OBJECTIVE To evaluate the effects of providing 100% O2, compared with provision of room air, in sedated spontaneously breathing inland bearded dragons (Pogona vitticeps). ANIMALS 8 adult bearded dragons. PROCEDURES Animals were sedated with alfaxalone (20 mg/kg, SC) and received 21% O2 (equivalent to room air) or 100% O2 via face mask (flow rate, 1 L/min) in a randomized, blinded, complete crossover study (2-week interval between treatments). Sedation variables, cardiopulmonary variables, venous blood gas values, and postsedation food intake were evaluated. RESULTS Respiratory rate, heart rate, oxygen saturation, and sedation quality were comparable between treatments. Venous blood gas analysis revealed a higher total Pco2 and HCO3− concentration for the 21% O2 treatment. Postsedation food intake was not affected by the inspired oxygen fraction provided during sedation. CONCLUSIONS AND CLINICAL RELEVANCE The fraction of inspired oxygen did not appear to have clinically relevant effects on physiologic variables of bearded dragons during and after sedation. Therefore, provision of 100% O2 can be considered for use in sedated bearded dragons without the risk of inducing hypoventilation. Similarly, failure to provide 100% O2 would be unlikely to result in clinically relevant consequences in healthy sedated bearded dragons.

OBJECTIVE To determine the minimum alveolar concentration of desflurane (MACDES) and effects on cardiovascular variables in positive-pressure ventilated sheep. ANIMALS 13 adult female sheep. PROCEDURES Anesthesia was induced with desflurane. After a 30-minute equilibration at an end-tidal concentration of desflurane (etDES) of 10.5%, an electrical stimulus (5 Hz/ms and 50 mA) was applied for 1 minute or until gross purposeful movement occurred. The etDES was then changed by 0.5% (modified up-down method), depending on whether a positive motor response had been elicited, and stimulation was repeated. The MACDES was the etDES midway between a positive and negative response. After MACDES was determined, etDES was increased to 1.3 and 1.6 MACDES. Animals were allowed to equilibrate for 15 minutes, and cardiovascular, blood gas, acid-base, and hematologic variables were measured. Times to induction of anesthesia, extubation, attainment of sternal position, and standing and duration of anesthesia were recorded. RESULTS Mean ± SD MACDES was 9.81 ± 0.79%. Times to intubation, extubation, and standing were 4.81 ± 2.21 minutes, 14.09 ± 4.05 minutes, and 32.4 ± 12.5 minutes, respectively. Duration of anesthesia was 226 ± 22 minutes. Heart rate increased significantly at induction of anesthesia but otherwise remained at preanesthetic rates. Arterial blood pressures progressively decreased with increasing etDES; pressures increased slightly only in response to noxious stimulation. CONCLUSIONS AND CLINICAL RELEVANCE The MACDES determined here compared favorably with that determined for other sheep populations and indicated similar anesthetic potency as in other species. Desflurane caused dose-dependent arterial hypotension, which indicated the need for careful blood pressure monitoring.

OBJECTIVE To evaluate hemodynamic, respiratory, and sedative effects of buccally administered detomidine gel and reversal with atipamezole in dogs. ANIMALS 8 adult purpose-bred dogs. PROCEDURES Arterial and venous catheters were placed. Baseline heart rate, respiratory rate, cardiac output (determined via lithium dilution with pulse contour analysis), oxygen delivery, systemic vascular resistance, arterial blood gas values, and sedation score were obtained. Detomidine gel (2.0 mg/m2) was administered on the buccal mucosa. Cardiopulmonary data and sedation scores were obtained at predetermined times over 180 minutes. Atipamezole (0.1 mg/kg) was administered IM at 150 minutes. Reversal of sedation was timed and scored. Data were analyzed with an ANOVA. RESULTS Compared with baseline values, heart rate was lower at 45 to 150 minutes, cardiac output and oxygen delivery were lower at 30 to 150 minutes, and systemic vascular resistance was increased at 30 to 150 minutes. There were no significant changes in Paco2, Pao2, or lactate concentration at any time point, compared with baseline values, except for lactate concentration at 180 minutes. All dogs became sedated; maximum sedation was detected 75 minutes after administration of detomidine. Mean ± SD time to recovery after atipamezole administration was 7.55 ± 1.89 minutes; sedation was completely reversed in all dogs. No adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE Buccally administered detomidine gel was associated with reliable and reversible sedation in dogs, with hemodynamic effects similar to those induced by other α2-adrenoceptor agonists. Buccally administered detomidine gel could be an alternative to injectable sedatives in healthy dogs.

OBJECTIVE To assess pulmonary hemodynamics and alveolar oxygenation in dogs anesthetized with propofol or isoflurane during one-lung ventilation (OLV) in a closed-thoracic experimental model. ANIMALS 6 healthy Beagles. PROCEDURES Dogs were anesthetized with each of 3 protocols (constant rate IV infusion of propofol [0.4 to 1.0 mg/kg/min], isoflurane at the minimum alveolar concentration [MAC], and isoflurane 1.5 MAC), with a 7-day washout period between anesthetic sessions. During each session, dogs were intubated with a double-lumen endotracheal tube, positioned in right lateral recumbency, and administered atracurium (0.1 to 0.2 mg/kg, IV, q 30 min) to allow mechanical ventilation throughout a 2-hour observation period. Dogs underwent two-lung ventilation for 30 minutes, OLV of the right lung for 1 hour, and two-lung ventilation for another 30 minutes. Pulmonary hemodynamic and blood gas variables were evaluated at predetermined times and compared among protocols and over time within each protocol. RESULTS Alveolar oxygenation was not impaired, and mean heart rate and pulmonary artery pressure and occlusion pressure were similar among the 3 protocols. One-lung ventilation caused a significant increase in the arteriovenous shunt fraction only when dogs were anesthetized with isoflurane at 1.5 MAC. Dogs developed respiratory acidosis, which was exacerbated by OLV, during all anesthetic sessions. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated pulmonary hemodynamics and alveolar oxygenation during OLV in a closed-thoracic model were similar regardless of whether dogs were anesthetized with propofol or isoflurane. One-lung ventilation can be successfully performed in dogs by use of a double-lumen endotracheal tube and either propofol or isoflurane.

OBJECTIVE To characterize the maternal and fetal cardiopulmonary effects of a low-dose infusion of dexmedetomidine without a loading dose in pregnant ewes anesthetized with sevoflurane. ANIMALS 11 pregnant ewes. PROCEDURES Anesthesia was induced with propofol and maintained with sevoflurane. Ewes and fetuses were instrumented with arterial and venous catheters, and thermodilution–pulmonary arterial catheters were placed in the ewes. Baseline measurements were obtained at an end-tidal sevoflurane concentration of 3.4%, then dexmedetomidine (2 μg/kg/h, IV) was infused for 90 minutes without a loading dose. Cardiovascular and blood gas variables were measured at predetermined time points. RESULTS Dexmedetomidine infusion resulted in approximately 30% decreases in maternal systemic vascular resistance, blood pressure, and heart rate. Maternal cardiac index, oxygenation variables, and acid-base status remained unchanged, whereas pulmonary arterial pressure, pulmonary vascular resistance, and stroke volume increased, compared with baseline values. Uterine blood flow decreased by approximately 30% to 36%. Fetal heart rate and blood pressure remained unchanged, but significant increases in fetal plasma glucose and lactate concentrations were detected. CONCLUSIONS AND CLINICAL RELEVANCE Pregnant ewes receiving a combination of sevoflurane and an infusion of dexmedetomidine without a loading dose had cardiac index in acceptable ranges and maintained normoxia. This balanced anesthesia did not produce significant changes in fetal blood pressure or heart rate. However, the increase in fetal plasma lactate concentration and changes in maternal pulmonary vascular resistance and uterine blood flow require further investigation to better elucidate these effects.

Somatosensory evoked potentials (SSEP) are used to monitor sensory function and are often recorded under general anesthesia. The objective of the study was to evaluate the effects of isoflurane on SSEPs in calves as it has not been reported. Eight calves (mean age: 40 days), were included in the study. Calves were anesthetized with a randomized sequence of four different isoflurane partial pressures. Blood gas analysis was performed before each measurement. SSEP were induced by repeated stimulation of the common dorsal digital nerve III. SSEPs were recorded from the lumbo-sacral junction (s-SSEP) and the head (c-SSEP). Latency and inter-amplitude of each peak were measured. For s-SSEP: One negative (Nsp1) and two positive (Psp1 and Psp2) peaks were identified in all tracings except for two calves. There was a significant effect of isoflurane on the latency of Psp2 (P = 0.01). Inter-amplitude decreased significantly with PaO2, PaCO2 and temperature (P < 0.05). Psp2 latency decreased with PaO2 (P = 0.01). For c-SSEP: two positive (Pc1 and Pc2) and two negative (Nc1 and Nc2) peaks were identified. There were identifiable peaks for the analysis of Pc1 latencies only. There was a significant positive linear relation between end-tidal isoflurane partial pressure (ETiso) and Pc1 latency (P = 0.04). None of the co-variables had a significant effect on the latency of Pc1 (P > 0.1). Isoflurane has a major impact on the recording of c-SSEP. Recording should be done at the lowest ETiso as possible, and anesthesia parameters should be kept constant.