Effect of endotoxin administration on equine digital hemodynamics and starling forces

Using a pump-perfused extracorporeal isolated digital preparation, the effects of a 30-minute infusion of either saline solution (control) or endotoxin on equine digital hemodynamics and microvascular function were determined. Digital blood flow and arterial, venous, and capillary pressures were recorded at 15-minute intervals for 150 minutes. From these data, total vascular resistance and pre- and postcapillary resistances were calculated. Isogravimetric capillary filtration coefficient, vascular compliance, and the osmotic reflection coefficient were determined after the last hemodynamic measurements were taken. Changes in hemodynamic values of control equine digits were not observed. During the 120 minutes after infusion of endotoxin, digital blood flow decreased 43%, and total vascular resistance increased 89%. Precapillary resistance increased 122%, but postcapillary resistance did not change significantly. Changes in vascular compliance or the capillary filtration coefficient were not observed in response to either treatment. The osmotic reflection coefficient, an index of permeability, did not differ significantly between digits of the endotoxin-treated and control groups. These data indicate that the increase in vascular resistance during endotoxemia may have been attributable to arterial/arteriolar constriction and that neither the permeability nor the surface area of the exchange vasculature within the digit was significantly affected by endotoxin. Although marked alterations in vascular function are seen after administration of endotoxin, these changes do not parallel those documented in association with experimentally induced laminitis.     

Capillary permeability to endogenous macromolecules in the equine digit

Microvascular permeability characteristics were evaluated in digits of 7 adult horses. After capillaries were isolated and an extracorporeal perfusion circuit for the digit was established, a lymphatic vessel draining the distal portion of the phalangeal region was cannulated at the level of the coronary band. Venous pressure was increased in a stepwise manner, and lymph flow, lymph protein concentration (Cl), and plasma protein concentration (Cp) were determined after measured variables were allowed to reach steady state. Lymph-to-plasma protein concentration ratios (Cl/Cp) and lymph and plasma oncotic pressures were determined from samples collected during steady state. The osmotic reflection coefficient was determined after Cl/Cp became constant, regardless of increasing lymph flow, and was expressed as 1--Cl/Cp. The osmotic reflection coefficient for the digit was 0.67. Seemingly, the microvasculature bed of the digit was relatively permeable and could maintain only 67% of the endogenous macromolecules within the vasculature.     

Muscle hemodynamics in hereditary myopathy of Labrador retrievers

Morphologic lesions seen in six 8-month-old Labrador Retrievers with hereditary myopathy were predominantly small- and large-group atrophy of muscle cells of all fiber types. The dogs were intolerant of exercise and fatigued rapidly. An isolated gracilis muscle preparation was used to study the hemodynamic features of the microvasculature. Isogravimetric capillary pressure as well as arterial and venous pressures in the isolated gracilis muscle preparation obtained during maximal vasodilatation were within the range reported for healthy, mixed-breed dogs, as were precapillary, postcapillary, and total vascular resistances. Capillary filtration and osmotic reflection coefficients were not different from those reported in other studies on healthy dogs. All measurements and calculations were repeated during reperfusion, subsequent to a 4-hour period of global ischemia. Postischemic vascular responses were similar to the pattern previously reported in healthy dogs. These studies did not support the hypothesis of a vascular defect as a cause of hereditary myopathy in Labrador Retrievers.     

Hypoperfusion of the small intestine during slow infusion of a low dosage of endotoxin in anesthetized horses

The effects of intravenous infusion of endotoxin for 30 minutes at a cumulative dosage of 0.03 micrograms/kg on average carotid arterial pressure, and on average arterial pressure, capillary pressure, venous pressure, total vascular resistance, precapillary resistance, postcapillary resistance, and capillary filtration coefficient in the jejunum were compared to the effects of intravenous infusion of 0.9% sodium chloride solution in 6 anesthetized horses. Endotoxin significantly reduced intestinal venous blood flow by inducing vasoconstriction. Increased vascular resistance resulted from increased precapillary resistance. The capillary filtration coefficient was unchanged by endotoxin. These results suggest that intestinal vasoconstriction occurs during the compensatory stages of endotoxemia.     

Crystalloids versus colloids: implications in fluid therapy of dogs with intestinal obstruction

Responses of jejunal transcapillary and transmucosal fluid fluxes to IV infusion of crystalloid or colloid solutions were evaluated in 12 dogs. One isolated intestinal segment in each dog was used as the control segment, and 2 segments were distended to a intraluminal hydrostatic pressure of 10 cm of H2O. The artery supplying 1 of the 2 distended (autoperfused) segments was cannulated and perfused with blood from the femoral artery. One of the 2 distended segments was autoperfused from the femoral artery. Intraluminal pressure was increased in the autoperfused segment and in 1 other segment for three, 20-minute periods after administration of the crystalloid or colloid solution. Net transmucosal fluid flux was estimated, using a volume recovery method. In each autoperfused segment, blood flow, capillary pressure, lymph flow, and plasma protein and lymph protein concentrations were measured during each 20-minute distention period. Systemic arterial pressure was monitored throughout the procedure. Plasma and tissue oncotic pressures were calculated from the plasma protein and lymph protein concentrations. Total vascular resistance and precapillary and postcapillary resistances were determined. Capillary pressure increased after infusion with colloids and crystalloids, with the effects being more prolonged in the colloid group. Plasma oncotic pressure transiently increased after infusion with colloids and decreased after infusion with crystalloids. Lymph flow increased only in crystalloid-treated dogs. Due to alterations in transcapillary fluid filtration, crystalloids induced a net loss of fluid into the intestinal lumen, whereas the fluid absorptive capacity of the jejunum was unaltered by colloid treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pathophysiology of acute laminitis

This article reviews research findings relating to the pathophysiology of acute laminitis in horses. The data presently available suggest that the onset of the condition may be due to constriction of the postcapillary vessels in the digit, leading to increased capillary hydrostatic pressure and movement of fluid into the interstitial space.     

Hemodynamic responses of the equine digit to intravenous and digital arterial infusion of dopamine

In 6 adult horses anesthetized with pentobarbital, the hemodynamic responses of the equine digit to infusion of dopamine were evaluated by use of an isolated extra corporeal pump perfused digital preparation. Digital blood flow was maintained at a constant rate that was independent of systemic hemodynamic changes. Three sequential experiments were performed on each horse. In the first experiment (n = 6), dopamine was infused IV at rates of 1.0, 2.5, and 5.0 micrograms/kg/min. For the second experiment (n = 5), dopamine (400 micrograms/ml) was infused into the digital artery at the rates of 0.07, 0.7, and 1.2 ml/min. The third experiment (n = 5) consisted of a 5-minute intra-arterial infusion of phentolamine followed by the intra-arterial infusion of dopamine while continuing the infusion of phentolamine. Digital venous, arterial, and capillary pressures, total digital vascular resistance, and precapillary to postcapillary resistance ratios were determined in each experiment. Systemic infusion of dopamine did not induce changes in the hemodynamics of the digital vasculature. Digital arterial infusion of dopamine alone resulted in a dose-dependent increase in arterial pressure, total digital vascular resistance, and an increase in the precapillary to postcapillary resistance ratio. Phentolamine attenuated the vasoconstrictive response elicited by intra-arterial infusion of dopamine.     

Effects of an endothelin receptor antagonist and nitroglycerin on digital vascular function in horses during the prodromal stages of carbohydrate overload-induced laminitis

OBJECTIVE: To evaluate changes in digital vascular function in horses with carbohydrate overload (CHO)-induced laminitis and determine the effects of an endothelin (ET) receptor antagonist and nitroglycerin on laminitis-associated vascular dysfunction. ANIMALS: 20 adult horses without abnormalities of the digit. PROCEDURES: Hemodynamic variables were recorded before (baseline) and hourly after all horses were administered a CHO ration via nasogastric tube. In 4 groups of 5 horses each, saline (0.9% NaCl) solution or ET receptor antagonist (10(5)M in digital blood) was administered into the digital arterial circulation according to 1 of 2 schedules. During anesthesia, blood flow; arterial, venous, and capillary pressures; and total, precapillary, and postcapillary resistances were measured in an isolated perfused digit of each horse. In all groups, nitroglycerin was infused (10(5)M in digital blood), and digital microvascular assessments were repeated. RESULTS: The CHO caused a significant decrease in right atrial pressure by 14 hours that was not affected by administration of saline solution or ET receptor antagonist. In isolated digits of anesthetized horses, CHO resulted in a significant decrease in digital blood flow associated with a significant increase in total and postcapillary resistances. Treatment with the ET receptor antagonist and nitroglycerin caused a significant decrease in total resistance. Postcapillary resistance was significantly decreased following treatment with the ET receptor antagonist but was not altered by treatment with nitroglycerin. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with an ET receptor antagonist and nitroglycerin resulted in significant improvement in vascular resistance in isolated perfused digits of anesthetized horses with CHO-induced laminitis.     

The Use of Hetastarch as Adjunct Therapy in 26 Dogs With Hypoalbuminemia: A Phase Two Clinical Trial

The purpose of this study was to evaluate the safety and efficacy of the synthetic colloid hetastarch in dogs with hypoalbuminemia. Individual doses of hetastarch ranged from 9 to 27 mL/kg, and multiple doses were used frequently. Total doses ranged from 9 to 59 mL/kg. Colloid oncotic pressure was measured in 13 dogs before and after treatment. Mean colloid oncotic pressure ± SD was 9.32 ± 2.35 mm Hg before treatment and 16.41 ±1.61 mm Hg in 8 healthy pet dogs used as controls. The difference in these values was significant ( P < .001). There was a significant increase in mean colloid oncotic pressure after the first dose of hetastarch, but there was no relationship between the dose of hetastarch and the magnitude of increase in colloid oncotic pressure. Peripheral edema or body cavity transudates resolved or decreased in 83% of the dogs despite concurrent use of crystalloid fluid therapy. There was also no relationship between the dose of hetastarch and resolution of edema. Worsening of the results from coagulograms occurred in 5 of 18 dogs, and included increased prothrombin time (n = 1), increased partial thromboplastin time (n = 5), and decreased platelet count (n = 3). Bleeding that occurred in 3 dogs could not be directly attributed to the hetastarch. There was no relationship between the dose of hetastarch and worsening of the values in the coagulograms.     

Cardiovascular and respiratory effects of propofol administration in hypovolemic dogs.

Cardiopulmonary effects of propofol were studied in hypovolemic dogs from completion of, until 1 hour after administration. 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, 6 mg of propofol/kg of body weight was administered IV to 7 dogs, and cardiopulmonary effects were measured. After blood withdrawal and prior to propofol administration, oxygen utilization ratio increased, whereas mean arterial pressure, mean pulmonary arterial pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index, oxygen delivery, mixed venous oxygen tension, and mixed venous oxygen content decreased from baseline. Three minutes after propofol administration, mean pulmonary arterial pressure, pulmonary vascular resistance, oxygen utilization ratio, venous admixture, and arterial and mixed venous carbon dioxide tensions increased, whereas mean arterial pressure, arterial oxygen tension, mixed venous oxygen content, arterial and mixed venous pH decreased from values measured prior to propofol administration. Fifteen minutes after propofol administration, mixed venous carbon dioxide tension was still increased; however by 30 minutes after propofol administration, all measurements had returned to values similar to those measured prior to propofol administration.     

Effect of weight loading on the coronary band interstitial fluid pressure in horses

Interstitial fluid pressures, as a possible function of limb load, were measured at 2 sites within the digital coronary dermis of both cranial digits in 10 standing horses. Fluid pressure changes and digital load measurements were simultaneously detected and recorded by use of, respectively, modified wick-in-needle and force plate transducers coupled to a microcomputer. Mean pressures, recorded at limb loads between 50 and 80 kg, were 2.29 +/- 3.17 mm of Hg at the toe and 2.49 +/- 5.91 mm of Hg at the heel. Mean pressures, recorded between 150 and 180 kg, were 5.01 +/- 5.23 mm of Hg at the toe and 1.28 +/- 7.69 mm of Hg at the heel. These data indicate that, in the static limb, no statistically significant change in interstitial fluid pressure occurs at loads up to 180 kg.     

Colloid Osmotic Pressure of Parenteral Nutrition Components and Intravenous Fluids

Objective: Parenteral nutrition is an important part of therapy for critically ill animals that cannot tolerate enteral feedings. It has been hypothesized that parenteral nutrition might also play a role in increasing colloid osmotic pressure (COP). The purpose of this study was to measure COP of various parenteral nutrition components and compare them to the COP of commonly used intravenous solutions.
Design: Membrane colloid osmometry was used to measure the COP of parenteral nutrition components (lipids, Abstractamino acids, dextrose solutions) and of synthetic colloids, crystalloids, and blood products.
Main Results: Parenteral nutrition components and all crystalloid solutions had COP measurements < 1 mm Hg. Great variation in COP was found in the different artificial colloids and blood products. The COP of the artificial colloids tested ranged from 32.7 ± 0.2 mm Hg for hetastarch to 61.7 ± 0.5 mm Hg for dextran 70.
Conclusions: The results of this in vitro study suggest that parenteral nutrition does not directly contribute to an increase in oncotic pressure. Further studies are needed to determine whether parenteral nutrition may indirectly influence COP in vivo. Knowing the COP of a fluid, along with its other properties, is useful in making appropriate therapeutic decisions.     

Intramedullary pressure in canine long bones

Intramedullary pressure was measured bilaterally in 36 dogs: in the diaphysis and distal metaphysis of the femur, in the proximal metaphysis of the tibia and humerus, and in the diaphysis of the radius. Pressure measurements were repeated in 5 dogs, 14 days after the initial recordings. Mean (+/- SD) pressures in the femoral diaphysis and distal metaphysis were 27.6 (+/- 15.4) mm of Hg and 17.6 (+/- 10.5) mm of Hg, respectively. Mean (+/- SD) pressures in the tibial diaphysis and proximal metaphysis were 26.4 (+/- 13.0) mm of Hg and 17.9 (+/- 11.8) mm of Hg, respectively. Mean (+/- SD) pressures in the humeral diaphysis and proximal metaphysis were 26.2 (+/- 15.8) mm of Hg and 13.4 (+/- 7.7) mm of Hg, respectively. The mean (+/- SD) pressure in the radial diaphysis was 15.4 (+/- 18.9) mm of Hg. Metaphyseal pressure was significantly (P less than 0.05) lower than diaphyseal pressure. Repeated pressure measurements in 5 dogs did not vary significantly from initial values, suggesting that the wide range of pressure was real not artifactual.     

Cardiopulmonary effects of intrathoracic insufflation in dogs

This study was designed to quantify the effects of incremental positive insufflation of the intrathoracic space on cardiac output (CO), heart rate (HR), arterial pressure (AP), central venous pressure (CVP), and percent saturation of hemoglobin with oxygen (SPO2) in anesthetized dogs. Seven healthy, adult dogs from terminal teaching laboratories were maintained under anesthesia with isoflurane delivered with a mechanical ventilator. The experimental variables were recorded before introduction of an intrathoracic catheter, at intrathoracic pressures (IP) of 0 mm Hg, 3 mm Hg insufflation, and additional increments of 1 mm Hg insufflation thereafter until the SPO2 remained <85% despite increases in minute volume. Finally the variables were measured again at 0 mm Hg IP. The cardiac output and systolic and diastolic AP significantly (P < 0.05) decreased at 3 mm Hg IP. Significant decreases in SPO2 were seen at 10 mm Hg IP. Significant increase in CVP was noted at 6 mm Hg IP. Heart rate decreased significantly at 5 to 6 mm Hg IP but was not decreased above 6 mm Hg IP. Given the degree of CO decrease at low intrathoracic pressures, insufflation-aided thoracoscopy should be used with caution and at the lowest possible insufflation pressure. Standard anesthetic monitoring variables such as HR and AP measurements may not accurately reflect the animal's cardiovascular status.     

Acute hemodynamic effects of hydralazine in dogs with chronic mitral regurgitation

The hemodynamic response to hydralazine administration was evaluated in 6 conscious small dogs with chronic mitral regurgitation. All dogs underwent invasive and noninvasive hemodynamic monitoring before and after hydralazine administration. Cardiac output and pulmonary capillary wedge pressure were measured with a Swan-Ganz thermodilution catheter. Systemic arterial blood pressure (AP) was measured directly by inserting a needle into the femoral artery. Standard M-mode echocardiograms and thoracic radiographs were obtained. Other hemodynamic variables were calculated. Base-line hemodynamic variables were altered severely in all dogs. Hydralazine decreased mean arterial blood pressure from 104 +/- 18 (mean +/- SD) to 78 +/- 12 mm of Hg (P less than 0.005), total systemic resistance index from 2,946 +/- 625 to 1,261 +/- 420 dynes-s-cm-5m2 (P less than 0.005), and pulmonary capillary wedge pressure from 40 +/- 5 to 26 +/- 3 mm of Hg, (P less than 0.005). Cardiac index increased from 2.92 +/- 0.72 to 5.36 +/- 1.67 L/min/m2 of body surface area (P less than 0.005). Mixed venous oxygen tension (PvO2) increased from 28.4 +/- 4.3 to 41.2 +/- 5.2 mm of Hg (P less than 0.001). Pulmonary edema resolved, as determined on thoracic radiographs. Mixed venous oxygen tension correlated well with the cardiac index (r = 0.92; P less than 0.001). It was concluded that hydralazine administration caused a small decrease in end diastolic diameter (4.8 +/- 0.9 to 4.5 +/- 0.8 cm, P less than 0.05) and end systolic diameter (2.6 +/- 0.8 to 2.3 +/- 0.7 cm, P less than 0.05). Fractional shortening and heart rate did not change.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypertension in Cats With Chronic Renal Failure or Hyperthyroidism

The Doppler ultrasonic recording technique was used to measure systolic and diastolic blood pressures indirectly in 28 cats with naturally occurring renal failure, 39 cats with hyperthyroidism, and 33 clinically normal cats. The mean systolic and diastolic blood pressures in the normal cats were 118.4 +/- 10.6 mm Hg and 83.8 +/- 12.2 mm Hg, respectively. In the cats with chronic renal failure, both the systolic (146.6 +/- 25.4 mm Hg) and diastolic (96.6 +/- 15.2 mm Hg) blood pressures were significantly higher (P less than 0.0001 and P less than 0.01, respectively) than in the normal cats. Elevations in systolic and/or diastolic blood pressure were recorded in 17 (61%) of the 28 cats with chronic renal failure. In the 39 untreated hyperthyroid cats, both the mean systolic (167.9 +/- 28.9 mm Hg) and diastolic (111.6 +/- 21.5 mm Hg) pressures also were significantly higher (P less than 0.0001) than normal. Increased systolic and/or diastolic blood pressure was recorded in 34 (87%) of the 39 hyperthyroid cats. In seven cats with hyperthyroidism that were reevaluated two to four months after successful treatment of the hyperthyroid state, there was a significant fall in mean systolic pressure (P less than 0.05) from a pretreatment value of 159.5 +/- 15.4 mm Hg to a posttreatment value of 132.0 +/- 1.62 mm Hg. Overall, the results of this study indicate that mild to moderate hypertension is common in cats with chronic renal failure and in cats with untreated hyperthyroidism. In addition, the hypertension appears to be reversible following successful treatment of the hyperthyroid state.     

The Cardiopulmonary Effects of Oxymorphone in Hypovolemic Dogs

Blood was withdrawn from 15 dogs over the course of about 1 hour until the mean arterial blood pressure was reduced to 60 mm Hg. Small aliquots of additional blood were withdrawn in order to maintain the mean arterial blood pressure near 60 mm Hg for an additional hour. Oxymorphone (0.4 mg/kg) was then administered intravenously to ten dogs, and all measurements were repeated in 5, 15, 30, and 60 minutes. Five dogs served as controls.
Heart rate, tidal volume, arterial oxygen, oxygen extraction, and pH significantly decreased after oxymorphone administration, while systemic and pulmonary arterial blood pressures, systemic vascular resistance (transiently), breathing rate, minute ventilation, physiologic dead space, venous admixture, venous oxygen, arterial and venous carbon dioxide, and bicarbonate concentration increased significantly. Cardiac output was also increased, but the change was not statistically significant. Oxymorphone was associated with significantly lower heart rate, tidal volume, arterial oxygen, and pH, and higher systemic and pulmonary arterial pressure, cardiac output, venous oxygen, and arterial and venous carbon dioxide, compared to the control group, which did not receive oxymorphone.
Oxymorphone significantly improved cardiovascular performance and tissue perfusion in these hypovolemic dogs. Oxymorphone did cause a significant increase in arterial carbon dioxide and a decrease in arterial oxygenation. Oxymorphone is an opioid agonist that may represent a reasonable alternative for the induction of anesthesia in patients who are candidates for induction hypotension.     

Indirect arterial blood pressure measurement in nonsedated Irish wolfhounds: reference values for the breed

Arterial blood pressure measurements were obtained from 158 healthy Irish wolfhounds using the oscillometric technique to establish reference values for the breed. In contrast to other sight hounds, Irish wolfhounds have low arterial blood pressure. Mean systolic pressure for the group was 116.0 mm Hg. Mean diastolic pressure was 69.2 mm Hg, and the mean value for mean arterial pressure was 87.8 mm Hg. Blood pressure measurements were higher in older wolfhounds than in young dogs. There was no difference between systolic and mean arterial blood pressures in lateral recumbency compared to standing position. However, diastolic pressure was slightly lower when standing. Calm dogs had lower pressure than anxious wolfhounds. There was a significant interaction between the effects of age, gender, and mood on systolic, diastolic, and mean arterial blood pressure values.     

Blood pressure changes in dogs with babesiosis

Systemic arterial blood pressures were measured in 30 dogs with acute babesiosis, 10 each with mild uncomplicated, severe uncomplicated and complicated disease. Ten healthy dogs were used as controls. Hypotension was defined as more than 3 standard deviations below the control mean. Normal mean pressures (+/-SD) were: systolic arterial pressure 151 (+/-11) mm Hg, diastolic arterial pressure 89 (+/-8) mm Hg and mean arterial pressure 107 (+/-10) mm Hg. Hypotension was the most frequent abnormality, and increased strikingly in incidence as disease severity increased, with 5/10 dogs in the complicated group being hypotensive for systolic, diastolic and mean arterial pressures, compared with 2/10 in the severe uncomplicated group and 0/10 in the mild uncomplicated group. Systolic, diastolic and mean arterial pressures in the complicated group and severe uncomplicated group, and systolic pressure in the mild uncomplicated group, were significantly lower than in the controls. There were no significant relationships between arterial pressures and age, pulse rate, respiratory rate, temperature, mucous membrane colour or haematocrit. There was a significant negative correlation between arterial pressures and white cell and immature neutrophil counts. Arterial pressures differed significantly between dogs that were clinically collapsed and those that were not, but not between survivors and non-survivors. Pulse pressure (systolic-diastolic) was low in 7/10 complicated, 1/10 mild uncomplicated, and 1/10 severe uncomplicated cases, and differed significantly between the complicated and control groups. The high incidence of hypotension in clinically severe babesiosis has important implications for therapy.     

Clinical comparison of three methods to measure blood pressure in nonsedated dogs

OBJECTIVE: To determine arterial blood pressure in client-owned dogs, using direct arterial puncture, oscillometry, and Doppler ultrasonography in a clinical setting. DESIGN: Prospective study. ANIMALS: 8 clinically normal client-owned dogs. PROCEDURE: Blood pressures of nonsedated dogs were measured simultaneously, using each of the 3 methods. Mean values obtained were compared with published mean values. Ability of noninvasive methods (Doppler ultrasonography and oscillometry) to accurately predict results of the invasive method, and relationships between blood pressure and age, body weight, and degree of patient anxiety were determined. RESULTS: Calculated ranges of values (mean +/- 2 SD) determined by direct arterial puncture were: systolic pressure, 114 to 194 mm Hg; diastolic pressure, 66 to 102 mm Hg; and mean pressure, 85 to 129 mm Hg. Ranges determined by use of oscillometry were: systolic, 110 to 190 mm Hg; diastolic, 35 to 107 mm Hg; and mean, 78 to 138 mm Hg. Ultrasonographic and oscillometric values did not accurately predict direct values, but mean values of systolic and mean pressures were similar among methods. Relationships were not detected between age or body weight and blood pressure. Significant differences in blood pressure were not detected between anxious and nonanxious dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Mean values of systolic, diastolic, and mean arterial blood pressure measured in nonsedated client-owned dogs, using invasive and noninvasive methods in a clinical setting, are comparable with those determined for acclimatized, trained, or sedated dogs. However, results of noninvasive methods may not accurately reflect direct values.