Abstract
Isoflurane (ISO), a potent inhalation anesthetic, is commonly used for infant anesthesia, but its cardiovascular effects are poorly defined. We invasively measured the effects of ISO on the major determinants of cardiac output in 15 acutely-instrumented healthy newborn piglets and 9 age-matched controls. End-tidal ISO concentrations were determined by mass spectrometry. Hemodynamic readings were obtained at baseline, 0.5, 1.0, and 1.3 MAC (minimum alveolar concentration needed for anesthesia).
At 1 MAC: CI -5% (NS), MAP -37%*, systemic resistance -32%*, dP/dT/DP40 -32%*, echo shortening fraction -20%*, HR -15% (NS), LVEDP -18% (NS). 1.3 MAC ISO did not depress any variable further, except HR (-19%*) (*=p<.05 vs baseline and control). 5 pigs who had ↓ HR were paced; MAP, dP/dT/DP40, and systemic resistance remained low while CI did not change. In 12 other piglets, the blood, heart, and brainstem lethal:MAC concentration ratio was 2.1, 2.0, and 2.8, respectively.
At 1 MAC, ISO depressed contractility and occasionally caused bradycardia. Because MAP and systemic resistance decreased to a similar extent, CI was unchanged. ↓ MAP may adversely affect flow to those vital organs lacking mature autoregulation. ISO has a limited margin-of-safety in newborn piglets.
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Schleber, R., Cook, D., Shlu, G. et al. 411 HEMODYNAMIC EFFECTS AND MARGIN-OF-SAFETY OF ISOFLU RANE IN NEWBORN PIGLETS. Pediatr Res 19, 179 (1985). https://doi.org/10.1203/00006450-198504000-00441
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DOI: https://doi.org/10.1203/00006450-198504000-00441