Electrical velocimetry for noninvasive cardiac output and stroke volume variation measurements in dogs undergoing cardiovascular surgery

Objective

To compare electrical velocimetry (EV) noninvasive measures of cardiac output (CO) and stroke volume variation (SVV) in dogs undergoing cardiovascular surgery with those obtained with the conventional thermodilution technique using a pulmonary artery catheter.

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

ObjectiveTo 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 designProspective clinical study.AnimalsA group of 50 mechanically ventilated dogs with spontaneous hypotension during orthopedic or oncologic surgery.MethodsInvestigations 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.ResultsAfter 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).ConclusionsWhen 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 relevanceΔVTI and ΔVpeak can be used as indices of fluid responsiveness in anesthetized dogs.     

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.

Comparison between pulse pressure variation and systolic pressure variation measured from a peripheral artery for accurately predicting fluid responsiveness in mechanically ventilated dogs

ObjectiveTo compare pulse pressure variation (PPV) and systolic pressure variation (SPV) measured from a peripheral artery to predict fluid responsiveness in anesthetized healthy dogs.Study designProspective study.AnimalsA total of 39 dogs (13.8–26.8 kg) anesthetized with isoflurane for elective ovariohysterectomy.MethodsVentilation was controlled (tidal volume 12 mL kg^–1; 40% inspiratory pause). PPV and SPV were recorded from a dorsal pedal artery catheter using an automated algorithm. A fluid challenge (FC) with lactated Ringer’s solution (20 mL kg^–1 over 15 minutes) was administered once (21 animals) or twice (18 animals) before surgery. Increases in transpulmonary thermodilution stroke volume index > 15% from values recorded before each FC defined responders to volume expansion. Final fluid responsiveness status was based on the response to single FC or second FC. Predictive ability of PPV and SPV was compared by receiver operating characteristic (ROC) curve analysis and by the range of cut-off values associated with uncertain results (gray zone).ResultsAll animals after the single FC were responders; all animals administered two FCs were nonresponders after the second FC. The area under the ROC curve (AUROC) of PPV (0.968) did not differ from that of SPV (0.937) (p = 0.45). Best cut-off thresholds to discriminate responders from nonresponders were >11.7% (PPV) and >7.4 mmHg (SPV). The gray zone of PPV and SPV was 8.2–14.6% and 7.0–7.4 mmHg, respectively. The percentage of animals with PPV and SPV values within the gray zone was less for SPV (10.2%) than for PPV (30.8%).Conclusions and clinical relevancePPV and SPV obtained from the dorsal pedal artery are useful predictors of fluid responsiveness in dogs. Using an automated algorithm, SPV may more accurately predict fluid responsiveness than PPV, with responders identifiable by PPV > 14.6% and SPV > 7.4 mmHg.     

Evaluation of the dynamic predictors of fluid responsiveness in dogs receiving goal-directed fluid therapy

Objectives

Goal-directed fluid therapy (GDFT) based on pulse pressure variation (PPV) was used in anaesthetized dogs undergoing abdominal surgeries. The aims were 1) to evaluate the success rate of the PPV ≥13% in detecting fluid responsiveness [delta stroke volume (ΔSV) ≥10%]; 2) to assess the correlation between PPV, systolic pressure variation (SPV), Plethysmograph Variability Index (PVI) and central venous pressure (CVP) and 3) to establish the threshold value for the PVI that would predict a PPV value of ≥13% and indirectly discriminate responders from nonresponders to fluid therapy.

Perianesthetic morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery

ObjectiveTo evaluate and compare perioperative morbidity and mortality in dogs undergoing cervical and thoracolumbar spinal surgery.Study designProspective case series.Animals157 dogs undergoing cervical or thoracolumbar spinal surgery.MethodsData were collected sequentially on canine cases presented from the Neurology Section of the North Carolina State University Veterinary Teaching Hospital for anesthesia and surgery for cervical spinal cord disease. Simultaneously, data were collected on all thoracolumbar spinal surgery cases during the same time period. Data included signalment, drugs administered, surgical approach, disease process, cardiac arrhythmias during anesthesia, and outcome.ResultsData were collected from 164 surgical events in 157 dogs. There were 52 cervical approaches; four dorsal and 48 ventral. All thoracolumbar surgeries were approached dorsolaterally. Four dogs 4/52 (7.6%) undergoing a cervical approach did not survive to discharge. Two dogs (2/8; 25%) underwent atlanto-axial (AA) stabilization and suffered cardiovascular arrest and two dogs (2/38; 5.2%) undergoing cervical ventral slot procedures were euthanized following anesthesia and surgery due to signs of aspiration pneumonia. All dogs undergoing thoracolumbar surgery survived until discharge (112/112). Mortality in dogs undergoing cervical spinal surgery was greater compared with dogs undergoing thoracolumbar spinal surgery (p = 0.009), however, in dogs undergoing decompressive disc surgery, intraoperative death rates were not different between dogs undergoing a cervical compared with thoracolumbar approaches (p = 0.32) nor was there a significant difference in overall mortality (p = 0.07).Conclusion and clinical relevanceOverall, dogs undergoing cervical spinal surgery were less likely to survive until discharge compared with dogs undergoing thoracolumbar spinal surgery. Mortality in dogs undergoing cervical intervertebral disc decompression surgery was no different than for dogs undergoing thoracolumbar intervertebral disc decompression surgery. However, dogs undergoing cervical intervertebral disc decompression surgery should be considered at risk for aspiration pneumonia.     

Predictors of outcome in dogs undergoing thoracic surgery (2002–2011)

ObjectiveTo evaluate mortality in a canine population undergoing thoracic surgery and identify factors which may be associated with outcome.Study designRetrospective cohort study.Animals286 dogs anaesthetized for thoracic surgery at the Royal Veterinary College between June 2002 – June 2011.MethodsVariables examined included: signalment; ASA status; nature of disease; presence of co-morbidities; pre-anaesthetic oxygen requirement; surgical approach; anaesthesia management [anaesthetic agents; requirement for thoracocentesis; central venous pressure measurement; duration of surgery and anaesthesia; use of colloids, blood products, inotropes or neuromuscular blocking agents (NMBA)]. Outcome was defined as either non-survival to 24 hours after surgery or (having survived to 24 hours) to discharge. Univariate and multivariable logistic regressions were performed to identify risk factors associated with non-survival.ResultsOverall non-survival (excluding those euthanased) to discharge was 5.9%. Non-survival was 2.2% at 24 hours and 3.6% at time of discharge. Non-survival to 24 hours was associated with pre-anaesthetic oxygen requirement (odds ratio (OR) 12.2 [95% CI 1.8–84.5]) and NMBA use (OR 9.6 [95% CI 1.6–57.9]). Non-survival to discharge was associated with surgical duration, with surgeries >180 minutes having OR 16.9 [95% CI 2.0–144.0] compared to surgeries ≤90 minutes and blood product use (OR 4.6 [95% CI 1.3–14.6]). No association was found between ASA category and non-survival at 24 hours (OR 1.4 [95% CI 0.2–11.7]) or discharge (OR 4.4 [95% CI 0.6–34.3]). Significant associations were found between NMBA use and ASA category (p = 0.046), surgical duration (p = 0.002), use of colloids (p = 0.011), blood products (p = 0.001) and inotropes and/or vasopressors (p < 0.001).Conclusions and clinical relevanceVariables significantly associated with non-survival from canine thoracic surgery at 24 hours include NMBA use and pre-anaesthetic oxygen requirement. Blood product use and increasing surgical duration were associated with non-survival to hospital discharge. The associations may relate to the need for such products in the most complicated cases.     

Epidural anesthesia in dogs undergoing hindlimb orthopedic surgery: effects of two injection sites

This prospective clinical trial evaluated the effects of epidural anesthesia (EA) placed at the lumbosacral compared to the L5–L6 junction in dogs undergoing hindlimb orthopedic surgery. In all, 98 dogs were randomly assigned to receive injection at either L7–S1 (LS group) or L5–L6 (LL group) at the same local anesthetic regimen (1 mg/kg bupivacaine 0.5% and 0.1 mg/kg morphine 1%). Fentanyl (1 µg/kg) was the intraoperative rescue analgesia (iRA) administered if mean arterial pressure increased by 30% above pre-stimulation value. Procedural failure, iRA, hypotension, motor block resolution, and postoperative side effects were recorded. There were 7/47 (15%) epidural procedural failures in the LS group and 8/51 (16%) (P=1.00) in the LL group; iRA was administered in 21/40 (52%) LS group dogs and in 13/43 (30%) LL group dogs, respectively (P=0.047). The incidence of hypotension was 10/40 (25%) and 16/43 (37%) in the LS group and the LL group, respectively (P=0.25). Proprioceptive residual deficit at 8 hr after EA was recorded in 3/26 (12%) in group LS dogs and in 13/26 (50%) group LL dogs, respectively (P=0.01). The proprioceptive residual deficit at 24 hr in one dog (LL group) resolved within 36 hr. No episodes of postoperative urinary retention, pruritus or neurological damage were recorded. The L5–L6 EA decreased significantly iRA but delays the proprioceptive recovery time. Further studies are needed to determine whether a lower bupivacaine dose reduces the duration of the residual block retaining the same incidence of iRA.     

Continuous versus intermittent thermodilution for cardiac output measurement during alveolar recruitment manoeuvres in sheep

ObjectiveTo evaluate interchangeability of a thermodilution based STAT mode continuous cardiac output (CCO) measurement method with bolus thermodilution (BTD).Study designRandomized crossover study.AnimalsTen 9 month old healthy male sheep.MethodsEach sheep was anaesthetized twice for laparoscopy. On one occasion mechanical ventilation was used immediately after anaesthetic induction (IPPV treatment) and on the other occasion the start of IPPV was delayed and two periods of alveolar recruitment manoeuvres were also performed (RM treatment). Cardiac output (CO) was measured simultaneously with both CCO and BTD at 6 time points. Data were analysed using difference versus mean plots. A priori limits of acceptance were set at ±30% of the mean of every paired measurement. If <5% of the data fell outside of these limits (Chi-square test, p < 0.05) the interchangeability of methods was accepted. Proportions of data outside of these limits were also compared between treatments (Fisher's test, p < 0.05). Cardiac output data from each treatment and measurement method were also analyzed separately with one-factorial anova and Bonferroni test (p < 0.05).ResultsA total of 119 measurements were obtained. Cardiac output ranged from 1.9 to 10.4 L minute^?1 (CCO) and from 1.1 to 9.8 L minute^?1 (BTD). The bias and limits of agreement were 0.5 ± 1.9 L minute^?1. More than 5% of all data fell outside of the limits of acceptance (24/119), and a larger proportion fell outside of these limits in the RM (20/59) compared to the IPPV treatment (4/60). The Bonferroni test detected significant decreases of CO over time in both treatments when measured with BTD but not with CCO.Conclusions and clinical relevanceThe STAT mode CCO method is not interchangeable with BTD during acute haemodynamic changes caused by recruitment manoeuvres, thus the results of STAT mode CCO should be interpreted with caution because decreases in CO may not be detected.     

Analgesic comparison of meloxicam or ketoprofen for orthopedic surgery in dogs

OBJECTIVE: To compare the safety and efficacy of 2 analgesic protocols (preoperative meloxicam or intraoperative ketoprofen administration) during the first 24 hours after orthopedic surgery in dogs. STUDY DESIGN: Double-blind, prospective randomized clinical trial. ANIMALS: Sixty client-owned dogs. METHODS: Dogs with surgical orthopedic disorders were randomly separated into 2 groups: 30 dogs were administered 0.2 mg/kg meloxicam intravenously (IV) immediately before induction and 30 dogs were administered 2 mg/kg ketoprofen IV, 30 minutes before the end of surgery. Pain was assessed with a visual analog scale (VAS) and a cumulative pain score (CPS) preoperatively and at 30 minutes, 1, 2, 3, 4, 6, 8, and 24 hours after extubation. Selected serum biochemical variables were measured before and 24 hours after surgery and, buccal mucosal bleeding time (BMBT) and whole blood clotting time (WBCT) were measured before and 8 hours after surgery. Dogs were anesthetized with propofol and maintained on halothane in oxygen. Any complications were documented for 7 days after surgery. Results were compared between the 2 groups for significant differences in VAS scores (2-sample t-test) and in CPS (Wilcoxon's 2-sample test). Moreover, results were analyzed for significant differences in area under the curve (AUC) for VAS (2-sample t-test) and CPS (Wilcoxon's 2-sample test) among groups. To assess the effects of treatments on biochemical and coagulation functions, pre- and postoperative mean values of BMBT and WBCT were compared within both treatment groups (paired t-tests) and between both groups (2-sample t-test). RESULTS: No significant differences in pain response or coagulation were found between meloxicam- and ketoprofen-treated dogs. In both groups, alkaline phosphatase and alanine aminotransferase concentrations were significantly increased compared with baseline. No serious complications occurred. CONCLUSIONS: Preoperative administration of meloxicam is a safe and effective method of controlling postoperative pain for up to 24 hours in dogs undergoing orthopedic surgery. CLINICAL RELEVANCE: Analgesia after administration of preoperative meloxicam was comparable with administration of ketoprofen at the end of the surgery.     

Variables associated with outcome in dogs undergoing extrahepatic biliary surgery: 60 cases (1988-2002)

OBJECTIVE: To report clinical findings and define clinical variables associated with outcome in dogs undergoing extrahepatic biliary surgery. STUDY DESIGN: Retrospective study. ANIMALS: Sixty dogs that had extrahepatic biliary tract surgery. RESULTS: Primary diagnoses included necrotizing cholecystitis (36 dogs, 60%), pancreatitis (12 dogs, 20%), neoplasia (5 dogs, 8%), trauma (4 dogs, 7%), and gallbladder rupture from cholelithiasis without necrotizing cholecystitis (3 dogs, 5%). Bile peritonitis occurred in 19 (53%) dogs with necrotizing cholecystitis, 4 dogs with trauma, and 3 dogs with cholelithiasis without evidence of necrotizing cholecystitis. Cholecystectomy (37 dogs, 62%) and cholecystoduodenostomy (14 dogs, 23%) were the 2 most commonly performed procedures. Median hospitalization for survivors was 5 days (range, 1-15 days). There were 43 surviving dogs (72%) and 17 nonsurvivors (28%, 4 died, 13 euthanatized). Presence of septic bile peritonitis (P=.038), elevation in serum creatinine concentration (P=.003), prolonged partial thromboplastin times (PTTs; P=.003), and lower postoperative mean arterial pressures (P=.0001) were significantly associated with mortality. CONCLUSIONS: Extrahepatic biliary surgery is associated with high mortality and a relatively long hospitalization time for survivors. Cholecystectomy and cholecystoduodenostomy were the most common surgical procedures to treat the 4 major biliary problems (necrotizing cholecystitis, pancreatitis, neoplasia, and trauma) observed in this cohort of dogs. The relatively high mortality rate likely reflects the underlying diseases and their effects on the animal (septic bile peritonitis, higher serum creatinine, prolonged PTT, and lower postoperative mean arterial pressure) rather than complications of surgery. CLINICAL RELEVANCE: Septic bile peritonitis, preoperative elevated creatinine concentration, and immediate postoperative hypotension in dogs undergoing extrahepatic biliary tract surgery are associated with a poor clinical outcome. Adequate supportive care and monitoring in the perioperative period is critical to improve survival of dogs with extrahepatic biliary disease.     

Comparison of a method using the HemoCue near patient testing device with a standard method of haemorrhage estimation in dogs undergoing spinal surgery

Objective  To compare an estimate of blood loss obtained using measurements from the Hemocue photometer with a standard estimate in dogs undergoing spinal surgery.
Study design  Prospective clinical study.
Animals  Twenty-nine client-owned dogs.
Methods  During surgery, blood and all lavage fluids were collected in the suction container and on to swabs. To prevent blood clot formation in the suction container, 10 mL citrate-phosphate dextrose adenine (CPDA) was added. At the end of the procedure, the total volume in the suction container was recorded. It was shaken to ensure uniformity and a 5 mL sample tested with the HemoCue photometer. Blood loss in the suction container was calculated as follows: Blood in suction (mL) = volume in bottle (mL) × [suction haemoglobin (Hb) concentration (g dL⁻¹)/pre-operative Hb concentration (g dL⁻¹)]. This volume was added to the estimated volume of blood on the swabs (weight of soaked swabs minus that of dry swabs) to provide the Hemocue estimate of total blood loss. A standard haemorrhage estimate was performed using the volume of fluid in the suction container at the end of surgery in excess of the total volume of lavage fluid available, minus 10 mL CPDA. This volume was added to the estimated volume of blood on the swabs to provide the standard estimate of total blood loss. Data were analyzed with a paired t -test. Retrospective power calculations demonstrated an 80% power to detect a mean difference of 25 mL between the two methods with a level of significance of 0.05.
Results  There was no significant difference in calculated blood loss between the two methods ( p  = 0.8, mean difference: −2 mL, 95% CI: −20 to 16 mL).
Conclusions and clinical relevance  The HemoCue may be used to help estimate blood loss in dogs undergoing spinal surgery.     

Acid‐base and electrolyte balance following administration of three crystalloid solutions in dogs undergoing elective orthopaedic surgery

ObjectiveTo compare acid–base balance and incidence of hyperchloraemic metabolic acidosis following administration of three crystalloid solutions to dogs undergoing anaesthesia for orthopaedic surgery.Study designProspective, randomised, clinical study.AnimalsSixty dogs.MethodsDuring a non–standardised anaesthetic, 0.9% saline (S), Hartmann's solution (H) or a polyionic glucose–free maintenance solution (M) was administered IV at 10 mL kg^?1 hour^?1. Venous blood pH, PCO₂, PCV, total protein, urea, sodium, potassium and chloride concentrations were measured at induction of anaesthesia (T0) and after 2 hours of fluid therapy (T2). Base excess (BE), bicarbonate, corrected chloride concentration (corrCl), osmolality, change in plasma volume (PV) and strong ion gap (SIG) were calculated. Changes in variables within groups (1–sample Student's t–test/Wilcoxon signed rank test) and between groups (1–way anova/Kruskal–Wallis) were assessed. Data are presented as median (interquartile range). Significance was set at p < 0.05.ResultsNo significant differences existed between groups for pH, PCO₂, PCV, total protein, urea, potassium, corrCl, PV and SIG. Potassium significantly increased in all groups. Significant differences existed between groups S and M for BE, sodium, chloride, bicarbonate and osmolality, and between groups H and M for sodium and osmolality. Chloride concentration significantly changed from 116 (114–117) to 117 (116–119) mmol L^?1 in group S, 116 (115–118) to 115 (113–117) mmol L^?1 in group H and 116 (115–118) to 114 (113–118) mmol L^?1 in group M. In groups H and M, sodium and osmolality decreased, and BE and bicarbonate concentration increased significantly. Plasma volume increased by 28 (14–44)%, 25 (5–40)% and 24 (13–33)% in groups S, H and M, respectively.Conclusion and clinical relevanceHyperchloraemic metabolic acidosis did not develop after intraoperative 0.9% saline, Hartmann's solution or maintenance solution at 10 mL kg^?1 hour^?1 for 2 hours in dogs undergoing elective orthopaedic surgery. Bicarbonate and BE increased after Hartmann's and maintenance solutions. Increases in potassium concentration were unexplained.     

Clinical efficacy of dexmedetomidine combined with lidocaine for femoral and sciatic nerve blocks in dogs undergoing stifle surgery

ObjectiveTo evaluate the effects of dexmedetomidine administered perineurally or intramuscularly (IM) on sensory, motor function and postoperative analgesia produced by lidocaine for sciatic and femoral nerve blocks in dogs undergoing unilateral tibial tuberosity advancement surgery.Study designProspective, blinded, clinical study.AnimalsA group of 30 dogs.MethodsDogs were anaesthetized with acepromazine, propofol and isoflurane in oxygen/air. Electrolocation-guided femoral and sciatic nerve blocks were performed: group L, 0.15 mL kg^–1 2% lidocaine (n = 10); group LD_loc, lidocaine and 0.15 μg kg^–1 dexmedetomidine perineurally (n = 10); group LD_sys, lidocaine and 0.3 μg kg^–1 dexmedetomidine IM (n = 10). After anaesthesia, sensory blockade was evaluated by response to forceps pinch on skin innervated by the saphenous/femoral, common fibular and tibial nerves. Motor blockade was evaluated by observing the ability to walk and proprioception. Analgesia was monitored with Short Form of Glasgow Composite Pain Scale for up to 4 hours after extubation. Methadone IM was administered as rescue analgesia. Data were analysed by linear mixed effect models and Kaplan-Meier test (p < 0.05).ResultsMedian duration of the sensory blockade for all nerves was longer (p < 0.001) for group LD_loc than for groups L and LD_sys and was longer (p = 0.0011) for group LD_sys than for group L. Proprioception returned later (p < 0.001) for group LD_loc [285 (221–328) minutes] compared with group L [160 (134–179) minutes] or LD_sys [195 (162–257) minutes]. Return of the ability to walk was similar among all groups. Dogs in group LD_loc required postoperative rescue analgesia later (p = 0.001) than dogs in groups LD_sys and L.Conclusions and clinical relevanceDexmedetomidine administered perineurally with lidocaine prolonged sensory blockade and analgesia during the immediate postoperative period. Systemic dexmedetomidine also prolonged the sensory blockade of perineural lidocaine.     

Three‐dimensional conformal radiation therapy alone or in combination with surgery for treatment of canine intracranial meningiomas

Treatment protocols, treatment planning methods and tumour types in studies evaluating radiotherapy for canine brain tumours have been varied. This case series retrospectively evaluated the outcome of definitive, three‐dimensional conformal radiation therapy (3D‐CRT) as either a sole modality or as an adjuvant to surgery in 31 dogs diagnosed with meningioma by histopathology (n = 10) or cross‐sectional imaging of the head (n = 21, assessed independently by two board certified radiologists). Prescribed dose ranged from 45 to 54 Gy in 2.5 to 3 Gy fractions. Median overall survival was 577 days (interquartile range = 272–829 days; range = 30–1942 days) when all deaths were considered and 906 days (interquartile range = 336–912 days; range = 101–1942 days) when only dogs dying due to meningioma were considered. No significant difference in survival time was detected for the defined clinical or imaging findings or between treatment with radiotherapy alone versus adjuvant radiotherapy, suggesting that 3D‐CRT may be a viable alternative to surgery.