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Winning Abstracts from the 2011 Medical Student Abstract Competition: Atropine Prophylaxis a Risk Factor for Post-Carotid Artery Stenting Hypotension

Author: Richard J. VanDam, Wayne State University School of Medicine, Class of 2011

Introduction: Hemodynamic Depression (HD) is a worrisome complication following Carotid Artery Stenting (CAS). Prophylactic atropine helps mitigate the risk of post-stent bradycardia. We assessed the hypothesis that pre-operative systolic BP and prophylactic atropine use are predictive for post-CAS HD.

Methods: Using a single-center prospective CAS registry, we retrospectively reviewed Electronic Medical Records of 109 patients (mean age 72 10 years; 68% men) receiving successful CAS between December, 2008 and October, 2010. Of these, 45 patients received prophylactic atropine intra-operatively prior to CAS deployment. Post-CAS HD was defined as symptomatic or asymptomatic hypotension (SBP < 90 mmHg or drop >40%), bradycardia (HR < 60 bpm or drop > 20%), or intra-operative need for vasopressors or anticholinergics post-CAS as surrogate end-points for hypotension and bradycardia respectively. Statistical significance was determined using Student t-test (mean SEM) or ?2 for categorical variables (% incidence) and 95% CI.

Results: Mean SBP decreased from baseline following CAS deployment (1562 to 1253, p < 0.001, n=109) with a small increase in mean HR (70+1 to 721, p=0.03, n=109). The incidence of post-CAS hypotension (n=24), bradycardia (n=38), and both (n=12) was 22%, 35%, and 11% respectively. Drug intervention with either atropine (n=20), dopamine (n=16), or both (n=6) was required in 42 patients for post-CAS HD. Prophylactic atropine was associated with decreased incidence of post-CAS bradycardia (29% vs. 58%, p < 0.01) but increased incidence of hypotension (49% vs. 22%, p < 0.01), leading to no net benefit in preventing HD (73% vs. 64%, p=0.31). While pre-procedural hypertension (SBP=140 mmHg, n=54 of 109) was not predictive of HD overall (p=0.12), it was a risk factor among atropine-treated patients for post-CAS hypotension (65% vs. 25%, p < 0.01) but not bradycardia (p=0.38). Conclusion: In conclusion, atropine prophylaxis carried an increased risk of post-CAS hypotension. While atropine mitigates the risk of post-CAS bradycardia, the concomitant prophylactic use of vasopressors may be warranted to offset the increased risk of hypotension- particularly in patients presenting with elevated SBP immediately prior to the procedure.

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