Colonic Luminal Pressure in Horses With Strangulating and Nonstrangulating Obstruction of the Large Colon

Colonic luminal pressure (median, range) measured during ventral midline celiotomy in 69 horses with strangulating obstruction (SO) of the large colon (SO; ≥ 270° large colon volvulus; 27 cm H₂O: 2 to 80 cm H₂O) was greater ( P =.0023) than that measured in 37 horses with nonstrangulating obstruction (NSO) of the large colon (NSO; ≤ 180° volvulus or a nonstrangulating displacement; 18 cm H₂O; 6 to 46 cm H₂O). Sixty-five percent (45 of 69) of horses with SO and all horses with NSO survived. Survival analysis was restricted to 59 horses with large-colon SO that survived to hospital discharge or met the criteria specified for classification as nonsurvivors. Colonic luminal pressure in nonsurvivors (48.5 cm H₂O; 34 to 80 cm H₂O) was higher ( P =.0001) than that measured in survivors (18 cm H₂O; 2 to 50 cm H₂O) of SO. From response operating characteristic curves, a luminal pressure of 38 cm H₂O optimized the distribution of horses with SO into survivor and nonsurvivor groups. Sensitivity, specificity, and positive and negative predictive values for a colonic luminal pressure greater than 38 cm H₂O in predicting nonsurvival were 0.89, 0.91, 0.72 and 0.97, respectively. Measurement of colonic luminal pressure may be useful for predicting survival in horses with colonic volvulus.     

Clinical Determination of Preoperative and Postoperative Intra-abdominal Pressures in Dogs

Intra-abdominal pressure (IAP) was indirectly measured, using a transurethral catheterization technique, in 20 client-owned dogs before and after elective ovariohysterectomy. Mean preoperative IAP was 4.50 ± 0.44 cm H₂O. Elective abdominal surgery caused significant elevations in mean postoperative IAP (mean 7.50 ± 0.45 cm H₂O, range 0 to 15 cm H₂O) that persisted for at least 24 hours. However, the increase in IAP caused no clinically evident complications; thus, after elective abdominal surgery an elevation in IAP up to 15 cm H₂O is to be expected. Intra-abdominal pressure was also measured in 20 consecutive clinical cases with gross abdominal distension, before or after laparotomy, or both. Included in this group were dogs with gastric dilation and volvulus, closed pyometra, hemoperitoneum, acute ascites, and diaphragmatic hernias. All dogs with gross abdominal distension had an elevated IAP (> 16 cm H₂O) either before or after surgery. Severe elevations of IAP were associated with anuria in two dogs, necessitating surgical decompression; one with hemoperitoneum (47 cm H₂O) and one after repair of a chronic diaphragmatic hernia (30 cm H₂O).     

Modification of a Nonrebreathing Circuit Adapter to Prevent Barotrauma in Anesthetized Patients

Barotrauma, pneumothorax, and pneumomediastinum occurred in two anesthetized cats in which the waste gas outlet of a nonrebreathing circuit was occluded. To prevent any similar cases of barotrauma, we have modified our nonrebreathing circuit adapters by inserting a 15 cm H₂O PEEP valve into the gas pathway of the nonrebreathing circuit adapter. This PEEP valve prevents the circuit and airway pressures from exceeding 15 cm H₂O if the pop-off valve of the nonrebreathing circuit adapter is inadvertently left closed.     

Effect of 5 cm of Water Positive End-Expiratory Pressure on Arterial Oxygen Tension in Dogs During and After Thoracotomy

Thoracotomy in dogs often is associated with lower than expected arterial oxygen tensions (PaO₂). Pulmonary collapse from opening the thoracic cavity is likely to be responsible for decreased PaO₂ during thoracotomy. To examine whether positive end-expiratory pressure (PEEP) is beneficial to dogs undergoing thoracotomy, PaO₂ and hemoglobin saturation (SaO₂) were measured in dogs randomly assigned to receive 5 cm of H₂O PEEP (n = 7) or no PEEP (n = 9). During surgery in both groups of dogs, PaO₂ progressively decreased ( P < .001), but the decrease in PaO₂ was significantly less in the PEEP group ( P = .027). In both groups, PaO₂ did not decrease enough to have a substantial effect on SaO₂. Furthermore, application of PEEP during thoracotomy did not prevent moderate hypoxemia after surgery and discontinuation of PEEP. Application of 5 cm of H₂O PEEP seems to attenuate the decrease in PaO₂ observed in dogs undergoing thoracotomy, but routine application of PEEP does not seem justified. ©     

Cardiopulmonary and Analgesic Effects of Epidural Lidocaine, Alfentanil, and Xylazine in Pigs Anesthetized With Isoflurane

To determine cardiopulmonary and analgesic effects of lidocaine, alfentanil, and xylazine in pigs anesthetized with isoflurane, 18 healthy Landrace-Large White pigs were studied (six for each drug). General anesthesia was induced with isoflurane in O₂ and maintained with 1% to 1.2% end-tidal ISO, ensuring presence of a pain response before epidural drug administration. Heart rate (HR), arterial blood pressures (AP), cardiac output (CO), pulmonary arterial pressure, pulmonary capillary wedge pressure (PCWP), central venous pressure, respiratory rate (RR), tidal volume (TV), minute volume (MV), arterial blood gas data, core temperature (CT), and analgesic effects (by pricking the lumbar area and the abdominal wall) were determined at various times (2, 5, 15, 30, 45, 60, and 90 minutes) after epidural administration of lidocaine (5 μg/kg), alfentanil (5 μg/kg), or xylazine (0.2 mg/kg), all diluted in NaCl 0.9% to 0.5 mL/kg. Statistical analysis included two-way analysis of variance for repeated measures and the least significant difference test for determining differences among means. A probability level of P <.05 was used. The following results were statistically significant decreases in systolic AP, HR, TV, RR, MV, CT, pH, PaO₂, and TCO₂ and increases in PCWP, PaCO₂, and HCO₃ after LID. After ALF, only CT and HCO₃ decreased. Core temperature and TV decreased after XYL. Lidocaine provided 45 to 60 minutes of analgesia. Alfentanil had no analgesic effects, and xylazine provided 90 minutes of analgesia. The authors conclude that xylazine, when injected epidurally, provides suitable analgesia in isoflurane-anesthetized pigs.     

The lowering effect of high copper intake on selenium retention in weanling rats depends on the selenium concentration of the diet

The question addressed was whether the influence of dietary copper concentration on selenium metabolism depends on the amount of selenium in the diet. Weanling, male rats were fed purified diets containing either 1 (low), 4 (normal) or 42 (high) mg Cu/kg diet and either 0.03 (low), 0.05 (normal) or 1.0 (high) mg Se/kg diet in a 3² factorial design. Extra copper was added to the diets in the form of CuSO₄ · 5H₂O and selenium as Na₂SeO₃ · 5H₂O. In rats fed either the low or normal amounts of selenium, higher intakes of copper decreased the apparent intestinal selenium absorption and increased urinary selenium excretion. The effects of copper on selenium absorption, excretion and retention were not seen in rats fed the high-selenium diets. An increase in dietary copper concentrations elevated selenium concentrations in the liver and kidneys, but slightly lowered those in the spleen of rats that were fed the diets with the normal level of selenium. In rats that were fed the diets with either low or high selenium concentration, copper intake had no effect on organ selenium concentrations. Glutathione peroxidase activity in erythrocytes was raised by feeding the diets which contained either normal or high copper content instead of those that were low in copper. It is concluded that the amount of selenium in the diet determines whether or not an increase in dietary copper concentration affects selenium metabolism.     

Effect of the 5-lipoxygenase inhibitor, fenleuton, on antigen-induced neutrophil accumulation and lung function changes in horses with chronic obstructive pulmonary disease

The leukotrienes (LT) LTD₄ and LTB₄ have been shown to cause bronchoconstriction and neutrophil accumulation, respectively, in horse lungs. Such changes are characteristic of the equine allergic respiratory disease, chronic obstructive pulmonary disease (COPD). To further investigate the role of these putative mediators in the pathogenesis of equine COPD the effect of a 5-lipoxygenase inhibitor, fenleuton, on antigen-induced changes in horses with this condition has been examined. Six horses with COPD underwent a series of four antigen challenges, one month apart, with placebo pre-treatment on three occasions and fenleuton (4 days oral dosing 5 mg/kg) pre-treatment on one occasion. Three horses received fenleuton prior to the second challenge and three horses received the drug prior to the fourth antigen challenge. Changes in radiolabelled neutrophil distribution, lung function and peripheral leucocyte counts were monitored on each occasion for 7 h following the start of antigen challenge. Antigen challenge caused an increase in radioactive counts over the lungs and a decrease in peripheral leucocyte count. Neither response was affected by fenleuton pre-treatment. Mean maximal changes in pleural pressure (ΔP_plmax) and respiratory rate were also unaffected by fenleuton pre-treatment. However, in the two horses which responded to antigen-challenge with a particularly marked increase in ΔP_plmax (>15 cm H₂O), prior administration of fenleuton reduced the response by 64 and 63%. These results suggest that 5-lipoxygenase inhibitors warrant further investigation as bronchodilators in equine COPD.     

High-Frequency Jet Ventilation in Anesthetized, Paralyzed Dogs and Cats Via Transtracheal and and Endotracheal Tube Routes

The ability of the SAV 6 high-frequency jet ventilator to effectively ventilate three anesthetized, paralyzed cats (3.2–4.2 kg), two small dogs (7.2 and 10.0 kg), six medium-sized dogs (20.5–25.0 kg), and three large dogs (36.0–43.0 kg) via a 14-gauge (dogs) or a 16-gauge (cats) catheter placed percutaneously into the trachea via the cricothyroid membrane or into a preplaced endotracheal tube was evaluated. The lowest driving pressure within the range of 0.25 to 2.0 kg/cm² (1 kg/cm²= 14.2 psi) and the highest cycle rate within the range of 60 to 240 per minute that would generate a PaCO₂ of 30 ± 3 mm Hg were determined.
All animals could be ventilated to a PaC0₂ of 30 ± 3 mm Hg by the endotracheal tube and transtracheal route, except the largest dogs, which couid be ventilated to an average PaC0₂ of 36 mm Hg by the transtracheal route. The transtracheal route consistently required higher driving pressures and lower cycle rates than did the endotracheal tube route. Cats could be ventilated with a driving pressure of 0.25 kg/cm²; small dogs could be ventilated with 0.5 to 1.0 kg/cm₂; medium-sized dogs with 1.0 to 1.5 kg/cm²; and large dogs with 1.5 to 2.0 kg/cm².
The SAV 6 high-frequency jet ventilator can effectively ventilate cats and dogs (7.2–43.0 kg) via a transtracheal catheter and an endotracheal tube.     

Pulmonary function, ventilator management, and outcome of dogs with thoracic trauma and pulmonary contusions: 10 cases (1994-1998)

OBJECTIVE: To document pulmonary function, ventilator management, and outcome of dogs with thoracic trauma that required mechanical ventilation because of severe pulmonary contusions. DESIGN: Retrospective study. ANIMALS: 10 dogs that required mechanical ventilation because of severe pulmonary contusions caused by blunt thoracic trauma. PROCEDURE: Signalment, historical data, arterial blood gas values, oxygen tension-based indices, ventilator settings, peak inspiratory pressure, positive end-expiratory pressure, tidal volume, and minute ventilation values were retrieved from medical records. RESULTS: All 10 dogs required positive-pressure ventilation because of dyspnea following trauma and had severely abnormal pulmonary function. Survival rate to discharge was 30%. Dogs were categorized into 2 groups; group A included 5 dogs in which pulmonary function improved during ventilation, whereas group B included 5 dogs that were euthanatized because of progressive lung dysfunction (n = 4) or cardiac arrest (1). Mean +/- SD body weight of group-A dogs (30.9 +/- 15.9 kg [68 +/- 35 lb]) was significantly greater than that of group-B dogs (7.6 +/- 1.8 kg [16.7 +/- 4 lb]). Dogs with improved lung function had peak inspiratory pressure that decreased progressively, whereas lung compliance deteriorated in dogs in group B. CONCLUSIONS AND CLINICAL RELEVANCE: Dyspneic dogs with severe pulmonary contusions may require and benefit from positive-pressure ventilation Prognosis is better for dogs that weigh > 25 kg (55 lb).     

Cardiopulmonary Effects of Using Carbon Dioxide for Laparoscopic Surgery in Dogs

Cardiopulmonary effects of laparoscopic surgery were investigated in five crossbred dogs (21 ± 1.9 kg). Premedicated dogs were anesthetized with thiopental and maintained with halothane at 1.5 times minimum alveolar concentration in oxygen. Controlled ventilation maintained partial pressure of end-tidal co₂ at 40 ± 2 mm Hg. Vecuronium was used for skeletal muscle relaxation. After instrumentation and stabilization, baseline measurements were made of cardiac output (thermodilution technique), mean systemic, mean pulmonary arterial and pulmonary wedge pressures, heart rate, saphenous vein and central venous pressures, and minute ventilation. Baseline arterial and mixed venous blood samples were drawn for analysis of pH, Pao₂, Paco₂, Pvo₂, Pvco₂, and bicarbonate concentrations. Systemic and pulmonary vascular resistances, oxygen delivery and consumption, shunt fraction, and dead space ventilation were calculated using standard formulas. Abdominal insufflation using co₂ to a pressure of 15 mm Hg for 180 minutes resulted in significant ( P <.05) increases in heart rate (15 to 180 minutes), minute ventilation (75 to 135 minutes), and saphenous vein pressure (15 to 180 minutes), and decreases in pH (60 to 180 minutes) and Pao₂ (60 to 180 minutes). For 30 minutes after desufflation, there was a significant decrease in Pao₂, and increases in cardiac output, o₂ delivery, and heart rate, compared with baseline. There was a significant increase in shunt fraction and decrease in pH at 15 minutes after desufflation only. The changes were within physiologically acceptable limits in these healthy, ventilated dogs.     

Effect of a tongue-tie on upper airway mechanics in horses during exercise

OBJECTIVE: To determine the effect of a tongue-tie on upper airway mechanics in exercising horses. ANIMALS: 5 Standardbreds. PROCEDURE: Peak inspiratory and expiratory tracheal and pharyngeal pressures and airflow were measured while horses exercised on a treadmill with and without a tongue-tie. Respiratory rate was also measured. Horses ran at speeds that corresponded to 50 (HR50), 75, 90 (HR90), and 100% of maximal heart rate. The tongue-tie was applied by pulling the tongue forward out of the mouth as far as possible and tying it at the level of the base of the frenulum to the mandible with an elastic gauze bandage. Peak inspiratory and expiratory tracheal, pharyngeal, and translaryngeal resistance, minute ventilation, and tidal volume were calculated. Data were analyzed by use of 2-way repeated-measures ANOVA. For post hoc comparison of significant data, the Student-Newman-Keuls test was used. RESULTS: We were unable to detect significant differences between groups for peak inspiratory or expiratory tracheal or pharyngeal resistance, peak pressure, peak expiratory flow, tidal volume, respiratory rate, or minute ventilation. Horses that ran with a tongue-tie had significantly higher peak inspiratory flows, compared with horses that ran without a tongue-tie. In the post hoc comparison, this effect was significant at 4 m/s, HR50, and HR90. CONCLUSION AND CLINICAL RELEVANCE: Application of a tongue-tie did not alter upper respiratory mechanics in exercising horses and may be beneficial in exercising horses with certain types of obstructive dysfunction of the upper airways. However, application of a tongue-tie does not improve upper airway mechanics in clinically normal horses.     

Tracheal gas isufflation-aided mechanical ventilation during carbon dioxide-induced pneumoperitoneum in rabbits

Despite numerous benefits of laparoscopic procedures, the serious hypercapnia and respiratory acidosis in hypercapnic patients with decreased pulmonary compliance during carbon dioxide-induced pneumoperitoneum (CDP) may be developed. Tracheal gas insufflation (TGI) has been shown to be a useful adjunct to controlled mechanical hypoventilation. This study was undertaken to identify whether TGI superimposed on controlled mechanical ventilation (CMV) improve ventilatory efficiency during CDP in rabbits. Sixteen paralyzed and anesthetized rabbits were used. The animals were assigned to two groups-CMV group: CMV alone; TGI group: CMV superimposed by TGI with flow rate of 2L/min. The animals were insufflated to intra-abdominal pressure of 8 mmHg with CO2 gas. Then, tidal volume (V(T)) was changed to maintain the set peak inspiratory pressure (PIP) value, while other ventilatory settings were kept constant. The set PIP value corresponding to 30, 60, and 90 min after the start of peritoneal insufflation of CO2 were 15, 22, and 25 cm H2O, respectively. During CDP with TGI, PaCO2 decreased significantly (p<0.01) from CMV without TGI of 82.1 +/- 14.1 to 47.5 +/- 5.5, 58.1 +/- 9.9 to 40.0 +/- 4.6, 47.1 +/- 9.4 to 32.7 +/- 5.1 mmHg at PIP of 15, 22, and 25 cm H2O, respectively. The inspired V(T) decreased significantly (p<0.05) from CMV without TGI of 18.4 +/- 3.9 to 12.8 +/- 2.8 ml at PIP of 15 cm H2O. TGI superimposed on CMV is more effective than CMV alone in enhancing ventilatory efficiency during CDP in rabbits.     

Comparison of the Bain system and Uniflow universal anaesthetic breathing systems in spontaneously breathing young pigs

OBJECTIVE: To compare minimum fresh gas flow (V(min)) requirements and respiratory resistance in the Uniflow and Bain anaesthetic breathing systems used in the Mapleson D mode. Animals Seven pigs, aged 8-12 weeks, anaesthetized for ophthalmic surgery. MATERIALS AND METHODS: Anaesthesia was maintained with halothane delivered in oxygen using a (Mapleson D) Bain breathing system. The V(min) that prevented re-breathing was found, and peak inspiratory (PIP) and peak expiratory (PEP) pressures measured. The fresh gas flow (V(f)) was then increased to V(min) + 50%, then V(min) + 100%, and respiratory pressures re-measured. A heat and moisture exchanger (HME) was inserted at the endotracheal tube and the procedure repeated. The breathing system was then exchanged for a Uniflow and the protocol repeated. After final disconnection from the breathing system, the animals' peak inspiratory and expiratory flows, tidal, and minute volumes (Vm) were measured over five respiratory cycles. RESULTS: The V(min) (L minute(-1); mL kg(-1) minute(-1)) required to prevent rebreathing in the Uniflow system [8.1(mean) +/-1.7 (SD); 332 +/- 94] was significantly greater than the Bain system (6.5 +/- 1.1; 256 +/- 64). At V(min), PEP with the Uniflow (3.5 +/- 0.1 cm H(2)O) was significantly higher than the Bain system (2 +/- 0.7 cm H(2)O), but PIP values did not differ (Uniflow -0.6 +/- 2.1 cm H(2)O; Bain system -0.2 +/- 0.6 cm H(2)O). With both systems, PEP increased significantly (p < 0.001) with each increase in V(f): Uniflow system 4.2 +/- 0.4 (V(min) + 50%) and 5.5 +/- 0.5 cm H(2)O (V(min) + 100%); Bain system 2.8 +/- 0.7 (V(min) + 50%) and 3.5 +/- 0.7 cm H(2)O (V(min) + 100%). Insertion of the HME did not alter pressures. The mean tidal volume was 6.4 +/- 1.6 mL kg(-1); mean Vm was 184.9 +/- 69.8 mL kg(-1) and mean respiratory rate was 28 +/- 5 breaths minute(-1). In one pig breathing with the Uniflow system PEP rose sharply; respiratory and heart rates increased, and ventricular dysrhythmias occurred. When the system was changed and V(f) reduced, physiological variables became normal. CONCLUSION: The study discredited the hypothesis that the two breathing systems behave similarly. Values for V(min) and PEP were higher with the Uniflow system. Increasing V(f) increased PEP with both systems. Insertion of an HME did not affect respiratory pressures. CLINICAL RELEVANCE: The Uniflow used in Mapleson D mode is not suitable for anaesthesia in young spontaneously breathing pigs.     

Effects of an alveolar recruitment maneuver on cardiovascular and respiratory parameters during total intravenous anesthesia in ponies

OBJECTIVE: To evaluate pulmonary and cardiovascular effects of a recruitment maneuver (RM) combined with positive end-expiratory pressure (PEEP) during total intravenous anesthesia in ponies. ANIMALS: 6 healthy adult Shetland ponies. PROCEDURE: After premedication with detomidine (10 microg/kg, IV), anesthesia was induced with climazolam (0.06 mg/kg, IV) and ketamine (2.2 mg/kg, IV) and maintained with a constant rate infusion of detomidine (0.024 mg/kg/h), climazolam (0.036 mg/kg/h), and ketamine (2.4 mg/kg/h). The RM was preceded by an incremental PEEP titration and followed by a decremental PEEP titration, both at a constant airway pressure difference (deltaP) of 20 cm H2O. The RM consisted of a stepwise increase in deltaP by 25, 30, and 35 cm H2O obtained by increasing peak inspiratory pressure (PIP) to 45, 50, and 55 cm H2O, while maintaining PEEP at 20 cm H2O. Hemodynamic and pulmonary variables were analyzed at every step of the PEEP titration-RM. RESULTS: During the PEEP titration-RM, there was a significant increase in PaO 2 (+12%), dynamic compliance (+ 62%), and heart rate (+17%) and a decrease in shunt (-19%) and mean arterial blood pressure (-21%) was recorded. Cardiac output remained stable. CONCLUSIONS AND CLINICAL RELEVANCE: Although baseline oxygenation was high, Pa(O2) and dynamic compliance further increased during the RM. Despite the use of high PIP and PEEP and a high tidal volume, limited cardiovascular compromise was detected. A PEEP titration-RM may be used to improve oxygenation in anesthetized ponies. During stable hemodynamic conditions, PEEP titration-RM can be performed with acceptable adverse cardiovascular effects.     

Effects of frequency and airway pressure on gas exchange during interrupted high-frequency, positive-pressure ventilation in ponies

Cardiovascular effects and pulmonary gas exchange were compared during conventional mechanical ventilation (CMV) and interrupted high-frequency, positive-pressure ventilation (IHFPPV) in 6 anesthetized ponies in dorsal recumbency. When the peak airway pressure (Paw) was held constant at control values attained during CMV (18 to 20 cm of H2O), and the ventilator frequency of IHFPPV was varied over the range, 2.5 to 12.5 Hz, significant (P less than 0.05) changes from control values were observed only in the ratio of dead-space volume to tidal volume (VD/VT) and in the respiratory minute volume (VE). The mean (+/- SEM) carbon dioxide excretion (VCO2) was 2.12 +/- 0.1 ml/kg/min during IHFPPV. Dead-space ventilation ranged from 40 to 73.7% of total ventilation and increased directly with increasing frequency. The VE also increased, from 89 ml/kg/min at a ventilatory frequency of 2.5 Hz to 145 ml/kg/min at a frequency of 12.5 Hz. Maintaining the frequency of IHFPPV constant at 12.5 Hz and increasing the Paw over the range of 5 to 30 cm of H2O caused significant (P less than 0.05) changes in arterial partial pressure of O2 (PaO2), VCO2, pulmonary shunt fraction (QS/QT), VE, arterial-alveolar differences in oxygen tension (AaDO2), VD/VT, and cardiac output, compared with CMV. The PaO2 and the VCO2 increased linearly with increasing Paw. With increasing Paw, VD/VT decreased directly with increasing Paw from 98 to 69.3%. Gas exchange at a Paw of 15 cm of H2O during IHFPPV was equivalent to conditions at Paw of 20 cm of H2O during CMV. At a higher Paw during IHFPPV, improvements over control values were observed in gas exchange.     

Minimally invasive cholecystostomy in the dog: evaluation of placement techniques and use in extrahepatic biliary obstruction

Objective— To evaluate 4 methods of cholecystostomy catheter placement and to report on laparoscopic (Lap) cholecystostomy for the management of extrahepatic biliary obstruction (EHBO) in 3 dogs.
Study Design— Experimental study and clinical report.
Animals— Cadaveric dogs (n=20); 2 canine and 1 feline patient.
Methods— Pigtail cholecystostomy catheters were inserted in 20 canine cadavers using ultrasound (US) or Lap guidance. Insertion routes were either transperitoneal or transhepatic. Methods studied included Lap-transperitoneal, US-transperitoneal, US-transhepatic, and US-Seldinger (n=5 dogs/group). Insertion success, pleural penetration, and insertion site leakage (Lap-transperitoneal group) were evaluated. Three clinical EHBO cases were treated by Lap-transperitoneal technique.
Results— Insertion success was 100% by Lap-transperitoneal but 0% with US-transperitoneal and US-Seldinger methods. US-transhepatic yielded 3 of 5 successful placements. The pleura was penetrated in all US-transhepatic and US-Seldinger insertions. Leakage pressure for Lap-transperitoneal catheters averaged 75 cm H₂O (±20 cm H₂O). Lap-transperitoneal cholecystostomy resulted in marked improvement in 2 dogs, but the catheter became obstructed in the cat. One dog spontaneously regained common bile duct patency and the remaining 2 animals had successful cholecystoenterostomy.
Conclusions— In cadaver testing, the Lap-transperitoneal cholecystostomy method was superior based on high insertion success with no pleural penetration. In 2 clinical cases, Lap-transperitoneal placement successfully provided biliary drainage for patient stabilization.
Clinical Relevance— The role for temporary cholecystostomy has yet to be established, but may aid patient stabilization and mortality reduction in EHBO.     

Morphologic Effects of Experimental Distention of Equine Small Intestine

The morphologic effects of induced intraluminal hydrostatic pressures (IHPs) of 0, 9, and 18 cm H₂O were evaluated in 33 isolated equine jejunal segments. Fifteen segments were distended with Tyrode's solution for 1 hour and nine segments for 4 hours. Tyrode's solution was added as needed to maintain the prescribed pressures. Nine other segments were left undisturbed for 4 hours after the initial distention period. On decompression of the intestinal segments, progressive peristaltic contractions resumed in all segments. Evaluation of intestinal sections by light microscopy and transmission electron microscopy showed edema of the villi and submucosa and separation of the epithelial cells adjacent to the basement membrane in all segments. The epithelial cell necrosis found in ischemic intestine was not seen. This study indicates that the necrosis found at the villous tips in distended sections of small intestine remote from the site of obstruction cannot be reproduced by IHP increases of 4 hours duration.     

Butorphanol Tartrate for Partial Reversal of Oxymorphone-Induced Postoperative Respiratory Depression in the Dog

A randomized, blinded, crossover study was designed to evaluate the respiratory, cardiovascular, and behavioral effects of butorphanol given postoperatively to oxymorphone-premedicated and surgically stimulated dogs. Nine healthy adult dogs were premedicated intramuscularly with atropine (0.04 mg/kg), acepromazine (0.10 mg/kg), and oxymorphone (0.2 mg/kg). Anesthesia was induced with thiamylal (12 mg/kg) and maintained with halothane in oxygen. According to the protocol of a concurrent study, all dogs had percutaneous endoscopic gastrostomy (PEG) feeding tubes placed during the first anesthetic episode and removed during the second anesthetic episode. All dogs received postoperatively either butorphanol tartrate (0.2 mg/kg) or an isovol-umetric dose of saline placebo, both given intravenously. Respiratory rate (RR), tidal volume (TV), minute ventilation (MV), end-tidal CO₂ concentration (ET_CO2). heart rate (HR), and indirect diastolic (DP), systolic (SP) and mean arterial (MAP) blood pressures were measured at times 0, 2, 5, 10, 20, 40, 80, and 120 minutes after injection. The time from injection of the test drug until extubation was recorded. RR, MV, HR, and DP were significantly ( P < .05) increased, while ET_co2 was significantly decreased, for a minimum of 30 minutes in butorphanol-treated dogs compared with saline controls. TV, SP, and MAP were transiently (≤15 minutes) increased in butorphanol-treated dogs compared with saline controls. There was no significant difference between the times to extubation in the butorphanol-treated dogs versus the saline control dogs.     

Pulmonary mechanics during treadmill exercise in race ponies

Exercise-induced variations in their ventilatory mechanics were studied in 8 healthy ponies 4.2±1.4 years old and weighing 282±11 kg. Airflow (V), tidal volume (VT), esophageal pressure, mask pressure and electrocardiogram were simultaneously recorded before, during and after a treadmill (incline 8.3°) exercise which consisted of 2 min walking (1.5 m.sec^-1), 3 min slow trotting (3.0 m.sec^-1) and 3 min fast trotting (3.5 m.sec^-1). The results of three consecutive daily measurements were averaged for each pony.Heart rate, minute volume (Ve), respiratory frequency (f) and peak inspiratory and expiratory V, mean inspiratory and expiratory V, and peak to peak changes in traspulmonary pressure (maxdPtp) increased linearly and significantly with increasing velocity (v) (R²=0.99). Tidal volume and the inspiratory time to total breathing time ratio showed a curvilinar relation with v (R²=0.99). Minute volume, maxdPtp, total pulmonary resistance (RL) and VT increased from rest to fast trot 6.7, 5.7, 1.5 and 1.6 times respectively. When the ponies stopped all these values decreased significantly. After 5 min recovery, the Ve was approximately doubled, VT and max dPtp unchanged and RL 30% smaller than their respective resting values. The exercise-induced increase in Ve was achieved by an increase in f at both low and high intensity of work.     

Failure of subtotal arytenoidectomy to improve upper airway flow mechanics in exercising standardbreds with induced laryngeal hemiplegia

Upper airway flow mechanics and arterial blood gas measurements were used to assess the efficacy of subtotal arytenoidectomy for treatment of induced left laryngeal hemiplegia in horses. Measurements were collected with the horses at rest, and trotting or pacing on a treadmill (6.38 degrees incline) at speeds of 4.2 and 7.0 m/s. Experimental protocols were performed after right common carotid artery exteriorization (baseline), after left recurrent laryngeal neurectomy (LRLN), and after left subtotal arytenoidectomy. At baseline, increasing treadmill speed progressively increased peak inspiratory and expiratory flow (VImax and VEmax, respectively), peak inspiratory and expiratory transupper airway pressure (PuI and PuE, respectively), respiratory frequency (f), tidal volume (VT), minute volume (VE), and heart rate. Inspiratory and expiratory times (TI and TE, respectively) and arterial oxygen tension (PaO2) decreased with increased treadmill speed; inspiratory and expiratory impedance (ZI and ZE, respectively) did not change. After LRLN, VImax, f, and PaO2 significantly (P less than 0.05) decreased at exercise, whereas PuI, TI, and ZI significantly increased. Minute volume decreased at exercise after LRLN, but the changes were not significant; LRLN had no effect on VEmax, PuE, ZE, heart rate, arterial carbon dioxide tension (PaCO2), or VT. Subtotal arytenoidectomy did not improve upper airway flow mechanics or blood gas measurements impaired by laryngeal hemiplegia.