Therapeutic hypothermia is associated with a decrease in urine output in acute stroke patients

Abstract

Aims: It is unclear what effect therapeutic hypothermia may have on renal function, because its effect has so far been primarily evaluated in settings in which there may be possible confounding perturbations in cardiovascular and renal physiology, such deep intraoperative hypothermia, general anesthesia, and post-cardiac arrest. We sought to determine if therapeutic hypothermia affects renal function in awake patients with normal renal function who were enrolled into a clinical trial of hypothermia plus intravenous thrombolysis for acute ischemic stroke.

Methods: Eleven patients with normal renal function were cooled to 33°C for 24 h using an endovascular catheter, and then re-warmed over 12 h to 36.5°C, while hourly temperature, blood pressure, and fluid status data was recorded. Blood samples for blood urea nitrogen (BUN), creatinine, and hematocrit were drawn prior to treatment (baseline), immediately after hypothermia and re-warming (day 2), and again at day 7 or discharge, and values compared.

Results: On initiation of cooling, temperatures dropped from a median pre-treatment value of 36.1°C (IQR: 35.8-36.4°C) to 33.1°C (IQR: 33.1-33.4°C). Urine output decreased 5.1 ml/h for every 1°C decrease in body temperature (p-value=0.001), with no associated serious adverse events. There were no statistically significant changes in BUN, creatinine, or hematocrit in the hypothermia patients.

Conclusion: Inducing hypothermia in patients with relatively unperturbed renal physiology results in a decrease in urine output that is linearly correlated with the decrease in core temperature. This has important implications for fluid management in patients undergoing therapeutic hypothermia.

Conflict of interest statement

Conflict of interest statement

No conflict of interest declared.

Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Figures

Figure 1

A, Hourly urine output as correlated with core temperature (with a regression line) in one of the hypothermia patients. B, Hourly net fluid status (the intravenous fluid volume minus the urine output) as correlated with core temperature for the same patient.

Figure 2

Hourly urine output (UOP) as correlated with centralized temperature (defined as the patient's temperature minus the lowest temperature of all patients in the study) for the entire group of hypothermia patients.

Figure 3

A) Comparison between normothermic control and hypothermia patients’ serum creatinine (CREAT), and B) serum blood urea nitrogen (BUN). Individual patients are shown in grey in the background (solid lines, hypothermia; dashed lines, normothermia controls). Each thick line represents a group (black, hypothermia; hatched, normothermia), with median and interquartile range values shown at each time-point. Bl, baseline; d2, day 2 (post-treatment, at completion of hypothermia and re-warm); d7, day 7.