Hyponatremia and cardiopulmonary bypass.

A 68-year-old man presented with recurrent angina after coronary rtery bypass graft (CABG) surgery. He also was noted to have severe yponatremia. He initially presented at age 46 with unstable angina and nderwent 3-vessel CABG (saphenous vein grafts to the left anterior escending, right coronary, and obtuse marginal arteries). He did well ntil he presented 22 years later with complaints of chest pain. He nderwent a stress echocardiographic evaluation, which showed 1-mm psloping ST depression in the anterior leads, associated with premaure ventricular contractions in a bigeminal distribution. There were no egional wall motion abnormalities and no symptoms during the test. ardiac catheterization showed a normal left main artery, a 50% roximal and a 100% mid-left anterior descending artery lesion (LAD), 0% mid-circumflex artery lesion, 80% ostial first obtuse marginal rtery occlusion, and 100% mid-right coronary artery lesion. The vein raft to the distal right coronary artery showed a 30% occlusion, and he graft to the mid-LAD had a 60% lesion. The graft to the marginal ranch was not visualized. Attempts at stenting the native left circumex lesion resulted in a dissection. An attempt to stent the obtuse arginal branch was unsuccessful. He continued to have intermittent ngina. It was decided to perform repeat CABG surgery. His medications on admission included aspirin, 325 mg/d, isosorbide initrate, 30 mg/d, valsartan, 160 mg/hydrochlorothiazide 25 mg/d, llopurinol, 300 mg/d, esomeprazole, 40 mg/d, quinine, 325 mg/d, imvastatin, 20 mg/d, and metoprolol, 25 mg/d. Laboratory analysis evealed the following: Na of 124 mmol/L, K of 3.8 mmol/L, Cl of 89 mol/L, HCO3 of 24.2 mmol/L, blood urea nitrogen of 11 mg/dL, Cr f 0.9 mg/dL, glucose of 142 mg/dL, white blood cells of 7,300/mm3, ematocrit of 34.1%, platelets of 179,000/mm3, prothrombin time of 2.5 seconds, partial thromboplastin time of 30.4 seconds, and tropoin-T of 0.07 ng/mL. Liver function tests were normal. Concerns were raised about CPB in the setting of hyponatremia with serum sodium of 124 mmol/L. However, his acute coronary artery issection prompted urgent surgery despite the electrolyte disturbance. A smooth induction of general anesthesia occurred. The CPB circuit as primed with 1,200 mL of lactated Ringer’s solution, 100 mL of 5% albumin, and 250 mL of 5% albumin. Five hundred milliliters of ormal saline were added to potentially minimize any additional hyonatremia caused by the pump prime. Warm (37°C), near-continuous lood cardioplegia was administered, and his body was cooled to 32°C Table 1). Serum sodium decreased to a low of 110 mmol/L in the etting of a glucose level of 773 mg/dL with CPB (Fig 1). He underent a left internal mammary artery graft to the left anterior descending rtery, saphenous vein graft to the posterior descending branch of the ight coronary artery, sequential saphenous vein graft to the first and econd obtuse marginal coronary arteries, and a saphenous vein graft to diagonal coronary artery. A bolus of 10 U of regular insulin, followed y a continuous infusion of 10 U/h, were administered when the serum lucose reached 336 mg/dL. An additional 10 U of regular insulin were iven to treat a serum glucose of 542 mg/dL followed by 20 U for a lucose of 772 mg/dL. Spontaneous organized ventricular activity esumed on removal of the aortic cross-clamp, and he was weaned from PB without the use of vasopressors. The insulin infusion was dereased to 5 U/h when a serum glucose of 485 mg/dL was reached.