Acute lung injury and acute respiratory distress syndromes in veterinary medicine: consensus definitions: The Dorothy Russell Havemeyer Working Group on ALI and ARDS in Veterinary Medicine

Background: As veterinary medicine has become more sophisticated, with greater numbers of veterinary patients receiving intensive care, more patients with an acute respiratory distress (ARDS)‐like syndrome have been recognized. Methods: A consensus definition meeting was held for the purpose of developing veterinary‐specific definitions for acute lung injury (ALI) and ARDS. Results/conclusions: Three clinically based definitions for acute lung injury and acute respiratory distress‐like syndromes occurring in veterinary patients were described. Neonatal equine respiratory distress syndrome (NERDS) was defined separately due to the specific requirement for primary developmental surfactant dysfunction and lack of an inflammatory component. Five diagnostic criteria categories were established for Veterinary ALI/ARDS (Vet ALI/ARDS) with 4 required and a fifth highly recommended criteria. A strong consensus was reached that onset of respiratory distress must have been acute and that known risk factors must be present. Additional criteria included evidence of pulmonary capillary leak with no evidence of increased pulmonary capillary pressure, evidence of inefficient gas exchange and, finally, evidence of inflammation. Some features of ALI/ARDS in the neonatal horse were recognized as unique, therefore, equine neonatal ALI/ARDS (EqNALI/EqNARDS) was similarly defined but with a graded gas exchange inefficiency table to allow for normal developmental changes in gas exchange. Use of these definitions in planning prospective studies of these problems in veterinary patients should allow for more direct comparisons of studies and clinical trials, with a larger goal of improving outcome in veterinary patients.     

A case of spontaneous venous embolism with carbon dioxide during laparoscopic surgery in a pig

BACKGROUND: Carbon dioxide (CO2) embolism is a possible complication of capnoperitoneum during laparoscopic surgery. Experimentally induced venous CO2 embolism has been studied in pigs. In this paper we report a case of spontaneous CO2 embolism. OBSERVATIONS: A 4-month-old Large White pig weighing 20 kg underwent experimental laparoscopic surgery under general anaesthesia. Monitoring consisted of pulse oximetry, capnography, airway pressure, electrocardiography, invasive arterial and central venous blood pressures, and arterial blood-gas analysis. Shortly after the start of laparoscopy and onset of CO2 insufflation, sudden decreases in end-tidal CO2 (Pe'CO2), haemoglobin saturation of oxygen (SpO2), systolic arterial blood pressure and heart rate were observed. Airway pressure increased and pulmonary compliance decreased simultaneously. Insufflation was immediately discontinued and epinephrine (2 mg IV), atropine (0.5 mg IV) and a 50 mL bolus of a polygeline solution were administered without effect. At this time arterial blood-gas analysis revealed a pH of 7.29 and a PaCO2 of 6.8 kPa (51.2 mmHg); PaO2 was 26.6 kPa (199.5 mmHg). After 4 minutes asystole occurred. CONCLUSIONS: The sudden decrease of Pe'CO2 and lung compliance combined with the sudden decrease in systolic blood pressure, heart rate and a poor response to resuscitation suggest a case of fatal gaseous venous embolism.     

Pulmonary gas exchange in anaesthetised horses mechanically ventilated with oxygen or a helium/oxygen mixture

Reason for performing study: It is unknown whether administration of gas‐mixtures high in inspired fraction of oxygen (FiO₂) under general anaesthesia may increase formation of pulmonary atelectasis and impair gas exchange. Objective: To evaluate the effects of different FiO₂ on pulmonary gas exchange in isoflurane‐anaesthetised horses breathing a helium/oxygen (He/O₂) mixture. Methods: Thirty healthy mature horses were sedated with i.v. acepromazine (0.02 mg/kg bwt), detomidine (0.002 mg/kg bwt) and xylazine (0.2‐0.4 mg/kg bwt). General anaesthesia was induced with i.v. 5% guaifenesin to effect, diazepam (0.1 mg/kg bwt) and ketamine (2 mg/kg bwt), and maintained with isoflurane. Fifteen horses (Group HX) were ventilated mechanically with gas mixtures of successively increasing FiO₂ (0.25‐0.30, 0.50‐0.55, >0.90), obtained by blending O₂with Heliox (70% He/30% O₂). The other 15 horses (Group O) were ventilated immediately with 100% O₂(FiO₂>0.90). After 20 min of ventilation at the different FiO₂levels in Group HX and after 60 min in Group O, PaO₂ and PaCO₂ were measured and the alveolar to arterial PO₂gradient (P(_A‐a)O₂) was calculated. Data analysis included robust categorical regression with clustering on horse (P<0.05). Results: Inhalation of a He/O₂ mixture with FiO₂ as low as 0.25‐0.30 ensured adequate arterial oxygenation and was associated with a smaller P_(A‐a)O₂ gradient than inhalation of pure O₂ (P<0.05). In Group HX, PaO₂ increased with each rise in FiO2 and so did P(A‐a)O₂ (P<0.05). The PaO₂ was significantly lower and the P_(A‐a)O₂ higher in Group O compared to Group HX at a FiO₂ >0.90 (P<0.05). Conclusions and potential relevance: Administration of a He/O₂gas mixture low in FiO₂ can better preserve lung function than ventilation with pure oxygen. A step‐wise increase of FiO₂ using a He/O₂ gas mixture might offer advantages with respect to pulmonary gas exchange over an immediate exposure to 100% O₂.     

A comparison of subarachnoid buprenorphine or xylazine as an adjunct to lidocaine for analgesia in goats

ObjectiveTo test the hypothesis that subarachnoid administration of buprenorphine and lidocaine provides more intense and longer lasting perioperative analgesia with less side effects than xylazine and lidocaine in goats.Study designRandomized, blinded, controlled study.Study animals Ten healthy female goats randomly assigned to two groups of five animals each.MethodsAfter sedation with acepromazine (0.1 mg kg^?1) intravenously (IV), lidocaine 2% (0.1 mL kg^?1) combined with either xylazine (0.05 mg kg^?1; Group X) or buprenorphine (0.005 mg kg^?1; Group B) were injected intrathecally at the lumbo-sacral junction prior to stifle surgery. Electrocardiogram, heart rate, direct systolic, mean, and diastolic arterial blood pressures, rectal temperature and arterial blood gases were recorded as were post-operative sedation and pain scores using a visual analogue and numeric rating scale, respectively. Data were analyzed with one-way anova for repeated measures, one-way anova, Friedman's and Kruskal–Wallis tests as necessary (p< 0.05).ResultsSurgery was successfully performed under both analgesia protocols. Total pain and sedation scores were significantly lower in the B as compared with X group from 3–24 hours and 30–120 minutes, respectively after subarachnoid drug administration (SDA). Heart rate and arterial blood pressures decreased post SDA and were consistently lower in X versus B (p< 0.05). In B arterial blood gas parameters did not change post SDA, but in group X PaCO₂ increased slightly within 15 minutes of SDA and remained elevated for at least 3 hours (p< 0.05).ConclusionIn these goats intrathecal administration of buprenorphine and lidocaine produced more profound and longer lasting analgesia with less sedation and hemodynamic and respiratory impairment than xylazine with lidocaine.Clinical relevanceIn these goats undergoing hind limb surgery, subarachnoid buprenorphine/lidocaine offered more intense and longer lasting analgesia than a xylazine/lidocaine combination, with less sedation and impairment of cardiopulmonary function.     

Comparison of intra-operative analgesia provided by intravenous regional anesthesia or brachial plexus block for pancarpal arthrodesis in dogs

The aim of this study was to compare intravenous regional anesthesia (IVRA) and brachial plexus block (BPB) for intra-operative analgesia in dogs undergoing pancarpal arthrodesis (PA). Twenty dogs scheduled for PA were intramuscularly sedated with acepromazine (0.03mg/kg), general anesthesia was intravenously (IV) induced with thiopental (10mg/kg) and, after intubation, maintained with isoflurane in oxygen. In 10 dogs (GIVRA) IVRA was performed on the injured limb administering 0.6ml/kg of 0.5% lidocaine. In 10 dogs (GBPB) the BPB was performed at the axillary level with the help of a nerve stimulator and 0.3ml/kg of a 1:1 solution of 2% lidocaine and 1% ropivacaine was injected. During surgery fentanyl (0.002mg/kg IV) was administered if there was a 15% increase of HR and/or MAP compared to the values before surgical stimulation. All the standard cardiovascular and respiratory parameters were continuously monitored during surgery. The duration of surgery and the time of extubation were recorded. Data were compared with a 1-way ANOVA test (P<0.05). No patients required fentanyl administration during surgery. All the recorded parameters were similar in the two groups. The two techniques were similar in providing intra-operative analgesia in dogs undergoing orthopaedic surgery.     

Intraoperative contrast echocardiography to verify the surgical occlusion of a single extrahepatic portosystemic shunt in a dog

This report details a bubble echocardiographic study carried out during the surgical treatment of a congenital single extrahepatic portosystemic shunt (PSS) in a Labrador Retriever. After celiotomy, agitated saline was injected through a jejunal vein and microbubbles appeared rapidly in the right cardiac chambers. The test confirmed the presence of a PSS, helping the surgeon to identify the vessel concerned and to rule out a second shunt. Successively, portography confirmed what the exploratory celiotomy had revealed before with the aid of the bubble study: a single shunt was located between the portal vein and the right renal vein. It was completely ligated, as all the criteria for this solution were met. Intraoperative contrast echocardiography (ICE) was easy to perform, helpful and undemanding. It is proposed here as an intraoperative ancillary test to diagnose all PSS and to confirm successful treatment when complete shunt closure is possible.     

Evaluation of Echocardiographic Parameters During Increasing Infusion Rates of Dobutamine in Isoflurane-Anesthetized Horses

The purpose of this study was to evaluate changes in echocardiographic parameters during increasing infusion rates of dobutamine in isoflurane-anesthetized horses and to compare our results with those of previous studies. Six Standardbred female healthy horses were included in this study. All animals were anesthetized and infused with dobutamine at different rates. mean arterial pressure (MAP), heart rate (HR), and some echocardiographic measurements were recorded. Statistical analysis was applied. Under basal conditions (time 0 [T0]), HR ranged between 32 and 42 beats per minute (bpm), and MAP was between 39 and 63 mm Hg. MAP increased significantly from T0 compared with values at T2, T2, and T3 in a dose-dependent manner, while HR increased significantly only at T3 if compared to the other measuring times. Left ventricular internal diameter during diastole (LVDs) decreased significantly in a dose-dependent manner, with increasing of the infusion rate of dobutamine. Interventricular septal dimension during diastole (IVSs) increased significantly, and end-systole left ventricular volumes (LVVols) decreased significantly at T2 and T3 compared to T1. Ejection fraction (%) increased significantly between T0 and T1, T2, and T3. Cardiac output increased significantly only at the higher dosage (T3 vs. others) of dobutamine, but cardiac power output was enhanced significantly at T2 versus that at T0 and T1 and at T3 versus all the previous measurements. Arrhythmias were diagnosed in 5 of 6 (83.3%). In this study, the increase of MAP was found to be dose-dependent, according with literature. The HR and MAP values registered at T0 were comparable to previous results obtained both in anesthetized and conscious horses, while at T1, T2, and T3, HR and MAP values were similar only too those reported in anesthetized horses. IVSs increased and LVDs decreased significantly with the increment of dobutamine infusion rate. These findings suggest that dobutamine, even at low infusion rates, induces an enhancement in cardiac systolic function. The dose-dependent increase of IVSs and decrease of LVDs measurements are in line with those reported for dobutamine administered in conscious horses but with lower values. The LVVols dose-dependent reduction obtained in this study is in line with that in other reports, but both LVold and LVVols values after dobutamine infusion at different dosages are lower if compared to previous studies. The low LVol values and the wide standard deviation have influenced consequently the derived indices values (stroke volume [SV], EF, cardiac output [CO]). In the present study, SV did not significantly increase during dobutamine infusion. These results disagree with those reported by others. The increment of CO might be due mainly to the enhanced HR rather than to the weak changes of SV. Cardiac power output increased significantly from the 5 mcg/kg/min dosage in a dose-dependent manner, as reported by others.     

An alveolar recruitment maneuver followed by positive end-expiratory pressure improves lung function in healthy dogs undergoing laparoscopy

Objective

To evaluate the effects of an alveolar recruitment maneuver (ARM) followed by 5 cmH₂O positive end-expiratory pressure (PEEP) in dogs undergoing laparoscopy.

WHICH AIRWAY PRESSURE SHOULD BE APPLIED DURING BREATH‐HOLD IN DOGS UNDERGOING THORACIC COMPUTED TOMOGRAPHY?

This randomized controlled trial study aimed to identify the optimal positive pressure (PP) level that can clear atelectasis while avoiding pulmonary hyperinflation during the breath‐hold technique in dogs undergoing thoracic computed tomography (CT). Sixty dogs affected by mammary tumors undergoing thoracic CT for the screening of pulmonary metastases were randomly assigned to six groups with different levels of PP during the breath‐hold technique: 0 (control), 5 (PP5), 8 (PP8), 10 (PP10), 12 (PP12), and 15 (PP15) cmH₂O. The percentage of atelectatic lung region was lower in the PP10 (3.7 ± 1.1%; P = 0.002), PP12 (3.4 ± 1.3%; P = 0.0001), and PP15 (2.8 ± 0.9%; P = 0.006) groups than in the control group (5.0 ± 2.3%), and the percentage of poorly aerated lung region was lower in the PP8 (15.1 ± 2.6%; P = 0.0009), PP10 (13.0 ± 2.0 %; P = 0.002), PP12 (13.0 ± 2.2 %; P = 0.0002), and PP15 (11.1 ± 1.9%; P = 0.0002) groups than in the control group (19.8 ± 5.0). The percentage of normally aerated lung region, however, was higher in the PP10 (79.7 ± 4.1%; P = 0.005), PP12 (79.8 ± 5.1%; P = 0.0002), and PP15 (80.2 ± 4.9%; P = 0.002) groups than in the control group (73.4 ± 6.6%). A PP of 10–12 cmH₂O during the breath‐hold technique should be considered to improve lung aeration during a breath‐hold technique in dogs undergoing thoracic CT.