Investigation of glucagon-like peptide-1 response to six oral carbohydrates in ponies

Glucagon-like peptide-1 (GLP-1), the principal incretin in horses, may play a role in the pathophysiology of insulin dysregulation (ID). This study aimed to describe its concentration in response to three preserved forages and four dynamic tests for ID in ponies. Twelve adult ponies of mixed ID status were given a meal of hay, soaked hay or haylage, an in-feed oral glucose test (OGT), oral sugar test (OST), an oral test using a proprietary breakfast cereal (WEET) or a combined glucose-insulin tolerance test (CGIT) weekly in a randomised cross-over study. Glucose, insulin and GLP-1 concentrations were measured before and following each intervention. Ponies were designated ID or non-ID and insulin resistant (IR) or non-IR according to OGT and CGIT results, respectively. All interventions apart from the CGIT provoked a GLP-1 response within 30 min. The OGT and WEET interventions, (containing the greatest dose of non-structural carbohydrate, 1.06 and 1 g/kg BW, respectively), resulted in a greater area under the curve (AUC) for GLP-1 compared to all other interventions (P < 0.001). No difference in GLP-1 response was detected according to ID or IR status, despite there being strong positive correlations (rs [95 % CI]) between GLP-1 and insulin concentrations measured at individual time points (0.67 [0.62 - 0.71]; P < 0.001) and as AUC (0.66 [0.49-0.79], P < 0.001). These data do not support of the use of GLP-1 as an adjunctive diagnostic test for ID or IR, as defined by conventional intravenous or oral dynamic tests.

Comparison of one novel and four established diagnostic tests for insulin dysregulation in ponies

Several tests have been advocated for diagnosis of insulin dysregulation (ID). Tests using simple sugars may not reflect the response to naturally ingested carbohydrates. This study aimed to evaluate agreement between the oral glucose test (OGT), the oral sugar test (OST), a novel oral test using a proprietary cereal (WEET), the IV combined glucose-insulin tolerance test (CGIT) and fasted basal insulin (FI) for diagnosis of ID. Each of the five tests above was performed on a group of six normal and six insulin dysregulated mixed-breed ponies in a randomised crossover study. Area under the curve (AUC) and maximum concentration of insulin from OGT, OST and WEET showed strong to very strong bivariate correlations (r = 0.85-0.94, and r = 0.87-0.92, respectively; P ≤ 0.001) and were significantly different between tests (associated with dose of carbohydrate) and between CGIT-positive and -negative ponies. Dichotomous results showed substantial agreement between OST and both WEET (κ = 0.65; P = 0.02) and OGT (κ = 0.67; P = 0.01) and between CGIT and both OST (κ = 0.63; P = 0.03) and OGT (κ = 0.67; P = 0.01), and no agreement between FI, which had low sensitivity, and all other tests (κ = 0.15 - 0.31; P > 0. 05). Palatability of WEET was variable, resulting in one pony being excluded for analysis of WEET data. Further work on development of an oral test using a more palatable feedstuff and appropriate cut-offs or diagnostic thresholds for tests of ID is warranted.

Evaluation of pulse co-oximetry to determine haemoglobin saturation with oxygen and haemoglobin concentration in anaesthetized horses: a retrospective study

OBJECTIVE

This study compared the values of variables measured by pulse co-oximetry (Masimo Radical 7; Masimo Europe Limited, UK) with those measured by a co-oximeter-enabled blood gas analyser (Siemens Rapid-point 500; Siemens Healthcare Limited, UK) in anaesthetized horses.

STUDY DESIGN

Retrospective study.

ANIMALS

A total of 30 anaesthetized horses.

METHODS

In total, 47 heparinized arterial blood samples were collected for blood gas analysis to determine haemoglobin concentration (tHb, g L^-1) and percentage of haemoglobin saturation with oxygen (SaO₂). Arterial haemoglobin saturation with oxygen was determined noninvasively by pulse co-oximetry (Masimo SpO₂). Pulse co-oximetry also provided arterial haemoglobin concentration (SpHb) and arterial oxygen content (SpCaO₂). Arterial oxygen content was calculated (CaO₂) in 39 samples using SaO₂ and the value of Hüfner's constant used by Masimo Radical 7 (1.3 mL g^-1). Data were compared using Bland-Altman analysis, correlation tests, accuracy root mean square (ARMS) statistics and total allowable error, where available.

RESULTS

Low bias but wide limits of agreement (LoA) were found between Masimo SpO₂ and SaO₂ (bias = -1.4%, LoA = -4.0 to 1.3%), with an ARMS of 3%. Compared with tHb, SpHb showed low bias (6.2 g L^-1) but wide LoA (-39.6 to 52.6 g L^-1); its % bias (5.2%) was still within the 7% limits recommended by the Clinical Laboratory Improvement Amendments (CLIA) for humans. When comparing SpCaO₂ and CaO₂, the bias and LoA were -0.2 mL dL^-1 and -6.7 to 6.2 mL dL^-1, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Masimo SpO₂ was acceptable for current ARMS standards, and SpHb measurements also met CLIA limits. The wide LoA in this study, however, suggest that the Masimo Radical 7 cannot be recommended as a substitute for direct measurements. As blood gas machines, pulse oximeters and co-oximeters use algorithms based on human haemoglobin, no true gold standard exists for horses.

Anaesthesia with sevoflurane in pigeons: minimal anaesthetic concentration (MAC) determination and investigation of cardiorespiratory variables at 1 MAC

The objective of the study was to determine the minimal anaesthetic concentration (MAC) of sevoflurane (SEVO) in pigeons and investigate the effects of 1 MAC SEVO anaesthesia on cardiovascular and respiratory variables compared with the awake state. This is a prospective, experimental study. Animals were seven healthy adult pigeons. After acclimatisation to handling, heart rate (HR), heart rhythm, respiratory rate (fR), end-expired carbon dioxide tension (PE'CO2), inspired CO2 tension, indirect systolic arterial blood pressure (SAP) and cloacal temperature were measured to determine baseline, 'awake' values. Pigeons were then anaesthetised with SEVO and MAC was determined by the 'bracketing' method. The same variables were monitored during a 40 minute period at 1.0 MAC SEVO for each bird. Mean MAC was 3.0±0.6 per cent for SEVO. During maintenance of anaesthesia at 1.0 MAC, SAP decreased significantly (P<0.001) without any significant change in HR. Although PE'CO2 increased significantly (P=0.001) despite an increase in fR, awake PE'CO2 values were unexpectedly low. Sinus arrhythmias were detected in two birds under SEVO anaesthesia. The times to tracheal intubation and to recovery were 2.5±0.7 and 6.4±1.7 minutes, respectively. Recovery was rapid and uneventful in all birds. In conclusion, SEVO is suitable for anaesthesia in pigeons.

Assessment of body fat in the pony: part I. Relationships between the anatomical distribution of adipose tissue, body composition and body condition

REASONS FOR PERFORMING STUDY

Evaluation of equine body fat content is important for nutritional and clinical purposes. However, our understanding of total body fat and its regional distribution in the body is sparse. Currently, body fat evaluation relies on the subjective assessment of body condition score (BCS), which has never been validated against 'gold standard' chemical analysis or dissection measurements in ponies.

OBJECTIVES

To define the relationships between subjective (BCS), objective (morphometric) indices of body fat and 'gold standard' measurements of actual body composition.

HYPOTHESES

BCS and morphometry offer valid, noninvasive methods for determination of body fat in equids.

METHODS

Seven mature (mean ± s.e. 13 ± 3 years, 212 ± 14 kg, BCS 1.25-7/9), Welsh Mountain pony mares, destined for euthanasia (for nonresearch purposes), were used. For all ponies, body mass (BM), BCS and various morphometric measurements were recorded. Following euthanasia, all ponies were systematically dissected. Discrete white adipose tissue (WAT) depots were independently described. Gross, body chemical composition was determined by proximate analyses.

RESULTS

Total somatic soft tissues increased linearly (r(2) = 1.00), whereas body WAT content (1-26% live BM) increased exponentially (r(2) = 0.96), with BCS. WAT was equally distributed between internal and external sites in all animals irrespective of BCS. Nuchal fat was a poor predictor of total WAT (r(2) = 0.66). Periorbital WAT did not alter with BCS (r(2) = 0.01). Heart girth:withers height and ultrasonic retroperitoneal fat depth were closely associated with total, chemically-extracted lipid which comprised 1-29% live BM (r(2) = 0.91 and 0.88, respectively).

CONCLUSIONS AND POTENTIAL RELEVANCE

The exponential relationship between BCS and total body WAT/lipid suggests that BCS is unlikely to be a sensitive index of body fat for animals in moderate-obese states. Morphometric measurements (body girths and retroperitonel fat depth) may be useful to augment subjective BCS systems.

Effect of dietary restriction on body condition, composition and welfare of overweight and obese pony mares

REASONS FOR PERFORMING STUDY

Increased prevalence of obesity among UK horses and ponies demands evidence-based advice to promote weight loss.

HYPOTHESIS

Restriction of dry matter intake (DMI) to 1% of body mass (BM, 67% [corrected] of predicted maintenance digestible energy [DE] requirements) would promote weight loss without compromise to health.

METHODS

Five mature (mean ± s.e. 10 ± 2 years), overweight/obese pony mares (BM, 257 ± 20 kg: body condition score [BCS] 6.8/9 ± 0.5) were studied over 12 weeks. Animals were individually housed. Daily provision of a chaff-based, complete diet (measured DE, 8.5 MJ/kg DM) was restricted to 1% of actual BM as DMI daily. BCS, girth measurements and ultrasound-derived measures of subcutaneous fat depth overlying the gluteal region and 12th intercostal space (rib-eye) were recorded weekly. Body fat content was estimated at the beginning and end of the study by deuterium oxide dilution methods. Clinical biochemistry was monitored weekly. Behaviour was observed (24 h, 3/5 ponies) on 3 occasions.

RESULTS

BM decreased by 4.3 ± 1.1% during the first week and thereafter by 0.7 ± 0.1% of BM at end of Week 1 each week. BCS remained constant. Heart and belly girths, rump width and subcutaneous fat depth at rib-eye decreased significantly with time and BM. Fat comprised 45 ± 19% of BM loss. Fatter animals lost relatively more fat. With decreased feeding activity, time spent in 'play' and rest increased by 36 ± 11% and 438 ± 95%, respectively.

CONCLUSIONS

This plane of nutrition resulted in an overall rate of weight loss of 1% of outset BM weekly. BCS was not a useful index of early weight loss but heart and belly girths and subcutaneous rib-eye fat were identified as alternative markers.

POTENTIAL RELEVANCE

This study provides an evidence-base for the management of weight loss in obese animals, especially those for which exercise may be contra-indicated.

Post anaesthetic colic in horses: a preventable complication?

REASONS FOR PERFORMING STUDY

There is little information on the prevalence of, and risk factors associated with, post anaesthetic colic (PAC) in horses undergoing nonabdominal operations.

OBJECTIVES

To undertake the first prospective study of prevalence of PAC and identify risk factors in its development in nonabdominal procedures.

METHODS

A multicentre prospective case-control study was conducted, on every horse undergoing anaesthesia for a nonabdominal procedure between April 2004 and June 2005. Colic cases were defined as any horse with recognised signs of abdominal pain within 72 h of general anaesthesia that could not be attributed to any concurrent disease. Five control horses per case were selected randomly from the study population at all hospitals. Multivariable logistic regression analysis was used to examine the relationship between predictor variables and the risk of developing PAC.

RESULTS

The estimated mean prevalence of PAC in the study population was 5.2% (95% CI, 2.8, 8.0). However, the prevalence of colic varied between each centre. The most commonly diagnosed cause of colic was impaction. Multivariable analyses showed that the centre involved and the type of surgery performed were associated with an increased risk of PAC. Preoperative food deprivation and the use of opioid drugs were confounding factors.

CONCLUSIONS

Prevalence of PAC varied significantly between the 4 hospitals studied; there may be hospital-related covariates that account for this. The type of surgery performed influenced the risk of PAC.

POTENTIAL RELEVANCE

Identifying the risk factors for PAC is a prerequisite for its prevention. This study indicates horses at increased risk of PAC that might benefit from a more critical evaluation of post anaesthetic gastrointestinal function and/or the provision of preventative measures. Further investigation is required to explain the variation in prevalence of PAC between centres.

Does pethidine affect the cardiovascular and sedative effects of dexmedetomidine in dogs?

OBJECTIVES

To investigate pethidine's effects on sedation and cardiovascular variables in dogs premedicated with dexmedetomidine.

METHODS

Sixty American Society of Anesthesiologists (ASA) I dogs were presented for routine neutering. Heart rate was measured at admission. Dogs were randomly assigned to one of the five groups to decide premedication; group D5+P (dexmedetomidine 5 microg/kg plus pethidine 5 mg/kg), D10+P (dexmedetomidine 10 microg/kg plus pethidine 5 mg/kg) with three control groups, D5 (dexmedetomidine 5 microg/kg), D10 (dexmedetomidine 10 microg/kg) or P (pethidine 5 mg/kg). Heart rate was measured at 3, 5, 10 and 20 minutes after preanaesthetic medication. Simple descriptive scores for sedation were assigned after 20 minutes. Anaesthesia was induced using propofol and maintained using isoflurane in oxygen. Heart rate was recorded throughout anaesthesia.

RESULTS

Sedation scores after preanaesthetic medication were significantly higher (P<0.001) in groups D5+P and D10+P compared with the other three groups. D5+P and D10+P groups tended to have lower heart rates in dogs at all time points after premedication compared with groups containing only pethidine or dexmedetomidine at the relevant dose.

CLINICAL SIGNIFICANCE

Greater sedation is achieved using combinations of dexmedetomidine and pethidine compared with each drug alone. Pethidine does not attenuate the alpha-2 adrenergic-induced bradycardia.

Tracheal necrosis following tracheal intubation in a dog

Tracheal rupture and stenosis are well-reported problems in human beings and cats following endotracheal intubation. However, this problem has been rarely reported in dogs. This case report describes a case of tracheal necrosis 5 days following endotracheal intubation in a dog associated with overinflation of the endotracheal tube cuff and multiple changes in position.

Use of sodium nitroprusside in the anaesthetic protocol of a patent ductus arteriosus ligation in a dog

Patent ductus arteriosus (PDA) is one of the most common congenital cardiac abnormalities in the dog. Sodium nitroprusside has been proposed as an infusion during PDA ligation as the resultant nitric oxide production causes hypotension thereby facilitating surgical dissection and decreasing the risk of haemorrhage. This case report details how the method described did not decrease blood pressure and therefore had no beneficial effects. It is speculated that the lack of response may have been due to tachyphylaxis. Other drugs may be preferred to induce deliberate hypotension in the dog.

Suspected venous air embolism in a horse

A horse which had had a caecal impaction for 10 days was treated by means of an ileocolostomy [corrected] but failed to respond satisfactorily. Before a second laparotomy was performed it was observed to have dislodged the extension set from a jugular catheter and air was heard being sucked into the vein. It became very agitated but was anaesthetised again and the impaction was removed through an incision in the apex of the colon [corrected] After recovering from the anaesthesia it developed severe signs of pruritus which subsided only after 12 hours. These signs were considered most likely to have resulted from a venous air embolism.

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

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

Pre-operative and anaesthesia-related risk factors for mortality in equine colic cases

Mortality rates for horses that have undergone emergency abdominal surgery are higher than for other procedures. Here, multivariable modelling of data from 774 surgical colic cases is used to identify pre-operative and anaesthesia-related variables associated with intra- and post-operative mortality. Intra-operative mortality was significantly (P<0.05), and positively associated with heart rate and packed cell volume (PCV) at admission, and negatively associated with the severity of pain. Post-operative mortality increased with increasing age and PCV at admission. Draught horses, Thoroughbreds and Thoroughbred-cross horses carried a significantly worse prognosis. We detected a small but significant variability in the risk of intra-operative death amongst referring veterinary surgeons. Different anaesthetic induction agents, inhalation maintenance agents and the use, or not, of intermittent positive pressure ventilation had no significant effect on risk of death. We conclude that cardiovascular compromise, level of pain, age, and breed are all associated with the risk of mortality in equine surgical colic cases.