Metabolic benefits of surface counter warming during therapeutic temperature modulation

To determine the impact of counter warming (CW) with an air circulating blanket on shivering and metabolic profile during therapeutic temperature modulation (TTM).

A prospective observational study.

An 18-bed neurologic intensive care unit.

Fifty mechanically ventilated patients with brain injury undergoing TTM with automated surface and intravascular devices.

Fifty indirect calorimetry (IDC) measurements with and without CW during TTM.

IDC was continuously performed for 10-15 minutes at baseline with CW (phase I), off CW (phase II), and again after the return of CW (phase III). Shivering severity during each phase was scored on a scale of 0-3 using the Bedside Shivering Assessment Scale (BSAS). Resting energy expenditure (REE), oxygen consumption, and carbon dioxide production were determined by IDC; 56% were women, with mean age 61 +/- 15 years. At the time of IDC, 72% of patients had signs of shivering (BSAS >0). All measures of basal metabolism increased after removal of the air warming blanket (from phases I and II); REE increased by 27% and oxygen consumption by 29% (both p < 0.002). A one-point increase in baseline BSAS was noted in 55% (n = 23/42) of patients from phase I to phase II. In a multivariate analysis, sedative use (p = 0.03), baseline moderate to severe shivering (p = 0.04), and lower serum magnesium levels (p = 0.01) were associated with greater increases in REE between phase I and phase II of CW. Phase III of CW was associated with a reversal in the increases in all metabolic variables.

Surface CW provides beneficial control of shivering and improves the metabolic profile during TTM.