Tromethamine

In general, dosage should be limited to an amount sufficient to increase blood pH to normal limits (7.35 to 7.45) and to correct acid-base derangements. The total quantity to be administered during the period of illness will depend upon the severity and progression of the acidosis. The possibility of some retention of tromethamine, especially in patients with impaired renal function, should be kept in mind.

DOSAGE AND ADMINISTRATION Tham Solution (tromethamine injection) is administered by slow intravenous infusion, by addition to pump-oxygenator ACD blood or other priming fluid or by injection into the ventricular cavity during cardiac arrest. For infusion by peripheral vein, a large needle should be used in the largest antecubital vein or an indwelling catheter placed in a large vein of an elevated limb to minimize chemical irritation of the alkaline solution during infusion.

The intravenous dosage of Tham Solution (tromethamine injection) may be estimated from the buffer base deficit of the extracellular fluid in mEq/liter determined by means of the Siggaard-Andersen nomogram. The following formula is intended as a general guide: Tham Solution (mL of 0.3 M) Required = Body Weight (kg) X Base Deficit (mEq/liter) X 1.1* Thus, a 70 kg patient with a buffer base deficit (“negative base excess”) of 5 mEq/liter would require 70 x 5 x 1.1 = 385 mL of Tham Solution containing 13.9 g (115 mEq) of tromethamine.

The need for administration of additional Tham Solution is determined by serial determinations of the existing base deficit. * Factor of 1.1 accounts for an approximate reduction of 10% in buffering capacity due to the presence of sufficient acetic acid to lower pH of the 0.3 M solution to approximately 8.6. Correction of Metabolic Acidosis Associated with Cardiac Bypass Surgery: An adverse dose of approximately 9.0 mL/kg (324 mg/kg) has been used in clinical studies with Tham Solution (tromethamine injection).

Thus, for a 70 kg (154 pound) patient the dose should not exceed a maximum of 35 g per hour (1078 mL of a 0.3 M solution). Repeated determinations of pH and other clinical observations should be used as a guide to the need for repeat doses. Correction of Acidity of ACD Blood in Cardiac Bypass Surgery: The pH of stored blood ranges from 6.80 to 6.22 depending upon the duration of storage.

The amount of Tham Solution used to correct this acidity ranges from 0.5 to 2.5 g (15 to 77 mL of a 0.3 M solution) added to each 500 mL of ACD blood used for priming the pump-oxygenator. Clinical experience indicates that 2 g (62 mL of a 0.3 M solution) added to 500 mL of ACD blood is usually adequate. Correction of Metabolic Acidosis Associated with Cardiac Arrest: In the treatment of cardiac arrest, Tham Solution should be given at the same time that other standard resuscitative measures, including manual systole, are being applied.

If the chest is open, Tham Solution is injected directly into the ventricular cavity. From 2 to 6 g (62 to 185 mL of a 0.3 M solution) should be injected immediately. Do not inject into the cardiac muscle. If the chest is not open, from 3.6 to 10.8 g (111 to 333 mL of a 0.3 M solution) should be injected immediately into a larger peripheral vein.

Additional amounts may be required to control acidosis persisting after cardiac arrest is reversed. Correction of Metabolic Acidosis Associated with RDS in Neonates and Infants: The initial dose of Tham Solution should be based on initial pH and birthweight amounting to approximately 1 mL per kg for each pH unit below 7.4.

Further doses have been given according to changes in P a O 2 , pH and PCO 2 . Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit (see CONTRAINDICATIONS ).