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Abstract

Objective—To describe the effects of increasing the extracellular fluid (ECF) volume by approximately 20% on acid-base changes and electrolyte concentrations in anesthetized rats.

Animals—18 adult male Sprague-Dawley rats.

Procedures—Rats were assigned to a control group (n = 6 rats) and a treatment group (12). All rats were anesthetized, and instrumentation and bilateral renal pedicle ligation were performed. The treatment group was infused IV with sterile water throughout a 30-minute period. Acid-base variables and concentrations of electrolytes, lactate, albumin, phosphorus, and hemoglobin were measured before (baseline) and 30 and 60 minutes after onset of infusion. Anion gap, strong ion difference, strong ion gap, and contributions of sodium, chloride, albumin, phosphorus, and lactate concentrations to base excess were calculated at each time point.

Results—Infusion of sterile water led to an increase in ECF volume of approximately 18%. This had no effect on acid-base balance, compared with that in control rats. Infusion of sterile water caused a significant decrease in sodium, chloride, ionized calcium, lactate, and albumin concentrations, compared with concentrations in the control group. Anion gap and calculated effects of sodium, chloride, albumin, and lactate concentrations on base excess at 60 minutes differed significantly between infused and control rats.

Conclusions and Clinical Relevance—Infusion of sterile water did not cause clinically relevant dilutional acidosis. The acidotic impact of water administration was offset by generation of new bicarbonate via carbonic acid equilibration and intracellular buffering in combination with the alkalotic effects of decreases in albumin, phosphorus, and lactate concentrations.

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in American Journal of Veterinary Research

Abstract

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. (Am J Vet Res 2005;66:656–660)

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in American Journal of Veterinary Research

Abstract

Objective—To determine whether peripheral venous pressure (PVP) was correlated with central venous pressure (CVP) when measured by use of different catheter sizes, catheterization sites, and body positions in awake dogs and cats.

Animals—36 dogs and 10 cats.

Procedures—Dogs and cats with functional jugular and peripheral venous catheters were enrolled in the study. Peripheral venous catheters (18 to 24 gauge) were placed in a cephalic, lateral saphenous, or medial saphenous vein. Central venous catheters (5.5 to 8.5 F) were placed in the jugular vein and advanced into the cranial vena cava. Catheters were connected to pressure transducers and a blood pressure monitor capable of displaying 2 simultaneous pressure tracings. For each animal, the mean of 5 paired measurements of PVP and CVP was calculated. The relationship between PVP and CVP when measured by use of different catheter sizes, catheterization sites, and body positions was determined.

Results—Mean ± SD PVP was 5.7 ± 5.8 mm Hg higher than CVP in dogs and 6.0 ± 6.9 mm Hg higher than CVP in cats. However, results of multiple regression analysis did not indicate a significant correlation between PVP and CVP, regardless of catheter size, catheter position, or body position. The relationship was weak in both dogs and cats.

Conclusions and Clinical Relevance—The PVP was poorly correlated with CVP when different catheter sizes, catheterization sites, and patient positions were evaluated. Peripheral venous pressure should not be used to approximate CVP in awake dogs and cats.

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effect of 2 hydroxyethyl starch (HES) preparations (ie, HES solution with a molecular weight of 600 kd and a degree of substitution of 0.7 [HES 600/0.7] and a calcium-containing polyionic HES solution with a molecular weight of 670 kd and a degree of substitution of 0.75 [HES 670/0.75]) on canine platelet function.

Sample Population—Blood samples from 10 healthy adult dogs.

Procedures—Dilution of citrated whole blood was performed with saline (0.9% NaCl) solution, HES 600/0.7, and HES 670/0.75 at ratios of 1:9 (ie, 1 part saline solution or colloid to 9 parts whole blood) and 1:3. Measurements of time to platelet plug formation in a capillary tube (ie, closure time) were made by use of a bench-top platelet function analyzer with collagen and ADP platelet agonists.

Results—Mean baseline closure time was 68.0 ± 15.3 seconds. A 1:3 dilution of whole blood with saline solution, HES 600/0.7, and HES 670/0.75 resulted in mean closure times of 85.8 ± 15.7 seconds, 100.6 ± 18.6 seconds, and 101.6 ± 16.2 seconds, respectively. Closure time following 1:3 dilution of whole blood with saline solution was significantly different from baseline and from 1:9 dilution with saline solution. Closure time following 1:3 dilution of whole blood with HES 670/0.75 was significantly different from baseline, 1:3 and 1:9 dilutions with saline solution, and 1:9 dilutions with HES 600/0.7 or HES 670/0.75.

Conclusions and Clinical Relevance—Saline solution, HES 600/0.7, and HES 670/0.75 affect canine platelet function by prolonging closure times; HES solutions prolonged closure time to a greater extent than saline solution.

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in American Journal of Veterinary Research

Abstract

Objective—To determine outcome of positive-pressure ventilation (PPV) for 24 hours or longer and identify factors associated with successful weaning from PPV and survival to hospital discharge in dogs and cats.

Design—Retrospective case series.

Animals—124 dogs and 24 cats that received PPV for 24 hours or longer.

Procedures—Medical records were reviewed for signalment, primary diagnosis, reason for initiating PPV, measures of oxygenation and ventilation before and during PPV, ventilator settings, complications, duration of PPV, and outcome. Animals were categorized into 1 of 3 groups on the basis of the reason for PPV.

Results—Group 1 patients received PPV for inadequate oxygenation (67 dogs and 6 cats), group 2 for inadequate ventilation (46 dogs and 16 cats), and group 3 for inadequate oxygenation and ventilation (11 dogs and 2 cats). Of the group 1 animals, 36% (26/73) were weaned from PPV and 22% (16/73) survived to hospital discharge. In group 2, 50% (31/62) were weaned from PPV and 39% (24/62) survived to hospital discharge. In group 3, 3 of 13 were weaned from PPV and 1 of 13 survived to hospital discharge. Likelihood of successful weaning and survival to hospital discharge were significantly higher for group 2 animals, and cats had a significantly lower likelihood of successful weaning from PPV, compared with dogs. Median duration of PPV was 48 hours (range, 24 to 356 hours) and was not as-sociated with outcome.

Conclusions and Clinical Relevance—Results suggested that long-term PPV is practical and successful in dogs and cats.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare direct measurements of canine oxyhemoglobin (HbO2) saturation and blood oxygen content (ContO2) in healthy dogs with analyzer-calculated values derived by use of a human HbO2 relationship and with hand-calculated values derived by use of a canine HbO2 relationship.

Animals—17 healthy dogs.

Procedure—3-mL samples of heparinized arterial and jugular venous blood were collected from each dog. The pH, PCO2, PO2, hemoglobin, HbO2, carboxyhemoglobin, methemoglobin, and ContO2 were measured; HbO2 and ContO2 were calculated automatically by analyzers and also hand-calculated. Blood gas analyzer–calculated and hand-calculated HbO2 values were compared with co-oximeter–measured HbO2 values. Analyzer-calculated and hand-calculated ContO2 values were compared with oxygen content analyzermeasured values.

Results—Hand-calculated HbO2 values for arterial and jugular venous samples were slightly but significantly lower than those calculated by a blood gas analyzer or obtained from a co-oximeter. Hand-calculated and analyzer-calculated arterial and venous ContO2 were similar to measured values.

Conclusions and Clinical Relevance—Although certain HbO2 and ContO2 values generated by use of the different methods were significantly different, these differences are unlikely to be clinically important in healthy dogs. (Am J Vet Res 2005;66:1273–1277)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate the use of the oxygen content–based index, Fshunt, as an indicator of venous admixture (s/t) at various fractions of inspired oxygen (Fio 2s) in anesthetized sheep undergoing Flung or 2-lung ventilation.

Animals—6 healthy adult female sheep.

Procedures—Sheep were anesthetized and administered 5 different Fio 2s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each Fio 2 after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used Fio 2 sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, s/t, Fshunt, and oxygen tension–based indices (OTIs; including Pao 2:Fio 2, alveolar-arterial difference in partial pressure of oxygen [Pao 2 – Pao 2], [Pao 2 – Pao 2]:Fio 2, [Pao 2 – Pao 2]:Pao 2, and Pao 2:Pao 2) were calculated at each Fio 2; associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between s/t and Fshunt was tested via Bland-Altman analysis.

Results—Strong and significant associations and substantial agreement were detected between Fshunt and s/t. Relationships between OTIs and s/t varied, but overall correlations were weak.

Conclusions and Clinical Relevance—Whereas OTIs were generally poor indicators of s/t, Fshunt was a good indicator of s/t at various Fio 2s, regardless of the magnitude of s/t, and could be potentially used as a surrogate for s/t measurements in healthy sheep.

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in American Journal of Veterinary Research

Abstract

Objective—To determine incidence of and possible risk factors for catheter-associated urinary tract infection (UTI) among dogs hospitalized in an intensive care unit and compare results of bacterial culture of urine samples with results of bacterial culture of catheter tips.

Design—Prospective study.

Animals—39 dogs.

Procedure—A standard protocol for aseptic catheter placement and maintenance was used. Urine samples were obtained daily and submitted for bacterial culture. When possible, the urinary catheter tip was collected aseptically at the time of catheter removal and submitted for bacterial culture. Bacteria that were obtained were identified and tested for antimicrobial susceptibility.

Results—4 of the 39 (10.3%) dogs developed a UTI. The probability of remaining free from UTI after 1 day in the intensive care unit was 94.9%, and the probability of remaining free from UTI after 4 days was 63.3%. Bacteria isolates were generally common urinary tract pathogens and were susceptible to most antimicrobials. Specific risk factors for catheter-associated UTI, beyond a lack of antimicrobial administration, were not identified. Positive predictive value of bacterial culture of urinary catheter tips was only 25%.

Conclusions and Clinical Relevance—Results suggest that placement of an indwelling urinary catheter in dogs is associated with a low risk of catheter-associated UTI during the first 3 days after catheter placement, provided that adequate precautions are taken for aseptic catheter placement and maintenance. Results of bacterial culture of urinary catheter tips should not be used to predict whether dogs developed catheter-associated UTI. (J Am Vet Med Assoc 2004;224:1936–1940)

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in Journal of the American Veterinary Medical Association