Renal safety of CT angiography and perfusion imaging in the emergency evaluation of acute stroke

BACKGROUND AND PURPOSE: Multimodal CT imaging with contrast-enhanced CT angiography (CTA) and CT perfusion (CTP) is increasingly being used to guide emergency management of acute stroke. However, little has been reported about the safety of intravenous contrast administration associated with these studies in the acute stroke population, including cases in which baseline creatinine values are unknown. We investigated the incidence of contrast-induced nephropathy (CIN), defined as a 25% or more increase in baseline creatinine levels within 72 hours of contrast administration and chronic kidney disease in patients receiving CTA±CTP at our regional stroke center.MATERIALS AND METHODS: We analyzed 198 patients who underwent contrast CT studies for evaluation of acute ischemic or hemorrhagic stroke at our center (2003–2007). Through retrospective chart abstraction, we analyzed serial creatinine levels (baseline to day 3) and later values (≥day 4) where available. The incidences of CIN and/or chronic kidney disease were documented. After power analysis, CIN and non-CIN groups were compared by using the unpaired t test, Wilcoxon rank sum test, or Fisher exact test.RESULTS: None of the 198 patients developed chronic kidney disease or required dialysis. Of 175 patients with serial creatinine measurements between baseline and day 3, 5 (2.9%) developed CIN. The incidence of CIN was 2% in patients who were scanned before a baseline creatinine level was available.CONCLUSION: The incidence of renal sequelae is relatively low in acute stroke patients undergoing emergent multimodal CT scanning. Prompt CTA/CTP imaging of acute stroke, if indicated, need not be delayed in those with no history of renal impairment.

Multimodal CT scanning is increasingly being used to aid acute stroke diagnosis and management. Dynamic CT perfusion (CTP) differentiates thresholds of reversible and irreversible ischemia and, thus, helps to identify “tissue at risk” that is potentially salvageable with thrombolytic therapy.^1–4 CT angiography (CTA) allows for rapid noninvasive assessment of the intracranial and extracranial vasculature and identifies vessel occlusions or stenoses that may be amenable to acute treatment.^1–4 For intracerebral hemorrhage, CTA can identify secondary causes of hemorrhage, and, in the acute phase, the CTA “spot sign” can predict which hemorrhages are likely to expand.^5–7 Advantages of multimodal CT over MR imaging include its rapid accessibility, lower costs, shorter scanning time intervals, better patient tolerability, and higher spatial resolution.^8,9 Although it is not yet clear whether the information provided by multimodal CT improves stroke outcomes, the increasing use of these imaging methods warrants more thorough assessment of their safety profiles.Little has been reported regarding the safety of multimodal CT imaging in the acute setting. Because “time is brain” for acute stroke patients,¹⁰ some stroke centers perform such imaging immediately on patient arrival to the emergency department, often before the results of blood work (eg, creatinine) are available. The primary safety concern regarding contrast-enhanced CT is the potential development of contrast-induced nephropathy (CIN), defined as a 25% or more increase in baseline creatinine levels within 72 hours of contrast administration.^11,12 Some clinicians feel uneasy about ordering contrast studies given the potential for CIN and the difficulty in obtaining a reliable history of renal disease in acute stroke patients who are frequently incapacitated or unable to communicate. In patients with CIN, creatinine levels usually peak around days 2–3 and normalize within 2 weeks, but a small proportion go on to chronic renal failure and dialysis.^11,13 CIN has been associated with prolonged hospital stay, increased resource use, and a fivefold increase in mortality.^12,14,15This purpose of this study was to assess the renal safety of emergency multimodal CT scanning in acute stroke patients at a large regional stroke center, including those patients for whom the baseline creatinine level was not known.