Effects of a continuous infusion of tris(hydroxymethyl)aminomethane on acidosis, oxygen affinity, and serum osmolality

Effects of alkaline agents on respiratory characteristics in rabbit models of respiratory failure

This study aimed to investigate the effects of alkaline agents on reducing strong inspiratory effort. Rabbits with hypercapnia or lung injury, induced via repeated lung lavage following injurious ventilation, were treated with Saline, NaHCO₃, or Trometamol. In the hypercapnia, minute ventilation and tidal volume were unchanged during NaHCO₃ administration; however, one hour after the end of NaHCO₃ these parameters decreased (82.1+/-7.8 %, 90.8+/-6.0 % of the baseline, respectively, p < 0.05). Trometamol reduced minute ventilation, tidal volume, and respiratory rate after infusion (59.8+/-19.0 %, 87.0+/-9.2 %, 68.2+/-18.4 % of the baseline, respectively, p < 0.05). Alkaline agents did not cause a large change in the cerebrospinal fluid acid-base balance. In the lung injury model, NaHCO₃ and Trometamol had little effect on ventilation. However, Trometamol reduced transpulmonary pressure. Trometamol exerted more inhibitory effects on ventilation than NaHCO₃ in the hypercapnia model, and Trometamol reduced the transpulmonary pressure in the lung injury model.

A Review of the Role of Blood Lactate Measurements in the ICU

The production of hyperlactatemia in the critically ill patient has previously been thought to be primarily related to anaerobic conditions. Newer data suggests that lactate accumulates under aerobic conditions in clinical settings that were previously thought to solely represent anaerobic processes. This review summarizes the present understanding of lactate metabolism and reviews the data supporting use of lactate determinations in the critical care setting. The use of lactate as a marker of inadequate tissue perfusion as well as its role as a prognostic indicator are discussed. The utility of managing lactic acidosis with various buffers is also reviewed.

Guidelines for the treatment of acidaemia with THAM

THAM (trometamol; tris-hydroxymethyl aminomethane) is a biologically inert amino alcohol of low toxicity, which buffers carbon dioxide and acids in vitro and in vivo. At 37 degrees C, the pK (the pH at which the weak conjugate acid or base in the solution is 50% ionised) of THAM is 7.8, making it a more effective buffer than bicarbonate in the physiological range of blood pH. THAM is a proton acceptor with a stoichiometric equivalence of titrating 1 proton per molecule. In vivo, THAM supplements the buffering capacity of the blood bicarbonate system, accepting a proton, generating bicarbonate and decreasing the partial pressure of carbon dioxide in arterial blood (paCO2). It rapidly distributes through the extracellular space and slowly penetrates the intracellular space, except for erythrocytes and hepatocytes, and it is excreted by the kidney in its protonated form at a rate that slightly exceeds creatinine clearance. Unlike bicarbonate, which requires an open system for carbon dioxide elimination in order to exert its buffering effect, THAM is effective in a closed or semiclosed system, and maintains its buffering power in the presence of hypothermia. THAM rapidly restores pH and acid-base regulation in acidaemia caused by carbon dioxide retention or metabolic acid accumulation, which have the potential to impair organ function. Tissue irritation and venous thrombosis at the site of administration occurs with THAM base (pH 10.4) administered through a peripheral or umbilical vein: THAM acetate 0.3 mol/L (pH 8.6) is well tolerated, does not cause tissue or venous irritation and is the only formulation available in the US. In large doses, THAM may induce respiratory depression and hypoglycaemia, which will require ventilatory assistance and glucose administration. The initial loading dose of THAM acetate 0.3 mol/L in the treatment of acidaemia may be estimated as follows: THAM (ml of 0.3 mol/L solution) = lean body-weight (kg) x base deficit (mmol/L). The maximum daily dose is 15 mmol/kg for an adult (3.5L of a 0.3 mol/L solution in a 70kg patient). When disturbances result in severe hypercapnic or metabolic acidaemia, which overwhelms the capacity of normal pH homeostatic mechanisms (pH < or = 7.20), the use of THAM within a 'therapeutic window' is an effective therapy. It may restore the pH of the internal milieu, thus permitting the homeostatic mechanisms of acid-base regulation to assume their normal function. In the treatment of respiratory failure, THAM has been used in conjunction with hypothermia and controlled hypercapnia. Other indications are diabetic or renal acidosis, salicylate or barbiturate intoxication, and increased intracranial pressure associated with cerebral trauma. THAM is also used in cardioplegic solutions, during liver transplantation and for chemolysis of renal calculi. THAM administration must follow established guidelines, along with concurrent monitoring of acid-base status (blood gas analysis), ventilation, and plasma electrolytes and glucose.