Prehospital and Disaster Medicine

Original Research

Design of a Model to Predict Surge Capacity Bottlenecks for Burn Mass Casualties at a Large Academic Medical Center

Mahshid Abira1 c1, Matthew M. Davisa2, Pratap Sankara3, Andrew C. Wonga4 and Stewart C. Wanga5

a1 Department of Emergency Medicine, University of Michigan, Ann Arbor, Michigan USA. Dr. Abir is now with the Department of Emergency Medicine, George Washington University, Washington, DC USA and Rand Corporation, Arlington, Virginia USA

a2 Department of Internal Medicine, Department of Pediatrics and the Robert Woods Johnson Foundation Clinical Scholars Program, University of Michigan, Ann Arbor, Michigan USA

a3 TRW Automotive, East Lansing, Michigan USA

a4 Department of Emergency Medicine, University of California, Irvine, Irvine, California USA

a5 Department of Surgery, University of Michigan, Ann Arbor, Michigan USA


Objectives To design and test a model to predict surge capacity bottlenecks at a large academic medical center in response to a mass-casualty incident (MCI) involving multiple burn victims.

Methods Using the simulation software ProModel, a model of patient flow and anticipated resource use, according to principles of disaster management, was developed based upon historical data from the University Hospital of the University of Michigan Health System. Model inputs included: (a) age and weight distribution for casualties, and distribution of size and depth of burns; (b) rate of arrival of casualties to the hospital, and triage to ward or critical care settings; (c) eligibility for early discharge of non-MCI inpatients at time of MCI; (d) baseline occupancy of intensive care unit (ICU), surgical step-down, and ward; (e) staff availability—number of physicians, nurses, and respiratory therapists, and the expected ratio of each group to patients; (f) floor and operating room resources—anticipating the need for mechanical ventilators, burn care and surgical resources, blood products, and intravenous fluids; (g) average hospital length of stay and mortality rate for patients with inhalation injury and different size burns; and (h) average number of times that different size burns undergo surgery. Key model outputs include time to bottleneck for each limiting resource and average waiting time to hospital bed availability.

Results Given base-case model assumptions (including 100 mass casualties with an inter-arrival rate to the hospital of one patient every three minutes), hospital utilization is constrained within the first 120 minutes to 21 casualties, due to the limited number of beds. The first bottleneck is attributable to exhausting critical care beds, followed by floor beds. Given this limitation in number of patients, the temporal order of the ensuing bottlenecks is as follows: Lactated Ringer's solution (4 h), silver sulfadiazine/Silvadene (6 h), albumin (48 h), thrombin topical (72 h), type AB packed red blood cells (76 h), silver dressing/Acticoat (100 h), bismuth tribromophenate/Xeroform (102 h), and gauze bandage rolls/Kerlix (168 h). The following items do not precipitate a bottleneck: ventilators, topical epinephrine, staplers, foams, antimicrobial non-adherent dressing/Telfa types A, B, or O blood. Nurse, respiratory therapist, and physician staffing does not induce bottlenecks.

Conclusions This model, and similar models for non-burn-related MCIs, can serve as a real-time estimation and management tool for hospital capacity in the setting of MCIs, and can inform supply decision support for disaster management.

M Abir, MM Davis, P Sankar, AC Wong, SC Wang. Design of a model to predict surge capacity bottlenecks for burn mass casualties at a large academic medical center. Prehosp Disaster Med. 2013;28(1):1-10.

(Received February 07 2011)

(Accepted May 09 2011)

(Revised May 17 2011)

(Online publication October 23 2012)


  • burns;
  • disaster;
  • emergency medicine;
  • mass-casualty incident;
  • model;
  • simulation;
  • surge;
  • surge capacity


  • %TBSA:percent total body surface area;
  • AHRQ:Agency for Healthcare Research and Quality;
  • ED:emergency department;
  • ICU:intensive care unit;
  • MCI:mass-casualty incident;
  • NBR:National Burn Repository;
  • SEMLES:Seamless Emergency Medical Logistics Expansion System


c1 Correspondence: Mahshid Abir, MD, MSc Rand Corporation 1200 South Hayes Street Arlington, VA 22202 USA E-mail