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Summary

Cardiopulmonary effects of etomidate administration were studied in hypovolemic dogs. Baseline cardiopulmonary data were recorded from conscious dogs after instrumentation. Hypovolemia was induced by withdrawal of blood from dogs until mean arterial pressure of 60 mm of Hg was achieved. Blood pressure was maintained at 60 mm of Hg for 1 hour, by further removal or replacement of blood. One milligram of etomidate/kg of body weight was then administered iv to 7 dogs, and the cardiopulmonary effects were measured 3, 15, 30, and 60 minutes later. After blood withdrawal and prior to etomidate administration, heart rate, arterial oxygen tension, and oxygen utilization ratio increased. Compared with baseline values, the following variables were decreased: mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, mixed venous oxygen content, and arterial carbon dioxide tension. Three minutes after etomidate administration, central venous pressure, mixed venous and arterial carbon dioxide tension, and venous admixture increased, and heart rate, arterial and venous pH, and arterial oxygen tension decreased, compared with values measured immediately prior to etomidate administration. Fifteen minutes after etomidate injection, arterial pH and heart rate remained decreased. At 30 minutes, only heart rate was decreased, and at 60 minutes, mean arterial pressure was increased, compared with values measured before etomidate administration. Results of this study indicate that etomidate induces minimal changes in cardiopulmonary function when administered to hypovolemic dogs.

Free access
in American Journal of Veterinary Research

SUMMARY

The cardiopulmonary effects of thiopental sodium were studied in hypovolemic dogs from completion of until 1 hour after administration of the drug. Hypovolemia was induced by withdrawal of blood from dogs until mean arterial pressure of 60 mm of Hg was achieved. After stabilization at this pressure for 1 hour, 8 mg of thiopental/kg of body weight was administered iv to 7 dogs, and cardiopulmonary effects were measured. After blood withdrawal and prior to thiopental administration, heart rate and oxygen utilization ratio increased, whereas mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, and mixed venous oxygen content decreased from baseline. Three minutes after thiopental administration, heart rate, mean arterial pressure, mean pulmonary arterial pressure, pulmonary vascular resistance, and mixed venous oxygen tension increased, whereas oxygen utilization ratio and arterial and mixed venous pH decreased from values measured prior to thiopental administration. Fifteen minutes after thiopental administration, heart rate was still increased; however by 60 minutes after thiopental administration, all measurements had returned to values similar to those obtained prior to thiopental administration.

Free access
in American Journal of Veterinary Research

SUMMARY

Conventional fluid resuscitation is unsatisfactory in a small percentage of equine emergency surgical cases because the large volumes of fluids required cannot be given rapidly enough to adequately stabilize the horse. In anesthetized horses, the volume expansion and cardiopulmonary effects of a small volume of highly concentrated hypertonic saline-dextran solution were evaluated as an alternative initial fluid choice. Seven halothane-anesthetized, laterally recumbent, spontaneously ventilating, normovolemic horses were treated with a 25% NaCl-24% dextran 70 solution (hsd) at a dosage of 1.0 ml/kg of body weight, iv, infused over 10 minutes, and the effects were measured for 120 minutes after infusion. Plasma volume expansion was rapid and significant (from 36.6 ± 4.6 ml/kg to 44.9 ± 4.8 ml/kg), and remained significantly expanded for the duration of the experiment. Packed cell volume, total blood hemoglobin, and plasma protein concentrations significantly decreased, confirming rapid and sustained volume expansion with hemodilution. Cardiac index and stroke index immediately increased and remained high for the entire study (from 69.6 ± 15.3 ml/min/kg to 106.6 ± 28.4 ml/min/kg, and from 1.88 ± 0.49 ml/beat/kg to 2.50 ± 0.72 ml/beat/kg, respectively). Systemic vascular resistance significantly decreased immediately after hsd infusion and remained decreased for the duration of the study (from 1.41 ± 0.45 mm of Hg/ml/min/kg to 0.88 ± 0.22 mm of Hg/ml/min/kg). Arterial and venous blood oxygen content decreased significantly because of hemodilution, but actual oxygen transport transiently increased at the 10-minute measurement before returning toward baseline. Plasma osmolality and sodium significantly increased and remained high for the entire 120 minutes (from 293 ± 2 osm/L to 326 ± 9 mosm/L, and from 142.8 ± 3.3 mM/L to 159.0 ± 6.2 mM/L, respectively). Urine output increased in 5 of 7 horses within minutes of hsd infusion, but the mean increase was not statistically significant.

Three horses developed transiently severe, clinically apparent intravascular hemolysis and hemoglobinuria. One horse developed multiple single premature ventricular contractions during the infusion with no persistent ecg changes after infusion. The potential benefit of using hsd as a rapid volume expander in anesthetized horses was documented because infusion of 1 ml of hsd/kg rapidly increased plasma volume by approximately 8 ml/kg. Substantial side effects developed in these normovolemic horses, however, and this solution requires further investigation before it can be recommended in hemodynamically unstable horses.

Free access
in American Journal of Veterinary Research

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)

Full access
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.

Full access
in Journal of the American Veterinary Medical Association

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.

Full access
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)

Full access
in Journal of the American Veterinary Medical Association