Experimental protocol for metabolic acidosis induction by intravenous administration of hydrochloric acid in sheep / Protocolo de indução experimental de acidose metabólica por administração intravenosa de ácido clorídrico em ovinos

The aim of this study was to assess the magnitude and duration of blood and urine changes and the side effects of hyperchloremic acidosis induced by the intravenous administration of hydrochloric acid in sheep. Five healthy, crossbred adult ewes, with a mean body weight of 44±2.9kg were used. The hydrochloric acid solution was administered intravenously at a rate of 25mL/kg/h for 4 hours continuously. Venous blood and urine samples were collected and pH values, blood carbon dioxide partial pressure, bicarbonate, base excess, strong ion difference, anion gap, total concentration of nonvolatile buffers, creatinine, plasma L-lactate, plasma and urine sodium, potassium, and chloride were determined. The experimental protocol induced severe hyperchloremic acidosis at the end of the infusion, with a decreased plasma strong ion difference. The fractional excretion of sodium and chloride remained increased during 4 hours after the infusion. Aciduria was observed at approximately 24 hours. Twenty-four hours after the infusion, the animals showed mild and compensated metabolic acidosis. This protocol was effective in inducing severe and long-lasting hyperchloremic acidosis and did not cause serious side effects. Therefore, this protocol can be used safely in adult sheep for studies on the treatment of this condition.(AU)

O objetivo deste estudo foi avaliar a magnitude e a duração das alterações sanguíneas e urinárias, bem como os efeitos colaterais da acidose hiperclorêmica induzida por administração intravenosa de ácido clorídrico, em ovinos. Foram utilizadas cinco ovelhas mestiças, adultas, sadias, com peso médio de 44±2,9kg. A solução de ácido clorídrico foi administrada por via intravenosa, na velocidade de 25mL/kg/h, totalizando quatro horas de administração contínua. Amostras de sangue venoso e de urina foram colhidas, e determinaram-se os valores de pH, pressão parcial de dióxido de carbono, bicarbonato, excesso de bases, diferença dos íons fortes, ânion-gap, creatinina, lactato L, sódio, potássio e cloro. O protocolo de indução experimental foi capaz de induzir acidose hiperclorêmica grave ao término da infusão, com diminuição da diferença dos íons fortes plasmáticos. Houve aumento da excreção fracionada de sódio e cloro por até quatro horas após o término da infusão. A acidúria foi observada por cerca de 24 horas. Após 24 horas do início da infusão, os animais apresentaram acidose metabólica leve e compensada. Esse protocolo foi eficaz na indução da acidose hiperclorêmica grave e duradoura e não causou efeitos colaterais. Conclui-se que o protocolo pode ser usado com segurança em ovelhas adultas, para estudos sobre tratamento dessa condição.(AU)

Intravenous administration of a polyionic solution containing 84 mEq/l of lactate resolves experimentally induced hyperchloraemic acidosis in horses.

REASONS FOR PERFORMING STUDY: Treatment of metabolic acidosis using sodium bicarbonate solutions is safe when blood gas analysis is available. The evidence that solutions containing metabolisable buffers can be used as an alternative for treatment of metabolic acidosis in horses is of practical interest. OBJECTIVES: To investigate the safety and efficacy of a polyionic solution containing 84 mEq/l of lactate (L84) for the correction of induced hyperchloraemic metabolic acidosis. STUDY DESIGN: Non-randomised crossover design. METHODS: Five healthy, adult, crossbred horses were used. A solution containing 100 mmol/l of HCl was infused intravenously (100 ml/kg bwt) for 5 h to induce metabolic acidosis. Metabolic acidosis was induced in each horse twice, with a minimum 15-day interval after recovery from the first induction: the first time no treatment was administered (control group) and the second time horses were treated with an intravenous infusion of L84 solution, 100 ml/kg bwt for 5 h, beginning 3 h after the end of HCl infusion. Venous blood samples were taken at 0, 2.5, 5, 8, 10.5, 13, 24 and 48 h; and urine at 0, 5, 8 and 13 h. Laboratory data included pH (blood and urine), PCO2 , HCO3- , base excess, total plasma protein concentration, l-lactate, Na+ , K+ , Cl- , strong ion difference (SID4 ), anion gap, change in plasma volume and fractional excretions of Na+ , K+ and Cl- . Effects of time and treatment were tested by 2-way repeated measures ANOVA. RESULTS: Severe hyperchloraemic metabolic acidosis was induced. In the untreated horses, correction of the imbalance occurred gradually, and mild acidosis was still present at 48 h. In horses treated with the L84 solution, acidosis was corrected by the end of the infusion. There were no adverse effects with the administration of the L84 solution. CONCLUSIONS: A polyionic solution containing 84 mEq/l of lactate effectively corrected induced metabolic acidosis in horses within 5 h.

Efeito alcalinizante da solução de Ringer com lactato em ovelhas sadias e acidóticas / Alkalinizing effect of lactated Ringer's solution in healthy and acidotic sheep

O estudo teve o objetivo de testar a hipótese de que o efeito alcalinizante da solução de Ringer com lactato (SRL) pode ser maior nos animais portadores de acidose metabólica do que nos sadios, como consequência da necessidade de retorno ao equilíbrio. Seis ovelhas receberam a SRL em volume correspondente a 10% do peso corporal, administrada por infusão contínua intravenosa, durante quatro horas, em duas condições definidas: enquanto eram saudáveis e após a indução experimental de acidose láctica ruminal aguda (ALRA). Amostras de sangue venoso e de urina foram colhidas em quatro momentos: antes do início da infusão, na metade do volume infundido, ao término da infusão e duas horas após. Foram determinados valores de pH sanguíneo e urinário, de pCO2, HCO3 - e BE no sangue, de Na+, K+, Cl-, SID, AG, PPT, Atot e lactato L no plasma, e das excreções fracionadas urinárias de Na+, K+, Cl- e lactato L. A SRL provocou hemodiluição, mas não interferiu nos equilíbrios eletrolítico e acidobase das ovelhas sadias. Apesar de eficaz para reverter a desidratação, não foi capaz de corrigir a acidose metabólica presente após a indução da ALRA.

The aim of this study was to investigate if the alkalinizing effect of lactated Ringer's solution (LRS) is greater in animals with metabolic acidosis than in healthy ones, as a result of the need to restore acid-base balance. LRS was intravenously infused in a volume corresponding to 10% of body weight, continously during four hours, in two definite conditions in the same six ewes: when they were healthy and after experimentally induced acute rumen lactic acidosis (ARLA). Venous blood and urine samples were taken in four moments: before the beginning, in the middle, at the end of the infusion and two hours after. Blood and urine pH, blood pCO2, HCO3 - and BE, and plasma Na+, K+, Cl-, TP and L lactate were measured. Na+, K+, Cl- and L lactate fractional clearance and plasma SID, AG, and Atot were calculated. LRS caused hemodilution but didn't change electrolyte and acid-base balances in healthy ewes. When ewes were affected by ARLA, the infusion of this solution was effective for dehydration reversion but was unable to correct metabolic acidosis.