Assessment of the effect of dilution of blood samples with sodium heparin on blood gas, electrolyte, and lactate measurements in dogs

OBJECTIVE: To evaluate the effect of dilution of blood samples with sodium heparin on blood gas, electrolyte, and lactate measurements in dogs. Sample Population-Venous blood samples collected from 6 adult dogs of various breeds. PROCEDURE: Syringes were prepared with anticoagulant via 1 of 4 techniques, and the residual volume of liquid heparin in each type of prepared syringe was determined. Blood gas values and other selected clinicopathologic variables were measured in whole blood samples after collection (baseline) and after aliquots of the samples were diluted with heparin via 1 of the 4 manual syringe techniques. By use of a tonometer, whole blood samples were adjusted to 1 of 3 oxygen concentrations (40, 100, or 600 mm Hg) and the PO2 values were measured at baseline and subsequent to the 4 heparin dilutions. RESULTS: The 4 syringe techniques resulted in 3.9%, 9.4%, 18.8%, and 34.1% dilutions of a 1-mL blood sample. Compared with baseline values, dilution of blood samples with liquid heparin significantly changed the measured values of PCO2, PO2, and base deficit and concentrations of electrolytes and lactate. Of the variables assessed, measurement of ionized calcium concentration in blood was most affected by heparin dilution. CONCLUSIONS AND CLINICAL RELEVANCE: These findings in dogs indicate that dilution of blood samples with heparin can be a source of preanalytical error in blood gas, electrolyte, and lactate measurements. Limiting dilution of blood samples with heparin to < 4% by volume via an evacuation technique of syringe heparinization is recommended.     

Sensitivity,specificity, and predictive values of reagent test strip estimations of blood urea nitrogen

Azostix-reagent-tests(R) strips (Ames, Miles, Inc., Diagnostic Division, Elkhart, IN) were used to measure blood urea nitrogen values in blood samples from 125 dogs and cats at the North Carolina State University, College of Veterinary Medicine. Results of the tests were compared with standard serum urea nitrogen results. Sensitivity, specificity, and negative predictive values were high (86.4, 90.3, and 96.5%, respectively). Positive predictive value was low, 65.5% of the dogs and cats with elevated blood urea nitrogen values were correctly classified as abnormal The test performs well when the prevalence of abnormal values is near 50%.     

Sampling and storage of blood for pH and blood gas analysis.

Techniques used in sampling and storage of a blood sample for pH and gas measurements can have an important effect on the measured values. Observation of these techniques and principles will minimize in vitro alteration of the pH and blood gas values. To consider that a significant change has occurred in a pH or blood gas measurement from previous values, the change must exceed 0.015 for pH, 3 mm Hg for PCO2, 5 mm Hg for PO2, and 2 mEq/L for [HCO-3] or base excess/deficit. In vitro dilution of the blood sample with anticoagulant should be avoided because it will alter the measured PCO2 and base excess/deficit values. Arterial samples should be collected for meaningful pH and blood gas values. Central venous and free-flowing capillary blood can be used for screening procedures in normal patients but are subject to considerable error. A blood sample can be stored for up to 30 minutes at room temperature without significant change in acid-base values but only up to 12 minutes before significant changes occur in PO2. A blood sample can be stored for up to 3.5 hours in an ice-water bath without significant change in pH and for 6 hours without significant change in PCO2 or PO2. Variations of body temperatures from normal will cause a measurable change in pH and blood gas values when the blood is exposed to the normal water bath temperatures of the analyzer.     

Thiopurine methyltransferase in red blood cells of dogs, cats, and horses

Our objective was to determine if thiopurine methyltransferase (TPMT), the enzyme important in the metabolism of azathioprine in human beings, is detectable in red blood cell lysates (RBCL) of healthy dogs, cats, and horses. Values for TPMT activity were determined from blood collected from 20 healthy dogs, cats, and horses. The TPMT activity in each animal's RBCL was determined using a radioenzymatic end point involving TPMT-facilitated metabolism of 6-mercaptopurine to 6-methylmercaptopurine (6-MMP). One unit of TPMT activity represents the formation of 1 nmol of 6-MMP per milliliter of packed red blood cells per hour of incubation at 37 degrees C. TPMT activity in RBCL was detectable in all species, with mean RBC values +/- standard deviation of 17.9 +/- 3.79 U/mL in dogs; 2.76 +/- 0.70 U/mL in cats; and 2.185 +/- 0.36 U/mL in horses. Values for TPMT in the 3 species were significantly (P < .05) different from one another. TPMT values for dogs were significantly higher than the other species, and TPMT values for cats were significantly higher than those for horses. We conclude that RBCL TPMT values are measurable in dogs. cats, and horses and that dogs have higher values than cats or horses. These findings are consistent with the lower tolerance for azathioprine in cats as compared with dogs. It remains to be determined whether RBCL TPMT values in these species correlate with TPMT activity in the liver, where most of the metabolization of azathioprine is believed to occur.     

Calculation of bovine haemoglobin oxygen saturation by algorithms integrating age,haemoglobin content,blood pH,partial pressures of oxygen and carbon dioxide in the blood,and temperature

In human and veterinary medicine, arterial and venous haemoglobin oxygen saturations are often used to estimate the severity of a disease and to guide therapeutic decisions. In veterinary medicine, haemoglobin oxygen saturation (SO(2)) is usually calculated using a blood gas analyser and algorithms developed for humans. It is possible, therefore, that the values obtained in animals may be distorted, particularly in animals with a high haemoglobin oxygen affinity, like young calves. In order to verify this hypothesis, we compared the arterial (SaO(2)) and venous (SvO(2)) haemoglobin oxygen saturations calculated using three different algorithms, and the oxygen exchange fraction (OEF) at the tissue level, which is the degree of haemoglobin desaturation between arterial and venous blood (SaO(2)-SvO(2)), with the values obtained from the whole bovine oxygen equilibrium curve (OEC) determined by a reference method. The blood gas analysers underestimated SvO(2) values; consequently, the OEF was overestimated (by about 10%). Two methods of reducing these errors were assessed. As the haemoglobin oxygen affinity decreases during the first month of life in calves a relationship between PO(2) at 50% haemoglobin saturation (P50) and age was established in order to correct the calculated values of venous and arterial SO(2), taking into account the estimated position of the OEC. This method markedly reduced the error for SvO(2) and OEF. Secondly, the SO(2) was calculated using a mathematical model taking into account the age of the animal and the specific effects of pH, PCO(2), and temperature on the bovine OEC. Using this method, the mean difference between the OEF values calculated using the mathematical model and those calculated by the reference method was close to zero. The errors produced by blood gas analysers can thus be minimised in two ways: firstly, by simply introducing a P50 estimated from the age of the calf into the analyser before the measurement; and secondly, by calculating the SO(2) using a mathematical model applied to the bovine OEC.     

Arterialized capillary blood used to determine the acid-base and blood gas status of dogs.

Blood samples were collected by microhematocrit tube from posterior medial margin of the shaved, but otherwise untreated, canine ear. Acid-base and blood gas values of these samples were compared with the values of samples obtained simultaneously from the carotid artery. The arterialized nature of capillary blood from the canine ear was demonstrated under various degrees of chemical restraint and during conditions of extreme hypoxic acidosis to hyperventilatory alkalosis. Once a week determinations of acid-base and blood gas status with such arterialized capillary blood from a group of awake dogs showed within-subject variance to be significantly less (P less than 0.05) than between-subject variance; thus, uniqueness of individual dogs was reliably revealed. This technique also was used to demonstrated breed differences for acid-base and blood gas characteristics.     

Comparison of PO2, PCO2, and pH in blood collected from the femoral artery and a cut claw of cats

A technique for collection of blood samples from the cut claw of the cat was developed. Forty-six blood samples were collected simultaneously from the cut claw and the femoral artery of 7 healthy cats. Blood gas and pH values were measured and compared. There was no difference between sample pairs for blood PO2 and PCO2, but the pH values were significantly (P less than 0.001) higher in the capillary samples (7.432 +/- 0.033) than in the samples from the femoral artery (7.419 +/- 0.031).     

Equine endotoxemia: cardiovascular, eicosanoid, hematologic, blood chemical, and plasma enzyme alterations

Ponies with electromagnetic blood flow transducers implanted around the main pulmonary and left main coronary arteries, were used to evaluate effects of chronic sublethal endotoxin on cardiac output (CO), stroke volume, and left coronary blood flow (LCBF). Plasma thromboxane (TX), as indicated by TXB2, prostacyclin as indicated by 6-keto-prostaglandin (PG) F1 alpha, and hematologic and blood chemical values also were evaluated. Over 24 hours, 2 groups of ponies were given progressively increasing IV and intraperitoneal doses of Escherichia coli lipopolysaccharide (LPS) at 0, 6, 12, and 18 hours. Group 1 was not treated and group 2 was treated with flunixin meglumine, before each LPS insult. Initial LPS inoculation in group 1 led to 10-fold increases in TXB2 and 6-keto-PGF1 alpha values by 30 and 90 minutes, respectively. These eicosanoid values returned to base line by 6 hours after each insult. Although repeated LPS injections stimulated recurring high plasma concentrations of 6-keto-PGF1 alpha, TXB2 production became less with each successive LPS insult. Cardiac output decreased to 55% to 60% of base-line values in association with increased 6-keto-PGF1 alpha values. Left coronary blood flow could not be evaluated accurately. Severe lactic acidosis developed in group 1. Group-2 ponies remained clinically normal, indicating protection of cardiovascular function and peripheral perfusion with flunixin meglumine. Seemingly, flunixin meglumine helped to maintain acceptable cardiovascular function and tissue perfusion during endotoxemia. Flunixin meglumine given to healthy ponies had no effect on cardiovascular function.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of a point-of-care blood analyzer and determination of reference ranges for blood parameters in rockfish

OBJECTIVE: To compare values of blood parameters in rockfish obtained by use of a point-of-care portable blood analyzer with values determined by a veterinary diagnostic laboratory, calculate reference ranges for various blood parameters in black rockfish, and compare values of blood parameters in clinically normal fish with those of fish with clinical abnormalities. DESIGN: Prospective study. ANIMALS: 41 captive adult black rockfish (Sebastes melanops) and 4 captive adult blue rockfish (Sebastes mystinus). PROCEDURE: Rockfish were anesthetized with tricaine methanesulfonate for collection of blood samples. Heparinized blood samples were immediately analyzed with a point-of-care analyzer. Blood sodium, potassium, chloride, urea nitrogen, and glucose concentrations; Hct; pH; partial pressure of carbon dioxide; total carbon dioxide concentration; bicarbonate concentration; base excess; and hemoglobin concentration were determined. A microhematocrit technique was used to determine PCV, and a refractometer was used to estimate total plasma protein concentration. Paired heparinized blood samples were transported to a veterinary diagnostic laboratory for analyses. RESULTS: Data obtained with the point-of-care analyzer were reproducible; however, values for most blood parameters were significantly different from those obtained by the veterinary diagnostic laboratory. Fish with poor body condition had several blood parameter values that were lower than corresponding values in clinically normal fish. CONCLUSIONS AND CLINICAL RELEVANCE: Point-of-care blood analyses may prove useful in rockfish. Point-of-care data for a large number of clinically normal fish must be obtained for reference ranges to be calculated, and further assessments of clinically abnormal fish are necessary to determine the relevance of the data.     

Evaluation of noninvasive blood pressure in anesthetized horses: Bias,limits of agreement,and comparative detection of a predetermined mean blood pressure warranting treatment

Oscillometric blood pressure monitoring may be a practical tool for short procedures or those performed outside of the operating room. Oscillometric and direct blood pressure values in 30 juvenile and adult horses in a clinical setting using mixed effect models were compared. The limits of agreement and percentage errors were also calculated. We evaluated the sensitivity and false positive rate for the oscillometric method to trigger an intervention for treating blood pressure [direct mean arterial pressure (MAP) < 70 mmHg]. Oscillometric MAP and diastolic arterial pressure (DAP) differed from direct values (P < 0.001); systolic arterial pressure (SAP) did not (P = 0.08). Wide limits of agreement were observed. Percentage errors were smaller for SAP (39%) than for MAP and DAP (48% and 72%). The oscillometric monitor indicated there was a requirement for blood pressure treatment with a true positive rate of 82%, consequently, it failed 18% of the times. The false positive rate (unnecessary treatment) was 55%.     

A comparison of pO2, pCO2, pH and bicarbonate in blood from the carotid and coccygeal arteries of calves

A technique is described for the subcutaneous deviation of the carotid artery into the jugular groove of calves weighing between 90 and 200 kg. This makes sampling arterial blood or chronic cannulation for further experimentation very easy. Values of oxygen tension, carbon dioxide tension, pH and bicarbonate concentration in blood sampled from the ventral coccygeal artery were compared with the values obtained in blood from carotid artery puncture. The high correlations observed indicate that blood samples from the ventral coccygeal artery can be used for measurement of blood gases and pH in calves.     

The effect of arterial blood sampling sites on blood gases and acid-base balance parameters in calves.

In 21 healthy calves, 1-6 months old, the interrelationship and comparability of acid-base balance variables (pH, HCO3-, BE) and blood gases (pCO2, pO2, and sat-O2) were evaluated in arterial blood collected from a larger, centrally localised (the a. axillaris) and a smaller peripheral artery (the a. auricularis caudalis). Sampling was done by direct puncture of the vessels without local anaesthesia. Except for blood pH, significant differences were observed in the average values of pCO2, pO2, HCO3-, sat-O2 (P < 0.001), and BE (P < 0.05). Analyses of blood from the a. axillaris showed higher pH, pO2, and sat-O2 values, and lower pCO2, HCO3-, and BE values compared with that from the a. auricularis caudalis. Despite statistically significant differences between some variables, in all indices high and significant correlation relationships were recorded (R = 0.928-0.961; P < 0.001). Therefore, from the biological and clinical point of view, these differences are unimportant and the presented method of peripheral arterial blood sampling can be considered suitable for evaluating blood gases and acid-base status.     

Blood gas, oxygen saturation, pH, and lactate values in elasmobranch blood measured with a commercially available portable clinical analyzer and standard laboratory instruments

Blood gas, pH, and lactate data are often used to assess the physiological status and health of fish and can often be most valuable when blood samples are analyzed immediately after collection. Portable clinical analyzers allow these measurements to be made easily in the field. However, these instruments are designed for clinical use and thus process samples at 37 degrees C. A few studies have validated the use of portable clinical analyzers for assessing blood gases and acid-base profiles in teleosts, but equivalent data are not available for elasmobranchs. We therefore examined the relationship of blood gas, pH, and lactate values measured with an i-STAT portable clinical analyzer with those measured using standard laboratory blood gas (thermostatted to 25 degrees C) and lactate analyzers in samples taken from three species of carcharhiniform sharks. We found tight correlations (r2 > 0.90) between these methods for pH, pO2, pCO2, and lactate level values. We thus developed species-specific equations for converting blood values measured with an i-STAT portable clinical analyzer to those taken at 25 degrees C. Additional studies need to address a wider range of temperatures and elasmobranch species.     

Cardiovascular, haematological and biochemical responses after large volume blood collection in horses.

To determine whether removal of 20 mL/kg of blood (approximately 25% of blood volume) resulted in adverse physiological effects in donor horses, we removed this volume of blood from five horses and selected cardiovascular, haematological and biochemical variables measured during collection and for 31 days thereafter. We found that alteration in most variables occurred, although the changes in values usually remained within published reference ranges. Also, recovery of these alterations to pre-collection values was rapid, occurring within 24--48 h in most instances. We concluded that volumes of blood less than or equal to 20 mL/kg when collected appropriately from healthy donor horses result in no adverse acute or chronic physiological changes. These results suggest that horses undergo adequate physiological compensation when approximately 25% of blood volume is removed for the purposes of blood donation or production of plasma.     

Evaluation of intestinal intramucosal pH,arterial and portal venous blood gas values,and intestinal blood flow during small intestinal ischemia and reperfusion in dogs

OBJECTIVES: To determine whether small intestinal ischemia and reperfusion affects intestinal intramucosal pH (pHi), arterial and portal venous blood gas values, and intestinal blood flow (IBF) and to investigate relationships between regional intestinal tissue oxygenation and systemic variables in dogs. ANIMALS: 15 healthy adult Beagles. PROCEDURE: Occlusion of superior mesenteric artery (SMA) for 0, 30, or 60 minutes, followed by reperfusion for 180 minutes, was performed; IBF, pHi, arterial and portal venous blood gas values, arterial pressure, and heart rate were measured at various time points; and intestinal mucosal injury was histologically graded. RESULTS: Occlusion of the SMA induced significant decreases in pHi and IBF. After the release of the occlusion, IBF returned rapidly to baseline values, but improvement in pHi was slow. Arterial and portal venous blood gas analyses were less sensitive than tonometric measurements of pHi, and there was no correlation between results of blood gas analyses and tonometric measurements. Histologic score for intestinal mucosal injury increased significantly, depending on duration of ischemia, and there was a correlation between tonometric results and the histologic score. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that it is difficult to accurately evaluate local oxygenation disorders by monitoring at the systemic level, whereas clinically pHi is the only reliable indicator of inadequate regional intestinal tissue oxygenation in dogs.     

Mineral levels of the arterial and venous blood in cows

The values of calcium, phosphorus, magnesium, potassium and sodium in the arterial and venous blood of cows before and after milking two to three months from calving were found to be within the standard range. The differences are not significant. In venous blood the values are lower than in arterial blood, which proves that minerals are utilized by the organisms for milk production. The values of minerals in the blood of the Slovak Spotted cows are higher than in the blood of the Black--Pied Lowland cows; they are also higher in the blood of lower-performance cows than in the blood of cows giving high milk yields. This means in practice that Black-Pied Lowland cows and high-performance cows need a higher supply of minerals to their blood stream.     

Accuracy of a portable blood gas analyzer incorporating optodes for canine blood

The accuracy of a portable blood gas analyzer (OPTI 1) was evaluated using canine blood and aqueous control solutions. Sixty-four arterial blood samples were collected from 11 anesthetized dogs and were analyzed for pH, partial pressure of carbon dioxide (PCO2) partial pressure of oxygen (PO2), and bicarbonate concentration ([HCO3-]) values by the OPTI 1 and a conventional blood gas analyzer (GASTAT 3). The conventional analyzer was considered as a standard against which the OPTI 1 was evaluated. Comparison of OPTI 1 results with those of GASTAT 3 by linear regression analysis revealed a high degree of correlation with the GASTAT 3 (r = .90-.91). The mean +/- SD of the differences between OPTI 1 and GASTAT 3 values was -0.008 +/- 0.017 for pH, -0.88 +/- 3.33 mm Hg for PCO2, 3.71 +/- 6.98 mm Hg for PO2, and -0.34 +/- 1.45 mEq/L for [HCO3-]. No statistically significant difference was found between the OPTI 1 and the GASTAT 3. Agreement between these 2 methods is within clinically acceptable ranges for pH, PCO2, PO2, and [HCO3-]. The coefficients of variation for measured pH, PCO2, and PO2 values of 3 aqueous control solutions (acidic, normal, and alkalotic) analyzed by the OPTI 1 ranged from 0.047 to 0.072% for pH, 0.78 to 1.81% for PCO2, and 0.73 to 2.77% for PO2. The OPTI 1 is concluded to provide canine blood gas analysis with an accuracy that is comparable with that of conventional benchtop blood gas analyzers.     

Ionized calcium and total calcium in the blood of cattle, sheep, swine and horses of different ages, reproductive stages and uses]

Concentrations of ionized calcium (Cai) in blood and of total calcium (Ca(t)) in serum were determined in 99 cattle, 58 sheep, 74 pigs and 59 horses of different age groups and reproductive periods as well as kinds of use of the animals. The values of Cai in blood in the groups taken into account for comparison of species decreased significantly in the order dairy cows < ewes < sows < horses. In cattle and pigs, there were significant differences in the Cai-level, according to age with the youngest animals having the highest values. In cows from the fourth lactation onward, one day post partum (p.p.) the smallest concentrations were measured, differing significantly from animals in other reproductive periods. In ewes, the lowest values were estimated one week before parturition. The level of Cai in blood of sows decreased between day one and 6 weeks p.p. significantly. No significant differences could be demonstrated between the different groups of horses. With regard to the concentrations of total Ca, differences between the groups were not so clear as with Cai.     

Annual dynamics of acidobasic indices in the sheep blood]

Altogether 218 sheep were followed for a year and the values of their acidobasic indices were examined, the follow-up comprises all seasons of the year, gravidity period, time of nursing and milk production. The actual pH value in the sheep blood varied from 7.30 to 7.48, with 7.40 average. The average value of partial CO2 pressure amounted to 37.26 torr the individual values varying between 30.0 and 47.5 torr. Baz excess varies from +5.0 to -6.3 mval/1 blood with year average of 1.11 mval/1 blood. Buffer baz was 43.0 mval/1 on the average, with variations from 34.2 to 48.9 mval/1 blood. Standard bicarbonate showed a relatively broad range of values from 19.0 to 28.0 mval/1 plasma, with 22.85 mval/1 average. Actual bicarbonate manifested similar variation dynamics as SB. Annual average was 22.92 mval/1 plasma, with variations from 19.0 to 28.2 mval/1. Total plasmatic CO2 had balanced average monthly values, with year average of 23.84 mval/1. Generally it can be concluded that after the sheep being out to grass the acidobasic blood indices became regulated.     

Serum concentrations of micronutrients, packed cell volume, and blood hemoglobin during the first two gestations and lactations of sows.

The objective of the present work was to describe the changes in serum concentrations of some micronutrients during the first 2 gestations and lactations of 33 gilts in order to establish blood reference values for a rapid assessment of nutritional status. In both parities, blood samples were taken from the jugular vein at mating, 5, 10 and 15 wk of gestation and l d and 4 wk after parturition (weaning). Reference values (mean, standard deviation, minimum, maximum) for serum folates, vitamin B12, vitamin B6 metabolites (pyridoxal and pyridoxal-5-phosphate), calcium, phosphorus, sodium, zinc, copper and iron, as well as blood hemoglobin and packed cell volume are reported for each studied time. Differences between parities and between each time are also reported. Results from the present report demonstrate that knowledge of the physiological state of the sows is critical for the assessment of nutritional status of an individual or a breeding herd by interpretation of analyses of blood constituents.