Use of clinical pathology in evaluation of horses with colic

Clinical pathology is a valuable adjunct to physical examination of cases of colic. The present review considers evaluation of cases of colic for three main purposes: (1) making a prognosis, (2) deciding whether to operate, and (3) making a diagnosis. Blood tests noted to be useful for prognostication were hematocrit, lactate and urea nitrogen concentrations, pH, anion gap, fibrin/fibrinogen degradation products, antithrombin III activity, prothrombin time, and thrombin time. Horses with a poor prognosis often have relative polycythemia, marked lactic acidosis, high anion gap, azotemia, and coagulation abnormalities evidenced by increased fibrin/fibrinogen degradation products, decreased antithrombin III activity, and prolonged prothrombin and thrombin times. The decision to operate is usually a clinical one, supported by relative polycythemia, hyperglycemia, and, possibly, abnormal peritoneal fluid analysis. Diagnosis of the primary problem (causing the colicky signs) is also often based largely on physical examination. However, peritoneal fluid analysis provides worthwhile data, especially in cases of peritonitis or intestinal ischemia and infarction.     

Evaluation of peritoneal fluid lactate as a marker of intestinal ischaemia in equine colic

REASONS FOR PERFORMING STUDY: The most common cause of death as a direct result of colic is acute circulatory failure secondary to intestinal ischaemia. Early and accurate recognition of ischaemic bowel is essential to decrease complications and increase survival. Blood to peritoneal lactate values have been evaluated as a prognostic indicator, but lactate values characterised by type of lesion have not been reported. HYPOTHESIS: Plasma and peritoneal lactate values are higher in horses with intestinal ischaemia secondary to a strangulating obstruction (ISSO). METHODS: Venous blood and peritoneal fluid were collected sequentially from 20 clinically healthy horses and 189 horses admitted for colic during a one-year period. Blood gas, pH, electrolyte (K+, Na+, Ca++, Cl-), glucose and lactate values were determined for blood and peritoneal fluid samples; other values recorded for peritoneal fluid included gross appearance, total protein and nucleated cell count. Information regarding diagnosis, treatment and outcome was retrieved from the medical records. RESULTS: Peritoneal and plasma levels of lactate were lower in control compared to clinical cases. Horses with ISSO had a higher peritoneal lactate value (8.45 mmol/l) than those with nonstrangulating obstruction (2.09 mmo/l). Factors with the strongest correlations with the presence of ISSO were changes in the gross appearance of the peritoneal fluid and values of peritoneal fluid chloride, pH and log10 lactate. CONCLUSIONS: Analysis of peritoneal fluid gross appearance, pH, lactate and chloride can be used for diagnosis of ISSO. POTENTIAL RELEVANCE: Peritoneal fluid lactate is a better predictor of ISSO than blood lactate and may aid in early detection of catastrophic peritoneal lesions such as intestinal strangulation and rupture.     

Evaluation of plasma catecholamine and serum cortisol concentrations in horses with colic

OBJECTIVE: To evaluate plasma epinephrine and norepinephrine concentrations and serum cortisol concentration in horses with colic and assess the relationship of these variables with clinical signs, routinely measured clinicopathologic variables, and outcome in affected horses. DESIGN: Prospective observational study. ANIMALS: 35 horses with colic. PROCEDURE: Blood samples were collected within 30 minutes of arrival at the veterinary hospital from horses referred because of colic. Plasma and serum samples were analyzed for cortisol, epinephrine, norepinephrine, lactate, and electrolyte concentrations and acid-base variables. Heart rate at admission and outcome (survival or nonsurvival) were recorded. Univariate logistic regression was used to calculate crude (unadjusted) odds ratios and 95% confidence intervals. RESULTS: Of the 35 horses with colic, 26 survived. Higher plasma epinephrine, plasma lactate, and serum cortisol concentrations were significantly associated with increased risk of nonsurvival, but plasma norepinephrine concentration was not associated with outcome. Plasma epinephrine concentration was significantly correlated with heart rate (r = 0.68), plasma lactate concentration (r = 0.87), blood pH (r = -0.83), anion gap (r = 0.74), and base excess (r = -0.81). CONCLUSIONS AND CLINICAL RELEVANCE: The risk of death appears to be greater in colic-affected horses with high circulating concentrations of epinephrine and cortisol. The correlation of epinephrine with other biochemical markers of illness severity and with heart rate indicates that the degree of sympathetic activation in horses with colic can be inferred from routinely measured variables.     

Evaluation of the usefulness of the portable device Lactate Pro for measurement of lactate concentrations in equine whole blood.

Blood lactate measurements are commonly used in exercising horses to determine the onset of lactate accumulation and in colic patients to assess clinical status and to indicate prognosis. To study the usability of a portable blood lactate meter based on dry chemistry (Lactate Pro), the data from this instrument were compared to data from a laboratory-used lactate meter based on wet chemistry (ABL 605 blood gas analyzer [ABL]). Heparinized blood samples were obtained from horses participating in a jumping experiment (n = 9), from horses cantering at maximal speed on a racetrack (n = 7), and from patients admitted to the Department of Equine Sciences at Utrecht University for severe colic (n = 13). Seventeen of these samples were tested in duplicate on both instruments to determine the repeatability of the measurements. Blood lactate concentrations measured with the Lactate Pro ranged from 0.8-17.6 mmol/liter and with the ABL from 1.0-18.6 mmol/liter. The correlation between lactate concentrations obtained using the Lactate Pro and values from the ABL was 0.90, and the relationship was represented by the following formula: y = 0.90 . x + 0.36, indicating a linear relationship between values produced by the ABL and Lactate Pro. The repeatability for the Lactate Pro was high (0.997), which is comparable to the ABL (0.999).     

Lactate Dehydrogenase Activity in Abdominal Fluid From Horses With Colic

The purpose of this study was to determine whether lactate dehydrogenase (LDH) activity in abdominal fluid could be used as a prognostic indicator in horses with colic. Lactate dehydrogenase activity was measured in 27 abdominal effusions from horses with colic presented to Murdoch University Veterinary Teaching Hospital using three different LDH test methods. Lactate in effusions was also measured in 11 of the horses. Lactate dehydrogenase activity was significantly different for each test method used—the ratio of Randox wet chemistry LDH lactate to pyruvate:Randox wet LDH pyruvate to lactate (P-L):IDEXX dry chemistry P-L was approximately 1:2:4. Lactate dehydrogenase activity in the abdominal effusions was significantly higher with all methods in the horses that died or were euthanized because of abdominal sepsis or advanced neoplasia than in those that survived after treatment for colic signs because of mechanical obstructions or nonseptic abdominal inflammation. Lactate dehydrogenase activity showed moderate-to-good correlation (r = 0.73 to 0.86) with lactate concentration of the fluid. In conclusion, LDH activity in abdominal fluid may be a useful prognostic test in horses with colic. The test method for LDH measurement must be known and remain constant for meaningful interpretation. Significantly higher levels of LDH activity may be present in horses with colic because of sepsis or advanced neoplasia than in those with colic because of nonseptic inflammation or mechanical obstructions that may respond to treatment.     

The usability of peritoneal lactate concentration as a prognostic marker in horses with severe colic admitted to a veterinary teaching hospital

Colic can be a life‐threatening condition in horses and there is a need for parameters that can help determine the prognosis and need for surgery. The aim of the study was to investigate whether peritoneal fluid (PF) lactate concentration is useful for this purpose in horses with severe colic presented to a veterinary hospital. During a 16 month period, the peritoneal fluid (PF) lactate concentration was measured in 74 of 760 colic horses admitted to the Utrecht University equine clinic using a portable analyser. When comparing survivors and nonsurvivors, heart rate, PF and blood lactate concentrations and blood glucose concentration were significantly higher in horses that did not survive. No horse with a PF lactate concentration >9.4 mmol/l survived. The presence of a strangulating lesion was also significantly associated with nonsurvival, as was PF colour: no horse with red PF survived in the present series. In horses with yellow PF, the blood glucose concentration was correlated with the presence of a strangulating intestinal lesion. Peritoneal lactate concentrations can be easily and rapidly measured using a portable analyser and may be useful in assessing the prognosis and/or need for surgery in equine colic cases.     

Arterial lactate concentration, hospital survival, sepsis and SIRS in critically ill neonatal foals

REASONS FOR PERFORMING STUDY: Blood lactate concentration has been shown to be a useful clinical indicator in human patients, but has not been formally investigated in critically ill foals. OBJECTIVE: To investigate the association of blood lactate with hospital survival, markers of cardiovascular status, metabolic acid base status, sepsis and systemic inflammatory response syndrome (SIRS). METHODS: A database containing clinical, haematological, plasma biochemical and hospital outcome data on neonatal foals referred to an intensive care unit in 2000-2001 was analysed. Seventy-two foals for which arterial lactate was measured at admission were included in the study. RESULTS: Sixty-one foals had an admission lactate concentration > 2.5 mmol/l. Admission lactate was statistically associated with hospital survival, mean arterial pressure, blood creatinine concentration, bacteraemia, anion gap, lactate concentration at 18-36 h after admission and evidence of SIRS, but not with packed cell volume or heart rate. Lactate at 18-36 h was also associated with survival and evidence of SIRS. Anion gap, base excess, base excess due to unidentified anions (BEua), simplified strong ion gap or bicarbonate correctly classified foals for presence of hyperlactaemia (> 5 mmol/l) in < or = 80% of animals. CONCLUSIONS: Admission blood lactate gives important prognostic information. Lactate should be measured rather than assumed from the anion gap, base excess, BEua, simplified strong ion gap or bicarbonate. POTENTIAL RELEVANCE: Blood lactate concentrations at admission are clinically relevant in neonatal foals and warrant further investigation. This should include the clinical value of measuring changes in lactate in response to treatment.     

Plasma endotoxin in horses presented to an equine referral hospital: correlation to selected clinical parameters and outcomes

Reasons for performing study: Endotoxaemia is frequently presumed on the basis of clinical signs in horses with colic. Objective: Measurements of plasma endotoxin (LPS) are rarely made in clinical cases and there is little information on the correlations between this variable, clinical variables and outcomes. Objectives: To measure LPS levels in plasma of horses presented to the Philip Leverhulme Equine Hospital on admission and daily for up to 4 days and to relate LPS levels to selected clinical parameters, such as heart rate and packed cell volume, and outcomes. Methods: Blood samples were collected and stored at ‐20°C prior to assay of the plasma using a validated kinetic chromogenic Limulus amoebocyte lysate (LAL) assay. Clinical parameters and outcome variables were collected from hospital records. Associations were determined by Chi‐squared test and logistic regression analysis. Results: Daily blood samples were collected from 234 horses. LPS was detected in 26.5% of the study population and in 29% of those horses presented for colic. Horses providing samples with detectable LPS were more likely to die whilst in the hospital than those that did not (P = 0.045). Horses presenting with colic were more likely to have detectable LPS in their plasma than noncolic cases (P = 0.037), although LPS was detected in the plasma of 8 out of 42 noncolic horses. A horse that did not meet the study definition of clinical endotoxaemia was 10 times less likely to provide a positive LPS sample (OR 0.10, 95% CI: 0.05–0.22). Conclusions: The proportion of horses providing samples with detectable LPS was similar to other studies. Potential relevance: LPS was detected in the minority of horses presented with colic. Increased levels of LPS positively correlated with packed cell volume and with risk of mortality in colic cases.     

Colic in geriatric compared to mature nongeriatric horses. Part 1: Retrospective review of clinical and laboratory data

Reason for performing study: It is the impression of some surgeons that geriatric horses have a lower survival rate compared to mature nongeriatric horses following colic surgery. One possible reason for this is that geriatric horses may be more critically ill at admission and have more severe disease than mature nongeriatric horses. Objective: To compare admission historical, physical examination and laboratory data for geriatric and mature nongeriatric horses referred for signs of colic. Methods: Medical records of horses admitted with a presenting complaint of colic between 2000 and 2006 were reviewed. Geriatric horses ≥16 years (n = 300) and mature nongeriatric horses 4–15 years (n = 300). Information obtained included duration of colic prior to admission, admission level of pain, heart rate, intestinal borborygmi, packed cell volume (PCV), plasma creatinine and blood lactate concentrations and peritoneal fluid total protein. Data were analysed using a Chi‐squared test or an analysis of variance. Level of significance was P<0.05. Results: There was no difference between geriatric and mature horses in the duration of colic prior to admission or in admission heart rate, PCV, or plasma creatinine or blood lactate concentrations. However, geriatric horses were more likely to be moderately painful and less likely to be bright and alert than mature horses; and less likely to have normal intestinal borborygmi than mature horses. Peritoneal fluid total protein concentration was higher in geriatric than mature horses. Conclusions and potential relevance: Geriatric horses presenting with signs of colic had a similar admission cardiovascular status based on heart rate, PCV, and plasma creatinine and blood lactate concentration to mature horses. Geriatric horses, however, may have different causes of colic, which may be more serious than mature horses based on pain, lack of intestinal borborygmi and peritoneal fluid total protein concentration.     

Serial venous lactate measurement following gastrointestinal surgery in horses

BackgroundProspective clinical study of blood lactate concentration in horses undergoing colic surgery is needed to determine utility in outcome prediction.ObjectivesTo evaluate venous lactate measurements in horses following colic surgery, including immediately after anesthetic recovery and daily throughout hospitalization, as well as to determine if lactate concentrations were significantly higher in horses that developed postoperative complications or did not survive to hospital discharge.MethodsHorses > 1 year of age undergoing surgery for colic and recovered from general anesthesia were sampled. A portable lactate meter was used to measure venous samples collected immediately following anesthetic recovery and daily throughout hospitalization. Complications arising during hospitalization and survival to hospital discharge were recorded.ResultsFifty one horses were enrolled, ranging in age from 2 to 29 years. Lactate concentration immediately following anesthetic recovery was higher in horses that developed complications during hospitalization (p = 0.046). The odds of developing complications postoperatively were doubled for horses with a venous lactate concentration > 5 mmol/L. Lactate measurements in non-survivors were significantly higher compared to survivors by 96 h postoperatively (p < 0.006).ConclusionsHigher venous lactate concentrations in the postoperative colic period were associated with an increased risk of complications and death. Results suggest horses with higher venous lactate measurements in recovery are more likely to have postoperative complications, with the odds of developing complications doubled for horses with a venous lactate > 5 mmol/L. Evaluation of venous lactate could provide information on prognosis in the postoperative period for horses with surgical colic.     

Correlation between anion gap, blood L lactate concentration and survival in horses

Blood L lactate concentration and anion gap were measured in 32 horses suspected of having metabolic acidosis. There was good linear correlation between these variables (r = 0.90791, P less than 0.0001) and both were good prognostic indicators. Anion gap was a good indicator of the presence but not the severity of L lactic acidosis and was a slightly better prognostic indicator. The ability to predict survival was not improved by the measurement of L lactate in addition to anion gap.     

Determination of the acid-base status in 50 horses admitted with colic between December 1998 and May 1999

The purpose of the present study was to investigate the acid-base status and the concentration of organic acids in horses with colic caused by various disorders. Blood samples were collected from 50 horses with colic and from 20 controls. No intravenous fluids had been given prior to sample collection. Identified causes of colic included gastric ulceration, small intestinal volvulus, cecal intussusception, cecal rupture, colonic impaction, left dorsal colon displacement, right dorsal colon displacement, colonic volvulus, colitis, peritonitis, and uterine torsion. Thirty-seven horses recovered from treatment of colic, 8 horses were euthanized, and 5 died. Most cases were not in severe metabolic acidosis. In previous studies, most horses presented for diagnosis and treatment of colic were in metabolic acidosis and in shock.     

Colic in the horse. A clinical and clinical chemical study of 42 cases

42 horses were examined. The physical signs with relation to circulatory insufficiency and the abdominal disease were registered following a two-phased examination procedure. Great prognostic value was found in the degree of circulatory insufficiency judged by pulse rate and character, filling of the jugular vein, skin temperature, colour of mucous membranes, capillary refill time, sweating, depression, skin turgor and degree of enophthalmus. In making a causal diagnosis the abdomen was examined for shape, tenderness, peristaltic sounds, gastric dilation by siphoning, abnormal rectal findings and macroscopic changes in peritoneal fluid. Greatest diagnostic difficulties were encountered in cases of intestinal atonia, acute enteritis and torsion of the colon. In selected (severe) cases laboratory tests were obtained. Blood samples were examined for packed cell volume, hemoglobin, red and white blood cell counts, differential white blood cell count, blood gases and acid-base status, lactate, serum total protein and albumin, plasma sodium, potassium, chloride, calcium, magnesium, inorganic phosphorus, glucose, creatinine, BUN, total bilirubin, ASAT, CK, BASP and GGT. Peritoneal fluid was examined for red blood and white cell counts, total protein, specific gravity, pH and lactate, and enzymes as in blood. Laboratory results generally confirmed the clinical signs of shock, and packed cell volume and blood lactate were regarded to be of greatest prognostic interest. Although the performed laboratory information, macroscopic evaluation was thought to reveal sufficient information in most cases. It was concluded that supervening shock is of decisive importance in severe forms of colic, and that a careful and repeated evaluation of the circulatory insufficiency often provides one with a tentative prognosis although the final diagnosis is not obtained. In spite of therapy fatal outcome was found in all seriously shocked horses.     

Use of the Accusport semi-automated analyser to determine blood lactate as an aid in the clinical assessment of horses with colic

The most useful diagnostic methods in the initial evaluation of horses with colic assess the morphological and functional status of the gastrointestinal tract and cardiovascular status. This evaluation is best achieved using a combination of clinical and laboratory data. Blood lactate concentration (BL) is one of these variables. BL rises mainly due to poor tissue perfusion and anaerobic glycolysis associated with shock, providing an indicator of both the severity of disease and its prognosis. A hand-held lactate meter, Accusport, provides a rapid (60 seconds), inexpensive dry-chemical-based determination of BL. This trial evaluated the Accusport's ability to provide BL data as an adjunct to the initial clinical evaluation of horses with colic. The accuracy of the Accusport was tested by evaluation of its interchangeability with the benchmark enzymatic kit evaluation of BL in a trial using data collected firstly from 10 clinically normal control horses and subsequently from 48 horses presented with signs of colic. The BL values were recorded together with the clinical variables of heart rate (HR), capillary refill time (CRT), haematocrit (Hct), and pain character and severity on the initial assessment of the colic horses. Information regarding choice of therapeutic management (medical or surgical) and eventual case outcome (full recovery or died/euthanased) was recorded. The Accusport was found to be interchangeable with the enzymatic kit for recording BL values in colic horses with BL < 10 mmol/l, which is within the BL range associated with survival. The interchangeability of an additional, laboratory-based wet chemical assay for BL, the Stat 7 was simultaneously evaluated for the colic and control horses. The Stat 7 was found to be interchangeable with the enzymatic kit for BL determination of colic horses. No linear associations between BL values with HR, CRT, Hct or pain assessment were observed. No relationship with either selection of therapeutic method or eventual case outcome was observed. All horses with BL >8 mmol/l died or were euthanased.     

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

OBJECTIVE: Hypocalcaemia is a common finding in horses with enterocolitis and severe gastrointestinal disorders. The aims of this study were to investigate in colic horses 1)the parameters related to hypocalcaemia, 2)the influence of hypocalcaemia on outcome and 3)the possible beneficial effect of Ca2+ substitution. DESIGN: Randomized controlled trial. SETTING: Intensive care unit. PATIENTS: One hundred forty-four horses that were admitted with an acute abdomen during a 1.5 year period were enrolled and daily evaluated for clinical criteria and whole blood ionized Ca2+ levels. Colic horses with hypocalcaemia were randomly assigned to receive Ca2+. INTERVENTIONS: Analysis of heparinised whole blood samples. Horses that were assigned to be treated received 400 mEq Ca2+ diluted in 10L of Ringer's lactate solution every 24 h until low reference range limits were obtained or until death. MEASUREMENTS AND MAIN RESULTS: 88% of all colic patients showed blood ionized Ca2+ levels below the reference range at the time of admission. Multivariable analysis revealed that the presence of reflux, signs of endotoxaemia, increased Packed Cell Volume (PCV), alkalinization of pH and the interaction PCV/pH all predispose colic horses to low ionized Ca2+ levels at the time of admission. The Odds for developing ileus during hospitalization are +/- 11.94 times larger for horses in the "very low" calcaemia interval, in comparison with normocalcaemic horses. The Odds for fatal outcome are respectively +/- 9.82 and 8.33 times larger for horses in the "very low" and "low" calcaemia interval. Ca2+ substitution increased the probability of survival, provided that Ca2+ levels could be normalized. The lack of an upward calcaemia response, despite repetitive Ca2+ substitutions, can be guarded as a poor ominous sign. CONCLUSIONS: Hypocalcaemia in colic horses is of prognostic relevance both with regard to survival as to the probability of development of ileus during hospitalization. This study shows the importance of routine measurement of ionized calcium levels in colic horses. Moreover, correction of hypocalcaemia seems to improve clinical outcome.     

Use of plasma ionized calcium levels and Ca(2+) substitution response patterns as prognostic parameters for ileus and survival in colic horses

Summary Objective: Hypocalcaemia is a common finding in horses with enterocolitis and severe gastrointestinal disorders. The aims of this study were to investigate in colic horses (!))the parameters related to hypocalcaemia, (2))the influence of hypocalcaemia on outcome and (3))the possible beneficial effect of Ca(2+ )substitution. Design: Randomized controlled trial. Setting: Intensive care unit. Patients: One hundred forty-four horses that were admitted with an acute abdomen during a 1.5 year period were enrolled and daily evaluated for clinical criteria and whole blood ionized Ca levels. Colic horses with hypocalcaemia were randomly assigned to receive Ca(2+). Interventions: Analysis of heparinised whole blood samples. Horses that were assigned to be treated received 400 mEq Ca(2+) diluted in 10L of Ringer's lactate solution every 24 h until low reference range limits were obtained or until death. Measurements and main results: 88% of all colic patients showed blood ionized Ca levels below the reference range at the time of admission. Multivariable analysis revealed that the presence of reflux signs of endotoxaemia increased Packed Cell Volume (PCV) alkalinization of pH and the interaction PCV/pH all predispose colic horses to low ionized Ca(2+) levels at the time of admission. The Odds for developing ileus during hospitalization are ± 11.94 times larger for horses in the "very low" calcaemia interval in comparison with normocalcaemic horses. The Odds for fatal outcome are respectively ± 9.82 and 8.33 times larger for horses in the "very low" and "low" calcaemia interval. Ca(2+) substitution increased the probability of survival provided that Ca(2+) levels could be normalized. The lack of an upward calcaemia response despite repetitive Ca(2+) substitutions can be guarded as a poor ominous sign. Conclusions: Hypocalcaemia in colic horses is of prognostic relevance both with regard to survival as to the probability of development of ileus during hospitalization. This study shows the importance of routine measurement of ionized calcium levels in colic horses. Moreover correction of hypocalcaemia seems to improve clinical outcome.     

Evaluation of Equine Albumin Solution in Fluid Therapy in Horses with Colic

Equine albumin solution can be a good therapeutic option in fluid replacement for treatment of horses with colic. The purpose of this study was to evaluate the effects of initial fluid therapy with equine albumin solution in horses presenting with colic and mild-to-moderate dehydration, and to compare this therapy with fluid therapy based on crystalloids alone. Nineteen horses of both genders presenting with colic and mild-to-moderate dehydration were used. Animals were randomly assigned to one of two groups (control: fluid therapy based on crystalloid solutions; experimental: fluid therapy based on equine albumin and crystalloid solutions). Physical examination, hematocrit determination, blood gas analysis, serum biochemistry, blood and peritoneal lactate assessment, and measurement of colloid osmotic and arterial pressure were performed at predetermined times. Good results were obtained with equine albumin solution. More fluid is attracted into and maintained in the intravascular compartment, despite infusion of small volumes, as indicated by higher arterial pressure, lower capillary refill time, lower hematocrit and serum protein concentrations, lower colloid osmotic pressure, and better skin turgor. Equine albumin solution has good oncotic action and is a safe fluid therapy option for horses with colic and mild-to-moderate dehydration. Our results suggest it can be a good choice of fluid for correction of severe dehydration, although further research is necessary to determine the adequate dose in such cases.     

A comparison of traditional and quantitative analysis of acid-base and electrolyte imbalances in horses with gastrointestinal disorders

The purpose of this study was to compare traditional and quantitative approaches in analysis of the acid-base and electrolyte imbalances in horses with acute gastrointestinal disorders. Venous blood samples were collected from 115 colic horses, and from 45 control animals. Horses with colic were grouped according to the clinical diagnosis into 4 categories: obstructive, ischemic, inflammatory, and diarrheic problems. Plasma electrolytes, total protein, albumin, pH, pCO2, tCO2, HCO3-, base excess, anion gap, measured strong ion difference (SIDm), nonvolatile weak buffers (A(tot)), and strong ion gap were determined in all samples. All colic horses revealed a mild but statistically significant decrease in iCa2+ concentration. Potassium levels were mildly but significantly decreased in horses with colic, except in those within the inflammatory group. Additionally, the diarrheic group revealed a mild but significant decrease in Na+, tCa, tMg, total protein, albumin, SIDm, and A(tot). Although pH was not severely altered in any colic group, 26% of the horses in the obstructive group, 74% in the ischemic group, 87% in the inflammatory group, and 22% in the diarrheic group had a metabolic imbalance. In contrast, when using the quantitative approach, 78% of the diarrheic horses revealed a metabolic imbalance consisting mainly of a strong ion acidosis and nonvolatile buffer ion alkalosis. In conclusion, mild acid-base and electrolyte disturbances were observed in horses with gastrointestinal disorders. However, the quantitative approach should be used in these animals, especially when strong ion imbalances and hypoproteinemia are detected, so that abnormalities in acid-base status are evident.     

Pulmonary gas exchange and plasma lactate in horses with gastrointestinal disease undergoing emergency exploratory laparotomy: a comparison with an elective surgery horse population

Objective: To characterize pulmonary gas exchange and arterial lactate in horses with gastrointestinal disease undergoing anesthesia, compared with elective surgical horses, and to correlate these variables with postoperative complications and mortality. Study Design: Prospective clinical study. Animals: Horses undergoing emergency laparotomy for acute intestinal disease (n=50) and healthy horses undergoing elective surgery in dorsal recumbency (n=20). Methods: Arterial blood gas analysis was performed at predetermined intervals on horses undergoing a standardized anesthetic protocol. Alveolar–arterial oxygen gradient was calculated. Predictive factors for postoperative complications and death in colic horses were determined. Results: Arterial oxygen tension (P_aO₂) varied widely among horses in both groups. P_aO₂ significantly increased in the colic group after exteriorization of the ascending colon. P_aO₂ and alveolar–arterial oxygen gradient were not significantly different between groups, and neither were correlated with horse outcome. Arterial lactate in recovery ≥5 mmol/L was associated with a 2.25 times greater relative risk of complications and lactate ≥7 mmol/L was associated with a 10.5 times higher relative risk of death. Conclusion: Colic horses in this population were not more likely to be hypoxemic than elective horses, nor was gas exchange impaired to a greater degree in colic horses relative to controls. Arterial lactate sampled immediately after anesthetic recovery was predictive for postoperative complications and death.     

Exacerbation of Hyperlactatemia by Infusion of Lactated Ringer''s Solution in Dogs With Lymphoma

Blood lactate concentrations and acid-base status of six dogs with lymphoma were compared statistically with those from six healthy control dogs before, during, and after a 6-hour infusion of lactated Ringer's solution (LRS). Blood lactate concentrations in dogs with lymphoma were significantly (P less than 0.05) higher immediately before, and at the 1-, 2-, 4-, and 6-hour time periods after infusion when compared with controls. Blood lactate concentrations increased significantly (P = 0.016) after the first hour of infusion in dogs with lymphoma but did not increase in the control dogs. The increase in blood lactate concentrations over baseline values after 1 hour of LRS infusion was significantly (P = 0.008) greater in dogs with lymphoma when compared with controls. Blood lactate concentrations returned to baseline levels after 2 hours of infusion in dogs with lymphoma, suggesting that dogs with lymphoma have a transient inability to handle increased lactate loads when compared with controls. However, the potential to augment lactate use, clearance, or both is present and does occur over time. Blood gas values were not significantly altered within the lymphoma or control dog groups after 6 hours of LRS infusion. Blood bicarbonate concentrations in dogs with lymphoma were significantly decreased before and after LRS infusion when compared with controls.