Blood flow distribution in dogs during hypothermia and posthypothermia

Abstract

Blood flow distribution in tissues of mongrel dogs during hypothermia was studied with radionuclide-tagged microspheres. The animals were cooled at 21 degrees C and rewarmed under thiamylal sodiuni anesthesia. During hypothermia, cardiac output fell to 20% of the control; the highest rate of blood flow relative to normothermic values was observed in the subendocardium of the left ventricle, and the lowest in the hypophysis. Each tissue showed specific reactions to hypothermia. During hypothermia the myocardial and brain-stem blood flows were about 40% of the control; almost all of the digestive tract, striated muscle, adrenal gland, and hypophysis blood flows were maintained at 20% or less of the control. After rewarming, cardiac output recovered to values significantly lower than control. The myocardium, brain, renal cortex, and striated and smooth muscle recovered to control levels; however, blood flow to the digestive organs, bronchial artery flow to the lung, and flow to the endocrine organs did not completely recover by 2 after rewarming.

Effects on dogs of surface-induced hypothermia and rewarming on the right heart function and pulmonary circulation

“…It has been reported that in some other studies cardiac output also fell linearly with decreasing core temperature (Kawashima et al 1976;Anzai et al 1978;Chen 1978;Tveita et al 1994). The lack of initial increases in heart rate and cardiac output in the present study may have been caused by the deep anaesthesia, or by an already enhanced sympathetic tone at the beginning of the experiments.…”

Effects of Constant Flow vs. Constant Pressure Perfusion on Fluid Filtration in Severe Hypothermic Isolated Blood-Perfused Rat Lungs

“…At variation from isolated lungs that are perfused at constant flow or constant pressure, intact organisms adjust perfusion to the demands of the local tissues in an interaction between peripheral sensors and the central nervous system (31). With reports of cardiac output in animals as low as 10% of the normal at a core temperature of 17°C, we assume that larger parts of the circulation have been shut down although the pulmonary artery pressure tended to be maintained almost at the normal level during hypothermia in these animals (5, 6). Isolated lungs have no autonomic nerves or hormonal influences.…”

“…Isolated lungs have no autonomic nerves or hormonal influences. However, despite lung circulation is locally regulated, the markedly reduced blood flow in response to hypothermia in lungs of the Constant PPA group, reminds highly on the changes taking place in hypothermic intact animals and even in man (5, 6, 8, 11, 32). …”

“…Previous researchers have noticed that in dogs, when cooled to a core temperature of 17°C, cardiac output decreases exponentially to only 10% of its value at normal core temperature (5, 6). Correspondingly, Tveita and his coworkers noticed a fall in cardiac output to approximately 13% of its value during normothermia when lowering temperature in the aortic arc of rats to 13–15°C (7).…”

A model of deep experimental hypothermia and rewarming in rat

“…The alpha-stat refers to restrain the pH at 7.40 only when measured at 37 C (Kofstad, 1996). Since during hypothermia there is a decrease (Watanabe et al, 1999) and redistribution (Anzai et al, 1978) of the blood flow, we choose the liver as an indicator of the viability of the model due to its important role as a vital metabolic organ for both endogenous and exogenous substances. In the present study we have used the alphastat strategy and have measured the hepatic regional blood flow, the acid-base balance, blood lactate, the release of transaminases and the survival rate in rewarmed hypothermic rats.…”