Prevalence and prognostic importance of hypomagnesemia and hypocalcemia in horses that have colic surgery

OBJECTIVE: To determine the prevalence of hypomagnesemia and hypocalcemia in horses with surgical colic. ANIMALS: 35 horses with surgically managed colic. PROCEDURE: Serum concentrations of total magnesium (tMg2+) and calcium (tCa2+), as well as ionized magnesium (iMg2+) and calcium (iCa2+) were analyzed before surgery and 1, 3, 5, and 7 days following surgery. A lead-II ECG and pertinent clinical data were also obtained at each time. RESULTS: Preoperative serum tMg2+ and iMg2+ concentrations were below the reference range in 6 (17%) and 19 (54%) horses, respectively. Serum concentrations of tCa2+ and iCa2+ were less than the reference range in 20 (57%) and 30 (86%) horses before surgery. Horses with strangulating lesions of the gastrointestinal tract had significantly lower preoperative serum concentrations of iMg2+ and iCa2+, as well as a higher heart rate than horses with nonstrangulating lesions. Horses that developed postoperative ileus had significantly lower serum concentrations of iMg2+ after surgery. Serum concentrations of magnesium and calcium (total and ionized) correlated significantly with the PR, QRS, QT, and corrected QT (QTc) intervals. Horses that were euthanatized at the time of surgery (n = 7) had significantly lower preoperative serum concentrations of iMg2+, compared with horses that survived. Neither serum magnesium nor calcium concentrations were predictors of hospitalization time or survival. CONCLUSIONS AND CLINICAL RELEVANCE: Hypomagnesemia and hypocalcemia were common during the perioperative period, particularly in horses with strangulating intestinal lesions and ileus. Serum concentrations of tMg2+ and tCa2+ were less sensitive than iMg2+ and iCa2+ in detecting horses with hypomagnesemia and hypocalcemia.     

Myeloperoxidase assay in plasma and peritoneal fluid of horses with gastrointestinal disease

Gastrointestinal disorders, especially strangulating intestinal obstructions, are still a major cause of illness and death in the horse. Circulating lipopolysaccharides may activate both neutrophils and monocytes. The activated neutrophils release myeloperoxidase (MPO), a specific enzyme with strong oxidative activity. The aim of this study was to evaluate MPO concentrations in the plasma and peritoneal fluid (PF) of horses with colic and to check the hypothesis that these concentrations would be higher in a case of strangulating obstruction than in cases of nonstrangulating disease. By using a specific enzyme-linked immunosorbent assay for equine MPO, we determined the MPO concentrations in horses admitted to a clinic for colic. Horses with nonstrangulating or strangulating obstruction of the large intestine (NSLI or SLI), strangulating obstruction of the small intestine (SSI), or inflammatory bowel disease (IBD) were compared with healthy horses. The horses with SLI, SSI, or IBD had significantly higher MPO levels in plasma and PF than did those in the other 2 groups. The mean plasma level was significantly higher in the horses with NSLI than in the healthy horses. High MPO values in PF indicated necrotic bowel. These results show that neutrophil activation occurs during nonstrangulating and strangulating intestinal obstruction in horses and that the plasma and PF MPO concentrations may be a marker of the severity of the disease.     

Evaluation of activated neutrophils in the blood of horses with colic

OBJECTIVE: To evaluate the activation status of neutrophils in blood samples obtained from horses with naturally occurring colic associated with strangulating obstruction, nonstrangulating obstruction, or inflammatory bowel disease. ANIMALS: 30 horses with naturally occurring colic and 30 healthy control horses. PROCEDURE: Activation status of neutrophils was determined by assessing the number of neutrophils that could pass through filters with 5-microm pores, cell-surface CD11-CD18 expression, and alterations in size and granularity of neutrophils. RESULTS: Horses with impaction or gas colic did not have evidence of activated neutrophils. Horses with inflammatory bowel disease consistently had evidence of activated neutrophils, including decreased leukocyte deformability, increased CD11-CD18 expression, increased neutrophil size, and decreased neutrophil granularity. Horses with strangulating colic had variable results. Of horses with strangulating colic, 7 of 14 had marked changes in filtration pressures, 5 of 14 had increased CD11-CD18 expression, 6 of 14 had changes in neutrophil size, and 5 of 14 had changes in neutrophil granularity. Among horses with strangulating colic, changes in deformability, size, and granularity of neutrophils correlated with an adverse outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Activated neutrophils were detected in all horses with inflammatory bowel disease and a few horses with strangulating colic. Correlation of activated neutrophils with horses that had strangulating colic that died or were euthanatized indicates that activated neutrophils are a negative prognostic indicator. Additional studies are needed to determine whether activated neutrophils contribute directly to the adverse outcome in horses with strangulating colic.     

Fibrinolytic Activity in Plasma From Horses With Gastrointestinal Diseases: Changes Associated With Diagnosis, Surgery, and Outcome

Plasma fibrinolytic activity was evaluated over 5 consecutive days in 59 horses admitted to the Large Animal Teaching Hospital with acute gastrointestinal diseases. Only horses hospitalized for at least 5 days were included in the study. Tissue plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1) were quantitated using standard chromogenic activity assays. Statistical analyses were performed using analysis of variance; differences were considered significant when P < .05. Activity of PAI-1, the primary endogenous inhibitor of fibrinolysis, was significantly increased on hospital days 2, 4, and 5 in horses that died, when compared with those that were discharged from the hospital. Plasma PAI-1 activity was not different at admission, but was significantly increased on hospital days 2 and 3 in horses that underwent surgery, when compared with those that did not, suggesting an acute phase response to surgical intervention. Horses with strangulating intestinal lesions had significantly increased PAI-1 activity on day 3, while PAI-1 activity was significantly greater in horses with inflammatory conditions at the time of admission, when compared with horses with strangulating or nonstrangulating/noninflammatory lesions. Among all horses, PAI-1 activity was significantly higher and tPA activity was significantly lower on day 2 when compared with other hospital days. These results suggest that fibrinolysis is inhibited early in the course of inflammatory gastrointestinal diseases and in response to surgery. In addition, among all horses, the prognosis for survival was poor for those with persistently increased PAI-1 activity, reflecting treatment failure and the loss of hemostatic regulation.     

Clinical comparison between a continuous Lembert pattern wrapped in a carboxymethylcellulose and hyaluronate membrane with an interrupted Lembert pattern for one-layer jejunojejunostomy in horses

Reasons for performing study: Although experimental studies have demonstrated differences in performance between methods for handsewn jejunojejunostomy in horses, information on clinical results after different methods of anastomosis are rare. Hypothesis: A continuous Lembert pattern wrapped in a carboxymethylcellulose and hyaluronate membrane would perform better than an interrupted Lembert pattern for jejunojejunostomy in horses. Methods: Data was reviewed on 32 horses that underwent jejunojejunostomy from 1993–2002. Kaplan‐Meier analyses and rates for post operative colic and death were used to compare outcomes after an interrupted Lembert pattern (15 horses with strangulating lesions and 5 horses with nonstrangulating lesions) and a continuous Lembert pattern with membrane (12 horses with strangulating diseases). Results: None of the 32 horses had post operative ileus or post operative endotoxaemia. One horse with a continuous pattern required a repeat celiotomy for anastomotic impaction. Short‐term survivals for the interrupted Lembert were 100% (nonstrangulating lesions) and 93% (strangulating lesions) and for the continuous pattern 92% (all strangulating). Long‐term rates for mortality and colic episodes were less for the continuous Lembert pattern with membrane compared with the interrupted Lembert for strangulating lesions (P<0.05) and were less for strangulating lesions than for nonstrangulating lesions (P<0.05). For strangulating lesions, Kaplan‐Meier analyses yielded a survival probability of 70% for up to 9 years after the interrupted Lembert pattern and 80% for up to 5 years for the continuous Lembert pattern. Conclusions and relevance: Both Lembert patterns performed well in clinical use, although the continuous pattern with the carboxymethylcellulose and hyaluronate membrane had superior long‐term outcomes with less colic and mortality from colic.     

Serum tumor necrosis factor activity in horses with colic attributable to gastrointestinal tract disease.

Over a 24-month period, serum tumor necrosis factor (TNF) activity was determined in 289 horses with colic attributable to gastrointestinal tract disease. Serum TNF activity was quantitated by use of a modified in vitro cytotoxicity bioassay, using WEHI 164 clone-13 murine fibrosarcoma cells. Causes for colic, determined by clinical and laboratory evaluation, exploratory celiotomy, or necropsy included: gastrointestinal tract rupture (GTR); ileal impaction; small intestinal strangulating obstruction (SIO); proximal enteritis (PE); transient small intestinal distention; large-colon displacement; large-colon volvulus; large-colon impaction; colitis; small-colon obstruction; peritonitis; and unknown. Each diagnosis was placed into 1 of 3 lesion categories: inflammatory disorders (GTR, PE, colitis, peritonitis); strangulating intestinal obstruction (SIO, large-colon volvulus); and nonstrangulating intestinal obstruction (ileal impaction, transient small intestinal distension, large-colon displacement, large-colon impaction, small-colon obstruction, unknown). The prevalence of high serum TNF activity and/or mortality were evaluated. Differences were tested at significance level of P less than 0.05. Approximately 20% of the 289 horses has serum TNF activity greater than that found in clinically normal horses (greater than 2.5 U/ml). Twenty-three horses (8%) had marked increase in serum TNF activity (greater than or equal to 10 U/ml) which was more prevalent among horses with SIO and PE than in horses of other diagnostic groups, except those with GTR. Mortality and marked increase in serum TNF activity were greater in horses with intestinal inflammatory disorders or strangulating intestinal obstruction than in horses with nonstrangulating intestinal obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hypercalcemia on serum concentrations of magnesium, potassium, and phosphate and urinary excretion of electrolytes in horses

OBJECTIVE: To determine effects of experimentally induced hypercalcemia on serum concentrations and urinary excretion of electrolytes, especially ionized magnesium (iMg), in healthy horses. ANIMALS: 21 clinically normal mares. PROCEDURES: Horses were assigned to 5 experimental protocols (1, hypercalcemia induced with calcium gluconate; 2, hypercalcemia induced with calcium chloride; 3, infusion with dextrose solution; 4, infusion with sodium gluconate; and 5, infusion with saline [0.9% NaCl] solution). Hypercalcemia was induced for 2 hours. Dextrose, sodium gluconate, and saline solution were infused for 2 hours. Blood samples were collected to measure serum concentrations of electrolytes, creatinine, parathyroid hormone, and insulin. Urine samples were collected to determine the fractional excretion of ionized calcium (iCa), iMg, sodium, phosphate, potassium, and chloride. RESULTS: Hypercalcemia induced by administration of calcium gluconate or calcium chloride decreased serum iMg, potassium, and parathyroid hormone concentrations; increased phosphate concentration; and had no effect on sodium, chloride, and insulin concentrations. Hypercalcemia increased urinary excretion of iCa, iMg, sodium, phosphate, potassium, and chloride; increased urine output; and decreased urine osmolality and specific gravity. Dextrose administration increased serum insulin; decreased iMg, potassium, and phosphate concentrations; and decreased urinary excretion of iMg. Sodium gluconate increased the excretion of iCa, sodium, and potassium. CONCLUSIONS AND CLINICAL RELEVANCE: Hypercalcemia resulted in hypomagnesemia, hypokalemia, and hyperphosphatemia; increased urinary excretion of calcium, magnesium, potassium, sodium, phosphate, and chloride; and induced diuresis. This study has clinical implications because hypercalcemia and excessive administration of calcium have the potential to increase urinary excretion of electrolytes, especially iMg, and induce volume depletion.     

Comparison of serum parathyroid hormone and ionized calcium and magnesium concentrations and fractional urinary clearance of calcium and phosphorus in healthy horses and horses with enterocolitis

OBJECTIVE: To evaluate calcium balance and parathyroid gland function in healthy horses and horses with enterocolitis and compare results of an immunochemiluminometric assay (ICMA) with those of an immunoradiometric assay (IRMA) for determination of serum intact parathyroid hormone (PTH) concentrations in horses. ANIMALS: 64 horses with enterocolitis and 62 healthy horses. PROCEDURES: Blood and urine samples were collected for determination of serum total calcium, ionized calcium (Ca2+) and magnesium (Mg2+), phosphorus, BUN, total protein, creatinine, albumin, and PTH concentrations, venous blood gases, and fractional urinary clearance of calcium (FCa) and phosphorus (FP). Serum concentrations of PTH were measured in 40 horses by use of both the IRMA and ICMA. RESULTS: Most (48/64; 75%) horses with enterocolitis had decreased serum total calcium, Ca2+, and Mg2+ concentrations and increased phosphorus concentrations, compared with healthy horses. Serum PTH concentration was increased in most (36/51; 70.6%) horses with hypocalcemia. In addition, FCa was significantly decreased and FP significantly increased in horses with enterocolitis, compared with healthy horses. Results of ICMA were in agreement with results of IRMA. CONCLUSIONS AND CLINICAL RELEVANCE: Enterocolitis in horses is often associated with hypocalcemia; 79.7% of affected horses had ionized hypocalcemia. Because FCa was low, it is unlikely that renal calcium loss was the cause of hypocalcemia. Serum PTH concentrations varied in horses with enterocolitis and concomitant hypocalcemia. However, we believe low PTH concentration in some hypocalcemic horses may be the result of impaired parathyroid gland function.     

Plasma ionized calcium and parathyroid hormone concentrations in horses after endurance rides

OBJECTIVE: To evaluate changes in plasma ionized calcium (Ca2+) and parathyroid hormone (PTH) concentrations in horses competing in endurance rides. DESIGN: Longitudinal clinical study. ANIMALS: 28 horses. PROCEDURE: Venous blood samples were obtained from horses before and after racing 80 km. Plasma pH and concentrations of Ca2+, PTH, inorganic phosphorus, albumin, lactate, and magnesium were measured. RESULTS: Overall, a significant decrease in mean (+/- SD) plasma Ca2+ concentration (from 6.44 +/- 0.42 to 5.64 +/- 0.42 mg/dl) and a significant increase in plasma PTH concentration (from 49.9 +/- 30.1 to 148.1 +/- 183.0 pg/ml) were found after exercise. Exercise also resulted in significant increases in plasma inorganic phosphorus, albumin, and lactate concentrations. No changes in plasma magnesium concentration or pH were detected after exercise. Plasma PTH concentration was not increased after exercise in 8 horses; in these horses, plasma PTH concentration decreased from 58.2 +/- 26.3 to 27.4 +/- 22.4 pg/ml, although plasma Ca2+ concentration was also decreased. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma Ca2+ concentration was decreased after racing for 80 km, compared with values obtained before racing. In most horses, an increase in plasma PTH concentration that was commensurate with the decrease in plasma Ca2+ was detected; however, some horses had decreased plasma PTH concentrations.     

Effects of storage on serum ionized calcium and pH from horses with normal and abnormal ionized calcium concentrations

It has been previously shown that Ca(I) concentration is stable in serum collected from healthy horses for 10 days if stored at 40 degrees C. This may not be true for horses with abnormal Ca(I) concentrations. Thus the stability of ionized calcium (Ca(I)) concentration and pH measurement in serum from horses with both normal and abnormal Ca(I) concentrations stored for various times at 40 degrees C and -10 degrees C was evaluated. Our results indicated that serum Ca(I) concentration was stable throughout 7 days of cold or frozen storage, after being received by the Clinical Chemistry Laboratory. Serum Ca(I) concentration showed a significant decrease by 14 days of frozen storage (-10 degrees C). Serum pH showed a statistically significant increase by 7 days of cold storage, and within 3 days of frozen storage. If equine serum is collected, handled and stored anaerobically, and kept cold or frozen, Ca(I) concentration can be accurately measured for approximately 7 days after collection, regardless of the health status of the animal. An accurate measurement of pH may be made within 3 days of cold or 1 day of frozen storage.     

Alterations in serum parathyroid hormone and electrolyte concentrations and urinary excretion of electrolytes in horses with induced endotoxemia

Hypocalcemia and hypomagnesemia are common in horses with sepsis and endotoxemia. We hypothesize that endotoxemia triggers a systemic inflammatory response that results in hypocalcemia and hypomagnesemia. The goal of this study was to determine the effect of endotoxin (lipopolysaccharide [LPS]) administration to healthy horses on serum parathyroid hormone (PTH), ionized calcium (Ca2+) and total calcium (tCa), ionized magnesium (Mg2+) and total magnesium (tMg), phosphate (Pi), potassium (K+), sodium (Na+), chloride (Cl-), and insulin concentrations, and on the urinary excretion of these electrolytes. Twelve mares were infused with Escherichia coli LPS (30 ng/kg/h i.v.) for 1 hour. Six mares were infused with saline (controls). In LPS-infused horses, heart rate increased significantly from (mean +/- SD) 40.0 +/- 1.3 to 70.0 +/- 9.0 beats/min, respiratory rate from 12.7 +/- 1.0 to 21.1 +/- 3.0 breaths/min, body temperature from 37.4 +/- 0.3 to 38.9 +/- 0.6 degrees C, and tumor necrosis factor-alpha concentrations from 6.6 +/- 3.5 to 507 +/- 260 pg/mL (P < .05). White blood cell count decreased significantly from 7570 +/- 600 to 1960 +/- 560 cells/ microL. Serum concentrations of Ca2+ decreased from 6.5 +/- 0.3 to 6.0 +/- 0.3 mg/dL, of Mg2+ from 0.53 +/- 0.06 to 0.43 +/- 0.04 mM, of tMg from 0.78 +/- 0.05 to 0.62 +/- 0.08 mM, of K+ from 4.3 +/- 0.4 to 3.0 +/- 0.5 mEq/L, and of Pi from 3.4 +/- 0.5 to 1.7 +/- 0.5 mg/dL (all P < .05). PTH increased significantly from 1.3 +/- 0.4 to 6.0 +/- 5.2 pM; however, in some horses (n=2), PTH did not increase despite hypocalcemia. Insulin increased significantly from 9.4 +/- 3.6 to 50.5 +/- 9.6 microIU/mL (n=3). Urinary fractional excretion of Ca2+ decreased significantly from 4.7 +/- 1.4 to 1.7 +/- 1.2%, of Mg2+ from 36.6 +/- 6.5 to 11.7 +/- 7.3%, and of K+ from 37.9 +/- 11.3 to 17.7 +/- 6.2%. Fractional excretion of Pi increased from 0.02 +/- 0.02 to 0.14 +/- 0.07% and of Na+ from 0.26 +/- 0.13% to 1.2 +/- 0.5%. No changes were found in serum tCa, Na+, and Cl- concentrations. In conclusion, endotoxemia in horses resulted in electrolyte abnormalities that included hypocalcemia, hypomagnesemia, hypokalemia, hypophosphatemia, and increased serum PTH and insulin concentrations.     

Influence of age and sex on serum osteocalcin concentrations in horses at weaning and during physical conditioning

Three experiments were conducted to evaluate serum osteocalcin concentrations in normal weanling and yearling Quarter Horses. In Experiment 1, jugular blood samples were taken at 3 hr intervals for 24 hr to evaluate diurnal changes in serum osteocalcin concentration of foals (n=3) and yearlings (n=5). In Experiment 2, twelve Quarter Horse foals were weaned at 4 months of age to determine the influence of sex, weaning and method of weaning of serum osteocalcin concentration. The third experiment utilized fifteen yearling Quarter Horses (7 geldings, 8 fillies) in a two-phase trial to evaluate normal peripheral osteocalcin concentration in sedentary and exercising horses. In Experiment 1, there was no detectable variation (P>.05) in serum osteocalcin concentration during the 24 hr sample period in either age group. In Experiment 2, colts had greater (P<.05) osteocalcin concentrations than fillies at weaning. Method of weaning did not alter mean serum osteocalcin concentration (P>.1). Serum osteocalcin concentrations declined (P<.05) in all horses following weaning but returned to preweaning levels within one week. In Experiment 3, sedentary horses had similar (P>.1) osteocalcin concentrations on d 0, 45 and 90. Serum osteocalcin concentrations of sedentary horses were not affected by sex (P>.1). During exercise, fillies had greater (P<.05) osteocalcin concentrations than geldings. Serum osteocalcin concentrations of all horses declined linearly (P<.0001) during the 90 d exercise period. Osteocalcin may be useful as a tool to assess bone metabolism during growth and physical conditioning in horses. However, variability in serum osteocalcin concentrations due to age, sex and level of activity suggest that these factors must also be considered.     

AN EXAMINATION OF THE CALCIUM AND PHOSPHORUS NUTRITION OF THOROUGHBRED RACEHORSES

SUMMARY The calcium and phosphorus nutrition of thoroughbred racehorses was assessed by analysis of serum and urine samples collected from 90 horses in 1975 and 139 horses in 1980–81 at racetracks in Melbourne. Horses that were excreting greater than 15 μmole Ca/mosmole and which had a calcium to creatinine clearance ratio greater than 2.5% were considered to have adequate Ca intake. Horses that were excreting greater than 15 μmole P/mosmole and which had a phosphorus to creatinine clearance ratio greater than 4% were considered to have excessive phosphorus intake. Sixty-percent of the horses sampled had adequate Ca intake, and 44% had excessive intakes of P. Twenty-five percent of the horses were excreting more P in urine than Ca. This would indicate these horses were subjected to nutritional secondary hyperparathyroidism, and horses entered in races by 53 of 99 trainers were in this category. It may be concluded that a high proportion (40%) of thoroughbred racehorses receive inadequate calcium nutrition while they are fed high-grain diets during racing.     

Assessment of vitamin E concentrations in serum and cerebrospinal fluid of horses following oral administration of vitamin E

OBJECTIVE: To determine concentrations of alpha-tocopherol in serum and CSF of healthy horses following administration of supplemental vitamin E in feed. ANIMALS: 10 healthy adult horses. PROCEDURES: Horses were allocated to receive supplemental d-alpha-tocopherol (1,000 U/d [group A; n=5] or 10,000 U/d [group B; 5]) in feed for 10 days. Blood samples were collected before (baseline), during, and at intervals for 10 days after discontinuation of vitamin E administration for assessment of serum alpha-tocopherol concentration. Cerebrospinal fluid samples were collected prior to and 24 hours after cessation of vitamin E administration. Alpha-tocopherol concentrations in serum and CSF samples were analyzed via high-performance liquid chromatography; changes in those values during the treatment period were compared between groups, and the relationship of serum and CSF alpha-tocopherol concentrations was evaluated. RESULTS: In both groups, serum alpha-tocopherol concentration increased significantly from baseline during vitamin E administration; values in group B were significantly greater than those in group A during and after treatment. At the end of vitamin E administration, CSF alpha-tocopherol concentration was not significantly greater than the baseline value in either group; however, the increase in CSF concentration was significant when the group data were combined and analyzed. Serum and CSF alpha-tocopherol concentrations were significantly correlated at baseline for all horses, but were not strongly correlated after 10 days of vitamin E administration. CONCLUSIONS AND CLINICAL RELEVANCE: In healthy horses, daily oral administration of supplemental vitamin E in feed resulted in increases in serum and CSF alpha-tocopherol concentrations.     

Use of plasma ionized calcium levels and Ca(2+) substitution response patterns as prognostic parameters for ileus and survival in colic horses

Summary Objective: Hypocalcaemia is a common finding in horses with enterocolitis and severe gastrointestinal disorders. The aims of this study were to investigate in colic horses (!))the parameters related to hypocalcaemia, (2))the influence of hypocalcaemia on outcome and (3))the possible beneficial effect of Ca(2+ )substitution. Design: Randomized controlled trial. Setting: Intensive care unit. Patients: One hundred forty-four horses that were admitted with an acute abdomen during a 1.5 year period were enrolled and daily evaluated for clinical criteria and whole blood ionized Ca levels. Colic horses with hypocalcaemia were randomly assigned to receive Ca(2+). Interventions: Analysis of heparinised whole blood samples. Horses that were assigned to be treated received 400 mEq Ca(2+) diluted in 10L of Ringer's lactate solution every 24 h until low reference range limits were obtained or until death. Measurements and main results: 88% of all colic patients showed blood ionized Ca levels below the reference range at the time of admission. Multivariable analysis revealed that the presence of reflux signs of endotoxaemia increased Packed Cell Volume (PCV) alkalinization of pH and the interaction PCV/pH all predispose colic horses to low ionized Ca(2+) levels at the time of admission. The Odds for developing ileus during hospitalization are ± 11.94 times larger for horses in the "very low" calcaemia interval in comparison with normocalcaemic horses. The Odds for fatal outcome are respectively ± 9.82 and 8.33 times larger for horses in the "very low" and "low" calcaemia interval. Ca(2+) substitution increased the probability of survival provided that Ca(2+) levels could be normalized. The lack of an upward calcaemia response despite repetitive Ca(2+) substitutions can be guarded as a poor ominous sign. Conclusions: Hypocalcaemia in colic horses is of prognostic relevance both with regard to survival as to the probability of development of ileus during hospitalization. This study shows the importance of routine measurement of ionized calcium levels in colic horses. Moreover correction of hypocalcaemia seems to improve clinical outcome.     

Role of prokinetic drugs for treatment of postoperative ileus in the horse

All horses undergoing coeliotomy for an acute abdominal crisis are at risk of developing ileus and should receive therapy aimed at promoting gastrointestinal function by restoring fluid and electrolyte balance. Adequate analgesia and prevention against peritonitis, bacteraemia and endotoxaemia should be provided. Horses that at the time of surgery have a strangulating or non-strangulating small intestinal obstruction should be considered to be at greater risk of developing a persistent ileus that is refractory to treatment than those horses with lesions involving the large intestine. In horses considered to be at greater risk of developing a persistent ileus, the use of prokinetic agents should be considered. Agents that may be used to improve gastrointestinal motility include adrenergic receptor antagonists, cholinergic agonists, benzamides, dopamine antagonists, macrolide antimicrobials, opiate receptor agonists and antagonists, somatostatin analogues and local anaesthetics. There are limited studies into the use of these agents in the horse. Until further research provides more information on motility disorders following intestinal surgery and the efficacy of prokinetic agents in this species, only selective use of some of these drugs can be recommended.     

Use of plasma ionized calcium levels and Ca2+ substitution response patterns as prognostic parameters for ileus and survival in colic horses

OBJECTIVE: Hypocalcaemia is a common finding in horses with enterocolitis and severe gastrointestinal disorders. The aims of this study were to investigate in colic horses 1)the parameters related to hypocalcaemia, 2)the influence of hypocalcaemia on outcome and 3)the possible beneficial effect of Ca2+ substitution. DESIGN: Randomized controlled trial. SETTING: Intensive care unit. PATIENTS: One hundred forty-four horses that were admitted with an acute abdomen during a 1.5 year period were enrolled and daily evaluated for clinical criteria and whole blood ionized Ca2+ levels. Colic horses with hypocalcaemia were randomly assigned to receive Ca2+. INTERVENTIONS: Analysis of heparinised whole blood samples. Horses that were assigned to be treated received 400 mEq Ca2+ diluted in 10L of Ringer's lactate solution every 24 h until low reference range limits were obtained or until death. MEASUREMENTS AND MAIN RESULTS: 88% of all colic patients showed blood ionized Ca2+ levels below the reference range at the time of admission. Multivariable analysis revealed that the presence of reflux, signs of endotoxaemia, increased Packed Cell Volume (PCV), alkalinization of pH and the interaction PCV/pH all predispose colic horses to low ionized Ca2+ levels at the time of admission. The Odds for developing ileus during hospitalization are +/- 11.94 times larger for horses in the "very low" calcaemia interval, in comparison with normocalcaemic horses. The Odds for fatal outcome are respectively +/- 9.82 and 8.33 times larger for horses in the "very low" and "low" calcaemia interval. Ca2+ substitution increased the probability of survival, provided that Ca2+ levels could be normalized. The lack of an upward calcaemia response, despite repetitive Ca2+ substitutions, can be guarded as a poor ominous sign. CONCLUSIONS: Hypocalcaemia in colic horses is of prognostic relevance both with regard to survival as to the probability of development of ileus during hospitalization. This study shows the importance of routine measurement of ionized calcium levels in colic horses. Moreover, correction of hypocalcaemia seems to improve clinical outcome.     

The effect of calcium and phosphorus supplementation, inactivity, and subsequent aerobic training on the mineral balance in young, mature, and aged horses

A randomized complete block design experiment was conducted to determine the effect of Ca and P supplementation, inactivity, and subsequent aerobic exercise on Ca and P serum concentrations, and balance and digestibilities in young, mature, and aged horses. Twelve stock-type geldings were blocked into three age groups: 2 and 3, 7 to 11, and 15 to 21 years of age. Two groups of six horses were randomly assigned to either control (C) or mineral supplemented (T) diet. Horses consuming C received about 133% of National Research Council (NRC) requirements for Ca and P, while horses consuming T received about 275% of NRC requirements for Ca and P. The trial consisted of eight 21-d periods. During periods I, II, and III, all horses were inactive, and during periods IV, V, VI, VII, and VIII, all horses performed an ascending aerobic exercise regimen. Serum samples were taken at the beginning of period I and at 21-d intervals thereafter for determination of serum Ca and P. Total fecal and urine collections were taken for 72 h at the beginning of period I and at 21-d intervals thereafter for determination of Ca and P balance. Overall mean apparent Ca balance was affected by treatment (P < .009); time (P < .001); and the interaction of time and treatment (P < .001). Overall mean apparent Ca balance was higher (P < .009) for T as compared to C (23.63 vs. 3.77 mg/kg BW). Mean apparent Ca digestibility was affected by time (P < .001) and the interaction of time and age (P < .001). Mean apparent P balance was affected by time (P < .001) and the interaction of time and treatment (P < .032). Increases in Ca balance may indicate more available mineral for bone metabolism, particularly when remodeling is triggered with the onset of exercise following a sedentary period, suggesting a possible benefit to feeding additional Ca above current NRC recommendations.     

Survival and Complications After Large Colon Resection and End‐to‐End Anastomosis for Strangulating Large Colon Volvulus in Seventy‐Three Horses

Objective— To report complications and survival after large colon resection and end‐to‐end anastomosis in horses with strangulating large colon volvulus. Study Design— Retrospective case series. Animals— Horses (n=73) with strangulating large colon volvulus. Methods— Records (January 1995 to December 2005) of horses that had large colon resection and anastomosis for strangulating large colon volvulus were reviewed for complications. Follow‐up data were obtained by telephone questionnaire at least 1 year postoperatively. Cox proportional hazards model was used for multivariate association with survival time. Variables included admission date, age, temperature, heart rate, packed cell volume, total plasma protein concentration, white blood cell count, breed, and sex. Significance was set at P<.05. Results— The most common postoperative complication was diarrhea. None of the 9 variables of interest were significant for survival. Short‐term survival rate (to discharge) was 74%. Overall survival rates at 1, 2, and 3 years postoperatively were 67.8%, 66.0%, and 63.5%, respectively. Four horses died of colic in the first year after surgery. All horses surviving long‐term (>1 year) returned to their intended use (37 brood mares, 2 racehorses, and 1 show horse) with no chronic problems related to the surgical procedure. Conclusion— None of the variables examined were associated with survival. Outcomes were similar to other large studies of surgical colic in the horse. Self‐limiting diarrhea is common after large colon resection and the prognosis for survival after hospital discharge is favorable. Clinical Relevance— Horses that survive the early postoperative period and are discharged after large colon resection and anastomosis have a good chance for long‐term survival with minimal negative impact on quality of life and use.