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Departments of Anesthesia and Critical Care and Cardiothoracic Surgery, Royal Brompton Hospital, London, UK
Address correspondence and reprint requests to Siân Jaggar, MBBS, FRCA, MD, Royal Brompton Hospital, Sydney Street, London SW3 6NP. Address e-mail to s.jaggar{at}rbh.nthames.nhs.uk.
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Case Report |
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Surgery was uneventful, with minimal blood loss. She was extubated and transferred to the ward the following day (Hb 11.7 g/dL) on continuing iron supplementation. The subsequent 4 days fluid balance was +175 mL/day (insensible losses). She was readmitted to the intensive care unit (ICU) obtunded, hypotensive, and anuric with atrial fibrillation and pulmonary edema. Laboratory data demonstrated marked lactic acidosis, Hb 7.6 g/dL (no evidence of bleeding/hemolysis), and creatinine 400 µmol/L. Mechanical ventilation, milrinone (0.7 µg · kg–1 · min–1), norepinephrine (0.02 µg · kg–1 · min–1), and antibiotics were commenced. Continuous venovenous hemodiafiltration (CVVHDF) for worsening acidosis/oliguria necessitated anticoagulation (activated partial thromboplastin time, 35–45). rhEPO was recommenced (24,000IU 3x/wk), iron supplementation was continued, and blood sampling was minimized. During CVVHDF fluid balance was +263 mL/day (insensible losses). Despite this, Hb decreased (4.2 g/dL). Therefore, rhEPO was increased (38,000 IU/day) together with iron sucrose (100 mg 3x/wk), hydroxycobalamin (1 mg 3x/wk), and folic acid (5 mg daily). Subsequently, Hb increased (10.1 g/dL) and polyuria developed (fluid balance –142 mL/day, 3% blood volume), allowing discontinuation of rhEPO/CVVHDF and discharge from ICU 11 days later.
A fall during mobilization resulted in a hematoma (8 x 5 cm, adductor magnus) requiring surgery. The reduction in Hb (3.6 g/dL) was treated with large-dose rhEPO. She was discharged 3 mo after initial surgery and remains well 15 mo later.
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Acute renal failure (ARF) requiring hemofiltration occurs in 1%–5% of cardiac surgery patients (7), requiring anticoagulation, recurrent blood sampling, and potential for blood loss when changing filters. In critically ill patients, both ARF and its management may result in major alterations in fluid balance, together with hemolysis. Seventy percent of the decline in Hb during ICU admission (inexplicable by acute blood loss) is unexplained by iatrogenic phlebotomy (8). Although patients with systemic inflammatory response syndrome may not exhibit laboratory or clinical signs of hemolysis, premature destruction of erythrocytes occurs (8,9), possibly accounting for the disproportionate decrease in Hb after surgery in this case.
The use of rhEPO in chronic renal failure is established (10), although its use in ARF remains controversial. Erythropoietic balance in critical illness is poorly understood. Although animal studies have suggested that EPO is potentially beneficial, human studies in critically ill patients demonstrate elevated levels of endogenous EPO (suggesting exogenous treatment may be ineffective) (11,12). However, in such patients there is reduced production/survival of erythrocytes, and decreased iron availability for erythropoiesis despite adequate (or supra-normal) iron stores (13). Thus, despite endogenous EPO increase, the reticulocyte response is blunted. The situation is complicated by inflammatory/antiinflammatory cytokines, each affecting erythropoiesis (including bone marrow suppression, decreased iron availability, and reduced EPO production). Moreover, in critically ill patients iron is sequestered by macrophages, reducing availability for erythropoiesis (13). Therefore, iron or EPO administered alone may be ineffective (14) and the magnitude of response may be unpredictable (15).
When exogenous EPO has been used in critically ill patients, the complex interactions described result in variable delays to increases in EPO/Hb levels (2–6 wks) and reticulocyte count (7–21 days). Attributing a precise temporal relationship to any treatment in this scenario is impossible. In the case described, there were no transfusion/major fluid balance changes. It is therefore difficult to explain the increase in Hb (4.2 to 10.1 g/dL) other than by increased erythropoiesis. Although the reticulocyte levels (>2%) indicated active erythropoiesis, Hb levels continued to decrease, suggesting relatively inadequate reticulocytosis. In healthy volunteers EPO showed a dose-response between 500 IU/kg and 1000 IU/kg (16). The 444 IU/kg dose administered to this patient resides to the left of the dose-response curve, and increasing the dose to 700 IU/kg would be predicted to elicit greater effect.
Despite theoretical concerns regarding efficacy of rhEPO in the critically ill, some studies report its use in the ICU (8,9,12,13,17). However, many have excluded severely ill patients and those with ARF or cardiac disease, and used either reticulocyte count or time to transfusion as the primary end-point. The case presented here differs in that the patient had ARF and severe cardiac disease, there was no possibility of transfusion, and the doses of rhEPO used were larger than in many published studies. Our intention is to alert ICU physicians to a potential salvage treatment when transfusion is contraindicated.
We would like to thank Dr. J. Burman, Dr. S. Davidson and the ICU staff at the Royal Brompton Hospital for their help in the management of this patient.
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Accepted for publication January 25, 2005.
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