Microcirculation assessment of dexmedetomidine constant rate infusion during anesthesia of dogs with sepsis from pyometra: a randomized clinical study.

OBJECTIVE: To compare dexmedetomidine and fentanyl constant rate infusions in anesthetic protocols for septic dogs with pyometra, using microcirculatory, hemodynamic and metabolic variables. STUDY DESIGN: Randomized clinical study. ANIMALS: A total of 33 dogs with pyometra with two or more systemic inflammatory response syndrome variables undergoing ovariohysterectomy. METHODS: Dogs were randomized into two groups: group DG, dexmedetomidine (3 µg kg-1 hour-1; 17 dogs) and group FG, fentanyl (5 µg kg-1 hour-1; 16 dogs) infused during isoflurane anesthesia and mechanical ventilation. Microcirculation flow index (MFI), total vessel density and De Backer score were assessed using orthogonal polarization spectral imaging at the sublingual site. Heart rate, invasive blood pressure, temperature, arterial blood gas analysis and lactate concentration were obtained at various time points. Variables were recorded at baseline (BL), immediately before (T0), 30 (T30) and 60 (T60) minutes after infusion, and 60 minutes after surgery. Data were analyzed using the Shapiro-Wilk test. To compare variables between groups, the unpaired Student t test was used. Comparison between evaluation time points was performed with two-way anova for repeated measures. Where statistical significance was detected, the Bonferroni post hoc test was used. RESULTS: MFI was significantly higher in group FG at T30. Mean arterial pressure at T30 was higher in group DG (89 ± 15 mmHg) than in group FG (72 ± 13 mmHg). Lactate concentrations were not significantly different between groups at each time point. Both groups had similar clinical outcomes (mortality, extubation time and occurrence of hypotension and bradyarrhythmias). CONCLUSIONS AND CLINICAL RELEVANCE: Dexmedetomidine (3 µg kg-1 hour-1) without a loading dose can be included in the maintenance of anesthesia in dogs with pyometra and sepsis without compromising microcirculation and hemodynamic values when compared with fentanyl (5 µg kg-1 hour-1).

Cyclooxygenases 1 and 2 inhibition and analgesic efficacy of dipyrone at different doses or meloxicam in cats after ovariohysterectomy.

OBJECTIVE: To evaluate the cyclooxygenases (COX) inhibition, adverse effects and analgesic efficacy of dipyrone or meloxicam in cats undergoing elective ovariohysterectomy. STUDY DESIGN: Prospective, blinded, randomized, clinical study. ANIMALS: A total of 30 healthy young cats. METHODS: The cats were randomly assigned to three postoperative groups: D25 (dipyrone 25 mg kg-1 every 24 hours), D12.5 (dipyrone 12.5 mg kg-1 every 12 hours) and M (meloxicam 0.1 mg kg-1 every 24 hours). In the first 24 hours, the drugs were administered intravenously (IV), and then orally for 6 (dipyrone) or 3 days (meloxicam). Prostanoids thromboxane B2 and prostaglandin E2 concentrations served as indicators of COX activity and, with physiological variables and pain and sedation scores, were measured for 24 hours after first analgesic administration. Rescue analgesia (tramadol, 2 mg kg-1 IV) was provided if Glasgow feline composite measure pain scale (CMPS-Feline) ≥5. Laboratory tests included symmetric dimethylarginine and adverse effects were evaluated regularly up to 7 and 10 days after surgery, respectively. Parametric and nonparametric data were analyzed with two-way anova and Kruskal-Wallis tests, respectively (p < 0.05). RESULTS: In the first half hour after analgesic administration, COX-1 activity was close to zero and remained significantly lower than before drug administration for 24 hours in all groups. The inhibition of COX-2 activity was significant for 30 minutes in all groups and up to 4 hours in group M. No alterations in laboratory tests or significant adverse effects were observed. Pain scores and need for rescue analgesia did not differ statistically among groups. CONCLUSIONS: Dipyrone at both doses and meloxicam provided a nonselective inhibition of COX-1 and -2 activities and effective analgesia without causing significant adverse effects or laboratory tests alterations. CLINICAL RELEVANCE: Dipyrone at both doses provides equally effective analgesia without causing adverse effects in cats undergoing ovariohysterectomy.

Nephrosplenic Space Ablation in Horses After Homologous Pericardium Implant Using a Laparoscopic Stapler.

This study aimed to describe and evaluate a laparoscopic technique to promote nephrosplenic space ablation in horses using a homologous pericardium implant, preserved in 98% glycerin and fixed using laparoscopic polydioxanone staples. In this experimental study, six Arabian horses without previous related abdominal diseases were used. The surgical procedures were performed in the standing position under sedation with alpha-2 agonists and opioids, associated with local infiltration of the local anesthetic in the portal sites. The horses were restrained in a stock, and the left flanks were clipped and aseptically prepared. Three portals were created on the left flank, and the homologous pericardium implant, measuring 10 × 5 cm, was introduced into the abdominal cavity covering the nephrosplenic space, positioned between the dorsal border of the spleen and perirenal fascia, fixed with polydioxanone staples using a laparoscopic stapler. Physical examination and blood and peritoneal fluid sample collection were performed on days 0, 1, 3, 7, 14, 30, and 60 of the postoperative period, and an exploratory laparoscopy was performed on day 60 to assess the effectiveness of the technique and eventual complications. There were no difficulties or significant complications during the surgical procedure, and the total average time to perform was 49.83 minutes (±10.19). In the postoperative period, there was a significant increase (P < .05) in the plasma fibrinogen concentration on days 7 and 14 compared with the preoperative moment. The total nucleated cell count in the peritoneal fluid increased (P < .05) on days 1, 3, 7, 14, and 30. After 60 days of the surgical procedure, the physical examination and laboratory data were within the normal range. Exploratory laparoscopy performed on day 60 revealed complete occlusion of the nephrosplenic space, and it was not possible to differentiate the pericardium implant from the scar tissue, not even in the histological evaluation performed on the collected samples. In two horses, omentum adhesion was observed in the region where the implant was fixed, and in two others, a synechia was observed between the implant area and mesocolon without association with clinical complications. The animals were followed up for 36 months at surgery, and no colic signs were observed along this period. It was concluded that the technique of ablation of the nephrosplenic space, using homologous pericardium preserved in 98% glycerin, fixed by polydioxanone staples by laparoscopy, was simple to perform, effective, and free of clinical complications during the period of evaluation, and its use may be indicated as a surgical option in clinical cases of horses with recurrent nephrosplenic entrapment.

Evaluation of hematologic, biochemical, and blood gas variables in stored canine packed red blood cells, and the impact of storage time on blood recipients.

BACKGROUND: Canine packed red blood cells (pRBCs) can be stored under refrigeration for several days; however, cellular metabolism remains active inside the units, thus producing substances that affect their quality. OBJECTIVES: We aimed to evaluate hematologic, biochemical, and blood gas variable alterations that occur in canine pRBCs during storage, and their effects on recipient clinicopathologic parameters. METHODS: The study was conducted in two phases. In phase I, 15 pRBC units containing CPDA-1 were stored for 28 days; samples were collected weekly from the units of days 0 to 28 to measure the packed cell volume (PCV), pH, partial pressure carbon dioxide (PCO2 ), partial pressure oxygen (PO2 ), concentrations of lactate and potassium, and the percent hemolysis. In phase II, another 22 canine pRBC units stored for different time periods (maximum of 21 days) were transfused, and the recipients were evaluated before and after transfusion for changes in clinical parameters (heart rate, respiratory rate, systolic arterial pressure, and rectal temperature) and hematologic variables (PCV, lactate and potassium concentrations, pH, PCO2 , the ratio of arterial oxygen partial pressure to fractional inspired oxygen [PO2 /FiO2 ] ratio, oxygen saturation [SaO2 ], base excess, and bicarbonate [HCO3 ]). RESULTS: In the pRBC units, the PCV increased from 70% to 78.33%, the lactate concentration increased 627%, the potassium concentration increased 183%, the percent hemolysis reached 0.69%, and the pH decreased 9% after 28 days. However, the dogs who received transfusions were not negatively affected. There was a significant increase in PCVs, and a significant decrease in heart rates. CONCLUSION: Canine pRBCs undergo hematologic, blood gas, and biochemical alterations during storage; however, the transfusion of pRBCs stored for up to 21 days increased PCVs without causing harm to the dogs.

Comparison of pulse pressure variation versus echocardiography-derived stroke volume variation for prediction of fluid responsiveness in mechanically ventilated anesthetized dogs.

OBJECTIVE: To evaluate the ability and accuracy of aortic flow velocity-time integral variation (ΔVTI) and peak aortic velocity variation (ΔVpeak) compared with pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated dogs. STUDY DESIGN: Prospective clinical study. ANIMALS: A group of 50 mechanically ventilated dogs with spontaneous hypotension during orthopedic or oncologic surgery. METHODS: Investigations were performed in the surgery room. When mean arterial pressure (MAP) decreased to <65 mmHg, measurements were performed before and after a fluid challenge (lactated Ringer's solution 5 mL kg-1 over 15 minutes). Responders were defined as a change in stroke volume (SV; transesophageal Doppler) ≥15%. Data were analyzed using paired/unpaired t test or Mann-Whitney/Wilcoxon test when appropriate and receiver operating characteristics (ROC) curves; a p value <0.05 was considered statistically significant. RESULTS: After the fluid challenge, 35 (70%) of 50 dogs were responders with significant increases in SV and decreases in PPV; 15 dogs were nonresponders. ΔVTI and ΔVpeak correlated with a 15% increase in SV. The optimum cut-off value for PPV was 15.6% (sensitivity, 88%; specificity, 100%), for ΔVTI was 10.65% (sensitivity, 65%; specificity, 100%) and for ΔVpeak was 10.15% (sensitivity, 80%; specificity, 100%). The area under the ROC curve for PPV was (0.93 ± 0.08) and for ΔVpeak was (0.89 ± 0.09), before fluid challenge. The gray zone area spread from 6.15% to 15.6% for PPV (18 dogs), 2.45% to 10.65% for ΔVTI (22 dogs) and 0.6% to 10.15% for ΔVpeak (25 dogs). CONCLUSIONS: When using mechanical ventilation, ΔVTI and ΔVpeak predicted fluid responsiveness with the same ability as PPV, based on the area under the ROC curve analysis. However, PPV showed great accuracy demonstrated by a narrower gray zone that included fewer individuals. CLINICAL RELEVANCE: ΔVTI and ΔVpeak can be used as indices of fluid responsiveness in anesthetized dogs.

Effects of 12 and 17 cmH2O positive end-expiratory pressure applied after alveolar recruitment maneuver on pulmonary gas exchange and compliance in isoflurane-anesthetized horses.

OBJECTIVE: To compare static compliance (Cst) and alveolar-arterial oxygen tension difference [P(a-a)O2] between positive end-expiratory pressures (PEEP) of 7, 12 and 17 cmH2O applied after an alveolar recruitment maneuver (RM) in isoflurane-anesthetized horses. STUDY DESIGN: Prospective, randomized, clinical study. ANIMALS: A group of 30 healthy adult horses undergoing arthroscopic surgery. METHODS: Animals in dorsal recumbency and mechanically ventilated with a tidal volume of 14 mL kg-1 and 7 cmH2O PEEP (control; n = 6) were subjected to an RM by increasing PEEP from 7 to 22 cmH2O in 5 cmH2O increments at 5 minute intervals, and then decreased similarly to PEEP of 17 (RM17; n = 8), 12 (RM12; n = 8) or 7 cmH2O (RM7; n = 8). Cst and P(a-a)O2 were assessed prior to (baseline) and after the RM at 5, 10, 15, 20, 40, 60 and 80 minutes after achieving each target PEEP, and during recovery from anesthesia. RESULTS: Post-RM improvements on P(a-a)O2 were maintained (baseline versus 80 minutes) in RM12 [216 ± 77 mmHg (28.8 ± 10.3 kPa) versus 194 ± 39 mmHg (25.9 ± 5.2 kPa)] and RM17 [180 ± 86 mmHg (24.0 ± 11.6 kPa) versus 136 ± 75 mmHg [18.2 ± 10.0 kPa]). The improvements on Cst were maintained only in RM12 (0.80 ± 0.13 versus 0.98 ± 0.13 mL cmH2O-1 kg-1). No such improvements were observed in RM7 and control. No significant differences were observed between groups during recovery from anesthesia. CONCLUSIONS: and clinical relevance The 12 and 17 cmH2O PEEP can be used to maintain the improvements on P(a-a)O2 obtained after an RM. Only 12 cmH2O PEEP maintained the post-RM increase on Cst. Such variables were not influenced by the 7 cmH2O PEEP.

Postoperative pain and short-term complications after two elective sterilization techniques: ovariohysterectomy or ovariectomy in cats.

BACKGROUND: Surgical sterilization of cats is one of the most commonly performed procedures in veterinary practice and it can be accomplished by two different techniques: ovariohysterectomy (OVH) or ovariectomy (OVE). Although there is an apparent preference for OVH in United States and Canada, OVE seems to be the standard of care in many European countries due to its advantages, such as a smaller surgical incision and potentially less complications associated with surgical manipulation of the uterus. The aim of this randomized, blind, prospective study was to compare postoperative pain and short-term complications in cats undergoing ovariohysterectomy or ovariectomy. METHODS: Twenty female cats were randomly assigned into two groups (OVH, n = 10 and OVE, n = 10). Pain was assessed prior to surgery (baseline) and 1, 2, 4, 8 12 and 24 h after the procedure using pain and sedation scales, physiologic parameters and blood glucose levels. Short-term complications were evaluated in the early postoperative period and reassessed at day 7 and day 10. RESULTS: Changes in cardiovascular parameters were not clinically relevant, however cats in OVH group had higher heart rates at T1 h compared with baseline (p = 0.0184). Blood glucose levels in OVH group were also higher at T1 h compared with baseline (p = 0.0135) and with OVE group (p = 0.0218). Surgical time was higher in OVH group (p = 0.0115). Even though no significant differences in pain scores were observed between groups or time points, cats in OVH group had greater need for rescue analgesia compared with OVE (2/10 and 0/10, respectively). Complications were not observed in any cat during surgery, at days 7 and 10 postoperatively or at discharge. CONCLUSIONS: Both surgical techniques promoted similar intensity of postoperative pain in cats and there were no short-term complications throughout the study's evaluation period. Therefore, both techniques may be indicated for surgical sterilization of cats, according to the surgeon's preference and expertise. Cats that underwent ovariectomy did not require rescue analgesia and surgical time was shorter in that group.

Pulse pressure variation as a guide for volume expansion in dogs undergoing orthopedic surgery.

OBJECTIVE: To investigate whether pulse pressure variation (PPV) can predict fluid responsiveness in healthy dogs during clinical surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Thirty-three isoflurane-anesthetized dogs with arterial hypotension during orthopedic surgery. METHODS: Fluid challenge with lactated Ringer's solution (15 mL kg-1 in 15 minutes) was administered in mechanically ventilated dogs (tidal volume 10 mL kg-1) with hypotension [mean arterial pressure (MAP) < 65 mmHg]. The volume expansion was considered effective if cardiac output (CO; transesophageal Doppler) increased by ≥ 15%. Cardiopulmonary data were analyzed using two-way ANOVA, receiver operating characteristics (ROC) curves and Spearman coefficient; p < 0.05 was considered significant. RESULTS: Effective volume expansion, mean ± standard deviation 42 ± 4% increase in CO (p < 0.0001) was observed in 76% of the dogs, resulting in a decrease in PPV (p < 0.0001) and increase in MAP (p < 0.0001), central venous pressure (CVP; p = 0.02) and ejection fraction (p < 0.0001) compared with before the fluid challenge. None of these changes occurred when volume expansion resulted in a nonsignificant CO increase of 4 ± 5%. No significant differences were observed in blood gas analysis between responsive and nonresponsive dogs. The increase in CO was correlated with the decrease in PPV (r = -0.65; p < 0.0001) but absolute values of CO and PPV were not correlated. The PPV performance (ROC curve area: 0.89 ± 0.06, p = 0.0011) was better than that of CVP (ROC curve area: 0.54 ± 0.12) and MAP (ROC curve area: 0.59 ± 0.13) to predict fluid responsiveness. The best cut-off for PPV to distinguish responders and nonresponders was 15% (50% sensitivity and 96% specificity). CONCLUSIONS AND CLINICAL RELEVANCE: In mechanically ventilated, healthy, isoflurane-anesthetized dogs, PPV predicted fluid responsiveness to volume expansion, and MAP and CVP did not show such applicability.

Effect of postoperative xylazine administration on cardiopulmonary function and recovery quality after isoflurane anesthesia in horses.

OBJECTIVE: To evaluate equine cardiopulmonary function and recovery quality after administration of 0.25 or 0.50 mg/kg xylazine intravenously (IV) during recovery. STUDY DESIGN: Randomized, blinded, prospective, clinical study. ANIMALS: Horses (n = 20). METHODS: During recovery after 3 hours of isoflurane anesthesia for arthroscopic surgery, horses were administered either 0.25 mg/kg (G25, n = 10) or 0.50 mg/kg (G50, n = 10) xylazine intravenously. Vital signs and arterial blood samples were obtained during recovery before sedation (baseline), 5, 10, 20, 30, and 45 minutes after xylazine and 30 minutes after standing. The quality of recovery scores ranged from 10 to 72 (10 = best, 72 = worst). RESULTS: G25 horses recovered faster (mean ± SD, 33 ± 5 min) than G50 horses (50 ± 7 min, P < .0001). Mean maximal decrease in arterial oxygen tension was 55 ± 11 mmHg in G25 (at 10 minutes; P < .05) and 54 ± 7 mmHg in G50 (at 20 minutes; P < .01). G25 group had a total recovery score (23 [range 18-29]) and number of attempts to stand (4 ± 2) greater than the G50 group (18 [10-23] and 1 ± 1, respectively; P < .001). CONCLUSIONS: Both doses of xylazine promoted a moderate and transient hypoxemia during recovery; however, the 0.5 mg/kg dose produced a longer and improved quality of recovery from anesthesia.

Effects of positive end-expiratory pressure titration on gas exchange, respiratory mechanics and hemodynamics in anesthetized horses.

OBJECTIVE: To assess if positive end-expiratory pressure (PEEP) titration improves gas exchange and respiratory mechanics, without hemodynamic impairment in horses during anesthesia. DESIGN: Prospective, randomized study. ANIMALS: Thirteen isoflurane-anesthetized healthy horses. METHODS: After 60 minutes of anesthesia with spontaneous breathing, mechanical ventilation was initiated with an inspiratory-expiratory ratio of 1:2, PEEP of 5 cmH2O, tidal volume of 10-20 mL kg(-1) and respiratory rate adjusted to maintain normocapnia. Constant PEEP of 5 cmH2O was continued (control group; n = 6) or titrated (PEEP group; n = 7) by increasing and decreasing PEEP from 5 to 20 cmH2O at 15-minute intervals. The horses were instrumented with an arterial catheter to measure blood pressure and allow collection of blood for pH and blood gas analysis and a Swan-Ganz catheter for measurement of cardiac output (CO) using thermodilution. Cardiopulmonary assessment was recorded before PEEP titration and after 15 minutes at each PEEP value. RESULTS: In the PEEP group, static compliance (range) (Cst 278-463 mL cmH2O(-1)) was significantly higher and the shunt fraction (Q·s/Q·t 7-20%) and the alveolar-arterial oxygen difference [P(A-a)O2 95-325 mmHg] were significantly lower than in the control group [Cst of 246-290 mL cmH2O(-1), Q·s/Q·t of 16-19%, P(A-a)O2 of 253-310 mmHg; p < 0.05]. CO (mean ± SEM) was lower in the PEEP group (23 ± 2 L minute(-1)) at 20 cmH2O PEEP than in the control group (26 ± 4 L minute(-1), p < 0.05), with no significant changes in heart rate, blood pressure or central venous pressure. CONCLUSIONS: PEEP titration significantly improved gas exchange and lung compliance, with a small decrease in CO at the highest PEEP level. CLINICAL RELEVANCE: Gas exchange and respiratory mechanics impairment during inhalation anesthesia can be treated using PEEP titration from 5 to 20 cmH2O, without clinically important hemodynamic effects in healthy horses.

Effect of ephedrine and phenylephrine on cardiopulmonary parameters in horses undergoing elective surgery.

OBJECTIVE: To assess the cardiopulmonary effects of ephedrine and phenylephrine for management of isoflurane-induced hypotension in horses. STUDY DESIGN: Prospective randomized clinical study. ANIMALS: Fourteen isoflurane-anesthetized horses undergoing digital palmar neurectomy. METHODS: Ephedrine (EPH group; 0.02 mg kg(-1) minute(-1); n = 7) or phenylephrine (PHE group; 0.002 mg kg(-1) minute(-1); n = 7) was administered to all horses when mean arterial pressure (MAP) was <60 mmHg. The infusions were ended when the target MAP was achieved, corresponding to a 50% increase over the pre-infusion MAP (baseline). The horses were instrumented with an arterial catheter to measure blood pressure and allow the collection of blood for pH and blood-gas analysis and a Swan-Ganz catheter for measurement of cardiac output using thermodilution. Cardiopulmonary parameters were recorded at baseline and at 5, 30, 60 and 90 minutes after achieving the target MAP. RESULTS: In both groups, the MAP and systemic vascular resistance (SVR) increased significantly at 5, 30, 60 and 90 minutes post infusion compared to baseline (p < 0.05). The EPH group had a significant increase in cardiac index (CI) and systemic oxygen delivery index at 5, 30, 60 and 90 minutes post infusion compared to baseline (p < 0.05) and compared to the PHE group (p < 0.05). The PHE group had significantly higher SVR and no decrease in oxygen extraction compared with the EPH group at 30, 60 and 90 minutes post infusion (p < 0.05). No significant differences in ventilatory parameters were observed between groups after the infusion. CONCLUSIONS: Ephedrine increased the MAP by increasing CI and SVR. Phenylephrine increased MAP by increasing SVR but cardiac index decreased. Ephedrine resulted in better tissue oxygenation than phenylephrine. CLINICAL RELEVANCE: Ephedrine would be preferable to phenylephrine to treat isoflurane-induced hypotension in horses since it increases blood flow and pressure.

Effects of positive end-expiratory pressure titration and recruitment maneuver on lung inflammation and hyperinflation in experimental acid aspiration-induced lung injury.

BACKGROUND: In acute lung injury positive end-expiratory pressure (PEEP) and recruitment maneuver are proposed to optimize arterial oxygenation. The aim of the study was to evaluate the impact of such a strategy on lung histological inflammation and hyperinflation in pigs with acid aspiration-induced lung injury. METHODS: Forty-seven pigs were randomly allocated in seven groups: (1) controls spontaneously breathing; (2) without lung injury, PEEP 5 cm H2O; (3) without lung injury, PEEP titration; (4) without lung injury, PEEP titration + recruitment maneuver; (5) with lung injury, PEEP 5 cm H2O; (6) with lung injury, PEEP titration; and (7) with lung injury, PEEP titration + recruitment maneuver. Acute lung injury was induced by intratracheal instillation of hydrochloric acid. PEEP titration was performed by incremental and decremental PEEP from 5 to 20 cm H2O for optimizing arterial oxygenation. Three recruitment maneuvers (pressure of 40 cm H2O maintained for 20 s) were applied to the assigned groups at each PEEP level. Proportion of lung inflammation, hemorrhage, edema, and alveolar wall disruption were recorded on each histological field. Mean alveolar area was measured in the aerated lung regions. RESULTS: Acid aspiration increased mean alveolar area and produced alveolar wall disruption, lung edema, alveolar hemorrhage, and lung inflammation. PEEP titration significantly improved arterial oxygenation but simultaneously increased lung inflammation in juxta-diaphragmatic lung regions. Recruitment maneuver during PEEP titration did not induce additional increase in lung inflammation and alveolar hyperinflation. CONCLUSION: In a porcine model of acid aspiration-induced lung injury, PEEP titration aimed at optimizing arterial oxygenation, substantially increased lung inflammation. Recruitment maneuvers further improved arterial oxygenation without additional effects on inflammation and hyperinflation.