Effects on divalent cations of a haemodilution technique using ACD blood in paediatric patients undergoing bypass open-heart operations

Plasma ionized calcium during paediatric anaesthesia: effects of pH and succinylcholine

Variations of plasma ionized calcium and pH were studied in 16 children anaesthetized with halothane and succinylcholine for minor surgery. During anaesthesia, a close negative correlation was noted between pH and ionized calcium. Intubation was followed by a fall of the ionized calcium concentration. A mean decrease of 0.04 mmol X L-1 was noted, without pH change. The acute elevation of carbon dioxide following extubation allowed the in vivo effects of pH on ionized calcium to be studied. For each pH unit decrease, a mean rise of 0.60 mmol X L-1 of ionized calcium was found. During the study, no significant variations of plasma total calcium concentration were observed. The variations in the hydrogen ion concentration and the administration of succinylcholine were accompanied by changes of the free calcium ion concentration, due probably to alterations in calcium binding to proteins, and perhaps to the formation of a calcium complex with anions. Our results emphasize the importance of knowledge of the pH for the interpretation of ionized calcium variations in the presence of acid-base disturbances.

Laboratory and clinical effects of the infusion of ACD solution during plateletpheresis

Transfusion of massive amounts of citrate anticoagulated blood during plateletpheresis with the intermittent flow centrifuge can produce symptoms and electrocardiographic changes suggestive of hypocalcemia. Following 15 procedures the ionized calcium decreased by an average of 32.4%, the average postpheresis serum citrate was 26.7 mg/dl and the QT interval was prolonged by 0.08 sec. Twelve plateletphereses performed with half-strength ACD solution caused an average decrease in ionized calcium of 16%, serum citrate levels of 12.5 mg/dl and QT prolongation of 0.04 sec. No donors experienced significant clinical symptoms with citrate infusion rates of less than 65 mg/kg/h. Solutions with citrate concentrations lower than ACD-A should be developed for use in plateletpheresis procedures involving citrate infusion rates greater than this.