Risk factors for surgical site infection following laparotomy: Effect of season and perioperative variables and reporting of bacterial isolates in 287 horses

Ultrasonographic findings of fluid accumulation and hyperechogenic spots suggestive of surgical site infection following laparotomy for colic in horses

BACKGROUND

The aim of this study was to compare ultrasonographic findings of the ventral midline incision after exploratory laparotomy for colic in horses with and without surgical site infection (SSI).

METHODS

Ultrasonographic examination of the surgical wound was performed on postoperative day 5 (D5) and day 10 (D10) to assess the presence of fluid accumulation, suture sinus formation, hyperechogenic spots and fistulous path. Clinical evaluation of the wound was used to classify horses with and without SSI. The accuracy, sensitivity, specificity and positive and negative predictive values of the ultrasonographic findings were then calculated. Multivariable logistic regression analyses were performed with SSI as a dependent variable and age, sex, breed and ultrasonographic findings as independent variables after univariate and collinearity analyses.

RESULTS

Twenty-nine of the 84 horses examined had an SSI. Detection of fluid accumulation and hyperechogenic spots increased the odds for SSI at D5 (odds ratio [OR]: 4.99, 95% confidence interval [CI]: 1.53-16.33, p = 0.008; OR: 10.78, 95% CI: 1.75-26.59, p = 0.01, respectively) and D10 (OR: 11.51, 95% CI: 2.39-55.47, p = 0.002; OR: 12.34, 95% CI: 3.45-44.15, p < 0.001, respectively).

LIMITATION

Ultrasonographic images were taken only on the longitudinal section.

CONCLUSION

Ultrasonographic examination is helpful in evaluating the surgical incision after laparotomy, with the detection of fluid accumulation and hyperechogenic spots surrounding the sutures being strongly related to SSI.

The Effects of Antimicrobial Protocols and Other Perioperative Factors on Postoperative Complications in Horses Undergoing Celiotomy: A Retrospective Analysis, 2008-2021

Recognition of antimicrobial resistance in equine practice has increased over the past decade. The objective of this study was to provide an updated retrospective review of antimicrobial regimens in one tertiary referral hospital and to evaluate the association with postoperative complications. A secondary objective was to evaluate other perioperative factors including surgical procedure, anesthetic and recovery parameters, and the effect of perioperative medications on complications and outcomes. A computerized search of medical records was performed to identify horses undergoing exploratory celiotomy from 1 January 2008 to 31 December 2021. A total of 742 celiotomies were performed (608 completed, 134 terminated intraoperatively). Factors recorded were evaluated using logistic regression for the presence of either incisional infection, postoperative ileus, or other complications postoperatively. Antimicrobial type or timing (pre-, intra-, or postoperative) were not associated with decreased risk of incisional infection or postoperative ileus; however, the duration of NSAID use was positively associated with incisional infection (OR 1.14 per day). Lidocaine and alpha-2-agonist administration postoperatively were also associated with increased incidence of postoperative ileus (OR 21.5 and 1.56, respectively). Poor recovery quality (OR 4.69), the addition of other antimicrobials besides penicillin/gentamicin postoperatively (OR 3.63), and an increased number of different NSAID classes used (OR 1.46 per additional) were associated with other complications. Implementation of enterotomy was associated with decreased risk of other complications (OR 0.64). These findings provide an updated summary of factors associated with postoperative complications in horses undergoing celiotomy.

Long-term outcome after colic surgery: retrospective study of 106 horses in the USA (2014-2021)

Objective

To determine long-term survival rate, defined as survival to 1 year after discharge from the hospital, and rate of return to prior athletic, breeding, or other function in horses undergoing colic surgery at the first presentation at one referral hospital in the Pacific northwest region of the United States.

Procedures

Records were reviewed for all horses that underwent colic surgery between October 2014 and October 2021. Owners of horses that survived to discharge were contacted to obtain follow-up information via internet-based questionnaire or telephone interview. The percentage of horses that survived to 1 year after discharge, rates of return to function, and complications occurring after hospital discharge were determined. The possible association of patient signalment, lesion type, and surgical procedures with long-term survival was examined with Chi-square and Fisher's exact tests. Overall satisfaction was indicated on a scale of 1 (unsatisfied) to 5 (very satisfied).

Results

Of 185 horses that underwent surgical intervention for colic and met the inclusion criteria, 134 horses recovered from anesthesia, with 106 of these recovered horses (79.1%) surviving to discharge. Of the 71 horses for which follow-up information was obtained, 61 horses survived to 1 year after discharge (long-term survival rate of 85.9%). There were no demographic, lesion type, or surgical procedure variables significantly associated with long-term survival. Prior to surgery, 59/71 horses (83.1%) were engaged in some type of athletic activity. After surgery, 44/61 horses (72.1%) were reported to be athletically active. Only one horse was reported to be retired from athletic activity as a direct result of a complication from surgery. Overall satisfaction with the decision to proceed with colic surgery was rated by all respondents as 4 or 5.

Conclusions and clinical relevance

The long-term survival for this sample of horses was similar to previously published reports of long-term survival after colic surgery. Horses that survived to hospital discharge were highly likely to remain alive and be athletically active 1 year later. There were no factors related to the signalment of the horse, the specific cause of colic, or the surgical procedures performed that were significantly associated with likelihood of survival.

Benefits of cyanoacrylate mesh closure following exploratory laparotomy in horses

BACKGROUND

Skin closure of laparotomy incisions using topical 2-octyl cyanoacrylate (2-OCA) mesh provides a secure bactericidal barrier in humans, which may reduce the risk of postoperative incisional complications. However, the benefits of using this mesh have not been objectively assessed in horses.

METHODS

From 2009 to 2020, three methods of skin closure were used following laparotomy for acute colic, including metallic staples (MS), suture (ST) and cyanoacrylate mesh (DP). The closure method was not randomised. Owners were contacted 3 months or more after the surgery to record any postoperative complications that occurred. For each method of closure, the rates of surgical site infection (SSI) and herniation were recorded, as well as surgical time and treatment costs, including those for incisional complications. Chi-square testing and logistic regression modelling were used to assess differences between the groups.

RESULTS

A total of 110 horses were recruited (45 in the DP group, 49 in the MS group and 16 in the ST group) The overall rate of SSI was 15.5%, with rates of 8.9%, 18.4% and 25% for the DP, MS and ST groups, respectively (p = 0.23). In addition, incisional hernias developed in 21.8% of cases, with 8.9%, 34.7% and 18.8% of horses in the DP, MS and ST groups, respectively, being affected (p = 0.009). The median total treatment cost did not differ significantly between groups (p = 0.47).

LIMITATION

This was a retrospective study with non-randomised choice of closure method.

CONCLUSIONS

No significant differences in the rate of SSI or overall cost wwere demonstrated between treatment groups. However, MS was associated with a higher rate of hernia formation than DP or ST. Despite increased capital cost, 2-OCA proved to be a safe skin closure method in horses and was no more expensive than DP or ST by the time visits to remove sutures/staples and treat infections were factored in.

Basic Postoperative Care of the Equine Colic Patient

The 3 time periods around colic surgery (preoperative, operative, and postoperative) are all critical to successful outcomes. Although much focus is often paid to the first 2 time periods, the importance of sound clinical judgment and rational decision-making in the postoperative period cannot be overstated. This article will outline the basic principles of monitoring, fluid therapy, antimicrobial therapy, analgesia, nutrition, and other therapeutics routinely used in patients following colic surgery. Discussions of the economics of colic surgery and expectations for normal return to function will also be included.

Current Antimicrobial Use in Horses Undergoing Exploratory Celiotomy: A Survey of Board-Certified Equine Specialists

In the past decade, there has been a considerable increase in the recognition of antimicrobial resistance in equine practice. The objective of this study was to survey the current clinical use of antimicrobials for a commonly performed surgical procedure (exploratory celiotomy) with the goal of understanding how recent literature and changes in microbial resistance patterns may have impacted antimicrobial selection practices. An electronic survey was distributed to veterinary professionals within the American College of Veterinary Internal Medicine (ACVIM) and the American College of Veterinary Surgery (ACVS). A total of 113 completed surveys were returned. Practitioners reported antimicrobials were most frequently given 30-60 min preoperatively (63.1%). Two antimicrobial classes were typically administered (95.5%), with gentamicin (98.2%) and potassium penicillin (74.3%) being the most common. Antimicrobials were typically not re-dosed intraoperatively (78.6%). Factors that affected overall treatment length postoperatively included resection (81.4%), bloodwork (75.2%), enterotomy (74.3%), fever (85.0%), incisional complications (76.1%), and thrombophlebitis (67.3%). The most common duration of antimicrobial use was 1-3 d for non-strangulating lesions (54.4% of cases) and inflammatory conditions such as enteritis or peritonitis (50.4%), and 3-5 d for strangulating lesions (63.7%). Peri-incisional and intra-abdominal antimicrobials were used by 24.8% and 11.5% of respondents, respectively. In summary, antimicrobial usage patterns were highly variable among practitioners and, at times, not concordant with current literature.

Changes in Perioperative Antimicrobial and Anti-Inflammatory Drugs Regimens for Colic Surgery in Horses: A Single Center Report

Simple Summary

The administration of postoperative anti-inflammatory and antimicrobial drugs after colic surgery is based on an empirical approach, and for this reason, in recent years, it has been questioned. Recent guidelines recommend that antimicrobials should be administered for the shortest effective period possible. The use of non-steroidal anti-inflammatory drugs is also discussed given the side effects especially on the gastrointestinal tract. Consequently, the antimicrobial and anti-inflammatory drugs administration in horses has changed in our practice over the years to modulate therapies according to the postoperative complications that eventually arise. The description of these changes and the reasons behind them can help define an appropriate stewardship. Over the years, the administration of postoperative antibiotics has been limited, and treatments have been started only in case of complications that justified their use. As for anti-inflammatories, there was a variation of dosages of flunixin meglumine and the addition of new types of anti-inflammatories, both non-steroidal anti-inflammatory drugs and corticosteroids. These changes in prophylaxis protocols were not associated with an increase in postoperative complications.

Abstract

Reducing postoperative incisional infection is the main reason to administer postoperative antimicrobials (AMD) after emergency laparotomy in horses, while reducing inflammation and providing analgesia are the reasons to administer anti-inflammatory drugs (AID). The basis for postoperative AMD and AID administration is empirical and only recently has been questioned. Empirical approaches can be changed, and these changes, along with the description of their outcomes, can help produce appropriate stewardship. The aim of this study is to report the changes in AMD and AID regimens in horses undergoing emergency laparotomy at a referral teaching hospital between 2017 and 2021. Signalment, pathology, surgery, prophylactic AMD and AID administration were obtained from the medical records. Difference in AMD and AID regimens throughout the study period were also reported. In 234 postoperative records considered, ninety-two horses received prophylactic AMD, while 142 received pre-operative antimicrobials only. There was a progressive change in regimens throughout the years, increasing the number of AID molecules used. AMD and AID administration in horses has changed in our practice over the years to modulate therapies according to the postoperative complications that eventually arise. In this study, horses not receiving postoperative routine AMD treatment did not show an increased incidence of complications.

Antimicrobial Resistance of Coagulase-positive Staphylococcus Isolated From Healthy Crioulo Horses and Associated Risk Factors

Antimicrobial resistance (AMR) is a global concern that must be addressed from a one health perspective. Horses are companion animals and their contact with humans facilitates exchange of resistant bacteria. This study aimed to evaluate AMR of coagulase-positive Staphylococcus (CoPS), including Staphylococcus aureus, isolated from healthy Crioulo horses. Swab samples from nostrils (n = 214) and skin (n = 107) of 107 horses from Porto Alegre, South Brazil, were used for CoPS isolation. The isolates were evaluated for AMR and a multivariate logistic regression was applied to identify the risk factors associated to this outcome, using information on horses' management and installations where they were maintained. A total of 143 CoPS were isolated from 79 horses (73.8%), of which 8 (5.6%) were S. aureus. The isolates showed resistance to seven of 10 tested antimicrobials and 38.5% (55/143) of them were resistant to at least one antimicrobial. One isolate (0.7%; 1/143) was classified as multidrug-resistant. Regarding S. aureus, 62.5 % (5/8) showed AMR, but none were methicillin-resistant. The risk factors associated with CoPS' antimicrobial resistance were lower frequency of bed changing (OR = 6.40; P = .001) and nonaccumulation of bed materials (OR = 3.47; P = .002). The results point that healthy horses have antimicrobial-resistant CoPS and S. aureus in their microbiota, which may be of concern for animal and human health. Moreover, bed management was associated with AMR, which can serve as a guide for best practices to be adopted to avoid the occurrence of resistant bacteria in these animals.

Standing flank laparotomy for colic: 37 cases

BACKGROUND

Standing flank laparotomy can be an alternative to ventral midline laparotomy in horses with colic. Standing flank laparotomy avoids general anaesthesia, provides excellent access to some regions of the abdominopelvic cavity and costs less than ventral midline laparotomy.

OBJECTIVE

To report a series of cases of peritoneal and intestinal diseases other than SC diseases managed with standing flank laparotomy.

STUDY DESIGN

Retrospective case series.

METHODS

Records from equids with colic subjected to standing flank laparotomy at five hospitals (2003-2020) were reviewed. Descriptive data analysis was performed.

RESULTS

Thirty horses (sixteen survived to discharge), six ponies (four survived) and one donkey (euthanised) were subjected to standing flank laparotomy via the left flank (n = 31), right flank (n = 2) or both flanks (n = 4). The primary disease affected the peritoneum (0/5 survived), SI (5/9 survived) and caecum and/or LC (15/23 survived). Enterotomy was performed in four animals (all survived). Partial typhlectomy was performed in one horse (euthanised). Resection-anastomosis of the SI or LC was performed in three animals (one survived). Three animals had intraoperative complications that negatively affected the outcome: Two ponies had intolerance to abdominopelvic exploration; one mare had spontaneous exteriorisation of a long segment of the SI leading to a large tear in the mesentery. In seven cases, severe/extensive lesions found during standing flank laparotomy warranted immediate euthanasia. The survival rate was 54%. All owners were satisfied with the decision to perform standing flank laparotomy.

MAIN LIMITATIONS

The retrospective design, lack of a control group, small number of cases and lack of standardised protocols between hospitals.

CONCLUSIONS

Although ventral midline laparotomy is the standard of care for horses with colic, standing flank laparotomy is a viable approach for some types of colic. Systemic administration of analgesics may not produce sufficient peritoneal analgesia, which can lead to intolerance to abdominopelvic exploration during standing flank laparotomy in horses with colic and may negatively affect the outcome.

[Surgery site healing disorder following laparotomy in cattle: a retrospective study]

OBJECTIVES

Wound healing processes in consequence to bovine abdominal surgery performed from 2007 to 2016 at the University of Veterinary Medicine in Vienna were retrospectively assessed. The aim of this study was to evaluate the occurrence of wound healing complications following abdominal surgery in cattle during this 10-year-period as well as to identify possible risk factors such as elevated temperatures.

MATERIAL AND METHODS

Surgical procedures finding inclusion comprised ileus, left and right abomasal displacement, caecal dilation or displacement (right flank laparotomies), foreign body syndrome (left flank laparotomy), and umbilical surgery. Additionally, weather data during the study period were collected in order to investigate the possible association between ambient temperatures and wound healing disorders.

RESULTS

During this period 1365 abdominal surgical procedures were performed. The majority (68.6 %) of the cattle were Simmental cows, followed by 19.6 % Holstein Friesians. Female animals were overrepresented (73.0 %), and 24.0 % of the patients were calves. In 156 cases (11.7 %), a postoperative wound healing disorder (WHD) occurred. The majority of the laparotomies were performed from the right side; of these 21.4 % were left abomasal displacements and 21.7 % ileus surgeries. Left abomasal displacements (24.4 %) and surgery in the umbilical region (21.2 %) were associated with a higher occurrence of WHDs than other abdominal surgical procedures. Animals with right abomasal displacement developing WHDs were significantly younger than those without a WHD. A significant association between WHD frequency and higher temperatures could not be demonstrated. A total of 34.6 % WHD occurred during the summer months (June-September). However, the probability of developing WHDs increased significantly starting at an environmental temperature of 12.5 °C. Most WHD were observed in May (17.1 %) followed by July (15.6 %) and June (15.3 %).

CONCLUSION AND CLINICAL RELEVANCE

The occurrence of WHDs is influenced by numerous different factors such as age of the animal, disease, and type of the surgical procedure. The environmental temperature may increase the risk to develop a WHD but is only one parameter of a multifactorial process.

In vitro efficacy of a 0.2% polyhexamethylene biguanide-impregnated gauze dressing against pathogenic bacterial isolates found in horses

OBJECTIVE

To determine the ability of 0.2% polyhexamethylene biguanide (PHMB)-impregnated gauze to inhibit the growth of bacteria isolated from equine infected sites.

STUDY DESIGN

In vitro study.

METHODS

Nine bacterial isolates were obtained from cultures submitted from equine patients presenting with penetrating injuries of the hoof (n = 4), septic osteitis (n = 1), synovial sepsis (n = 1), wounds (n = 2), and incisional infection following laparotomy (n = 1). Two standardized strains were also included. A standard inoculum of each isolate was placed on 12 Muller-Hinton agar plates. Squares (2.5 cm × 2.5 cm) of 0.2% PHMB-impregnated (n = 6) and nonimpregnated control gauze (n = 6) were placed on inoculated agar plates. Bacterial growth under each gauze square was assessed after a 24-h incubation period and areas of inhibition were measured to a standardized scale, using image-processing software. Mean ± SD growth inhibition (%) using 0.2% PHMB-impregnated gauze was compared to the nonimpregnated gauze for each isolate using Student's t test (p < .05).

RESULTS

The 0.2% PMHB-impregnated gauze inhibited the growth of Staphylococcus spp. (n = 4) by 33%-83.1% and that of Escherichia coli spp. (n = 4) by 6.5%-37%. There was no inhibition of growth of Pseudomonas aeruginosa or either Enterococcus spp.

CONCLUSION

The 0.2% PHMB-impregnated dressing tested here inhibited the growth of staphylococcal and E. coli isolates, but the magnitude of inhibition varied between strains.

CLINICAL RELEVANCE

These results justify in vivo studies to evaluate the ability of the dressing to reduce the bacterial growth of common equine bacterial pathogens in clinical practice.

Incisional complications after skin closure with n-butyl cyanoacrylate or stainless-steel skin staples in horses undergoing colic surgery

OBJECTIVE

To compare the prevalence of incisional complications after skin closure with n-butyl cyanoacrylate (NBC) or stainless-steel skin staples (SS) after ventral midline celiotomy for colic surgery in the horse.

STUDY DESIGN

Retrospective study (2014-2018).

ANIMALS

Two hundred eighteen horses.

METHODS

Medical records of horses that underwent exploratory celiotomy for colic were included when the skin was closed with NBC or SS and the horse survived ≥15 days after surgery. Records and a follow-up questionnaire were used to determine in-hospital and posthospital discharge incisional complications. Associations between variables were assessed by using bivariable and multivariable analysis.

RESULTS

The cutaneous incision was closed with SS in 113 of 218 (51.8%) horses and with NBC in 105 of 218 (48.2%) horses. Follow-up information was available in 166 of 218 horses. Five horses with incisional complications prior to discharge but without follow-up were included in the overall analysis. Incisional complications were recorded in 17.5% (30/171) of horses, including 19.1% (17/89) of closures with SS and 15.9% (12/82) of closures with NBC (P = .54). Complications occurred before discharge in 14 of 218 (6.4%) horses and after discharge in 16 of 166 (9.6%) horses. Four horses with in-hospital incisional complications (surgical site infection) developed a second complication after discharge (hernia). Packed cell volume was a risk factor for in-hospital incisional complications (P = .04), and in-hospital incisional complications were associated with posthospital discharge incisional complications (P = .01).

CONCLUSION

Occurrence of incisional complications did not differ between NBC and SS.

CLINICAL SIGNIFICANCE

N-butyl cyanoacrylate is a suitable alternative to SS to close the cutaneous incision for ventral midline celiotomy for colic surgery in the horse.

Use of aminoglycoside antibiotics in equine clinical practice; a questionnaire-based study of current use

Veterinary use of the aminoglycoside antibiotics is under increasing scrutiny. This questionnaire-based study aimed to document the use of aminoglycosides with a particular focus on gentamicin. An online questionnaire was delivered to generalist equine veterinary surgeons and specialists in internal medicine to determine the perceived importance, frequency of use and routes of administration of the aminoglycoside antibiotics. A series of hypothetical scenarios were also evaluated regarding gentamicin. Data were compared to evaluate the impact of the level of specialisation on prescribing practices for different antibiotics using Chi-squared and Fischer's exact tests. Data were analysed from 111 responses. Gentamicin was commonly used empirically without culture and susceptibility testing. Generalists were more likely to use gentamicin only after susceptibility testing than specialists in a variety of clinical presentations including respiratory diseases, septic peritonitis, acute febrile diarrhoea, cellulitis and contaminated limb wounds (p < 0.01). Intravenous administration of gentamicin was most common, although inhaled and regional administration of gentamicin and amikacin were also described. Amikacin was most commonly used by intra-articular administration. Gentamicin was more likely to be used in high-risk procedures or contaminated surgeries (86% and 74%, respectively) compared with clean surgery (32%; p < 0.0001). Gentamicin was often used perioperatively in horses undergoing exploratory celiotomy and more commonly used in horses undergoing an enterotomy (90%) than without and enterotomy (79%; p = 0.04). Most respondents (86%) used gentamicin at a dose of 6.6 mg/kg in adults, with few changing their dosing strategies based on the presence of sepsis, although higher doses were more reported in foals (7-15 mg/kg) irrespective of the presence of sepsis. Aminoglycosides are widely used in equine practice and use outside current EU marketing authorisations is common. Stewardship of the aminoglycoside antibiotics could be enhanced in both generalists and specialists through the more frequent use of susceptibility testing, regional administration and dose adjustment, especially in foals.

Evaluation of the risk of incisional infection in horses following application of protective dressings after exploratory celiotomy for treatment of colic

OBJECTIVE To assess incidence of incisional infection in horses following management with 1 of 3 protective dressings after exploratory celiotomy for treatment of acute signs of abdominal pain (ie, colic) and determine the risk of complications associated with each wound management approach. DESIGN Prospective, randomized, controlled study. ANIMALS 85 horses. PROCEDURES Horses were assigned to 3 groups. After standardized abdominal closure, a sterile cotton towel (group 1) or polyhexamethylene biguanide-impregnated dressing (group 2) was secured over the incision site with 4 or 5 cruciate sutures of nonabsorbable monofilament, or sterile gauze was placed over the site and secured with an iodine-impregnated adhesive drape (group 3). Demographic and clinicopathologic data, intraoperative and postoperative variables, and development of complications were recorded and compared among groups by statistical methods. Follow-up information was collected 30 and 90 days after surgery. Incidence and odds of incisional complications were calculated. RESULTS 75 horses completed the study. Group 3 typically had dressing displacement necessitating removal during anesthetic recovery; dressings were in place for a mean of 44 and 31 hours for groups 1 and 2, respectively. Purulent or persistent serosanguinous incisional discharge (ie, infection) was detected in 11 of 75 (15%) horses (2/24, 0/26, and 9/25 from groups 1, 2, and 3, respectively). Odds of incisional complications were significantly greater for group 3 than for groups 1 or 2. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that risk of infection after celiotomy for treatment of colic is lower for incisions covered with sterile towels or polyhexamethylene biguanide-impregnated dressings secured with sutures than for incisions covered with gauze secured with iodine-impregnated adhesive drapes.

Bacterial translocation in horses with colic and the potential association with surgical site infection: a pilot study

BACKGROUND

Surgical site infection (SSI) is a leading cause of morbidity in horses undergoing emergency exploratory laparotomy for the treatment of acute colic. The exact mechanism by which SSI develops in these cases is unclear. This prospective observational study investigated whether bacterial translocation occurs in horses with acute colic and if there is an association between bacterial translocation and development of SSI.

METHODS

Peripheral venous blood (PVB) and peritoneal fluid (PF) samples were collected on admission and PF samples were collected at the end of surgery from horses presenting for investigation of acute colic. Any discharge from the laparotomy incision in horses that developed SSI was also collected. All samples were submitted for bacterial culture.

RESULTS

In total, 7.7 per cent of PVB samples (3/39), 11.8 per cent (4/34) of admission PF samples and 8.7 per cent (2/23) of the PF samples at surgery were culture positive. The prevalence of SSI was 10.2 per cent. No association was identified between a positive PVB or PF culture and development of a SSI or survival to hospital discharge.

CONCLUSION

Bacterial translocation can occur in some horses with acute colic. However, we were unable to identify any association between bacterial translocation and the development of SSIs following emergency exploratory laparotomy.

Incisional infections associated with ventral midline celiotomy in horses

OBJECTIVE

To review the veterinary literature regarding healing and complications associated with equine celiotomy including anatomy and physiology, risk factors for incisional infection and hernia, and treatment.

ETIOLOGY

Celiotomy is the most common approach to treat horses with surgical colic. Incision through the linea alba provides exposure to most of the abdomen for exploration, exteriorization, and correction of surgical lesions. Incisional apposition relies on suture strength during anesthetic recovery and for the first 30 days postoperatively. Factors associated with the patient, surgical lesion and procedures, anesthesia, and recovery put the horse at risk for surgical site infection. Infection is the most important risk factor for incisional hernia formation.

DIAGNOSIS

A presumptive diagnosis of surgical site infection is made based on the presence of fever and incisional swelling, pain, and discharge. Ultrasonography can be used to identify areas of fluid accumulation prior to the appearance of incisional drainage. Definitive diagnosis is based on positive bacteriologic culture of the incisional discharge. Incisional hernia is diagnosed by palpation of the incision, usually 30-60 days after surgery. Ultrasound of the incision may aide in early diagnosis of incisional hernia if gaps along the incision in the linea alba are apparent.

THERAPY

No objective data exist to assess the efficacy of specific therapies for surgical site infections following celiotomy. Principles of treatment include the establishment of drainage, bandaging, antimicrobial therapy based on culture and sensitivity, and extended rest in an attempt to avoid incisional hernia or dehiscence. Treatment for incisional hernia includes prolonged circumferential bandaging, open or minimally invasive hernia repair, or no treatment.

PROGNOSIS

Incisional complications are associated with prolonged convalescence and diminished prognosis for return to athleticism. Limiting risk factors for surgical site infections, prompt treatment, and incisional support may optimize celiotomy healing and timely return to function. Horses compete in many disciplines with incisional hernias.

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.

Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization

Background

Antimicrobial treatment protocols for foals with sepsis that do not improve clinically often are adjusted based on bacteriological and antimicrobial susceptibility testing results from samples collected at hospital admission.

Objectives

To evaluate whether hospitalization for ≥48 hours affects bacteriological and antimicrobial susceptibility testing results.

Animals

Two‐hundred sixty‐seven foals <30 days of age admitted to a neonatal intensive care unit and diagnosed with sepsis.

Methods

Medical records were reviewed retrospectively to identify foals with sepsis and positive bacteriological cultures. Results from samples collected at hospital admission were compared to those collected ≥48 hours after admission. Logistic regression for clustered data and exact logistic regression were used for statistical analysis.

Results

Three‐hundred fifty‐three unique bacterial isolates were obtained from 231 foals at hospital admission and 92 unique bacterial isolates were obtained from 57 foals after ≥48 hours of hospitalization. Relative isolation frequency after ≥48 hours of hospitalization increased for Acinetobacter spp., 0.6% versus 3.3% (odds ratio [OR], 7.63; 95% confidence interval [CI], 1.28‐45.45); Enterococcus spp., 4.8% versus 19.6% (OR, 5.37; 95% CI, 2.64‐10.90); Klebsiella spp., 5.1% versus 10.9% (OR, 2.27; 95% CI, 1.05‐4.89); Pseudomonas spp., 3.0% versus 7.6% (OR, 3.49; 95% CI, 3.49‐240.50); and Serratia spp., 3.0% versus 5.4% (OR, 20.23; 95% CI, 2.20‐186.14). Bacteria isolated after ≥48 hours of hospitalization were less susceptible to all tested antimicrobial drugs, except for imipenem.

Conclusions and Clinical Importance

Decreased antimicrobial susceptibility of bacteria isolated after ≥48 hours of hospitalization provides a rationale for repeated bacteriological culture and susceptibility testing in hospitalized foals with sepsis.

Retrospective Identification of Bacterial Isolates From Emergency Laparotomy Surgical Site Infections in Horses

Surgical site infection (SSI) with multiresistant bacteria is an important cause of postoperative morbidity after laparotomy in horses. The objective of this study was to identify bacteria isolates and their antibiotic resistance patterns associated with the development of wound infection in horses after laparotomy. This is a retrospective case series. Medical records of horses that underwent ventral midline exploratory laparotomy in a four-year period at one equine hospital were reviewed. Results of microbiologic culture and susceptibility testing are described. The study group consisted of 183 (100%) horses that recovered from anesthesia after laparotomy. The prevalence of infection was 19% (24/124) after first surgery and 83% (19/23) after relaparotomy. The most common microbial isolates were bacteria of the family Enterobacteriaceae followed by Staphylococcus ssp., Enterococcus ssp., Streptococcus ssp., and Bacteroides ssp. Bacteria from the family Enterobacteriaceae showed the lowest resistance to amphenicols, cephalosporins, and quinolones groups of antibiotics. Coagulase-positive Staphylococci were sensitive to amphenicols and only 33% were resistant to trimethoprim/sulfamethoxazole. The most commonly used perioperative and postoperative antibiotics were gentamicin and amoxicillin. Limitations include poor control over exposure factors, covariates, and potential confounders during the surgery, recovery time, or period of hospitalization; relying on others for accurate outcome assessment and recordkeeping; lack of follow-up information once animals were discharged from the hospital. Despite 5 days of antibiotic prophylaxis, the rate of incisional infection is still high. The most common isolates from SSI belong to the family Enterobacteriaceae and the genus Staphylococcus, which showed high resistance to the antibiotics used before the gastrointestinal surgery.

Correlation Between Peritonitis and Incisional Infections in Horses

Surgical site infection of abdominal incisions is an important complication after laparotomy with increased risk of incisional hernia formation in horses. This study aims to evaluate the healing process of abdominal incisions and correlate peritonitis with the occurrence of surgical site infection and incisional hernias. Nine horses underwent standardized laparotomy, intestinal exploration, and induced septic peritonitis. Standardized relaparotomy was performed two (n = 3), four (n = 3), and six (n = 3) months later to evaluate the abdominal cavity for adhesions and to collect the sutured ventral abdominal wall to evaluate and prepare it for histopathological and tensile strength study. All horses presented with endotoxemia, controllable peritonitis, heat and touch-sensitive ventral abdominal edema and surgical wound infection with presence of purulent discharge. Adhesion of the cecum or colon to the internal portion of the surgical wound was observed. Healing of the infected surgical wounds occurred by second intention and a space between the rectus abdominis muscles developed because of the presence of a scar, which was related to incisional hernia. In the histopathological evaluation, the collagen content increased, and the inflammation decreased over time. The tensile strength increased over time and was highest after 6 months. After the second surgical intervention, there was no infection of the surgical wound in any of the animals and healing by first intention occurred. Surgical site infection may be a symptom of peritonitis in horses recovering from abdominal surgery. Infected surgical wounds heal by second intention, which favors the spacing of rectus abdominis muscle and the formation of incisional hernia.

Antimicrobial dosing for common equine drugs: a content review and practical advice for veterinarians in Australia

BACKGROUND

Appropriate dosing with antimicrobial agents is critical for effective treatment and to prevent the development of antimicrobial resistance.

METHODS

A review was undertaken of equine journal articles (Equine Veterinary Journal, Equine Veterinary Education, Australian Veterinary Journal, Australian Equine Veterinarian, Journal of Veterinary Internal Medicine and Journal of Equine Veterinary Science) between January 2015 and August 2018. Those with dosing regimens for procaine penicillin G, gentamicin or trimethoprim-sulfonamide in adult horses were examined and evaluated. Pharmacokinetics and -dynamics of these drugs were also reviewed.

RESULTS & CONCLUSION

The most frequently reported doses for penicillin, gentamicin and trimethoprim-sulfonamide were 20-25,000 IU/kg, 6.6 mg/kg and 30 mg/kg, respectively. Veterinarians treating equine patients in Australia should be aware of the current recommended doses and inter-dosing intervals to ensure efficacy in therapy and to preserve the usefulness of these antimicrobials for the future.

Comparison of incisional complications between skin closures using a simple continuous or intradermal pattern: a pilot study in horses undergoing ventral median celiotomy

Background

Development of incisional complications following ventral median celiotomy might depend on suture pattern for skin closure.

Methods

In this prospective study, 21 healthy male horses underwent celiotomy. Skin closure was either performed via a continuous percutaneous pattern (CO group; 5 warmbloods/5 ponies) or an intradermal pattern (ID group; 5 warmbloods/6 ponies). Follow-up examination of the incisional site included daily monitoring for edema, dehiscence, and drainage. Transcutaneous ultrasound was performed at Days 3, 6, and 10 as well as on Week 8 and 12 to evaluate size of edema and presence or absence of sinus formation, and hernia formation. Prevalence of incisional infection on base of positive microbiological analysis at any time up to Day 10 was evaluated and compared between ID and CO group. Furthermore, edema size was analysed by a linear mixed-effect model for group and time dependency.

Results

Observed incisional complications included edema (9/10 in CO, 10/11 in ID), suture sinus formation (2/10 in CO, 1/11 in ID), surgical site infection (2/10 in CO, 0/11 in ID), and incisional hernia (1/10 in CO, 0/11 in ID). The overall prevalence of incisional infection was 9.5% without significant differences between both groups (20% in CO, 0% in ID; p = 0.214). Edema size was not dependent on time or group (p = 0.545 and p = 0.627, respectively).

Discussion

CO and ID suture pattern are appropriate for skin closure following ventral median celiotomy in horses. None of the animals in the continuous ID group developed surgical site infections, even without the use of antibiotics.

Antimicrobial resistance in horses

Cajsa Isgren and colleagues from the University of Liverpool discuss issues around the problem of antimicrobial resistance in bacteria associated with horses and introduce a new surveillance initiative.

Sequential bacterial sampling of the midline incision in horses undergoing exploratory laparotomy

BACKGROUND

There is limited information about bacterial isolates that are present on the equine midline incision during and following exploratory laparotomy.

OBJECTIVES

To investigate the bacterial species cultured from the ventral midline pre-, intra- and post- laparotomy, whether particular bacterial isolates are associated with the development of surgical site infections (SSIs) and to report the antimicrobial resistance phenotypes of these isolates.

STUDY DESIGN

Prospective cohort study.

METHODS

The ventral midline of 31 horses undergoing exploratory laparotomy was sampled for bacterial culture at set time-points pre, intra and post-operatively. Inclusion criteria were that horses must have undergone exploratory laparotomy within 90 min of the initial colic examination upon hospital admission and must not have been placed in a stable prior to surgery. SSI was defined as any purulent or serous discharge from the laparotomy incision of >24 h duration.

RESULTS

Seven horses (22.6%) developed a SSI. None of the variables tested were associated with the altered risk of SSI. The prevalence of a positive bacterial culture from the incision increased progressively over time and a variety of bacteria were isolated. A positive intra-operative culture was not a predictor of SSI; and when a SSI did occur, it was due to a different bacterial isolate. MRSA and ESBL-producers were identified in the post-operative period in one and four different horses respectively, but none of these developed a SSI.

MAIN LIMITATIONS

Sampling was limited to hospitalisation and no culture results were available for horses developing SSI following hospital discharge.

CONCLUSIONS

A variety of bacterial species may be isolated from equine laparotomy incisions peri-operatively without development of SSI. SSI does not appear to be solely related to bacterial contamination of the incision peri-operatively and other mechanisms such as bacteraemia merit further investigation.

Season of the year influences infection rates following total hip arthroplasty

AIM

To research the influence of season of the year on periprosthetic joint infections.

METHODS

We conducted a retrospective review of the entire Medicare files from 2005 to 2014. Seasons were classified as spring, summer, fall or winter. Regional variations were accounted for by dividing patients into four geographic regions as per the United States Census Bureau (Northeast, Midwest, West and South). Acute postoperative infection and deep periprosthetic infections within 90 d after surgery were tracked.

RESULTS

In all regions, winter had the highest incidence of periprosthetic infections (mean 0.98%, SD 0.1%) and was significantly higher than other seasons in the Midwest, South and West (P < 0.05 for all) but not the Northeast (P = 0.358). Acute postoperative infection rates were more frequent in the summer and were significantly affected by season of the year in the West.

CONCLUSION

Season of the year is a risk factor for periprosthetic joint infection following total hip arthroplasty (THA). Understanding the influence of season on outcomes following THA is essential when risk-stratifying patients to optimize outcomes and reduce episode of care costs.

Antimicrobial Resistance-Transducing Bacteriophages Isolated from Surfaces of Equine Surgery Clinics - A Pilot Study

In the past, the horizontal transfer of antimicrobial resistance genes was mainly associated with conjugative plasmids or transposons, whereas transduction by bacteriophages was thought to be a rare event. In order to analyze the likelihood of transduction of antimicrobial resistance in the field of clinical veterinary medicine, we isolated phages from Escherichia coli from a surgery suite of an equine clinic. In a pilot study, the surgery suite of a horse clinic was sampled directly after surgery and subsequently sampled after cleaning and disinfection following a sampling plan based on hygiene, surgery, and anesthesia. In total, 31 surface sampling sites were defined and sampled. At 24 of these 31 surface sampling sites, coliphages were isolated. At 12 sites, coliphages were found after cleaning and disinfection. Randomly selected phages were tested for their ability of antimicrobial resistance transduction. Ten of 31 phages were detected to transfer antimicrobial resistance. These phages most often transduced resistance to streptomycin, encoded by the addA1 gene (n = 9), followed by resistance to chloramphenicol by cmlA (n = 3) and ampicillin (n = 1). This is, to the best of our knowledge, the first report on antimicrobial resistance-transferring bacteriophages that have been isolated at equine veterinary clinics.

Are horse age and incision length associated with surgical site infection following equine colic surgery?

It is our clinical impression that age and incision length are more strongly associated with surgical site infection (SSI) following colic surgery than skin closure or wound protection method. Therefore, the objective of this observational clinical cohort study was to identify the risks for SSI in horses undergoing colic surgery. Data collection included pre-, intra-, and postoperative variables. Variables with P < 0.2 following univariable analysis were used in a logistic regression multivariable model. Variables with P <0.05 were included in the final model. Odds ratios (OR; 95% confidence intervals, 95% CI) were determined. The area under the curve (AUC) for the receiver-operator characteristic was calculated. The final multivariable model included breed (P = 0.008), incision length (P = 0.004), surgical procedure classification (P <0.001), and postoperative (PO) colic (P = 0.037; overall model P <0.001, and AUC was 0.81 [excellent discrimination between SSI vs. no SSI]). Warmbloods (OR 12.0; 95% CI 2.7-74.8), American breeds (OR 6.4; 95% CI 1.2-43.0), and Thoroughbreds (4.5; 95% CI 1.1-25.5) more commonly had SSI than other breeds (ponies/miniature horses, Draft breeds, Standardbreds, Arabians, and Crossbreeds [referent]). A higher SSI rate was associated with incision lengths >27 cm (3.7; 95% CI 1.5-9.9), heavily contaminated procedures (12.0; 95% CI 3.3-49.9), and horses with PO colic (2.7; 95% CI 1.1-6.8). SSI appeared to be more common after heavily contaminated procedures and in horses with PO colic, which probably resulted in more incisional contamination and trauma. Some breeds appeared to have higher odds of SSI. Age was not associated with SSI. The risk of developing SSI was higher for horses with an incision >27 cm; therefore, surgeons are encouraged to use the minimum incision length required to accomplish the necessary abdominal exploration and bowel manipulation in the safest manner possible.