L. C. Sanchez

Effect of systemic lidocaine on visceral and somatic nociception in conscious horses.

REASONS FOR PERFORMING STUDY Commonly used analgesics (nonsteroidal anti-inflammatory agents, opioids and alpha2-agonists) have unwanted side effects. An effective alternative with minimal adverse effects would benefit clinical equine pain management. OBJECTIVES To compare the effect of lidocaine or saline on duodenal and rectal distension threshold pressure and somatic thermal threshold in conscious mature horses. HYPOTHESIS Systemically administered lidocaine would increase somatic and visceral nociceptive thresholds. METHODS Lidocaine (2 mg/kg bwt bolus followed by 50 microg/kg bwt/min for 2 h) or saline was administered to 6 horses each carrying a permanently implanted gastric cannula, in a randomised, blinded cross-over design. Thermal threshold was measured using a probe containing a heater element placed over the withers which supplied heat until the horse responded. A barostatically controlled intraduodenal balloon was distended until a discomfort response was obtained. A rectal balloon was inflated until extruded or signs of discomfort noted. RESULTS Thermal threshold was increased significantly 30 and 90 mins after the start of lidocaine infusion. There was no change in duodenal distension pressure and a small but clinically insignificant change in colorectal distension pressure in the lidocaine group. CONCLUSIONS At the dose used, systemically administered lidocaine produced thermal antinociception but minimal changes in visceral nociception. POTENTIAL RELEVANCE At these doses, lidocaine may play a role in somatic analgesia in horses.

Infectious agents detected in the feces of diarrheic foals: a retrospective study of 233 cases (2003-2008).

Background: Diarrhea is common in foals but there are no studies investigating the relative prevalence of common infectious agents in a population of hospitalized diarrheic foals. Objectives: To determine the frequency of detection of infectious agents in a population of hospitalized foals with diarrhea and to determine if detection of specific pathogens is associated with age, outcome, or clinicopathologic data. Animals: Two hundred and thirty‐three foals ≤ 10 months of age with diarrhea examined at a referral institution. Methods: Retrospective case series. Each foal was examined for Salmonella spp., viruses, Clostridium difficile toxins, Clostridium perfringens culture, C. perfringens enterotoxin, Cryptosporidium spp., and metazoan parasites in feces collected at admission or at the onset of diarrhea. Results: At least 1 infectious agent was detected in 122 foals (55%). Rotavirus was most frequently detected (20%) followed by C. perfringens (18%), Salmonella spp. (12%), and C. difficile (5%). Foals < 1 month of age were significantly more likely to be positive for C. perfringens (odds ratio [OR] = 15, 95% confidence interval [CI] = 3.5–66) or to have negative fecal diagnostic results (OR = 3.0, 95% CI = 1.7–5.2) than older foals. Foals > 1 month of age were significantly more likely to have Salmonella spp. (OR = 2.6, 95% CI = 1.2–6.0), rotavirus (OR = 13.3, 95% CI = 5.3–33), and parasites (OR = 23, 95% CI = 3.1–185) detected compared with younger foals. Overall 191 of the 223 foals (87%) survived. The type of infectious agent identified in the feces or bacteremia was not significantly associated with survival. Conclusions and Clinical Importance: In the population studied, foals with diarrhea had a good prognosis regardless of which infectious agent was identified in the feces.

Treatment efficacy of trimethoprim sulfamethoxazole, pentoxifylline and altrenogest in experimentally induced equine placentitis

The objective was to determine if long-term treatment with trimethoprim sulfamethoxazole (antimicrobial), pentoxifylline (anti-inflammatory/anti-cytokine) and altrenogest (synthetic progestin), would improve pregnancy outcome in mares with experimentally induced placentitis. Seventeen normal, pregnant pony mares were enrolled in the study at 280-295 d of pregnancy. Placentitis was induced in all mares by intra-cervical inoculation of Streptococcus equi subsp. zooepidemicus (10(7) CFU). Five mares served as infected, untreated control animals (Group UNTREAT). Twelve mares (Group TREAT) were infected and given trimethoprim sulfamethoxazole (30 mg/kg, PO, q 12h), pentoxifylline (8.5 mg/kg, PO, q 12h) and altrenogest (0.088 mg/kg, PO, q 24h) from the onset of clinical signs to delivery of a live foal or abortion. Blood samples were cultured from all foals at delivery and fetal stomach and thoracic contents were obtained for culture from dead fetuses. More mares in Group TREAT delivered viable foals (10/12; 83%; P < 0.05) than mares in Group UNTREAT (0/5; 0%). Ten of 12 foals (83%) in Group TREAT had negative blood cultures at birth. All foals in Group UNTREAT (5/5; 100%) had positive cultures from one or more samples (blood, stomach contents, and thoracic fluid). Bacteria were recovered from uterine culture samples in both groups. Streptococcus equi subsp. zooepidemicus was the predominant organism recovered from fetal/foal or mare culture samples. The authors inferred that administration of trimethoprim sulfamethoxazole, pentoxifylline and altrenogest may improve the viability of foals from mares with experimentally induced placentitis.

Effect of paddock vs. stall housing on 24 hour gastric pH within the proximal and ventral equine stomach

REASONS FOR PERFORMING STUDY Stall housing has been suggested as a risk factor for ulcer development in the equine stomach; however, the exact pathogenesis for this has not been established. OBJECTIVES To investigate the effect of 3 environmental situations (grass paddock, stall alone or stall with adjacent companion) on pH in the proximal and the ventral stomach. METHODS Six horses with permanently implanted gastric cannulae were used in a randomised, cross-over, block design. Each horse rotated through each of three 24 h environmental situations. Horses remained on their normal diet (grass hay ad libitum and grain b.i.d.) throughout the study. Intragastric pH was measured continuously for 72 h just inside the lower oesophageal sphincter (proximal stomach) and via a pH probe in the gastric cannula (ventral stomach). RESULTS Neither proximal nor ventral 24 h gastric pH changed significantly between the 3 environmental situations. Mean hourly proximal gastric pH decreased significantly in the interval from 01.00-09.00 h compared to the interval from 13.00-20.00 h, regardless of environmental situation. Median hourly proximal pH only differed in the interval from 06.00-07.00 h compared to the interval 14.00-19.00 h. Neither mean nor median hourly ventral gastric pH varied significantly with the time of day. CONCLUSIONS The change in housing status used in the current study did not affect acid exposure within either region of the equine stomach. The pH in the ventral stomach was uniformly stable throughout the study, while the proximal pH demonstrated a 24 h circadian pattern.

Pain control in horses: What do we really know?

Currently, approaches to pain control in horses are a mixture of art and science. Recognition of overt pain behaviours, such as rolling, kicking at the abdomen, flank watching, lameness or blepharospasm, may be obvious; subtle signs of pain can include changes in facial expression or head position, location in the stall and response to palpation or human interaction. Nonsteroidal anti-inflammatory drugs (i.e. phenylbutazone, flunixin meglumine and firocoxib), opioids (i.e. butorphanol, morphine and buprenorphine) and α2 -adrenergic agonists (i.e. xylazine, detomidine, romifidine and medetomidine) are the most commonly used therapeutic options. Multimodal therapy using constant-rate infusions of lidocaine, ketamine and/or butorphanol has gained popularity for severe pain in hospitalised cases. Drugs targeting neuropathic pain, such as gabapentin, are increasingly used for conditions such as laminitis. Optimal strategies for management of pain are based upon severity and chronicity, including special considerations for use of intra-articular or epidural delivery and therapy in foals. Strategies that aim to mitigate adverse effects associated with use of various analgesic agents are briefly discussed.

Effect of a feed/fast protocol on pH in the proximal equine stomach.

REASONS FOR PERFORMING STUDY Risk factors for the development of gastric squamous ulcers include various management procedures, such as intermittent feed deprivation that can occur during weight management regimens or stall and dry lot confinement. OBJECTIVES To investigate the effect of intermittent feed deprivation relative to continuous feed intake on proximal intragastric pH, specifically in the region of the squamous mucosa of the lesser curvature. METHODS In 6 horses, pH electrodes were placed just inside of the oesophageal sphincter in the stomach for each of two 72 h protocols (A and B) in a randomised, cross-over design. Protocol A consisted of 12 h fed, 12 h fasted, 24 h fed and 24 h fasted, in sequence. Protocol B consisted of 72 h fed. During the fed periods of each protocol, horses had ad libitum access to coastal Bermuda hay and were fed sweet feed (1 kg, b.i.d.). Horses had ad libitum access to water at all times. RESULTS Proximal intragastric pH was significantly lower during protocol A, than during protocol B. However, hourly mean pH was significantly different only during the day and evening hours between protocols. During protocol B, mean proximal pH decreased significantly from 03.00 to 09.00 compared to 19.00 to 23.00 h. A moderate positive correlation of hay intake vs. proximal gastric pH could be established. CONCLUSIONS Intermittent feed deprivation decreased proximal gastric pH in horses relative to those horses for which feed was not restricted. However, the effect was only significant when fasting occurred during the day and evening hours, as a nocturnal decrease in pH occurred simultaneously in the fed horses. POTENTIAL RELEVANCE Episodes of daytime feed deprivation should be avoided if possible, as proximal gastric acid exposure rapidly increases during such events.

Re-evaluation of the sepsis score in equine neonates

REASONS FOR PERFORMING STUDY The modified sepsis scoring system provides a method to identify sepsis in foals early in the disease process, but inconsistent results have been obtained from its clinical application in previous studies. OBJECTIVES To evaluate the sensitivity and specificity of the modified sepsis score in a larger population of foals. A secondary objective was to identify factors associated with sepsis. STUDY DESIGN Retrospective cohort study. METHODS Records were retrospectively analysed for neonatal admissions to the University of Florida Large Animal Hospital from 1982 to 2008. Backwards stepwise multivariable logistic regression was used to evaluate objective clinical factors associated with sepsis. Receiver operating chararacteristic ROC curve analysis was performed on the modified sepsis score and used to determine an optimal cut point. RESULTS A total of 1065 foals were included in the study. The modified sepsis score had a sensitivity of 56.4% and specificity of 73.4% for the originally suggested cut point (>11). Receiver operating chararacteristic analysis revealed an optimal cut point of >7 (sensitivity 84.4%, specificity 41.8%). The modified sepsis score performed better than the generated regression model which included age, creatinine, lymphocytes, potassium and IgG>8 g/l (P = 0.026). Diagnostic performance of the modified sepsis score did not change significantly over time. CONCLUSIONS Sensitivity and specificity of the modified sepsis score were not as high as previously documented, but the score still outperformed a regression model derived from objective clinical data. The Summary is available in Chinese - see Supporting information.

Colorectal distention in the horse: visceral sensitivity, rectal compliance and effect of i.v. xylazine or intrarectal lidocaine

REASONS FOR PERFORMING STUDY Most current models of visceral sensitivity testing in the horse have required visceral cannulation. Colorectal distention (CRD) is a widely used, noninvasive method for testing in other species and could be adapted for use in horses. OBJECTIVES To develop a protocol of controlled CRD in the conscious horse and to evaluate the effect of i.v. xylazine or intrarectal lidocaine on CRD threshold and rectal compliance. METHODS Eight horses were used for baseline studies (3 trials each) and 6 horses to evaluate treatments (4 trials, 2 per treatment). A 45 cm diameter polyvinyl balloon attached to plastic tubing was used for rectal distention following a stepwise barostat-controlled inflation pattern. RESULTS The procedure was well tolerated by all horses. Mean baseline threshold pressure was 14.17 mmHg. Xylazine i.v. resulted in significantly (P < 0.05) higher mean threshold pressures compared to baseline or rectal lidocaine. Rectal compliance increased following lidocaine treatment relative to baseline or xylazine. CONCLUSIONS CRD offers a noninvasive method for visceral sensitivity testing in the horse. Xylazine raises CRD threshold, while lidocaine increases rectal compliance. POTENTIAL RELEVANCE The increased rectal compliance following intrarectal lidocaine administration may explain the benefit of its use to facilitate rectal examination.

Retrospective Comparison of Caffeine and Doxapram for the Treatment of Hypercapnia in Foals with Hypoxic‐Ischemic Encephalopathy

BACKGROUND Despite a lack of data regarding their efficacy, both caffeine and doxapram have been recommended for treatment of hypercapnia in equine neonates with central nervous system damage. HYPOTHESIS Caffeine and doxapram alleviate hypercapnia in foals with hypoxic-ischemic encephalopathy. ANIMALS Sixteen foals treated with either caffeine (n = 8) or doxapram (n = 8). METHODS Information on age, body temperature, heart rate, respiratory rate, arterial blood gas parameters, duration of therapy, and outcome was abstracted from each medical record. RESULTS Therapy with doxapram resulted in a significant decrease in partial pressure of carbon dioxide (PaCO2 [P= .004]), bicarbonate concentration (P= .002), and base excess (P= .005) compared with baseline values but failed to correct acidemia. In contrast, administration of caffeine did not result in significant changes from baseline values. The percentage decrease in PaCO2 and bicarbonate concentration was significantly greater in foals treated with doxapram than in foals treated with caffeine (P= .004). The proportions of foals that achieved the targeted PaCO2 (< or = 50 mmHg) were significantly higher in foals treated with doxapram than in foals treated with caffeine (P= .029). The proportion of survivors in the 2 treatment groups was not significantly different. CONCLUSIONS AND CLINICAL IMPORTANCE Doxapram is more effective than caffeine for rapid correction of hypercapnia in foals with hypoxic-ischemic encephalopathy.

Disposition of desfuroylceftiofur acetamide in serum, placental tissue, fetal fluids, and fetal tissues after administration of ceftiofur crystalline free acid (CCFA) to pony mares with placentitis

The objective of this study was to determine the pharmacokinetics of CCFA in mares with placentitis and evaluate the disposition of the drug in fetal fluids, fetal membranes, colostrum, and serum of foals. A secondary objective was to obtain pilot data regarding the efficacy of CCFA for improving foal survival in mares with placentitis. Twelve pregnant pony mares were enrolled in the study, inoculated with Streptococcus zooepidemicus, intracervically and assigned to one of three groups: CEFT (n = 3; administered CCFA only; 6.6 mg/kg, i.m., q96h); COMBO (n = 6; administered combination therapy of CCFA, altrenogest, and pentoxifylline); UNTREAT (n = 3, no treatment). Treatment was initiated at the onset of clinical signs. Concentrations of desfuroylceftiofur acetamide (DCA), the acetamide derivative of ceftiofur and desfuroylceftiofur metabolites, were measured using high-performance liquid chromatography. Maximum and minimum serum concentrations of DCA at steady state in treated mares were 2.40±0.40 μg/mL and 1.06±0.29 μg/mL, respectively. Concentration of DCA in colostrum was 1.51±0.60 μg/mL. DCA concentrations in placenta and fetal tissues were very low (median = 0.03 μg/mL) and below the minimum inhibitory concentration of relevant pathogens. DCA was not detected in amniotic fluid or foal serum. Treatment did not appear to improve foal survival (CEFT: 0/3; COMBO: 2/6; UNTREAT: 2/3). Bacteria were recovered from the uterus of most mares postpartum and from blood cultures of most foals regardless of treatment.