Repeatability, reproducibility, and effect of head position on central venous pressure measurement in standing adult horses.

BACKGROUND: Central venous pressure (CVP) is a used as an estimation of intravascular volume status in various species. Techniques for measuring CVP in horses have been described, but the repeatability of these readings at a single time point or over time has not been established. HYPOTHESIS: That CVP measurements in healthy adult horses would be repeatable at each time point, that these readings would be reproducible over time, and that alteration in head position relative to the heart would alter CVP. ANIMALS: Ten healthy adult research horses. METHODS: In an experimental study, horses were instrumented with a central venous catheter. Readings were taken in triplicate q6h for 2 days by water manometry, and twice daily with the head in neutral, elevated, and lowered positions by electronic manometry. RESULTS: Variation in the "neutral" measurements obtained at each time point was <0.1 ± 1.0 cmH(2)O (P = .718). There was a significant decrease in CVP over time (P = .015), which was eliminated when results were controlled for acute decrease in body weight of -1.35% (presumed hypohydration because of lack of acclimatization and decreased water intake). Head height had a significant and directional effect on CVP in that the elevated head position decreased CVP -2.0 ± 6.5 cmH(2)O (P < .001) while the lowered head position increased CVP by 3.7 ± 5.5 cmH(2)O (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: CVP values obtained by water manometry were repeatable in adult horses, but were reproducible only when controlled for changes in hydration. Care should be taken to maintain consistency in head position to prevent erroneous readings.

Comparison of water manometry to 2 commercial electronic pressure monitors for central venous pressure measurement in horses.

BACKGROUND: Central venous pressure (CVP) customarily has been measured in veterinary patients with water manometry. However, many institutions are now using stallside electronic monitors in both anesthesia and intensive care units for many aspects of patient monitoring. HYPOTHESIS: Electronic stall side monitoring devices will agree with water manometry for measurement of CVP in horses. ANIMALS: Ten healthy adult horses from the university research herd. METHODS: Central venous catheters were placed routinely, and measurements were obtained in triplicate with each of the 3 methods every 12 hours for 3 days. Data were analyzed by a Lin concordance correlation coefficient and modified Bland-Altman limits of agreement, with all devices compared pairwise. RESULTS: Compared with water manometry, agreement (bias) of the Passport was -1.94 cmH2O (95% limits of agreement, -8.54 to 4.66 cmH2O) and of the Medtronic was -1.83 cmH2O (95% limits of agreement, -8.60 to 4.94 cmH2O). When compared with the Passport, agreement of the data obtained with the Medtronic was 0.27 cmH2O (95% limits of agreement, -4.39 to 4.93 cmH2O). CONCLUSIONS AND CLINICAL IMPORTANCE: These data show that both electronic monitors systematically provide measurements that are approximately 2 cmH2O lower than water manometry, but differences between the 2 electronic devices are small enough (< 0.5 cmH2O) to be considered clinically unimportant. This discrepancy should be taken into account when interpreting data obtained with these monitoring devices.

The effects of hypohydration on central venous pressure and splenic volume in adult horses.

BACKGROUND: Central venous pressure (CVP) is used in many species to monitor right-sided intravascular volume status, especially in critical care medicine. HYPOTHESIS: That hypohydration in adult horses is associated with a proportional reduction in CVP. ANIMALS: Ten healthy adult horses from the university teaching herd. METHODS: In this experimental study, horses underwent central venous catheter placement and CVP readings were obtained by water manometry. The horses were then deprived of water and administered furosemide (1 mg/kg IV q6h) for up to 36 hours. Weight, CVP, vital signs, PCV, total protein (TP), and serum lactate were monitored at baseline and every 6 hours until a target of 5% decrease in body weight loss was achieved. The spleen volume was estimated sonographically at baseline and peak volume depletion. Linear regression analysis was used to assess the association of CVP and other clinical parameters with degree of body weight loss over time. RESULTS: There was a significant association between CVP and decline in body weight (P < .001), with a decrease in CVP of 2.2 cmH(2)O for every percentage point decrease in body weight. Other significant associations between volume depletion and parameters measured included increased TP (P = .007), increased serum lactate concentration (P = .048), and decreased splenic volume (P = .046). There was no significant association between CVP and vital signs or PCV. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings suggest that CVP monitoring might be a useful addition to the clinical evaluation of hydration status in adult horses.

Prospective evaluation of coagulation in critically ill neonatal foals.

BACKGROUND: Coagulopathy is a potentially underrecognized complication of sepsis and septic shock in critically ill neonatal foals. HYPOTHESIS: Critically ill neonatal foals have abnormalities in coagulation that are associated with disease severity and outcome. ANIMALS: Foals <72 hours old admitted to a neonatal intensive care unit. METHODS: Prospective, observational study. Blood was collected at admission, 24, and 48 hours for platelet count, prothrombin time, activated partial thromboplastin time, antithrombin activity and concentrations of fibrin degradation products, and fibrinogen in plasma from all foals. RESULTS: Sixty-three foals were enrolled and classified as Septic Shock (12), Septic (28), and Other (23). At least 1 abnormal value was found in 18/28 (64%) samples from the Septic Shock group, 66/85 (78%) from the Septic group, and 30/59 (51%) from the Other group (P= .01). Coagulopathy (3 or more abnormal values) was present in 7/28 (25%) samples in the Septic Shock group, 14/85 (16%) samples in the Septic group, and 3/59 (5%) samples in the Other group (P= .0028). Clinically detectable bleeding occurred in 8/12 (67%) Septic Shock cases, 11/28 (39%) Septic cases, and 3/23 (13%) Other cases (P= .009). Foals in Septic Shock were 12.7 times more likely to have clinical evidence of bleeding than those in the Other group (95% CI 2.3-70, P= .004). Treatment with fluids or plasma did not have a detectable effect on coagulation values. CONCLUSIONS AND CLINICAL IMPORTANCE: Coagulopathy commonly occurs in critically ill neonatal foals, especially those with sepsis and septic shock.

Retrospective study of dystocia in mares at a referral hospital.

REASONS FOR PERFORMING STUDY: The period between the onset of dystocia and its resolution has an important bearing on fetal outcome. There are few published data on which to base decisions regarding optimum management of cases in practice. OBJECTIVES: To evaluate and compare the effects of a coordinated dystocia management protocol (CDMP) with that of a previous protocol of random management on time to resolution and outcome in both an emergency dystocia referral population of mares (referred emergency cases: EM) and in a population of mares residing in hospital due to high risk pregnancy (HRP) concerns that then experience dystocia at parturition. METHODS: Retrospective study performed at a university hospital referral centre of cases presenting from 1991-2004 divided into Group 1 (pre-CDMP) and Group 2 (CDMP). RESULTS: Medical records of 71 cases with dystocia were retrieved and data recorded. For referred emergency cases (EM), time from hospital presentation to resolution decreased significantly by 32 min (P = 0.03) after institution of CDMP. Survival rate of mares at discharge was 86%. Survival of EM foals was low, with 10% in Group 1 and 13% in Group 2, surviving to discharge. For EM foals delivered alive, survival to discharge was 30% and 43% in Groups 1 and 2, respectively. Median Stage II was significantly (P < 0.001) different at 71 and 282 min for EM foals delivered alive vs. those not alive at delivery, respectively. Median duration of Stage II was also significantly (P < 0.001) different between EM foals surviving and not surviving to discharge, at 44 and 249 min, respectively. Survival of HRP dystocia foals to discharge was 79%. CONCLUSIONS: Although CDMP reduced the time from presentation at the hospital to resolution significantly for EM, total duration of Stage II for EM was unchanged, as was foal outcome. POTENTIAL RELEVANCE: Very early referral of mares with dystocia to referral centres with dystocia management protocols may improve fetal outcome as increased duration of Stage II in the horse affects fetal outcome negatively.

Evaluation of the clinical efficacy of prokinetic drugs in the management of post-operative ileus: can retrospective data help us?

The objectives of the study were to determine whether retrospective data can be used to answer questions about the efficacy of prokinetic agents when used to treat horses with post-operative ileus (POI). We describe prevalence and mortality of POI with reference to treatment with four prokinetic agents. By combining data from two Hospitals a study population of 55 horses with POI following pedunculated lipoma obstruction (PLO) was established. Univariable and multivariable associations were determined between short term survival and potential explanatory variables. With death as outcome in multivariable models, breed and hospital were significantly associated with outcome but the use of prokinetic agents was not (P=0.15). However, sample size estimates indicate the low power of this study to detect differences in outcome. It was not possible definitively to evaluate the efficacy of prokinetics as treatment for POI following PLO using retrospective data. The data were suggestive of limited efficacy of prokinetics as treatment for POI. It is postulated that the identified association between hospital and survival reflects differences in clinician decision making. The study highlights the need for further prospective studies using randomised clinical trials to evaluate accurately the efficacy of prokinetic agents. This report illustrates difficulties with performing retrospective analysis of clinical data to determine the efficacy of treatment regimes.

Results of screw fixation combined with cortical drilling for treatment of dorsal cortical stress fractures of the third metacarpal bone in 56 Thoroughbred racehorses.

The purpose of this study was to evaluate screw fixation with cortical drilling as a surgical treatment for dorsal cortical stress fractures of MCIII in the Thoroughbred racehorse. Details of age, sex, limb affected, fracture assessment, and post operative recommendations were obtained from medical records and radiographs. Fracture healing was assessed radiographically at the time of screw removal. Performance evaluation was determined from race records obtained from The Jockey Club Information System, Lexington, Kentucky. Fifty-six Thoroughbred racehorses were treated surgically for stress fracture of MCIII with screw fixation and cortical drilling. Stress fractures occurred primarily in the left front limb of the male 3-year-olds, in the dorsolateral cortex of the middle third of MCIII. Ninety-seven percent of the fractures travelled in a dorsodistal to palmaroproximal direction. Median period to screw removal was 2.0 months. Evaluation at time of screw removal revealed 98% of single stress fractures of the left front limb were healed radiographically. Median period to resume training was 2.75 months (single stress fractures); median period to race was 7.62 months. There was no statistically significant difference in earnings/start before and after surgical intervention. Of the 63 fractures treated, two recurred. There were no catastrophic failures, and no incisional infections.

Lateral buccotomy for removal of a supernumerary cheek tooth in a horse.

A 3-year-old female Standardbred was admitted for evaluation of a firm swelling on the right side located rostral to the facial crest and a firm intraoral swelling located rostral to the erupted cheek teeth. Examination of skull radiographs revealed a supernumerary cheek tooth rostral to the erupted third premolar. The supernumerary tooth was removed via lateral buccotomy. The horse did not have complications after surgery and resumed racing. Lateral buccotomy should be considered for removal of rostrally located maxillary or mandibular cheek teeth. Supernumerary cheek teeth can be found in locations in the upper dental arcade, other than caudal to the last molar.