Cardiovascular responses to experimental infra-renal aortic cross-clamping. Modulating effects of isoflurane, sodium nitroprusside and milrinone.
BACKGROUND
Pharmacological control of blood pressure is usually indicated during aortic cross-clamping (AXC). The aim of this study was to analyze the modulation by isoflurane (ISO), sodium nitroprusside (SNP) and milrinone (MIL) of the systemic circulatory responses to a standardized infra-renal AXC.


METHODS
Chloralose-anaesthetized pigs were exposed to AXC at control (no vasoactive drugs) and during the administration of each of the drugs.


RESULTS
During control, AXC increased mean arterial pressure (MAP, 17 +/- 4%) and systemic vascular resistance (SVR, 27 +/- 7%), but induced no significant changes in cardiac output (CO), heart rate (HR), pulmonary arterial pressures, pulmonary vascular resistance or central venous pressure. Low-dose ISO (0.7%) and investigated doses of SNP and MIL did not significantly alter this response. High-dose ISO (1.4%, attenuated the AXC-induced increase in SVR, but not in MAP. All drugs decreased non-clamp MAP levels. Therefore, with low-dose ISO and with SNP or MIL, peak MAP during AXC was not significantly different from control non-clamp levels (i.e. prior to pharmacological or surgical interventions). High-dose ISO was associated with a MAP during AXC that was below control non-clamp levels.


CONCLUSIONS
The objective that during AXC MAP should not exceed control non-clamp levels was achieveable by ISO, SNP or MIL. The modulating actions of the drugs on MAP during AXC were exerted mainly through reductions in non-clamp levels. This systemic hypotension was associated with decreased CO and SVR during ISO, and with decreased SVR and increased HR during SNP and MIL. Attenuation of the AXC-induced increase in SVR was produced only by 1.4% ISO.
Seeman-Lodding
H
H
Department of Anesthesiology, Ostra University Hospital, Gothenburg, Sweden.
Biber
B
B
Martner
J
J
Pontén
J
J
Winsö
O
O
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D020105:Milrinone; D009599:Nitroprusside / Q000494:pharmacology*; D011728:Pyridones / Q000494:pharmacology*; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
D018685:Anesthetics, Inhalation; D011728:Pyridones; D014665:Vasodilator Agents; D009599:Nitroprusside; D007530:Isoflurane; D020105:Milrinone