Agreement between arterial and central venous blood pH and its contributing variables in anaesthetized dogs with respiratory acidosis.

OBJECTIVE: To determine the accuracy of variables that influence blood pH, obtained from central venous (jugular vein) blood samples compared with arterial (dorsal pedal artery) samples in anaesthetized dogs with respiratory acidosis. STUDY DESIGN: Prospective, comparative, observational study. ANIMALS: A group of 15 adult male dogs of various breeds weighing 17 (11-42) kg [median (range)]. METHODS: Dogs were premedicated with buprenorphine (0.03 mg kg-1) and medetomidine (0.01 mg kg-1) administered intramuscularly by separate injections, anaesthetized with propofol intravenously to effect and maintained with isoflurane in 50% air-oxygen. Arterial and central venous catheters were placed. After 15 minutes of spontaneous breathing, arterial and central venous blood samples were obtained and analysed within 5 minutes, using a bench-top gas analyser. Differences between arterial and central venous pH and measured variables were assessed using Wilcoxon rank sum test and effect size (r: matched-pairs rank-biserial correlation) was calculated for each comparison. The agreement (bias and limits of agreement: LoAs) between arterial and central venous pH and measured variables were assessed using Bland-Altman; p < 0.05. Data are reported as median and 95% confidence interval. RESULTS: Arterial blood pH was 7.23 (7.19-7.25), and it was significantly greater than central venous samples 7.21 (7.18-7.22; r = 0.41). Agreement between arterial and venous pH was acceptable with a bias of 0.01 (0.002-0.02) and narrow LoAs. PCO2 [arterial 54 (53-58) mmHg, 7.2 (7.1-7.7) kPa; venous 57 (54-62) mmHg, 7.6 (7.2-8.3) kPa], bicarbonate ion concentration and base excess did not differ between samples; however, agreement between arterial and venous PCO2 was not acceptable with a bias of -2 (-5 to 0) mmHg and wide LoAs. CONCLUSIONS AND CLINICAL RELEVANCE: Blood pH measured from central venous (jugular vein) blood is an acceptable clinical alternative to arterial blood (dorsal pedal artery) in normovolaemic anaesthetized dogs with respiratory acidosis.

Comparative effects of three different ventilatory treatments on arterial blood gas values and oxygen extraction in healthy anaesthetized dogs.

OBJECTIVE: To compare the effect of invasive continuous positive airway pressure (CPAP), pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) and spontaneous breathing (SB) on PaO2, PaCO2 and arterial to central venous oxygen content difference (CaO2-CcvO2) in healthy anaesthetized dogs. STUDY DESIGN: Prospective randomized crossover study. ANIMALS: A group of 15 adult male dogs undergoing elective orchidectomy. METHODS: Dogs were anaesthetized [buprenorphine, medetomidine, propofol and isoflurane in an air oxygen (FiO2= 0.5)]. All ventilatory treatments (CPAP: 4 cmH2O; PCV: 10 cmH2O driving pressure; PEEP, 4 cmH2O; respiratory rate of 10 breaths minute-1 and inspiratory-to-expiratory ratio of 1:2; SB: no pressure applied) were applied in a randomized order during the same anaesthetic. Arterial and central venous blood samples were collected immediately before the start and at 20 minutes after each treatment. Data were compared using a general linear mixed model (p < 0.05). RESULTS: Median PaO2 was significantly higher after PCV [222 mmHg (29.6 kPa)] than after CPAP [202 mmHg (26.9 kPa)] and SB [208 mmHg (27.7 kPa)] (p < 0.001). Median PaCO2 was lower after PCV [48 mmHg (6.4 kPa)] than after CPAP [58 mmHg (7.7 kPa)] and SB [56 mmHg (7.5 kPa)] (p < 0.001). Median CaO2-CcvO2 was greater after PCV (4.36 mL dL-1) than after CPAP (3.41 mL dL-1) and SB (3.23 mL dL-1) (p < 0.001). PaO2, PaCO2 and CaO2-CcvO2 were no different between CPAP and SB (p > 0.99, p = 0.697 and p = 0.922, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: CPAP resulted in similar arterial oxygenation, CO2 elimination and tissue oxygen extraction to SB. PCV resulted in improved arterial oxygenation and CO2 elimination. Greater oxygen extraction occurred with PCV than with CPAP and SB, offsetting its advantage of improved arterial oxygenation. The benefit of invasive CPAP over SB in the healthy anaesthetized dog remains uncertain.

Comparison of canine urine specific gravity measurements between various refractometers in a clinical setting.

BACKGROUND: Veterinary facilities might use multiple refractometers and individuals to measure urine specific gravity (USG). Previous comparison studies show conflicting results. Furthermore, the clinical significance of measurement differences and interobserver variabilities has not been assessed. OBJECTIVES: We aimed to determine statistically and clinically significant differences between four refractometers in measuring canine USG and subsequent categorization of urine concentrations and azotemia and determine the variability between different observers performing USG measurements. METHODS: Fifty-nine specimens were included for the USG measurements with four refractometers by different observers. Each refractometer pair was compared using Spearman's rank correlation, Bland-Altman difference plots, and Deming regression analyses. Calculated bias was compared to set performance goals. Interobserver agreement was evaluated, and intraclass correlation coefficients were used to determine differences in the categorization of urine concentrations and azotemia (prerenal or renal). RESULTS: There was excellent correlation (rs  = .99-1.00) between refractometers. All comparisons involving R4 showed significant constant and proportional biases. Mean bias met the clinical performance goals for all refractometers, except for comparisons with R4, where up to 17 results were outside the allowable bias. There was almost perfect agreement (rs  = .999) between observers and excellent agreement (ICC = .96-.99) for the classification of urine concentrations. In azotemic patients (22%), there was perfect agreement (ICC = 1.00) for the categorization of azotemia. CONCLUSIONS: In most cases, three of the refractometers evaluated in this study can be used interchangeably at all USG values, without affecting clinical decision-making. Multiple observers did not significantly affect decision-making.

Blood acid-base, haematological and haemostatic effects of hydroxyethyl starch (130/0.4) compared to succinylated gelatin colloid infusions in normovolaemic dogs.

Synthetic colloids are commonly administered to dogs to treat absolute or relative hypovolaemia. Voluven® (tetrastarch 130/0.4) and Gelofusine® (succinylated gelatin) are available to veterinarians in South Africa. In humans, use of these products has caused acid-base derangements, changes in haematology and impaired haemostasis. We aimed to investigate these effects in healthy normovolaemic dogs. Eight healthy adult beagle dogs underwent a cross-over study, receiving Voluven® or Gelofusine® (10 mL/kg/h for 120 min) once each with a 14-day washout between treatments. Dogs were premedicated with dexmedetomidine (10 µg/kg intramuscularly). Anaesthesia was induced with propofol and the dogs were maintained with isoflurane-in-oxygen. The anaesthetised dogs were connected to a multi-parameter monitor to monitor physiological parameters throughout. Catheters placed in a jugular vein and dorsal metatarsal artery allowed sampling of venous and arterial blood. Blood was collected immediately prior to commencement of colloid infusion, after 60 min infusion and at the end of infusion (120 min) to allow for arterial blood gas analysis, haematology and coagulation testing (activated partial thromboplastin time [aPTT], prothrombin time [PT] and thromboelastography [TEG]). There was no effect, between treatments or over time, on blood pH. The haemoglobin concentration, erythrocyte count and haematocrit decreased significantly over time (all p 0.01), with no differences between treatments, and remained within normal clinical ranges. There were no differences between treatments or over time for the TEG, aPTT and PT tests of haemostasis. At the dose studied, Voluven® and Gelofusine® had comparably negligible effects on blood acid-base balance and coagulation in normovolaemic dogs.

Adenoviral hepatitis in two Nile crocodile (Crocodylus niloticus) hatchlings from South Africa.

Adenoviral infections may cause mild to severe morbidity or fatality in a large array of animal species. In crocodilians, hatchlings under 5 months of age are usually affected. However, there is a paucity of information on actual incidences in hatchlings originating from South Africa. Two cases of adenoviral hepatitis in crocodile hatchlings about 2 weeks old, bred on a commercial farm in South Africa, are described. Both hatchlings showed typical clinical signs of hepatitis. The identification of intranuclear inclusion bodies in the liver was used to differentiate between adenoviral hepatitis and chlamydial hepatitis. Although vertical transmission has never been proven in crocodiles, the young age of the affected hatchlings raises the possibility of vertical transmission. The lack of epidemiological information on adenoviral hepatitis in crocodiles highlights the need for further characterisation of the virus and targeted surveillance.