Use of plasma ionized calcium levels and Ca2+substitution response patterns as prognostic parameters for ileus and survival in colic horses

Performance of predictive models of survival in horses undergoing emergency exploratory laparotomy for colic

Objective

To evaluate previously published predictive survival models in a population of horses undergoing colic surgery in the midwestern United States.

Study design

Retrospective cohort study; single referral hospital.

Animals

A total of 260 horses met the inclusion criteria.

Methods

Medical records of horses undergoing surgical treatment for colic were reviewed. Previously published models were applied to cohort data to predict outcome. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for prediction of short‐term survival were calculated.

Results

Single‐variable and multivariable models performed similarly for prediction of survival, with a mean 79% sensitivity (range: 44%–94%), 48% specificity (range: 22%–83%), 63% PPV (range: 56%–72%), 73% NPV (range: 60%–83%), and 64% accuracy (range: 59%–72%). Blood lactate ≤6 mmol/l and the colic severity score (CSS) were highly sensitive for prediction of survival; however, both had poor specificity.

Conclusion

Single‐variable and multivariable predictive models did not perform as well for prediction of survival in the study cohort compared to original reports, suggesting that population‐specific factors contribute to patient survival.

Clinical significance

Predictive models of survival developed in one population may be less reliable when used to predict outcome in horses undergoing colic surgery from an independent population. Additional model testing and refinement using data from multiple surgical centers could be considered to improve prediction of outcome for horses undergoing laparotomy for treatment of colic.

Development of a Colic Scoring System to Predict Outcome in Horses

Acute abdominal pain in the horse is a common emergency presenting to equine practices. The wide variety of etiologies makes prognosticating survival a challenge. A retrospective, multi-institutional clinical study was performed to determine clinical parameters associated with survival of horses with colic, and to use them to develop a colic survival scoring system. The scoring system was then validated using clinical data in the prospective portion of the study. Medical records from 67 horses presenting for acute abdominal pain were evaluated to develop the colic assessment score. Twenty eight variables were compared between survivors and non-survivors and entered into logistic regression models for survival. Of these, six variables were included in the colic assessment score. A total colic assessment score range was from 0 to 12, with the highest score representing the lowest probability of survival. The optimal cutoff value to predict survival was seven resulting in an 86% sensitivity and 64% specificity with a positive predictive value of 88% and a negative predictive value of 57%. Data from 95 horses presenting for abdominal pain to two equine hospitals was then collected prospectively to validate the colic assessment score. Horses from the prospective portion of the study that received a score >7 were classified as predicted to die and those with a score ≤7 were predicted to survive. The classification was compared to the actual outcome, of which the sensitivity, specificity, positive and negative predictive values of the colic assessment score were 84, 62, 88, and 52%, respectively.

Retrospective evaluation of the effect of intravenous fluid administration on development of postoperative reflux in horses with colic (2004-2012): 194 horses

OBJECTIVE

To evaluate the role of intravenous fluid volume and electrolyte supplementation on the development of postoperative reflux (POR) in horses undergoing celiotomy for colic.

DESIGN

Case-control study spanning 2004-2012 for horses undergoing celiotomy for colic.

SETTING

University teaching hospital.

ANIMALS

Sixty-seven client-owned horses >1 year of age with POR were each matched to 2 controls with similar surgical lesions that did not demonstrate POR.

MEASUREMENTS AND MAIN RESULTS

Survival was significantly lower in cases (65.7%) than controls (96.1%). Factors found to be associated with POR included decreased net fluid volume administered on day 1 postoperatively, increased age, and performing a resection and anastomosis. Mean time until onset of POR was 20.4 hours postoperatively. PCV was significantly higher immediately following surgery and at 24 hours postoperatively in horses that developed POR compared with matched controls. There was no association between electrolyte values at presentation or administration of potassium, calcium, or magnesium in the postoperative period and the subsequent development of reflux.

CONCLUSIONS

In the perioperative period, IV fluid volume overload and electrolyte abnormalities were not contributing factors in the development of POR in this population of surgical colic patients. Close postoperative monitoring with consideration and correction of pre- and postoperative fluid deficits is recommended.

Clinical features and management of equine post operative ileus: Survey of diplomates of the European Colleges of Equine Internal Medicine (ECEIM) and Veterinary Surgeons (ECVS)

REASONS FOR PERFORMING STUDY

There is a need for an improved understanding of equine post operative ileus (POI), in terms of both clinical definition and optimal management. Although the pharmacological strategies that are used to treat POI continue to evolve, little is known about the supplementary strategies used to prevent and manage this condition.

OBJECTIVES

To report the current strategies used to diagnose, prevent and manage POI following emergency abdominal surgeries.

STUDY DESIGN

Cross-sectional survey.

METHODS

An electronic survey invitation was sent by email to 306 European college diplomates (European Colleges of Equine Internal Medicine, ECEIM n = 120, and Veterinary Surgeons, ECVS n = 186).

RESULTS

The response rate was 33% (100 of 306). The median reported estimated incidence of POI was 10-20%. The presence of reflux on nasogastric intubation was the main criterion used to define POI. Lesions involving the small intestine were thought to be the leading risk factors for developing POI. Anti-inflammatory drugs, antimicrobial drugs and i.v. fluids were the primary preventative strategies when managing cases at high risk for POI. Flunixin meglumine and lidocaine were the drugs most commonly used to treat horses with POI. Supplementary preventative and treatment strategies for POI included control of endotoxaemia, fluid therapy, early ambulation and judicious timing of post operative feeding.

CONCLUSIONS

Appreciation of the potential risk factors associated with the development of POI appeared to have an impact on the choice of management strategies that are implemented. The majority of ECEIM and ECVS Diplomates in the survey used flunixin meglumine and lidocaine, often in combination, to treat horses with POI, which is likely to reflect the contributory role of inflammation in its pathophysiology. Various supplementary strategies were used to prevent and manage POI risk factors intraoperatively and post operatively.

Undetected hypoparathyroidism: An unusual cause of perioperative morbidity

Routine investigation of serum calcium is not recommended in ASA one and two patients unless abnormalities of calcium metabolism are clinically suspected. The clinical features of hypocalcaemia can often be subtle and may manifest in the presence of associated factors. Hypoparathyroidism, an important cause of hypocalcaemia, often presents as soft tissue calcification (ostosis). Ligamentum flavum ostosis can present with compressive myelopathy requiring laminectomy. We report a case of ligamentum flavum ostosis and subclinical hypocalcaemia due to hypoparathyroidism, who went undetected pre-operatively resulting in significant post-operative morbidity.

Sequential plasma lactate concentrations as prognostic indicators in adult equine emergencies

BACKGROUND

Sequential lactate concentration ([LAC]) measurements have prognostic value in that hospitalized humans and neonatal foals that have a delayed return to normolactatemia have greater morbidity and case fatality rate.

HYPOTHESIS

Prognosis for survival is decreased in horses with a delayed return to normal [LAC].

ANIMALS

Two hundred and fifty adult horses presented for emergency evaluation excepting horses evaluated because of only ophthalmologic conditions, superficial wounds, and septic synovitis without systemic involvement.

METHODS

Prospective observational study. [LAC] was measured at admission and then at 6, 12, 24, 48, and 72 hours after admission. The change in [LAC] over time ([LAC]deltaT) was calculated from changes in [LAC] between sampling points.

RESULTS

Median [LAC] was significantly (P < .001) higher at admission in nonsurvivors (4.10 mmol/L [range, 0.60-18.20 mmol/L]) when compared with survivors (1.30 mmol/L [range, 0.30-13.90 mmol/L]) and this difference remained at all subsequent time points. The odds ratio for nonsurvival increased from 1.29 (95% confidence interval 1.17-1.43) at admission to 49.90 (6.47-384) at 72 hours after admission for every 1 mmol/L increase in [LAC]. [LAC]deltaT was initially positive in all horses but became negative and significantly lower in nonsurvivors for the time periods between 24-72 hours (- 0.47, P = .001) and 48-72 hours (- 0.07, P = .032) when compared with survivors (0.00 at both time periods) consistent with lactate accumulation in nonsurvivors.

CONCLUSIONS AND CLINICAL IMPORTANCE

These results indicate that lactate metabolism is impaired in critically ill horses and [LAC]deltaT can be a useful prognostic indicator in horses.

A comparison of total calcium, corrected calcium, and ionized calcium concentrations as indicators of calcium homeostasis among hypoalbuminemic dogs requiring intensive care

OBJECTIVE

(1) To evaluate whether total calcium (tCa) correlates with ionized calcium (iCa) in hypoalbuminemic dogs; (2) to evaluate whether calcium adjusted for albumin (Alb), or total protein (TP), or both accurately predict iCa concentrations and hence can be used to monitor calcium homeostasis in critically ill hypoalbuminemic dogs; and (3) to evaluate factors associated with any potential discrepancy in calcium classification between corrected total and ionized values.

DESIGN

Prospective observational clinical study.

SETTING

Small animal intensive care unit in a veterinary medical teaching hospital.

ANIMALS

Twenty-eight client-owned dogs with hypoalbuminemia.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

iCa was determined using ion-specific electrode methodology, on heparinized plasma. The tCa concentration was adjusted for Alb and TP using published equations. In total 29% (8/28) of the hypoalbuminemic, critically ill dogs in this study were hypocalcemic at intensive care unit admission, as determined by iCa measurement. Corrected calcium values failed to accurately classify calcium status in 67.9% and 64.3% of cases, according to whether the Alb-adjusted or TP-adjusted values, respectively, were used. The sensitivity and specificity of the tCa to evaluate hypocalcemia was 100% and 47%, respectively. The sensitivity and specificity of the correction formulae were 37.5% and 79% for the Alb-adjusted values and 37.5% and 74% for TP-adjusted values. tCa overestimated the presence of hypocalcemia and underestimated the presence of normocalcemia, while corrected calcium values overestimated the presence of normocalcemia and underestimated the presence of hypocalcemia.

CONCLUSIONS

Calcium homeostasis in hypoalbuminemic critically ill dogs should be evaluated by iCa concentrations rather than tCa or calcium adjusted for Alb or TP. Given that tCa has 100% sensitivity for detecting hypocalcemia in this population it is recommended that all hypoalbuminemic and critically ill patients with low tCa should be evaluated with an iCa measurement.

Postoperative ileus: pathogenesis and treatment

Surgical manipulation of the intestines activates intestinal macrophages that release cytokines and nitric oxide, which results in inhibition of intestinal motility. Subsequent infiltration of circulating leukocytes into the intestinal wall contributes to cytokine and nitric oxide release and exacerbates ileus. Other factors contributing to ileus are endotoxemia; edema of the intestine wall subsequent to excessive fluid therapy; hypocalcemia; and long abdominal incisions. Because treatment of ileus with prokinetic drugs has not proven to be very effective, efforts should be directed at reducing its severity. Strategies which reduce the severity of ileus include pretreatment with a nonsteroidal anti-inflammatory drug, minimizing the length of the abdominal incision, reducing intestinal manipulation, intraoperative lidocaine infusion, correction of hypocalcemia, limiting the volume of intravenous fluids to prevent intestinal edema, and administration of alpha(2) antagonists.

Prognosticating equine colic

Prognosticating survival in horses with colic is challenging because of the number of diseases and pathophysiologic processes that can cause the behavior. Although the treatment of horses with colic has improved dramatically over the years, case fatality can still be high because of the delay in recognizing the problem, the time delay inherent in receiving veterinary care, and the lack of effective treatment for the more severe diseases. Intensive case management and surgery for these horses may be expensive and emotionally draining for owners; therefore, providing an accurate prognosis is key to decisions needed for case management. This article is dedicated to recent advances in applying a prognosis for survival in horses at higher risk for a fatal outcome.

Rapid calcitonin response to experimental hypercalcemia in healthy horses

Calcium has important physiological functions, and disorders of calcium homeostasis are frequent in horses. We have made important progress understanding equine calcium homeostasis; however, limited information on equine calcitonin (CT) is available, in part because of the lack of validated CT assays. To determine the CT response to high ionized calcium (Ca(2+)) concentrations in healthy horses, we induced hypercalcemia in 10 healthy horses using a calcium gluconate 23% solution (5mg/kg; 120 mL/500 kg horse) infused over 4 min. Four horses were infused with 120 mL of 0.9% NaCl and used as controls. We validated a human-specific CT radioimmunoassay for use in horses. Serum Ca(2+) concentrations increased from 6.2+/-0.3mg/dL to 9.9+/-0.5mg/dL (4 min; P<0.01). Serum CT increased from 16.7+/-8.0 pg/mL to 87.1+/-55.8 pg/mL at 2 min, and 102.5+/-51.1 pg/mL at 4 min (P<0.01). Serum CT returned to baseline by 20 min, whereas serum Ca(2+) returned to baseline by 40 min. Of interest, CT concentrations returned to baseline despite hypercalcemia, suggesting thyroid gland C-cell CT depletion. Resting CT values higher than 40 pg/mL were considered abnormally elevated. No significant changes in serum Ca(2+) or CT concentrations were found in control horses. The coefficients of variation for the CT radioimmunoassay were lower than 11.9%. We conclude that the equine thyroid gland C-cell responds quickly to changes in extracellular Ca(2+) concentrations by secreting large quantities of CT into the systemic circulation, indicating that CT is important in equine calcium homeostasis. The human CT radioimmunoassay can be used to measure changes in equine CT.

Calcium regulating hormones and serum calcium and magnesium concentrations in septic and critically ill foals and their association with survival

BACKGROUND

Disorders of calcium regulation are frequently found in humans with critical illness, yet limited information exists in foals with similar conditions including septicemia. The purpose of this study was to determine whether disorders of calcium exist in septic foals, and to determine any association with survival.

HYPOTHESIS

Blood concentrations of ionized calcium (Ca(2+)) and magnesium (Mg(2+)) will be lower in septic foals with concomitant increases in parathyroid hormone (PTH), calcitonin (CT), and parathyroid-related peptide (PTHrP) compared with healthy foals. The magnitude of these differences will be negatively associated with survival.

ANIMALS

Eighty-two septic, 40 sick nonseptic, and 24 healthy foals of <or=7 days were included.

METHODS

Prospective, observational study. Blood was collected at initial examination for analysis. Foals with positive blood culture or sepsis score >or=14 were considered septic. Foals with disease other than sepsis and healthy foals were used as controls. Hormone concentrations were measured with validated immunoassays.

RESULTS

Septic foals had decreased Ca(2+) (5.6 versus 6.1 mg/dL, P < .01) and increased serum PTH (16.2 versus 3.2 pmol/L, P < .05), and phosphorus concentrations (7.1 versus 6.3 mg/dL, P < .01). No differences in serum Mg(2+), PTHrP, and CT concentrations were found. Nonsurviving septic foals (n = 42/82) had higher PTH concentrations (41.1 versus 10.7 pmol/L, P < .01) than survivors (n = 40/82).

CONCLUSIONS AND CLINICAL IMPORTANCE

Septic foals were more likely to have disorders of calcium regulation compared with healthy foals, where hyperparathyroidemia was associated with nonsurvival.

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

OBJECTIVE

To assess the changes in colloid osmotic pressure (COP) in horses undergoing surgery for colic.

STUDY DESIGN

Prospective clinical evaluation.

ANIMALS

Twenty-nine adult horses presented for emergency laparotomy.

METHODS

Horses were premedicated with intravenous (IV) xylazine and anesthesia was induced with ketamine, diazepam and guaifenesin and was maintained with isoflurane as required. Lactated Ringer's solution (LRS) was given to all horses during anesthesia. Blood was collected in heparin before, and every 30 minutes during, anesthesia to measure COP, total protein concentration (TP), osmolality, packed cell volume, electrolytes, glucose and lactate. In addition, COP was estimated using different formulas previously described for horses.

RESULTS

Before anesthesia, COP and TP were 18.7 +/- 2.2 mmHg (2.49 +/- 0.29 kPa) and 6.3 +/- 0.7 g dL(-1), respectively. The horses received a mean +/- SD of 19.5 +/- 3.9 mL kg(-1) hour(-1) (range 15-25 mL kg(-1)hour(-1)) of LRS during anesthesia. The COP and TP decreased linearly (R(2) = 0.99, p < 0.01) during anesthesia and reached the lowest point at the end of anesthesia with a COP of 11.6 +/- 1.6 mmHg (1.55 +/- 0.21 kPa) and TP of 4.4 +/- 0.4 g dL(-1). The Pearson correlation coefficient for COP versus TP was r(2) = 0.78. Calculation of COP from TP concentrations showed that two formulas could predict COP to within 1 mmHg (0.13 kPa) (Thomas & Brown 1992; Boscan et al. 2007).

CONCLUSIONS AND CLINICAL RELEVANCE

Colloid osmotic pressure, like TP, decreased greatly over the course of crystalloid fluid infusion during anesthesia for laparotomy in horses with colic. This change may predispose the animal to tissue edema with subsequent morbidity.