The Science Journal of the American Association for Respiratory Care
Background: PHV in ALI requires induced respiratory acidosis that may compromise cellular function in the presence of metabolic acidosis and shock. The renal excretion of protonated THAM lowers CO2 production in metabolic acidosis(1) and directly lowers PaCO2.(2) We report the use of THAM in 4 cases of PHV and one case of severe acidosis with eucapnea in ALI.
Methods: THAM was administered at a mean dose of 2.1 ± standard deviation (sd) of 1.63 mmol/kg/hour. Arterial blood gases were taken before, and within an hour after THAM started. Alveolar ventilation ([Vdot]A) was calculated from measurements of minute ventilation and physiologic deadspace. Deadspace was measured on Assist/Control ventilation using a Deltatrac metabolic monitor (3) Wilcoxon Sign-Rank tests were used for paired comparisons (Alpha = 0.05.).
Results: Mean PaCO2 was significantly lower at equivalent levels of [Vdot]A.
|Case||pHa||PaCO2 mmHg||[Vdot]A L/min||pHa||PaCO2 mmHg||[Vdot]A L/min|
|± sd||± .04||± 26.9||± 4.5||± .08||± 24.8||± 2.5|
|?P < 0.05.|
Conclusions: High dose THAM directly lowers PaCO2. Buffering acidosis with THAM may facilitate the use of PHV during ALI.
1. Nahas G, Reveillaud A, Strauss J: Renal effects of tris (hydroxymethyl) aminomethane during CO2 load. Am J Physiol. 1963; 204(1): 113-118.
2. Nahas G: Use of an organic carbon dioxide buffer in vivo. Science 1959; 129: 782-783.
3. Lum L, Saville A, Venkataraman ST: Accuracy of physiologic deadspace measurement in intubated pediatric patients using a metabolic monitor: Comparison with the douglas bag method. Crit Care Med. 1998;26: 760-754.