Multivariable prediction model for the need for surgery in horses with colic.

A survey of 1,965 equine colic cases was conducted from August 1985 to July 1986 at 10 equine referral centers located throughout the United States. The purpose of this study was to develop and validate a multivariable model for the need for surgery. Two-thirds of the cases were randomly selected for model development (1,336), whereas the remaining cases (629) were used only for subsequent validation of the model. If a lesion requiring surgical correction was found at either surgery or necropsy, the case for the horse was classified as surgical, otherwise the case was classified as medical. Only variables that were significant (P less than 0.05) in an initial bivariable screening procedure were considered in the model development. Because of the large number of missing values in the data set, only variables for which there were less than 400 missing values were considered in the multivariable analysis. A multivariable logistic regression model was constructed by use of a stepwise algorithm. The model used 640 cases and included variables: rectal findings, signs of abdominal pain, peripheral pulse strength, and abdominal sounds. The likelihood ratio for surgery was calculated for each horse in the validation data set, using the logistic regression equation. Using Bayes theorem, the posttest probability was calculated, using the likelihood ratio as the test odds and the prevalence of surgery cases (at each institution) as an estimate of the pretest odds. A Hosmer-Lemeshow goodness-of-fit chi 2 statistic indicated that the model fit the validation data set poorly, as demonstrated by the large chi 2 value of 26.7 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of clinical pathology in evaluation of horses with colic

Clinical pathology is a valuable adjunct to physical examination of cases of colic. The present review considers evaluation of cases of colic for three main purposes: (1) making a prognosis, (2) deciding whether to operate, and (3) making a diagnosis. Blood tests noted to be useful for prognostication were hematocrit, lactate and urea nitrogen concentrations, pH, anion gap, fibrin/fibrinogen degradation products, antithrombin III activity, prothrombin time, and thrombin time. Horses with a poor prognosis often have relative polycythemia, marked lactic acidosis, high anion gap, azotemia, and coagulation abnormalities evidenced by increased fibrin/fibrinogen degradation products, decreased antithrombin III activity, and prolonged prothrombin and thrombin times. The decision to operate is usually a clinical one, supported by relative polycythemia, hyperglycemia, and, possibly, abnormal peritoneal fluid analysis. Diagnosis of the primary problem (causing the colicky signs) is also often based largely on physical examination. However, peritoneal fluid analysis provides worthwhile data, especially in cases of peritonitis or intestinal ischemia and infarction.     

Plasma arginine vasopressin concentration in horses undergoing surgery for colic

Objective – To determine if horses before undergoing anesthesia for surgical correction of colic would have lower plasma arginine vasopressin (AVP) concentrations than healthy horses undergoing anesthesia for arthroscopic surgery, and would not increase their plasma AVP concentrations in response to anesthesia and surgery. Design – Prospective clinical study. Setting – University teaching hospital. Animals – Fourteen horses with colic and 8 healthy horses. Interventions – Horses with colic underwent anesthesia and surgery for alleviation of colic, and healthy horses underwent anesthesia and surgery for arthroscopy. Measurements and Main Results – Plasma AVP was measured perioperatively in horses with colic and in healthy horses. Before anesthesia, and 30 and 60 minutes after induction, horses with colic had greater median plasma AVP concentrations than control horses (P≤0.001); thereafter during anesthesia differences in AVP concentrations between the 2 groups were not significant. In the control group, plasma AVP concentration increased during 120 minutes of anesthesia; no such increase occurred in colic horses. Conclusions – Compared with healthy horses, horses with colic had higher preanesthesia plasma AVP concentrations that did not increase further in response to anesthesia and surgery. Exogenous AVP is associated with decreased splanchnic perfusion in a variety of animal species and, therefore, could be detrimental to horses with colic. Thus, it may be inappropriate to use exogenous AVP in support of blood pressure in anesthetized horses with colic. Further studies are warranted to define appropriate indications for the use of AVP in horses with colic.     

Effects of aerobic and anaerobic fluid collection on biochemical analysis of peritoneal fluid in healthy horses and horses with colic

Objective: To determine whether in healthy horses and those with colic, exposure of peritoneal fluid to room air affects values obtained on biochemical analysis. Study Design: Prospective study. Animals: Adult horses with a primary complaint of acute abdominal pain (n=29) and 12 healthy horses. Methods: Peritoneal fluid was aseptically collected under aerobic and anaerobic conditions. After collection, pH, PCO₂, PO₂, HCO₃^?, Na⁺, ionized Ca²⁺, K⁺, lactate, and glucose were immediately measured using a commercial blood gas analyzer. Biochemical variables were compared between aerobically and anaerobically obtained samples using a paired t‐test. Results: In healthy horses, peritoneal fluid samples collected under anaerobic conditions had higher PCO₂ and ionized Ca²⁺ and lower PO₂, HCO₃^?, and pH compared with samples exposed to air. No differences were observed for K⁺, Na⁺, glucose, and lactate. In horses with colic, samples collected anaerobically had higher PCO₂, ionized Ca²⁺, Na⁺, and glucose and lower PO₂, HCO₃^?, and pH value compared with samples exposed to air. No differences were observed for K⁺ and lactate. Conclusion: Exposure of peritoneal fluid to room air had a significant effect on pH, PCO₂, PO₂, and variables associated or dependent on changes in pH such as HCO₃^? and ionized Ca²⁺. Interpretation of biochemical analysis of peritoneal fluid may be influenced by sample collection method.     

Use of force plate analysis to compare the analgesic effects of intravenous administration of phenylbutazone and flunixin meglumine in horses with navicular syndrome

OBJECTIVE: To use force plate analysis to evaluate the analgesic efficacies of flunixin meglumine and phenylbutazone administered i.v. at typical clinical doses in horses with navicular syndrome. ANIMALS: 12 horses with navicular syndrome that were otherwise clinically normal. PROCEDURE: Horses received flunixin (1.1 mg/kg), phenylbutazone (4.4 mg/kg), or physiologic saline (0.9% NaCI; 1 mL/45 kg) solution administered IV once daily for 4 days with a 14-day washout period between treatments (3 treatments/horse). Before beginning treatment (baseline) and 6, 12, 24, and 30 hours after the fourth dose of each treatment, horses were evaluated by use of the American Association of Equine Practitioners lameness scoring system (half scores permitted) and peak vertical force of the forelimbs was measured via a force plate. RESULTS: At 6, 12, and 24 hours after the fourth treatment, subjective lameness evaluations and force plate data indicated significant improvement in lameness from baseline values in horses treated with flunixin or phenylbutazone, compared with control horses; at those time points, the assessed variables in flunixin- or phenylbutazone-treated horses were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with navicular syndrome treated once daily for 4 days, typical clinical doses of flunixin and phenylbutazone resulted in similar significant improvement in lameness at 6, 12, and 24 hours after the final dose, compared with findings in horses treated with saline solution. The effect of flunixin or phenylbutazone was maintained for at least 24 hours. Flunixin meglumine and phenylbutazone appear to have similar analgesic effects in horses with navicular syndrome.     

Use of noninvasive dental dolorimetry to evaluate analgesic effects of intravenous and intrathecal administration of morphine in anesthetized dogs

OBJECTIVE: To determine whether changes in amplitude of the reflex-evoked muscle action potential (REMP) elicited by noninvasive dental dolorimetry (electrical stimulation of the tooth pulp) in anesthetized dogs may be used to objectively evaluate the effectiveness of IV and intrathecal (IT) administration of morphine. ANIMALS: 6 male Beagles that were 2 to 6 years old. PROCEDURE: Dogs were used in a crossover design with at least a 5-day washout period between treatments. Each dog received morphine, saline (0.9% NaCl) solution, and oxytocin via the IV and IT routes of administration; however, only results for morphine and saline treatments were reported here. Dogs were anesthetized and prepared for noninvasive dental dolorimetry. After IV or IT administration, electrical stimulation was applied to a tooth, and REMPs of the digastricus muscle were recorded at 5-minute intervals for 60 minutes. To determine differences in REMP amplitude between treatments, a linear regression line was fitted for each dog-treatment combination. RESULTS: The IV administration of morphine significantly inhibited REMP amplitude, compared with IV administration of saline solution. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: Noninvasive dental dolorimetry in anesthetized dogs has promise as a technique for use in evaluating the analgesic potential of drugs administered IV and IT through evaluation of their effect on REMP amplitude recorded for the digastricus muscle.     

Use of newly developed assays for protein C and plasminogen in horses with signs of colic

Protein C content and plasminogen activity were measured in plasma from 100 horses with signs of colic. Data were analyzed by grouping horses 4 ways. Each horse was allotted to 1 of 2 outcome groups (survivors and nonsurvivors), 1 of 3 broad-category diagnosis groups (inflammatory disorders, strangulating obstructions, and all other gastrointestinal disorders), and 1 of 2 clinical management groups (medical and surgical). In a fourth grouping, all horses (although numbers of horses included in each subgroup were small) were assigned either to specific diagnostic groups that had high expectation for activated hemostasis (intestinal ischemia, endotoxemia, jugular thrombosis, peritoneal adhesions, and laminitis) or to a control group, in which active hemostasis was unlikely. Within 2 to 24 hours after admission, nonsurvivors developed lower protein C content than did survivors. Protein C content and plasminogen activity became low during hospitalization in horses with strangulating obstructions and in horses having surgery. The results from the grouping by specific diagnosis must be considered pilot data because the numbers of horses in each subgroup were small. Although not statistically significant, trends were noticed in protein C and plasminogen: (1) horses with intestinal ischemia and endotoxemia developed low protein C content and plasminogen activity, (2) protein C content became low in horses that developed peritoneal adhesions or laminitis, and (3) plasminogen activity became low in horses that developed jugular thrombosis. Low protein C content or low plasminogen activity, or both, may be useful as predictors for outcome and for these specific complications of equine colic.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of force plate analysis to assess the analgesic effects of etodolac in horses with navicular syndrome

OBJECTIVE: To evaluate the musculoskeletal analgesic effect of etodolac administered PO every 12 or 24 hours in chronically lame horses by use of force plate analysis. ANIMALS: 22 horses with navicular syndrome. PROCEDURE: Horses received etodolac (23 mg/kg, PO, q 12 h; n = 7), etodolac (23 mg/kg, PO, q 24 h; 8), or corn syrup (20 mL, PO, q 24 h; control treatment; 7) for 3 days. Combined forelimb peak vertical ground reaction force (PVF) was measured via force plate analysis before the first treatment (baseline) and at 6, 12, 24, and 36 hours after the last treatment. Differences in mean PVF (mPVF) between baseline and subsequent measurements were analyzed (repeated-measures ANOVA) and evaluated for treatment and time effects and treatment-time interaction. RESULTS: Once- or twice-daily administration of etodolac resulted in significant increases in mPVF from baseline at 6, 12, and 24 hours after the last treatment, compared with the control treatment. There were no significant differences in mPVF between the etodolac treatment groups at any time point. In both etodolac treatment groups, there was a significant increase in mPVF from baseline at 6, 12, and 24 hours, compared with that at 36 hours. Etodolac-associated adverse effects were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: In horses with navicular syndrome, once-daily oral administration of 23 mg of etodolac/kg appears to provide effective analgesia for as long as 24 hours. Twice-daily administration of etodolac at this same dose does not appear to provide any additional analgesic efficacy or duration of effect.     

Use of right ventricular pressure increase rate to evaluate cardiac contractility in horses

OBJECTIVE: To establish reference values for right ventricular maximal rate of increase in pressure (dP/dt(max)) in horses and determine the usefulness of this variable to evaluate cardiac contractility. ANIMALS: 15 crossbred horses, 3 to 20 years old. PROCEDURE: Cardiac catheterization was performed, using a high-fidelity catheter tip micromanometer, to determine right ventricular dP/dt(max). The following mathematic corrections were made: for preload, (dP/dt(max))/instantaneous total pressure, (dP/dt(max))/instantaneous developed pressure, and (dP/dt(max))/end diastolic pressure; for afterload, (dP/dtCPIP)/common peak isovolumic pressure. Wedge pressure was measured simultaneously, using a Swan-Ganz catheter. A negative inotropic drug, detomidine hydrochloride, was administered to 6 horses to examine the effect of the negative inotropic drug on right ventricular dP/dt(max) and derived variables. RESULTS: The mean right ventricular dP/dt(max) was 477 (+/- 84.1) mm Hg/s in 15 horses. A 40% decrease in dP/dt(max) was found for 30 minutes after detomidine administration. Variables that correct for preload and afterload were influenced similarly. Detomidine administration also caused a 24% increase in mean wedge pressure, probably indicating reduced left-sided cardiac contractility. CONCLUSIONS AND CLINICAL RELEVANCE: Right ventricular dP/dt(max) may be a useful clinical variable for determining acute changes in cardiac contractility in horses.     

Retrospective study of the risk factors and prevalence of colic in horses after orthopaedic surgery

The records of 496 orthopaedic operations on 428 horses were reviewed to estimate the prevalence of, and identify the risk factors for, the development of colic in horses after surgery. Colic was defined as any recognised sign of abdominal pain that could not be attributed to a concurrent disease. Fourteen of the horses developed colic; eight of them were undiagnosed, three were classified as impactions, one as tympanic colic of the colon, one as incarceration of the small intestine in the epiploic foramen, and one as left dorsal displacement of the colon in the nephrosplenic space. Morphine was associated with a four-fold increased risk of colic compared with the use of no opioid or butorphanol, and out-of-hours surgery was also associated with an increased risk.     

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.     

Use of a novel one-nostril mask-spacer device to evaluate airway hyperresponsiveness (AHR) in horses after chronic administration of albuterol

Inflammatory airway disease (IAD) is very common in stabled horses. Short-acting beta agonist (SABA) drugs are often used to relieve clinical signs, although long-term exposure to these drugs may result in rebound bronchoconstriction. The purpose of this study was twofold: i) to describe the deposition of radiolabeled drugs using a novel one-nostril design mask-spacer combination with a breath-activated inhaler (BAI), and ii) to determine whether treatment for 10 d with inhaled albuterol using this device would impair the ability of albuterol to prevent bronchospasm during a histamine challenge test. The percentage of radio-aerosol deposited in the total lung was 12.39% ± 5.05%. All study horses demonstrated airway hyperresponsiveness (AHR) before enrollment in the study [mean provocative concentration eliciting 35% increase in delta flow (PC35) < 6 mg/mL histamine]. There was no significant difference in airway hyperresponsiveness to post-albuterol histamine challenge before or after treatment with albuterol. A 10-d treatment with placebo, however, caused a significant increase in airway hyperresponsiveness in all horses (P < 0.001). The results of this study show that the novel mask-spacer device was effective in delivering radiolabeled aerosolized drug to the lung and that delivery of a SABA for 10 d using this device did not result in increased airway hyperresponsiveness.     

Morphine administration in horses anaesthetized for upper respiratory tract surgery

OBJECTIVE: To determine the effect of morphine administration on commonly monitored cardio-respiratory variables and recovery quality in horses undergoing anaesthesia and surgery. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: Thirty-eight thoroughbred horses, 32 geldings and six mares, 3-13 years old, weighing 411-600 kg. MATERIALS AND METHODS: A standard anaesthetic technique was used. Twenty minutes after induction of anaesthesia horses received 0.1 mg kg(-1) (0.1 m) or 0.2 mg kg(-1) (0.2 m) morphine by intravenous injection. A control group did not receive morphine. Heart rate, respiratory rate (fr), mean arterial pressure (MAP) and blood gases were measured before morphine administration and every 10 minutes thereafter. Horses were positioned for 35 minutes in right lateral recumbency for tension palatoplasty by cautery and were then moved into dorsal recumbency for additional intraluminal surgery comprising one or more of aryepiglottic fold resection, sub-epiglottal mucosal resection, ventriculectomy and cordectomy. A subjective recovery score from 0 (worst) to 5 (best) was assigned by a single observer who was unaware of treatment group. Two-way repeated measures anova, one-way anova, Kruskal-Wallis test, Mann-Whitney test, Pearson and Spearman correlation coefficients, and chi-squared tests were used to analyse the data where appropriate. RESULTS: Arterial partial pressure of oxygen (PaO(2)) decreased significantly over time and was significantly lower in horses that received morphine. One horse in the control group and two horses in each of the morphine groups had a PaO(2) <13 kPa. No other significant cardiopulmonary effects were detected. Recovery scores [median (range)] were higher in morphine recipients: 4 (2-5) in 0.1 m, 4 (3-5) in 0.2 m compared with 3 (2-4) in the control group. CONCLUSIONS AND CLINICAL RELEVANCE: The lower PaO(2) in morphine recipients did not appear to be of clinical significance in healthy horses because the number of horses with a low PaO(2) was similar between groups. The quality of recovery was significantly better in morphine recipients. These results indicate that morphine may be considered for use in clinical cases although further work is required to assess the analgesic properties of the drug in this species.     

Use of the Accusport semi-automated analyser to determine blood lactate as an aid in the clinical assessment of horses with colic

The most useful diagnostic methods in the initial evaluation of horses with colic assess the morphological and functional status of the gastrointestinal tract and cardiovascular status. This evaluation is best achieved using a combination of clinical and laboratory data. Blood lactate concentration (BL) is one of these variables. BL rises mainly due to poor tissue perfusion and anaerobic glycolysis associated with shock, providing an indicator of both the severity of disease and its prognosis. A hand-held lactate meter, Accusport, provides a rapid (60 seconds), inexpensive dry-chemical-based determination of BL. This trial evaluated the Accusport's ability to provide BL data as an adjunct to the initial clinical evaluation of horses with colic. The accuracy of the Accusport was tested by evaluation of its interchangeability with the benchmark enzymatic kit evaluation of BL in a trial using data collected firstly from 10 clinically normal control horses and subsequently from 48 horses presented with signs of colic. The BL values were recorded together with the clinical variables of heart rate (HR), capillary refill time (CRT), haematocrit (Hct), and pain character and severity on the initial assessment of the colic horses. Information regarding choice of therapeutic management (medical or surgical) and eventual case outcome (full recovery or died/euthanased) was recorded. The Accusport was found to be interchangeable with the enzymatic kit for recording BL values in colic horses with BL < 10 mmol/l, which is within the BL range associated with survival. The interchangeability of an additional, laboratory-based wet chemical assay for BL, the Stat 7 was simultaneously evaluated for the colic and control horses. The Stat 7 was found to be interchangeable with the enzymatic kit for BL determination of colic horses. No linear associations between BL values with HR, CRT, Hct or pain assessment were observed. No relationship with either selection of therapeutic method or eventual case outcome was observed. All horses with BL >8 mmol/l died or were euthanased.     

Myonecrosis in three horses with colic: evidence for endotoxic injury

Three horses with colic, clinical evidence of endotoxaemia and high serum activities of creatine kinase and aspartate aminotransferase were examined postmortem. The horses were diagnosed with severe ulcerative colitis, pyloric ulceration and stenosis with colonic sand impaction, and colonic obstruction due to faecaliths. There was no gross or histological evidence of muscle trauma. Their semimembranosus muscles had scattered acute to subacute segmental necrosis of the myofibres, suggestive of endotoxin-induced muscle injury.     

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.     

Demographics and costs of colic in Swedish horses

BACKGROUND: Colic is an important cause of morbidity and mortality in horses. In Sweden, an insurance database with diagnostic medical information is maintained on >30% of the nation's horse population. HYPOTHESIS: The objective was to describe the occurrence of colic, defined by costly veterinary care and life claims, in horses at 1 insurance company during 1997-2002. HORSES: All horses (<21 years of age) with complete insurance for veterinary care and life during the period 1997-2002 were included. METHODS: Colic was defined as conditions where the main clinical sign was abdominal pain and the problem was related to the gastrointestinal system. The analyses included measures of incidence by sex, breed group, age categories, geographical location (urban/other), survival to and survival after colic, medical cost for colic, and multivariable modeling of risk factors related to the event of colic. RESULTS: In all, 116,288 horses contributed to 341,564 horse years at risk (HYAR). There were 3,100 horses with a colic diagnosis, of which 27% were settled for life insurance. The median gross cost for veterinary care was 4,729 Swedish Kronor (SEK). The overall occurrence and mortality rate of colic was 91 and 24 events per 10,000 HYAR. Survival after colic at 1 month was 76% (95% confidence interval: 75-78%). CONCLUSIONS AND CLINICAL IMPORTANCE: The occurrence of colic varied with breed group, age, and season. The mortality rates probably reflected the true mortality of colic. The veterinary care rates most likely underestimated of the risk colic because they represent relatively costly events.     

Dietary and other management factors associated with colic in horses.

OBJECTIVE: To determine whether dietary and other management factors were associated with development of colic in horses. DESIGN: Prospective matched case-control study. POPULATION: 2,060 horses examined by veterinarians in private practice in Texas for colic and noncolic emergencies. PROCEDURE: Each month for 12 months, participating veterinarians were sent forms to collect information on 1 horse with colic and 1 horse that received emergency treatment for a condition other than colic, information collected included signalment, farm management and characteristics, diet, medical and preventive medical factors, transport, and activity or use. Case and control horses were compared by means of conditional logistic regression to identify factors associated with colic. RESULTS: Recent change in diet, recent change in type of hay, history of previous episode of colic, history of abdominal surgery for colic, recent change in weather conditions, recent change in housing, Arabian breed, administration of an anthelmintic during the 7-day period prior to examination, failure to receive regular deworming, age > 10 years, and regular exercise (vs pastured at all times) were associated with increased risk of colic. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that changes in diet (particularly in type of hay fed) contribute to increased risk of colic. A regular program for administration of anthelmintics may reduce the overall frequency at which colic develops, but recent administration of anthelmintics may predispose some horses to colic. Arabian horses may have an increased risk of colic, and horses at pasture may have a decreased risk of colic.     

Factor analysis of the interrelationships between clinical variables in horses with colic

A prospective survey of horses with colic referred to the Large Animal Hospital at the Royal Veterinary and Agricultural University of Copenhagen, Denmark, was undertaken between August 1994 and December 1997. The interrelationships between 17 clinical variables were analysed using factor analysis. Factor analysis uncovers the structure of the variability in data and therefore detects multicollinearity. A total of 528 horses were admitted in the study period. Of these, 16 were excluded from the analysis as a result of miscellaneous conditions. Only 205 horses had observations for all 17 variables. Because no major change occurred in the main diagnostic categories, this population was considered as a representative subset. Factor analysis confirmed the clinical impression of correlation between variables, but the multicollinearity turned out not to be strong. Four factors were extracted, and these accounted for 51% of the total variance. The retained factors were interpreted by integrating previously reported clinical research. The first factor, which was interpreted as endotoxaemia, had high loadings on capillary refill time, mucous-membrane colour, degree of pain, heart rate, packed-cell volume and abdominal sounds. In the second factor, cecal decompression, admission month and gastric reflux had the predominant influence, and this factor was explained as cecal tympany. The third factor was simply interpreted as age because it had high loadings on gender, age and temperature. In the fourth factor, the interpretation was not straightforward, although breed had the greatest influence in the formation of this factor. Subsequently, the extracted factors were used in a logistic-regression analysis to determine their association with outcome (survival/death). The two factors interpreted as endotoxaemia and age were related to the outcome.