Arterial blood gas measurements are different for brachycephalic and nonbrachycephalic dogs acclimatized to an altitude of 1,535 meters.

OBJECTIVE: To define reference intervals (RIs) for arterial blood gas (aBG) measurements in healthy, nonsedated, dolichocephalic, and mesocephalic (nonbrachycephalic) dogs at approximately 1,535 m above sea level and compare these findings with healthy, nonsedated, brachycephalic dogs living at the same altitude. ANIMALS: 120 adult nonbrachycephalic dogs and 20 adult brachycephalic dogs. METHODS: Cases were prospectively enrolled from October 2021 to June 2022. Dogs were enrolled from the community or after presentation for wellness examinations or minor injuries including lacerations, nail injuries, and lameness. Physical examinations and systolic blood pressure (sBP) measurements were obtained before blood sample collection. Arterial blood was collected from the dorsal pedal artery or femoral artery. After data collection, brachycephalic dogs underwent pre- and postexercise tolerance assessments. RESULTS: The mean and RI values for arterial pH (7.442; 7.375 to 7.515), partial pressure of oxygen in arterial blood (Pao2; 78.3; 59.2 to 92.7 mm Hg), partial pressure of carbon dioxide in arterial blood (Paco2; 28.0; 21.5 to 34.4 mm Hg), saturation of arterial oxygen (Sao2; 98.4; 84.3% to 101.4%), HCO3 (18.9; 14.9 to 22.4 mmol/L), concentration of total hemoglobin (ctHb; 17.5; 13.4 to 21.1 g/dL), and sBP (133; 94 to 180 mm Hg) were established for healthy nonbrachycephalic dogs at 1,535-m altitude. All aBG measurements were statistically and clinically different from those previously reported for dogs at sea level. Brachycephalic dogs had significantly lower Pao2 and Sao2 (P = .0150 and P = .0237, respectively) and significantly higher ctHb (P = .0396) compared to nonbrachycephalic dogs acclimatized to the same altitude; the nonbrachycephalic RIs were not transferable to the brachycephalic dogs for Pao2. CLINICAL RELEVANCE: This study represents the first collation of aBG measurements for healthy nonbrachycephalic dogs acclimatized to an altitude of 1,535 m. Additionally, this study identified differences in arterial oxygenation measurements between brachycephalic and nonbrachycephalic dogs. RIs in brachycephalic dogs need to be established.

Investigation of the association between oxygen reserve index and arterial partial oxygen pressure in anesthetized dogs.

OBJECTIVE: To evaluate the relationship between oxygen reserve index (ORI) and arterial partial pressure of oxygen (PaO2) in anesthetized dogs. STUDY DESIGN: Prospective experimental study. ANIMALS: A total of eight healthy adult Beagle dogs with a median age of 38 (range 20-87) months and a median body mass of 8.6 (range 7.0-13.8) kg. METHODS: After induction of general anesthesia with propofol, dogs were mechanically ventilated and anesthesia maintained with isoflurane carried in oxygen. Arterial blood samples were collected from a catheter placed in the femoral artery. ORI was measured by placing a CO-oximeter sensor on the tongue. Inspired oxygen fraction (FiO2) was increased from 21% to > 95% in increments of 5%. PaO2 and ORI were recorded and compared at different times. The relationship between ORI and PaO2 was investigated using a nonlinear function, the Hill equation, and a linear regression analysis was performed, as appropriate. RESULTS: A total of 128 pairs of values were compared for all dogs. Applying the Hill equation to the relationship between ORI and PaO2 resulted in R2 = 0.80 (p < 0.001) with a Hill coefficient of 3.7. It was predicted that ORI ranged 0.1-0.9 as PaO2 ranged 127.0-417.9 mmHg and that in the more linear portion of the range, PaO2 of 127.0-289.9 mmHg ORI ranged 0.1-0.7. Linear regression analysis in the more linear portion showed a weak correlation (R2 = 0.29, p = 0.006). CONCLUSIONS AND CLINICAL RELEVANCE: In the present study, the Hill equation predicted the relationship between PaO2 and ORI for PaO2 ranging 127.0-417.9 mmHg in anesthetized dogs. However, in the linear portion of the PaO2, the coefficient of determination was low, indicating that ORI is not a surrogate for PaO2.

Non-invasive assessment of oxygenation status using the oxygen reserve index in dogs.

BACKGROUND: The oxygen reserve index (ORi) is a real-time, continuous index measured with multi-wavelength pulse CO-oximetry technology. It estimates mild hyperoxemia in humans, which is defined as a partial pressure of oxygen (PaO2) level between 100 and 200 mmHg. The objectives of this study were to assess the correlation between ORi and PaO2, as well as to determine its ability in detecting mild hyperoxemia in dogs. METHODS: This prospective observational study enrolled 37 anaesthetised and mechanically ventilated dogs undergoing elective procedures. Simultaneous measurements of ORi and PaO2 were collected, using a multi-wavelength pulse CO-oximeter with a probe placed on the dog's tongue, and a blood gas analyser, respectively. A mixed-effects model was used to calculate the correlation (r2) between simultaneous measurements of ORi and PaO2. The trending ability of ORi to identify dependable and proportional changes of PaO2 was determined. The diagnostic performances of ORi to detect PaO2 ≥ 150 mmHg and ≥ 190 mmHg were estimated using the area under the receiver operating characteristic curve (AUROC). The effects of perfusion index (PI), haemoglobin (Hb), arterial blood pH and partial pressure of carbon dioxide (PaCO2) on AUROC for PaO2 ≥ 150 mmHg were evaluated. RESULTS: A total of 101 paired measurements of ORi and PaO2 were collected. PaO2 values ranged from 74 to 258 mmHg. A strong positive correlation (r2 = 0.52, p < 0.001) was found between ORi and PaO2. The trending ability ORi was 90.7%, with 92% sensitivity and 89% specificity in detecting decreasing PaO2. An ORi value ≥ 0.53 and ≥ 0.76 indicated a PaO2 ≥ 150 and ≥ 190 mmHg, respectively, with ≥ 82% sensitivity, ≥ 77% specificity and AUROC ≥ 0.75. The AUROC of ORi was not affected by PI, Hb, pH and PaCO2. CONCLUSIONS: In anaesthetised dogs, ORi may detect mild hyperoxaemia, although it does not replace blood gas analysis for measuring the arterial partial pressure of oxygen. ORi monitoring could be used to non-invasively assess oxygenation in dogs receiving supplemental oxygen, limiting excessive hyperoxia.

Agreement between hematocrit values determined by the Cobas b121 blood gas analyzer and the microhematocrit method in dogs, cats, and horses.

BACKGROUND: Packed cell volume (PCV) is important for assessing a patient's health status. Some blood gas analyzers measure hematocrit, and the agreement with PCV varies among different analyzers. OBJECTIVES: We aimed to determine the agreement between PCV measured by microcentrifugation and hematocrit measured by the Cobas b121 blood gas analyzer in dogs, cats, and horses. METHODS: Whole blood samples for PCV and blood gas analysis were collected in lithium-heparin syringes and analyzed within 10 min of collection. Agreement and association between the PCV and Cobas b121 generated hematocrit were assessed by the Bland-Altman method, Pearson's correlation, Deming regression analysis, and paired t tests. A total allowable error of 10% was used for the analysis. RESULTS: This study included 45 dogs, 45 cats, and 33 horses. The respective mean ± SD (minimum-maximum) of PCVs and hematocrits were: dogs, 34.9 ± 9.9% (9.0-55.0) and 32.5 ± 8.8% (10.4-50.6); cats, 29.0 ± 9.6% (11.0-51.0) and 26.9 ± 9.3% (10.2-50.9); horses, 34.2 ± 6.5% (24.0-47.0) and 34.1 ± 6.0% (22.5-46.1). There were no significant differences between the methods. The bias ± SD was: dogs, -2.4 ± 2.6%; cats, -2.2 ± 2.3%; horses, -0.1 ± 2.4%. Pearson's correlation coefficients were > 0.90 for all species (P < 0.0001). In 60%, 49%, and 85% of the samples for dogs, cats, and horses, respectively, the percentage differences between the methods were within 10%. CONCLUSIONS: The Cobas b121 blood gas analyzer provided accurate estimates of PCVs in horses. However, in dogs and cats, there was a large frequency of unacceptable differences between the methods.

Evaluation and establishment of reference intervals using the i-STAT1 blood chemistry analyzer in turkeys.

In veterinary medicine, point-of-care testing techniques have become popular, since they provide immediate results and only small amounts of blood are needed. The handheld i-STAT1 blood analyzer is used by poultry researchers and veterinarians; however, no studies have evaluated the accuracy of this analyzer determined reference intervals in turkey blood. The objectives of this study were to 1) investigate the effect of storage time on turkey blood analytes, 2) compare the results obtained by the i-STAT1 analyzer to those obtained by the GEM Premier 3000, a conventional laboratory analyzer, and 3) establish reference intervals for blood gases and chemistry analytes in growing turkeys using the i-Stat. For the first and second objectives, we used the CG8+ i-STAT1 cartridges to test blood from 30 healthy turkeys in triplicate and once with the conventional analyzer. To establish the reference intervals, we tested a total 330 blood samples from healthy turkeys from 6 independent flocks during a 3-yr period. Blood samples were then divided into brooder (<1 wk) and growing (1-12 wk of age). Friedman's test demonstrated significant time-dependent changes in blood gas analytes, but not for electrolytes. Bland-Altman analysis revealed that there was agreement between the i-STAT1 and the GEM Premier 300 for most of the analytes. However, Passing-Bablok regression analysis identified constant and proportional biases in the measurement of multiple analytes. Tukey's test revealed significant differences in the whole blood analytes between the means of brooding and growing birds. The data presented in the present study provide a basis for measuring and interpreting blood analytes in the brooding and growing stages of the turkey lifecycle, offering a new approach to health monitoring in growing turkeys.

Cephalic and saphenous venous blood collected by continuous heating of the paws compared with arterial blood for measurement of blood gas values in well-perfused dogs.

BACKGROUND: "Arterialization" of the dorsal hand vein is well-established in human medicine, but not in veterinary medicine. OBJECTIVES: To compare cephalic and saphenous venous blood collected by continuously heating the paws to 37°C ("arterialization"), with arterial blood (AB) for measurement of blood gas variables in well-perfused dogs. ANIMALS: Eight healthy dogs. METHODS: Experimental study. Fore and hind paws were continuously heated to 37°C to "arterialize" cephalic and saphenous venous blood. AB and "arterialized" cephalic and saphenous venous blood (ACV and ASV, respectively) were simultaneously collected from lightly anesthetized dogs with induced metabolic and respiratory acid-base disorders. The pH, partial pressures of carbon dioxide (PCO2 ) and oxygen (PO2 ), bicarbonate concentration [HCO3 - ], and base excess (BE) were measured once in each state. Systolic blood pressure was maintained above 100 mm Hg. The AB, ACV, and ASV values were compared. RESULTS: The pH, [HCO3 - ], and BE values had no significant difference and good agreement, the PCO2 values had a strong correlation (correlation coefficient of .91-1.00), and the PO2 values had a significant difference (P < .01) and poor agreement between AB and ACV, and between AB and ASV. The PCO2 values of ASV overestimated those of AB by ~3.0 mm Hg, which was considered within clinically allowable limits, while those of ACV were not within clinically allowable limits. CONCLUSIONS AND CLINICAL IMPORTANCE: Under experimental conditions, the ASV samples were more identical to the AB samples than the ACV samples for pH, PCO2 , [HCO3 - ], and BE values in well-perfused dogs. The saphenous vein is suitable for "arterialization."

Evaluation of Nasal Oxygen Administration at Various Flow Rates and Concentrations in Conscious, Standing Adult Horses.

This study evaluated the effects of various flow rates and fractions of oxygen on arterial blood gas parameters and on the fraction of inspired oxygen (FIO2) delivered to the distal trachea. Oxygen was administered to 6 healthy, conscious, standing, adult horses via single nasal cannula positioned within the nasopharynx. Three flow rates (5, 15, 30 L/min) and fractions of oxygen (21, 50, 100%) were delivered for 15 minutes, each in a randomized order. FIO2 was measured at the level of the nares and distal trachea. Adverse reactions were not observed with any flow rate. FIO2 (nares and trachea) and PaO2 increased with increasing flow rate and fraction of oxygen (P < .0001). FIO2 (trachea) was significantly less than FIO2 (nares) at 50% and 100% oxygen at all flow rates (P < .0001). Differences in PaO2 were not observed between 100% oxygen-5L/min and 50% oxygen-15L/min and or between 100% oxygen-15L/min and 50% oxygen-30L/min. Tracheal FIO2 for 100% oxygen-15L/min was increased compared to 50% oxygen-30L/min (P < .0001). Respiratory rate, ETCO2, PaCO2, and pH did not differ between treatments. Administration of 50% oxygen via nasal cannula at 15 and 30 L/min effectively increased in PaO2 and was well tolerated in conscious, standing, healthy horses. While these results can be used guide therapy in hypoxemic horses, evaluation of the administration of 50% oxygen to horses with respiratory disease is warranted.

A randomized controlled trial investigating the effect of transport duration and age at transport on surplus dairy calves: Part II. Impact on hematological variables.

Surplus dairy calves often arrive at veal and dairy-beef rearing facilities with health and blood metabolite level abnormalities, which can affect their welfare and performance, predisposing them to future health challenges. The objective of this randomized controlled trial was to investigate the effects of transport duration and age at the time of transport on blood parameters in surplus dairy calves following 6, 12, or 16 h of continuous road transportation. All surplus calves from 5 commercial dairy farms in Ontario were enrolled and examined daily before transport (n = 175). On the day of transportation, calves were weighed, blood sampled, and randomly assigned to 6, 12, or 16 h of transportation. Blood samples were then collected immediately after transportation, as well as 24, 48, and 72 h thereafter. Serum was analyzed at a provincial diagnostic laboratory for nonesterified fatty acids (NEFA), ß-hydroxybutyric acid (BHBA), creatine kinase (CK), cholesterol, and haptoglobin. In addition, blood gas and electrolyte values were also assessed at the time of sample collection. Mixed models with repeated measures were used to assess the effects of transport duration, breed, sex, transfer of passive immunity status, weight before transportation, and age at transportation on blood parameters. Immediately following transportation, NEFA and BHBA were greater for calves transported for 12 h (Δ = 0.22 mmol/L NEFA, 95% CI = 0.15 to 0.30; Δ = 0.04 mmol/L BHBA, 95% CI = 0.02 to 0.06) and 16 h (Δ = 0.35 mmol/L NEFA, 95% CI = 0.27 to 0.42; Δ = 0.10 mmol/L BHBA, 95% CI = 0.08 to 0.11) compared with calves transported for 6 h. Glucose was lower immediately following transportation in calves transported for 16 h compared with 6 h (Δ = -15.54 mg/dL, 95% CI = -21.54 to -9.54). In addition, pH and HCO3- were lower in calves transported for 12 (Δ = -0.09 pH, 95% CI = -0.13 to -0.05; Δ = -1.59 mmol/L HCO3-, 95% CI = -2.61 to -0.56) and 16 h (Δ = -0.07 pH, 95% CI = -0.12 to -0.03; Δ = -1.95 mmol/L HCO3-, 95% CI = -2.95 to -0.95) compared with calves transported for 6 h. Calves transported between 15 and 19 d of age had a higher concentration of cholesterol and CK (Δ = 0.27 mmol/L cholesterol; 37.18 U/L CK) compared with 2- to 6-d-old calves, and calves 12 to 14 d old had greater reduction in HCO3- (Δ = -0.92 mmol/L) compared with 2- to 6-d-old calves. These findings show that transporting calves for long distances results in lower glucose concentration and suboptimal energy status, and that this effect varies based on the calf's age.

Acid-Base.

In clinical medicine, evaluation of acid-base balance can be a valuable diagnostic and monitoring tool. Blood gas machines need very small volumes of blood and provide immediate results, making them ideal for use in the emergency room and intensive care setting. This review outlines the stepwise approach to assessment of acid-base balance in dogs, common causes of acid-base abnormalities, and the general approach to treatment.

Point-of-Care Instruments.

Point-of-care testing, or testing done near the patient, allows for rapid results that can theoretically improve patient care and client satisfaction. The value of these results relies on high-quality laboratory practices, including an understanding of the technology by users. Herein is a brief review of point-of-care testing for biochemistry, hematology, coagulation, blood gas analysis, glucometers, and urinalysis, along with available technology with a focus on what information these analyzers can and cannot provide.

Effects of time delay and blood storage methods on analysis of canine venous blood samples with an Element point-of-care analyzer.

BACKGROUND: Manufacturers of point-of-care (POC) analyzers recommend immediate processing and anaerobic collection of blood samples. However, it is not uncommon for clinical scenarios to result in delayed sample processing or room air exposure that could impact the test results. OBJECTIVE: To investigate the effect of time delay and sample storage method on key POC analytes in canine venous blood samples processed with an Element POC analyzer. METHODS: Blood gas analysis was performed on venous blood samples at times 0 (T0), 15, 30, and 60 minutes after sampling using three different storage methods: preheparinized plastic syringes and two different lithium heparin tubes. To determine clinical relevance, results were compared with allowable total error of the respective parameter. Significance was set at P < 0.05. RESULTS: Significant differences between the three storage methods at baseline were found for partial pressure of carbon dioxide (PCO2 ), partial pressure of oxygen (PO2 ), base excess, and total hemoglobin. No significant differences up to T60 were found within collection methods for actual bicarbonate (HCO3 - ), base excess, sodium, potassium, chloride, ionized calcium (iCa), glucose, and BUN. Significant differences within collection methods were found after T0 for creatinine, after 15 minutes for lactate, and after 30 minutes for pH and hematocrit. No significant differences were found for PO2 in samples stored in preheparinized plastic syringes at any time point. CONCLUSIONS: These results suggest that HCO3 - , sodium, potassium, chloride, iCa, glucose, and BUN are comparable within the three storage methods for up to 60 minutes after sampling without resulting in clinically relevant changes.

Does postprandial lipemia interfere with blood gas analysis and assessment of acid-base status in dogs?

To evaluate the interference of postprandial lipemia on blood gas parameters and to assess the acid-base status by the quantitative approach of the strong ion model blood samples of 15 healthy dogs were collected during fasting (0 h) and at one (1 h), three (3 h) and five (5 h) hours after the induction of lipemia with a hypercaloric diet. Total cholesterol (TC) and triglyceride (TG) levels were used to assess lipemia and these were correlated with the parameters evaluated accordingly. Anion gap decreased at 5 h without correlation with TC and TG, whereas other parameters measured by the blood gasometer did not change. In the evaluation of the acid base state, the apparent strong ion difference (SIDa) and the strong ion gap (SIG) showed a decrease at 5 h without correlation with lipemia. Lipid levels correlated with the effective strong ion difference (SIDe), the concentration of total non-volatile weak acids (Atot), albumin, phosphate, and magnesium. The SIDe increased at 1 h and at 3 h; the Atot at 1 h, 3 h, and 5 h; albumin increased at 1 h and 3 h; phosphate increased at 1 h, 3 h and 5 h; and magnesium decreased at 5 h. Though postprandial lipemia does not interfere with blood gas analysis, it can cause errors in the variables used to assess the acid-base status, which are dependent on biochemical analytes. Therefore, caution is required when interpreting electrolyte disturbances that result from the postprandial state.

Preliminary study evaluating the assessment of changes in pulmonary function associated with body positioning in dogs with suspected aspiration pneumonia.

OBJECTIVE: To evaluate the variability in arterial blood gas (ABG) assessment of pulmonary function with different body positioning in dogs with suspected aspiration pneumonia. KEY FINDINGS: The median differences in alveolar-arterial gradient, Pao2 , and Paco2 values in different recumbencies were not statistically significantly different, both within patients and across the study population. No difference was noted in ABG values in the subgroups with unilateral or bilateral disease or that were more affected on the right side versus the left side. SIGNIFICANCE: This preliminary study provides data that can be used to calculate appropriate sample sizes for subsequent studies investigating the impact of recumbency on pulmonary function in patients with aspiration pneumonia.

Preliminary evaluation of the effects of a 1:1 inspiratory-to-expiratory ratio in anesthetized and ventilated horses.

OBJECTIVE: To describe some cardiorespiratory effects of an inspiratory-to-expiratory (IE) ratio of 1:1 compared with 1:3 in ventilated horses in dorsal recumbency. STUDY DESIGN: Randomized crossover experimental study. ANIMALS: A total of eight anesthetized horses, with 444 (330-485) kg body weight [median (range)]. METHODS: Horses were ventilated in dorsal recumbency with a tidal volume of 15 mL kg-1 and a respiratory rate of 8 breaths minute-1, and IE ratios of 1:1 (IE1:1) and 1:3 (IE1:3) in random order, each for 25 minutes after applying a recruitment maneuver. Spirometry, arterial blood gases and dobutamine requirements were recorded in all horses during each treatment. Electrical impedance tomography (EIT) data were recorded in four horses and used to generate functional EIT variables including regional ventilation delay index (RVD), a measure of speed of lung inflation, and end-expiratory lung impedance (EELI), an indicator of functional residual capacity (FRC). Results were assessed with linear and generalized linear mixed models. RESULTS: Compared with treatment IE1:3, horses ventilated with treatment IE1:1 had higher mean airway pressures and respiratory system compliance (p < 0.014), while peak, end-inspiratory and driving airway pressures were lower (p < 0.001). No differences in arterial oxygenation or dobutamine requirements were observed. PaCO2 was lower in treatment IE1:1 (p = 0.039). Treatment IE1:1 resulted in lower RVD (p < 0.002) and higher EELI (p = 0.023) than treatment IE1:3. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggest that IE1:1 improved respiratory system mechanics and alveolar ventilation compared with IE1:3, whereas oxygenation and dobutamine requirements were unchanged, although differences were small. In the four horses where EIT was evaluated, IE1:1 led to a faster inflation rate of the lung, possibly the result of increased FRC. The clinical relevance of these findings needs to be further investigated.

Comparison of the bovine blood gas parameters produced with three types of portable blood gas analyzers.

BACKGROUND: A definite diagnosis should be made in the bovine practice field, however, it was difficult to perform laboratory analysis immediately. Currently, three types of portable blood gas analyzers are available in Korea. OBJECTIVES: This study aimed to evaluate the correlations among these three analyzers. METHODS: Seventy-two plasma samples from Holstein-Friesian cows were used for blood gas analysis, and three instruments (EDAN i15 Vet, VETSCAN i-STAT, and EPOC) were operated simultaneously. Moreover, plasma calcium levels were compared between these portable analyzers and blood chemistry device, which is usually used in a laboratory environment. Pearson analysis was performed to confirm the correlation of each parameter produced with the three instruments and blood chemistry analyzer. RESULTS: As results, high correlation was observed in parameters of pH, pO2, potassium ion, ionized calcium, and glucose (p < 0.001, r > 0.7). In addition, pCO2 showed a moderate correlation among the three analyzers (p < 0.001, r > 0.5), and there was no correlation among all instruments for sodium ions. There was also a high correlation between ionized calcium from the three portable devices and total calcium from the biochemistry analyzer (p < 0.001, r > 0.9). CONCLUSIONS: In conclusion, there was a high correlation between results from the three different blood gas analyzers used in the bovine clinical field in Korea. Thus, a consistent diagnosis can be made even with different equipment if the operator is aware of the strengths and weaknesses of each piece of equipment and operates it properly.

Sources of error in acid-base analysis from a blood gas analyser result: a narrative review.

Preservation of blood pH within a narrow range is essential to optimal physiological function. This narrow pH range is maintained via the interactions of various buffer systems. Blood gas analysis is thus essential in the diagnosis and management of disorders affecting blood pH. Common methods of acid-base interpretation in veterinary science are the traditional approach, the physicochemical approach and the semiquantitative approach. However, blood gas analysis is prone to error during the preanalytical, analytical and post-analytical phases of the laboratory process. The pre-analytical phase incorporates steps in obtaining the sample, thus sources of pre-analytical error are related to operator technique. Most errors occur during the pre-analytical phase. Pre-analytical errors include entrainment of air bubbles into the sample and delays between sampling and analysis, both of which cause inaccurate measurement of oxygen and carbon dioxide tensions. The analytical phase outlines processes within the analyser. Common analytical errors are related to substances confounding analyte measurements. The post-analytical phase mainly describes interpretation of the results. Some of the approaches to acid-base interpretation require extensive post-analytical calculations, thus lending themselves to error. Errors occurring during the prior phases will be amplified. Errors in the measurement of the carbon dioxide tension (from which bicarbonate concentration and base excess are calculated) will introduce error into all three methods of acid-base interpretation. Furthermore, errors occurring in the measurements of electrolytes and lactate will result in incorrect interpretations if the physicochemical and semiquantitative approaches are applied. The potential sources of error during the various phases are reviewed.

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.

Intratracheal oxygen administration increases FIO2 and PaO2 compared with intranasal administration in healthy, standing horses.

OBJECTIVE: To evaluate the efficacy of 2 different oxygen delivery strategies-intranasal and tracheal insufflation-on the inspired fraction of oxygen (FIO2) in standing horses and to determine the time needed for arterial oxygen partial pressure (PaO2) equilibration. ANIMALS: 6 healthy adult horses. PROCEDURES: In this blinded, randomized crossover design study, horses were randomly assigned to receive oxygen via nasal cannula (group N) or transcutaneous tracheal catheter (group T). After placement of venous and arterial catheters, FIO2 was measured through a catheter placed into the distal portion of the trachea. After baseline measurements were obtained, horses received oxygen at up to 25 mL/kg/min for 1 hour via either intranasal or intratracheal catheter. The FIO2 and PaO2 were recorded at 5, 10, 15, 20, 25, 30, 45, and 60 minutes during and 5, 10, 15, 20, and 30 minutes after oxygen insufflation. Data were analyzed by use of a 2-way repeated measures ANOVA with Tukey-Kramer post hoc testing for pairwise comparisons (P < 0.05). RESULTS: During oxygen administration, FIO2 and PaO2 increased significantly when compared with baseline, resulting in significantly higher values for group T (37.7 ± 2.4%; 214.6 ± 18 mm Hg) than for group N (34.3 ± 3.9%; 184.1 ± 11 mm Hg). The equilibration time was less than 10 minutes. CLINICAL RELEVANCE: Intratracheal oxygen administration resulted in better oxygenation than nasal insufflation and should therefore be considered in standing horses that are experiencing severe respiratory compromise. The equilibration between FIO2 and PaO2 is rapid in adult horses.

Effects of intraoperative positive end-expiratory pressure and fraction of inspired oxygen on postoperative oxygenation in dogs undergoing stifle surgery.

OBJECTIVE: To compare the effects of fraction of inspired oxygen (FiO2) with the addition of positive end-expiratory pressure (PEEP) during anesthesia on arterial oxygenation in the first 4 postoperative hours in dogs. We hypothesized that compared with dogs breathing FiO2 ≥ 0.95 and no PEEP (ZEEP), the use of intraoperative PEEP would improve postoperative oxygenation, and that the use of PEEP combined with an FiO2 of 0.4 would further improve it. STUDY DESIGN: Prospective, randomized study. ANIMALS: A total of 30 dogs undergoing unilateral stifle surgery. METHODS: Using a standardized anesthetic protocol, dogs were assigned to either FiO2 ≥ 0.95 and ZEEP, FiO2 ≥ 0.95 and 5 cmH2O PEEP or FiO2 0.4 and 5 cmH2O PEEP. All dogs were mechanically ventilated with a tidal volume of 12 mL kg-1. Dogs breathed room air after recovery from anesthesia. Arterial blood gases were measured during surgical closure and 10, 120 and 240 minutes after extubation. Demographic characteristics were compared with Kruskal-Wallis tests. The effects of treatment and time on the PaO2, PaCO2, PaO2:FiO2 and shunt fraction (F-shunt) were assessed with mixed-effect models. RESULTS: The PaO2 and F-shunt were lower during anesthesia for dogs breathing FiO2 0.4. No differences among groups were measured after extubation for any variable. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with dogs ventilated with FiO2 ≥ 0.95 and ZEEP, application of 5 cmH2O PEEP did not improve intraoperative gas exchange. The combination of 5 cmH2O PEEP and FiO2 0.4 resulted in lower intraoperative F-shunt values. However, no benefits from those maneuvers on postoperative PaO2 and F-shunt were recorded after extubation, suggesting that alterations in pulmonary function imposed by anesthesia were reversed soon after extubation.

Comparison of point-of-care NOVA CCX blood gas analyzer to laboratory analyzer in a population of healthy adult cats.

OBJECTIVE: To compare the level of agreement of measurement of analytes (sodium, chloride, potassium, urea nitrogen [UN], creatinine, glucose) in a population of healthy adult cats between the point-of-care (POC) analyzer and laboratory analyzer. To establish reference intervals for the POC analyzer in healthy adult cats. DESIGN: Prospective observational study. SETTING: University teaching hospital. ANIMALS: Fifty-five cats were screened. Seven cats were excluded due to aggression that prohibited phlebotomy, and 1 cat was excluded due to prolonged restraint; 47 cats were enrolled. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In this patient population, reference intervals for the POC analyzer were calculated: sodium 145-157 mmol/L; chloride 116-124 mmol/L; potassium 3.4-5.5 mmol/L; UN 5.71-13.9 mmol/L (16-39 mg/dl); creatinine 74.3-189.2 mmol/L (0.84-2.14 mg/dl); and glucose 4-11.8 mmol/L (72-213 mg/dl). Comparison between the POC analyzer and laboratory analyzer using the Bland-Altman method was performed. The bias for each analyte is as follows: sodium 1.55 mmol/L; chloride 0.99 mmol/L; potassium 0.21 mmol/L; UN -0.25 mmol/L (-0.7 mg/dl); creatinine 9.73 mmol/L (0.11 mg/dl); and glucose 0.5 mmol/L (9.79 mg/dl). CONCLUSIONS: Reference intervals for each analyte were similar to other chemistry analyzers. There was no significant difference between the POC and laboratory analyzers in analysis of UN, with a statistically significant difference observed with sodium, potassium, chloride, creatinine, and glucose. However, the values are likely not sufficiently different to alter initial clinical decisions regarding patient care.