Cardiovascular effects of equipotent isoflurane and alfentanil/isoflurane minimum alveolar concentration multiple in cats.
OBJECTIVE
To determine whether administration of opioids to anesthetized cats induced less cardiovascular depression than that induced by an equivalent amount of anesthetic alone, and to measure endocrine responses to a noxious stimulus.


METHODS
6 healthy female cats.


METHODS
Anesthesia was induced with isoflurane and was maintained for 60 minutes at 1.3 isoflurane MAC. Blood gas tensions, pH, and plasma alfentanil and hormone concentrations, blood pressures, and cardiac output were measured. A noxious stimulus was applied for 5 minutes, while blood acquisition and measurements were repeated. Alfentanil was administered i.v. to achieve estimated plasma concentration of 500 ng/ml, and end-tidal isoflurane concentration was reduced by 35%. After another 60 minutes, blood was obtained and measurements were taken, then a second 5-minute noxious stimulus was applied while blood acquisition and measurements were retaken.


RESULTS
Alfentanil administration and reduction of isoflurane concentration significantly increased body temperature, heart rate, mean arterial pressure, mean pulmonary arterial pressure, stroke index, cardiac index, hemoglobin, oxygen delivery index, PvO2 and PvCO2, dopamine, epinephrine (EPI), norepinephrine (NOREPI), and cortisol values, and significantly decreased arterial and venous pH. Application of a noxious stimulus significantly increased heart rate, stroke index, cardiac index, PaO2, oxygen delivery index, arterial and venous pH, and NOREPI values, and decreased bicarbonate, PaCO2, PvCO2, and EPI values. Alfentanil administration blunted cardiac index, PaCO2, oxygen delivery index, arterial pH, PaO2, and EPI, and NOREPI responses to a noxious stimulus.


CONCLUSIONS
Compared with isoflurane alone, alfentanil administration and reduction of isoflurane MAC improved cardiovascular variables, and blunted respiratory, hormonal, and most hemodynamic responses to a noxious stimulus in cats.


CONCLUSIONS
Use of the balanced opioid anesthesia regimen induced some beneficial effects in healthy cats; effects were similar to, although greater in nature, than effects induced by a noxious stimulus.
Pascoe
P J
PJ
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis 95616, USA.
Ilkiw
J E
JE
Fisher
L D
LD
D000136:Acid-Base Equilibrium; D015760:Alfentanil / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates / Q000097:blood; D001784:Blood Gas Analysis / Q000662:veterinary; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood; D002415:Cats / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004347:Drug Interactions; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006454:Hemoglobins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007530:Isoflurane / Q000008:administration & dosage / Q000032:analysis / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011650:Pulmonary Alveoli / Q000737:chemistry*; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D001639:Bicarbonates; D002395:Catecholamines; D004338:Drug Combinations; D006454:Hemoglobins; D015760:Alfentanil; D007530:Isoflurane