Bicarbonato de sódio...

A propósito de uma conversa que tive com a Jacinta na nossa última urgência sobre a administração de bicarbonato de sódio a doentes com acidose láctica, fica o resumo de um artigo de revisão sobre o assunto.

O artigo apresenta e analisa criticamente resultados de vários estudos experimentais e clínicos e está dividido nas seguintes áreas:

• Is a low pH bad?
• Can sodium bicarbonate raise the pH in vivo?
• Does increasing the blood pH with sodium bicarbonate have any salutary effects?
• Does sodium bicarbonate have negative side effects?

Sodium bicarbonate is clearly effective in raising the arterial pH in critically ill patients with lactic acidosis. The impact on intracellular pH is unknown in such patients, but extrapolation from extensive animal studies suggests that it is negative.

Despite the correction of arterial acidemia, sodium bicarbonate, like DCA, has no favorable cardiovascular effects, even for patients with severe acidemia and receiving continuous infusions of catecholamines. Although hemodynamic improvement is not the only mechanism by which bicarbonate might be beneficial, animal studies have failed to yield alternatives.

Even theoretical arguments in favor of sodium bicarbonate administration rely on a naive representation of acid-base physiology, ignoring the complex compartmentalization of pH, the second-level effects of bicarbonate infusion, the impact of carbon dioxide generation, or the negative consequences of hyperlactatemia.

We believe most clinicians who continue to use bicarbonate for patients with severe lactic acidosis do so largely because of their inclination to action: How can I “fail” to give bicarbonate when no alternative therapy is available and the mortality of this condition is so high? The oft-cited rationale for bicarbonate use, that it might ameliorate the hemodynamic depression of metabolic acidemia, has been disproved convincingly.

Any future role for bicarbonate in these patients depends on the formulation of new hypotheses of efficacy followed by animal and clinical studies to seek to confirm any proposed benefit. Given the current lack of evidence supporting its use, we cannot condone bicarbonate administration for patients with lactic acidosis. We extend this to those with pH , 7.2 on vasoactive drugs, inasmuch as bicarbonate has no measurable beneficial effects even in these sickest patients. Indeed, we do not give or advise bicarbonate infusion regardless of the pH.

Fonte: Forsythe SM, Schmidt GA: Sodium Bicarbonate for the Treatment of Lactic Acidosis. CHEST 2000; 117:260–267.