PubMed1987
The hemodynamic effects induced by thiopental and a decrease in blood ionized calcium are uniform. This investigation was undertaken to show a possible decrease in ionized blood calcium during induction of general anesthesia with thiopental. Twenty-four patients aged 19-79 years (median 57) were studied. None had any known parathyroid disease, malabsorption, or chronic renal insufficiency, and none were receiving calcium channel blockers. For the analysis of blood Ca++, pH, and PCO2, blood samples were drawn anaerobically into a heparinized syringe from an i.v. cannula. A special heparin solution was used (S4500 Radiometer, Copenhagen) to avoid the influence of heparin on the Ca++ determination. The initial 2 ml were discarded. No samples were drawn in the first 3 min after removal of the tourniquet. A maximum of 100 ml isotonic saline was infused between the two samplings. The infusion was stopped for at least 30 s before sampling. PCO2, B-Ca++, and pH were measured directly using the ABL 4 (Radiometer, Copenhagen) and the ICA 1 ionized calcium analyzer (Radiometer, Copenhagen). The standard deviation of repeated measurements of B-Ca++ within a short time using the same sample is 0.01 mmol/l on the ICA 1. The samples were drawn just before and 2 min after thiopental injection (median 5.9 mg/kg) was started. The pulse and blood pressure were simultaneously measured. The individual Ca++ measurements are shown in Table 1. The results of the investigation are shown in Table 2.(ABSTRACT TRUNCATED AT 250 WORDS)