We retrospectively analyzed the medical records of all patients who were treated with IV tPA within 4.5 hours of symptom onset in the ED, at Johns Hopkins Hospital or Bayview Medical Center, between January 2010 and March 2013. Patients with in-hospital strokes and patients who were subsequently transferred to or from other hospitals after tPA administration were excluded. Demographic data including age, sex, and race were collected for all patients. The presence of stroke risk factors including hypertension, hyperlipidemia, diabetes mellitus, smoking status, history of atrial fibrillation, and prior history of stroke, as well as the pre-hospital use of antiplatelet agents, anticoagulation, and statins were also recorded. National Institutes of Health Stroke Scale (NIHSS) is a standardized and easy to obtain tool used by providers and researchers in order to quantify stroke severity [7] (link), [8] (link). Possible values on the NIHSS range from 0 to 42, higher values indicating increased stroke severity. NIHSS and the following physiologic parameters at presentation were recorded: blood pressure, international normalized ratio (INR), and estimated glomerular filtration rate (eGFR) by Modification of Diet in Renal Disease (MDRD) equation. The most likely stroke localization (anterior vs. posterior circulation) was recorded based on the patient's presenting symptoms.
The primary outcome was the need for a critical care intervention at any time point from the end of tPA infusion until transfer from the ICU to the floor. A critical care intervention was considered any therapy or intervention that required ICU resources, as defined previously [9] (link), [10] (link). Specifically, ICU admission criteria included: uncontrolled hypertension requiring titration of IV antihypertensives, use of vasopressors either for symptomatic systemic hypotension or blood pressure augmentation, need for invasive hemodynamic monitoring, uncontrolled hyperglycemia requiring IV Insulin, respiratory compromise resulting in either initiation of bilevel positive airway pressure (BiPAP) or mechanical ventilation, arterial bleeding, management of cerebral edema and increased ICP, neurosurgical intervention such as decompressive craniectomy, or interventional angiography with or without intervention. Our definition of an ICU intervention also included patients with any event or complication that would require monitoring in an ICU setting even if no immediate ICU intervention was performed, such as progressive decrease in mental status with impaired airway protection, increasing oxygen requirement, or detection of potentially life-threatening arrhythmia. Patients who required ICU resources by the end of their tPA infusion or at any time over the next 24 hours were compared with those patients who did not have an ICU intervention during the same time period.