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Piotr Slawuta, Agnieszka Noszczyk-Nowak Agnieszka, Jozef Nicpon, Agnieszka Kurosad ©
Department of Internal Diseases with Clinic for Horses, Dogs and Cats, Faculty of Veterinary Medicine, University of Environmental and Life Sciences, pl. Grunwaldzki
47, 50-366 Wroclaw, Poland
USEFULNESS OF ANION GAP IN EARLY DIAGNOSTICS OF REASONS FOR ARRHYTHMIAS AND ACID-BASE EQUILIBRIUM DISTURBANCES
IN BOXERS
Key words: anion gap, dogs , boxers
Supported by Grant-in-Aid for Scientific Research from the Polish Ministry of Scientific Research and High Education in the years 2008-2011 as a research project N N308 187735
Introduction.
Acid-base equilibrium ( ABE ) disturbances, similarly to ions concentration in the blood serum, particularly hyponatremia, hypocalcemia, hypomagnesemia and hypochloremia, may affect the ECG curve parameters ( 5,6,7,10,11 ). Boxers are the breed predisposed to ventricular arrhythmias ( 3,13 ). Premature ventricular extrasystoles ( EV ) constitute one of the first signs of dilated cardiomyopathy of the Boxer type ( 13 ). EV of a short coupling interval for sinus beat may initiate ventricular tachycardia or ventricular fibrillation in R on T mechanism, which may become a cause of sudden cardiac death. That is why it is so important in this breed to detect the heart arrhythmias as well as their extra heart causes as early as possible and to refer the dogs to specialist examinations, i.e. electrocardiographic, echocardiographic and X-ray examinations. The notion of the anion gap (AG) is closely connected with acid-base equilibrium. Concentrations of cations and anions in the blood serum must be equal to maintain electroneutrality of the bodily fluids. Yet, when one compares concentration of the main ions - Na+ and K+ with the main anions - Cl- and HCO3-. in the blood serum , the apparent lack of negative ions, i.e. anion gap, is observed. It is constituted by the negatively charged blood proteins, phosphates and sulphates. AG is calculated in dogs and cats in diagnostics of metabolic acidosis. Its value increases in the course of the lactate acidosis, that is in hypoxemia, shock and sepsis, and in ketone acidosis, that is diabetes and renal failure (1,4,8,9,12).
Task, the aim of the article The aim of the article was to test usefulness of the calculated anion gap ( AG ) value in diagnostics of reasons for arrhythmias and disturbances of acid-base equilibrium in Boxers.
© Piotr Slawuta, Agnieszka Noszczyk-Nowak Agnieszka, Jozef Nicpon, Agnieszka Kurosad, 2009
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Material and methods
The control group ( I ) included 10 Beagle dogs and the examined group ( II ) - 20 Boxer dogs in which arrhythmias had been diagnosed : atrial fibrillation with rapid ventricular rhythm - 240/260/min ( 8 dogs ), sustained ventricular tachycardia ( 5 dogs ), numerous ventricular extrasystoles and nonsaturated ventricular tachycardia ( 4 dogs ) , and third degree atrioventricular block ( 3 dogs). The arterial blood was collected from the femoral artery and the venous blood was collected from the radial vein. In the arterial blood pH, pCO2, HCO3- , pO2 were determined, and in the venous blood the concentration of Na+, K+, Cl- was determined. For both groups the AG value was calculated using the formula: ([Na+mmol/l]+[K+mmol/l])-([Cl-mmol/l]+[HCO3-mmol/l]) (2), then the obtained ions concentrations, AG values,and ABE parameters were compared. The arterial blood was collected from the femoral artery ( 1 ml of blood ) to a heparinased syringe provided with a needle of 0.7 in internal diameter. The blood was stored in a container with ice after collection.The place of insertion of the needle was pressed for about 5 min after collection of blood to avoid hematoma.Immediately after collection the blood was transported to the analytical laboratory in the place of examination.Determination of ABE parameters and remaining analyses were performed using Osmotech OPTI Blood Gas Analyser and Vet abc™ Animal Blood Count devices. The results were subject to the statistical analysis. The mean value and standard deviation were calculated. U Mann-Whitney test was used to determine differences between the groups. Testing was performed at the level of statistical significance p<0,05.
Results of research
The mean concentration of ions in the blood serum of the group I and II dogs did not differ statistically - Tab.1. The mean AG value differed statistically in both groups - Tab.2. Figure 1 shows a graphic comparison of AG in both groups. ABE parameters obtained in the present study are given in Tab.3. The significantly lower HCO3- concentration , in combination with lower pH and pCO2 in the arterial blood of the group II dogs as well as an increased AG value indicate compensated metabolic acidosis in these dogs ( 2 ).
Table 1. Comparison of concentration of examined ions in blood serum
GrupaI Grupa II
Na+mmol/l 143,88 ±1,8 147,86 ±3,75
K+ mmol/l 4,96 ±0,48 4,67 ±0,37
Cl- mmol/l 108,61 ±1,42 110,85 ±3,52
Table 2. Comparison of anion gap value in both groups of examined dogs
Grupa I Grupa II
LA mmol/l 12,54* ±1,31 19,34* ±2,51
Range of obtained values mmol/l 11,12- 14,6 16,16 - 23,85
* - statistically significant
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Figure 1. Comparison of AG values in both groups
AG com parison
25 20 -15 Ö10 E 5 E 0
Examined groups
Table3. Comparison of examined ABE parameters
Grupa I Grupa II
pH 7,44 ±0,02 7,43 ±0,02
pCO2 mmHg 33,07 ±3,3 32,21 ±4,47
pO2 mmHg 96,92 ±16,89 97,08 ±7,9
HCO3- mmol/l 27,68* ±1,66 20,77* ±2,64
* - statistically significant Conclusions
1) Boxers with arrhythmias are affected by compensated metabolic acidosis ; even though
2) the concentration of Na+, K+ and Cl- ions in the blood serum of healthy dogs and Boxers with arrhythmias is similar, the calculated AG value differs in a statistically significant way; therefore
3) calculation of AG value may be helpful in diagnosing reasons for arrhythmias and ABE disturbances in dogs.
Reference
1. Bruegger D, Kemming GI, Jacob M, Meisner FG, Wojtczyk CJ, Packert KB, Keipert PE, Faithfull NS, Habler OP, Becker BF, Rehm M. Causes of metabolic acidosis in canine hemorrhagic shock: role of unmeasured ions. Crit Care. 2007, 11, R130
2. Di Bartola S.P. Fluid, electrolyte and acid base disorders in small animal practice. Saunders Elsevier 2006 St Louis
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5. Fantuzzi, S. Caico, S. Amatruda, O. Cervini, P. Abu-Turky, H. Baratelli, L. Donati, D. Gastaldi, L. Hemodialysis-associated cardiac arrhythmias: a lower risk with bicarbonate?. Nephron. 1991, 58, 196-200.
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6. Fessler HE; Brower RG; Wise RA; Permutt S Effects of systolic and diastolic positive pleural pressure pulses with altered cardiac contractility. J Appl Physiol 1992 73, 498-505.
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8. Nappert G, Dunphy E, Ruben D, Mann FA. Determination of serum organic acids in puppies with naturally acquired parvoviral enteritis. Can J Vet Res. 2002, 66, 15-8
9. Paulson WD. Effect of acute pH change on serum anion gap. J Am Soc Nephrol. 1996, 7, 357-63.
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13. Spier AW, Meurs KM. Assessment of heart rate variability in Boxers with arrhythmogenic right ventricular cardiomyopathy. J Am Vet Med Assoc. 2004, 224, 534-7
Summary
ABE disturbances, similarly to ions concentration, may affect the ECG curve parameters. The aim of the study was to test usefulness of the calculated anion gap (AG) value in diagnostics of reasons for arrhythmias in Boxers. The control group included 10 Beagle dogs and the examined group - 20 Boxer dogs with diagnosed arrhythmias. In both groups the arterial blood was collected from the femoral artery and the venous blood was collected from the radial vein. In the arterial blood pH, pCO2, HCO3, pO2 were determined. The concentration of Na+, K+, Cl' was determined in the venous blood. The AG value was calculated for both groups using the formula ([Na+mmol/l]+[Kmmol/l])-([Clmmol/l]+[HCO3mmol/l]).
Then the obtained ions concentrations, AG values and ABE parameters were compared. The mean ions concentrations in the blood serum of the group I and II dogs did not differ statistically. The mean AG value and HCO3 concentration differed in a statistically significant way.
Conclusions : Boxers with arrhythmias were affected by compensated metabolic acidosis; even though the concentration of Na+, K and Cl' is similar in healthy dogs and Boxers with arrhythmias, the calculated AG value differs in a statistically significant way. Therefore, the calculation of the AG value may be helpful in diagnosing reasons for arrhythmias.
Cmammx nadiümna do peda^ii 23.09.2009
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