Blood lactate measurement and interpretation in critically ill equine adults and neonates

Comparison of plasma l-lactate between jugular and cephalic veins in healthy and systemically ill horses using a point-of-care device

OBJECTIVE

To compare plasma l-lactate (LAC) values between samples collected from jugular and cephalic venipuncture in healthy horses and systemically ill horses.

DESIGN

Prospective, experimental study.

SETTING

Large animal university teaching hospital.

ANIMALS

Thirty healthy adult university-owned horses and 43 client-owned horses presenting to the large animal hospital for elective surgical procedures or for emergent medical evaluation of systemic illness.

INTERVENTIONS

Blood samples were collected from the jugular vein (JV) and cephalic vein (CV) and placed in EDTA blood tubes prior to any medical therapy. LAC values were obtained with a handheld lactate meter at the time of blood collection.

MEASUREMENTS AND MAIN RESULTS

LAC was higher in CV samples than JV samples in healthy horses (P < 0.001); however, all values were within the normal reference range. Similarly, LAC was higher in CV samples than JV samples in systemically ill horses (P < 0.001), but the median JV value was within normal reference range (1.9 mmol/L [17.1 mg/dL]), while the median CV value was outside the normal reference range (2.9 mmol/L [26.1 mg/dL]).

CONCLUSIONS

The CV is an alternative venipuncture site for assessing plasma LAC if the JV is not accessible or to preserve the JV for subsequent catheterization. However, in ill horses, the CV value may be outside the reference range when the corresponding JV value would have been within the reference range.

Effects of xylazine and adrenaline combinations: Preliminary clinical application for non-surgical protocols of nephrosplenic entrapment in horses

Background and Aim:

The medical treatment of horses with nephrosplenic entrapment (NSE) of the large colon through administrating phenylephrine and rolling during general anesthesia was effective and less expensive than surgical treatment. However, the selection of drugs for non-surgical treatment of NSE is not a usual method for clinical practice. This study aimed to identify the effects of combined drugs on the cardiac and splenic response in horses and provide information on the NSE of the large colon for clinical application.

Materials and Methods:

Six healthy Thai native crossbred horses were enrolled in this study. Horses received two protocols with a withdrawal period of 14 days: Group 1 received xylazine (0.5 mg/kg IV) and adrenaline (1 mcg/kg IV), and Group 2 received xylazine (0.5 mg/kg IV) and adrenaline (3 mcg/kg IV). Heart rate (HR), HR variability (HRV), heart dimensions, and the splenic response of six horses were measured before the sedation, 30 and 60 min later, and 65, 70, 75, 80, 90, and 100 min after adrenaline administration. Doppler was used to obtain systolic blood pressure.

Results:

The HRV low-frequency and high-frequency power ratios decreased after using xylazine. Hypertension was observed after adrenaline administration. In this study, there were only minimal differences in the HR and respiratory rate between groups. However, overall cardiac and splenic parameters were statistically higher in Group 2.

Conclusion:

This study suggested that xylazine and three micrograms of adrenaline preserved the cardiac autonomic activity balance and were safe to use non-surgical applicability in horses.

Comparison of liberal and goal-directed fluid therapy after small intestinal surgery for strangulating lesions in horses

BACKGROUND

There are few guidelines for the appropriate mode of fluid administration during and after colic surgery, and is challenging to reach the right balance while avoiding overhydration. This study aimed to compare goal-directed fluid therapy (GDFT) and 'liberal' fluid regimens (LFRs) in horses undergoing small intestinal surgery.

METHODS

Eighteen horses subjected to small intestinal surgery were matched according to the surgical lesion, type of anastomosis, length of resection, and duration of clinical signs. Horses in the LFR group were administered intravenous (IV) fluids for at least 24 h. In the GDFT group, IV fluids were administered only when considered necessary based on clinical parameters. Postoperative reflux (POR), packed cell volume, total protein, heart rate, venous lactate level, complications, and long-term survival rates were compared.

RESULTS

Three horses in the LFR and one in the GDFT group developed POR. Horses in the GDFT group had a shorter time interval to first oral water intake and shorter hospitalisation time. Postoperative complication rates and survival were not different between groups.

CONCLUSION

Further studies are necessary to set guidelines for the evaluation of hydration status and to plan postoperative fluid administration; however, GDFT may be a valid alternative to liberal fluid therapy after colic surgery.

Comparative evaluation of clinical findings and prognostic outcome parameters in hospitalized, critically ill neonatal foals and crias

OBJECTIVE

Species-related differences in the prevalence, manifestation, and outcome of neonatal illness may impact management practices of neonatal intensive care. The study aimed to elucidate similarities between disease manifestations and mortality risks of critically ill (CI) neonatal crias and foals admitted to the same referral center.

DESIGN

A comparative, retrospective cohort evaluation of two species (camelid and equine).

SETTING

The study was conducted in a University hospital.

ANIMALS

Two hundred and forty-six CI neonatal crias (January 1999 to May 2016) and 356 neonatal foals (February 2001 to May 2016) under 4-week-old were admitted to a university hospital.

INTERVENTION

All data are presented descriptively and compared between groups using univariate and multivariate analyses.

MEASUREMENTS AND MAIN RESULTS

Female crias (142/246, 57.7%) were significantly overrepresented in comparison to fillies (132/352, 37.5%). Congenital defects and transfer failure of passive immunity were more often observed in neonatal crias, while colic, diarrhea, patent urachus, septic arthritis, and omphalitis were significantly more common in CI foals. Overall survival to discharge (excluding fatal congenital defects) was comparable between crias (174/224; 77.8%) and foals (287/347, 82.1%), while crias (26/48; 54.2%) were more likely than foals (21/60; 35%) to die naturally than undergo euthanasia. Lower respiratory disease and indications for oxygen or IV glucose support increased mortality in the multivariate outcome models of both species. Species-specific adaptations of pediatric diagnostic criteria for sepsis were significantly associated with mortality in the multivariate analysis of patients with complete hematological datasets. However, the diagnosis of systemic inflammatory response syndrome (SIRS) did not retain statistical significance as an independent outcome predictor.

CONCLUSIONS

Lower respiratory disease and oxygen or glucose dysregulation increased mortality irrespective of species. However, despite species-specific differences in disease prevalence, the success of intensive care management was comparable.

Evaluation of Blood Glucose and Lactate Concentrations in Mule and Equine Foals

Information about mule physiology is scarce. Glucose and lactate serve as prognostic tools in neonates; thus, real-time evaluations would be beneficial. Our main objective was to measure glucose and lactate concentrations from healthy mule and equine foals from birth to 720 hours. Glucose and lactate concentrations were evaluated with a benchtop Randox Daytona analyzer (LAB) using plasma and with an Accutrend Plus system (ACP) using whole blood. Data were analyzed using PROC MIXED (P < .05), intraclass coefficient correlation and Bland-Altman analysis. Glucose and lactate concentrations from mule and equine foals were different when evaluated with LAB, but there was no difference when evaluated with ACP. Glucose pattern of variation, evaluated with both analyzers for mule and equine foals, had an increase, with subsequent decrease, whereas lactate pattern of variation had initial higher values with subsequent decrease. Intraclass coefficient correlation for glucose was low and moderate for lactate. Results of glucose and lactate with ACP from our experimental neonates were not highly correlated with LAB. However, the ACP had the same pattern of variation for glucose and lactate, thus can still be used clinically for immediate evaluations if the technique is standardized with the specific samples that will be used.

Variations in haematological and biochemical parameters in healthy ponies

Background

Breed specific reference ranges for selected blood parameters are recommended for proper interpretation of blood tests, but there are only few reports dealing with ponies. The purpose of this study was to investigate if blood parameters differ among ponies’ classes and to check if general normal values for equine species are applicable to ponies.

Results

All, except total protein concentration, biochemical parameter significantly (p < 0.05) differed among ponies’ classes. The most pronounced difference was noted in blood lactate concentrations, higher (p < 0.001) in the smallest ponies (class A). In all groups of ponies muscle enzymes (aspartate aminotransferase and creatine kinase) and urea were high when compared to normal values for equine species, but triglycerides and creatinine were low. Blood lactate concentration was high in comparison with normal values for horses only in class A ponies’.

Conclusions

In healthy ponies, blood lactate concentration significantly differs between height classes. Normal values for equine species should not be directly applied to interpret the lactate, triglycerides, aspartate aminotransferase and creatine kinase values in ponies.

Oxidative state in equine neonates: Anti- and pro-oxidants

BACKGROUND

In newborns, exposure to the extrauterine environment with high oxygen tension and sudden pulmonary adaptation leads to an increase in reactive oxygen species (ROS). ROS have several physiological roles, which are essential for neonatal development, however, when unbalanced, these highly unstable molecules can cause cellular destabilisation, compromising vital processes.

OBJECTIVES

To characterise the oxidative status in healthy equine neonates, evaluating an indicator of lipid peroxidation and both enzymatic and nonenzymatic antioxidant systems, during the first week of life.

STUDY DESIGN

Experimental cohort.

METHODS

Twenty-four foals were evaluated, with blood collections performed at 5 minutes, 12, 72 and 168 hours after birth. The degree of lipid peroxidation was quantified using Thiobarbituric Acid Reactive Substances (TBARS). Superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic activities, and total, conjugated and unconjugated serum bilirubin levels were also analysed. Comparisons were performed using ANOVA followed by a Tukey's test. Additionally, dependent variables were also evaluated with Pearson's correlation tests.

RESULTS

Higher GPx activity was observed at 12 and 72 hours when compared to 5 minutes. An increase in TBARS levels was found at 5 minutes after birth, followed by a decrease at 72 hours and stabilisation through subsequent moments until 168 hours after birth. No differences were observed in SOD activity when comparing the four time points. Bilirubin concentrations were lower at 5 minutes after birth and total and unconjugated bilirubin increased at 12 hours and decreased between 72 and 168 hours after birth.

CONCLUSIONS

Lipid peroxidation at birth was high, suggesting an increase in ROS levels relating to physiological events in neonatal adaptation. Antioxidant systems, involving unconjugated bilirubin and GPx, were activated and these biomolecules act concomitantly to reduce ROS levels, thus maintaining oxidative homeostasis. Overall, our results suggest a pro-oxidant balance during the first 168 hours after birth in equine neonates.

Clinical Pathology in the Foal

The dynamic physiologic changes and unique diet during the neonatal period contribute to key differences in clinicopathologic test results of healthy foals relative to healthy adult horses. When reporting results, most diagnostic laboratories only provide reference intervals for mature horses. Thus, failure to recognize the unique differences that occur in foals relative to adult horses can lead to erroneous interpretation of neonatal clinical pathologic values. Thus, the main objective of this article was to review distinct features of common clinicopathologic tests in foals, relative to mature horses.

Effect of Intravenously Administered Crystalloid Solutions on Acid-Base Balance in Domestic Animals

Intravenous fluid therapy can alter plasma acid-base balance. The Stewart approach to acid-base balance is uniquely suited to identify and quantify the effects of the cationic and anionic constituents of crystalloid solutions on plasma pH. The plasma strong ion difference (SID) and weak acid concentrations are similar to those of the administered fluid, more so at higher administration rates and with larger volumes. A crystalloid's in vivo effects on plasma pH are described by 3 general rules: SID > [HCO3-] increases plasma pH (alkalosis); SID < [HCO3-] decreases plasma pH (alkalosis); and SID = [HCO3-] yields no change in plasma pH. The in vitro pH of commercially prepared crystalloid solutions has little to no effect on plasma pH because of their low titratable acidity. Appreciation of IV fluid composition and an understanding of basic physicochemical principles provide therapeutically valuable insights about how and why fluid therapy can produce and correct alterations of plasma acid-base equilibrium. The ideal balanced crystalloid should (1) contain species-specific concentrations of key electrolytes (Na+ , Cl- , K+ , Ca++ , Mg++ ), particularly Na+ and Cl- ; (2) maintain or normalize acid-base balance (provide an appropriate SID); and (3) be isosmotic and isotonic (not induce inappropriate fluid shifts) with normal plasma.

Comparison of jugular and transverse facial venous sinus blood analytes in healthy and critically ill adult horses

OBJECTIVE

To compare blood gas, electrolyte, and metabolic analysis results between blood obtained by jugular and transverse facial venous sinus (TFVS) venipuncture in healthy adult horses and sick adult horses presented for emergency evaluation.

DESIGN

Prospective, experimental study, from June 2012 to October 2013.

SETTING

Large animal university teaching hospital.

ANIMALS

Ten healthy adult University-owned horses and 48 client-owned adult horses (≥2 years old) presenting to the large animal hospital emergency service for medical or surgical evaluation of systemic illness.

INTERVENTIONS

Venipunctures (jugular vein [JV] and TFVS) were performed using preheparinized syringes and obtained prior to institution of medical therapy. Samples were analyzed in random order within a 10-minute interval using a point-of-care blood gas analyzer (NOVA Critical Care Xpress) that also reports electrolyte and metabolite results. Comparisons between venipuncture sites were analyzed using the Student's paired t-test for normally distributed data and the Wilcoxon paired test for nonnormally distributed data. Bland-Altman analysis was used to assess agreement between venipuncture sites.

MEASUREMENTS AND MAIN RESULTS

There were no statistically significant differences found between variables for JV and TFVS in healthy horses. In sick horses, JV measurements were greater than TFVS for ionized calcium (P = 0.002) and glucose (P = 0.001), and less than TFVS for hematocrit (P = 0.015). Bland-Altman plots demonstrated small biases but overall agreement between sites.

CONCLUSIONS

The TFVS can be used interchangeably with JV for venous blood gas analysis in healthy horses. In sick horses, identified differences were small and likely not clinically important. The reliability of this point-of-care blood gas analyzer for measurement of hematocrit remains to be determined.

Effect of Dexamethasone on Resting Blood Lactate Concentrations in Horses

Background

Blood lactate concentration is a marker of tissue perfusion and helps guide therapeutic interventions in critically ill horses. In both humans and dogs, administration of corticosteroids can increase blood lactate concentration, leading to type B hyperlactatemia. This effect could be a consequence of the impact of corticosteroids on glucose metabolism.

Objectives

To investigate the effects of daily IM dexamethasone administration on blood lactate and glucose concentrations in horses.

Animals

Nine healthy adult horses.

Methods

A randomized, blinded, controlled, cross‐over study design was used. Horses were randomly assigned to 1 of 2 groups, either receiving 0.05 mg/kg of dexamethasone IM or an equivalent volume of saline, daily for 7 days. Blood was collected to determine lactate and glucose concentrations at baseline, 2 hours after the daily injections and 24 hours after the last injection.

Results

Dexamethasone treatment had a statistically significant effect on lactate (P = .006) and glucose (P = .033) concentrations. The least squares mean lactate concentration was 0.93 mmol/L (95% CI: 0.87–0.99) in the dexamethasone group compared to 0.71 mmol/L (95% CI: 0.70–0.73) for the saline group. A positive relationship between blood lactate and glucose concentrations was identified, with a 0.07 mmol/L (95% CI: 0.05–0.09) increase in lactate concentration per unit increase in glucose (P < .0001) concentration.

Conclusions and Clinical Importance

Dexamethasone induces statistically significant increases in blood lactate and glucose concentrations in healthy horses. Awareness of the potential for corticosteroids to induce type B hyperlactatemia might be important in the management of critically ill horses receiving dexamethasone.

The Effect of Inadequate Presample Blood Volume Withdrawal from Intravenous Catheter and Extension Sets on Measured Circulating L-Blood Lactate Concentration in Horses Receiving Lactated Ringer's Solution

Background

Circulating l‐lactate concentration is commonly measured in hospitalized horses by sampling from indwelling intravenous (IV) catheters. However, there are no published evidence‐based recommendations to prevent contamination by lactated Ringer's solution (LRS).

Hypothesis

Withdrawing 10 mL of blood from the LRS‐containing extension set connected to the IV catheter before obtaining the sample for analysis should be adequate to obtain accurate measurement of blood lactate concentration (BLC).

Animals

Thirty‐three adult hospitalized horses receiving constant rate infusion of LRS.

Methods

Immediately after disconnecting the LRS, 5 sequential 5 mL blood samples were obtained by aspiration from an extension set connected to an indwelling IV catheter, followed by 3 samples collected by direct venipuncture of the contralateral jugular vein. Samples were analyzed with 1 portable blood lactate analyzer. A linear mixed model was used to examine differences in lactate concentrations among samples collected from the catheter and by direct venipuncture.

Results

After considering differences in age, breed, sex, and reason for hospitalization, BLCs were higher (P < .001) in the first and second 5 mL samples collected through the extension set/catheter than in all other extension set/catheter samples or the direct venipuncture samples. The largest difference observed between the third and subsequent catheter or venipuncture samples was 0.34 mmol/L with an upper 95% CI of 1.12 mmol/L.

Conclusions and Clinical Importance

Withdrawing 15 mL of blood from a LRS‐containing extension set connected to an IV catheter (5.9 mL total volume capacity) before obtaining the sample for blood lactate analysis is suggested to optimize accuracy of BLC measurements.