Effects of orally administered enalapril on blood pressure and hemodynamic response to vasopressors during isoflurane anesthesia in healthy dogs.

OBJECTIVE: To examine whether preanesthetic administration of enalapril, compared with placebo, results in a greater decline in blood pressure (BP) or decreased responsiveness of BP to isotonic fluids or vasopressors in healthy dogs during isoflurane anesthesia. STUDY DESIGN: Randomized, experimental, placebo-controlled, blinded, crossover study. ANIMALS: Twelve healthy, female, purpose-bred beagles. METHODS: Dogs underwent the following week-long treatment protocols, each preceded by a 1 week washout period: oral placebo twice daily (PLA); oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose withheld on the day of anesthesia (ENA-W), and oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose administered 90 minutes prior to anesthetic induction (ENA). On day 8 of each treatment period, dogs were anesthetized in random order utilizing a standard protocol. Following stabilization at an end-tidal isoflurane concentration (Fe'Iso) of 1.3%, invasively measured systolic (SAP), diastolic (DAP) and mean (MAP) arterial blood pressure were continuously recorded via telemetry. Hypotension (SAP < 85 mmHg) was treated with the following sequential interventions: lactated Ringer's solution (LRS) bolus (10 mL kg(-1) ); repeated LRS bolus; dopamine (7 µg kg(-1)  min(-1) ); and dopamine (10 µg kg(-1)  min(-1) ) first without and then with vasopressin (1 mU kg(-1)  hour(-1) ). RESULTS: Compared with the PLA but not the ENA-W group, the ENA group had significantly lower average SAP, DAP and MAP at an Fe'Iso of 1.3%, spent more minutes in hypotension, and required a greater number of interventions to correct moderate-to-severe mean arterial hypotension. CONCLUSIONS: In healthy dogs, enalapril administered 90 minutes prior to isoflurane anesthesia increases the degree of intra-anesthetic hypotension and the number of interventions required to correct moderate-to-severe hypotension. CLINICAL RELEVANCE: Dogs receiving angiotensin-converting enzyme inhibitors on the day of anesthesia may exhibit clinically significant intra-anesthetic hypotension.

Perianesthetic development of diaphragmatic hernia in a horse with equine pituitary pars intermedia dysfunction (PPID).

A 21-year-old Thoroughbred gelding with a history of equine pituitary pars intermedia dysfunction (PPID) presented with priapism of 2 days' duration. The horse received a caudal morphine epidural and then underwent corpus cavernosum lavage and phallectomy under general anesthesia. The patient's recovery featured multiple unsuccessful attempts to stand and his respiratory distress persisted for several hours until he acutely developed severe colic and was euthanized. Necropsy findings revealed a pituitary adenoma of the pars intermedia, bilateral adrenal cortical hyperplasia, and diaphragmatic herniation. This report suggests that horses with PPID may present a greater risk for diaphragmatic hernia under general anesthesia or during procedures placing stress on the diaphragm, including anesthetic recovery.

Développement périanesthésique d'une hernie diaphragmatique chez un cheval atteint d'une dysfonction de l'hypophyse pituitaire (DHP). Un hongre Thoroughbred âgé de 21 ans avec une anamnèse de dysfonction de l'hypophyse pituitaire (DHP) a été présenté avec un priapisme présent depuis 2 jours. Le cheval a reçu une épidurale caudale de morphine et a ensuite subi un lavement du corps caverneux et une phallectomie sous anesthésie générale. Le rétablissement du patient a comporté de nombreuses tentatives infructueuses de se tenir debout et sa détresse respiratoire a persisté pendant plusieurs heures jusqu'à ce qu'il développe de graves coliques et soit euthanasié. Les constatations à la nécropsie ont révélé un adénome pituitaire de l'hypophyse, de l'hyperplasie corticale bilatérale et une herniation diaphragmatique. Ce rapport suggère que les chevaux atteints de DHP peuvent présenter un plus grand risque d'hernie diaphragmatique sous anesthésie générale ou durant des interventions exerçant un stress sur le diaphragme, y compris le réveil après l'anesthésie.(Traduit par Isabelle Vallières).

Effect of Hypotension and Dobutamine on Gastrointestinal Microcirculations of Healthy, Anesthetized Horses.

Horses undergoing abdominal exploratory surgery are at risk of hypotension and hypoperfusion. Normal mean arterial pressure is used as a surrogate for adequate tissue perfusion. However, measures of systemic circulation may not be reflective of microcirculation. This study measured the mean arterial pressure, cardiac index, lactate, and four microcirculatory indices in six healthy, anesthetized adult horses undergoing elective laparotomies. The microcirculatory parameters were measured at three different sites along the gastrointestinal tract (oral mucosa, colonic serosa, and rectal mucosa) with dark-field microscopy. All macro- and microcirculatory parameters were obtained when the horses were normotensive, hypotensive, and when normotension returned following treatment with dobutamine. Hypotension was induced with increases in inhaled isoflurane. The horses successfully induced into hypotension did not demonstrate consistent, expected changes in systemic perfusion or microvascular perfusion parameters at any of the three measured gastrointestinal sites. Normotension was successfully restored with the use of dobutamine, while the systemic perfusion and microvascular perfusion parameters remained relatively unchanged. These findings suggest that the use of mean arterial pressure to make clinical decisions regarding perfusion may or may not be accurate.

Pharmacodynamics of alfaxalone after single-dose intramuscular administration in red-eared sliders (Trachemys scripta elegans): a comparison of two different doses at two different ambient temperatures.

OBJECTIVE: This study compares the pharmacodynamics of two different doses of alfaxalone administered intramuscularly (IM) to red-eared sliders at two ambient temperatures. STUDY DESIGN: Prospective blinded crossover experimental study. ANIMALS: Nine adult female sliders (Trachemys scripta elegans). METHODS: Following a 2-week acclimation at 22-25 °C, nine sliders were randomly assigned to receive alfaxalone, 10 mg kg(-1) (W10), or 20 mg kg(-1) (W20) IM. Each turtle received each dose, with a minimum 7-day washout period. A blinded observer evaluated heart rate (HR), palpebral and corneal reflexes, muscle relaxation, handling, and response to toe pinch at the following points: pre-injection, and 5, 12, 20, 30, 45, 60, and 120 minutes post-injection. Turtles then acclimated to 18-20 °C for 63 days, and the experiment was repeated in this lower-temperature environment, with treatment groups C10 (alfaxalone 10 mg kg(-1)) and C20 (alfaxalone 20 mg kg(-1)) subjected to the same crossover design. RESULTS: C10 and C20 groups had significantly lower intraanesthetic HR than W10 or W20, respectively. C10 and W20 were significantly more relaxed and easier to handle than W10. No significant differences were observed in palpebral reflex, nor responsiveness to the toe pinch stimulus. None of the turtles lost corneal reflex. W20 and C20 had prolonged recoveries, compared to low-dose groups within the same temperature environment. Recovery was also longer at C20 and C10 compared to W10. CONCLUSIONS: Turtles given 10 mg kg(-1) were more relaxed and easier to handle in cold than warm conditions. Warm turtles were more relaxed and easier to handle when given 20 mg kg(-1) than those given 10 mg kg(-1). Cold conditions correlated with lower HR and longer recovery time for each dose category. CLINICAL RELEVANCE: The turtles had dose-dependent and inconsistent responses to alfaxalone. Lower ambient temperature augmented the behavioral effects of this drug.

A comparison of cardiopulmonary and anesthetic effects of an induction dose of alfaxalone or propofol in dogs.

OBJECTIVE: To compare the physiological parameters, arterial blood gas values, induction quality, and recovery quality after IV injection of alfaxalone or propofol in dogs. STUDY DESIGN: Prospective, randomized, blinded crossover. ANIMALS: Eight random-source adult female mixed-breed dogs weighing 18.7 ± 4.5 kg. METHODS: Dogs were assigned to receive up to 8 mg kg(-1) propofol or 4 mg kg(-1) alfaxalone, administered to effect, at 10% of the calculated dose every 10 seconds. They then received the alternate drug after a 6-day washout. Temperature, pulse rate, respiratory rate, direct blood pressure, and arterial blood gases were measured before induction, immediately post-induction, and at 5-minute intervals until extubation. Quality of induction, recovery, and ataxia were scored by a single blinded investigator. Duration of anesthesia and recovery, and adverse events were recorded. RESULTS: The mean doses required for induction were 2.6 ± 0.4 mg kg(-1) alfaxalone and 5.2 ± 0.8 mg kg(-1) propofol. After alfaxalone, temperature, respiration, and pH were significantly lower, and PaCO2 significantly higher post-induction compared to baseline (p < 0.03). After propofol, pH, PaO2 , and SaO2 were significantly lower, and PaCO2 , HCO3 , and PA-aO2 gradient significantly higher post-induction compared to baseline (p < 0.03). Post-induction and 5-minute physiologic and blood gas values were not significantly different between alfaxalone and propofol. Alfaxalone resulted in significantly longer times to achieve sternal recumbency (p = 0.0003) and standing (p = 0.0004) compared to propofol. Subjective scores for induction, recovery, and ataxia were not significantly different between treatments; however, dogs undergoing alfaxalone anesthesia were more likely to have ≥ 1 adverse event (p = 0.041). There were no serious adverse events in either treatment. CONCLUSIONS AND CLINICAL RELEVANCE: There were no clinically significant differences in cardiopulmonary effects between propofol and alfaxalone. A single bolus of propofol resulted in shorter recovery times and fewer adverse events than a single bolus of alfaxalone.

Comparison of the oral and rectal mucosal and colonic serosal microcirculations of healthy, anesthetized horses.

The objectives of the study were to: i) determine baseline microvascular perfusion indices (MPI) and assess their repeatability in healthy horses under general anesthesia, and ii) compare the MPIs of 3 microvascular beds (oral mucosa, colonic serosa, and rectal mucosa). Healthy adult horses were anesthetized and sidestream dark field microscopy was used to collect video loops of the oral mucosa, rectal mucosa, and colonic serosa under normotensive conditions without cardiovascular support drugs; videos were later analyzed to produce MPIs. Baseline MPI values were determined for each site, which included the total vessel density (TVD), perfused vessel density (PVD), portion perfused vessels (PPV), and microcirculatory flow index (MFI). Differences in MPIs between microvascular beds were not statistically significant. Repeatability of the measurements varied for each MPI. In particular, the site of sampling had a profound effect on the repeatability of the PPV measurements and should be considered in future studies.

Les objectifs de cet étude étaient: i) de déterminer les indices de perfusion microvasculaires (IPM) de base et évaluer leur répétabilité chez les chevaux en bonne santé sous anesthésie générale, et ii) de comparer les IPMs de trois lits microvasculaires (muqueuse orale, séreuse du colon, et muqueuse rectale). Des chevaux adultes en bonne santé ont été anesthésiés et une unité de microscopie au champ sombre a été utilisée pour recueillir des boucles vidéo de la muqueuse buccale, de la muqueuse rectale, et de la séreuse du colon sous des conditions de tension artérielle normale. Les vidéos ont été analysées pour produire les IPMs, incluant la densité totale des vaisseaux, la densité des vaisseaux perfusés, la portion des vaisseaux perfusés, et l'index de flux microcirculaire. Pour chaque IPM, les différences entre les sites anatomiques n'étaient pas significatives statistiquement. La répétabilité des mesures variait pour chaque IPM. En particulier, le type de lit microvasculaire a une influence profonde sur la répétabilité des mesures.(Traduit par les auteurs).

A survey of the use of arterial catheters in anesthetized dogs and cats: 267 cases.

OBJECTIVES: To describe the clinical practice of insertion of arterial catheters in anesthetized dogs and cats, to document complications of arterial catheterization, and to determine risk factors associated with the complications. DESIGN: Prospective clinical study and retrospective evaluation of medical records. SETTING: University teaching hospital. ANIMALS: Dogs (n = 251) and 13 cats anesthetized for clinical procedures with arterial catheters inserted for blood pressure monitoring. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Details of the animal and catheter were collected at the time of anesthesia. On the following day, the catheter site was palpated and observed for abnormalities and the medical records of all animals were reviewed retrospectively for complications. Details of catheter placement were available for 216 catheters: 158 catheters in a dorsal pedal artery, 50 catheters in the median caudal (coccygeal) artery, 6 in the median artery, and 1 each in a cranial tibial and lingual artery. Blood pressure was obtained from 200 catheters, and 12 catheters failed before the end of anesthesia. Postoperative observational data obtained from 112 catheters described a palpable arterial pulse at 73 sites and no pulse at 21 sites. No risk factor for arterial occlusion was identified. No complications resulting from arterial catheterization were noted in the medical records. CONCLUSIONS: Arterial catheterization resulted in loss of a peripheral pulse postoperatively in 21/94 (22.3%) of animals examined, although no evidence of tissue ischemia was noted in the medical records of any of the patients in this study. These results suggest that insertion of a catheter in the dorsal pedal or coccygeal arteries was not associated with a high risk for complications. However, the course of arterial occlusion postoperatively warrants further investigation.

Effect of duration and type of anesthetic on tear production in dogs.

OBJECTIVE: To determine effects of duration and type of anesthetic on tear production in dogs. ANIMALS: 8 female Beagles. PROCEDURES: Each dog was randomly allocated into 1 of 4 groups according to a Latin square design to receive anesthesia as follows: 1 hour with isoflurane, 1 hour with desflurane, 4 hours with isoflurane, and 4 hours with desflurane. Each dog was anesthetized with the selected inhalant 4 times during a 4-week period, with at least 5 days separating anesthetic episodes. Aqueous tear production was measured via the Schirmer I tear test at baseline and 10 minutes, 30 minutes, and 1 hour after induction of anesthesia as well as 2, 3, and 4 hours after induction for the 4-hour groups. Tear production was also measured after the dogs were standing after recovery from anesthesia and 2, 10, and 22 hours after recovery from anesthesia. RESULTS: Aqueous tear production was significantly reduced in dogs during anesthesia and returned to baseline values immediately after recovery and until 10 hours after anesthesia in all treatment groups. Inhalant type and duration had no significant effect. Neither lateral recumbency nor left versus right eyes had a significant effect. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that inhalant anesthetics did not reduce tear production after anesthesia and that longer-duration anesthesia did not cause decreased tear production, compared with shorter-duration anesthesia.

Effects of acepromazine maleate or morphine on tear production before, during, and after sevoflurane anesthesia in dogs.

OBJECTIVE: To investigate the effects of acepromazine maleate and morphine on aqueous tear production before, during, and after sevoflurane anesthesia in dogs. ANIMALS: 6 mixed-breed dogs. PROCEDURES: In a Latin square study design, dogs underwent i.m. administration of morphine (1 mg/kg), acepromazine (0.05 mg/kg), or saline (0.9% NaCl) solution (0.05 mL/kg), followed by induction and maintenance of anesthesia with sevoflurane for 30 minutes. The protocol was repeated until all dogs had received all treatments, with a minimum of 7 days between anesthetic episodes. Aqueous tear production was measured via Schirmer tear test I before treatment (baseline); before anesthetic induction; 5, 10, 20, and 30 minutes after anesthetic induction; immediately once dogs recovered from anesthesia; and 2 and 10 hours after recovery. RESULTS: Aqueous tear production for all treatments was significantly lower 10, 20, and 30 minutes (but not 5 minutes) after anesthetic induction than at baseline, before anesthetic induction, at recovery, and 2 and 10 hours after recovery. Aqueous tear production was significantly higher after saline solution administration than after morphine administration at the preinduction measurement point and 2 hours after recovery. No other differences were detected among the 3 treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Aqueous tear production after anesthesia did not differ significantly from baseline values after any treatment following 30 minutes of sevoflurane anesthesia, suggesting premedication with morphine or acepromazine does not contribute to a decrease in lacrimation in these circumstances.