Blood moves from the feet and lower extremities by way of venous pumps, a one-way valve system, in normal physiology. When legs are moved or flexed, the muscular contraction forces blood in the veins up toward the torso. These one-way valves in the veins prevent that blood from flowing back down to the feet between contractions, like a friction hitch when ascending a rope. The next muscular movement continues to force the blood up the leg, resulting eventually in blood being “pumped” passively from the feet back up to the torso despite there obviously being no pump in the feet pushing it upward.
If one remains vertical and does not move the lower extremities at all, this passive venous pump system fails, and blood can pool in the lower extremities. Although no actual blood is lost, this causes a relative low-volume state in the core that mimics the shock from bleeding.
A climber hanging suspended vertically and immobile in a harness is in danger that nothing, including unconsciousness, will change his vertical position unless the climber is actively repositioned. It is common to pass out within minutes of being suspended in an immobile state. Unconsciousness can cause loss of breathing and death from asphyxiation or other consequences of shock, such as low oxygenation of the brain or of other vital organs due to the amount of blood taken out of functional circulation.
Numerous safety and standard-setting organizations have recognized this syndrome, which can occur within five to 30 minutes of being trapped in a vertical position. For industries using harnesses, the Occupational Safety and Health Administration in the United States requires “prompt” rescue as quickly as possible, noting that death can occur within 30 minutes. (OSHA; http://bit.ly/2ovBuaq.) Manufacturers of industrial personal protective equipment harnesses, citing suspension syndrome, recommend rescue within 15 minutes, and the American National Standards Institute recommends patient contact within four to six minutes and “prompt” rescue to follow. (Fallproof. Oct. 21, 2014; http://bit.ly/2ovChrU; Roco Rescue, http://bit.ly/2pnr2Fo).
Climbers trapped in a vertical suspended position should use an etrier (a webbing ladder) to reposition themselves periodically or a cordelette (basically a large sling), or other rope system to suspend the lower extremities. At the very least, periodic movements of the legs should be made when possible to stimulate the venous pump system in the lower extremities and ensure adequate blood return to the core.
A Debunked Myth
A mythical teaching has evolved among rescue personnel born out of the climbing and mountain medicine community, and its recent dispelling represents one of the greatest success stories of evidence-based medicine in wilderness medicine and the critical role of medical science and evidence-based medicine in climbing rescue education and operations.
The story behind the evolution of rescue personnel's misunderstanding of suspension syndrome began in 1972 at the second International Conference of Mountain Rescue Doctors in Innsbruck, Austria. (Wilderness Environ Med 2011;22:77.) A series of cases was analyzed where patients died after being taken off rope following prolonged suspension. Particularly puzzling were two otherwise unrelated cases — one caving and one mountaineering — in which the individuals were suspended for four hours but died within minutes of being taken off rope. It was hypothesized that these rescue deaths (also known as reperfusion syndrome, harness death, and harness pathology) were caused by blood returning too quickly to the core or by blood in the periphery collecting toxic contents that proved lethal when recirculated back to the heart after the patient was placed in a supine position. This hypothesis prompted a recommendation that a slow, gradual process be used to move suspended patients to a supine position and that harnesses be removed slowly, due to the belief that they contributed to the risk of death.
It prompted decades of teaching in climbing and mountain rescue communities that directly contraindicated common sense and standard practices in treating patients who are in shock and require urgent resuscitation: to lay them flat. Unfortunately, implementing practices based on hypothesis alone is not how medical science is supposed to work. The next step — testing the hypothesis — should be done before changes to practice are made. In subsequent testing, including by the presenters of the original hypothesis, no evidence could be found that this concept was valid. Nonetheless, the teaching persisted for years.
Roger B. Mortimer, MD, wrote the most compelling and comprehensive analysis of this error. (Wilderness Environ Med 2011;22:77.) He concluded that “this suggestion is not supported by the original series that demonstrated sudden deaths after rescue nor by modern understandings of physiology. Search-and-rescue teams and party members assisting a colleague suspended unconscious on rope should follow standard resuscitation measures to restore circulation to vital organs immediately.” Numerous other review articles have also come to similar conclusions. (Emerg Med J 2009;26:896; Norwich. UK: Health and Safety Executive 2009, http://bit.ly/2pnznZJ; Emerg Med J 2011;28:265; Wilderness Environ Med 2011;22:167.)
Scattered recommendations to orient a suspended climber into a supine position gradually still exist, and were still appearing in the Journal of Emergency Medical Services as late as 2009. (2009;34:44.) They are not, however, based on present-day evidence, and are steadily becoming increasingly rare or have corrected themselves, as the Journal of Emergency Medical Services did in 2015. (2015;40:48.)