Extending tissue plasminogen activator use to community and rural stroke patients.

BACKGROUND AND PURPOSE: Guidelines for intravenous tissue plasminogen activator (tPA) use in stroke emphasize the importance of limiting its use to facilities with imaging capabilities and stroke expertise. This prospective case series set out to evaluate the safety of tPA use in patients referred from rural communities to a tertiary center. METHODS: Prospective data of 82 consecutive patients treated with tPA in London, Ontario, were reviewed. RESULTS: Twenty-three patients were transferred to London from a rural hospital (non-London patients); 49 were first evaluated in a London emergency room (London ER); and 10 were inpatients in a London hospital at the time of stroke onset. Mean transfer time and distance to London for non-London patients were 89 minutes and 41 miles. Although symptom onset to London ER times were longer for non-London than for London ER patients (123 versus 53 minutes), the door to needle times were significantly shorter for the former (49 versus 95 minutes, P<0.005). Imaging to needle times were longer for London inpatients compared with London ER patients (55 versus 36 minutes, P=0.16). The proportion of patients with >4-point improvement on the NIH Stroke Scale or cure at 24 hours was 57%, with no difference among groups (P=0.46). The overall symptomatic hemorrhage rate at 36 hours was 2%. No significant differences in outcomes were observed at 3 months. CONCLUSIONS: This prospective study suggests that it is feasible and safe to treat rural patients referred to a tertiary care center with tPA, thus extending the benefits of thrombolysis for acute stroke to a wider population.

Relating drug-induced changes in carotid artery mechanics to cardiovagal and sympathetic baroreflex control.

Previous evidence indicates that sensitivity of the baroreflex cardiovagal and sympathetic arms is dissociated. In addition, pharmacologic assessment of baroreflex sensitivity (BRS) has revealed that cardiovagal, but not sympathetic, BRS is greater when blood pressure is increasing versus falling. The origin of this hysteresis is unknown. In this study, carotid artery distensibility and absolute distension (diameter) were assessed to test the hypothesis that vessel mechanics in barosensitive regions affect the BRS of cardiovagal, but not sympathetic, outflow. R-R interval (i.e. time between successive R waves), finger arterial blood pressure, muscle sympathetic nerve activity, and carotid artery dimensions (B-mode imaging) were measured during sequential infusions of sodium nitroprusside (SNP) and phenylephrine (PHE). Systolic and diastolic common carotid artery diameters and pulse pressure were recorded to calculate distensibility of this vessel under each drug condition. Cardiovagal BRS was greater when blood pressure was increasing versus decreasing (p < 0.01). Sympathetic BRS was not affected by direction of pressure change. Distensibility did not differ between SNP and PHE injections. However, compared with SNP, infusion of PHE resulted in larger absolute systolic and diastolic carotid diameters (p < 0.001). Therefore, cardiovagal reflex hysteresis was related to drug-induced changes in common carotid artery diameter but not distensibility. The lack of sympathetic hysteresis in this model suggests a relative insensitivity of this baroreflex component to carotid artery dimensions and provides a possible mechanism for the dissociation between cardiovagal and sympathetic BRS.