Effects of a Continuous Infusion of Tris(hydroxymethyl)aminomethane on Acidosis, Oxygen Affinity, and Serum Osmolality

Abstract

The effects of a continuous infusion of tris(hydroxymethyl)-aminomethane (THAM) on pH, base excess, p50, serum osmolality, and plasma drug concentration during respiratory acidosis were studied in newborn piglets. Measurements were made during three experimental periods: (1) control period with normal blood gases; (2) hypercapnia period, and (3) hypercapnia plus THAM period (THAM infusion: 1.65 mmol/kg/h). pH decreased and paCO₂ increased between control period (7.40 ± 0.05 and 45 ± 3 mm Hg) and hypercapnia period (7.24 ± 0.06 and 59 ± 2 mm Hg; p < 0.001; mean ± SD). pH returned to baseline (7.37 ± 0.04) during the hypercapnia plus THAM period, while paCO₂remained elevated (63 ± 4 mm Hg). p50 increased from 30.7 ± 5.9 to 38.3 ± 4.7 (p < 0.05) during hypercapnia and decreased with hypercapnia plus THAM. THAM concentration and base excess increased with time and were linearly related. Serum osmolality was unchanged during the THAM infusion. We conclude that continuous infusion of THAM is effective in normalizing pH during respiratory acidosis in the piglet.

Permissive hypercapnia. How permissive should we be?

“…Similar to Carbicarb, it does not generate CO 2 , There is no sodium load resulting from THAM, but its use has been discouraged based on possible deleterious side effects such as hypotension, hypoglycemia, and marked shifts to the left of the hemoglobin dissociation curve (190). However, two recent animal studies failed to substantiate adverse effects of continuous THAM infusion in the treatment of respiratory acidosis (190,191).Perhaps the clinical usefulness of THAM should be reevaluated. Should adverse consequences of acidosis, such as intolerable pulmonary hypertension or the incessant need to increase adrenergic support, occur and remain unresponsive to buffer therapy, one might be led to increase ventilation and settle for airway pressures higher than the ideal goal.…”

Neuroprotection in Surgery

“…However, questions regarding its optimal administration, e.g. , continuous versus intermittent dosing, have not been answered 22,42 …”

“…THAM is a reasonable choice to reduce acidosis, 22,23,42 and appears to be efficacious during hyperventilation (which is commonly used intraoperatively) 18,19,43 . It has been shown to minimize extracellular pH decrease (acidosis) in focal cerebral ischemia, an effect which is not the result of CBF augmentation 44 .…”

Sodium Bicarbonate Use in the Treatment of Acute Neonatal Lactic Acidosis

“…Additionally, these authors disputed the conclusions from an animal study published by Rudolph and Yuan that promoted the use of sodium bicarbonate to both reduce H 1 concentration and modify pulmonary vascular resistance. 21 Chelating tromethamine is the end product of th a m; this metabolite is excreted by the kidneys and is therefore not dependent on adequate ventilation. 10,11,17,18 Malik and Kidd's work with dogs found that correction of pH was less important than correction of hypoperfusion, further disputing the benefit of the popular Usher regimen.…”