Plasma concentrations of noradrenaline and adrenaline and plasma renin activity during extradural blockade in dogs.
Anaesthetized dogs (pentobarbitone 25 mg kg-1 + 3 mg kg-1 h-1) with a Teflon catheter inserted to the femoral artery for pressure and heart rate measurement and blood sampling were studied. Extradural puncture was carried out at L7--S1 under x-ray control and 2% lignocaine (1 ml min-1) infused for approximately 10 min. During extradural block a decrease in arterial pressure was accompanied by a simultaneous decrease in plasma noradrenaline concentration (NA) and a compensatory increase in plasma renin activity (PRA), which became significant 15 min after commencing the block when the arterial pressure was at the minimum. Dihydroergotamine (DHE) led to a rapid reversal of the hypotension with no change in heart rate and a decrease in PRA. Hypovolaemia (blood loss 5 ml kg-1) was induced before and during block, respectively, in two further experimental groups. Increased NA and PRA were found under hypovolaemia without extradural block, but only PRA increased with hypovolaemia and a block. The effects of DHE in the later studies were comparable to those observed in the initial study.
D000767:Anesthesia, Epidural; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004087:Dihydroergotamine / Q000494:pharmacology; D004285:Dogs; D004837:Epinephrine / Q000097:blood*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006470:Hemorrhage / Q000378:metabolism; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D012083:Renin / Q000097:blood*; D013997:Time Factors
D004087:Dihydroergotamine; D008012:Lidocaine; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine