was and urine. operated on for bilateral fasciotomies (excision of fibrous tissues). Intraoperative findings include a question of muscle necrosis, but were otherwise Case #1 unremarkable. Postoperative course was uncompli­ cated with a decrease of serum myoglobin to 348 (ig/L and serum creatinine from 1.6 to 1.3 mg/dL A 77-year-old man was found at home unrespon­ (table I). On day 15, he was operated on for fasci- sive by a neighbor. He was brought in the Emer­ otomy closure; on day 30, he was discharged to a gency Department at Hartford Hospital with a nursing home to continue supportive care with serum myoglobin of 43,000 |xg/L, a creatine kinase physical therapy. of 53,569 U/L (table I), and a creatine kinase MB of 136 Jig/L (relative index <1 percent). He was admit­ ted with rhabdomyolysis and early cellulitis. The Case # 2 patient’s medical history included Parkinson’s dis­ ease, status post myocardial infarction and coronary artery bypass surgery in 1988, chronic obstructive A 32-year-old man was admitted to Hartford Hos­ pulmonary disease, congestive heart failure, benign pital with diagnosis of severe pancreatitis. He was prostatic hypertrophy, and gout. transferred there from the Institute of Living (men­

TABLEI

Laboratory Results for Case #1

Hours After ______Mvoqlobin (\ia/L)______Creatinine (mg/dL)____ CK Admission* Serum Urine Clearance* Serum Urine Clearance1’ (U/L)

0 43000 NA NA 1.3 NA NA 53569 11 30900 NA NA 1.2 NA NA 52360 41 15300 153000 27.1 1.6 56 95 52760 61 9780 185000 23.6 1.5 75 62 33960 85 5560 63500 14.3 1.4 67 60 20983 110 1590 11200 11 1.5 54 56 12587 132 617 1390 4.7 1.3 45 72 6265 156 348 <20 0.05 1.3 79 57 3273

•Admitted to medical intensive care unit. b In mL per minute over an 8-hour period. MYOGLOBIN CLEARANCE AND RHABDOMYOLYSIS-INDUCED ACUTE RENAL FAILURE 181

tal health facility), Hartford, CT, where he was after admission, following a night of agitation and enrolled in an alcohol rehabilitation program. He fighting restraints, he was found to be hypotensive, had a past medical history significant for depres­ tachypneic, diaphoretic with delirium tremens, and sion, alcohol abuse, and delirium tremens. Three had abnormal electrolytes (sodium, 160 mmol/L; weeks prior to admission he had myositis ossificans potassium, 3.3 mmol/L; ionized calcium, 1.34 after removal of left piriform muscle. mmol/L; magnesium, 1.49 mmol/L; chloride, 124 The results of the initial laboratory tests were as mmol/L). Creatine kinase and myoglobin were follows: sodium, 140 mmol/L; potassium, 3.8 increased, as shown in table II, with a serum cre­ mmol/L; chloride, 95 mmol/L; carbon dioxide, 28 atinine of 1.5 mg/dL and a blood urea nitrogen of mmol/L; creatinine, 0.7 mg/dL; blood urea nitro­ 32 mg/dL. gen, 9 mg/dL; glucose 92 mg/dL; ionized calcium, The patient was transferred to MICU because of 1.23 mmol/L; magnesium, 0.86 mmol/L; phospho­ acute respiratory and cardiovascular deterioration. rus, 1.2 mmol/L; hematocrit, 38 percent; white-cell He was diagnosed with sepsis syndrome, hypox­ count, 6200 cells/|xL; platelet count, 182000 plate- emic respiratory failure, and rhabdomyolysis for Iets/|xL; prothrombin time, 11.8 seconds; partial- which he was treated with intravenous fluids with thromboplastin time, 34.4 seconds; total bilirubin added sodium bicarbonate. Arterial-blood gas val­ 1.0 mg/dL; amylase, 729 U/L; lipase, 13442 U/L; ues, measured while the patient was breathing aspartate aminotransferase, 91 U/L; alanine ami­ room air and after the administration of intravenous notransferase, 50 U/L; and alkaline phosphatase, fluids, revealed a pH of 7.44, a POz of 82 mm Hg, 82 U/L. and P C 0 2 of 19 mm Hg. Two days later the patient Patient was initially admitted to the medical developed acute renal failure secondary to rhabdo­ floor and treated with cimetidine (6 mL/hour of myolysis and was treated initially with furosemide 900 mg in 150 mL normal saline), lorazepam (1 to 2 (200 mg at 4 mg/hour) and then mannitol (20 per­ mg intravenous q4h), meperidine (25 to 50 mg intra­ cent at 50 mL/hour). Urine output decreased from venous q4h), and intravenous fluids with added 620 mL in 8 hours to 465 mL in 8 hours, and man­ potassium chloride. His pancreatitis improved, nitol was discontinued 24 hours later to avoid accu­ but he required larger and larger dosage for with­ mulation. Serum osmolality values in that time drawal symptoms. period (table II, 0 to 63 hours after admission to Two days after admission the patient wanted to MICU) ranged from 324 to 338 mOsm/kg. go home; however, because he was suicidal, the Seven days after admission (table II, 63 hours attending physician would not discharge him. after admission to MICU), the patient was put on Patient became very agitated and disoriented, had hemodialysis for three hours, and continued on to be restrained, and was given sedatives. Four days hemodialysis every other day for a week. Urine out-

TABLE II

Laboratory Results for Case #3

Hours After ______Mvoalobin (\ia/L)______Creatinine (mg/dL) CK Admission3 Serum Urine Clearanceb Serum Urine Clearance1’ (U/L)

0 26800 16500 0.64° 1.5 387 269.5 ° 41960 14 46300 102000 2.85 2.8 43 19.8 310400 51 80400 141000 1.70 5.8 17 2.8 179500 63 96900 140000 1.45 6.5 15 2.3 114110 78 46400 134000 1.98 6.5 20 2.1 93300 110 50000 119000 2.48 6.2 19 3.2 73750 160 33400 92400 1.67 7.8 29 2.2 46841 194 12600 44100 1.18 6.1 33 1.8 23557 278 4210 14500 0.90 7.0 65 2.4 4027 412 2070 5340 0.50 3.9 85 4.1 376 470 1030 5160 0.99 2.9 65 4.4 314 495 940 140 0.04 3.0 83 7.9 325 784 243 N/A N/A 2.4 N/A N/A 137 856 537 < 2 0 0.07 1.4 38 48.6 436

a Admitted to medical intensive care unit. b In mL per minute over an 8-hour period. c In mL per minute over a 3-hour period. 182 LAIOS, CARUK, AND WU put continued to decrease and three weeks after ence range was estimated for myoglobin admission reached the lowest volume of 93 mL in 8 hours with a creatinine clearance of 4.1 mL/min clearance of 0—0.2 mL/min. It has been (table II, 412 hours after admission to MICU). The previously determined that a cutoff of 4.0 patient’s condition after that point slowly improved mL/min is significant for development of and at the end of the fifth week his urine volume was 850 mL in 8 hours with a serum myoglobin of a rhabdomyolysis-induced acute renal 537 jJLg/L and a serum creatinine of 1.4 mg/dL (table failure.5 II, last row). After an 11-week hospital stay requir­ Serum creatinine and creatine kinase ing intensive rehabilitation and aggressive physical therapy, the patient was discharged to another hos­ (CK) were measured on an Ektachem pital for chronic rehabilitation and continuous med­ 700t and urine creatinine on a Cobas ical management. Fara.t The male reference ranges for serum creatinine, creatinine clearance, Experimental and CK were 0.7 to 1.7 mg/dL, 97 to 137 mL/min/1.73 m2, and 0 to 230 U/L, Quantitative determinations of myo­ respectively. Because both men were of globin were performed on an Opus Plus,* average size and weight, creatinine clear­ which is a nonisotopic, fluorogenic ances were calculated without correc­ enzyme sandwich immunoassay. The tions to body surface area. capture antibody is a monoclonal anti­ First-order rate constants for the body linked to glass fiber, while the sec­ elimination of serum myoglobin were ond antibody is polyclonal and conju­ calculated by fitting a first-order model gated to alkaline phosphatase. The to the data with a multiple-linear- enzyme acts on the substrate (4-methyl regression method .7 umbelliferyl phosphate) to produce a fluorescent product. The initial rate of Results and Discussion fluorescence increase is proportional to It has recently been suggested by us the myoglobin concentration. The manu­ that in patients with rhabdomyolysis, the facturer’s recommendations were fol­ myoglobin clearance rate was a risk factor lowed for the serum assays and the same for development of acute renal failure .5 methodology adopted for urine speci­ Patients who have serum myoglobin con­ mens as well. Myoglobin is stable in centrations exceeding 400 (xg/L and myo­ serum samples for at least one month globin clearance rate of <4 mL/min were when stored at 2 to 8 °C. Myoglobin in at greatest risk for this complication. In urine samples with an acidic pH the cases presented in this report, equiva­ degrades within a few days; therefore, lently high concentrations of urine myo­ urine samples should be either analyzed globin were obtained in both cases. How­ immediately or alkalinized before stor­ ever, differences in serum myoglobin age at 2 to 8 °C. The reference ranges for concentrations and urine volume pro­ serum and urine myoglobin were 8 to 6 6 duce different myoglobin clearance cal­ and 0 to 7 |xg/L, respectively .5 The refer­ culations, which may have contributed to ence range for myoglobin clearance was different clinical outcomes. not computed because myoglobin con­ In case #1, very high serum and urine centrations in urine are normally below myoglobin concentrations were obtained the sensitivity of the immunoassays. Nev­ (table I). High myoglobin clearance rates ertheless, using the reference range for ranging from 11 to 27 mL/min during the serum and urine myoglobin and assum­ first few days after admission were seen ing a normal 24-h urine volume, a refer­

t Eastman Kodak, Rochester, NY. * Behring Diagnostics, Westwood, MA. t Roche Diagnostics, Nutley, NJ. MYOGLOBIN CLEARANCE AND RHABDOMYOLYSIS-INDUCED ACUTE RENAL FAILURE 183

because urine values were some 1 0 -fold creatinine from skeletal muscle trauma. higher than the serum concentrations. However, the low myoglobin clearance Serum creatinine concentrations were rate of 0.64 mL/min indicated that this within the upper limits of normal patient was at high risk for acute renal throughout the initial period of admis­ failure, a complication that subsequently sion, and this patient did not suffer any developed some 48 hours later, when renal impairment. Myoglobin clearances serum creatinine concentrations rose to returned to low values within a week. 5.8 mg/dL, creatinine clearance dropped In case #2, although equally high to 2.8 mL/min (table II), and blood urea urine myoglobin concentrations were nitrogen concentration increased to 63 observed, serum myoglobin concentra­ mg/dL. It is our suggestion that in this tions were disproportionately high, case, an accumulation of myoglobin, as resulting in myoglobin clearance values reflected by the low clearance rate, con­ that were all below the 4.0 mL/min cut­ tributed to the acute renal failure off. The significant part of this case was observed. Prospective knowledge of that at admission to the MICU, this potential risk for acute kidney failure in patient had no clinical or laboratory signs this patient could prompt more aggres­ of renal dysfunction (except for a blood sive therapies that may lead to minimiza­ urea nitrogen of 32 mg/dL) with a serum tion and possibly avoidance of renal fail­ creatinine of 1.5 mg/dL, a urine creati­ ure. nine of 387 mg/dL, and a urine output of These cases illustrate the utility of 188 mL in a 3-hour period that resulted in myoglobin clearance measurements. a creatinine clearance of 269.5 mL/min. Qualitative dipstick analysis, which has a The high urine creatinine could be due sensitivity of about 1000 jxg/L, would to increased glomerular filtration and provide no prognostic information, as tubular secretion after the administration results would have been positive on all of diuretics and intravenous fluids, and urine samples from both patients during may also reflect release and excretion of the first week after admission. Moreover,

F i g u r e 1. E x p e ri­ mental (■, A) and fitted (solid lines) data using a first-order model for serum myoglobin vs time. (■): Case #1, ti/2 = 29 h. (k): Case #2, ti/2 = 53 h.

Time after admission (hours) 184 LAIOS, CARUK, AND WU creatine kinase levels, which established References the diagnosis of rhabdomyolysis in these patients, were not useful in predicting 1. Hamilton RW, Hopkins MB, Shihabi ZK. Myo­ globinuria, hemoglobinuria, and acute renal renal failure. The ability to clear myoglo­ failure. Clin Chem 1989;35:1713-20. bin is the critical factor in prediction of 2. Gabow PA, Kaehny WD, Kelleher SP. The acute renal failure, because myoglobin spectrum of rhabdomyolysis. Medicine 1982; can obstruct tubular blood flow and is 61:141-9. 3. Gibler BW, Gibler CD, Weinshenker E, et al. directly toxic to renal tubules. Myoglobin as an early indicator of acute myocar­ To demonstrate further the impaired dial infarction. Ann Emerg Med 1987;16:851-6. myoglobin clearance rate in case #2, the 4. Harper J. Rhabdomyolysis and myoglobinuric first-order rate constant was calculated renal failure. Crit Care Nurse 1992;10:32-6. 5. Wu AHB, Laios I, G reen S, et al. Immunoassays for the elimination of serum myoglobin, for serum and urine myoglobin: myoglobin and results compared to a case of good clearance assessed as a risk factor for acute myoglobin clearance. As shown in figure renal failure. Clin Chem 1994;40:796-802. 6. Eneas JF, Schoefeld PY, Humphreys MH. The 1 , the half-life for case # 2 was consider­ effect of infusion of mannitol-sodium bicarbon­ ably prolonged compared to case #1. The ate on the clinical course of myoglobinuria. onset of acute renal failure further poten­ Arch Intern Med 1979;139:801-5. tiates the effect of high serum myoglobin 7. Love MD, Pardue HL, Pagan G. Evaluation of transient responses of ammonia-selective concentrations, as this is the only major potentiometric electrodes for quantitative mechanism for its clearance. applications. Anal Chem 1992;64:1269-76.