Effects of remifentanil infusion regimens on cardiovascular function and responses to noxious stimulation in propofol-anesthetized cats.
OBJECTIVE
To evaluate the effects of 2 remifentanil infusion regimens on cardiovascular function and responses to nociceptive stimulation in propofol-anesthetized cats.


METHODS
8 adult cats.


METHODS
On 2 occasions, cats received acepromazine followed by propofol (6 mg/kg then 0.3 mg/kg/min, i.v.) and a constant rate infusion (CRI) of remifentanil (0.2 or 0.3 microg/kg/ min, i.v.) for 90 minutes and underwent mechanical ventilation (phase I). After recording physiologic variables, an electrical stimulus (50 V; 50 Hz; 10 milliseconds) was applied to a forelimb to assess motor responses to nociceptive stimulation. After an interval (> or = 10 days), the same cats were anesthetized via administration of acepromazine and a similar infusion regimen of propofol; the remifentanil infusion rate adjustments that were required to inhibit cardiovascular responses to ovariohysterectomy were recorded (phase II).


RESULTS
In phase I, heart rate and arterial pressure did not differ between remifentanil-treated groups. From 30 to 90 minutes, cats receiving 0.3 microg of remifentanil/kg/min had no response to noxious stimulation. Purposeful movement was detected more frequently in cats receiving 0.2 microg of remifentanil/kg/min. In phase II, the highest dosage (mean +/- SEM) of remifentanil that prevented cardiovascular responses was 0.23 +/- 0.01 microg/kg/min. For all experiments, mean time from infusion cessation until standing ranged from 115 to 140 minutes.


CONCLUSIONS
Although the lower infusion rate of remifentanil allowed ovariohysterectomy to be performed, a CRI of 0.3 microg/kg/min was necessary to prevent motor response to electrical stimulation in propofol-anesthetized cats. Recovery from anesthesia was prolonged with this technique.
Correa
Mariana do A
Mdo A
Department of Veterinary Surgery and Anesthesiology, Faculdade de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista, Botucatu, São Paulo, Brazil, CEP 18618-000.
Aguiar
Antonio J de A
AJ
Neto
Francisco J Teixeira
FJ
Mendes
Guilherme da M
Gda M
Steagall
Paulo V M
PV
Lima
Alfredo F da M
AF
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000762:Anesthesia Recovery Period; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002319:Cardiovascular System / Q000187:drug effects*; D002415:Cats / Q000502:physiology* / Q000601:surgery; D018592:Cross-Over Studies; D004558:Electric Stimulation; D004562:Electrocardiography / Q000662:veterinary; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007044:Hysterectomy / Q000662:veterinary; D007262:Infusions, Intravenous; D010147:Pain Measurement / Q000187:drug effects*; D010880:Piperidines / Q000494:pharmacology*; D011897:Random Allocation; D000077208:Remifentanil
D000701:Analgesics, Opioid; D010880:Piperidines; D000077208:Remifentanil