Transpulmonary ultrasound dilution is an acceptable technique for cardiac output measurement in anesthetized pigs.

OBJECTIVE: To evaluate cardiac output (CO) measurements using transpulmonary ultrasound (TPUD) technology and compare results with those of the gold standard, pulmonary arterial catheter thermodilution (PACTD), in 6 healthy anesthetized pigs during acute hemodynamic changes caused by manipulation of the blood volume. ANIMALS: 6 healthy male Landrace pigs. PROCEDURES: Over a period of 1 week, pigs were anesthetized with isoflurane, mechanically ventilated, and underwent instrumentation in dorsal recumbency. They were subjected to sequential experimental states during which the blood volume was manipulated so that the animals transitioned from normovolemia to hypovolemia (20% and 40% of blood volume depletion), back to normovolemia (autologous blood transfusion), and then to hypervolemia (following colloid bolus). During each volume state, CO measurements were compared between TPUD and PACTD. RESULTS: The mean ± SD relative bias between TPUD and PACTD was 7.71% ± 21.2% with limits of agreement -33.9% to 49.3%, indicating TPUD slightly underestimated CO values, compared with values obtained with PACTD. The mean ± SD of the bias between the 2 methods was 0.13 ± 0.5 L/min. Only 5 of 36 (13.9%) TPUD CO measurements had an absolute value of relative bias > 30%. The percentage error calculated for TPUD was 29.4%. CLINICAL RELEVANCE: Results suggested that TPUD measurements have acceptable agreement with PACTD measurements. Moreover, TPUD exhibits promising potential in being used interchangeably with PACTD for future hemodynamic research involving swine as species of interest.

Chest compression by two-thumb encircling method generates higher carotid artery blood flow in swine infant model of cardiac arrest.

OBJECTIVE: Two-Thumb(TT) technique provides superior quality chest compressions compared with Two-Finger(TF) in an instrumented infant manikin. Whether this translates to differences in blood flow, such as carotid arterial blood flow(CABF), has not been evaluated. We hypothesized that TT-CPR generates higher CABF and Coronary Perfusion Pressure(CPP) compared with TF-CPR in a neonatal swine cardiac arrest model. METHODS: Twelve anesthetized & ventilated piglets were randomized after 3 min of untreated VF to receive either TT-CPR or TF-CPR by PALS certified rescuers delivering a compression rate of 100/min. The primary outcome, CABF, was measured using an ultrasound transonic flow probe placed on the left carotid artery. CPP was calculated and end-tidal CO2(ETCO2) was measured during CPR. Data(mean ± SD) were analyzed and p-value ≤0.05 was considered statistically significant. RESULTS: Carotid artery blood flow (% of baseline) was higher in TT-CPR (66.2 ± 35.4%) than in the TF-CPR (27.5 ± 10.6%) group, p = 0.013. Mean CPP (mm Hg) during three minutes of chest compression for TT-CPR was 12.5 ± 15.8 vs. 6.5 ± 6.7 in TF-CPR, p = 0.41 and ETCO2 (mm Hg) was 29.0 ± 7.4 in TT-CPR vs. 20.7 ± 5.8 in TF-CPR group, p = 0.055. CONCLUSION: TT-CPR achieved more than twice the CABF compared with TF-CPR in a piglet cardiac arrest model. Although CPP and ETCO2 were higher during TT-CPR, these parameters did not reach statistical significance. This study provides direct evidence of increased blood flow in infant swine using TT-CPR and further supports that TT chest compression is the preferred method for CPR in infants.

Cardiac Monitoring in Horses.

Monitoring variables of cardiac performance in horses is challenging owing to patient size, temperament, and anatomic peculiarities. Blood pressure is a major determinant of afterload, but it is not a reliable surrogate of cardiac performance and tissue perfusion. Cardiac output, together with arterial and venous oxygen content, provides insight as to the adequacy of delivery of blood and oxygen to the body as a whole and can be used to gauge the fluid responsiveness and cardiovascular status of the patient. Measurement of intracardiac pressures serves to assess cardiac filling pressures, myocardial performance, and vascular resistance.

Use of a modified passive leg-raising maneuver to predict fluid responsiveness during experimental induction and correction of hypovolemia in healthy isoflurane-anesthetized pigs.

OBJECTIVE To evaluate the use of a modified passive leg-raising maneuver (PLRM) to predict fluid responsiveness during experimental induction and correction of hypovolemia in isoflurane-anesthetized pigs. ANIMALS 6 healthy male Landrace pigs. PROCEDURES Pigs were anesthetized with isoflurane, positioned in dorsal recumbency, and instrumented. Following induction of a neuromuscular blockade, pigs were mechanically ventilated throughout 5 sequential experimental stages during which the blood volume was manipulated so that subjects transitioned from normovolemia (baseline) to hypovolemia (blood volume depletion, 20% and 40%), back to normovolemia, and then to hypervolemia. During each stage, hemodynamic variables were measured before and 3 minutes after a PLRM and 1 minute after the pelvic limbs were returned to their original position. The PLRM consisted of raising the pelvic limbs and caudal portion of the abdomen to a 15° angle relative to the horizontal plane. RESULTS Hemodynamic variables did not vary in response to the PLRM when pigs were normovolemic or hypervolemic. When pigs were hypovolemic, the PLRM resulted in a significant increase in cardiac output and decrease in plethysomographic variability index and pulse pressure variation. When the pelvic limbs were returned to their original position, cardiac output and pulse pressure variation rapidly returned to their pre-PLRM values, but the plethysomographic variability index did not. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a modified PLRM might be useful for identification of hemodynamically unstable animals that are likely to respond to fluid therapy. Further research is necessary to validate the described PLRM for prediction of fluid responsiveness in clinically ill animals.

Assessment of agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scoring the recovery of horses from anesthesia by use of subjective grading scales and development of a system for evaluation of the recovery of horses from anesthesia by use of accelerometry.

OBJECTIVE To evaluate agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scores determined by use of a simple descriptive scale (SDS) or a composite grading scale (CGS) for quality of recovery of horses from anesthesia and to investigate use of 3-axis accelerometry (3AA) for objective evaluation of recovery. ANIMALS 12 healthy adult horses. PROCEDURES Horses were fitted with a 3AA device and then were anesthetized. Eight diplomates evaluated recovery by use of an SDS, and 7 other diplomates evaluated recovery by use of a CGS. Agreement was tested with κ and AC1 statistics for the SDS and an ANOVA for the CGS. A library of mathematical models was used to map 3AA data against CGS scores. RESULTS Agreement among diplomates using the SDS was slight (κ = 0.19; AC1 = 0.22). The CGS scores differed significantly among diplomates. Best fit of 3AA data against CGS scores yielded the following equation: RS = 9.998 × SG0.633 × ∑UG0.174, where RS is a horse's recovery score determined with 3AA, SG is acceleration of the successful attempt to stand, and ∑UG is the sum of accelerations of unsuccessful attempts to stand. CONCLUSIONS AND CLINICAL RELEVANCE Subjective scoring of recovery of horses from anesthesia resulted in poor agreement among diplomates. Subjective scoring may lead to differences in conclusions about recovery quality; thus, there is a need for an objective scoring method. The 3AA system removed subjective bias in evaluations of recovery of horses and warrants further study.

Perioperative Fluid Therapy.

Anesthesia can lead to pathophysiologic changes that dramatically alter the fluid balance of the body compartments and the intravascular space. Fluid administration can be monitored and evaluated using static and dynamic indexes. Guidelines for fluid rates during anesthesia begin with 3 mL/kg/h in cats and 5 mL/kg/h in dogs. If at all possible, patients should be stabilized and electrolyte disturbances should be corrected before general anesthesia.

Ventricular Fibrillation-Induced Cardiac Arrest Results in Regional Cardiac Injury Preferentially in Left Anterior Descending Coronary Artery Territory in Piglet Model.

Objective. Decreased cardiac function after resuscitation from cardiac arrest (CA) results from global ischemia of the myocardium. In the evolution of postarrest myocardial dysfunction, preferential involvement of any coronary arterial territory is not known. We hypothesized that there is no preferential involvement of any coronary artery during electrical induced ventricular fibrillation (VF) in piglet model. Design. Prospective, randomized controlled study. Methods. 12 piglets were randomized to baseline and electrical induced VF. After 5 min, the animals were resuscitated according to AHA PALS guidelines. After return of spontaneous circulation (ROSC), animals were observed for an additional 4 hours prior to cardiac MRI. Data (mean ± SD) was analyzed using unpaired t-test; p value ≤ 0.05 was considered statistically significant. Results. Segmental wall motion (mm; baseline versus postarrest group) in segment 7 (left anterior descending (LAD)) was 4.68 ± 0.54 versus 3.31 ± 0.64, p = 0.0026. In segment 13, it was 3.82 ± 0.96 versus 2.58 ± 0.82, p = 0.02. In segment 14, it was 2.42 ± 0.44 versus 1.29 ± 0.99, p = 0.028. Conclusion. Postarrest myocardial dysfunction resulted in segmental wall motion defects in the LAD territory. There were no perfusion defects in the involved segments.

Assessment of hemostatic changes in a model of acute hemorrhage in dogs.

OBJECTIVE: To evaluate hemostatic changes following experimental acute hemorrhage in dogs using traditional coagulation tests (eg, platelet count, prothrombin time [PT], and activated partial thromboplastin time [aPTT]), kaolin-activated thromboelastography (TEG), and whole blood multiple electrode impedance platelet aggregometry. DESIGN: Prospective study. SETTING: Research laboratory. ANIMALS: Five Beagles. INTERVENTIONS: Dogs were anesthetized prior to obtaining blood samples for baseline PCV, total plasma protein (TPP), arterial blood-gas, platelet count, PT, aPTT, TEG, fibrinogen, and aggregometry. Blood was obtained at 4 additional time points, following 20% blood volume loss, 40% blood volume loss, 60 minutes of sustained hypotension, and after autologous blood transfusion. In addition, heart rate and direct arterial blood pressure were measured at each time point. MEASUREMENTS AND MAIN RESULTS: Significant decreases were noted for PCV (P = 0.048), TPP (P < 0.0001), and arterial blood pressures (P < 0.0001) over time. Platelet count did not change significantly (P = 0.879), but platelet function was decreased following hemorrhage when arachidonic acid (P = 0.004) and ADP (P = 0.008) were used as agonists. The TEG variables R (P = 0.030), MA (P = 0.043), and G (P = 0.037) were significantly, albeit mildly, changed following hemorrhage. Significant prolongations in PT (P < 0.0001) and aPTT (P = 0.041), and decreases in fibrinogen concentration (P = 0.002) were also seen. CONCLUSION: Platelet dysfunction occurred following hemorrhage in this model, despite a stable platelet count. Additionally, significant changes associated with hemorrhage were documented in aPTT, fibrinogen, and MA. Platelet function testing in dogs with naturally occurring hemorrhage warrants further investigation.

Utstein-style guidelines on uniform reporting of in-hospital cardiopulmonary resuscitation in dogs and cats. A RECOVER statement.

OBJECTIVE: To provide recommendations for reviewing and reporting clinical in-hospital cardiopulmonary resuscitation (CPR) events in dogs and cats and to establish nonambiguous operational definitions for CPR terminology. DESIGN: Consensus guidelines. SETTING: International, academia, referral practice, general practice, and human medicine. METHODS: An international veterinary Utstein task force was convened in April 2013 in San Francisco to determine the scope of the project, the variables to be reported, their definitions, and a reporting template. Factors that were essential for meaningful data reporting and were amenable to accurate collection (ie, core variables) and additional variables useful for research projects and hypothesis generation (ie, supplemental variables) were defined. Consensus on each item was either achieved during that meeting or during the subsequent online modified Delphi process and dialogue between task force members. RESULTS: Variables were defined and categorized as hospital, animal, event (arrest), and outcome variables. This report recommends a template for standardized reporting of veterinary in-hospital CPR studies involving dogs or cats. Core elements include the suspected cause(s) and location of arrest, first rhythm identified, the occurrence of return of spontaneous circulation (ROSC) of more than 30 seconds (any ROSC) or more than 20 minutes (sustained ROSC), survival to discharge, and functional capacity at discharge. If CPR is discontinued or the patient is euthanized by owner request, a reason is reported. The task force suggests a case report form to be used for individual resuscitation events. CONCLUSIONS: The availability of these veterinary small animal CPR reporting guidelines will encourage and facilitate high-quality veterinary CPR research, improve data comparison between studies and across study sites, and serve as the foundation for veterinary CPR registries.

In vitro evaluation of bursting pressure and intestinal luminal area of three jejunostomy tube placement techniques in dogs.

OBJECTIVE: To compare pursestring, Witzel (seromuscular inversion), and seromuscular incision jejunostomy tube placement techniques in vitro. SAMPLE: Jejunal specimens from 10 dogs. PROCEDURES: Jejunal segments (50 cm) were harvested immediately prior to euthanasia from 10 mixed-breed dogs Specimens were harvested with the orad and aborad ends clamped and stored in saline (0.9% NaCl) solution-soaked towels during instrumentation. Three jejunostomy tubes were placed via 3 techniques (pursestring, Witzel, and seromuscular incision), and 2 double lumen central venous catheters were placed at each intestinal end for luminal filling and leak testing. Intestinal luminal area was measured ultrasonographically with specimens suspended in a warm undyed saline solution bath with the intestinal lumen filled with dyed saline solution (intraluminal pressure, 6 mm Hg). Leak testing was performed by means of infusion of dyed saline solution (4 mL/min) until each jejunostomy site failed. Intestinal luminal area and leakage pressure were compared between the 3 tube placement techniques. RESULTS: The Witzel and seromuscular incision techniques decreased the intestinal luminal area measured at the tube insertion site, albeit nonsignificantly. For the seromuscular incision technique, a significant decrease in intestinal luminal area at the intraluminal site of measurement was found. For 2/30 specimens (1/10 pursestring and 1/10 seromuscular incision), failure occurred at pressures within the range of previously reported peak peristaltic pressure for dogs. Failure occurred at supraphysiologic peristaltic pressures for the remaining 28 specimens, including all 10 specimens for the Witzel technique. CONCLUSIONS AND CLINICAL RELEVANCE: In this in vitro study, all specimens for the Witzel technique withstood physiologic peristaltic pressures during leak testing. Both tunneling techniques (Witzel and seromuscular incision) created a decrease in intestinal luminal area. Further investigation, including in vivo testing, is indicated to evaluate the clinical relevance of these findings.

Cardiopulmonary Effects of Laparoscopic Ovariectomy of Variable Duration in Cats.

OBJECTIVE: To evaluate the cardiopulmonary effects of low-pressure (6 mmHg) peritoneal insufflation of varying duration in healthy cats during ovariectomy (OVE). STUDY DESIGN: Prospective, randomized study. ANIMALS: Female cats (n = 24). METHODS: After anesthesia induction, cats had short (Short LAP; n = 8) or long duration (Long LAP; n = 8) laparoscopic ovariectomy, or Open OVE (Open; n = 8) for comparison. Hemodynamic and pulmonary measurements were recorded after induction of anesthesia (T0), 5 minutes after abdominal insufflation had reached 6 mmHg of pressure (T1), after the 2nd ovary had been resected (T2), after abdominal decompression (T3), and at the end of anesthesia, after abdominal closure (T4). Hemodynamic and pulmonary variables were compared between groups. RESULTS: Low-pressure abdominal insufflation caused cardiopulmonary changes in cats. At T1 and T2, Long LAP and Short LAP caused a significant change in PvCO2 and RC when compared with Open. During T3, RC was lower only in Long LAP. At T2, there was decrease in SV, but not CO for Long LAP when compared with Open. CONCLUSIONS: Duration of insufflation was associated with worsening of negative cardiopulmonary effects; however, these effects were reversible and resolved by the end of the procedure.

Accuracy of calculated arterial saturation in oxygen in neonatal foals and effects of monitor, sensor, site of sensor placement, and degree of hypoxemia on the accuracy of pulse oximetry.

OBJECTIVES: To (1) assess the agreement between calculated values for arterial hemoglobin saturation of oxygen (SaO2 ) and values obtained by co-oximetry, (2) assess the accuracy of 2 pulse oximetry monitors for measurement of SaO2 in foals, and for each monitor, and (3) determine the optimal combination of sensor type and site of sensor placement for SaO2 monitoring. DESIGN: Prospective experimental study. SETTING: University teaching hospital. ANIMALS: Six neonatal foals. INTERVENTIONS: Foals were anesthetized with isoflurane and SaO2 was manipulated by varying the inspired fraction of oxygen. SaO2 was calculated from oxygen tension or measured by pulse oximetry using 2 monitors equipped with transmission or reflectance sensors attached to the foal's tongue, lip, ear, or inserted rectally (reflectance sensor only). SaO2 values measured by co-oximetry were used as the gold standard to calculate bias. MEASUREMENTS AND MAIN RESULTS: Mean (±SD) SaO2 determined by co-oximetry was 65.2% ± 11.8%, 85.4% ± 2.5%, and 97.2% ± 0.4% at the low, intermediate, and high SaO2 level, respectively. Sensors attached to the ear failed to provide SaO2 readings for most attempts. Reflectance sensors placed on the lip or rectally gave significantly larger biases at low SaO2 (-17.0% and -23.6%, respectively) than at higher levels. Bias of all other combinations of monitors, sensors, and sites (-1.8 to -4.1%) was not significantly influenced by the level of SaO2 or different from each other. The bias of calculated saturation was similar to that of pulse oximetry. CONCLUSIONS: Transmission sensors placed on the lip or tongue or reflectance sensors placed on the tongue give the most accurate assessment of SaO2 in anesthetized neonatal foals. Calculated saturation is not more accurate than pulse oximetry to estimate SaO2 .

Atrial septal pacing in small dogs: a pilot study.

OBJECTIVE: To determine the feasibility of atrial septal pacing via a delivery catheter-guided small non-retracting helix pacing lead. ANIMALS: Six healthy beagles (8.3-12.9 kg). METHODS: Using single plane fluoroscopic guidance, Medtronic(®) 3830 SelectSecure leads were connected to the atrial septum via Medtronic® Attain Select® II standard 90 Left Heart delivery catheter. Pacing threshold and lead impedance were measured at implantation. The Wenckebach point was tested via atrial pacing up to 220 paced pulses per minute (ppm). Thoracic radiographs were performed following implantation to identify the lead position, and repeated at 24 h, 1 month, and 3 months post-operatively. RESULTS: Macro-lead dislodgement occurred in two dogs at 24 h and in three dogs at one-month post-implantation. Lead impedance, measured at the time of implantation, ranged from 583 to 1421 Ω. The Wenckebach point was >220 ppm in four of the six dogs. The remaining two dogs had Wenckebach points of 120 and 190 ppm. CONCLUSIONS: This pilot study suggests the selected implantation technique and lead system were inadequate for secure placement in the atrial septum of these dogs. The possible reasons for inadequate stability include unsuitable lead design for this location, inadequate lead slack at the time of implantation and inadequate seating of the lead as evidenced by low impedance at the time of implantation. Other implantation techniques and/or pacing leads should be investigated to determine the optimal way of pacing the atria in small breed dogs that are prone to sinus node dysfunction.

Comparison of cardiac output determined by an ultrasound velocity dilution cardiac output method and by the lithium dilution cardiac output method in juvenile horses with experimentally induced hypovolemia.

OBJECTIVE: To assess the accuracy of an ultrasound velocity dilution cardiac output (UDCO) method, compared with that of the lithium dilution cardiac output (LiDCO) method, for determination of cardiac output (CO) in juvenile horses with experimentally induced hypovolemia. ANIMALS: 12 anesthetized 2- to 6-month-old horses. PROCEDURES: For each anesthetized horse, CO was determined by the LiDCO and UDCO methods prior to any intervention (baseline state), after withdrawal of approximately 40% of the horse's blood volume (low CO state), after maintenance of hypovolemia and infusion of norepinephrine until mean arterial blood pressure was equal to baseline value (high CO state), and after further infusion of norepinephrine and back-transfusion of withdrawn blood (posttransfusion state). For each of the 4 hemodynamic situations, CO and calculated cardiac index (CI) values were obtained by each method in duplicate (8 pairs of measurements/horse); mean values for each horse and overall mean values across all horses were calculated. Agreement between CI determined by each method (96 paired values) was assessed by Bland-Altman analysis. RESULTS: For the UDCO method-derived CI measurements among the 12 horses, mean ± SD bias was -4 ± 11.3 mL/kg/min (95% limits of agreement, -26.1 to 18.2 mL/kg/min) and mean relative bias was -10.4 ± 21.5% (95% limits of agreement, -52.6% to 31.8%). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that, compared with the LiDCO method, the UDCO method has acceptable clinical usefulness for determination of CO in foals.

Thromboelastographic evaluation of hemostatic function in dogs treated for crotalid snake envenomation.

OBJECTIVE: To characterize the overall hemostatic changes in dogs envenomated by crotaline snakes via kaolin-activated thromboelastography (TEG), and to determine any prognostic/monitoring value from a TEG tracing on presentation, as well as during treatment with antivenom therapy. DESIGN: Prospective observational, cohort study. SETTING: University teaching hospital and primary emergency hospital. ANIMALS: Thirty-eight dogs envenomated by crotaline snakes. INTERVENTIONS: TEG tracings were evaluated on presentation to the hospital (pre) as well as immediately following (post) and 12 hours (12 h post) after antivenom treatment, if administered. MEASUREMENTS AND MAIN RESULTS: At presentation, data were available for 38 dogs envenomated by crotaline snakes. Twenty dogs were in Group 1 (Antivenin [Crotalidae] Polyvalent antivenom), 12 dogs were in Group 2 (Antivipmyn antivenom), and 6 dogs in Group 3 that were not treated with antivenom. The average number of vials administered to group 1 and 2 were equal at 2.2. On presentation, based on a G value < TEG reference range, 15/38 (39%) of the dogs had hypocoagulable TEG tracings. There was a significant increase in G and MA value from the pre and 12 hour post measurement (P = 0.0001 and 0.0003, respectively), as well as from the post to 12 hour post measurement (P = 0.003 and, 0.014, respectively). During the study, 5 of 38 dogs died (13%) and of the dogs that died, 4/5 (80%) had angle and MA equal to zero on presentation. A decreased G and MA were significantly associated with mortality (P = 0.02 and 0.04, respectively). CONCLUSIONS: A hypocoagulable TEG tracing, particularly a decreased G value and MA, is associated with an increased mortality in crotaline snake envenomation. G and MA also demonstrate a significant increase over treatment time.

Comparison of surgical variables in cats undergoing single-incision laparoscopic ovariectomy using a LigaSure or extracorporeal suture versus open ovariectomy.

OBJECTIVE: To evaluate the applicability of single-incision laparoscopic ovariectomy (SILOVE) in cats using a single-incision laparoscopic port (SILP); to compare surgical time, complications, and postoperative pain after SILOVE using a LigaSure (SILOVE-LS) or extracorporeal suture (SILOVE-ECS), and open ovariectomy (open-OVE). STUDY DESIGN: Randomized, blinded, prospective study. ANIMALS: Healthy, domestic female cats (n = 24). METHODS: Cats underwent physical examination, packed cell volume, total solids and blood urea nitrogen analysis. Cats were randomly assigned to 1 of 3 groups: SILOVE-LS (n = 8), SILOVE-ECS (8) or open-OVE (8). Surgical time, complications, and postoperative pain scores were recorded. RESULTS: Single-incision laparoscopic ovariectomy was successful in (n = 8) SILOVE-LS cats and (n = 5) SILOVE-ECS cats. Surgical time was significantly longer for the SILOVE-ECS group compared with the SILOVE-LS (P < .0001) and open-OVE (P < .0001) groups, which were not different (P = .55). Complications were more frequent in the SILOVE-ECS group and removal of the SILP was required to complete ovariectomy in 3 cats. Cumulative 4-hour pain scores were not different between groups. CONCLUSIONS: Single-incision laparoscopic ovariectomy using a SILP is a feasible method for OVE in cats. Single-incision laparoscopic ovariectomy using an extracorporeal suture is more time consuming and associated with more complications than either the SILOVE-LS or open-OVE methods.

Evaluation of tissue oxygen saturation with near-infrared spectroscopy during experimental acute hemorrhagic shock and resuscitation in dogs.

OBJECTIVE: To evaluate tissue oxygen saturation (Sto2) by use of near-infrared spectroscopy in experimental acute hemorrhagic shock and resuscitation in dogs. ANIMALS: 14 healthy adult purpose-bred Beagles. PROCEDURES: Dogs were anesthetized with isoflurane via facemask, anesthesia was maintained with propofol and rocuronium bromide, and dogs were mechanically ventilated to maintain normocapnia. Dogs were studied under normovolemia (baseline), hypovolemia with target mean arterial blood pressure < 40 mm Hg achieved and maintained steady for 10 minutes (hypovolemia T1), then 20 minutes later (hypovolemia T2), following resuscitation with shed blood (after transfusion), and after administration of 20 mL of hetastarch/kg (hypervolemia). Conditions were executed sequentially during a single anesthetic episode, allowing stabilization between states (10 minutes). Hemoglobin concentration, mean arterial blood pressure, arterial blood gas concentrations, cardiac index, oxygen delivery indexed to body surface area, and Sto2 were monitored. RESULTS: From baseline to hypovolemia T1, there was a significant reduction in mean ± SD oxygen delivery index (619 ± 257 mL/min/m(2) to 205 ± 76 mL/min/m(2)) and Sto2 (94 ± 4.4% to 78 ± 12.2%). Following resuscitation, Sto2 (80 ± 8.5% vs 92 ± 6.45%) and oxygen delivery index (211 ± 73 mL/min/m(2) vs 717 ± 221 mL/min/m(2)) significantly increased, returning to baseline values. Hypervolemia had no effect on Sto2 or oxygen delivery index. A strong correlation (r = 0.97) was detected between mean oxygen delivery index and Sto2 across all time points. CONCLUSIONS AND CLINICAL RELEVANCE: Under the conditions of this study, there was a strong correlation between Sto2 and oxygen delivery, suggesting that Sto2 may be used to estimate oxygen delivery.

Evaluation of electrical nerve stimulation for epidural catheter positioning in the dog.

OBJECTIVE: To evaluate the accuracy of epidural catheter placement at different levels of the spinal cord guided solely by electrical nerve stimulation and resultant segmental muscle contraction. STUDY DESIGN: Prospective, experiment. ANIMALS: Six male and two female Beagles, age (1 ± 0.17 years) and weight (12.9 ± 1.1 kg). METHODS: Animals were anesthetized with propofol and maintained with isoflurane. An insulated epidural needle was used to reach the lumbosacral epidural space. A Tsui epidural catheter was inserted and connected to a nerve stimulator (1.0 mA, 0.1 ms, 2 Hz) to assess positioning of the tip at specific spinal cord segments. The catheter was advanced to three different levels of the spinal cord: lumbar (L2-L5), thoracic (T5-T10) and cervical (C4-C6). Subcutaneous needles were previously placed at these spinal levels and the catheter was advanced to match the needle location, guided only by corresponding muscle contractions. Catheter position was verified by fluoroscopy. If catheter tip and needle were at the same vertebral body a score of zero was assigned. When catheter tip was cranial or caudal to the needle, positive or negative numbers, respectively, corresponding to the number of vertebrae between them, were assigned. The mean and standard deviation of the number of vertebrae between catheter tip and needle were calculated to assess accuracy. Results are given as mean ± SD. RESULTS: The catheter position in relation to the needle was within 0.3 ± 2.0 vertebral bodies. Positive predictive values (PPV) were 57%, 83% and 71% for lumbar, thoracic and cervical regions respectively. Overall PPV was 70%. No significant difference in PPV among regions was found. CONCLUSION AND CLINICAL RELEVANCE: Placement of an epidural catheter at specific spinal levels using electrical nerve stimulation was feasible without radiographic assistance in dogs. Two vertebral bodies difference from the target site may be clinically acceptable when performing segmental epidural regional anesthesia.

Use of impedance threshold device in conjunction with our novel adhesive glove device for ACD-CPR does not result in additional chest decompression.

OBJECTIVE: To evaluate the hemodynamic effects of using an adhesive glove device (AGD) to perform active compression-decompression CPR (AGD-CPR) in conjunction with an impedance threshold device (ITD) in a pediatric cardiac arrest model. DESIGN: Controlled, randomized animal study. METHODS: In this study, 18 piglets were anesthetized, ventilated, and continuously monitored. After 3min of untreated ventricular fibrillation, animals were randomized (6/group) to receive either standard CPR (S-CPR), active compression-decompression CPR via adhesive glove device (AGD-CPR) or AGD-CPR along with an ITD (AGD-CPR+ITD) for 2min at 100-120compressions/min. AGD is delivered using a fingerless leather glove with a Velcro patch on the palmer aspect and the counter Velcro patch adhered to the pig's chest. Data (mean±SD) were analyzed using one-way ANOVA with pair wise multiple comparisons to assess differences between groups. p-Value≤0.05 was considered significant. RESULTS: Both AGD-CPR and AGD-CPR+ITD groups produced lower intrathoracic pressure (IttP, mmHg) during decompression phase (-13.4±6.7, p=0.01 and -11.9±6.5, p=0.01, respectively) in comparison to S-CPR (-0.3±4.2). Carotid blood flow (CBF, % of baseline mL/min) was higher in AGD-CPR and AGD-CPR+ITD (respectively 64.3±47.3%, p=0.03 and 67.5±33.1%, p=0.04) as compared with S-CPR (29.1±12.5%). Coronary perfusion pressure (CPP, mmHg) was higher in AGD-CPR and AGD-CPR+ITD (respectively 19.7±4.6, p=0.04 and 25.6±12.1, p=0.02) when compared to S-CPR (9.6±9.1). There was no statistically significant difference between AGD-CPR and AGD-CPR+ITD groups with reference to intra-thoracic pressure, carotid blood flow and coronary perfusion pressure. CONCLUSION: Active compression decompression delivered by this simple and inexpensive adhesive glove device resulted in improved cerebral blood flow and coronary perfusion pressure. There was no statistically significant added effect of ITD use along with AGD-CPR on the decompression of the chest.