NDT Advance Access originally published online on August 8, 2007
Nephrology Dialysis Transplantation 2007 22(12):3676-3677; doi:10.1093/ndt/gfm533
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Continuous dialysis by gravity through the filter of the extracorporeal membrane oxygenation
Email: ponteb{at}bluemail.ch
Sir,
Continuous renal replacement therapies (CRRT) are characterized generally by their good haemodynamic tolerance [1–4]. However, in some critical clinical situations, even CRRT are impracticable.
A 22-year-old man with Marfan syndrome, admitted to the ICU after emergency dissecting aneurysm surgery of the thoracic aorta, presented extreme haemodynamic instability (blood pressure: 46/35 mmHg; Central venous pressure: 9 cmH2O). Despite fluid resuscitation (12 l) including sodium bicarbonate solutions, vasoactive drugs, intraaortic balloon counterpulsation and extracorporeal membrane oxygenation (ECMO) support, he remained unstable. Acute kidney injury developed with anuria, high levels of serum creatinine (3.97 mg/dl), BUN (31 mg/dl), toxic hyperkalemia (8.2 mmol/l) and hyperlactactatemia (10.1 mmol/l). Temperature was 36°C, arterial pH 7.32; pO2 55.6 mmHg; pCO2 37.7 mmHg and bicarbonate 19.2 mmol/l.
As standard renal replacement therapies could not be used due to the blood pressure (BP) levels, we tried another depurative technique.
The ECMO system haemofilter was used as dialysis membrane (1.4 m2 poly-ethersulfone membrane; Cobe cardiovascular, Mirandola, Italy). Dialysis fluid was provided by two 5 l bags suspended above the patient (Figure 1). A ‘Y’ tube system was used to deliver a kalium-free dialysate (Na 140 mmol/l, bicarbonate 34 mmol/l). To control dialysis flow speed, two plastics locks provided by the manufacturer alternatively closed and opened the system. From the filter, another ‘Y’ tube collected the drainage fluid in two 5 l bags below the patient. Each bag was weighed, using an electronic newborn scale, to calculate the ultrafiltration volume. A ‘Y’ line returned the blood from the ECMO: the main branch directly to the patient and the other to the haemofilter. The dialysis flow was maintained at 291 ml/min for 2 h and decreased to 83 ml/min for 3 h (mean flow 166 ml/min). Patient's net balance throughout the procedure was zero and temperature 35.5°C. After 5 h, BP increased to 76/45, pH to 7.4, kaliemia decreased to 6.2 mmol/l, lactate to 8.5 mmol/l and bicarbonate remained stable. In the absence of a positive fluid balance, improvement of kaliemia was attributed to dialysis. Improvement of BP could be due to the decrease in potassium levels and the slightly lower core temperature [5]. Lactate decrease was probably due to a better tissue perfusion, rather than a dialytic effect [6]. Gravity dialysis could then be changed to conventional CRRT.
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In summary, the technique of continuous dialysis by gravity using the ECMO filter could be a therapeutic option in critically unstable patients, unable to tolerate CRRT and requiring urgent management of electrolytic disturbances (Figure 2).
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Conflict of interest statement. None declared.
1Nephrology Department
Hospital Ramón y Cajal, Madrid
2Anesthesiology Department
Hospital Ramón y Cajal, Madrid
Notes
See http://www.oxfordjournals.org/our_journals/ndtplus/
References
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- Dhondt A, Eloot S, Wacrter DD, et al. Dialysate partitioning in the Genius batch hemodialysis system: effect of temperature and solute concentration. Kidney Int (2005) 67:2470–2476.[CrossRef][Web of Science][Medline]
- Luft FC. Lactic acidosis update for critical care clinicians. J Am Soc Nephrol (2001) 12(Suppl 17):S15–S19.
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