The physicochemical approach for evaluating acid-base balance in exercising horses.
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Acid-Base Equilibrium↗
Biomedical subjects
P D Constable
Publications and source records attributed to P D Constable.
Techniques for evaluation of right ventricular relaxation rate in horses and effects of inhalant anesthetics with and without intravenous administration of calcium gluconate.
OBJECTIVES: To determine the most repeatable method for evaluating right ventricular relaxation rate in horses and to determine and compare effects of isoflurane or halothane with and without the added influence of intravenously administered calcium gluconate on right ventricular relaxation rates in horses. ANIMALS: 6 Thoroughbred horses from 2 to 4 years old. PROCEDURE: 6 models (2 for monoexponential decay with zero asymptote, 3 for monoexponential decay with variable asymptote, and 1 for biexponential decay) for determining right ventricular relaxation rate were assessed in conscious and anesthetized horses. The 2 methods yielding the most repeatable results then were used to determine right ventricular relaxation rates in horses anesthetized with isoflurane or halothane before, during, and after i.v. administration of calcium gluconate. Right ventricular pressure was measured, using a catheter-tip high-fidelity pressure transducer, and results were digitized at 500 Hz from minimum rate of change in ventricular pressure. RESULTS: 2 models that used monoexponential decay with zero asymptote repeatedly produced an estimate for relaxation rate and were used to analyze effects of anesthesia and calcium gluconate administration on relaxation rate. Isoflurane and halothane each prolonged right ventricular relaxation rate, with greater prolongation evident in halothane-anesthetized horses. Calcium gluconate attenuated the anesthesia-induced prolongation in right ventricular relaxation rate, with greater response obtained in isoflurane-anesthetized horses. CONCLUSIONS AND CLINICAL RELEVANCE: Right ventricular relaxation rate in horses is assessed best by use of a monoexponential decay model with zero asymptote and nonlinear regression. Intravenous administration of calcium gluconate to isoflurane-anesthetized horses best preserves myocardial relaxant function.
Anesthetics, Inhalation↗
Hemodynamic effects of ionized calcium in horses anesthetized with halothane or isoflurane.
OBJECTIVES: To evaluate the effects of halothane and isoflurane on cardiovascular function and serum total and ionized calcium concentrations in horses, and to determine whether administration of calcium gluconate would attenuate these effects. ANIMALS: 6 clinically normal adult Thoroughbreds. PROCEDURE: Catheters were inserted for measurement of arterial blood pressures, pulmonary arterial blood pressures, right ventricular pressure (for determination of myocardial contractility), right atrial pressure, and cardiac output and for collection of arterial blood samples. Anesthesia was then induced with xylazine hydrochloride and ketamine hydrochloride and maintained with halothane or isoflurane. An i.v. infusion of calcium gluconate was begun 75 minutes after anesthetic induction; dosage of calcium gluconate was 0.1 mg/kg of body weight/min for the first 15 minutes, 0.2 mg/kg/min for the next 15 minutes, and 0.4 mg/kg/min for an additional 15 minutes. Data were collected before, during, and after administration of calcium gluconate. RESULTS: Halothane and isoflurane decreased myocardial contractility, cardiac index, and mean arterial pressure, but halothane caused greater depression than isoflurane. Calcium gluconate attenuated the anesthetic-induced depression in cardiac index, stroke index, and maximal rate of increase in right ventricular pressure when horses were anesthetized with isoflurane. When horses were anesthetized with halothane, a higher dosage of calcium gluconate was required to attenuate the depression in stroke index and maximal rate of increase in right ventricular pressure; cardiac index was not changed with calcium administration. CONCLUSIONS AND CLINICAL RELEVANCE: I.v. administration of calcium gluconate may support myocardial function in horses anesthetized with isoflurane.
Anesthesia, Inhalation↗
Sequence of cardiovascular changes leading to pulmonary edema in swine fed culture material containing fumonisin.
OBJECTIVES: To determine the sequence of cardiovascular and blood gas changes induced by ingestion of fumonisin-containing culture material in swine and to examine the temporal relationship of these changes to plasma sphinganine and sphingosine concentrations. ANIMALS: 12 healthy castrated pigs (38 to 50 kg). PROCEDURE: Pigs were instrumented to permit cardiovascular monitoring and collection of blood samples. Baseline values were obtained, and pigs were randomly assigned to 1 of 2 groups. Control pigs (n = 6) were fed a standard grower diet, whereas culture material that contained 20 mg of fumonisin B1/kg of body weight was added to the feed of treated pigs (n = 6) each day. Hemodynamic data, results of arterial and mixed venous blood gas analyses, and plasma sphinganine and sphingosine concentrations were recorded every 12 hours until treated pigs were euthanatized because of impending death from pulmonary edema. RESULTS: Sphinganine and sphingosine concentrations were increased in plasma of treated pigs within 24 hours of initial fumonisin exposure and continued to increase dramatically until euthanasia. Fumonisin-treated pigs had increased respiratory rate, mean pulmonary artery pressure, and pulmonary artery wedge pressure, along with decreased heart rate and cardiac output in the 12-hour period before euthanasia. Fumonisin-treated pigs also had systemic arterial hypotension, arterial and mixed venous hypoxemia, metabolic acidosis, decreased oxygen delivery, and increased oxygen consumption immediately before euthanasia. CONCLUSIONS AND CLINICAL RELEVANCE: Fumonisin-induced pulmonary edema in swine is probably caused by acute left-sided heart failure. Onset of hemodynamic changes was associated with plasma sphinganine concentration > or = 2.2 microM/L and plasma sphingosine concentration > or = 1 microM/L.
Animal Feed↗
Hemodynamic effects of thyroidectomy in sedentary horses.
OBJECTIVE: To investigate hemodynamic effects of thyroidectomy in horses at rest. ANIMALS: 6 healthy aged Quarter Horse mares. PROCEDURE: Horses were monitored for 5 months before and 4 weeks after thyroidectomy and for an additional 4 weeks after administration of thyroid hormone supplement (2.5 microg of thyroxine/kg of body weight, PO, q 12 h, and 0.6 microg of triiodothyronine/kg, PO, q 12 h). Responses to thyroid-stimulating hormone (TSH) were measured before and 4 weeks after thyroidectomy. Other variables monitored daily were resting rectal temperature (T), heart rate (HR), respiratory rate (RR), and body weight (BW). Monthly cardiac output (Q), blood volume (BV), plasma volume (PV), standard electrocardiographic measures, systolic and right ventricular blood pressure, and HR responses were determined after IV administration of isoproterenol and phenylephrine. Variables were analyzed by use of repeated-measures ANOVA. RESULTS: Complete thyroidectomy was confirmed by minimal response to TSH 4 weeks after surgery. Resting HR, RR, T, Q, and beta-adrenergic responsiveness to isoproterenol decreased significantly after thyroidectomy. Resting T, Q, and beta-adrenergic responsiveness increased after administration of supplement and was not significantly different from euthyroid values. Blood volume and PV increased significantly after thyroidectomy but did not return to euthyroid values despite administration of supplement. Response to phenylephrine was minimally different between treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Thyroidectomy in horses caused decreased resting HR, RR, T, Q, and isoproterenol responsiveness and increased BV, PV, PQ interval, and QT interval corrected for HR. Some of these surgically induced changes appeared to be partially reversed by administration of thyroid hormone supplement.
Adrenergic alpha-Agonists↗
Characteristics of dairy cows during episodes of bacteriologically negative clinical mastitis or mastitis caused by Corynebacterium spp.
OBJECTIVES: To use clinical and lactational characteristics to determine whether bacteriologically negative (BN) clinical mastitis episodes are more apt to be caused by gram-negative or gram-positive bacteria, and to investigate severity of clinical mastitis caused by Corynebacterium spp (COR). DESIGN: Case series. SAMPLE POPULATION: 300 clinical mastitis episodes affecting 123 dairy cows vaccinated against lipopolysaccharide core antigens. PROCEDURE: Cows were examined at onset of clinical mastitis, and 23 characteristics, including rectal temperature, heart rate, rumen contraction rate, degree of dehydration, udder and milk characteristics, lactation number, stage of lactation, and season of year, were recorded. Milk production and milk constituent concentrations before onset of mastitis were obtained from herd records. Values for cows with BN milk were compared with values for cows from which milk yielded gram-negative bacteria (GNB) or gram-positive cocci (GPC); logistic regression was used to predict which pathogen type was causing BN mastitis. Characteristics for cows from which milk yielded COR were compared with those of cows from which milk was BN or yielded GPC. RESULTS: BN clinical mastitis episodes differed significantly from episodes caused by GPC, and were similar to, but milder than, episodes caused by GNB. COR were isolated in a substantial proportion of mastitis episodes, but clinical signs were milder than when GPC were isolated. CLINICAL IMPLICATIONS: Most BN mastitis episodes in cows receiving lipopolysaccharide core antigen vaccines appear to be caused by low-grade infection with GNB, and treatment and management decisions should be made accordingly. The COR may be economically important clinical mastitis pathogens in some herds.
Animals↗
Comparison of hypertonic saline-dextran solution and lactated Ringer's solution for resuscitating severely dehydrated calves with diarrhea.
OBJECTIVE: To determine effectiveness of rapid i.v. administration of hypertonic saline-dextran (HSD) solution combined with oral administration of isotonic electrolyte solution for resuscitating severely dehydrated calves and to compare the resuscitative response with that of a conventional treatment of lactated Ringer's solution (LRS) i.v. and orally administered isotonic electrolyte solution. DESIGN: Prospective study. ANIMALS: 15 male dairy calves 3 to 10 days old. PROCEDURE: Baseline data were obtained. Osmotic diarrhea and severe dehydration were induced for 48 hours. Calves were then allocated to 3 treatment groups. The control group (group C) did not receive fluids, a second group (group H) received hypertonic saline (7.2% NaCl) solution with 6% dextran 70 and isotonic electrolyte solution, and a third group (group L) received LRS and isotonic electrolyte solution. Physical examinations were performed every 8 hours. RESULTS: Calves developed diarrhea, lethargy, severe dehydration (mean, 14% of body weight), azotemia, hyperkalemia, and mild acidemia. Group-C calves remained lethargic and severely dehydrated during the 24-hour treatment phase. Calves treated with HSD and LRS were effectively resuscitated; however, response for most variables was more rapid and sustained for the HSD-treated group. Cardiac output was greater in LRS- than HSD-treated calves 1, 2, and 8 hours after initiation of treatment because of continued i.v. administration of fluids. CLINICAL IMPLICATIONS: A combination of HSD and isotonic electrolyte solution was a rapid and effective method for resuscitation of severely dehydrated calves. It was similar in effectiveness to conventional treatment in which LRS and isotonic electrolyte solution were used for resuscitating calves with severe dehydration.
Administration, Oral↗
Use of clinical parameters for differentiation of gram-positive and gram-negative mastitis in dairy cows vaccinated against lipopolysaccharide core antigens.
OBJECTIVE: To determine whether clinical parameters could be used to differentiate clinical mastitis (CM) caused by gram-positive bacteria from CM caused by gram-negative bacteria in dairy cows vaccinated against lipopolysaccharide core antigens. DESIGN: Case series. ANIMALS: 143 episodes of CM in 86 dairy cows in a single herd. PROCEDURE: Cows were examined at onset of CM, and 24 clinical parameters including rectal temperature, heart rate, rumen contraction rate, degree of dehydration, various udder and milk characteristics, lactation number, stage of lactation, and season of year were recorded. Milk production and milk constituent concentrations before onset of CM were obtained from Dairy Herd Improvement Association records. Values for cows with gram-negative CM were compared with values for cows with gram-positive CM. Logistic regression was used to identify important predictors of gram-negative CM. RESULTS: 64 (45%) CM episodes were caused by gram-negative bacteria and 79 (55%) were caused by gram-positive bacteria. Rumen contraction rate was significantly lower and milk protein percentage before onset of CM was significantly higher in cows with gram-negative, rather than gram-positive, CM. Logistic regression indicated that CM was more likely to have been caused by gram-negative bacteria if it developed during the summer, milk was watery, or rumen contraction rate was low. Sensitivity and specificity of the final regression model were 0.58 and 0.80, respectively. Predictive value of a positive result was 0.74 when proportion of CM episodes caused by gram-negative bacteria was assumed to be 50%. CLINICAL IMPLICATIONS: Results suggest that clinical observations do not allow accurate prediction of CM pathogens and should not be the sole criteria for deciding whether cows with CM are treated with antibiotics.
Animals↗
Clinical and laboratory assessment of hydration status of neonatal calves with diarrhea.
OBJECTIVE: To develop accurate, objective guidelines for assessing hydration status of neonatal calves with diarrhea. DESIGN: Prospective study. ANIMALS: 15 male dairy calves 3 to 10 days old. PROCEDURE: Dehydration and diarrhea were induced by administration of diuretic agents (i.e., furosemide, spironolactone, hydrochlorothiazide) and sucrose solution. Linear regression was used to examine the relationship between potentially useful factors for evaluating hydration status (extent of enophthalmos; skin-tent duration on neck, thorax, and upper and lower eyelids; heart rate; mean central venous pressure; peripheral [extremity] and core [rectal] temperatures; core-peripheral [rectal-extremity] temperature difference; PCV; and hemoglobin and plasma protein concentrations) and degree of dehydration, as determined by change in body weight. RESULTS: Best predictors of degree of dehydration were extent of enophthalmos, skin elasticity on neck and thorax, and plasma protein concentration. CLINICAL IMPLICATIONS: These experimentally determined guidelines provide practitioners with a simple, inexpensive, and practical method for evaluating hydration status of neonatal calves with diarrhea.
Animals↗
Effect of endurance training on cardiac morphology in Alaskan sled dogs.
The cardiac morphology of 77 conscious Alaskan sled dogs before and after 5 mo of endurance training (20 km/day team pulling a sled and musher) was studied using two-dimensional and M-mode echocardiography. Subgroups included dogs with at least one season of previous training ("veterans") and dogs undergoing their first season of training ("rookies"). Training resulted in a significant (P < 0.05) decrease in resting heart rate (-15%) and significant increases in interventricular septal thickness (systole, 15%; diastole, 13%), left ventricular (LV) internal dimension in diastole (LVIDd, 4%), LV free wall thickness in systole (9%) and diastole (LVWd, 9%), and left atrial diameter (5%) in all dogs, but the increase in LVWd was greater in rookies (16%) than in veterans (7%). Training increased end-diastolic volume index (8%), LV mass index (24%), and heart weight index (24%) and decreased the LVIDd-to-LVWd ratio (-6%) but did not alter cardiac index. We conclude that increased LV mass attributable to LV dilation and hypertrophy is associated with endurance training in Alaskan sled dogs. Disproportionate LV wall thickening accompanying LV dilation suggests that cardiac morphological changes are due to volume and pressure loading. These training-induced changes are similar to those documented in human athletes undergoing combined isometric and isotonic training and differ from studies of dogs trained on treadmills.
Alaska↗
Effects of mastitis on the volume and composition of colostrum produced by Holstein cows.
The effects of mastitis during the late nonlactating period on colostral volume and concentrations and total yields of immunoglobulin (Ig) G1, fat, and protein in colostrum were investigated using matched pairs of mammary glands from multiparous Holstein cows. Samples of mammary secretions were collected at approximately 14 and 7 d prepartum and within 3 h after calving. At each sampling time, the glands and secretions were examined for gross abnormalities, and the California Mastitis Test was performed. Duplicate secretion samples from each gland were cultured, and somatic cell count, pH, and fat and protein concentrations were determined. The volume of colostrum obtained at the first milking of each gland was quantified using a quarter milking device, and its IgG1 concentration was measured. Colostral volume from persistently infected mammary glands was lower than that from matched uninfected glands, as was the total mass of IgG1. However, infection did not alter IgG1 concentration in colostrum. Fat and protein percentages were lower in prepartum secretions but not in colostrum from infected glands. Persistent infection was associated with increased somatic cell count and pH of secretions at all sampling times, and California Mastitis Test scores were higher for colostrum from infected glands. The appearance of secretions was extremely variable, but the presence of flakes or clots in colostrum was associated with infection. We concluded that mastitis during the late nonlactating period alters mammary gland function but is unlikely to be an important contributor to the high rate of failure of passive transfer of immunoglobulins in calves.
Animals↗
Use of peripheral temperature and core-peripheral temperature difference to predict cardiac output in dehydrated calves housed in a thermoneutral environment.
OBJECTIVE: To investigate the relation between cardiac output (CO) and peripheral (fetlock) temperature (PT) and core-peripheral (rectal-fetlock) temperature difference (CPTD) in dehydrated calves housed in a thermoneutral environment. ANIMALS: 28 male dairy calves 3 to 10 days old. PROCEDURE: Severe dehydration and watery diarrhea were induced by administering diuretics (furosemide, hydrohlorothiazide, spironolactone) and sucrose solution. Cardiac output was measured by means of thermodilution, core temperature was determined by placing a digital thermometer in the rectum, and PT was measured by taping a thermistor to the left hind fetlock and insulating the thermistor from ambient air. RESULTS: In thermoneutral ambient temperatures (10 to 24 C), PT and CPTD were constant and independent of CO at normal or high CO values but were linearly dependent on CO below a critical value (78% of normal CO output). Regression equations were developed that predicted CO from measured PT or CPTD. At ambient temperatures below the lower critical temperature for neonatal calves (8 to 10 C), normal values for PT and CPTD in healthy calves were significantly different from those at thermoneutral ambient temperatures. CONCLUSIONS AND CLINICAL RELEVANCE: Peripheral temperature and CPTD are practical, noninvasive, and inexpensive but only moderately useful methods for predicting CO in hemodynamically stable calves housed in a thermoneutral environment. Thus, these parameters are of some value in daily monitoring of the response to treatment and in determining need for i.v. fluid administration in dehydrated calves housed at a dry still-air temperature of 10 to 24 C but are of minimal to no value in calves housed at < 10 C.
Animals↗
Comparison of anion gap and strong ion gap as predictors of unmeasured strong ion concentration in plasma and serum from horses.
OBJECTIVE: To compare the accuracy of anion gap (AG) and strong ion gap (SIG) for predicting unmeasured strong ion concentration in plasma and serum from horses. ANIMALS: 6 well-trained Standardbred horses undergoing high-intensity exercise (experimental study) and 78 horses and ponies that underwent i.v. administration of lactic acid or endotoxin, and endurance, submaximal, or high-intensity exercise. PROCEDURE: Anion gap was calculated as AG = (Na+ + K+) - (Cl- + HCO3-), and SIG was calculated, using the simplified strong ion model, whereby SIG (mEq/L) = 2.24 x total protein (g/dl)/(1 + 10(6.65-pH)) - AG. The relation between AG or SIG and plasma lactate concentration was evaluated, using linear regression analysis. RESULTS: Linear relations between plasma lactate concentration and AG and SIG were strong for the experimental study (r2 = 0.960 and 0.966, respectively) and the published studies (r2 = 0.914 and 0.925, respectively). The following relations were derived: AG = 1.00 x plasma lactate + 10.5; SIG = 0.99 x plasma lactate + 2.8. An AG > 15 mEq/L indicated an increased unmeasured anion concentration, whereas a SIG < -2 mEq/L indicated an increased unmeasured strong anion concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Anion gap and SIG can be used to predict plasma lactate concentration in horses. AG is accurate and clinically useful for estimating unmeasured strong ion concentration in horses with total protein concentrations within or slightly outside reference range, whereas SIG is more accurate in horses with markedly abnormal total protein concentrations and those of various ages and with various concentrations of albumin, globulin, and phosphate.
Acid-Base Equilibrium↗
A reliable, practical, and economical protocol for inducing diarrhea and severe dehydration in the neonatal calf.
Fifteen healthy, colostrum-fed, male dairy calves, aged 2 to 7 d were used in a study to develop a diarrhea protocol for neonatal calves that is reliable, practical, and economical. After instrumentation and recording baseline data, diarrhea and dehydration were induced by administering milk replacer [16.5 mL/kg of body weight (BW), PO], sucrose (2 g/kg in a 20% aqueous solution, p.o.), spironolactone and hydrochlorothiazide (1 mg/kg, PO) every 8 h, and furosemide (2 mg/kg, i.m., q6h). Calves were administered sucrose and diuretic agents for 48 h to induce diarrhea and severe dehydration. Clinical changes after 48 h were severe watery diarrhea, severe depression, and marked dehydration (mean, 14% BW loss). Cardiac output, stroke volume, mean central venous pressure, plasma volume, thiocyanate space, blood pH and bicarbonate concentration, base excess, serum chloride concentration, and fetlock temperature were decreased. Plasma lactate concentration, hematocrit, and serum potassium, creatinine, phosphorus, total protein and albumin concentrations were increased. This non-infectious calf diarrhea protocol has a 100% response rate, while providing a consistent and predictable hypovolemic state with diarrhea that reflects most of the clinicopathologic changes observed in osmotic/maldigestive diarrhea caused by infection with rotavirus, coronavirus or cryptosporidia. Limitations of the protocol, when compared to infectious diarrhea models, include failure to induce a severe metabolic acidosis, absence of hyponatremia, renal instead of enteric loss of chloride, renal as well as enteric loss of free water, absence of profound clinical depression and suspected differences in the morphologic and functional effect on intestinal epithelium. Despite these differences, the sucrose/diuretic protocol should be useful in the initial screening of new treatment modalities for calf diarrhea. To confirm their efficacy, the most effective treatment methods should then be examined in calves with naturally-acquired diarrhea.
Animals↗
Electrocardiographic characteristics of endurance-trained Alaskan sled dogs.
OBJECTIVE: To determine electrocardiographic characteristics of endurance-trained Alaskan sled dogs. DESIGN: Case series. ANIMALS: 319 Alaskan sled dogs entered to compete in the 1994 Iditarod Trail Sled Dog Race. PROCEDURE: ECG were recorded while dogs were standing and were analyzed digitally. RESULTS: Amplitudes of P waves (median, 0.40 mV; fifth to 95th percentile range, 0.11 to 0.61 mV) and R waves in lead II (median, 3.02 mV; fifth to 95th percentile range, 1.49 to 4.40 mV) were high; durations of P waves in lead II (median, 61 milliseconds; fifth to 95th percentile range, 36 to 96 milliseconds), QRS complexes (median, 64 milliseconds; fifth to 95th percentile range, 52 to 80 milliseconds), and QT intervals (median, 236 milliseconds; fifth to 95th percentile range, 208 to 277 milliseconds) were prolonged. Median value for mean axis of ventricular depolarization was 57 degrees (fifth to 95th percentile range, 19 to 90 degrees). Atrial and ventricular premature depolarizations were observed in 3 (0.9%) and 4 (1.3%) of 319 dogs, respectively, and paroxysmal ventricular tachycardia was detected in 1 (0.3%). CLINICAL IMPLICATIONS: Results suggest that electrocardiographic characteristics of endurance-trained Alaskan sled dogs differ from those reported for nonsled dogs, probably as a result of effects of endurance training on heart size. Some of these characteristics could be mistaken as evidence of pathologic cardiac hypertrophy.
Alaska↗
Evaluation of breed as a risk factor for atresia coli in cattle.
Systematic review of published cases and a hospital-based case-control study were completed to evaluate breed as a risk factor for atresia coli in cattle. Systematic review of 37 published studies indicated that atresia coli has been diagnosed in 10 cattle breeds and 12 countries, with the marked preponderance of cases occurring in Holstein-Friesian calves (485/514 cases, 94%). Epidemiologic analysis based on 28,373 cattle < 2 mo of age admitted to North American veterinary schools between 1964 and 1993 identified 291 cases of atresia coli in 13 breeds, with the marked preponderance of cases occurring in Holstein-Friesian calves (228/291, 78%). Holstein-Friesian cattle were at significantly greater risk for the condition than all other dairy cattle breeds (crude odds ratio 4.55, P < 0.0001) and all other cattle breeds (crude odds ratio 7.12, P < 0.0001), whereas there was no difference in the odds ratio between dairy cattle (not Holstein-Friesian) and beef cattle (crude odds ratio 1.68, P = 0.11). Atresia coli probably occurs secondary to vascular insufficiency of the developing colon. Holstein-Friesian cattle may be genetically predisposed to atresia coli, possibly because their developing colon grows at a faster rate and/or to a greater extent than that in other cattle breeds. Early or vigorous palpation per rectum of the amniotic vesicle appears to increase the risk of atresia coli in a genetically predisposed fetus, probably through palpation-induced damage to the developing colonic vasculature.
Journal Article↗
Intussusception in cattle: 336 cases (1964-1993).
OBJECTIVE: To evaluate risk factors and to describe clinical and laboratory findings, surgical management, and postoperative outcome for cattle with intussusception. DESIGN: Hospital-based, case-control epidemiologic study and retrospective case series. SAMPLE POPULATION: Medical records of cattle admitted to 17 veterinary medical teaching hospitals in North America. PROCEDURE: Epidemiologic analysis of demographic data and detailed analysis of medical records for selected cattle. RESULTS: 336 cattle with intussusception were identified, 281 had small intestinal, 7 had ileocolic, 12 had cecocolic, and 36 had colocolic intussusceptions. Sex and season were not significantly associated with cattle developing intussusception, whereas calves < 2 months old were at greater risk of developing small intestinal intussusception than older cattle. Analysis of medical records of 57 cattle with intussusception revealed that these cattle were mildly hyponatremic, hypochloremic, hypocalcemic, azotemic, and hyperglycemic. Right flank laparotomy with a cow in a standing position, followed by intestinal resection and end-to-end anastomosis was the most common means of surgical correction. Overall survival rate (20/57; 35%) and postoperative survival rate (20/46; 43%) for cattle with intussusception were much lower than previously reported. CLINICAL IMPLICATIONS: Although rare in cattle, intussusception was most common in calves < 2 months old. Survival rate for cattle treated for intussusception was low (< 50%).
Age Factors↗
A simplified strong ion model for acid-base equilibria: application to horse plasma.
The Henderson-Hasselbalch equation and Stewart's strong ion model are currently used to describe mammalian acid-base equilibria. Anomalies exist when the Henderson-Hasselbalch equation is applied to plasma, whereas the strong ion model does not provide a practical method for determining the total plasma concentration of nonvolatile weak acids ([Atot]) and the effective dissociation constant for plasma weak acids (Ka). A simplified strong ion model, which was developed from the assumption that plasma ions act as strong ions, volatile buffer ions (HCO-3), or nonvolatile buffer ions, indicates that plasma pH is determined by five independent variables: PCO2, strong ion difference, concentration of individual nonvolatile plasma buffers (albumin, globulin, and phosphate), ionic strength, and temperature. The simplified strong ion model conveys on a fundamental level the mechanism for change in acid-base status, explains many of the anomalies when the Henderson-Hasselbalch equation is applied to plasma, is conceptually and algebraically simpler than Stewart's strong ion model, and provides a practical in vitro method for determining [Atot] and Ka of plasma. Application of the simplified strong ion model to CO2-tonometered horse plasma produced values for [Atot] (15.0 +/- 3.1 meq/l) and Ka (2.22 +/- 0.32 x 10(-7) eq/l) that were significantly different from the values commonly assumed for human plasma ([Atot] = 20.0 meq/l, Ka = 3.0 x 10(-7) eq/l). Moreover, application of the experimentally determined values for [Atot] and Ka to published data for the horse (known PCO2, strong ion difference, and plasma protein concentration) predicted plasma pH more accurately than the values for [Atot] and Ka commonly assumed for human plasma. Species-specific values for [Atot] and Ka should be experimentally determined when the simplified strong ion model (or strong ion model) is used to describe acid-base equilibria.
Acid-Base Equilibrium↗