Increasing inspired isoflurane concentration from 1.5% to 5% acutely suppressed cardiorespiratory function in all rat strains, with SHR/Izm rats exhibiting the most profound sensitivity to cardiovascular suppression.
Does increasing isoflurane concentration differentially suppress cardiorespiratory function in SHR/Izm, WKY/Izm, and Crl:CD (SD) rats?
Spontaneously hypertensive rats (SHR/Izm) are more sensitive to the cardiorespiratory suppressive effects of high-dose isoflurane anesthesia than normotensive strains, highlighting the need for careful anesthetic management in hypertensive models.
Isoflurane is a widely used anesthetic, but its effects with increase in inspired concentration on cardiovascular function have not yet been clarified in rodents. Additionally, there are only a few studies comparing isoflurane-induced cardiorespiratory effects between rat strains. Thus, we investigated the differences in cardiorespiratory responsiveness to increasing concentration of inspired isoflurane in SHR/Izm, WKY/Izm and Crl:CD (SD) rats, by increasing the setting values of vaporizer’s dial indicator. The rats were anesthetized with 1.5% isoflurane, and electrocardiograms, blood pressure, and respiratory rate were recorded simultaneously. Thereafter, the inspired concentration was increased stepwise to 2%, 3%, 4%, and 5%, and cardiorespiratory parameters were obtained at each concentration. Under anesthesia at more than 4%, although prolongation of the RR and PR intervals was observed in all strains, shortening of the QTC interval was found only in SHR/Izm rats. From frequency domain analysis of heart rate variability, an increase in LF/HF ratio and a decrease of HF components were observed in SHR/Izm and WKY/Izm rats, respectively, with 5% isoflurane anesthesia. Blood pressure and heart rate were remarkably reduced in SHR/Izm rats at higher concentrations, whereas the reduction was smallest in WKY/Izm rats among the three strains examined. Respiratory rate was inspired concentration-dependently decreased in all strains. These results suggested that SHR/Izm rats are more sensitive to suppressive effects of isoflurane anesthesia on cardiovascular function among these rat strains.
Kato et al. (Fri,) conducted a other in Cardiorespiratory function under anesthesia (n=23). Isoflurane anesthesia vs. 1.5% isoflurane (baseline) and between-strain comparison was evaluated on Cardiorespiratory parameters (ECG, heart rate, blood pressure, respiratory rate). Increasing inspired isoflurane concentration from 1.5% to 5% acutely suppressed cardiorespiratory function in all rat strains, with SHR/Izm rats exhibiting the most profound sensitivity to cardiovascular suppression.
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