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- Author or Editor: Ann M. Hess x
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Abstract
OBJECTIVE
To evaluate the sedative and cardiopulmonary effects of various combinations of acepromazine, dexmedetomidine, hydromorphone, and glycopyrrolate, followed by anesthetic induction with propofol and maintenance with isoflurane in healthy dogs.
ANIMALS
6 healthy adult female Beagles.
PROCEDURES
Dogs were instrumented for hemodynamic measurements while anesthetized with isoflurane. Two hours after recovery, dogs received 1 of 4 IM combinations in a crossover design with 1 week between treatments: hydromorphone (0.1 mg/kg) and acepromazine (0.005 mg/kg; HA); hydromorphone and dexmedetomidine (0.0025 mg/kg; HD); hydromorphone, acepromazine, and dexmedetomidine (HAD); and hydromorphone, acepromazine, dexmedetomidine, and glycopyrrolate (0.02 mg/kg; HADG). Sedation was scored after 30 minutes. Physiologic variables and cardiac index were measured after sedation, after anesthetic induction with propofol, and every 15 minutes during maintenance of anesthesia with isoflurane for 60 minutes (target expired concentration at 760 mm Hg, 1.3%).
RESULTS
Sedation scores were not significantly different among treatments. Mean ± SD cardiac index was significantly higher for the HA (202 ± 45 mL/min/kg) and HADG (185 ± 59 mL/min/kg) treatments than for the HD (88 ± 31 mL/min/kg) and HAD (103 ± 25 mL/min/kg) treatments after sedation and through the first 15 minutes of isoflurane anesthesia. No ventricular arrhythmias were noted with any treatment.
CLINICAL RELEVANCE
In healthy dogs, IM administration of HADG before propofol and isoflurane anesthesia provided acceptable cardiopulmonary function with no adverse effects. This combination should be considered for routine anesthetic premedication in healthy dogs.
Abstract
OBJECTIVE
To compare IV doses of alfaxalone and ketamine needed to facilitate orotracheal intubation and assess effects of each treatment on selected physiologic variables in goats undergoing orthopedic surgery with isoflurane anesthesia.
ANIMALS
18 healthy adult goats.
PROCEDURES
Behavior was assessed before and after sedation with midazolam (0.1 mg/kg, IV) for IV catheter placement. Anesthesia was induced with additional midazolam (0.1 mg/kg, IV) and alfaxalone (n = 9) or ketamine (9) at 2 mg/kg, IV, over 30 seconds. An additional dose of alfaxalone or ketamine (1 mg/kg) was given IV if needed for intubation; anesthesia was maintained with isoflurane in oxygen and IV fluids with ketamine (0.5 to 1 mg/kg/h). Direct systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressures; heart rate; and respiratory rate were recorded before induction, immediately after intubation, and during surgery. Qualitative anesthetic induction and recovery characteristics were assessed. Variables were compared within and between groups by statistical methods.
RESULTS
No preinduction variables differed significantly between groups. Postintubation and 30-minute intraoperative SAP, DAP, and MAP were higher for the ketamine group than for the alfaxalone group; within the alfaxalone group, postintubation SAP, MAP, and respiratory rate prior to mechanical ventilation were lower than respective preinduction values. All alfaxalone-group goats were intubated after 1 dose of the induction agent; 5 of 9 ketamine-group goats required an additional (1-mg/kg) dose. Postoperative recovery was good to excellent for all animals.
CONCLUSIONS AND CLINICAL RELEVANCE
Both drugs were suitable for induction of anesthesia after sedation with midazolam, but most goats required higher doses of ketamine to allow intubation. For situations in which alfaxalone administration is appropriate, the potential for decreased arterial blood pressures and respiratory rate should be considered.
Abstract
OBJECTIVE
To determine if tissue oxygen saturation (StO2) correlates with oxygen delivery (DO2) and/or cardiac output (CO) in a canine hemorrhagic shock model.
ANIMALS
8 healthy purpose-bred dogs.
METHODS
Dogs were anesthetized, and hemorrhagic shock was induced by withdrawing up to 60% of total blood volume, targeting a mean arterial pressure (MAP) of 40 mm Hg. The withdrawn blood was returned to the patient in 2 equal aliquots. Data was collected at 4 time points: 10 minutes after MAP was stabilized under anesthesia (time point [TP]-1), 10 minutes after up to 60% of blood volume was removed to target a MAP of 40 mm Hg (TP2), 10 minutes after the return of 50% of shed blood (TP3), and 10 minutes after the return of the remaining 50% of shed blood (TP4). Total blood volume withdrawn, StO2, CO, heart rate, and MAP were recorded, and DO2 was calculated at each TP.
RESULTS
Mean StO2 significantly decreased between TP1 (77.8% [± 9.54]) and TP2 (44.8% [± 19.5]; P < .001 vs TP1). Mean StO2 increased to 63.1% (± 9.85) at TP3, but remained significantly lower compared to TP1 (P = .002). There was no difference between mean StO2 at TP4 (82.5% [± 12.6]) versus TP1 (P = .466). StO2 has a strong, positive correlation to both CO (r = 0.80; P < .001) and DO2 (r = 0.75; P < .001).
CLINICAL RELEVANCE
A decrease in StO2 may be used in conjunction with physical examination findings and diagnostic parameters to support a diagnosis of shock. The return of shed blood was correlated with increases in StO2, DO2, and CO, suggesting that StO2 may be used as a marker of adequate resuscitation.
Abstract
OBJECTIVE
To determine whether shock index (SI) positively correlates with percentage blood loss and negatively correlates with cardiac output (CO) in a canine hemorrhagic shock model and whether SI and metabolic markers may be used as end point targets for resuscitation.
ANIMALS
8 healthy Beagles.
PROCEDURES
Between September and December 2021, dogs underwent general anesthesia for experimental induction of hypotensive shock, with the total volume of blood removed, CO, heart rate, systolic blood pressure, base excess, blood pH, and concentrations of hemoglobin, lactate, ionized calcium recorded, and SI calculated at 4 time points (TPs): after anesthetic induction when the dog had been stable for 10 minutes (TP1), 10 minutes after the mean arterial pressure stabilized to a target of 40 mm Hg following jugular removal of up to 60% blood volume to induce hemorrhagic shock (TP2), 10 minutes after autotransfusion of 50% of the removed blood (TP3), and 10 minutes after autotransfusion of the remaining 50% of the removed blood (TP4).
RESULTS
Mean SI increased between TP1 (1.08 ± 0.35) and TP2 (1.90 ± 0.73) and did not return to the prehemorrhage values for TP3 or TP4. SI correlated positively with percentage blood loss (r = 0.583) and negatively with CO (r = –0.543).
CLINICAL RELEVANCE
An increase in SI may support diagnosis of hemorrhagic shock; however, SI cannot be used as the sole end point of resuscitation. Significant differences in blood pH, base excess, and lactate concentration suggested they may be useful markers of hemorrhagic shock and need for blood transfusion.
Abstract
OBJECTIVE To determine effects of prosthetic laryngoplasty on return to racing, performance index, and career longevity in racing Quarter Horses with recurrent laryngeal neuropathy (RLN) and to evaluate performance variables for horses with RLN undergoing prosthetic laryngoplasty, compared with a control horse population.
DESIGN Multicenter, retrospective cohort study.
ANIMALS 162 racing Quarter Horses with RLN treated with prosthetic laryngoplasty (case horses) and 324 racing Quarter Horse without RLN (control horses).
PROCEDURES Medical and race records of case and control horses examined at 5 referral centers between January 2000 and December 2015 were reviewed retrospectively. Two control horses were matched with each case horse. Return to racing, earnings, number of racing starts, performance index, and career longevity were evaluated.
RESULTS The odds of returning to racing did not differ significantly between case and control horses but decreased with increasing age. Neither racing starts nor career longevity were affected by prosthetic laryngoplasty or by RLN grade. In fact, horses undergoing laryngoplasty for treatment of RLN and horses with the lowest RLN grade before surgery had higher performance indices after the surgery, compared with indices for control horses.
CONCLUSIONS AND CLINICAL RELEVANCE The faster speeds and shorter distances raced with Quarter Horses could alter how RLN impacts respiratory variables and performance in Quarter Horses, compared with other racehorse breeds. Further study is needed to understand the impacts of RLN and surgical treatments for RLN in racing Quarter Horses.
