Canadian Journal of Anaesthesia

, Volume 34, Issue 5, pp 442–446 | Cite as

The effect of high-dose mannitol on serum and urine electrolytes and osmolality in neurosurgical patients

  • Pirjo H. Manninen
  • Arthur M. Lam
  • Adrian W. Gelb
  • Stephen C. Brown


The effect of mannitol on serum and urine electrolytes and osmolality was investigated intraoperatively in neurosurgical patients. Patients in Group A (n = 7) received 1 gm·kg-1 of 20 per cent mannitol (“low”-dose) and in Group B, (n = 7) 2 gm·kg-1 (“high”-dose). There was a significant decrease in serum sodium and bicarbonate, and a significant increase in serum osmolality in both groups after mannitol administration. The decrease in serum sodium and the increase in serum osmolality were significantly greater in patients receiving the larger dose of mannitol. The infusion of low-dose mannitol resulted in a slight decrease in serum potassium, in contrast, after highdose mannitol there was a significant rise in serum potassium reaching a maximum mean increase of 1 .5 mmolľ1-1. Urine electrolyte concentration and osmolality showed a similar decrease in both groups. The significant changes that occurred with the administration of mannitol were of short duration in these patients with normal cardiac and renal function. The clinically most important change is the increase in serum potassium with high-dose manitol. The exact mechanism of this increase remains unclear.

Key words

anaesthesia: neurosurgical pharmacology: mannitol fluid balance: electrolytes. 


On a examiné ľeffet du mannitol sur les électrolytes et ľosmotalité sériques et urinaires en période intraopératoire chez les patients neurochirurgicaux. Les patients du groupe A (n = 7) ont reçu 1 g·kg-1 de 20 pour cent de mannitol (“faible” dose) et ceux du groupe B (n = 7), ont reçu 2 g·kg-1 (dose “élevée”). Une diminution significative du sodium et du bicarbonnate sêrique, et une augmentation significative de ľosmolalité sêrique s’est produite dans les deux groupes après ľadministration du mannitol. La diminution du sodium sêrique et ľaugmentation de V osmolalité sêrique étaient beaucoup plus élevées chez les patients recevant une dose importante de mannitol. Ľinfusion ďune faible dose de mannitol a entraîné une légère diminution du potassium sêrique. Par contre, après ľadministration ďune dose élevée de mannitol, le potassium sêrique a augmenté de façon significative atteignant une augmentation maximum moyenne de 1.5 mmol·L-1. La concentration électrolytique et ľosmolalité urinaire ont démontré une diminution semblable dans les deux groupes. Les changements significatifs qui se sont produits avec ľadministration de mannitol étaient de courte durée chez les patients ayant une fonction cardiaque et une fonction rénale normales. Le changement clinique le plus important est ľaugmentation du potassium sêrique en présence ďune dose élevée de mannitol. On ne comprend pas encore clairement le mécanisme exact de cette augmentation.


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Copyright information

© Canadian Anesthesiologists 1987

Authors and Affiliations

  • Pirjo H. Manninen
    • 1
  • Arthur M. Lam
    • 1
  • Adrian W. Gelb
    • 1
  • Stephen C. Brown
    • 1
  1. 1.Department of AnaesthesiaUniversity HospitalLondonCanada

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