The effects of phentolamine and isoproterenol in experimental hemorrhagic shock in the dog.
The effects of phentolamine and isoproterenol were investigated in eight dogs versus eight control dogs. The dogs were placed into simulated hemorrhagic shock using a reservoir to maintain arterial pressure at 40 mmHg until the level of the reservoir decreased to 20% of the maximum shed volume, or for 2 hr in the isoproterenol groups. After 30 min, during which phentolamine, isoproterenol, or saline was infused, the remaining blood was reinfused. Phentolamine was given as a 5-mg intravenous bolus. Isoproterenol was infused at 2.0 micrograms/kg/min. The dogs were monitored until their arterial pressure declined to 70 mmHg (50 mm for isoproterenol) or death ensued. Phentolamine lowered peripheral resistance and the size of the vascular space increased as shown by the rapid uptake of blood, 214.0 +/- 12.5 ml, during the 30 min after injection. The control group took back only 72.5 +/- 7.5 ml. Although reinfusion of the shed blood restored blood pressure to near normal for a short period, all groups showed a progressive decline in arterial pressure. There was no evidence that phentolamine or isoproterenol significantly decreased capillary permeability or that renal or pulmonary function were significantly altered by treatment. A large increase in venous oxygen content occurred following phentolamine, and a mild inotropic and vasodilator action lasted for about 30 min. Isoproterenol also decreased postinfusion arterial pressure. Neither drug influenced the hypoglycemia seen after reinfusion.
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure / Q000187:drug effects; D002199:Capillary Permeability / Q000187:drug effects; D004285:Dogs; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D010646:Phentolamine / Q000494:pharmacology / Q000627:therapeutic use*; D012771:Shock, Hemorrhagic / Q000188:drug therapy* / Q000503:physiopathology; D014655:Vascular Resistance / Q000187:drug effects
D001786:Blood Glucose; D007545:Isoproterenol; D010646:Phentolamine