Why the study?
Does intravenous saline infusion alter heart rate in anesthetized dogs depending on preinfusion heart rate and body temperature?
Does intravenous saline infusion alter heart rate in anesthetized dogs depending on preinfusion heart rate and body temperature?
The Bainbridge reflex (chronotropic response to volume loading) depends on the baseline heart rate and requires vagal tone, as demonstrated by the lack of response in hypothermic dogs.
Supports rate-dependent Bainbridge reflex requiring vagal tone in normothermic dogs; leaves open translation to human physiology and volume management.
Ninety-four anesthetized dogs at normal body temperature received 293 intravenous saline infusions by gravity flow through either a femoral or jugular vein. Also nine dogs with body temperature lowered to 27 C received 30 similar infusions. Heart rate and blood pressure were monitored by transducer and oscillographic recording. The chronotropic response of the normothermic group varied with the preinfusion heart rate, with those below 140/min generally showing increases and those above showing no response or a decrease. Negative results with hypothermic animals also having slow preinfusion rates indicate the Bainbridge effect requires the slow preinfusion heart rate to be under vagal inhibition.
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Ahmad et al. (1963) studied this question.
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