Heat accumulation with relative blood volume decrease.
BACKGROUND
Both hypovolemia and heat accumulation act as powerful perturbations of blood pressure control. In hemodialysis, hypovolemia and heat accumulation often develop simultaneously, and the question arises of whether and to what extent these perturbations are linked.


METHODS
Heat accumulation was measured by the amount of thermal energy (E) removed from a patient during prescribed ultrafiltration under isothermic hemodialysis conditions, ie, constant patient temperature. Measurement and control of temperatures and thermal energies were performed using the blood temperature monitor. Relative blood volume (RBV) was measured using the blood volume monitor.


RESULTS
Thirty-eight treatments were analyzed in 12 patients (3 women). During treatments lasting 189 +/- 28 minutes, 5.1% +/- 1.3% of postdialysis body weight were removed from patients by ultrafiltration at a mean rate of 1.1 +/- 0.3 L/h. Blood volumes decreased to 85% +/- 7% of initial values, and 229 +/- 106 kJ of E were removed from patients at a cooling rate (J) of 20 +/- 8 W, corresponding to 28% +/- 11% of estimated energy expenditure (H%). E, J, and H% significantly increased as RBV decreased (P < 0.05). Linear regression analysis between J and RBV showed that approximately 1 W had to be removed from the patient for each percentage of change in blood volume (J = -102.38 + 0.97* RBV; r2 = 0.63).


CONCLUSIONS
Results show that the probability for the effect of heat stress during hemodialysis increases with ultrafiltration-induced blood volume changes. Temperature control is an important aspect of hemodialysis treatment.
D000222:Adaptation, Physiological / Q000502:physiology; D001810:Blood Volume / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology; D005112:Extracorporeal Circulation / Q000379:methods; D005260:Female; D017583:Hemodiafiltration / Q000009:adverse effects / Q000379:methods; D006439:Hemodynamics / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D013312:Stress, Physiological / Q000150:complications / Q000503:physiopathology / Q000517:prevention & control