Q: Tromethamine (tris-hydroxymethyl aminomethane - THAM) buffers hydrogen ions and is an alternative for use in acidosis instead of 'bicarb'. THAM can be used in all of the following situations except? 

A) hypercapnic respiratory failure, 
B) drug intoxications, 
C) Acidosis with severe hypernatremia
D) renal failure
E)  mixed metabolic and respiratory acidosis



Answer: D

Tromethamine (THAM) is an alternative to NaHCO3 for use in acidosis. It buffers hydrogen ions by virtue of its amine (NH2) moiety

Bicarbonate generates CO2, 

THAM consumes CO2

 THAM get cleared by urinary route, thus is less effective when renal function is reduced. Also it may cause hyperkalemia and hypoglycemia. It has been used with success in acidosis associated with drug intoxications but in non-intubated patient it should be use with caution as rapid alkalization of the central nervous system may cause respiratory depression. THAM can be an excellent choice in hypercapnia as it clears CO2. It has also been used with success in diabetic ketoacidosis, RTA and gastroenteritis. Another advantage is that THAM does not cause a sodium load.


Reference:

Kallet RH, Jasmer RM, Luce JM, et al. The treatment of acidosis in acute lung injury with tris-hydroxymethyl aminomethane (THAM). Am J Respir Crit Care Med 2000; 161:1149.