Prognosticating equine colic

Prospective case study of critical decision making for horses referred for treatment of colic

BACKGROUND

There is limited evidence on factors affecting critical decision making for horses with colic. This study's aim was to describe the assessment and decision making involved in horses referred for management of colic.

METHODS

An in-depth case analysis was used to document case presentation, decision making and outcomes for horses referred for colic to two UK equine veterinary practices over a 12-month period. The data recorded included previous history, presenting signs, response to treatment, case outcome and factors affecting decisions for further treatment or euthanasia.

RESULTS

Data were available for 60 cases: 55 were hospitalised for medical or surgical treatment and five horses were euthanased following initial assessment. The main factors affecting treatment decisions were severity of clinical signs (80%, 47/59), financial concerns (10%, 6/59) and ongoing health issues or previous history of colic (5%, 3/59). Factors associated with euthanasia decisions were postoperative complications (5/18), poor prognosis (4/18), deteriorating clinical signs (3/18) and financial concerns (3/18).

LIMITATION

The limited study population may affect the extent to which the findings can be generalised.

CONCLUSION

The severity of clinical signs was the key factor in treatment decision making. The main factors affecting euthanasia decisions were clinical deterioration, poor prognosis and financial constraints. These findings should be incorporated into clinical case recording to capture the multifactorial nature of decision making.

Evaluation of substance P as a biomarker for pain in equine colic

Equine colic is an important condition associated with acute abdominal pain and one of the leading causes of death in horses. As such, objectively evaluating pain is of interest for attending veterinarians. Pain scales for assessment are present, but no single pain-specific biomarker has been reported. The aim of this study was to determine if substance P (SP) could be a reliable biomarker to reflect pain and serve as a parameter to predict outcome in equine colic. The hypothesis was that horses displaying severe colic signs present with higher values of SP in contrast to those with mild colic signs. Thirty warmblood horses, aged between 3 and 20 years were recruited; evenly distributed (10 horses each) in three colic groups (mild, moderate, severe). To classify the colic signs, the horses were graded by the Equine Acute Abdominal Pain Scale (EAAPS). Clinical examination and EAAPS were performed at arrival in the hospital. Blood samples were collected four times in hourly intervals commencing from arrival. For comparison, already established parameters for prognosticating equine colic (heart rate, serum cortisol, and blood lactate concentration) were also measured. The assumption of increasing SP concentrations along with pain could not be confirmed. SP did not show any association with heart rate, cortisol, lactate, or EAAPS. Whereas the established parameters increased according to the EAAPS, SP remained stable in individual horses regardless of clinical signs, treatment, and disease progression. Consequently, SP was not a reliable parameter to reflect painful conditions or to predict outcome in equine colic.

Arterial Blood Gas, Electrolyte and Acid-Base Values as Diagnostic and Prognostic Indicators in Equine Colic

The study aimed to investigate if arterial blood analysis in conscious horses presenting with signs of colic and breathing ambient air had diagnostic or prognostic value. Arterial blood samples from 352 horses presenting with colic at a university equine referral hospital were analysed for pH, partial pressure of carbon dioxide (PaCO2), partial pressure of oxygen (PaO2), concentrations of sodium (Na+), potassium (K+), ionised calcium (Ca2+) and chloride (Cl-), actual and standardised plasma bicarbonate concentration (HCO3- (P) and HCO3- (P, st)), blood and extracellular fluid base excess (Base (B) and Base (ecf)) and anion gap (AG). Results were compared to previously reported values for healthy horses, and comparisons were made between final diagnosis, treatment and survival to hospital discharge. Significant differences were found between colic cases and healthy reference values between some primary aetiologies. Overall, surgical and non-surgical colic cases differed in Ca2+ and Cl- concentrations and Ca2+ differed between cases that survived to discharge and those that did not. PaO2 differed between small intestinal surgical cases that survived and those that did not. From these results, we developed regression models that demonstrated excellent or good predictive value in identifying the likelihood of surgical versus medical management and survival to hospital discharge.

[Evaluation of clinical examination parameters and a scoring system in equine colic as well as the assessment of their prognostic value]

SUBJECT AND AIM

In horses, colic is associated with relatively high mortality rates. Identification of parameters associated with poor outcome may aid in providing a more accurate prognosis. This study aimed to assess the early prognostic value towards survival of the horse based on parameters of the clinical examination.

MATERIAL AND METHODS

In a retrospective study (2013-2017), results of the clinical examination of horses with colic were analyzed. Obtained parameters were categorized from physiologic up to different pathophysiologic manifestations. The risk of death was calculated as odds ratios in comparison to normal values of these parameters. Individual score points were obtained and related to the respective outcome. Cut-off values for prognosis and treatment were calculated to distinguish between outcome and treatment group.

RESULTS

A total of 492 colic horses were analyzed, presenting 433 survivors (88 %). Overall, medical treatment was selected in 346 (70.3 %) horses (with 96 % survivors) and surgical treatment (laparotomy) was performed in 146 (29.7 %) horses (69.2 % survivors). An increased likelihood of the outcome "death" was found in horses aged over 20 years (OR = 5.498, p < 0.0005), with colic signs of > 6 hours duration (OR = 3.590, p = 0.035) and, also, for breeds of draft horses (OR = 8.364, p < 0.0005). Horses with significant increases in heart and respiratory rates (OR = 24.294, p < 0.0005 and OR = 20.375, p < 0.0005, respectively) and increased blood lactate concentrations (> 90 mg/dl: OR = 26.390, p < 0.0005) were more likely to succumb to the disease. However, a scoring system failed to show an association between high score points and poor prognosis.

CONCLUSION AND CLINICAL RELEVANCE

Parameters of the clinical examination as well as the history of the patient may be indicative for the patient's outcome. However, no clear-cut distinction of the evaluated parameters towards survival and treatment options was obtained. A careful investigation of the patient remains mandatory for selection of treatment and a proper assessment of prognosis.

Higher body mass index may increase the risk for the development of incisional complications in horses following emergency ventral midline celiotomy

BACKGROUND

Obesity is common in the equine population and it has been associated with increased surgical morbidity and mortality in humans. The effect of increased body mass index (BMI) on the incidence of surgical site infections has not been investigated in horses.

OBJECTIVES

To determine whether horses with increased body fat, as estimated by BMI, are more likely to develop post-operative complications, particularly incisional complications, following emergency ventral midline celiotomy.

STUDY DESIGN

Retrospective, multi-institutional clinical study.

METHODS

Medical records of horses >2 years old presenting with colic that underwent ventral midline celiotomy between January 2010 and September 2018 with follow-up of a minimum of 30 post-operative days were reviewed. Extracted data included signalment, operative details and outcome. BMI was calculated by dividing the patient's weight (kg) by the withers height squared (m² ).

RESULTS

In all, 287 horses fit inclusion criteria. Incisional complication prevalence was 23.7%. Horses with incisional complications had a higher BMI (median 203.6 kg/m² , IQR = 191.5-217.4) compared with those without (median 199.1 kg/m² , IQR = 184.7-210.2) (P = .03). Multi-variable analysis of the effects of age, sex, breed and presence of metabolic disease on the association between BMI and risk of incisional complications, identified a tendency towards increased risk with a higher BMI, but statistical significance decreased to P = .07. Breed had an association with BMI (P < .01), but not with incisional complication risk.

MAIN LIMITATIONS

BMI as an estimate of body fat has limitations. Retrospective studies with reliance on owners reporting data and complete medical records is imperfect. When the data were subjected to multi-variable analysis, the trend towards an increased incidence of incisional complications in horses with higher BMI persisted but it was not statistically significant.

CONCLUSION

Higher BMI may increase the risk for the development of incisional complications in horses following emergency ventral midline celiotomy.

Serum amyloid A and plasma fibrinogen concentrations in horses following emergency exploratory celiotomy

BACKGROUND

Acute-phase proteins may help assess the nature and severity of lesions and outcome in horses undergoing colic surgery.

OBJECTIVES

To compare serum amyloid A and plasma fibrinogen concentrations ([SAA] and [fibrinogen]) in the immediate post-operative period after exploratory celiotomy and determine their value in assessment of post-operative complications and survival to discharge.

STUDY DESIGN

Observational study.

METHODS

This study included horses over 1 year of age undergoing exploratory celiotomy. Surgical procedures, lesions, post-operative care, complications and survival to discharge were recorded. [SAA] and [fibrinogen] were measured prior to surgery and 5 days post-operatively. Statistical analyses included Yate's Chi-square test, linear mixed effects model, Mann-Whitney U test and logistic regression.

RESULTS

Of 300 horses, 52.0% developed post-operative complications and 83.7% survived to discharge, with significantly reduced chance of survival in horses that developed post-operative complications (P<0.01). Median [SAA] at days 1, 2, 3, 4 and 5 and median [fibrinogen] at days 3, 4 and 5 were significantly different between horses that did and did not develop post-operative complications (P<0.05). Median [SAA] at days 1, 4 and 5 were significantly different between horses that did and did not survive to discharge (P<0.05). Logistic regression revealed post-operative complications to be associated with strangulating lesions (OR 2.35, 95% confidence interval [CI] 1.41-3.91, P≤0.001) and higher [fibrinogen] at admission (OR 1.21, 95% CI 1.00-1.45, P<0.05), and survival to discharge to be associated with lower [SAA] at 5 days post-operatively (OR 0.965, 95% CI 0.94-0.99, P = 0.002).

MAIN LIMITATIONS

A large variety of lesions and complications prevented detailed analysis of associations between inflammatory markers, lesions and complications.

CONCLUSIONS

Horses that develop post-operative complications have acute-phase responses of greater magnitudes and durations compared with those that do not develop complications. This is also seen in horses that do not survive to discharge. Measuring [SAA] daily and [fibrinogen] at admission, may help predict the development of post-operative complications.

Prognostic Value and Development of a Scoring System in Horses With Systemic Inflammatory Response Syndrome

Background

Despite its widespread use in equine medicine, the clinical value of the systemic inflammatory response syndrome (SIRS) concept in horses remains unknown.

Objectives

To study the prognostic value of measures of SIRS in horses and identify the best model of severe SIRS to predict outcome.

Animals

A total of 479 consecutive adult horse emergency admissions to a private primary referral practice.

Methods

Prospective observational study. All adult horses admitted for emergency treatment over the study period were included. Multivariate logistic regression and stepwise model selection were used.

Results

Each of the 4 SIRS criteria was associated with outcome in this population. Thirty‐one percent of emergency cases had 2 or more abnormal SIRS criteria on admission and were defined as SIRS cases. SIRS was associated with increased odds of death (odds ratio [OR] = 8.22; 95% CI, 4.61–15.18; P < .001), an effect mainly found for acute gastrointestinal cases. SIRS cases were assigned a SIRS score of 2, 3, or 4, according to the number of abnormal SIRS criteria fulfilled on admission, and SIRS3 and SIRS4 cases had increased odds of death compared to SIRS2 cases (OR = 4.45; 95% CI, 1.78–11.15; P = .002). A model of severe SIRS including the SIRS score, blood lactate concentration, and color of the mucous membranes best predicted outcome in this population of horses.

Conclusions and Clinical Importance

Systemic inflammatory response syndrome is associated with an increased risk of death in adult horses presenting with acute gastrointestinal illnesses. The model of severe SIRS proposed in this study could be used to assess the status and prognosis of adult equine emergency admissions.

Veterinary practitioners' selection of diagnostic tests for the primary evaluation of colic in the horse

The aim of this study was to survey veterinary practitioners’ selection of diagnostic tests for horses with clinical signs of abdominal pain. A questionnaire was distributed to veterinary surgeons involved in the primary evaluation of horses with abdominal pain, including the respondent's demographics, selection of diagnostic tests and factors affecting decision-making. Data analysis included descriptive analysis, categorisation of free text and simple univariable correlations to explore the relationships between independent variables and the relative self-estimated frequency that diagnostic tests were performed. A total of 228 responses were analysed. Participants worked in mixed practice (55.7 per cent), first opinion equine (22.8 per cent), first and second opinion equine (17.9 per cent) and referral practice (3.1 per cent). The majority (48.2 per cent, 105/218) were very confident managing a colic case (confidence level 4/5). The most frequently used diagnostic tests were ‘response to analgesia’ (87.2±24.0 per cent cases), rectal examination (75.9±21.2 per cent) and nasogastric intubation (43.8±27.6 per cent). Approach varied between practitioners, and for all diagnostic tests with frequency of use ranging from 0 to 100 per cent of cases. ‘Risk to personal safety’ was the most common reason for not using rectal examination. Practitioner's opinion of their confidence level in managing a colic case was associated with how frequently they used different diagnostic tests. There was marked variation in practitioners’ approaches, highlighting the need for further evidence to support decision-making.

Evaluation of plasma muscle enzyme activity as an indicator of lesion characteristics and prognosis in horses undergoing celiotomy for acute gastrointestinal pain

Background

In horses undergoing celiotomy for acute gastrointestinal pain, identification of variables correlating with lesion severity and location, and survival provide veterinarians and owners with information that aids in making informed decisions regarding appropriate treatment. Muscle enzyme activity is often increased in horses undergoing celiotomy for acute gastrointestinal pain and it is not known if muscle enzyme activity increase is specific to lesion type or impacts prognosis for survival. The objective of this study was to evaluate the relationship of pre-operative increase in muscle enzyme activities with intestinal lesion characteristics, specifically lesion location (large versus small intestine) and whether it was strangulating versus nonstrangulating, and case survival in horses undergoing celiotomy for acute gastrointestinal pain.

Methods

Records of 241 horses undergoing exploratory laparotomy for colic were reviewed retrospectively. Evaluation of preoperative plasma aspartate aminotransferase (AST), creatine kinase (CK), sorbitol dehydrogenase (SDH), and gamma-glutamyltransferase (GGT) activities, fibrinogen and glucose concentrations, and hematocrit (HCT) and their association with gastrointestinal lesion characteristics and survival was performed.

Results

Pre-operative increase in plasma CK and AST activity, and HCT and decrease in plasma bilirubin concentration were significantly associated with presence of lesions resulting in intestinal ischemia. Increase in plasma CK activity and HCT were significantly associated with a decreased probability of survival to hospital discharge. Plasma GGT and SDH activity, and glucose and fibrinogen concentration were not significantly associated with survival or severity of disease in multivariate analysis.

Conclusions

Plasma muscle enyzme activity may be useful as a prognostic indicator in equine colic cases. Given that increases in plasma CK and AST activity were significantly associated with nonsurvival and the presence of intestinal ischemia, preoperative increase in these enzyme activities could assist in identification of disease severity and prognosis of horses undergoing celiotomy for acute gastrointestinal pain. Further study is indicated to elucidate the etiology of increased muscle enzyme activity in horses with surgical colic disease observed in this preliminary study.

Surgical treatment of equine colic - a retrospective study of 297 surgeries in Norway 2005-2011

BACKGROUND

Colic, defined as pain originating from the abdomen, is a common condition in horses. Most of the cases resolve spontaneously or after medical treatment, but a few require surgical treatment. Surgical treatment of colic in horses is resource-demanding and expensive, and information on prognosis is therefore important for both owners and surgeons. In the present study, surgical cases in two equine hospitals in Norway between 2005 and 2011 were reviewed. The aim of the study was to describe associations between prognostic indicators, diagnoses and short term survival by use of random effects logistic regression.

RESULTS

In the present study, 162 out of 297 (54.5%) surgeries resulted in the horse being discharged from the hospital. Excluding cases euthanized during surgery, the overall short-term survival was 74.0% (162 out of 219 surgeries). Seventy-eight (26.3%) of the horses were euthanized during surgery, due to grave or poor prognosis. In univariable analyses, duration of colic signs, heart rate, capillary refill time, mucosal membrane appearance, intestinal sounds, affected gastrointestinal segment, hematocrit, intestinal resection, hospital and surgeon board-certification had P-value <0.20 and were assessed in multivariable analyses. Respiration rate, rectal temperature and lactate in blood also had univariable P <0.20, but were left out from multivariable analyses due to too high levels of missing values. A random effect of primary surgeon was included and breed, sex and age were tested in multivariable analyses as possible confounders; and hospital was included to control for hospital routine differences. In the final multivariable model the variables mucosal membrane appearance, affected gastrointestinal segment and surgeon board-certification significantly influenced survival. The random surgeon effect was not significant.

CONCLUSIONS

The present study showed that prognostic parameters and diagnoses of surgical treatment of horses with colic in Norway are in accordance with reports from other parts of the world. The significant effect of board-certification of surgeon is not reported in previous studies. The general short-term survival rate was somewhat lower than reported in other studies, partly due to more horses being euthanized intraoperatively in the present study. This might be because of economical or animal welfare reasons.