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  • Author or Editor: Craig A. E. Mosley x
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Abstract

Objective—To determine the cardiac anesthetic index (CAI) of isoflurane in green iguanas and whether butorphanol affected the CAI.

Design—Prospective randomized controlled trial.

Animals—7 healthy mature iguanas.

Procedure—In 5 iguanas, CAI was determined after induction of anesthesia with isoflurane alone, and in 5 iguanas, CAI was determined after induction of anesthesia with isoflurane and IM administration of butorphanol (1 mg/kg [0.45 mg/lb]). Three iguanas underwent both treatments. Animals were equilibrated for 20 minutes at 1.5 times the minimum alveolar concentration (MAC) of isoflurane and observed for evidence of cardiovascular arrest. If there was no evidence of cardiovascular arrest, end-tidal isoflurane concentration was increased by 20%, and animals were allowed to equilibrate for another 20 minutes. This process was repeated until cardiovascular arrest occurred or vaporizer output could no longer be consistently increased. The CAI was calculated by dividing the highest end-tidal isoflurane concentration by the MAC.

Results—None of the iguanas developed cardiovascular arrest and all survived. Mean ± SD highest endtidal isoflurane concentration during anesthesia with isoflurane alone (9.2 ± 0.60%) was not significantly different from mean concentration during anesthesia with isoflurane and butorphanol (9.0 ± 0.43%). The CAI was > 4.32.

Conclusions and Clinical Relevance—Results suggest that the CAI of isoflurane in green iguanas is > 4.32 and not affected by administration of butorphanol. Isoflurane appears to be a safe anesthetic in green iguanas. (J Am Vet Med Assoc 2003;222: 1565–1568)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine minimum alveolar concentration (MAC) of isoflurane in green iguanas and effects of butorphanol on MAC.

Design—Prospective randomized trial.

Animals—10 healthy mature iguanas.

Procedure—In each iguana, MAC was measured 3 times: twice after induction of anesthesia with isoflurane and once after induction of anesthesia with isoflurane and IM administration of butorphanol (1 mg/kg [0.45 mg/lb]). A blood sample was collected from the tail vein for blood-gas analysis at the beginning and end of the anesthetic period. The MAC was determined with a standard bracketing technique; an electrical current was used as the supramaximal stimulus. Animals were artificially ventilated with a ventilator set to deliver a tidal volume of 30 mL/kg (14 mL/lb) at a rate of 4 breaths/min.

Results—Mean ± SD MAC values during the 3 trials (2 without and 1 with butorphanol) were 2.0 ± 0.6, 2.1 ± 0.6, and 1.7 ± 0.7%, respectively, which were not significantly different from each other. Heart rate and end-tidal partial pressure of CO2 were also not significantly different among the 3 trials. Mean ± SD heart rate was 48 ± 10 beats/min; mean end-tidal partial pressure of CO2 was 22 ± 10 mm Hg. There were no significant differences in blood-gas values for samples obtained at the beginning versus the end of the anesthetic period.

Conclusions and Clinical Relevance—Results suggest that the MAC of isoflurane in green iguanas is 2.1% and that butorphanol does not have any significant isoflurane-sparing effects. (J Am Vet Med Assoc 2003;222:1559–1564)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare the effects of hetastarch and lactated Ringer's solution (LRS) on plasma colloid osmotic pressure (pCOP) and other hematologic variables in healthy llamas.

Design—Prospective crossover study.

Animals—6 healthy female llamas.

Procedures—Llamas were administered LRS (45 mL/kg [20.5 mL/lb]) and, after a 3-day washout period, hetastarch (15 mL/kg [6.8 mL/lb]) during 60-minute IV infusions. Serum total protein, serum albumin, and hemoglobin concentrations and Hct were measured before each infusion (baseline), immediately after each infusion was completed (0 hours), and at 2, 4, 8, and 12 hours. The pCOP was measured at baseline and at 0, 2, 4, 8, 12, 24, 36, and 48 hours after each infusion was completed; additional measurements of pCOP were obtained 72 and 96 hours after hetastarch infusion.

Results—Hetastarch administration significantly increased mean ± SEM pCOP from 23.5 ± 0.3 mm Hg (baseline) to a peak of 28.4 ± 0.6 mm Hg (12 hours); significant increases in pCOP persisted at 96 hours after hetastarch administration. Administration of LRS significantly decreased albumin and total protein concentrations; in addition, mean ± SEM pCOP decreased from 24.1 ± 0.4 mm Hg (baseline) to 18.0 ± 0.3 mm Hg (0 hours). Hetastarch administration caused more pronounced decreases in Hct (0 hours) and concentrations of hemoglobin (0 hours), albumin (all time points), and total protein (all time points) than did LRS administration.

Conclusions and Clinical Relevance—Hetastarch administration increased pCOP in healthy llamas for 96 hours with no clinically important complications.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine minimum alveolar concentration (MAC) of isoflurane in mechanically ventilated Dumeril monitors (Varanus dumerili).

Design—Prospective study.

Animals—10 healthy adult Dumeril monitors.

Procedure—Anesthesia was induced with isoflurane in oxygen delivered through a face mask. Monitors were endotracheally intubated, and end-tidal and inspired isoflurane concentrations were continuously measured. After equilibration at an end-tidal-toinspired isoflurane concentration ratio of > 0.9 for 20 minutes, an electrical stimulus (50 Hz, 50 V) was delivered to the ventral aspect of the tail for up to 1 minute and the monitor was observed for purposeful movement. End-tidal isoflurane concentration was then decreased by 10%, and equilibration and stimulation were repeated. The MAC was calculated as the mean of the lowest end-tidal isoflurane concentration that prevented positive response and the highest concentration that allowed response. A blood sample for blood gas analysis was collected from the tail vein at the beginning and end of the anesthetic period.

Results—Mean ± SD MAC of isoflurane was 1.54 ± 0.17%. Mean heart rates at the upper and lower MAC values were 32.4 ± 3 beats/min and 34 ± 4.5 beats/min, respectively. During the experiment, Paco2 decreased significantly from 43.1 mm Hg to 27.9 mm Hg and blood pH and HCO3 concentration increased significantly from 7.33 to 7.64 and from 25.3 to 32.9 mmol/L, respectively.

Conclusions and Clinical Relevance—The MAC of isoflurane in Dumeril monitors was similar to that reported in mammals but lower than values reported in other reptiles. This difference may be reflective of the more advanced cardiovascular physiologic features of monitor lizards. (J Am Vet Med Assoc 2005; 226:1098–1101)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the minimum alveolar concentration (MAC) of sevoflurane and assess the sevoflurane-sparing effect of coadministration of nitrous oxide in mechanically ventilated Dumeril monitors (Varanus dumerili).

Design—Prospective crossover study.

Animals—10 healthy adult Dumeril monitors.

Procedure—Anesthesia was induced with sevoflurane in 100% oxygen or sevoflurane in 66% nitrous oxide (N2O) with 34% oxygen, delivered through a face mask. Monitors were endotracheally intubated, and end-tidal and inspired isoflurane concentrations were measured continuously; MAC was determined by use of a standard bracketing technique. An electrical stimulus (50 Hz, 50 V) was delivered to the ventral aspect of the tail as the supramaximal stimulus. A blood sample for blood gas analyses was collected from the ventral coccygeal vessels at the beginning and end of the anesthetic period. An interval of at least 7 days was allowed to elapse between treatments.

Results—The MAC ± SDs of sevoflurane in oxygen and with N2O were 2.51 ± 0.46% and 1.83 ± 0.33%, respectively. There was a significant difference between the 2 treatments, and the mean MAC-reducing effect of N2O was 26.4 ± 11.4%. Assuming simple linear additivity of sevoflurane and N2O, the MAC for N2O was estimated to be 244%. No significant differences in blood gas values—with the predictable exception of oxygen pressure—were detected between the 2 groups.

Conclusions and Clinical Relevance—The MAC of sevoflurane in Dumeril monitors is similar to that reported for other species. The addition of N2O significantly decreased the MAC of sevoflurane in this species. (J Am Vet Med Assoc 2005;227:575–578)

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in Journal of the American Veterinary Medical Association