Harness Suspension Trauma – Is it a real threat?

Harness suspension trauma, also known as Orthostatic Intolerance, suspension syndrome or harness-induced pathology has long been thought to cause loss of consciousness, and other injuries to a worker or rescuer who has suspended in midair by a harness. But is this phenomenon really as big of threat as we commonly believe?

Suspension Pathophysiology

Due to the nature of harness, and a worker’s orientation after a fall onto the fall arrest system, the following is presumed to occur:

1. Decrease blood return from lower extremities, muscle venous pump decreases, and blood collects in lower limbs with extracellular fluid shift
2. Increase in metabolic waste, and acidotic blood in the legs
3. Decreased Cardiac output, possible anxiety, and onset of volume shock, with possible cardiac irritability
4. Reduced heart rate and blood pressure, associated with vagal mediated syncope
5. Loss of Consciousness cardiac arrest / death

Historical Context

In the early 1970’s, a series of case reports emerged, describing seemingly uninjured climbers who died after they were suspend in their harnesses for various times, ranging from 90 minutes to 8 hours. Trauma could not explain the deaths. Some climbers had died while suspended, and in one worrisome case, the victim died immediately after rescue. Some speakers at the 1972 International Conference of Mountain Rescue Doctors in Innsbruck, Austria attempted to explain the deaths and made recommendations for prevention. They recommended against placing a victim supine “abruptly” after rescue, although they did not define “abruptly.” These recommendations were buried in obscurity for 3 decades. 

From the mid 1980’s, to early 1990’s, two noteworthy studies were conducted.

• One studied participants who were hanging passively in a harness. 2 of the 10 participants showed significant decrease in blood pressure. 
• The French Federation of Speleology had subjects hang passively in a harness.  The first two subjects loss consciousness at the 7 and 30 minute point.  The study was modified and repeated — the first participant loss consciousness after 6 minutes.  No further trials were conducted.

During the 2000’s, Health and Safety Executive of United Kingdom published treatment standard: “the accident victim must never be laid down”. OSHA stated that any person suspended for over 30 minutes had a “significant increase” in mortality. As well, in 2004, an OSHA and Health bulletin on Suspension Trauma/ Orthostatic Intolerance stated, “Be aware that some authorities advise against moving the rescue worker to a horizontal position too quickly”.

In 2011, Pasquier et al publish clinical review, debunking “don’t lie patient down” mantra. 

Recent Laboratory Studies

Summary of Recent Studies 

One important point to note is that is that all of the current research is a result of laboratory studies only. There is good laboratory evidence that physiological changes occur with passive suspension, however, we must ask the question of Correlation VS Causality. Both studies identify “Syncope” in 10 to 30% of subjects, and onsets as early as 10 minutes with mean time around 30 minutes. However different attribution – vagal mechanism VS cerebral hypoxia. 

So, laboratory studies clearly indicate that something happens to a large number of people when they hang motionless in a harness. The Harness design and attachment point itself also has an influence. The limitations of this research should also be mentioned. These results were from a small number of laboratory Studies only. To date, no higher quality evidence exists. 

With no other evidence to turn to, the research shifted to real world documented cases. 

Statistical Analysis

Incident Rates and Frequency

In reviewing reports from databases across North America, and Europe, over the past 5 years, there is only one possible death related to suspension in a harness. However, there is insufficient information to attribute conclusively this reported death to suspension related trauma. Based on these statistics, it is safe to say that suspension trauma is an extremely rare event and uncommon event in real life.

Raven Recommended Treatment Guidelines

Looking through the lens of rescue medicine, the following treatment guidelines should be considered for anyone hanging in a harness.

Conscious Patient Suspend in Harness (Normothermic) 

• Encourage person to move.
• If possible, position in a sitting position. 
• Rescue promptly if no signs of syncope no further treatment required.

Supporting Evidence:

No Direct evidence, inferred expert opinion only.

• Laboratory studies instructed subject to hang passively and not to move. Resulting in 10-30% Syncope. No study of the impact of movement on onset of syncope.
• Harness pressure study demonstrated that a sitting position exerts the least amount of pressure in groin area.

Conscious Patient Suspend in Harness (Hypothermic)

• Place person in horizontal position as soon as possible.
• Gentle Handling
• Treat for hypothermia – Super Insulate and support spontaneous rewarming.  
• If no signs of syncope and patient rewarms spontaneously, no further treatment required.

Supporting Evidence:

No Direct evidence, inferred expert opinion only.

• Laboratory studies instructed subject to hang passively and not to move. Resulting in 10-30% Syncope. No study of the impact of movement on onset of syncope.

Unconscious Patient Suspended in Harness

Rescue Phase

• Execute rescue plan and get patient to ground or safety ASAP
• It is more important to extricate than to delay extrication in an attempt to move patient into a horizontal position before rescue except in case of hypothermic patient then move to horizontal position early in the rescue 

Supporting Evidence:

• Normothermic – Laboratory evidence, expert opinion
• Hypothermic — Good case study evidence on the importance of horizontal position for hypothermic.

Immediate First Aid Phase

• Place patient supine and provide standard care. Follow normal treatment guidelines at your level of care for whatever injuries found.  Closely monitor ABC’s and vital signs and anticipate a dynamic patient that could change.  If hypothermic, be cautious of a potential post rescue collapse.

Medical Treatment Phase

• Symptom based treatment based on standard medical care guidelines.  For any patient suspended for more that 90 minutes consider monitoring 24 to 36 hours for delay onset complication due to muscle hypoxia e.g., Rhabdomyolysis. 

Supporting Evidence:

• No Direct evidence, inferred expert opinion only
• Treatment recommendations based on physiologically similar conditions

Conclusion

From looking at recent laboratory studies, as well as recent statistics, we can conclude that suspension trauma as we previously viewed it, is not a significant threat to workers or rescuers as once was thought to be. This is in part to changes in harness technology, rope construction, and fall arrest devices. Although further research is required to obtain higher quality evidence such as Random Control Trials and Meta Analysis, the existing evidence points to treatment guidelines that follow existing best practices. 

Sources

Patrizio Petrone, et al 2021

Fatal and non-fatal injuries due to suspension trauma syndrome: A systematic review of definitions, pathophysiology, and management controversies

World Journal of Emergency Medicine, 2021; 12(4) 253-260

Weber, S.A. et al (June 08, 2020)

Suspension Trauma:  A Clinical Review

Cureus 12(6): e8514 DOI 10.7759/cureus.8515

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Len James

Len has been teaching wilderness medical programs since the mid 1980’s. Len has taught course in 10 countries around the world. From “north of 60” and South America, to teaching the first wilderness medical program in China, he enjoys adopting medical training programs to meet the needs of diverse students.