A relation exists between colloid osmotic pressure and serum total protein concentration; equations describing this relation have been used to determine a calculated value for colloid osmotic pressure. However, the relation between total protein concentration and colloid osmotic pressure is altered by the method used to measure protein and by changes in the ratio of concentrations of albumin (A) to globulin (G). We developed nomograms for estimating colloid osmotic pressure from A and G concentrations, using samples obtained from clinically normal animals and compared the accuracy of these nomograms with that of previously described equations relating colloid osmotic pressure to total protein concentration. For comparison, serum samples from canine (n = 106), equine (n = 79), feline (n = 24), and bovine (n = 27) patients admitted to the University of Georgia Veterinary Medical Teaching Hospital were used. Results indicated that nomograms based on protein concentration estimated by a refractometer generally were the least reliable. Although predictive nomograms, using total protein concentration determined by the biuret method, provided better results for serum samples, there was considerable variation between measured and calculated values for colloid osmotic pressure in all species studied. Calculated values for colloid osmotic pressure derived from A and G concentrations were most closely related to measured values for colloid osmotic pressure in dogs, horses, and cats. However, calculated values for colloid osmotic pressure differed from measured values by as much as 5 mm of Hg for some samples by each of the methods of estimation. These results indicate that, although calculated values for colloid osmotic pressure may be most accurate when variations in the A-to-G ratio are accounted for in the nomogram, none of the calculation methods provided a consistently accurate estimate of colloid osmotic pressure.

The objective of this study was to determine the effects of the administration of a high volume of isotonic crystalloid at a rapid rate on cardiovascular function in normovolemic, isoflurane-anesthetized dogs during induced hypotension. Using a prospective study, 6 adult dogs were induced to general anesthesia and cardiovascular and hematological values were measured while the dogs were maintained at 3 hemodynamic states: first during light anesthesia with 1.3% end-tidal isoflurane (ETI); then during a hypotensive state induced by deep anesthesia with 3% ETI for 45 min while administered 1 mL/kg body weight (BW) per minute of isotonic fluids; and then decreased to 1.6% ETI while receiving 1 mL/kg BW per minute of fluids for 15 min. End-tidal isoflurane (ETI) at 3.0 ± 0.2% decreased arterial blood pressure (ABP), cardiac index (CI), and stroke volume index (SVI), and increased stroke volume variation (SVV) and central venous pressure (CVP). Fluid administration during 3% ETI decreased only SVV and systemic vascular resistance index (SVRI), while CVP increased progressively. Decreasing ETI to 1.6 ± 0.1% returned ABP and SVI to baseline (ETI 1.3 ± 0.1%), while CI and heart rate increased and SVV decreased. There was significant progressive clinical hemodilution of hemoglobin (Hb), packed cell volume (PCV), total protein (TP), colloid osmotic pressure (COP), arterial oxygen content (CaO2), and central-venous oxygen content (CcvO2). High-volume, rapid-rate administration of an isotonic crystalloid was ineffective in counteracting isoflurane-induced hypotension in normovolemic dogs at a deep plane of anesthesia. Cardiovascular function improved only when anesthetic depth was reduced. Excessive hemodilution and its adverse consequences should be considered when a high volume of crystalloid is administered at a rapid rate.

Indices of renal function and damage were measured in 12 healthy male adult llamas fed a diet of mixed alfalfa/grass hay (mixed hay) and water ad libitum. Using a collection bag fitted over the preputial area, urine samples were collected at 6, 12, and 24 hours. Serum samples were obtained concurrently to determine endogenous creatinine clearance (CL), total (TE) and fractional excretion (FE) of electrolytes (Na, K, Cl, P), electrolyte CL, urine and serum osmolality, urine enzyme activities (gamma-glutamyltransferase and N-acetyl-beta-D-glucosaminidase), and urine protein concentration. Urine production was quantified. Three months later, 10 of the 12 llamas were fed a grass hay diet and water ad libitum. Similar samples were obtained, and similar measurements were made. Urine production was higher when the llamas were fed the mixed hay diet. Total urine volume for llamas fed mixed hay ranged from 628 to 1,760 ml/24 h, with a median of 1,307.5 ml/24 h, compared with a range of 620 to 1,380 ml/24 h and a median of 927.50 ml/24 h for llamas fed grass hay. Median urine osmolality was higher in llamas fed mixed hay (1,906 mOsm/kg of body weight, with a range of 1,237 to 2,529 mOsm/kg), compared with llamas fed grass hay (1,666 mOsm/kg with a range of 1,163 to 2,044 mOsm/kg). Creatinine CL did not vary significantly over time for either diet. Median creatinine CL was higher for llamas fed mixed hay, compared with llamas fed grass hay--0.78 ml/min/kg with a range of 0.20 to 1.83 ml/min/kg vs 0.45 ml/min/kg with a range of 0.13 to 3.17 ml/min/kg. Clearances for K and Cl varied significantly among the periods. However, median CL for Na and P did not vary over time for either diet. Overall values for these electrolytes in llamas fed mixed hay and grass hay diets were: CL(Na), 0.001 and 0.002 ml/min/kg and CL(P), 0.0006 and 0.0004 ml/min/kg respectively. The FE rates of K, Cl, and P did not vary significantly over time for either diet. Median respective FE for these electrolytes in the llamas fed mixed hay and grass hay diets include: FE(K), 84.90 and 63.10%; FE(Cl), 0.85 and 1.30%; and FE(P), 0.10 and 0.10%. Fractional excretion of Na varied over time for both diets and could not be expressed accurately as an overall median. Median respective TE of electrolytes for llamas fed the mixed hay and grass hay diets were: TE(Na), 0.007 and 0.03 mEq/kg/h; TE(Cl), 0.04 and 0.06 mEq/kg/h; and TE(P), 0.0002 and 0.00 mg/kg/h; TE(K) varied significantly (P < 0.05) over time for both diets. Urine gamma-glutamyltransferase activity changed significantly (P < 0.05) over time. Urine N-acetyl-beta-D-glucosaminidase activity was influenced by an interaction between diet and time. Median urine protein concentration was 26.0 mg/dl, with a range of 11.0 to 73.0 mg/dl for llamas fed mixed hay, and was 28.0 mg/dl, with a range of 16.0 to 124.0 mg/dl for llamas fed grass hay.

Cerebrospinal fluid and serum were obtained from 17 adult, healthy llamas (9 males, 1 castrated male, and 7 females). Osmolality; activities of lactate dehydrogenase and creatine kinase; and concentrations of glucose, sodium, chloride, potassium, total protein, and albumin were determined in serum and CSF. Total and differential cell counts were determined in CSF, and electrophoresis of CSF proteins was performed. Total nucleated cell count was low, 0 to 3/microliter, which is lower than that reported for other domestic species and is similar to values in healthy people. Differential leukocyte percentages were disparate depending on the degree of blood contamination. Blood contamination influenced the percentage of neutrophils and eosinophils in CSF. Samples with few erythrocytes had differential leukocyte distribution similar to that of other species: mostly lymphocytes, fewer monocytoid cells, and scant neutrophils. Older llamas had a few eosinophils in the CSF. Total protein, albumin, and gamma-globulin concentrations in llamas were similar to values in cattle and were higher than values in most domestic species. Glucose concentration in CSF was approximately 40% of the value in serum (nonruminant animals and people typically have CSF glucose concentration that is approximately 60 to 80% of the serum glucose concentration). Sodium and Cl concentrations in CSF were higher than those in serum, whereas K concentration was lower in CSF, compared with serum. Activities of creatine kinase and lactate dehydrogenase in CSF were markedly lower than those in serum, and the ranges of values in this group of healthy llamas were narrow.

A relation exists between colloid osmotic pressure and serum total protein concentration; equations describing this relation have been used to determine a calculated value for colloid osmotic pressure. However, the relation between total protein concentration and colloid osmotic pressure is altered by the method used to measure protein and by changes in the ratio of concentrations of albumin (A) to globulin (G). We developed nomograms for estimating colloid osmotic pressure from A and G concentrations, using samples obtained from clinically normal animals and compared the accuracy of these nomograms with that of previously described equations relating colloid osmotic pressure to total protein concentration. For comparison, serum samples from canine (n = 106), equine (n = 79), feline (n = 24), and bovine (n = 27) patients admitted to the University of Georgia Veterinary Medical Teaching Hospital were used. Results indicated that nomograms based on protein concentration estimated by a refractometer generally were the least reliable. Although predictive nomograms, using total protein concentration determined by the biuret method, provided better results for serum samples, there was considerable variation between measured and calculated values for colloid osmotic pressure in all species studied. Calculated values for colloid osmotic pressure derived from A and G concentrations were most closely related to measured values for colloid osmotic pressure in dogs, horses, and cats. However, calculated values for colloid osmotic pressure differed from measured values by as much as 5 mm of Hg for some samples by each of the methods of estimation. These results indicate that, although calculated values for colloid osmotic pressure may be most accurate when variations in the A-to-G ratio are accounted for in the nomogram, none of the calculation methods provided a consistently accurate estimate of colloid osmotic pressure. For clinical patients, colloid osmotic pressure based on these nomograms cannot replace direct measurement.

Red blood cell populations separated by density centrifugation were compared in a dynamic assay of osmotic stress. Red blood cells from Beagles genotypically normal and nonanemic (nonaffected), Beagles with inherited hemolytic anemia (anemic), and Beagles presumed to be carriers of the anemia trait (trait carriers) were examined for rate and extent of swelling after exposure to the ionophore A23187 in a medium containing calcium and potassium chloride. Comparisons were made between RBC populations separated on the basis of density. Significant differences were observed in the rates of cell swelling in Rbc populations separated by density between nonaffected and anemic Beagles. The response of RBC from Beagles presumed to carry the anemia trait was similar to that of RBC from nonaffected dogs. One phenotypic expression of this inherited abnormality of Rbc in Beagles was an accelerated rate of RBC swelling under osmotic stress, and this swelling response diminished with increasing RBC density.

The effects of single IV injections of sodium bicarbonate (0.5 mEq/kg of body weight, 1 mEq/kg, 2 mEq/kg, and 4 mEq/kg) on serum osmolality, serum sodium, chloride, and potassium concentrations, and venous blood gas tensions in 6 healthy cats were monitored for 180 minutes. Serum osmolality increased and remained significantly (P less than 0.05) increased for 120 minutes in cats given 4 mEq of sodium bicarbonate/kg. Serum sodium was increased significantly (P less than 0.05) for 30 minutes in cats given 4 mEq of sodium bicarbonate/kg. Serum sodium decreased and remained significantly (P less than 0.05) decreased for 120 minutes in cats given 1 g of 20% mannitol/kg, and serum osmolality was significantly (P less than 0.05) decreased at 30 and 60 minutes. Serum chloride decreased significantly (P less than 0.05) for 10 minutes in cats given 1 mEq of sodium bicarbonate/kg, and was significantly decreased for 30 minutes in cats given 2 mEq and 4 mEq of sodium bicarbonate/kg. Serum chloride decreased and remained significantly (P less than 0.05) decreased for 30 minutes in cats given 1 g of 20% mannitol/kg. Serum sodium and serum osmolality did not change significantly (P less than 0.05) in cats given 4 ml of 0.9% sodium chloride/kg. Serum potassium decreased significantly (P less than 0.05) for 10 minutes in cats given 1 mEq of sodium bicarbonate/kg, and for 120 minutes in cats given 2 mEq/kg or 4 mEq/kg. There was a significantly (P less than 0.05) greater decrease in serum potassium that lasted for 30 minutes after giving sodium bicarbonate at the dosage of 4 mEq/kg, compared with other dosages given. Serum potassium did not change significantly in cats given 1 g of 20% mannitol/kg, but was significantly (P less than 0.05) decreased 10 minutes following 4 ml of 0.9% sodium chloride/kg. Sodium bicarbonate infusion significantly (P less than 0.05) increased venous blood pH and plasma bicarbonate concentration in all cats. The magnitude and duration of these changes were significantly greater following administration of sodium bicarbonate at dosages of 2 mEq/kg and 4 mEq/kg. Significant (P less than 0.05) increases in PCO2 were associated only with the highest dosage of sodium bicarbonate (4 mEq/kg). Base excess increased significantly (P less than 0.05) in all cats following sodium bicarbonate infusion. There were significantly (P less than 0.05) greater increases in base excess lasting 30 minutes following administration of sodium bicarbonate at dosages of 2 mEq/kg and 4 mEq/kg. Significant (P less than 0.05) changes in venous blood pH, PCO2, or bicarbonate were not observed in cats given 4 ml of 0.9% sodium chloride/kg, or in cats given 1 g of 20% mannitol/kg. Base excess was significantly (P less than 0.05) increased for 10 minutes in cats given 1 g of 20% mannitol/kg. As expected, 4 mEq of sodium bicarbonate/kg induced the most time- and dosage-related effects. Caution should be used when administering sodium bicarbonate IV to cats at dosages greater than 2 mEq/kg, because of the potential for important acid-base and electrolyte changes.

Renal electrolyte and net acid excretion were characterized during generation and maintenance of hypochloremic metabolic alkalosis in a ruminant model. Two phases of renal response with regard to sodium and net acid excretion were documented. An initial decrease in net acid excretion was attributable to increase in bicarbonate excretion with associated increase in sodium excretion. As the metabolic disturbance became more advanced, a second phase of renal excretion was observed in which sodium and bicarbonate excretion were markedly decreased, leading to increase in net acid excretion and development of aciduria. Throughout the metabolic disturbance, chloride excretion was markedly decreased; potassium excretion also decreased. These changes were accompanied by increase in plasma renin and aldosterone concentrations. There was apparent failure to concentrate the urine optimally during the course of the metabolic disturbance, despite increasing plasma concentration of antidiuretic hormone.

OBJECTIVE To compare the effects of equivalent volumes of equine plasma and 6% hydroxyethyl starch (600/0.75) solution (hetastarch) administered IV on plasma colloid osmotic pressure (pCOP) and commonly monitored clinicopathologic variables in horses. ANIMALS 6 healthy mares. PROCEDURES In a randomized, crossover study, horses were administered hetastarch or plasma (both 10 mL/kg, IV) 18 months apart. The pCOP and variables of interest were measured before (baseline), immediately after, and at intervals up to 96 or 120 hours after infusion. Prothrombin and activated partial thromboplastin times were measured before and at 2 and 8 hours after each infusion. RESULTS Prior to hetastarch and plasma infusions, mean ± SEM pCOP was 19.4 ± 0.5 mm Hg and 19.4 ± 0.8 mm Hg, respectively. In general, hetastarch and plasma infusions comparably increased pCOP from baseline for 48 hours, with maximum increases of 2.0 and 2.3 mm Hg, respectively. Mean Hct and hemoglobin, total protein, and albumin concentrations were decreased for a period of 72, 96, or 120 hours after hetastarch infusion with maximum decrements of 8.8%, 3.2 g/dL, 1.2 g/dL, and 0.6 g/dL, respectively. Plasma infusion decreased (albeit not always significantly) hemoglobin concentration and Hct for 20 and 24 hours (maximum changes of 1.5 g/dL and 6.6%, respectively) and increased total solids concentration (maximum change of 0.6 g/dL) for 48 hours. Platelet count and coagulation times were minimally affected. CONCLUSIONS AND CLINICAL RELEVANCE Overall, the hetastarch and plasma infusions comparably increased pCOP in healthy horses for up to 48 hours. Hetastarch induced greater, more persistent perturbations in clinicopathologic variables.