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- Author or Editor: Sathya K. Chinnadurai x
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Objective—To determine the accuracy of a noninvasive oscillometric monitor in the measurement of arterial blood pressure in anesthetized boid snakes.
Animals—4 boa constrictors (Boa constrictor), 2 carpet pythons (Morelia spilota), and 2 reticulated pythons (Python reticulatus).
Procedures—After induction of anesthesia with isoflurane, each snake was instrumented with an arterial catheter connected to a pressure transducer and oscilloscope to obtain invasive measurements of systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressure as well as a pressure waveform. A cuff connected to an oscillometric device was placed on the tail immediately distal to the vent for noninvasive measurements. Heart rate, respiratory rate, and invasive and noninvasive measurements of SAP, DAP, and MAP were obtained every 5 minutes for 45 minutes. Delivered isoflurane concentration was increased in 15-minute increments to induce hypotension. Repeatability of each device and fixed and proportional biases between devices were calculated.
Results—Throughout most of the measured ranges of blood pressures, the oscillometric unit overestimated the SAP and underestimated the DAP and MAP, compared with respective direct measurements. When the invasively determined SAP was > 100 mm Hg, the oscillometric unit underestimated all 3 variables. Fixed bias was significant for SAP and DAP, and proportional bias was significant for SAP and MAP.
Conclusions and Clinical Relevance—When using an oscillometric blood pressure monitor on anesthetized boid snakes, veterinarians can potentially monitor changes in blood pressure, although the displayed readings may underestimate DAP and MAP and overestimate SAP. Indirect measurements of blood pressure made with the oscillometric device cannot substitute for direct measurements.
OBJECTIVE To evaluate the anesthetic and cardiorespiratory effects of IM alfaxalone and isoflurane administration in budgerigars (Melopsittacus undulatus) and compare use of these agents with use of manual restraint.
ANIMALS 42 healthy budgerigars.
PROCEDURES For dose comparison, birds received alfaxalone (5 or 10 mg/kg [2.27 or 4.54 mg/lb], IM; groups A5 and A10, respectively; n = 6/group). For treatment comparison, birds received alfaxalone (10 mg/kg, IM) or isoflurane (via face mask) or were manually restrained (groups A, I, and M, respectively; n = 10/group). Data were obtained on onset, degree, and duration of sedation or anesthesia; heart and respiratory rates; and recovery times. Birds in the treatment comparison underwent physical examination and blood gas analysis.
RESULTS All group A5 birds became sedate, but not recumbent. In group A10, 5 of 6 birds lost the righting reflex; however, none lost the noxious stimulus response. Median time to initial effects was significantly shorter and mean time to complete recovery was significantly longer in group A10 than in group A5. Heart and respiratory rates in group A10 remained clinically acceptable; however, some birds had signs of excitement during induction and recovery. Times to initial effects, recumbency, and complete recovery were significantly longer, yet clinically practical, in group A than in group I. Plasma lactate concentrations were significantly higher in group M than in groups A and I.
CONCLUSIONS AND CLINICAL RELEVANCE Alfaxalone administered IM at 10 mg/kg produced effective sedation in healthy budgerigars and may be a viable alternative to isoflurane and manual restraint for brief, minimally invasive procedures. Brief manual restraint resulted in a significant increase in plasma lactate concentration.
CASE DESCRIPTION 2 female red-necked wallabies (Macropus rufogriseus) were evaluated because of sudden-onset mandibular swelling, ptyalism, and hyporexia.
CLINICAL FINDINGS Physical examination revealed a mandibular swelling with a fluctuant center in both wallabies. Hematologic analysis revealed leukocytosis with a mature neutrophilia and monocytosis in one wallaby (case 1) and a slight neutrophilia, hyperglobulinemia, and high serum alanine aminotransferase activity in the other (case 2). Cytologic examination of the swelling revealed a uniform population of gram-negative rods in case 1 and neutrophilic inflammation in case 2. Radiography revealed a soft tissue mandibular swelling with osteolucency around mandibular incisor roots in both wallabies. Computed tomography revealed changes consistent with chronic active mandibular osteomyelitis and reactive bone formation, but also sequestra formation not appreciable via radiography.
TREATMENT AND OUTCOME Long-term antimicrobial treatment was initiated with clindamycin (17 to 21 mg/kg [7.7 to 9.5 mg/lb], IV, q 12 h for 40 to 55 days) and high-dose benzathine penicillin G (80,000 U/kg [36,364 U/lb], SC, q 12 h for 150 days). Serial CT was performed to evaluate response to treatment and resolution of disease. A CT scan 18 months after the initial evaluation revealed complete resolution of osteomyelitis and sequestra.
CLINICAL RELEVANCE Advanced imaging and long-term treatment and management were integral to the successful outcome for these wallabies, given that the osseous changes visible on CT images were not visible on standard radiographs, guiding therapeutic decision-making. This report provides new therapeutic and diagnostic monitoring information to assist clinicians with similar cases.
To characterize induction and recovery characteristics of 3 commonly used inhalant anesthetics in prairie rattlesnakes (Crotalus viridis): isoflurane, sevoflurane, and desflurane.
12 healthy adult prairie rattlesnakes.
In a randomized crossover design, snakes underwent anesthetic induction with 5% isoflurane, 8% sevoflurane, or 18% desflurane, with a washout period of ≥ 7 days between anesthetic events. Anesthetic depth parameters were recorded throughout induction and recovery, including time to loss and return of righting reflex, muscle tone, ability to intubate, response to pressure, and time to return to spontaneous respiration. Every 5 minutes throughout the anesthetic procedures, heart rate, respiratory rate, and percentage expired anesthetic gas were recorded.
No snakes died during the study. Sevoflurane anesthesia resulted in anesthetic gas avoidance behavior in snakes during induction and had the significantly longest recovery time to extubation and time to return of pressure response, compared with the other inhalant anesthetics. Anesthesia with isoflurane resulted in a significantly longer time to return of righting reflex, compared with sevoflurane or desflurane. No significant difference was noted in time to loss of pressure response among the 3 anesthetic gases. Desflurane anesthesia resulted in the significantly quickest loss of righting reflex among the anesthetic protocols; despite this, 4 of 12 desflurane anesthetized snakes did not achieve an anesthetic plane deep enough for intubation.
CONCLUSIONS AND CLINICAL RELEVANCE
Isoflurane and sevoflurane, but not desflurane, inhalation anesthesia resulted in consistent and predictable loss of righting reflex and induction of anesthesia deep enough to allow intubation in snakes.
Bearded dragons (Pogona vitticeps), a popular zoological companion species, frequently require sedation for procedures. A novel formulation of alfaxalone with preservatives was FDA approved for 28-day use after the vial is breached. Research has been performed in squamate species using alfaxalone without preservatives at various doses and routes of administration, but it is unknown whether preservatives affect quality of sedation or cardiac function.
10 bearded dragons.
This complete crossover study evaluated the pharmacodynamic effects of alfaxalone with preservatives administered to bearded dragons via intracoelomic (ICo; n = 10), SC (10), IM (9), and IV (9) injection at 15 mg/kg.
Deep sedation was achieved in 9 of 10 ICo, 8 of 10 SC, 8 of 9 IM, and 9 of 9 IV administrations. Heart rate significantly decreased from baseline for ICo (P = .008; median heart rate, 46), IM (P = .018; 54), and IV (P = .033; 54) routes, but maintained within clinically acceptable limits. Respiratory rate significantly decreased from baseline for ICo (P = .011; median respiratory rate, 30), SC (P = .024; 12), IM (P = .028; 12), and IV (P = .043; 12) routes. Spontaneous ventilation was retained during all events. Time to first effects was significantly sooner with IV (0 min) administration compared with ICo (P = .02; 5 min) and IM (P = .008; 5 min). Time to loss and recovery of withdrawal, righting reflex, deep pain, and purposeful movement were not significantly different between routes of administration. End-systolic volume was the only echocardiographic parameter significantly affected by IV sedation.
Sedation quality was most consistent via IV administration at 15 mg/kg, and minimal changes in cardiac function were observed.
OBJECTIVE: To determine the intracoelemic (ICe) dose of alfaxalone required to induce loss of righting reflex (LRR) in garter snakes (Thamnophis sirtalis) and to evaluate the tactile stimulus response in unanesthetized and alfaxalone-anesthetized snakes.
ANIMALS: 8 healthy mature garter snakes.
PROCEDURES: During the first of 3 phases, snakes received each of 3 doses (10, 20, and 30 mg/kg) of alfaxalone, ICe, with a 2-week washout period between treatments. Times to LRR and return of righting reflex were determined after each dose. During phase 2, unanesthetized snakes underwent tactile stimulation testing with Semmes-Weinstein monofilaments once daily for 3 consecutive days to determine the baseline tactile pressure required to elicit purposeful movement. During phase 3, snakes were anesthetized with alfaxalone (30 mg/kg, ICe), and the tactile pressure required to induce purposeful movement was assessed at predetermined times after LRR.
RESULTS: Intracoelomic administration of alfaxalone at doses of 10, 20, and 30 mg/kg induced LRR in 0, 5, and 8 snakes, respectively. For snakes with LRR, median time to LRR following the 30-mg/kg dose (3.8 minutes) was significantly shorter than that following the 20-mg/kg dose (8.3 minutes); median time to return of righting reflex did not differ between the 2 doses. Mean ± SD tactile pressure that resulted in purposeful movement in unanesthetized snakes was 16.9 ± 14.3 g. When snakes were anesthetized, the mean tactile pressure that resulted in purposeful movement was significantly increased from baseline at 10, 20, and 30 minutes after LRR.
CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested ICe administration of alfaxalone might be effective for anesthetizing garter snakes.