Abstract Presentations at the 2005 Wilderness Medical Society Meeting, Snowmass,
Colorado, July 23 to 27, 2005
Oral Presentation
The Effects of Mechanical Stimulation on Cardiac Rhythm in a Hypothermic Swine
Model
James M Grueskin, MD
1
, Pam Harvey, DO
2
, Frank Dos Santos, DO
2
, William H
Richardson, MD
3
, and Dave A Tanen, MD
2
1
Naval Hospital Great Lakes, Great Lakes, Illinois
2
Naval Medical Center San Diego, San Diego, California
3
University of California San Diego, San Diego, California
Introduction: Hypothermia is a frequent complication of cold weather exposure and/or
wilderness injuries. Anecdotal reports have postulated that patients suffering from acute
hypothermia are at significantly increased risk of developing lethal cardiac dysrhythmias
secondary to the physical stimulation from moving and transporting patients.
Objective: To determine the ability of rough handling and sudden movement to induce
lethal cardiac dysrhythmias in a controlled animal study of mild to severe hypothermia.
Methods: Ten anesthetized swine had continuous cardiac and invasive BP monitoring.
Core body temperature (CBT) was measured with an esophageal probe. Animals were
secured to a backboard in a supine position for the duration of the study and their CBT
was serially lowered by external cooling measures. At preset intervals (every 3
°C
lowered from the baseline CBT of 38
°C) the animals were lifted via the backboard and
rolled 90 degrees to the left and held for 5 seconds, brought back to horizontal and then
rolled to the right and held for 5 seconds. After rolling, the swine were lifted via the
backboard 6 inches off the OR table and dropped back onto the table, 15 seconds later
this was repeated at 12 inches. If no signs of arrhythmia were noted, external cooling was
continued.
Results: 2/10 (20%) swine developed fatal arrhythmias (V-fib) during mechanical
stimulation but not until CBT was 20
°C. Fifty percent (5/10) of the animals developed
fatal arrhythmias (3 V-fib, 2 asystole) with no stimulation but at CBT 25
°C (average
CBT 22.7
°C). No animal developed a dysrhythmia at a CBT > 25°C with or without
stimulation.
Conclusion: Severe hypothermia induces fatal dysrhythmias. Mechanical stimulation in
animals with severe hypothermia may contribute to the induction of fatal arrhythmias.
