Studies on acid-base status (Stewart's model) of young camels (Camelus dromedarius) after acid-load with NH4Cl.

UNLABELLED: The identification of the reference values of Stewart variables and the changes in the acid-base status of the blood and urine in relation to the age after acid-load were studied in desert species of camels. 14 healthy young camels (age: 3-5 months) and 22 adult camels (age: 5-8 years) were used to provide the reference and percentile ranges of the Stewart variables. In the experiments, 24 healthy young camels (age: < 3-5 months) were infused with 5M NH4Cl solution (dose: 1.0 ml/kg) through a permanent intravenous catheter. Venous blood and urine samples were collected before infusion (0 hours). After the start of infusion, venous blood samples were collected at 2, 4, 6, 8 and 24 hours, and urine samples were collected at 8, 24 and 48 hours. Blood and urine samples were used for the determination of the various acid-base parameters, including the non-respiratory Stewart variables. The reference range of serum-[strong ion difference = SID3] was 39-52 mmol/l for all age groups. The reference values of serum-[acid total = A-] were between 10-17 mmol/l for all age groups. Serum-[Atotprotein] and -[Atot-albumin] showed a reference range of 19-24 mmol/I and 20-28 mmol/l, respectively. By 2-8 hours after the NH4Cl-load, the Stewart variables (serum-[SID3] and serum-[A(tot-protein)]) decreased significantly, and as a consequence, the blood pH decreased. Generally, the loaded young camels showed a transient moderate hyperchloraemic acidosis with a slight hypoproteinaemic alkalosis. These malfunctions were accompanied by increased renal fractional excretion of chloride and sodium and decreased urine pH. CONCLUSION: The identified reference values of the Stewart variables can be used for the clinical diagnosis of acid-base disturbances in camels. With the assistance of the non-respiratory Stewart variables ([SID3] and [Atot]), we can detect the determining influence of strong electrolytes (Na+, K+ and Cl-) and weak acids (proteins, Pi) on the physiological and pathological acid-base status of the animals.

Characterisation of acid-base abnormalities in pigs experimentally infected with Chlamydia suis.

This study characterises the acid-base abnormalities in pigs experimentally infected with Chlamydia suis (Henderson-Hasselbalch equation and Constable's simplified strong ion equation). Eight pigs were challenged with the respiratory pathogen C. suis and four pigs served as non-infected controls. Pigs were monitored from 7 days before challenge to 8 days post-inoculation. Clinical examination was performed twice daily and venous blood samples were collected every two days. Blood-gas analysis, haemoxymetry, serum biochemical analysis and electrophoresis were performed in order to characterise the acid-base derangement. Aerosol challenge with C. suis resulted in severe acid-base disturbance characterised by acute respiratory acidosis and strong ion (metabolic) acidosis secondary to anaerobic metabolism and hyper L-lactataemia. Maximal changes were seen at day 3 post-inoculation when severe clinical signs of respiratory dysfunction were evident. The results of the study provide new information regarding the pathophysiology of respiratory infection caused by C. suis and the applicability and diagnostic utility of different approaches for assessing acid-base status in pigs.

[Different CO2-stunning procedures and post mortem obtained lung lesions in response to the corneal reflex and parameters in blood of slaughtered pigs]. / Einfluss unterschiedlicher CO2- Betäubungsvarianten sowie postmortaler Lungenbefunde auf die Antwortreaktion des Kornealreflexes und Parameter im Stichblut von Schlachtschweinen.

The effect of different CO2-stunning on the corneal reflex response and blood parameters in (arterio-venous) killing blood was investigated in n = 614 slaughter pigs (carcass weight = 92-94 kg) at two different abattoirs. CO2-anaesthesia lead to remarkable decrease of PO2 (hypoxaemia), increase of PCO2 (hypercapnia), decrease of pH (respiratory acidosis) and increase of [strong ion difference = SID3] (basic reaction caused by electrolytes). Pigs with subclinical post mortem obtained lung lesions showed no significant modified value of the reflex answer or changes in parameters of killing blood compared to the animals with healthy lungs. The CO2-stunning with 90% CO2 and 120 s exposure time resulted in notably less undesired positive reflex responses (6% of slaughter pigs) than the CO2-stunning with 90% CO2 and only 90 s exposure time (15% of slaughter pigs). The occurence of the positive reflex response, which means an inadequate depth of anaesthesia, in slaughter pigs can be safely eliminated by use of qualified cut off values of killing blood parameters. These parameters can be measured rapidly and validly with ion-sensitive electrodes, making a beneficial monitoring of the used CO2-stunning possible.

Age-dependent response of the acid-base parameters (Henderson-Hasselbalch, Stewart) in healthy calves with experimentally induced metabolic acidosis.

UNLABELLED: The intensity of the response to acid-base parameters in relation to the age after a defined acid load was studied in calves. 32 clinically healthy calves (age: 4-104 days) were infused with 5M NH4Cl solution (dose: 1.0 ml/kg) through a permanent intravenous catheter. Before (0 hrs) and after starting the infusion (2, 4, 6, 8 and 24 hrs) venous blood samples were collected for the determination of the various acid-base parameters. The intensity of the response of the acid-base parameters was estimated by using the "area under curve (AUC)" procedure. By 2-6 hrs after the infusion of the NH4Cl solution, the Henderson-Hasselbalch parameters decreased significantly (decrease pH, decrease [HCO3-]) as did Stewart's variables (decrease [Strong ion difference=SID3], decrease [Acid total = A(tot) or A-]). A transient moderate hyperchloraemic acidosis with a slight hypoproteinaemic alkalosis was observed in all calves in association with a respiratory compensation (decrease PCO2). The younger calves (1st-3rd week) showed a similar pattern of response to the same dose per kg 0.75 acid load with significantly greater acid-base parameters response (higher AUC values) than the older animals. The calculated pH was determined by using the three Stewart variables PvCO2, serum-[SID3] and serum-[A(tot)]. The mean difference was -0.03 to -0.09 compared with the measured pH (7.32-7.40). CONCLUSION: The Stewart model appears to be more successful in providing a comprehensive evaluation of acid-base status compared with the traditional Henderson-Hasselbalch model. The younger calves during the first week of life reacted more sensitively to an equal acidotic condition than the older animals.

[Qualification of the Stewart variables for the assessment of the acid-base status in healthy dogs and dogs with different diseases]. / Eignung der Stewart-Variablen zur Beurteilung des Säuren-Basen-Status bei gesunden und unterschiedlich erkrankten Hunden.

Peter Stewart criticized the traditional theory of the acid-base status by Henderson-Hasselbalch as too simple and incomplete. He developed a new model with 3 independent variables: (1) pCO2, (2) SID (strong ion difference) and (3) Atot (Acid total). In healthy and ill dogs the diagnostic usefulness of both acid-base models were compared. This study included n=58 healthy dogs and 3 clinical cases of sick dogs. The age of the healthy dogs was 5.0 (2.0-7.0) years (= median (1.-3. quartil)). The 3 clinical cases included (1) a dog with septic shock, (2) with acute renal insufficiency, and (3) with hypovolaemic shock due to gastric torsion. Venous blood was taken of all dogs and the acid-base parameters were determined within < or =30 minutes. Electrolytes and albumin were determined in blood serum and used for calculation of the Stewart variables. Limits of reference intervals (x+/-1.96 - s) were determined for the healthy dogs yielding pCO2 = 3.6-6.5 kPa, [SID3] = 33.1-50.9 mmol/l resp. [SID4] = 31.8-49.6 mmol/l and [Al = 8.5-13.1 mmol/l. In Case 1 the Henderson-Hasselbalch parameters demonstrated the presence of a strong metabolic acidosis with mild respiratory influence (pH, [HCO3-], [BE] and PCO2 at upper range of normal). Analysis of the Stewart variables [SID3] resp. [SID4] revealed an electrolyte imbalance with [Cl-] and [lactate-] as the reason for metabolic acidosis. Case 2 showed a metabolic acidosis with respiratory compensation (pH, [HCO3-], [BE] and PCO2). Analysis of the Stewart variables with [SID3] resp. [SID4 caused by [K+], [Na+] and [lactate-]demonstrated the acidotic metabolism due to a renal malfunction. Case 3 had a metabolic acidosis (pH-value in the lower range) caused by electrolyte imbalances ([SID4]. The Stewart variables allow a better understanding of the causes of acid-base-disturbances in animals with implications for successful therapy via infusion.

The impact of dietary cation anion difference (DCAD) on the acid-base balance and calcium metabolism of non-lactating, non-pregnant dairy cows fed equal amounts of different anionic salts.

We evaluated the impact of the dietary cation-anion difference (DCAD) on the influence of anionic salts (AS) on the metabolism of dairy cows using a study-design that included control of feed intake. Ten mature, non-lactating, non-pregnant, Holstein-Friesian-crossbreed cows received 2000 mEq of either one of the seven anionic salts tested, two combinations of the anionic salts or water as control via a rumen cannula. Salts and controls were assigned in a 10x10 Latin square design. Whole blood, serum and urine samples were taken during treatment (TP) and washout period. Samples of whole blood were tested for pH, base-excess and bicarbonate concentrations. In urine, pH and net acid-base excretion (NABE) were analysed. Calcium was measured in serum and urine. According to the different batches of hay, five groups of DCAD were created regarding cluster analysis. Changes in urine and blood parameters were statistically analysed for each DCAD group separately. The different DCAD had an impact on the amount of change in acid-base balance (ABB) and calcium metabolism and for how long these changes lasted. In the DCAD group receiving the highest amount of AS (239 mEq/kg dry matter with AS), changes of ABB were only noticeable in urine and these changes only differed from day zero in the first week of TP (P<0.05). In the other four groups changes of ABB were also visible in blood parameters, but only on a few days of TP did the deviations differ significantly (P<0.05) from day zero. Changes of ABB parameters in urine samples were more pronounced than those in blood and differed clearly from day zero (P<0.05). Parallel to the changes of ABB, calcium concentrations in these samples were significantly increased (P<0.001) in all DCAD groups. Except for the highest DCAD group, ionized calcium concentrations changed over time (P<0.020). However, the differences were very small and only differed from day zero on a few TP days. We conclude that the DCAD of a dairy cow's diet has an important impact on the effect of AS on ABB and calcium metabolism with respect to the duration and amount of change. The target regions of DCAD should be clearly below 100 mEq/kg dry matter to ensure the desired effect on ABB and calcium metabolism. Extremely negative DCAD should be avoided to minimize the risk of clinical acidosis induced by AS.

[Suitability of the peroral administration of the marker creatinine for the quantitative determination of the glomerular filtration rate (GFR) in dogs]. / Eignung der peroralen Verabreichung des Markers Kreatinin zur quantitativen Bestimmung der glomerulären Filtrations- rate (GFR) beim Hund.

Established renal function tests for the quantitative determination of the glomerular filtration rate (GFR) in small animals by means of an exogenous clearance marker like creatinine are based on the intravenous or subcutaneous administration of the marker. In order to simplify performing the test, the suitability of the peroral administration of the marker substance was tested. Exogenous creatinine was administered to 17 Beagle dogs successively by the peroral (dose: 4 g/m2 BSA) and the subcutaneous route (dose: 2 g/m2 BSA). Both routes were tested sequentially in fasted and fed animals. In addition to the peroral administration of creatinine, the absorption marker D-Xylose (dose: 0.5 g/kg body weight) was given per os. Pharmacokinetic parameters were calculated based on serum concentration--time data of both markers. Maximum serum concentrations of the exogenous creatinine (C(max) = 1284 +/- 173 micromol/l) were observed 92 +/- 19 min post-dose (t(max)) in fasted dogs after peroral administration of creatinine. C(max) (956 +/- 209 micromol/l) and t(max) (67 +/- 13 min) were statistically significantly reduced in fed animals. The exogenous plasma clearance of creatinine was about 1/3 lower in fasted animals (94 +/- 15 ml/min/m2) than in fed ones (134 +/- 28 ml/min/m2). The apparent terminal disposition half-life of the exogenous creatinine showed mean values of about 170 min (fasted) and 200 min (fed). After peroral administration of D-Xylose, fasted animals showed higher C(max) (3.9 +/- 0.99 mmol/l) and t(max) values (60 +/- 18 min) than fed dogs (C(max) = 2.2 +/- 0.55 mmol/l, t(max) = 40 +/- 15 min). C(max) and t(max) did not differ between fed and fasted dogs after subcutaneous administration of creatinine. Creatinine clearance was again higher in fed (124 +/- 12.8 ml/min/m2) than in fasted dogs (104 +/- 9.0 ml/min/m2) after subcutaneous administration of the marker. The terminal disposition half-live was, however, similar with about 130-140 min. The route of administration (peroral vs. subcutaneous) did not influence the calculated clearance (no statistical significance when p < 0.01 is required). Creatinine in a dose of 4 g/m2 BSA can be administered by the peroral route of administration for assessing the GFR. For the quantitative determination of GFR standardized condition are required, i.e. animals have to be fasted for > or = 6 hours.

[Evaluation of a modified exogenous creatinine clearance as a suitable renal function test for the small animal practice]. / Bewertung einer modifizierten Plasma-Clearance mit exogenem Kreatinin als ein für die Kleintierpraxis geeignetes Verfahren der renalen Funktionsdiagnostik.

A suitable method in the routine veterinary practice for the quantitative determination of the glomerular filtration rate (GFR) in dogs and cats has not been available until to date. Therefore, we modified the known plasma clearance model (=P-CL). The resulting P-CLterminal was assessed concerning its diagnostic value. P-CL of exogenous creatinine (P-CLcrea) and of inulin were determined in dogs (n=12, Beagle, 6 months of age) and cats (n=11, Domestic Short Hair, 14 months of age). The marker substances were administered as a bolus injection. In fasted dogs, P-CLcrea was 84.3 +/- 14.85 ml/min/m2 after a creatinine dose of 2.4 g/m2. An electrolyte infusion during the clearance determination did not alter the resulting values (p>0.05). In fasted cats, P-CLcrea was 54.7 +/- 5.8 ml/min/m2 (creatinine dose 2.0 g/m2). The inulin clearance, determined at the same time, was 104.5 +/- 19.81 ml/min/m2. Feeding the cats just before and during the test increased P-CL of both markers significantly (p<0.05). In order to adapt the clearance method for diagnostic assessment of GFR in the small animal practice, we aimed at minimizing the number of required blood samples (3 instead of 7 or more) and introduced the modified exogenous creatinine clearance (P-CLterminal). These values determined were 108.4 +/- 20.81 ml/min/m2 in fasted dogs and 66.3 +/- 11.81 ml/min/m2 in fasted cats. An electrolyte infusion (dogs) and feeding (cats) had the same effect on P-CLterminal values as described above for P-CL. In conclusion,the modified exogenous creatinine clearance is a suitable renal function test for the early diagnosis of renal disease in dogs and cats presented in small animal practices.