Effect of continuous positive airway pressure helmet on respiratory function following surgical procedures in brachycephalic dogs: A randomized controlled trial.

OBJECTIVE: To evaluate the effect of continuous positive airway pressure (CPAP) on respiratory function in the early postoperative period of brachycephalic dogs. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: A total of 32 dogs. METHODS: Dogs were assigned to recover with or without CPAP (control) and assessed at specific time points over 1 h. Treatment was discontinued for dogs with a CPAP tolerance score of 3 or more (from a range of 0-4). The primary outcome was pulse oximetry (SpO2). Secondary outcomes were arterial O2 pressure (PaO2)/FiO2 ratio (PaO2/FiO2), arterial CO2 pressure (PaCO2), and rectal temperature. For dogs that reached a CPAP tolerance score of 3 or more, only the data collected up to the time point before discontinuation were included in the analysis. The treatment effect (ß) was analyzed using random effects models and the results were reported with 95% confidence intervals. RESULTS: Dogs were assigned randomly to each protocol. Baseline characteristics in both groups were comparable. Arterial blood gases were obtained in seven control group dogs and nine CPAP group dogs. Treatment did not affect SpO2 (ß = -0.1, -2.1 to 2.0) but affected the PaO2/FiO2 ratio (ß = 58.1, 2.6 to 113.6), with no effects on PaCO2 (ß = -4.3, -10.5 to 1.9) or temperature (ß = 0.4, -0.8 to 1.6). CONCLUSION: In postoperative brachycephalic dogs, CPAP had no effect on SpO2 but improved the PaO2/FiO2 ratio in brachycephalic dogs postoperatively. CLINICAL SIGNIFICANCE: Continuous positive airway pressure offers a valuable solution to improve gas exchange efficiency, a prevalent concern in postoperative brachycephalic dogs, with the potential to enhance overall outcomes.

Three-dimensional electrical impedance tomography to study regional ventilation/perfusion ratios in anesthetized pigs.

This study aimed to develop a three-dimensional (3-D) method for assessing ventilation/perfusion (V/Q̇) ratios in a pig model of hemodynamic perturbations using electrical impedance tomography (EIT). To evaluate the physiological coherence of changes in EIT-derived V/Q̇ ratios, global EIT-derived V/Q̇ mismatches were compared with global gold standards. The study found regional heterogeneity in the distribution of V/Q̇ ratios in both the ventrodorsal and craniocaudal directions. Although global EIT-derived indices of V/Q̇ mismatch consistently underestimated both low and high V/Q̇ mismatch compared with global gold standards, the direction of the change was similar. We made the software available at no cost for other researchers to use. Future studies should compare regional V/Q̇ ratios determined by our method against other regional, high-resolution methods.NEW & NOTEWORTHY In this study, we introduce a novel 3-D method for assessing ventilation-perfusion (V/Q̇) ratios using electrical impedance tomography (EIT). Heterogeneity in V/Q̇ distribution showcases the significant potential for enhanced understanding of pulmonary conditions. This work signifies a substantial step forward in the application of EIT for monitoring and managing lung diseases.

Low-dose epidural anesthesia decreases the use of intraoperative systemic analgesics in goats undergoing lower urinary tract surgery.

OBJECTIVE: To test whether the use of low-dose epidural anesthesia (EA) in goats undergoing lower urinary tract surgery reduces the requirements of perioperative analgesics, contributes to intraoperative hypotension, and improves postoperative comfort during the first 24 hours after surgery. ANIMALS: Retrospective analysis of 38 goats between January 2019 and July 2022. PROCEDURES: Goats were divided into 2 groups (EA or no EA). Demographic characteristics, surgical procedure, time of anesthesia, and anesthetic agents used were compared between treatment groups. Outcome variables potentially related to the use of EA included dose of inhalational anesthetics, incidence of hypotension (mean arterial pressure < 60 mm Hg), intraoperative and postoperative administration of morphine, and time to first meal after surgery. RESULTS: EA (n = 21) consisted of bupivacaine or ropivacaine 0.1% to 0.2% with an opioid. There were no differences between groups except for age (EA group was younger). Less inhalational anesthetic (P = .03) and less intraoperative morphine (P = .008) were used in the EA group. The incidence of hypotension was 52% for EA and 58% for no EA (P = .691). Administration of postoperative morphine was not different between groups (EA, 67%, and no EA, 53%; P = .686). Time to first meal was 7.5 hours (3 to 18 hours) for EA and 11 hours (2 to 24 hours) for no EA (P = .057). CLINICAL RELEVANCE: Low-dose EA reduced the use of intraoperative anesthetics/analgesics in goats undergoing lower urinary tract surgery without an increased incidence of hypotension. Postoperative morphine administration was not reduced.

High-dose buprenorphine results in a greater occurrence of postoperative hyperthermia than morphine in a randomized clinical trial in cats undergoing ovariohysterectomy.

OBJECTIVE: To compare the thermoregulatory and analgesic effects of high-dose buprenorphine versus morphine in cats undergoing ovariohysterectomy. ANIMALS: 94 client-owned cats. PROCEDURES: Cats were randomized to receive either buprenorphine 0.24 mg/kg or morphine 0.1 mg/kg subcutaneously (SC) during recovery from ovariohysterectomy. Body temperature measurements were obtained before anesthesia, during anesthesia (averaged), at extubation, and 2, 4, and 16 to 20 hours postoperatively. Signs of pain were assessed, and demographic characteristics were compared between groups. The effects of treatment and time on body temperature, point prevalence of hyperthermia (> 39.2 °C), and pain scores were compared with linear or generalized mixed-effect models. RESULTS: Cats receiving morphine (vs. buprenorphine) were older and heavier (both, P ≤ 0.005). Other group characteristics did not differ between treatments. Cats receiving buprenorphine (vs. morphine) had higher postoperative temperatures (P = 0.03). At 2, 4, and 16 to 20 hours after extubation, the point prevalence of hyperthermia was greater (P = 0.001) for cats receiving buprenorphine (55% [26/47], 44% [21/47], and 62% [27/43], respectively) versus morphine (28% [13/46], 13% [6/46], and 47% [21/44], respectively). There were no differences in pain scores between groups or over time. Five cats receiving buprenorphine and 6 receiving morphine required rescue analgesia within the 24-hour period. CLINICAL RELEVANCE: Administration of buprenorphine (0.24 mg/kg SC), compared with morphine (0.1 mg/kg SC), resulted in higher body temperatures without an apparent advantage with regard to analgesia during the first 20 postoperative hours than morphine. Opioid-induced postoperative hyperthermia could confound the diagnosis of fever from different sources.

Effects of intraoperative positive end-expiratory pressure and fraction of inspired oxygen on postoperative oxygenation in dogs undergoing stifle surgery.

OBJECTIVE: To compare the effects of fraction of inspired oxygen (FiO2) with the addition of positive end-expiratory pressure (PEEP) during anesthesia on arterial oxygenation in the first 4 postoperative hours in dogs. We hypothesized that compared with dogs breathing FiO2 ≥ 0.95 and no PEEP (ZEEP), the use of intraoperative PEEP would improve postoperative oxygenation, and that the use of PEEP combined with an FiO2 of 0.4 would further improve it. STUDY DESIGN: Prospective, randomized study. ANIMALS: A total of 30 dogs undergoing unilateral stifle surgery. METHODS: Using a standardized anesthetic protocol, dogs were assigned to either FiO2 ≥ 0.95 and ZEEP, FiO2 ≥ 0.95 and 5 cmH2O PEEP or FiO2 0.4 and 5 cmH2O PEEP. All dogs were mechanically ventilated with a tidal volume of 12 mL kg-1. Dogs breathed room air after recovery from anesthesia. Arterial blood gases were measured during surgical closure and 10, 120 and 240 minutes after extubation. Demographic characteristics were compared with Kruskal-Wallis tests. The effects of treatment and time on the PaO2, PaCO2, PaO2:FiO2 and shunt fraction (F-shunt) were assessed with mixed-effect models. RESULTS: The PaO2 and F-shunt were lower during anesthesia for dogs breathing FiO2 0.4. No differences among groups were measured after extubation for any variable. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with dogs ventilated with FiO2 ≥ 0.95 and ZEEP, application of 5 cmH2O PEEP did not improve intraoperative gas exchange. The combination of 5 cmH2O PEEP and FiO2 0.4 resulted in lower intraoperative F-shunt values. However, no benefits from those maneuvers on postoperative PaO2 and F-shunt were recorded after extubation, suggesting that alterations in pulmonary function imposed by anesthesia were reversed soon after extubation.