Lisa Tarragona

Objective: To evaluate whether the velocity–time integral of aortic blood flow (VTI _Ao ) assessed by transthoracic echocardiography is increased after the passive leg‐raising maneuver (PLRM) in anesthetized and mechanically ventilated, fluid‐responder pigs. Design: Prospective laboratory study. Setting: University teaching hospital. Animals: Eight healthy Landrace pigs. Interventions: Pigs were anesthetized, mechanically ventilated, and subjected to the PLRM. Ultrasound‐guided VTI _Ao measurements were compared before and after the PLRM to assess changes. A fluid challenge was then performed, and changes in VTI _Ao were assessed again to classify pigs as fluid responders or nonresponders. Measurements and Main Results: Seven of the eight animals were responders, and one was a nonresponder. After the PLRM, fluid responders exhibited an increase in VTI _Ao compared with baseline ( p = 0.017). An optimal cutoff of 11.2% for changes in ultrasound‐guided VTI _Ao was calculated for predicting fluid responsiveness after the PLRM, with an area under the receiver operating characteristic curve of 1.00 (95% confidence interval [CI]: not estimated), sensitivity of 100% (95% CI: 59–100), specificity of 100% (95% CI: 2.5–100), positive predictive value of 100% (95% CI: 59–100), and negative predictive value of 100% (95% CI: 2.5–100). Conclusions: Despite limitations, this study demonstrates the potential of using ultrasound‐guided VTI _Ao measurements associated with the PLRM to predict fluid responsiveness in anesthetized pigs. An ultrasound‐guided VTI _Ao cutoff of ≥11.2% could serve as a reference for identifying fluid‐responsive pigs under anesthesia and mechanical ventilation, and offer a noninvasive alternative to fluid challenges.

Objective: To assess the splenic flow resistance index (RI) and its response to a fluid bolus in dogs showing circulatory abnormalities upon hospital admission.Design: Prospective clinical study.Setting: Veterinary referral hospital.Animals: Nine dogs with circulatory shock and nine dogs without circulatory abnormalities.Interventions: Dogs with circulatory abnormalities received an IV bolus of 30 mL/kg of balanced isotonic crystalloid fluid.Measurements and Main Results: The splenic flow RI and the baseline aortic velocity–time integral of both groups of dogs were evaluated upon hospital admission. Measurements were repeated after the fluid bolus in dogs with circulatory shock. The Mann–Whitney U‐test or the Wilcoxon rank sign test was used as appropriate. The median RI in dogs with circulatory shock was higher than that in dogs without hemodynamic disorders (median [interquartile range]: 0.64 [0.62–0.77] vs. 0.54 [0.51–0.54], P < 0.001). The best cutoff value to discriminate between the two groups was 0.61, with an area under the receiver operating characteristic curve of 1.00 (95% confidence interval [CI]: 1.00–1.00), a sensitivity of 100% (95% CI: 66.4–100), a specificity of 100% (95% CI: 66.4–100), a positive predictive value of 100% (95% CI: 66.4–100), and a negative predictive value of 100% (95% CI: 66.4–100). After fluid expansion, a significant decrease in the median splenic flow RI was observed (0.57 [0.54–0.71], P = 0.007 vs. basal).Conclusions: The splenic flow RI may be a dependable tool for identifying circulatory shock in dogs and assessing their response to fluid therapy. Additional studies are required to evaluate the use of this index for the monitoring of organ perfusion, changes in cardiac output, and fluid responsiveness in critically ill dogs.

Objective: To evaluate if variation in the end‐tidal CO₂ partial pressure (∆Petco₂) after a fluid challenge could predict fluid responsiveness with a sensitivity of 75% and a specificity of 70% in healthy anesthetized and mechanically ventilated dogs.Design: Diagnostic accuracy study.Setting: University hospital.Animals: Twenty‐seven dogs admitted for neutering.Interventions: To obtain a balanced sample between fluid responder and nonresponder dogs, a 10‐mL/kg lactated Ringer's solution was administered over 15 minutes to half of the population before the baseline measurements. All animals then received a fluid challenge of 10 mL/kg lactated Ringer's solution in 5 minutes.Measurements and Main Results: The velocity–time integral of aortic blood flow (VTI_Ao) was evaluated with Doppler echocardiography before and after a fluid challenge to classify the included dogs as fluid responders or nonresponders. Fluid responsiveness was defined as an increase of ≥15% of the VTI_Ao after the fluid challenge. Petco₂ was evaluated at 1, 5, and 10 (T1, T5, T10) minutes after fluid expansion. Area under the receiver operating characteristic curve (AUROC) analysis was used to assess the ability of ∆Petco₂ to predict fluid responsiveness at different time points. A total of 13 dogs were fluid responders, and 14 were nonresponders. The best predictive capacity for ∆Petco₂ was observed at T10. The AUROC with its 95% confidence interval (CI) for ∆Petco₂ at T10 was 0.75 (0.56–0.93), with a sensitivity of 84.62% (95% CI, 54.60–98.10), a specificity of 64.29% (95% CI, 35.10–87.20), a positive predictive value of 68.80% (95% CI, 41.30–89.00), and a negative predictive value of 81.80% (95% CI, 48.20–97.70). The optimal cutoff was 1 mm Hg.Conclusions: The current study showed that, although minimal, ∆Petco₂ predicted fluid responsiveness in the dogs studied.

Objective: To evaluate the changes in flow velocities of the middle cerebral artery before and after a carotid compression maneuver using transcranial color‐coded duplex sonography (TCCD) in healthy anesthetized dogs under mechanical ventilation.Design: Prospective study.Setting: University teaching hospital.Animals: Eleven healthy adult dogs.Interventions: A 5‐second carotid occlusion maneuver was performed to evaluate cerebral autoregulation (CA).Measurements and Main Results: After 10 minutes of stable anesthesia, the middle cerebral artery was evaluated by TCCD. Dogs were positioned in sternal recumbency with the head raised to the level of the phlebostatic axis. The systolic peak velocity (Vp) was measured using pulsed Doppler mode. CA was evaluated through the transient hyperemia test (THT), which assesses changes in the Vp after a 5‐second transient compression of the ipsilateral common carotid artery and is expressed as the ratio between the Vp flow before and after carotid compression. The Vp before and after carotid occlusion was compared using the Wilcoxon signed‐rank test. The median Vp of the middle cerebral artery after the carotid compression maneuver was significantly higher than the median Vp before compression (median [interquartile range, IQR]: 47.7 cm/s [34.3] vs 64.1 cm/s [24.4]; P = 0.003). The median THT obtained was 1.20 (IQR: 0.37).Conclusions: The current study demonstrated a significant increase in the Vp of the middle cerebral artery after a 5‐second temporary occlusion of the ipsilateral carotid artery in healthy anesthetized dogs under mechanical ventilation. These findings suggest that the noninvasive TCCD methodology could be valuable for assessing CA in dogs. Additional studies using this technique in neurocritical animals are required to confirm its usefulness.

This study assessed the analgesic and motor effects of the GIN-TONIC block, a combination of the greater ischiatic notch plane block and the caudal lateral quadratus lumborum block, in 24 dogs undergoing pelvic limb surgery. Dogs were randomly divided into two equal groups: G_A received acepromazine [(20 µg kg⁻¹ intravenously (IV)] as premedication, and G_D received dexmedetomidine (2 µg kg⁻¹ IV). General anesthesia was maintained with isoflurane, and both groups received a GIN-TONIC block using 2% lidocaine. Nociception during surgery and postoperative pain [assessed using the Glasgow Composite Measure Pain Score (GCMPS-SF)] were assessed. Fentanyl (2 µg kg⁻¹ IV) was administered if nociception was noted and morphine (0.5 mg kg⁻¹ IV) was administered during recovery if the pain scores exceeded the predefined threshold. Motor function was assessed during the recovery period using descriptors previously reported. All dogs received analgesics at the 4 h mark before being discharged. Three and two dogs in G_D and G_A required fentanyl once. Postoperative pain scores remained ≤4/20 for all dogs except one. Dogs achieved non-ataxic ambulation within 38.9 ± 10.3 and 35.1 ± 11.1 min after extubation in G_D and G_A, respectively. This study highlighted the potential of the GIN-TONIC block as a feasible regional anesthesia method for delivering perioperative analgesia in dogs undergoing pelvic limb orthopedic surgery.

To evaluate the echocardiographic variable tricuspid annular plane systolic excursion normalised to body weight (TAPSEnorm) as a predictor of fluid responsiveness in hospitalised dogs with haemodynamic and tissue perfusion alterations and to investigate the association of left ventricular internal diameter in diastole normalised to body weight (LVIDdN) and aortic velocity time integral (VTI_Ao) with TAPSEnorm. A single-centre, prospective study was carried out in a cohort of spontaneously breathing dogs, hospitalised for any reason, with severe haemodynamic and tissue perfusion alterations. The echocardiographic variables TAPSEnorm, LVIDdN, and VTI_AO were measured. A bolus of 30 mL/kg of lactated Ringer’s solution was administered and then VTI_Ao was subsequently remeasured. Patients were classified as fluid responsive if VTI_Ao increased by ≥15% after fluid expansion, or non-responsive if VTI_Ao increased by AO. TAPSEnorm was lower in fluid responsive dog (mean 0.57 (95% CI=0.50–0.64) cm/kg) compared to non-responders (mean 0.76 (95% CI=0.62–0.90) cm/kg). The AUROC for TAPSEnorm was 0.827 (95% CI=0.65–1.00). The optimal cut-off point was 0.76 with sensitivity of 80 (95% CI=28.4–99.5)% and specificity of 86.7 (95% CI=69.3–99.2)%, positive predictive value of 50 (95% CI=15.7–84.3)% and negative predictive value of 96.3 (95% CI=81–99.9)%. A monotonic linear relationship was observed between TAPSEnorm and LVIDdN (pAo (p=0.001). TAPSEnorm could be useful in determining those dogs that are likely to respond to a fluid bolus from those that are likely to be non-responsive. Additionally, a positive linear association between the LVIDdN and the TAPSEnorm suggests that TAPSEnorm decreases at lower preload values. The present study results suggest that TAPSEnorm could be a valuable tool for evaluating blood volume status and fluid responsiveness in hospitalised dogs.

The current COVID-19 pandemic has led the world to an unprecedented global shortage of ventilators, and its sharing has been proposed as an alternative to meet the surge. This study outlines the performance of a preformed novel interface called ’ACRA’, designed to split ventilator outflow into two breathing systems. The ’ACRA’ interface was built using medical use approved components. It consists of four unidirectional valves, two adjustable flow-restrictor valves placed on the inspiratory limbs of each unit, and one adjustable PEEP valve placed on the expiratory limb of the unit that would require a greater PEEP. The interface was interposed between a ventilator and two lung units (phase I), two breathing simulators (phase II) and two live pigs with heterogeneous lung conditions (phase III). The interface and ventilator adjustments tested the ability to regulate individual pressures and the resulting tidal volumes. Data were analyzed using Friedman and Wilcoxon tests test (p < 0.05). Ventilator outflow splitting, independent pressure adjustments and individual tidal volume monitoring were feasible in all phases. In all experimental measurements, dual ventilation allowed for individual and tight adjustments of the pressure, and thus volume delivered to each paired lung unit without affecting the other unit’s ventilation—all the modifications performed on the ventilator equally affected both paired lung units. Although only suggested during a dire crisis, this experiment supports dual ventilation as an alternative worth to be considered.