Effects of fentanyl on isoflurane minimum alveolar concentration in New Zealand White rabbits (Oryctolagus cuniculus)

Barter, Linda S; Hawkins, Michelle G.; Pypendop, Bruno H.

doi:10.2460/ajvr.76.2.111

Cited by 12 publications

(6 citation statements)

References 13 publications

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“…We achieved this by increasing the end-tidal isoflurane concentration to 1.3X that of the individual rabbit at MAC without adjusting the dose of fentanyl used to achieve each targeted plasma concentration. Interestingly, in that same study, 8 the measured plasma concentrations of fentanyl were approximately half of the targeted values. In that study, 8 plasma fentanyl concentrations of 36 ng/mL were associated with excessive spontaneous movement and rigidity, limiting the clinical benefit of fentanyl doses to achieve that concentration.…”

Section: Discussionmentioning

confidence: 83%

“…The targeted plasma fentanyl concentrations were selected as those with the most clinical promise on the basis of results of a previous study 8 in New Zealand White rabbits, which was performed in our laboratory. We achieved this by increasing the end-tidal isoflurane concentration to 1.3X that of the individual rabbit at MAC without adjusting the dose of fentanyl used to achieve each targeted plasma concentration.…”

Section: Discussionmentioning

confidence: 99%

“…In the first experiment, MAC was determined in duplicate for each isoflurane-anesthetized rabbit prior to administration of fentanyl (ie, baseline) and at 3 targeted plasma fentanyl concentrations (4,8, and 16 ng/mL, determined on the basis of results of a previous study 8 ). In the first experiment, MAC was determined in duplicate for each isoflurane-anesthetized rabbit prior to administration of fentanyl (ie, baseline) and at 3 targeted plasma fentanyl concentrations (4,8, and 16 ng/mL, determined on the basis of results of a previous study 8 ).…”

Section: Methodsmentioning

confidence: 99%

“…8 For this pharmacokinetic model, volume of the central compartment was 581 mL/kg and clearance was 80.2 mL/kg/min. e On the basis of unpublished pharmacokinetic data obtained previously by our laboratory regarding fentanyl in isoflurane-anesthetized rabbits, this system rapidly loaded the central compartment to the targeted concentration and updated the infusion rate every 10 seconds to maintain a pseudo-steady-state plasma concentration as previously described.…”

Section: Fentanyl Infusion Schemementioning

confidence: 99%

“…This was performed once at baseline and twice for each targeted plasma concentration (4,8, and 16 ng/mL): the first sample was obtained 15 minutes after starting the fentanyl infusion, and the second was collected at the time of the second MAC determination for each targeted plasma concentration. The end-tidal isoflurane concentration was increased by 10% if movement occurred or decreased by 10% if movement did not occur, and another 15-minute period of stable end-tidal isoflurane concentration was allowed prior to reapplication of the stimulus.…”

Section: Mac Determinationmentioning

confidence: 99%

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Cardiovascular effects of equipotent doses of isoflurane alone and isoflurane plus fentanyl in New Zealand White rabbits (Oryctolagus cuniculus)

Tearney

Barter

Pypendop

2015

ajvr

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OBJECTIVE To determine effects of equipotent concentrations of fentanyl and isoflurane, compared with isoflurane alone, on cardiovascular variables in New Zealand White rabbits (Oryctolagus cuniculus). ANIMALS 6 adult female New Zealand White rabbits. PROCEDURES Rabbits were anesthetized with isoflurane, and lungs were mechanically ventilated. The minimum alveolar concentration (MAC) of isoflurane alone (baseline) and with fentanyl administered IV to achieve 3 targeted plasma concentrations was determined for each rabbit by means of an electrical stimulus. Cardiovascular variables were measured in a separate experiment at 1.3X isoflurane MAC and equipotent doses of isoflurane plus fentanyl at the same 3 targeted plasma concentrations. Blood samples were collected for measurement of blood gas variables and plasma fentanyl concentrations. Treatment effects were evaluated by repeated-measures ANOVA followed by 2-tailed paired t tests with sequentially rejective Bonferroni correction. RESULTS Mean ± SD MAC of isoflurane was 1.95 ± 0.27%. Mean measured plasma fentanyl concentrations of 4.97, 8.93, and 17.19 ng/mL reduced isoflurane MAC by 17%, 37%, and 56%, respectively. Mean measured plasma fentanyl concentrations during cardiovascular measurements were 5.49, 10.26, and 18.40 ng/mL. Compared with baseline measurements, heart rate was significantly lower at all 3 plasma fentanyl concentrations, mean arterial blood pressure and systemic vascular resistance were significantly higher at mean fentanyl concentrations of 10.26 and 18.40 ng/mL, and cardiac output was significantly higher at 18.40 ng of fentanyl/mL. CONCLUSIONS AND CLINICAL RELEVANCE Administration of fentanyl in isoflurane-anesthetized rabbits resulted in improved mean arterial blood pressure and cardiac output, compared with isoflurane alone. This balanced anesthesia technique may prove useful in the management of clinical cases in this species.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%