Acid-base imbalances and the association of blood-gas variables, electrolytes, and biochemical analytes with outcome in hospitalized calves undergoing abdominal surgery

BACKGROUND

Surgical abdominal emergencies in calves are associated with a guarded prognosis and have the potential for complex metabolic derangements including acid-base imbalances.

OBJECTIVES

To perform a comprehensive analysis of acid-base status and to assess the prognostic relevance of preoperative clinicopathologic variables in calves undergoing abdominal surgery.

ANIMALS

Hospital-based study samples of 535 (dataset 1; DS1) and 83 calves (dataset 2; DS2).

METHODS

Retrospective (DS1) and prospective (DS2) case series.

RESULTS

In DS1, acidemia (pH <7.33) was present in 49.9%, whereas alkalemia (pH >7.37) was present in 30.7% of calves. Plasma L-lactate, chloride, and serum inorganic phosphorus concentration accounted for 51.9%, 11.6% and 9.4% of the variation of venous blood pH, respectively. Classification tree analysis indicated that a negative outcome (death or euthanasia during hospitalization) was associated with venous pO₂  ≤33.6 mm Hg, anion gap >18.3 and >22.9 mEq/L, serum albumin concentration ≤36.5 and ≤29.4 g/L, serum urea concentration >4.4 mmol/L, and plasma ionized calcium concentration ≤1.26 mmol/L. The area under the receiver operating characteristic curve of this model was 0.85 (95% CI: 0.82-0.89, P < .001) and the resulting sensitivity and specificity for the prediction of nonsurvival at the optimal probability cut-point of 0.5 was 89.8% and 65.7%, respectively. In DS2 the model had a similar sensitivity and specificity of 90.5% and 70%, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinicopathologic imbalances and associated changes of acid-base status are common in calves with surgical abdominal emergencies and have clinical utility for the prediction of a negative postoperative outcome.

Macrophages in dermal disease progression of phospholipase D4-deficient Fleckvieh calves

A new gene defect in Fleckvieh calves leads to a syndrome with partial phenotype overlap with bovine hereditary zinc deficiency. A mutation in a gene encoding phospholipase D4 (PLD4), an endosomal exonuclease, causes the disorder. In mice, PLD4 activity indirectly regulates the Toll-like receptor 9 (TLR9) pathway via degradation of microbial DNA. PLD4 absence thus results in visceral macrophage activation comparable to human macrophage activation syndrome. In this study, disease progression and the role of macrophages in affected calves were monitored clinically, clinicopathologically, and histologically over time. Breeding data identified 73 risk matings of heterozygous carriers resulting in 54 potentially PLD4-deficient calves born on farms. PLD4 status was examined via 5'-exonuclease assay, detecting 6 calves carrying the defect. These were purchased and monitored daily until final necropsy. The calves developed progressive skin lesions starting with small scaling areas terminating in severe crusting dermatitis, especially in areas with mechanical exposure. Histological and immunohistochemical analyses indicated that macrophages with cytoplasmic vacuolation increased considerably in skin sections obtained weekly during the disease course. Macrophage increase correlated with increased dermal lesion severity. Macrophage activation was confirmed by prominent phagocytic activity in the superficial dermis using electron microscopy. Dermal mRNA abundance of CCL2 and CCL3 measured by quantitative polymerase chain reaction verified macrophage activation. Further increase in mRNA of downstream molecule MyD88 and cytokine IL12b connected bovine PLD4 deficiency to increased TLR9 pathway activation. In contrast to human macrophage activation syndrome, the main feature of bovine PLD4 deficiency was local disease in organs with contact to microbial DNA (skin, intestine, lungs).

Intravenous and Oral Fluid Therapy in Neonatal Calves With Diarrhea or Sepsis and in Adult Cattle

Optimal fluid therapy protocols in neonatal calves and adult cattle are based on consideration of signalment, history, and physical examination findings, and individually tailored whenever laboratory analysis is available. Measurement of the magnitude of eye recession, duration of skin tenting in the lateral neck region, and urine specific gravity by refractometry provide the best estimates of hydration status in calves and cattle. Intravenous and oral electrolyte solutions (OES) are frequently administered to critically ill calves and adult cattle. Application of physicochemical principles indicates that 0.9% NaCl, Ringer's solution, and 5% dextrose are equally acidifying, lactated Ringer's and acetated Ringer's solution are neutral to mildly acidifying, and 1.3-1.4% sodium bicarbonate solutions are strongly alkalinizing in cattle. Four different crystalloid solutions are recommended for intravenous fluid therapy in dehydrated or septic calves and dehydrated adult cattle: (1) lactated Ringer's solution and acetated Ringer's solution for dehydrated calves, although neither solution is optimized for administration to neonatal calves or adult cattle; (2) isotonic (1.3%) or hypertonic (5.0 or 8.4%) solutions of sodium bicarbonate for the treatment of calves with diarrhea and severe strong ion (metabolic) acidosis and hyponatremia, and adult cattle with acute ruminal acidosis; (3) Ringer's solution for the treatment of metabolic alkalosis in dehydrated adult cattle, particularly lactating dairy cattle; and (4) hypertonic NaCl solutions (7.2%) and an oral electrolyte solution or water load for the rapid resuscitation of dehydrated neonatal calves and adult cattle. Much progress has been made since the 1970's in identifying important attributes of an OES for diarrheic calves. Important components of an OES for neonatal calves are osmolality, sodium concentration, the effective SID that reflects the concentration of alkalinizing agents, and the energy content. The last three factors are intimately tied to the OES osmolality and the abomasal emptying rate, and therefore the rate of sodium delivery to the small intestine and ultimately the rate of resuscitation. An important need in fluid and electrolyte therapy for adult ruminants is formulation of a practical, effective, and inexpensive OES.

Dependence of the apparent bicarbonate space on initial plasma bicarbonate concentration and carbon dioxide tension in neonatal calves with diarrhea, acidemia, and metabolic acidosis

BACKGROUND

Marked strong ion (metabolic) acidosis in neonatal diarrheic calves usually is corrected by IV administration of NaHCO₃ . The distribution space for IV-administered bicarbonate, called the apparent bicarbonate space (ABS), appears to depend on initial plasma bicarbonate concentration (cHCO₃ ) and varies considerably in calves.

OBJECTIVE

To determine whether ABS was associated with initial plasma cHCO₃ and other acid-base variables.

ANIMALS

Twenty-five neonatal diarrheic calves with acidemia and metabolic acidosis.

METHODS

Prospective observational study using a convenience sample. Calves received NaHCO₃ (10 mmol/kg) and glucose (1.4 mmol/kg) IV in a crystalloid solution at 25 mL/kg over 60 minutes. The ABS (L/kg) was calculated at 4 time points over 2 hours after the end of the infusion. The relationship between ABS and initial acid-base variables was characterized using nonlinear, linear, and stepwise regression.

RESULTS

The median value for ABS calculated from the initial plasma cHCO₃ increased from 0.53 L/kg (range, 0.40-0.79) at the end of IV infusion to 0.96 L/kg (range, 0.54-1.23) 120 minutes later. Data obtained at the end of infusion provided the best fit to initial plasma cHCO₃ and jugular venous blood Pco₂ , such that: ABS = 0.41 + 1.06/cHCO₃ and ABS = 0.87-0.0082 × Pco₂ .

CONCLUSIONS AND CLINICAL IMPORTANCE

The observed median value for ABS of 0.53 L/kg in our study was similar to the empirically used value of 0.6. However, ABS values varied widely and were increased in calves with severe metabolic acidosis. We therefore recommend calculating ABS using the initial plasma cHCO₃ or venous blood Pco₂ , if respective measurements are available.

Prognostic utility of pre- and postoperative plasma l-lactate measurements in hospitalized cows with acute abdominal emergencies

The aim of the present analyses was to compare the prognostic value of pre- and postoperative l-lactate measurements in hospitalized cows requiring surgical intervention for an acute abdominal emergency, such as gastrointestinal ileus or peritonitis. For this purpose, we analyzed data from retro- and prospective case series, consisting of 754 and 98 cows, respectively. Plasma l-lactate concentrations (L-LAC) were determined upon admission to the hospital (both study populations), immediately before initiation of surgical intervention (prospective study population), and 6, 12, 24, 48, and 72 h later (prospective study population). The outcome of cows was evaluated until hospital discharge (both study populations) and 3 mo after discharge by a phone call to the farmer (prospective study population). A negative outcome was defined as death or euthanasia during hospitalization, or if discharged animals had an unsatisfied owner or were culled for medical reasons that were directly related to the initial abdominal emergency. For the retrospective study population, the overall survival rate until hospital discharge was 66%. Cows with a negative outcome (median: 6.81 mmol/L) had significantly higher L-LAC than cows with a positive outcome (3.66 mmol/L) of therapy. At the individual diagnosis level, L-LAC was associated with mortality in cows with a diagnosis of abomasal volvulus, local peritonitis, hemorrhagic bowel syndrome, and jejunal volvulus. Considering the whole study population, the area under the receiver operating characteristic curve was 0.66. For the prospective study population, the proportion of cows with a positive outcome was 65% until hospital discharge and 61% after the 3-mo observation period. At all sampling times, before and during the first 12 h after surgical intervention, cows with a negative outcome had significantly higher L-LAC than cows with a positive outcome. The largest area under the receiver operating characteristic curve for L-LAC was observed at 6 h (0.89). A cut-point of 1.77 mmol/L was identified, which had a sensitivity and specificity for predicting a negative outcome until hospital discharge of 88.9 and 73.4%, respectively. The present analyses confirmed previous findings in calves and show that persistent hyper-l-lactatemia during the early postoperative period is a more reliable indicator for a negative outcome than hyper-l-lactatemia before initiation of surgical intervention.

Prognostic relevance of pre- and postoperative plasma l-lactate measurements in calves with acute abdominal emergencies

In both human and veterinary medicine, l-lactate is a well-established prognostic biomarker of disease severity and mortality and has also attracted increasing attention in bovine medicine due to the availability and validation of cheap and portable l-lactate analyzers. The aim of the present study was to evaluate the prognostic accuracy of plasma L-lactate measurements in calves with acute abdominal emergencies before and during the initial therapeutic period after surgical intervention. A prospective observational study was carried out involving 83 hospitalized calves up to an age of 7 mo, which required surgical intervention for reasons of an acute abdominal emergency such as gastrointestinal ileus or peritonitis. Plasma l-lactate (L-LAC) concentrations were determined immediately before initiation of surgery and 6, 12, 24, 48, and 72 h later. The outcome of calves was evaluated 3 mo after discharge by a phone call to the farmer, and a positive outcome was defined if the calf was still alive and the owner was satisfied with the animal's postsurgical progress. A total of 29% of calves were discharged from the hospital and the proportion of calves with a positive outcome after the 3-mo period was 24%. At all sampling times during the first 48 h after initiation of surgical intervention, calves with a negative outcome had significantly higher L-LAC than calves with a positive outcome. A binary logistic regression analysis indicated that the odds for a negative outcome during the 3-mo observation period increased by a factor of 1.23 [95% confidence interval (CI): 1.04-1.44] for every mmol/L increase of L-LAC before initiation of surgical intervention, but by a factor of 5.29 (95% CI: 1.69-16.6) and 5.92 (95% CI: 1.29-27.3) at 12 and 24 h, respectively. The largest area under the receiver operating characteristic curve for L-LAC was observed at 12 h (0.91; 95% CI: 0.83-0.99), and a cut-point of 2.75 mmol/L was identified that had a sensitivity and specificity for predicting a negative outcome of 68 and 100%, respectively. In conclusion, persistent hyper-l-lactatemia during the early postoperative period is a more reliable indicator for a negative outcome in calves with acute surgical abdominal emergencies than hyper-l-lactatemia before initiation of surgical intervention. Postoperative measurements of L-LAC are therefore a clinically useful tool to identify patients with an increased risk for a negative outcome at an early stage after surgical intervention was carried out.

Prognostic value of preoperative plasma l-lactate concentrations in calves with acute abdominal emergencies

Acute abdominal emergencies in calves due to abomasal disorders, gastrointestinal ileus, or peritonitis are characterized by a rapid disease progression and usually require immediate surgical intervention. Those conditions are associated with a guarded prognosis, and the aim of the present study was to assess the prognostic relevance of preoperatively measured plasma l-lactate concentrations (l-LAC) in a large study population of calves with a broad spectrum of acute abdominal emergencies. For the purpose of this study, the medical records of 587 calves admitted to a veterinary teaching hospital over a 10-yr period were analyzed retrospectively. Plasma l-LAC was measured as part of a routinely performed biochemistry panel before initiation of surgical intervention. Hyper-l-lactatemia (plasma l-LAC >2.2 mmol/L) was evident in 75% of calves, and the overall survival rate until hospital discharge was 31%. Calves with a negative outcome were younger (median: 3.4 vs. 6 wk) and had higher plasma l-LAC (median: 4.96 vs. 3.09 mmol/L) than calves with a positive outcome. At the individual diagnosis level, l-LAC was associated with mortality in calves with a diagnosis of mesenteric torsion, right-sided dilated abomasum, small intestinal volvulus, or paralytic ileus, but not in calves suffering from peritonitis, malformations, abomasal volvulus, bloat, or small intestinal intussusceptions. Considering the whole study population, the area under the receiver operating characteristic (ROC) curve for plasma l-LAC was 0.66 [95% confidence interval (CI): 0.61-0.70]. A classification tree analysis indicated that l-LAC >8.84 mmol/L and age categories of <3 wk and <1 wk were independent predictors of mortality. The area under the ROC curve of this model was 0.75 (95% CI: 0.71-0.79) and the resulting sensitivity and specificity for the prediction of nonsurvival at the optimal probability cut-point of 0.62 were 67.7 and 76.6%, respectively. In conclusion, hyper-l-lactatemia is common in calves suffering from acute abdominal emergencies. Markedly increased plasma l-LAC is associated with an increased mortality risk, but it is not possible to reliably predict the outcome of affected calves based on a single, preoperative measurement. However, a clinically important finding of this study was that the ability to predict a negative outcome is improved when the age of the calf is considered in addition to plasma l-LAC.

Evaluation of the analytical performance of a portable ion-selective electrode meter for measuring whole-blood, plasma, milk, abomasal-fluid, and urine sodium concentrations in cattle

A portable ion-selective electrode (ISE) meter (LAQUAtwin B-722; Horiba Instruments Inc., Irvine, CA) is available for measuring the sodium ion concentration ([Na]) in biological fluids. The objective of this study was to characterize the analytical performance of the ISE meter in measuring [Na] in whole-blood, plasma, milk, abomasal fluid, and urine samples from cattle. Method comparison studies were performed using whole-blood and plasma samples from 106 sick calves and 11 sick cows admitted to a veterinary teaching hospital, 80 milk and 206 urine samples from 16 lactating Holstein-Friesian cows with experimentally induced free water, electrolyte, and acid-base imbalances, and 67 abomasal fluid samples from 7 healthy male Holstein-Friesian calves fed fresh milk with or without an oral electrolyte solution. Deming regression and Bland-Altman plots were used to determine the accuracy of the meter against reference methods. The meter used in direct mode on undiluted samples measured whole-blood [Na] 9.7 mmol/L (7.3%) lower than a direct ISE reference method and plasma [Na] 16.7 mmol/L (12.7%) lower than an indirect ISE reference method. The meter run in direct mode measured milk [Na] 3.1 mmol/L lower and abomasal fluid [Na] 9.0% lower than indirect ISE reference methods. The meter run in indirect mode on diluted samples accurately measured urine [Na] compared with an indirect ISE reference method. We conclude that, after adjustment for the bias determined from Bland-Altman plots, the LAQUAtwin ISE meter provides a clinically useful and low-cost cow-side instrument for measuring [Na] in whole blood, plasma, milk, and abomasal fluid.

Effects of pH and the plasma or serum concentrations of total calcium, chloride, magnesium, l-lactate, and albumin on the plasma ionized calcium concentration in calves

Background

The plasma ionized calcium concentration (cCa²⁺) represents the biologically active form of calcium and is the preferred method for evaluating calcium status in animals. Different pH‐corrective equations have been developed for human plasma, but the validity of the equations for bovine plasma is unknown.

Hypothesis

We hypothesized that pH‐corrective equations for bovine plasma would be similar to those used for human plasma; cCa²⁺ was dependent on the plasma concentrations of total calcium (cTCa), chloride (cCl), L‐lactate (cLactate), and albumin (cAlbumin); and the in vitro and in vivo cCa²⁺‐pH relationships would differ.

Animals

Ten healthy calves (in vitro study), 1426 critically ill calves.

Methods

The in vitro plasma log₁₀(cCa²⁺)‐pH relationship was determined by CO₂ tonometry of 465 plasma samples. Plasma cCl was altered by equivolume dilution of plasma with 3 electrolyte solutions of different cCl. The in vivo plasma cCa²⁺‐pH relationship was investigated and validated using clinicopathologic data extracted from the medical records of 950 (model development) and 476 (model validation) critically ill calves.

Results

pH‐corrective equations for bovine plasma were similar to those used for human plasma. Plasma cCa²⁺ increased in vitro with increases in plasma cCl. Plasma cCa²⁺ in critically ill calves was associated with plasma cTCa, blood pH, plasma cCl, serum cMg, and cL‐lactate (R² = 0.69) but not plasma cAlbumin.

Conclusions and Clinical Importance

Calculation of cCa²⁺ from cTCa in calf plasma or serum requires adjustment for at least pH and cCl when 1 or both are outside the reference range.

Electrocardiographic findings in 130 hospitalized neonatal calves with diarrhea and associated potassium balance disorders

Background

Hyperkalemia in neonatal diarrheic calves can potentially result in serious cardiac conduction abnormalities and arrhythmias.

Objectives

To document electrocardiographic (ECG) findings and the sequence of ECG changes that are associated with increasing plasma potassium concentrations (cK⁺) in a large population of neonatal diarrheic calves.

Animals

One hundred and thirty neonatal diarrheic calves (age ≤21 days).

Methods

Prospective observational study involving calves admitted to a veterinary teaching hospital.

Results

Hyperkalemic calves (cK⁺: 5.8‐10.2, blood pH: 6.55‐7.47) had significantly (P < .05) longer QRS durations as well as deeper S wave, higher T wave, and higher ST segment amplitudes in lead II than calves, which had both venous blood pH and cK⁺ within the reference range. The first ECG changes in response to an increase in cK⁺ were an increase in voltages of P, Ta, S, and T wave amplitudes. Segmented linear regression indicated that P wave amplitude decreased when cK⁺ >6.5 mmol/L, S wave amplitude voltage decreased when cK⁺ >7.4 mmol/L, QRS duration increased when cK⁺ >7.8 mmol/L, J point amplitude increased when cK⁺ >7.9 mmol/L, and ST segment angle increased when cK⁺ >9.1 mmol/L. P wave amplitude was characterized by a second common break point at cK⁺ = 8.2 mmol/L, above which value the amplitude was 0.

Conclusions and Clinical Importance

Hyperkalemia in neonatal diarrheic calves is associated with serious cardiac conduction abnormalities. In addition to increased S and T wave amplitude voltages, alterations of P and Ta wave amplitudes are early signs of hyperkalemia, which is consistent with the known sensitivity of atrial myocytes to increased cK⁺.

Zinc Deficiency-Like Syndrome in Fleckvieh Calves: Clinical and Pathological Findings and Differentiation from Bovine Hereditary Zinc Deficiency

Background

Zinc deficiency‐like (ZDL) syndrome is an inherited defect of Fleckvieh calves, with striking similarity to bovine hereditary zinc deficiency (BHZD). However, the causative mutation in a phospholipase D4 encoding gene (PLD4) shows no connection to zinc metabolism.

Objectives

To describe clinical signs, laboratory variables, and pathological findings of ZDL syndrome and their utility to differentiate ZDL from BHZD and infectious diseases with similar phenotype.

Animals

Nine hospitalized calves with crusting dermatitis and confirmed mutation in PLD4 and medical records from 25 calves with crusting dermatitis or suspected zinc deficiency.

Methods

Prospective and retrospective case series.

Results

The 9 calves (age: 5–53 weeks) displayed a moderate to severe crusting dermatitis mainly on the head, ventrum, and joints. Respiratory and digestive tract inflammations were frequently observed. Zinc supplementation did not lead to remission of clinical signs in 4 calves. Laboratory variables revealed slight anemia in 8 calves, hypoalbuminemia in 6 calves, but reduced serum zinc concentrations in only 3 calves. Mucosal erosions/ulcerations were present in 7 calves and thymus atrophy or reduced thymic weights in 8 calves. Histologically, skin lesions were indistinguishable from BHZD. Retrospective analysis of medical records revealed the presence of this phenotype since 1988 and pedigree analysis revealed a common ancestor of several affected calves.

Conclusions and Clinical Importance

ZDL syndrome should be suspected in Fleckvieh calves with crusting dermatitis together with diarrhea or respiratory tract inflammations without response to oral zinc supplementation. Definite diagnosis requires molecular genetic confirmation of the PLD4 mutation.

Plasma potassium concentrations in neonatal diarrhoeic calves are correlated with serum aldosterone concentrations but not with insulin concentrations

Hyperkalaemia is a clinically relevant electrolyte imbalance in neonatal diarrhoeic calves which was previously associated with severe dehydration and acidaemia. The present study assessed the association of plasma potassium (cK) with serum aldosterone and insulin concentrations, since these hormones are involved in the regulation of potassium homeostasis. Serum aldosterone (r_s=0.62), but not insulin concentrations (r_s=0.22) were closely correlated to cK in 123 hospitalised neonatal diarrhoeic calves. Median values for serum aldosterone concentrations in 38 hyperkalaemic calves (cK>5.8mmol/L) were 3.2 and 15.3 times higher (P<0.001) than in 85 non-hyperkalaemic diarrhoeic calves and nine healthy control calves, respectively. Aldosterone, but not insulin secretion, appears to be highly stimulated in dehydrated diarrhoeic calves with hyperkalaemia, but hypovolaemia and a concomitant decrease in renal perfusion and urinary flow rate are likely to limit the efficacy of aldosterone-induced control mechanisms in these animals.

Effect of Intravenous Small-Volume Hypertonic Sodium Bicarbonate, Sodium Chloride, and Glucose Solutions in Decreasing Plasma Potassium Concentration in Hyperkalemic Neonatal Calves with Diarrhea

Background

Hyperkalemia is a frequently observed electrolyte imbalance in dehydrated neonatal diarrheic calves that can result in skeletal muscle weakness and life‐threatening cardiac conduction abnormalities and arrhythmias.

Hypothesis

Intravenous administration of a small‐volume hypertonic NaHCO₃ solution is clinically more effective in decreasing the plasma potassium concentration (cK) in hyperkalemic diarrheic calves than hypertonic NaCl or glucose solutions.

Animals

Twenty‐two neonatal diarrheic calves with cK >5.8 mmol/L.

Methods

Prospective randomized clinical trial. Calves randomly received either 8.4% NaHCO₃ (6.4 mL/kg BW; n = 7), 7.5% NaCl (5 mL/kg BW; n = 8), or 46.2% glucose (5 mL/kg BW; n = 7) IV over 5 minutes and were subsequently allowed to suckle 2 L of an electrolyte solution. Infusions with NaHCO₃ and NaCl provided an identical sodium load of 6.4 mmol/kg BW.

Results

Hypertonic NaHCO₃ infusions produced an immediate and sustained decrease in plasma cK. Hypertonic glucose infusions resulted in marked hyperglycemia and hyperinsulinemia, but cK remained unchanged for 20 minutes. Between 30 and 120 minutes after initiation of treatment, the most marked decrements in cK from baseline occurred in group NaHCO₃, which were significantly (P < .05) larger during this period of time than in calves in group NaCl, but not group glucose. After 120 minutes, the mean decrease in cK from baseline was −26 ± 10%, −9 ± 8%, and −22 ± 6% in groups NaHCO₃, NaCl, and glucose, respectively.

Conclusions/Clinical Importance

Small‐volume hypertonic NaHCO₃ infusions appear to have clinical advantages for the rapid resuscitation of hyperkalemic diarrheic calves, compared to hypertonic NaCl or glucose solutions.

Risk factors for the development of hypokalemia in neonatal diarrheic calves

Background

Neonatal diarrheic calves have a clear negative potassium balance because of intestinal losses and decreased milk intake but in the presence of acidemia, they usually show normokalemic or hyperkalemic plasma concentrations.

Objectives

To assess whether marked hypokalemia occurs in response to the correction of acidemia and dehydration and to identify factors that are associated with this condition.

Animals

Eighty‐three calves with a clinical diagnosis of neonatal diarrhea.

Methods

Prospective cohort study. Calves were treated according to a clinical protocol using an oral electrolyte solution and commercially available packages of 8.4% sodium bicarbonate, 0.9% saline and 40% dextrose infusion solutions.

Results

The proportion of hypokalemic calves after 24 hours of treatment (19.3%) was twice as great as it was on admission to the hospital. Plasma K⁺ after 24 hours of treatment was not significantly correlated to venous blood pH values at the same time but positively correlated to venous blood pH values on admission (r = 0.51, P < .001). Base excess on admission (Odds ratio [OR] = 0.81, 95% confidence interval [CI] = 0.70–0.94), duration of diarrhea (OR = 1.37, 95% CI = 1.05–1.80), milk intake during hospitalization (OR = 0.54, 95% CI = 0.37–0.79) and plasma sodium concentrations after 24 hours (OR = 1.12, 95% CI = 1.01–1.25) were identified to be independently associated (P < .05) with a hypokalemic state after 24 hours of treatment.

Conclusions and Clinical Importance

Findings of this study suggest that marked depletion of body potassium stores is evident in diarrheic calves that suffered from marked metabolic acidosis, have a low milk intake and a long history of diarrhea.

Quantitative physicochemical analysis of acid-base balance and clinical utility of anion gap and strong ion gap in 806 neonatal calves with diarrhea

BACKGROUND

Acid-base abnormalities in neonatal diarrheic calves can be assessed by using the Henderson-Hasselbalch equation or the simplified strong ion approach which use the anion gap (AG) or the strong ion gap (SIG) to quantify the concentration of unmeasured strong anions such as D-lactate.

HYPOTHESIS/OBJECTIVES

To determine and compare the clinical utility of AG and SIG in quantifying the unmeasured strong anion charge in neonatal diarrheic calves, and to examine the associations between biochemical findings and acid-base variables by using the simplified strong ion approach. We hypothesized that the SIG provides a more accurate prediction of unmeasured strong anions than the AG.

ANIMALS

Eight hundred and six neonatal diarrheic calves admitted to a veterinary teaching hospital.

METHODS

Retrospective study utilizing clinicopathologic findings extracted from medical records.

RESULTS

Hyperphosphatemia was an important predictor of venous blood pH. Serum inorganic phosphorus and plasma D-lactate concentrations accounted for 58% of the variation in venous blood pH and 77% of the variation in AG and SIG. Plasma D- and total lactate concentrations were slightly better correlated with SIG (rs = -0.69; -0.78) than to AG (rs = 0.63; 0.74).

CONCLUSIONS AND CLINICAL IMPORTANCE

Strong ion gap is slightly better at quantifying the unmeasured strong anion concentration in neonatal diarrheic calves than AG. Phosphorus concentrations should be included as part of the calculation of Atot when applying the simplified strong ion approach to acid-base balance to critically ill animals with hyperphosphatemia.

Effects of alkalinization and rehydration on plasma potassium concentrations in neonatal calves with diarrhea

Background

Increased plasma potassium concentrations (K⁺) in neonatal calves with diarrhea are associated with acidemia and severe clinical dehydration and are therefore usually corrected by intravenous administration of fluids containing sodium bicarbonate.

Objectives

To identify clinical and laboratory variables that are associated with changes of plasma K⁺ during the course of treatment and to document the plasma potassium‐lowering effect of hypertonic (8.4%) sodium bicarbonate solutions.

Animals

Seventy‐one neonatal diarrheic calves.

Methods

Prospective cohort study. Calves were treated according to a clinical protocol using an oral electrolyte solution and commercially available packages of 8.4% sodium bicarbonate (250–750 mmol), 0.9% saline (5–10 L), and 40% dextrose (0.5 L) infusion solutions.

Results

Infusions with 8.4% sodium bicarbonate solutions in an amount of 250–750 mmol had an immediate and sustained plasma potassium‐lowering effect. One hour after the end of such infusions or the start of a sodium bicarbonate containing constant drip infusion, changes of plasma K⁺ were most closely correlated to changes of venous blood pH, plasma sodium concentrations and plasma volume (r = −0.73, −0.57, −0.53; P < .001). Changes of plasma K⁺ during the subsequent 23 hours were associated with changes of venous blood pH, clinical hydration status (enophthalmos) and serum creatinine concentrations (r = −0.71, 0.63, 0.62; P < .001).

Conclusions and Clinical Importance

This study emphasizes the importance of alkalinization and the correction of dehydration in the treatment of hyperkalemia in neonatal calves with diarrhea.

Hyperkalemia in neonatal diarrheic calves depends on the degree of dehydration and the cause of the metabolic acidosis but does not require the presence of acidemia

Hyperkalemia is a clinically important electrolyte imbalance in neonatal diarrheic calves that has previously been associated with skeletal muscle weakness and life-threatening cardiac arrhythmias. The aim of the present retrospective analysis was to identify risk factors for hyperkalemia in a convenience sample of 832 calves (≤ 21 d of age) with a clinical diagnosis of diarrhea admitted to a veterinary teaching hospital. Plasma potassium concentrations were most closely associated with parameters of dehydration and renal function such as serum creatinine [Spearman correlation (rs) = 0.61], urea (rs = 0.51), and inorganic phosphorus concentrations (rs = 0.64). Plasma potassium concentrations were weakly associated with venous blood pH (rs = -0.21). Although venous blood pH was not predictive in a multivariate linear regression analysis, the odds of having hyperkalemia (>5.8 mmol/L) in acidemic calves was found to be 8.6 times as high as in nonacidemic calves [95% confidence interval (CI): 4.8-15.4]. However, the presence of hyperkalemia depended on the nature of an existing acidosis, and the odds for the presence of hyperkalemia in acidemic calves with hyper-D-lactatemia (>3.96 mmol/L) were only 0.15 times as high as in acidemic calves with normal D-lactate concentrations (95% CI, 0.11-0.22). Acidemia in hyperkalemic diarrheic calves was associated with hyponatremia and increased concentrations of inorganic phosphorus, L-lactate, and unidentified strong anions that presumably included uremic anions such as sulfate. We conclude that hyper-D-lactatemia in neonatal diarrheic calves is not usually associated with elevated plasma potassium concentrations. Application of the simplified strong ion acid-base model indicated that dehydration is an important contributor to the pathogenesis of hyperkalemia and acidemia in neonatal calves with diarrhea.

Construction and validation of a decision tree for treating metabolic acidosis in calves with neonatal diarrhea

BACKGROUND

The aim of the present prospective study was to investigate whether a decision tree based on basic clinical signs could be used to determine the treatment of metabolic acidosis in calves successfully without expensive laboratory equipment. A total of 121 calves with a diagnosis of neonatal diarrhea admitted to a veterinary teaching hospital were included in the study. The dosages of sodium bicarbonate administered followed simple guidelines based on the results of a previous retrospective analysis. Calves that were neither dehydrated nor assumed to be acidemic received an oral electrolyte solution. In cases in which intravenous correction of acidosis and/or dehydration was deemed necessary, the provided amount of sodium bicarbonate ranged from 250 to 750 mmol (depending on alterations in posture) and infusion volumes from 1 to 6.25 liters (depending on the degree of dehydration). Individual body weights of calves were disregarded. During the 24 hour study period the investigator was blinded to all laboratory findings.

RESULTS

After being lifted, many calves were able to stand despite base excess levels below -20 mmol/l. Especially in those calves, metabolic acidosis was undercorrected with the provided amount of 500 mmol sodium bicarbonate, which was intended for calves standing insecurely. In 13 calves metabolic acidosis was not treated successfully as defined by an expected treatment failure or a measured base excess value below -5 mmol/l. By contrast, 24 hours after the initiation of therapy, a metabolic alkalosis was present in 55 calves (base excess levels above +5 mmol/l). However, the clinical status was not affected significantly by the metabolic alkalosis.

CONCLUSIONS

Assuming re-evaluation of the calf after 24 hours, the tested decision tree can be recommended for the use in field practice with minor modifications. Calves that stand insecurely and are not able to correct their position if pushed require higher doses of sodium bicarbonate, if there is clinical evidence of a marked D-lactic acidosis. In those calves, determining the degree of loss of the palpebral reflex was identified as a useful decision criterion to provide an additional amount of 250 mmol sodium bicarbonate. This work demonstrates the clinical relevance of the discovery that D-lactate is responsible for most of the clinical signs expressed in neonatal diarrheic calves suffering from metabolic acidosis.

Metabolic acidosis in neonatal calf diarrhea-clinical findings and theoretical assessment of a simple treatment protocol

BACKGROUND

Clinical assessment of metabolic acidosis in calves with neonatal diarrhea can be difficult because increased blood concentrations of d-lactate and not acidemia per se are responsible for most of the clinical signs exhibited by these animals.

OBJECTIVES

To describe the correlation between clinical and laboratory findings and d-lactate concentrations. Furthermore, the theoretical outcome of a simplified treatment protocol based on posture/ability to stand and degree of dehydration was evaluated.

ANIMALS

A total of 121 calves with diagnosis of neonatal diarrhea admitted to a veterinary teaching hospital during an 8-month study period.

METHODS

Prospective blinded cohort study. Physical examinations were carried out following a standardized protocol. Theoretical outcome of treatment was calculated.

RESULTS

Type and degree of metabolic acidosis were age dependent. The clinical parameters posture, behavior, and palpebral reflex were closely correlated to base excess (r = 0.74, 0.78, 0.68; P < .001) and d-lactate concentrations (r = 0.59, 0.59, 0.71; P < .001), respectively. Thus, determining the degree of loss of the palpebral reflex was identified as the best clinical tool for diagnosing increase in serum d-lactate concentrations. Theoretical outcome of treatment revealed that the tested dosages of sodium bicarbonate are more likely to overdose than to underdose calves with diarrhea and metabolic acidosis.

CONCLUSIONS AND CLINICAL IMPORTANCE

The degree of metabolic acidosis in diarrheic calves can be predicted based on clinical findings. The assessed protocol provides a useful tool to determine bicarbonate requirements, but a revision is necessary for calves with ability to stand and marked metabolic acidosis.