Klein, K., Rosenthal, M., Klausner, H. (2005). Blackout 2003: Preparedness and Lessons Learned from the Perspectives of Four Hospitals. Prehospital and Disaster Medicine. 20(5):343-49.
The authors reviewed after-action reports from four hospitals that experienced loss of power (and in two cities, water supply). They found that many issues landing or keeping patients in the hospital were social/resource rather than medical, which is consistent with more recent disasters (e.g., Hurricane Sandy).