Hypocalcemia induced during major and minor abdominal surgery in humans

Hypocalcemia has only been rarely reported during surgical procedures not i nvolving massive blood transfusions. The frequent observation in our hospit al of a low serum ionized calcium level during surgery in nonacutely ill pa tients prompted us to investigate the calcium-PTH axis in three groups of s ubjects undergoing major (hepatectomy; n = 10), moderately severe, or minor surgery under general anesthesia (colectomy; n = 7, herniorrhaphy; n = 9) compared to that in one group of minor surgery cases under epidural anesthe sia (herniorrhaphy; n = 15). Serum samples were obtained before anesthesia, after anesthesia but before surgery, and 40 and 120 min after the beginnin g of surgery in all groups of patients and for up to 3 days in major and mo derately severe cases. Significant falls (P < 0.01), always proportional to the severity of the surgical/anesthesia procedure, were observed for ioniz ed calcium (6-20%), total calcium (8-19%), and albumin (8-23%) accompanied by increases in intact PTH (105-635%). The decrease in ionized and total ca lcium correlated with a decrease in albumin (P < 0.001). Phosphorus, pH, an d magnesium levels remained within the normal range. Adjustment of ionized calcium for variation in albumin revealed that 50 - 100% of the variation i n ionized calcium could be attributed to a fall in albumin resulting from f luid administration to patients before admission to the surgery ward and be tween the onset of anesthesia and the end of surgery (1.2-5.6 L). Albumin- and pH-independent residual ionized calcium decreases of 12.2% in the hepat ectomy group, 4.6% in the group of moderately severe and minor cases under general anesthesia, and 3.7% in the control group reflected the severity of the surgical/anesthesia procedure.