Severe hypophosphatemia following elective abdominal aortic bypass grafting

Serum phosphate levels and urinary phosphate excretion were investigated in ten patients undergoing elective abdominal aortic bypass grafting. The abdominal aorta was cross-clamped peroperatively for 50-95 min. The median serum phosphate was within reference range (0.80-1.55 mmol/l) during cross-clamping and for the first 24 hours after revascularization of the lower limbs. At 48 hours there was statistically significant fall in the serum phosphate level in all patients, with median reaching a nadir of 0.49 mmol/l. At 72 hours this level had risen to 0.69 mmol/l, and reference range had been regained 7 days postoperatively. The median urinary phosphate excretion (mmol) was 38.4 during the first 24 postoperative hours, and 34.7 and 10.0 on the 2 subsequent days. The median ratio of urinary phosphate to creatinine clearance was, respectively, 0.47, 0.37, 0.09 and 0.08 on postoperative days 1, 2, 3 and 7. The study indicated that patients undergoing aortic bypass grafting with protracted regional muscular ischemia may constitute a risk group with respect to development of severe postoperative hypophosphatemia.