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Hemolytic uremic syndrome is a complex disease that impacts multiple body systems. Knowledge gained from cases has increased understanding of etiologic factors, presenting symptoms, diagnostic laboratory findings, and the disease process. In rare cases, severe neurological symptoms are evident. This 20-year-old woman presented with bloody diarrhea that progressed quickly to respiratory distress requiring intubation and to the development of status epilepticus, controlled only by a barbiturate coma. Ongoing nursing care in the critical care unit was vital in preventing complications and promoting a positive outcome.
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Hemolytic uremic syndrome (HUS) is a disease of rapid onset characterized by microangiopathic hemolytic anemia, acute renal failure, thrombocytopenia, and various degrees of central nervous system complications that can result in chronic, irreversible renal dysfunction or death (Tzipori, Sheoran, Akiyoshi, Donohue-Rolfe, & Trachtman, 2004). Known triggers of HUS include infections, genetic abnormalities, drugs, pregnancy, and organ transplant, among others. A genetic form of thrombotic microangiopathy, known as Factor H associated HUS, is characterized by deficient quantities of factor H and uncontrolled complement activation. The disorder usually leads to end-stage renal disease and often recurs after kidney transplantation (Remuzzi et al., 2004). Most cases of HUS are, however, preceded by infection with Escherichia coli O157:H7 (E. coli) strains that produce Shiga toxin (Stx; Trachtman & Christen, 1999). This type of E. coli causes approximately 73,000 illnesses and 60 deaths annually in the United States, with 2%-15% of cases progressing to HUS (Tserenpuntsag, Chang, Smith, & Morse, 2005).
Throughout the world, HUS is a primary cause of acute renal failure, especially in children (Garg et al., 2003). Other serious complications of this disorder include seizures, cortical blindness, and thrombotic strokes, which occur in 5% to 10% of patients. A similar percentage of patients develop life-threatening cardiopulmonary complications, including acute respiratory distress syndrome, congestive heart failure, and myocarditis (Tzipori et al., 2004). As previously mentioned, most cases of HUS are preceded by an E. coli infection of the gastrointestinal system, a bacterium commonly found in contaminated foods such as meats and dairy products. Other sources of infection include swimming in pools or lakes contaminated by feces (National Institute of Diabetes and Digestive and Kidney Diseases, 2005). E. coli is thought be the cause of more than 80% of the Stx-producing E. coli (STEC) infections that lead to HUS (Banatvala et al., 2001). According to the Centers for Disease Control and Prevention (2007), 8% of patients infected with E. coli progress to HUS, and of the 221 HUS cases reported in 2005, 75% occurred in patients younger than 10 years old. Ten percent of these patients will develop chronic renal failure, and 5% will die (Peacock, Jacob, & Fallone, 2001). The purpose of this article was to examine the characteristics of HUS and discuss the case of a 20-year-old woman with HUS complicated by the development of status epilepticus.
According to Zimmerhackl (2000), the organisms colonize the intestine after being ingested through contaminated food or transmitted by direct person-to-person contact. This particular bacterium has several virulence properties. The organism produces intimin, a protein necessary for attachment to the intestinal wall. Another protein, hemolysin, is also formed. This protein affects the growth of other bacteria and may hemolyze human cells. As the bacteria invade the gastrointestinal system, adherence to mucosal surfaces occurs, producing Stx, which may act both locally and systemically on the gut mucosa (Boyce, Swerdlow, & Griffin, 1995). Because Stx cannot be detected in the serum, it is uncertain whether the toxin is released in a single wave, multiple waves, or continuously (Kaplan, Meyers, & Schulman, 1998).
According to Boyce et al. (1995), the histological pattern of human colonic injury inflicted by E. coli is comparable with the pattern observed in Clostridium difficile colitis, caused by a locally acting toxin, which suggests that Stx plays a part in colonic injury. This toxin can initiate apoptosis in endothelial and epithelial cells in animals (Zimmerhackl, 2000). Damage to the colonic vasculature by this toxin may allow lipopolysaccharide and other inflammatory mediators to invade the circulation, thus initiating HUS (Boyce et al., 1995).
Endothelial cell damage appears to be the primary cause of adhesion and aggregation of platelets, the formation of thrombi, and the impairment of fibrinolysis (Ray & Liu, 2001). In samples from patients with HUS, the renal glomeruli demonstrate thickening of capillary walls, swelling, and detachment of endothelial cells from the basement membrane, with fibrin thrombi and narrowing of the capillary lumen (Ray & Liu, 2001). Detachment of endothelial cell from their basement membrane causes vascular connective tissue elements, such as collagen, to be exposed. Circulating platelets adhere to collagen. This process occurs either directly or via von Willebrand factor and integrin receptors. A loss of antithrombotic properties of the blood vessel wall and intravascular platelet activation then takes place. Adherence of platelets to the damaged vascular endothelium is the hypothesized cause for thrombocytopenia commonly seen in HUS (Ray & Lui, 2001). Vasoactive substances are released by damaged endothelial calls, causing platelet aggregation. Consequently, the formation of thrombotic microangiopathy lesions occurs predominately in renal glomeruli and small renal arterioles. Damage to erythrocytes during passage through diseased capillaries and small blood vessels with fibrin micro-thrombi is believed to be the cause of the hemolytic anemia. Other possible causes of the hemolysis of red blood cells include products released by the activated neutrophils, lipid peroxidation of erythrocyte membranes, and shear stress (Ray & Liu, 2001). Schistocytes and helmet cells are formed as a result. Damage to red blood cells causes the release of hemoglobin into the plasma and the trapping of damaged erythrocytes by the reticuloendothelial system. Fibrin in the microcirculation eventually results in thrombotic occlusion of the vessels first within the kidneys and later other organs (Ray & Liu, 2001).
Neurological complications such as headache, lethargy, seizures, and coma are believed to be caused by microcirculatory injury, cerebral edema, uremia, hypoxemia, and electrolyte imbalances (Schmelzer & Stam, 2000). In a recent study examining the predictors of death in HUS, 8 of 12 children died of complications of the central nervous system that were diagnosed by clinical criteria, computed tomography, intracranial pressure monitoring, and autopsy. Several of the autopsies revealed cerebral edema and/or infarction (Oakes, Siegler, McReynolds, Pysher, & Pavia, 2006).
This young woman presented at a local hospital with a several-day history of bloody diarrhea. She was initially treated with antibiotics because E. coli infection was suspected as a result of ingesting undercooked beef. Four days after admission, the patient developed acute renal failure requiring dialysis and subsequently experienced a tonic-clonic seizure. She was transferred to the intensive care unit, and after the development of thrombocytopenia and elevated lactate dehydrogenase (LDH), the diagnosis of HUS was made. Soon after, the patient progressed to respiratory failure and required intubation. The patient experienced intermittent tonic-clonic seizures that were initially responsive to phenytoin. Status epilepticus developed, however, and a pentobarbital coma was initiated after numerous medications failed to break the seizure activity. The patient experienced multiple complications related to the induced coma, including ileus, pneumonia, and myopathy.
After 60 days of numerous weaning attempts with return of epileptiform activity on electroencephalography, the pentobarbital was successfully weaned and discontinued with no significant seizures. Recovery following withdrawal of the medication was a very slow process.
One month after the pentobarbital was discontinued, the patient tracked with her eyes and was able to follow simple commands, such as blinking, with her face only. The patient transferred from the intensive care unit to a general floor for more intensive rehabilitative therapies. At 2 months, she recovered language and use of her upper extremities. She also regained long-term memory. The patient spent several weeks on a rehabilitation unit and later transferred to a facility closer to her home. In all, she was hospitalized acutely, and for rehabilitation, for 144 days.
Care of the patient required a multidisciplinary team consisting of doctors, nurses, therapists, and chaplains, among others. Nursing played a pivotal role in coordinating the team and executing the plan of care.
As discussed by Schmelzer and Stam (2000), nursing care of HUS patients involves careful monitoring of laboratory values, particularly trends in blood urea nitrogen and creatinine, electrolytes, and platelet count. To prevent further bleeding complications secondary to thrombocytopenia, nurses should take care to avoid use of blood pressure cuffs and tourniquets. Invasive procedures such as rectal temperature and venipunctures should be avoided whenever possible (Camp-Sorrell, 2008). Dialysis is required in 50% of HUS patients (Peacock et al., 2001). Close hemodynamic monitoring is indicated during dialysis to assess for hypotension. Fluid balance needs to be carefully observed by measuring fluid intake and output, monitoring daily weights, and assessing for pulmonary and peripheral edema. Neurological status should be assessed frequently to ensure early detection of deterioration. It may be valuable to seek the opinion of the patient's family whether or not they notice changes in the patient's level of consciousness (Schmelzer & Stam, 2000).
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