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.     

Plasma serotonin in horses undergoing surgery for small intestinal colic

This study compared serotonin concentrations in platelet poor plasma (PPP) from healthy horses and horses with surgical small intestinal (SI) colic, and evaluated their association with postoperative ileus, strangulation and non-survival. Plasma samples (with EDTA) from 33 horses with surgical SI colic were collected at several pre- and post-operative time points. Serotonin concentrations were determined using liquid-chromatography tandem mass spectrometry. Results were compared with those for 24 healthy control animals. The serotonin concentrations in PPP were significantly lower (P < 0.01) in pre- and post-operative samples from surgical SI colic horses compared to controls. However, no association with postoperative ileus or non-survival could be demonstrated at any time point. In this clinical study, plasma serotonin was not a suitable prognostic factor in horses with SI surgical colic.     

Feeding practices associated with colic in horses.

OBJECTIVE: To determine whether specific feeding practices were associated with development of colic in horses. DESIGN: Prospective matched case-control study. ANIMALS: 364 horses examined by veterinarians in private practice in Texas because of colic (cases; n = 182) or any other reason (controls; 182). PROCEDURE: Participating veterinarians were sent forms at the beginning of the study to collect information on signalment, feeding management practices, farm management practices, and preventive medical treatments. Case and control horses were compared by use of conditional logistic regression to identify factors associated with colic. RESULTS: Risk factors for colic were a recent change in batch of hay, decreased exposure to pasture, a recent change in type of grain or concentrate fed, feeding > 2.7 kg (6 lb) of oats/d, feeding hay from round bales, and Thoroughbred breed. Recent anthelmintic administration decreased the risk of colic. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain changes in diet (eg, change in batch of hay, change in type of grain or concentrate, feeding hay from round bales) and management (eg, decreased availability of pasture) increase the risk of colic in horses.     

Postoperative pharmacokinetics of meloxicam in horses after surgery for colic syndrome

NSAID s are often used in horses with colic syndrome during the postoperative period, due to their ability to contrast endotoxemia and to promote an analgesic and anti‐inflammatory effect. As the pharmacokinetics of a drug are often modified in unhealthy animals compared to healthy subjects, the aim of this study was to evaluate the pharmacokinetic profile of meloxicam after i.v. administration in horses undergoing laparotomy for colic syndrome. Eight horses received 0.6 mg/kg of meloxicam i.v. towards the end of surgery. Blood samples were taken at scheduled time points during the following 24 hr. The serum concentration of the drug was determined by HPLC . Terminal half‐life (6.88 ± 2.96 hr), volume of distribution at steady‐state (186.53 ± 61.20 ml/Kg) and clearance (27.91 ± 5.72 ml kg^?1 hr^?1) were similar to those reported in literature for healthy horses. This result suggests that no adjustment of the approved dose should be necessary when meloxicam is used to treat horses in the immediate postoperative period after surgery for colic syndrome.     

Extraperitoneal incisional abscess formation after colic surgery in 3 horses

In this article we report 3 horses that developed an extraperitoneal abscess after colic surgery at the incision site. All 3 horses presented with nonspecific clinical signs and extraperitoneal abscess was diagnosed from ultrasound evaluations and cytological examination of abscess aspirates. One horse developed dehiscence of the incision after drainage of the abscess through the incision. In 2 cases a small standing paramedian incision was performed through which the abscess was drained and lavaged; complete resolution of the abscess and healing of the incision was achieved in both cases. Extraperitoneal abscess is a previously unreported incisional complication after colic surgery in horses. Early and careful ultrasonographic examination of the abdominal incision is required for diagnosis in cases with nonspecific clinical signs. A paramedian incision through the rectus abdominis muscle into the abscess cavity permitted adequate drainage and debridement of the abscess in 2 cases.     

Risk factors associated with colic in horses

Many factors have been identified as risk factors for colic in horses in several epidemiological studies. The aim of our paper was to review the results of 12 epidemiological studies, in order to assess the impact of each risk factor for colic. According to the literature, the factors that increase the risk of colic are feeding practices (type and quality of food, type and changes of feeding), the intrinsic factors of horses (sex, age and breed), management (type and changes of housing and activity), medical history (a previous colic, administration of a medical treatment) and parasite control (the presence of worms and type of deworming program). Several individual factors were incriminated as risk factors by all the studies. Nevertheless, the different studies did not always agree on the role of other risk factors. The conclusions were tightly related to several criteria in the selection of the study population, like the type of the epidemiological study, the number and the origin of horses included and the location of the study.     

The coagulation system in horses with colic

Colic in horses very often induces changes in the coagulation system causing the development of disseminated intravascular clotting. It is promoted by blood concentration and an increase in exposition of coagulation activators with a simultaneous decrease in coagulation inhibitors activity, mainly antithrombin III. Progressing blood platelets aggregation supports production of microthromboses and plugging capillary vessels. The progression of this processes causes complications in basic disease and becomes the reason for therapeutic failure. Determination of coagulation system indexes such as the number of platelets, prothrombin time, activated partial thromboplastin time, thrombin time, concentration of fibrinogen and fibrinogen degradation products, and D-dimmer and antithrombin III contents enables diagnosis and facilitates appropriate therapy of colic in horses.     

Salmonella shed by horses with colic

Salmonella was isolated from 13 of 100 colicky horses admitted to a referral hospital. Seven horses were shedding the microorganism at or soon after hospital admission. A unique serotype was introduced into the hospital by a horse not shedding Salmonella at admission. It was concluded that 8 horses were infected before admission. Whether the remaining 5 horses were infected before or after admission could not be determined. Salmonella senftenberg was the most commonly isolated serotype from colicky horses and from horses with salmonellosis that were not colicky on hospital admission during the survey period. This organism was rarely isolated at the hospital before initiation of this survey.     

Use of web-based data collection to evaluate analgesic administration and the decision for surgery in horses with colic

REASONS FOR PERFORMING STUDY: There is no current veterinary information with regard to data entry on a website. We therefore completed a prospective study on use of analgesics in relation to the need for abdominal surgery using a web-based survey instrument. OBJECTIVES: To establish an internet-based data entry system that could be used to record prospective data on horses with colic. HYPOTHESIS: Failure of horses to respond to the initial administration of an analgesic is an indicator of the need for abdominal surgery. METHODS: A survey was developed to determine if the response to administration of an analgesic during a veterinarian's first examination of a horse with colic was related to the need for surgery. Veterinarians were contacted via AAEP and ECN listservs requesting submission of cases using a log-in system at a data entry website. The survey was completed by submission of a data entry page. RESULTS: Twenty-seven veterinarians submitted details of 119 cases of colic, 28 of which required surgery. The need for surgery was significantly associated with moderate or severe pain observed during the first examination compared to mild or no pain, and with constant pain or return of pain after administration of one or more analgesics and the need to administer a second analgesic treatment. Abnormal findings on rectal examination were not associated with the need for surgery, whereas total absence or decrease of intestinal sounds was significantly related to the odds that surgery was needed. The web-based data collection was successful in collecting all data points on the survey for each case. CONCLUSIONS: This study reinforced veterinarians' use of response to therapy as a way to determine the need for abdominal surgery. POTENTIAL RELEVANCE: When a specific diagnosis has not been made, lack of response or resumption of colic after analgesic administration should be considered as an indicator of the need for surgery. Web-based collection of data allows veterinary practitioners to participate in clinical research by providing prospective data.     

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.     

Changes in coagulation and markers of fibrinolysis in horses undergoing colic surgery

Activation of coagulation can be frequently found in horses with colic. However, it has also been demonstrated as a sequela of surgical trauma alone in humans. The purpose of the present study was to determine changes in coagulation and fibrinolysis in horses that underwent colic surgery and to evaluate whether these changes were secondary to the colic or the surgery and wound healing. Thirty horses that underwent colic surgery with uncomplicated recovery were included. Ten horses with a Forssell's procedure served as control group with a standardized surgical trauma. Besides daily physical examinations during the observation period of 10 days, activated partial thromboplastin time (aPTT), prothrombin time and thrombin time as well as fibrin monomer (FM), D-Dimer (DD) and antithrombin (AT) III were determined. Compared with the control group the aPTT was the only standard coagulation test that was significantly prolonged before and after the event of colic surgery. After surgery, hyperfibrinogenaemia occurred in all groups. In colic groups FM and DD concentrations were within reference range at admission,and were significantly greater than in control horses after surgery. AT III activity decreased after colic surgery, but did not change in the control group. It was concluded that an activated coagulation state after colic surgery has to be expected, resulting not only from the colic disease, but also from the event of surgery.     

Hypoxaemia during anaesthesia in seven horses with colic

Anaesthetic records of horses with colic anaesthetised between June 1987 and May 1989 were reviewed. pH and blood gas analyses were performed during 157 operations from which the horses were allowed to recover. A PaO₂ of 8.0 kPa or less was measured during anaesthesia in seven of these horses. The horses were of different breeds, ages and sexes. Anaesthesia was induced with xylazine, guaifenesin and ketamine in four horses and with xylazine, guaifenesin and thiobarbiturate in three horses. Anaesthesia was maintained with inhalation anaesthetic agent and oxygen: isoflurane in five horses, halothane in one horse, and initially halothane but later isoflurane in one horse. Systolic arterial pressures during anaesthesia ranged from 80 to 150 mmHg, diastolic arterial pressures were between 60 and 128 mmHg, and heart rates were between 28 and 44 beats /min. Controlled ventilation was initiated at the start of anaesthesia. PaCO₂ exceeded 6.7 kPa in three horses but was subsequently decreased by adjustment of the ventilator. PaO₂ of 8.0 kPa or less was measured during early anaesthesia, with one exception, and persisted for the duration of anaesthesia. The horses' inspired air was supplemented with oxygen during recovery from anaesthesia, at which time measurement of blood gases in three horses revealed no increase in PaO₂. Recovery from anaesthesia was uneventful. The surgical problems involved primarily the large intestine in five horses and the small intestine in two horses. Six horses were discharged from the hospital alive; one horse was reanaesthetised later the same day and destroyed without regaining consciousness. We concluded that none of the objective values recorded during the pre-anaesthetic evaluation could have been used to predict the complication of intraoperative hypoxaemia. We observed that once hypoxaemia developed it persisted for the duration of anaesthesia and even into the recovery period when the horses were in lateral recumbency and regaining consciousness. We assume that the altered metabolism from anaesthetic agents and hypothermia combined with adequate peripheral perfusion contributed to the lack of adverse consequences in six of the horses. The contribution of hypoxaemia to the deteriorating condition of the seventh horse is speculative.     

Plasma colloid osmotic pressure and total protein in horses during colic surgery

OBJECTIVE: To assess the changes in colloid osmotic pressure (COP) in horses undergoing surgery for colic. STUDY DESIGN: Prospective clinical evaluation. ANIMALS: Twenty-nine adult horses presented for emergency laparotomy. METHODS: Horses were premedicated with intravenous (IV) xylazine and anesthesia was induced with ketamine, diazepam and guaifenesin and was maintained with isoflurane as required. Lactated Ringer's solution (LRS) was given to all horses during anesthesia. Blood was collected in heparin before, and every 30 minutes during, anesthesia to measure COP, total protein concentration (TP), osmolality, packed cell volume, electrolytes, glucose and lactate. In addition, COP was estimated using different formulas previously described for horses. RESULTS: Before anesthesia, COP and TP were 18.7 +/- 2.2 mmHg (2.49 +/- 0.29 kPa) and 6.3 +/- 0.7 g dL(-1), respectively. The horses received a mean +/- SD of 19.5 +/- 3.9 mL kg(-1) hour(-1) (range 15-25 mL kg(-1)hour(-1)) of LRS during anesthesia. The COP and TP decreased linearly (R(2) = 0.99, p < 0.01) during anesthesia and reached the lowest point at the end of anesthesia with a COP of 11.6 +/- 1.6 mmHg (1.55 +/- 0.21 kPa) and TP of 4.4 +/- 0.4 g dL(-1). The Pearson correlation coefficient for COP versus TP was r(2) = 0.78. Calculation of COP from TP concentrations showed that two formulas could predict COP to within 1 mmHg (0.13 kPa) (Thomas & Brown 1992; Boscan et al. 2007). CONCLUSIONS AND CLINICAL RELEVANCE: Colloid osmotic pressure, like TP, decreased greatly over the course of crystalloid fluid infusion during anesthesia for laparotomy in horses with colic. This change may predispose the animal to tissue edema with subsequent morbidity.     

Radiographic parameters for diagnosing sand colic in horses

Background

Ingestion of sand can cause colic, diarrhoea and weight loss in horses, but these signs are unspecific and can have many other causes. The amount of sand that induces disease may vary between individuals. To avoid over-diagnosing, it is important to determine the amount of sand that can be found in horses without clinical signs of gastrointestinal disease. The aim of this study was to use previously suggested parameters for establishing a radiographic diagnosis of sand colic, and compare these findings between a sand colic group and a control group.

Methods

Abdominal radiographs were obtained in 30 horses with a complaint unrelated to the gastrointestinal tract. In addition, archived abdominal radiographs of 37 clinical cases diagnosed with sand impaction were investigated. The size of the mineral opacity indicative of sand in the abdomen was measured and graded according to a previously published protocol based on height and length. Location, homogeneity, opacity and number of sand accumulations were also recorded.

Results

Twenty out of 30 control horses (66%) had one or more sand accumulations. In the present study; height, length and homogeneity of the accumulations were useful parameters for establishing a diagnosis of sand colic. Radiographically defined intestinal sand accumulation grades of up to 2 was a common finding in horses with no clinical signs from the gastrointestinal tract whereas most of the clinical cases had much larger grades, indicating larger sand accumulations.

Conclusion

Further work to establish a reliable grading system for intestinal sand content is warranted, but a previously proposed grading system based on measurements of height and length may be an alternative for easy assessment of sand accumulations in the meantime. The present study indicates that a grade 1 – 2 sand accumulation in the intestine is a frequent finding in horses. When working up a case with clinical signs from the gastrointestinal tract, one or more accumulations of this grade should not be considered the cause until other possibilities have been ruled out.     

Histologic findings in the gastrointestinal tract of horses with colic

Thirty horses were admitted to the University of Georgia Veterinary Medical Teaching Hospital with colic severe enough to warrant surgery and/or euthanasia. Gastrointestinal tracts of these 30 horses were histologically examined for morphologic changes. The horses were grouped according to cause of the colic (ie, simple obstruction, strangulation obstruction, thromboemboli, and inflammation). Lesions were graded as to severity, and grade scores were correlated with survival or nonsurvival. Mucosal changes developed distal and proximal to the primary lesion site and, although there were some differences between groups, changes characteristic of ischemia were common to all groups. The predictability of lesion grades of 2 or higher for nonsurvivability (90%) indicates that intestinal biopsy may have prognostic value in the postsurgical evaluation and management of equine colic.     

Nutrition for critical gastrointestinal illness: feeding horses with diarrhea or colic.

Horses with GI diseases such as colic and diarrhea are often intolerant of adequate enteral nutrition. Nutritional intervention should be an early part of therapeutic management in such cases. Protein and energy malnutrition in critically ill horses can have deleterious effects, including poor wound or incisional healing, reduced immunity, and weight loss. Early enteral or parenteral support should be provided to supply resting DE requirements in the equine ICU.     

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.     

Surgical colic in racing endurance horses

A retrospective study was performed of horses that developed colic during endurance racing, and subsequently required surgery. Fifteen horses met the inclusion criteria, of which 13 (87%) had small intestinal volvulus. Nine of the 15 horses (60%) had a small intestinal resection and anastomosis performed. Post operative ileus, particularly in those horses that had a resection performed, was a common complication. Eleven of the 15 (73%) survived, and 4 (27%) have since raced.