Objective—To determine selected cardiopulmonary values and baroreceptor response in conscious green iguanas (Iguana iguana) and to evaluate the use of blood gas analysis and pulse oximetry in this species. Animals—15 healthy juvenile green iguanas. Procedures—Baseline cardiopulmonary values were determined in 15 conscious iguanas breathing room air. Effects of 100% O2 inspiration were also measured (n = 6), and the baroreceptor reflex was characterized by exponential sigmoidal curve fitting analysis. Results—Conscious iguanas had a mean ± SD resting heart rate of 52 ± 8 beats/min, respiratory rate of 28 ± 6 breaths/min, and systolic, mean, and diastolic arterial blood pressures of 69 ± 10 mm Hg, 62 ± 12 mm Hg, and 56 ± 13 mm Hg, respectively. Mean arterial pH at 37°C was 7.29 ± 0.11, Pao2 was 81 ± 10 mm Hg, and Paco2 was 42 ± 9 mm Hg; corrected for a body temperature of 30°C, mean arterial pH at 37°C was 7.382 ±0.12, Pao2 was 54 ± 15 mm Hg, and Paco2 was 32 ± 7 mm Hg. Inspiration of 100% O2 did not change heart and respiratory rates but increased Pao2 to 486 ± 105 mm Hg (corrected value, 437 ± 96 mm Hg). A baroreceptor reflex was evident, with mean heart rates ranging from 30 ± 3 beats/min to 63 ± 5 beats/min and mean arterial blood pressures ranging from 42 ± 3 mm Hg to 58 ± 3 mm Hg. Conclusions and Clinical Relevance—This study provided needed information on cardiopulmonary values in healthy green iguanas, the application and limitation of arterial and venous blood gas analysis, and the accuracy of pulse oximetry.

Objective-To assess the accuracy of isoflurane, halothane, and sevoflurane vaporizers during high oxygen flow and at maximum dial settings at room temperature and to test sevoflurane vaporizers similarly during heating and at low-fill states. Sample-5 isoflurane, 5 halothane, and 5 sevoflurane vaporizers. Procedures-Vaporizers were tested at an oxygen flow of 10 L/min and maximum dial settings for 15 minutes under various conditions. All 3 vaporizer types were filled and tested at room temperature (21 degrees to 23 degrees C). Filled sevoflurane vaporizers were wrapped with circulating hot water (42 degrees C) blankets for 2 hours and tested similarly, and near-empty sevoflurane vaporizers were tested similarly at room temperature. During each 15-minute test period, anesthetic agent concentration was measured at the common gas outlet with a portable refractometer and temperature of the vaporizer wall was measured with a thermistor. Results-For each vaporizer type, anesthetic agent concentrations and vaporizer wall temperatures decreased during the 15-minute test period. Accuracy of isoflurane and halothane vaporizers remained within the recommended 20% (plus or minus) deviation from dial settings. Heated and room-temperature sevoflurane vaporizers were accurate to within 23% and 11.7% (plus or minus) of dial settings, respectively. Sevoflurane vaporizers at low-fill states performed similarly to vaporizers at full-fill states. Conclusions and Clinical Relevance-Under these study conditions, the isoflurane and halothane vaporizer models tested were accurate but the sevoflurane vaporizers were not. Sevoflurane vaporizer accuracy was not affected by fill state but may be improved with vaporizer heating; measurements of inspired anesthetic agent concentrations should be obtained during the use of heated vaporizers.

Objective—To determine effects of a continuous rate infusion of lidocaine on the minimum alveolar concentration (MAC) of sevoflurane in horses. Animals—8 healthy adult horses. Procedures—Horses were anesthetized via IV administration of xylazine, ketamine, and diazepam; anesthesia was maintained with sevoflurane in oxygen. Approximately 1 hour after induction, sevoflurane MAC determination was initiated via standard techniques. Following sevoflurane MAC determination, lidocaine was administered as a bolus (1.3 mg/kg, IV, over 15 minutes), followed by constant rate infusion at 50 μg/kg/min. Determination of MAC for the lidocaine-sevoflurane combination was started 30 minutes after lidocaine infusion was initiated. Arterial blood samples were collected after the lidocaine bolus, at 30-minute intervals, and at the end of the infusion for measurement of plasma lidocaine concentrations. Results—IV administration of lidocaine decreased mean ± SD sevoflurane MAC from 2.42 ± 0.24% to 1.78 ± 0.38% (mean MAC reduction, 26.7 ± 12%). Plasma lidocaine concentrations were 2,589 ± 811 ng/mL at the end of the bolus; 2,065 ± 441 ng/mL, 2,243 ± 699 ng/mL, 2,168 ± 339 ng/mL, and 2,254 ± 215 ng/mL at 30, 60, 90, and 120 minutes of infusion, respectively; and 2,206 ± 329 ng/mL at the end of the infusion. Plasma concentrations did not differ significantly among time points. Conclusions and Clinical Relevance—Lidocaine could be useful for providing a more balanced anesthetic technique in horses. A detailed cardiovascular study on the effects of IV infusion of lidocaine during anesthesia with sevoflurane is required before this combination can be recommended.

Objective: To evaluate effects of racemic ketamine and S-ketamine in gazelles. Animals: 21 male gazelles (10 Rheem gazelles [Gazella subgutturosa marica] and 11 Subgutturosa gazelles [Gazella subgutturosa subgutturosa]), 6 to 67 months old and weighing (mean±SD) 19 ± 3 kg. Procedures: In a randomized, blinded crossover study, a combination of medetomidine (80 μg/kg) with racemic ketamine (5 mg/kg) or S-ketamine (3 mg/kg) was administered IM. Heart rate, blood pressure, respiratory rate, rectal temperature, and oxygen saturation (determined by means of pulse oximetry) were measured. An evaluator timed and scored induction of, maintenance of, and recovery from anesthesia. Medetomidine was reversed with atipamezole. The alternate combination was used after a 4-day interval. Comparisons between groups were performed with Wilcoxon signed rank and paired t tests. Results: Anesthesia induction was poor in 2 gazelles receiving S-ketamine, but other phases of anesthesia were uneventful. A dominant male required an additional dose of S-ketamine (0.75 mg/kg, IM). After administration of atipamezole, gazelles were uncoordinated for a significantly shorter period with S-ketamine than with racemic ketamine. Recovery quality was poor in 3 gazelles with racemic ketamine. No significant differences between treatments were found for any other variables. Time from drug administration to antagonism was similar between racemic ketamine (44.5 to 53.0 minutes) and S-ketamine (44.0 to 50.0 minutes). Conclusions and Clinical Relevance: Administration of S-ketamine at a dose 60% that of racemic ketamine resulted in poorer induction of anesthesia, an analogous degree of sedation, and better recovery from anesthesia in gazelles with unremarkable alterations in physiologic variables, compared with racemic ketamine.

Objective—To directly assess microcirculatory changes associated with induced hemorrhagic shock by use of sidestream dark field microscopy (SDM) and correlate those values with concurrently measured macrovascular and blood gas variables in healthy anesthetized dogs. Animals—12 adult dogs. Procedures—Dogs were anesthetized and splenectomized. Instrumentation and catheterization were performed for determination of macrohemodynamic and blood gas variables. Hemorrhagic shock was induced via controlled hemorrhage to a mean arterial blood pressure (MAP) of 40 mm Hg. Dogs were maintained in the shock state (MAP, 35 to 45 mm Hg) for 60 minutes. An SDM device was used to image microcirculation of buccal mucosa, and vascular analysis software was used to determine microcirculatory variables. These values were compared with other cardiovascular and blood gas variables to determine correlations. Results—Following hemorrhage, there was a significant decrease in microvascular variables (mean ± SD), including proportion of perfused vessels (82.77 ± 8.32% vs 57.21 ± 28.83%), perfused vessel density (14.86 ± 2.64 mm/m2 vs 6.66 ± 4.75 mm/m2), and microvascular flow index (2.54 ± 0.52 vs 1.59 ± 0.85). Perfused vessel density individually correlated well with macrovascular variables, with heart rate (zero order, partial correlation, and part correlation coefficients = −0.762, −0.884, and −0.793, respectively) and oxygen extraction ratio (−0.734, −0.832, and −0.746, respectively) being the most important predictors. Conclusions and Clinical Relevance—SDM allowed real-time imaging of the microvasculature and has potential as an effective tool in experimental and clinical applications for monitoring microcirculatory changes associated with hemorrhagic shock and resuscitation in dogs.

This study established a disease model and protocol for bacterial challenge with Escherichia coli serogroup O2 strain EC317 in Japanese quail. Five groups of 10 birds each were injected subcutaneously in the breast with 200 μL of a brain–heart infusion (BHI) culture containing 1 × 10(8), 1 × 10(7), 1 × 10(6), 1 × 10(5), or 1 × 10(4) colony-forming units/mL of the test organism, which had been isolated from a turkey with cellulitis and septicemia. Birds in a 6th group were controls that received sterile BHI alone. Localized lesions of cellulitis developed in all of the birds that received E. coli. The morbidity and mortality rates were highest (100%) in the birds receiving the highest dose of E. coli and decreased linearly with decreasing dose (P < 0.05). Severity of disease, including lesions of pericarditis and perihepatitis, was also directly proportional to the dose of E. coli. These findings indicate that this disease challenge protocol can be used to study disease resistance and immunologic consequences of contaminant exposure or other stressors in birds.

Objective—To compare cardiovascular effects of sevoflurane alone and sevoflurane plus an IV infusion of lidocaine in horses. Animals—8 adult horses. Procedures—Each horse was anesthetized twice via IV administration of xylazine, diazepam, and ketamine. During 1 anesthetic episode, anesthesia was maintained by administration of sevoflurane in oxygen at 1.0 and 1.5 times the minimum alveolar concentration (MAC). During the other episode, anesthesia was maintained at the same MAC multiples via a reduced concentration of sevoflurane plus an IV infusion of lidocaine. Heart rate, arterial blood pressures, blood gas analyses, and cardiac output were measured during mechanical (controlled) ventilation at both 1.0 and 1.5 MAC for each anesthetic protocol and during spontaneous ventilation at 1 of the 2 MAC multiples. Results—Cardiorespiratory variables did not differ significantly between anesthetic protocols. Blood pressures were highest at 1.0 MAC during spontaneous ventilation and lowest at 1.5 MAC during controlled ventilation for either anesthetic protocol. Cardiac output was significantly higher during 1.0 MAC than during 1.5 MAC for sevoflurane plus lidocaine but was not affected by anesthetic protocol or mode of ventilation. Clinically important hypotension was detected at 1.5 MAC for both anesthetic protocols. Conclusions and Clinical Relevance—Lidocaine infusion did not alter cardiorespiratory variables during anesthesia in horses, provided anesthetic depth was maintained constant. The IV administration of lidocaine to anesthetized nonstimulated horses should be used for reasons other than to improve cardiovascular performance. Severe hypotension can be expected in nonstimulated horses at 1.5 MAC sevoflurane, regardless of whether lidocaine is administered.

Objective: To determine the effectiveness of preinduction hyperbaric oxygen treatment (HBOT) in ameliorating signs of experimentally induced endotoxemia in horses. Animals: 18 healthy adult horses. Procedures: Horses were randomly assigned to 1 of 3 equal-sized treatment groups to receive normobaric ambient air and lipopolysaccharide (LPS), HBOT and LPS, or HBOT and physiologic saline (0.9% NaCl) solution. Horses were physically examined, and blood was obtained for a CBC and to determine concentration or activity of plasma tissue necrosis factor-α, blood lactate, and blood glucose before the horses were treated with HBOT and then intermittently for 6 hours after administration of LPS or physiologic saline solution. Results: All LPS-treated horses developed signs and biochemical and hematologic changes consistent with endotoxemia. Treatment with HBOT significantly ameliorated the effect of LPS on clinical endotoxemia score but did not significantly improve other abnormalities associated with endotoxemia. Conclusions and Clinical Relevance: The protective effect of HBOT was minimal, and results did not support its use as a treatment for horses prior to development of endotoxemia.

Objective—To assess agreement between anesthetic agent concentrations measured by use of an infrared anesthetic gas monitor (IAGM) and refractometry. Sample—4 IAGMs of the same type and 1 refractometer. Procedures—Mixtures of oxygen and isoflurane, sevoflurane, desflurane, or N2O were used. Agent volume percent was measured simultaneously with 4 IAGMs and a refractometer at the common gas outlet. Measurements obtained with each of the 4 IAGMs were compared with the corresponding refractometer measurements via the Bland-Altman method. Similarly, Bland-Altman plots were also created with either IAGM or refractometer measurements and desflurane vaporizer dial settings. Results—Bias ± 2 SD for comparisons of IAGM and refractometer measurements was as follows: isoflurane, −0.03 ± 0.18 volume percent; sevoflurane, −0.19 ± 0.23 volume percent; desflurane, 0.43 ± 1.22 volume percent; and N2O, −0.21 ± 1.88 volume percent. Bland-Altman plots comparing IAGM and refractometer measurements revealed nonlinear relationships for sevoflurane, desflurane, and N2O. Desflurane measurements were notably affected; bias ± limits of agreement (2 SD) were small (0.1 ± 0.22 volume percent) at < 12 volume percent, but both bias and limits of agreement increased at higher concentrations. Because IAGM measurements did not but refractometer measurements did agree with the desflurane vaporizer dial settings, infrared measurement technology was a suspected cause of the nonlinear relationships. Conclusions and Clinical Relevance—Given that the assumption of linearity is a cornerstone of anesthetic monitor calibration, this assumption should be confirmed before anesthetic monitors are used in experiments.