Letters to the Editor: Letter to the Editor
To the Editor
Continuous renal replacement therapy (CRRT) is frequently used as an intraoperative modality for patients with renal dysfunction undergoing liver transplantation.1–4 It was our impression that hypothermia was more frequent in such cases, and this view was supported by a review of our anesthesia records that showed a tendency toward lower core temperatures in liver transplant patients undergoing intraoperative CRRT.
Further investigation revealed that our center’s CRRT device (NxStage System One, NxStage Medical, Lawrence, MA) has no temperature display. The system reportedly has low and high temperature limits of 29°C and 39°C that will trigger an alarm, but there is no display of the current operating temperature within those limits. The system also has a fluid warmer attached to it. The dial to adjust the temperature of the warmer has no numeric markings on it. It simply has a graphic suggesting that it gets warmer as the knob is turned clockwise (Figure). Only a US Food and Drug Administration (FDA) filing indicates that the temperature setting of the device ranges from 31°C to 38°C.5 There is no display of the current temperature on the warmer, although there is a light to indicate that the dialed temperature was reached and an internal overheat alarm at 41°C. As such, operators have no way to know the temperature of the fluid or blood return to the patient. Consequently, the warmer dial may be cautiously set in the middle to avoid presumed extremes. Unfortunately, this “happy medium” is approximately 34.5°C, actively cools patients, and produces hypothermia more severe than we saw before the use of intraoperative CRRT.
In the intensive care unit setting, hypothermia has been reported to be frequent in association with CRRT.6 In outpatient hemodialysis, deliberate hypothermia has been advocated to avoid hypotension.7 Even in the absence of CRRT, patients in the operating room tend to become hypothermic from anesthetic agent-induced impairment of thermoregulatory mechanisms coupled with lower ambient temperatures. The addition of a CRRT circuit compounds this problem in a manner similar to that seen with veno-venous bypass.8 The impact of hypothermia during liver transplantation has not been well studied, but best evidence is that it is detrimental in other types of surgery and so should be avoided.9
It is unknown why this device was designed or approved without temperature monitoring or even temperature markings on the warmer dial. The FDA requires hemodialysis units to have operating temperatures monitored and state law requires blood warmers to have temperature monitored, but technically the device in question is for hemofiltration rather than hemodialysis, and the warmer is for replacement fluid rather than blood.10,11 In any case, we recommend that anesthesiologists be familiar with the CRRT device being utilized and work with the operators to optimize the device settings to avoid contributing to hypothermia in the operating room.
David B. Wax, MDSamuel DeMaria Jr, MDJeron Zerillo, MDIcahn School of Medicine at Mount SinaiNew York, New Yorkdavid.firstname.lastname@example.org
1. Nadim MK, Annanthapanyasut W, Matsuoka L, et al. Intraoperative hemodialysis during liver transplantation: a decade of experience. Liver Transpl. 2014;20:756–764.
2. Agopian VG, Dhillon A, Baber J, et al. Liver transplantation in recipients receiving renal replacement therapy: outcomes analysis and the role of intraoperative hemodialysis. Am J Transplant. 2014;14:1638–1647.
3. Douthitt L, Bezinover D, Uemura T, et al. Perioperative use of continuous renal replacement therapy for orthotopic liver transplantation. Transplant Proc. 2012;44:1314–1317.
4. Townsend DR, Bagshaw SM, Jacka MJ, Bigam D, Cave D, Gibney RT. Intraoperative renal support during liver transplantation. Liver Transpl. 2009;15:73–78.
6. Akhoundi A, Singh B, Vela M, et al. Incidence of adverse events during continuous renal replacement therapy. Blood Purif. 2015;39:333–339.
7. Selby NM, McIntyre CW. A systematic review of the clinical effects of reducing dialysate fluid temperature. Nephrol Dial Transplant. 2006;21:1883–1898.
8. Khoury GF, Kaufman RD, Musich JA. Hypothermia related to the use of venovenous bypass during liver transplantation. Eur J Anesthesiol. 1990;7:501–503.
9. Reynolds L, Beckmann J, Kurz A. Perioperative complications of hypothermia. Best Pract Res Clin Anaesthesiol. 2008;22:645–657.