Use of nitroprusside to increase tissue temperature during local hyperthermia in normal and tumor-bearing dogs.
The present study investigates the effects of nitroprusside, a potent vasodilating agent, on tissue temperature during local hyperthermia in five normal and five tumor-bearing dogs. Caudal thigh muscles were heated in normal dogs and muscle temperatures were recorded during hyperthermia. Tumor-bearing dogs received two hyperthermia treatments during a course of radiation therapy. Temperatures were recorded in tumor and surrounding normal tissues. Mean arterial pressure was decreased by approximately 40-45% during nitroprusside infusion and was associated with a compensatory increase in heart rate and increases in tissue temperature. In normal dogs, muscle temperatures increased an average of 1.7 degrees C with nitroprusside administration. When nitroprusside was administered at the beginning of local hyperthermia to induce step-down heating, approximately 48% of the measured positions in caudal thigh muscle achieved a temperature greater than or equal to 43 degrees C, sufficient to induce step-down heating, during the hyperthermia episode. In tumor-bearing dogs, there was a significant increase in tumor and normal tissue temperatures during nitroprusside administration. Estimated T90 and T50 descriptors increased by 0.9 degrees C and 1.6 degrees C, respectively, for tumor tissue and by 0.4 degrees C and 1.2 degrees C, respectively, for normal tissue. Despite the increase in normal tissue temperatures no toxicity was observed in these dogs. Nitroprusside may be a useful agent for manipulation of tumor temperatures during the entire hyperthermia treatment or for a short time period at the initiation of treatment to induce step-down heating.
Prescott
D M
DM
Dept. of Radiation Oncology, Duke University Medical Center, Durham, NC 27710.
Samulski
T V
TV
Dewhirst
M W
MW
Page
R L
RL
Thrall
D E
DE
Dodge
R K
RK
Oleson
J R
JR
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D003131:Combined Modality Therapy; D004285:Dogs; D006979:Hyperthermia, Induced / Q000379:methods*; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000628:therapy*; D009599:Nitroprusside / Q000627:therapeutic use*; D013268:Stimulation, Chemical
D009599:Nitroprusside