Polyuria and cerebral vasospasm after aneurysmal subarachnoid hemorrhage.

BACKGROUND: Natriuresis with polyuria is common after aneurysmal subarachnoid hemorrhage (aSAH). Previous studies have shown an increased risk of symptomatic cerebral vasospasm or delayed cerebral ischemia (DCI) in patients with hyponatremia and/or the cerebral salt wasting syndrome (CSW). However, natriuresis may occur in the absence of hyponatremia or hypovolemia and it is not known whether the increase in DCI in patients with CSW is secondary to a concomitant hypovolemia or because the physiology that predisposes to natriuretic peptide release also predisposes to cerebral vasospasm. Therefore, we investigated whether polyuria per se was associated with vasospasm and whether a temporal relationship existed. METHODS: A retrospective review of patients with aSAH was performed. Exclusion criteria were admission more than 48 h after aneurysmal rupture, death within 5 days, and the development of diabetes insipidus or acute renal failure. Polyuria was defined as > 6 liters of urine in a 24 h period. Vasospasm was defined as a mean velocity > 120 m/s on Transcranial Doppler Ultrasonography (TCDs) or by evidence of vasospasm on computerized tomography (CT) or catheter angiography. Multivariable logistic regression was performed to assess the relationship between polyuria and vasospasm. RESULTS: 95 patients were included in the study. 51 had cerebral vasospasm and 63 met the definition of polyuria. Patients with polyuria were significantly more likely to have vasospasm (OR 4.301, 95% CI 1.378-13.419) in multivariate analysis. Polyuria was more common in younger patients (52 vs 68, p <.001) but did not impact mortality after controlling for age and disease severity. The timing of the development of polyuria was clustered around the diagnosis of vasospasm and patients with polyuria developed vasospasm faster than those without polyuria. CONCLUSIONS: Polyuria is common after aSAH and is significantly associated with cerebral vasospasm. The development of polyuria may be temporally related to the development of vasospasm. An increase in urine volume may be a useful clinical predictor of patients at risk for vasospasm.

Augmented Renal Clearance in Patients with Subarachnoid Hemorrhage.

BACKGROUND: Patients with subarachnoid hemorrhage (SAH) typically exhibit hyperdynamic cardiovascular hemodynamics, which may lead to increased medication clearance. The aims of this study were to evaluate the actual creatinine clearance (CrClA) in an aneurysmal SAH population and the effect of the development of cerebral vasospasm (CV) along with its treatment to better understand if this population exhibits augmented renal clearance (ARC). METHODS: This was a prospective, single-center study in a neurosciences ICU at a university hospital. A total of 20 patients were consented and provided a 24-h urine sample to measure the CrClA. If patients experienced CV, a 24-h urine collection was repeated during vasospasm treatment. CrClA was measured using a modified Jaffe assay. RESULTS: Among the 20 patients enrolled, the mean SAH CrClA was 325.93 ± 135.20 ml/min 1.73 m(2) and this differed significantly from the SAH estimated creatinine clearance (CrClE) 144.93 ± 42.82 ml/min 1.73 m(2) (p < 0.001). Four patients developed CV; the mean CV CrClA was 558.43 ± 356.12 ml/min 1.73 m(2) and there was no significant difference when compared to those patients' mean SAH CrClA (246.91 ± 84.14 ml/min 1.73 m(2), p = 0.16). CONCLUSIONS: ARC was present in 100 % of the patients with recent SAH enrolled. Although ARC remained present in the patients who experienced CV, their creatinine clearance was not significantly further augmented. Further work is needed to clarify the impact of such clearances on renally excreted medications and how the development and treatment of CV further augment these findings.

Cerebral salt wasting in subarachnoid hemorrhage rats: model, mechanism, and tool.

Cerebral salt wasting (CSW) frequently occurs concomitantly with aneurysmal subarachnoid hemorrhage (SAH). CSW induces excessive natriuresis and osmotic diuresis, and reduces total blood volume. As a result, the risk of symptomatic cerebral vasospasm may be elevated. Therefore, it is important to determine the mechanism of CSW. The purpose of this study was to evaluate whether the rat SAH model exhibits CSW and to investigate the relationship between CSW and natriuretic peptides. A SAH model was produced in 24 rats by perforating a cerebral artery with a nylon thread up through the common carotid artery. To evaluate CSW, urine was cumulatively collected from SAH onset to 12 hours and sodium (Na) excretion was analyzed. Body weight and hematocrit were analyzed before and after SAH onset. Concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in plasma were also analyzed. Urine volume and total Na excretion of SAH rats were significantly higher than those of sham rats (p<0.05). Body weight of SAH rats significantly decreased and hematocrit significantly increased (p < 0.05). ANP concentration was significantly decreased in SAH rats (p<0.05). However, BNP concentrations did not change. This study demonstrated for the first time that a rat SAH model exhibited CSW. It was suggested that the cause of CSW was neither ANP nor BNP. In addition, this rat SAH model will be useful for study of CSW after SAH.