Blood pressure, fatigue, and the pathogenesis of aneurysmal subarachnoid hemorrhage

Prognostic value of premorbid hypertension and neurological status in aneurysmal subarachnoid hemorrhage: pooled analyses of individual patient data in the SAHIT repository

OBJECT

The literature has conflicting reports about the prognostic value of premorbid hypertension and neurological status in aneurysmal subarachnoid hemorrhage (SAH). The aim of this study was to investigate the prognostic value of premorbid hypertension and neurological status in the SAH International Trialists repository.

METHODS

Patient-level meta-analyses were conducted to investigate univariate associations between premorbid hypertension (6 studies; n = 7249), admission neurological status measured on the World Federation of Neurosurgical Societies (WFNS) scale (10 studies; n = 10,869), and 3-month Glasgow Outcome Scale (GOS) score. Multivariable analyses were performed to sequentially adjust for the effects of age, CT clot burden, aneurysm location, aneurysm size, and modality of aneurysm repair. Prognostic associations were estimated across the ordered categories of the GOS using proportional odds models. Nagelkerke's R(2) statistic was used to quantify the added prognostic value of hypertension and neurological status beyond those of the adjustment factors.

RESULTS

Premorbid hypertension was independently associated with poor outcome, with an unadjusted pooled odds ratio (OR) of 1.73 (95% confidence interval [CI] 1.50-2.00) and an adjusted OR of 1.38 (95% CI 1.25-1.53). Patients with a premorbid history of hypertension had higher rates of cardiovascular and renal comorbidities, poorer neurological status (p ≤ 0.001), and higher odds of neurological complications including cerebral infarctions, hydrocephalus, rebleeding, and delayed ischemic neurological deficits. Worsening neurological status was strongly independently associated with poor outcome, including WFNS Grades II (OR 1.85, 95% CI 1.68-2.03), III (OR 3.85, 95% CI 3.32-4.47), IV (OR 5.58, 95% CI 4.91-6.35), and V (OR 14.18, 95% CI 12.20-16.49). Neurological status had substantial added predictive value greater than the combined value of other prognostic factors (R(2) increase > 10%), while the added predictive value of hypertension was marginal (R(2) increase < 0.5%).

CONCLUSIONS

This study confirmed the strong prognostic effect of neurological status as measured on the WFNS scale and the independent but weak prognostic effect of premorbid hypertension. The effect of premorbid hypertension could involve multifactorial mechanisms, including an increase in the severity of initial bleeding, the rate of comorbid events, and neurological complications.

Physical factors effecting cerebral aneurysm pathophysiology

Many factors that are either blood-, wall-, or hemodynamics-borne have been associated with the initiation, growth, and rupture of intracranial aneurysms. The distribution of cerebral aneurysms around the bifurcations of the circle of Willis has provided the impetus for numerous studies trying to link hemodynamic factors (flow impingement, pressure, and/or wall shear stress) to aneurysm pathophysiology. The focus of this review is to provide a broad overview of such hemodynamic associations as well as the subsumed aspects of vascular anatomy and wall structure. Hemodynamic factors seem to be correlated to the distribution of aneurysms on the intracranial arterial tree and complex, slow flow patterns seem to be associated with aneurysm growth and rupture. However, both the prevalence of aneurysms in the general population and the incidence of ruptures in the aneurysm population are extremely low. This suggests that hemodynamic factors and purely mechanical explanations by themselves may serve as necessary, but never as necessary and sufficient conditions of this disease's causation. The ultimate cause is not yet known, but it is likely an additive or multiplicative effect of a handful of biochemical and biomechanical factors.

Dependence of subarachnoid hemorrhage on climate conditions: a systematic meteorological analysis from the dusseldorf metropolitan area

OBJECTIVE

A number of publications suggest that there are seasonal influences on the incidence of subarachnoid hemorrhage (SAH). Most series agree on a peak incidence during springtime. Meteorological influences have been assumed to be obvious explanations for seasonal variations. Furthermore, the perceived clustering of the incidence of subarachnoid hemorrhage is also intuitively related to meteorological influences. The present study was initiated to determine whether specific meteorological conditions are related to the occurrence of SAH in the mild climatic zone of North Rhine Westphalia.

METHODS

We retrospectively examined 183 patients (107 women and 76 men) treated at our department between January 2003 and June 2005 for SAH that had occurred within the Düsseldorf metropolitan area. We correlated the date of SAH (Day 0) and of the week preceding the incident (Days -1, -3, -5, and -7) with the meteorological key parameters from Düsseldorf International Airport. Parameters analyzed were mean daily temperature (7C), relative humidity (%), barometric pressure (hPa), and weather condition (divided into 6 groups: clear, cloudy, rain, thunderstorms, snow, and not available).

RESULTS

A relative peak incidence of SAH was found for the month of April. In addition, a diurnal rhythm with two peaks during morning and in the evening, and a statistically significant nadir during forenoon and midday was evident (P <0.002). None of the average meteorological key parameters of the day of SAH differed from the annual average, and no general trends during the days preceding hemorrhage could be identified. Apparent clustering of the occurrence of SAH could not be related to short-term meteorological trends.

CONCLUSION

The results of the present study demonstrate a trend toward a seasonal distribution in the incidence of SAH with a peak during spring in the metropolitan area of Düsseldorf. Furthermore, weather variables, such as temperature, barometric pressure, and humidity, were shown to be without influence on aneurysm rupture within the patient population. Therefore, the result indicates the need to validate further parameters in detail to isolate risk circumstances to achieve a risk pattern for patients with SAH.