Preventing hyponatremic encephalopathy: comparison of serum sodium and osmolality during operative hysteroscopy with 5.0% mannitol and 1.5% glycine distention media.

STUDY OBJECTIVE: To determine whether isotonic 5.0% mannitol is superior to 1.5% glycine in preventing development of hyponatremic encephalopathy.

DESIGN: Prospective, comparative study (Canadian Task Force classification II=2).

SETTING: Gynecology department of a community hospital.

PATIENTS: One hundred twenty-two women undergoing operative hysteroscopy.

INTERVENTIONS: Eighteen blood serum chemical indicators analyzed preoperatively and postoperatively in 61 women undergoing operative hysteroscopy with 1. 5% glycine (group 1) were compared with those of 61 women having similar surgery with 5.0% mannitol (group 2). Fluid deficit (difference between input and output volume of distention fluid) was recorded, and differences between presurgical and postsurgical indicators of the two groups (mean difference score) were compared.

MEASUREMENTS AND MAIN RESULTS: Mean +/- SEM sodium difference scores of groups 1 and 2 were -1.73 +/- 0.42 mEq/L (range -7.00 to 2.00 mEq/L) and -5.04 +/- 1.07 mEq/L (range -36.00 to 3.00 mEq/L), respectively (p <0.01). Serum osmolality difference scores were -6. 88 +/- 1.36 mmol/L (range -13.00 to -1.00 mmol/L) and -1.87 +/- 0.35 mmol/L (range -3 to 15 mmol/L), respectively (p <0.01). Distention fluid deficits were 0.435 +/- 0.071 L (range 0-2.448 L) and 0.473 +/- 0.084 L (range 0-3.640 L), respectively (p = 0.862). Two women (3.4%) in group 1 and five (8.2%) in group 2 developed postoperative asymptomatic dilutional hyponatremia (p = 0.211), which was the only complication. Two of the five women in group 2 developed severe dilutional hyponatremia.

CONCLUSION: We found that 5.0% mannitol distention fluid produces greater postoperative dilutional hyponatremia than 1.5% glycine, but hypo-osmolality does not occur with mannitol. Its use should lessen the risk of hyponatremic encephalopathy.