Suspension Induced Shock Syndrome

Terminology and similar conditions

Also known as:

• Suspension trauma (even though there is no "trauma" involved)
• Harness induced pathology

Similarities / related to:

• Collapse / death during rescue of hypothermic victims
• Collapse / death during helicopter winching in the vertical position
• Rewarming shock (hypothermic victims)

All of which are forms of:

• Rescue associated collapse
• Other related conditions
• Collapse due to exercise induced heat exhaustion
• Parade ground collapse / fainting

Causes and effects

All of these conditions have a similar result: The victim suddenly collapses, loses consciousness and may have a cardiac arrest. In all cases, the final physiological mechanism causing the collapse is the same. There is not enough blood flow and/or blood pressure in the region of the heart and brain and consciousness is therefore lost. This is, in effect, a special form of sudden onset circulatory shock. The condition is often fatal, either because the low blood flow triggers a cardiac arrest or because the patient's airway becomes obstructed.

If the victim is vertical (the usual situation) and remains vertical, then resuscitation is often impossible. Conversely, if the victim can be quickly laid horizontal, the blood flow to the brain and heart improves and, if cardiac arrest has not occurred, recovery is usually fairly prompt, unless the shock situation has been prolonged.

Some of the most frequent reports of this condition relevant to HART operations involve cavers and canyoners who have lost consciousness and died in their harnesses, when either hanging stationary for a prolonged time on a belay or when entangled, or shortly after stopping to rest during a long prussik. Victims have often (but not always) been cold and exhausted.

The other situation to be especially aware of is vertical hoisting of a patient who is cold, exhausted, shocked or injured. Collapse, unconsciousness and cardiac arrest have occurred during vertical hoist in either a paraguard or similar stretcher or by a helicopter or shipboard strop under the patient's arms. In several cases, the patient was conscious and able to wave whilst floating in the water but had lost consciousness or died by the time they reached the top of the hoist.

Blood flows normally around the body when the three major factors which apply in all fluid circulation systems are balanced - the pump (the heart) is pumping adequately, there is enough fluid (blood) in the pipes and pump and the pipes are the right size, not leaky and not too stretchy. Normally, blood does not pool too much in the legs because the leg blood vessels constrict and, whilst leg muscles are tensed, this assists to "pump" the blood back uphill to the heart. The pressure and flow of blood reaching the brain will fall if there is not enough blood to fill the blood vessels, if the blood vessels are relaxed and stretch, allowing blood to pool in the legs or if the heart beats too weakly.

When a similar situation occurs following prolonged standing on a parade ground, fainting tends to cure itself. Once the person is lying down, blood circulates easily to the brain and heart because the whole body is on one level. In a harness on a rope, this will not usually be possible and brain damage or cardiac arrest follows. If the brain is starved of blood, it often reacts by triggering an extreme stress reaction, which can result in a brief period of very high blood pressure, triggering a cardiac arrest via another mechanism.

Risk Factors for Suspension Induced Shock Syndrome

• Sweating and lack of fluid intake cause dehydration.
• Cold exposure or immersion causes a "diuresis" (passing excess urine) which leads to relative dehydration.
• Blood loss
• Immobility means the leg muscle "pump" does not work.
• Muscle relaxation and heat allow stretching of leg blood vessels creating room for blood to pool in the legs.
• Prolonged cold can paralyse blood vessels and slow muscle reactions, resulting in the same effect.
• Some harnesses may restrict blood flow from the legs, back to the heart.
• When the person is exhausted and cold, and especially if they have been exerting themselves vigorously prior to the incident, the acidity and saltiness of the blood will be abnormal and the heart will be more "twitchy" and at risk of cardiac arrest.
• If there has been significant trauma (e.g. a major fall) there may be some element of crush injury to complicate things.
• If a patient is supported by a chest harness, simple waist loop only or strop under the arms, this will severely impair breathing and the respiratory muscles become tired and may fail ("Crucifixion syndrome"). This can occur together with suspension induced shock and will make things much worse.

Signs and Symptoms

• Sudden collapse (can occur without warning)
• Faintness, nausea, hot flushes, sweats, breathlessness, feeling of panic or unwellness, change in pulse rate (suddenly slowing or becoming rapid) - these may be warning signs which can be followed by collapse shortly after

Preventing Suspension Induced Shock Syndrome

Rescuers:

• Take adequate fluids
• Keep warm but avoid excess sweating and heat exhaustion
• Recover before a long prussik or other vigorous exertion
• Do not push yourself to the point of exhaustion - especially on long prussiks
• Avoid prolonged stationary suspension in a harness - take turns at the job, consider a bosun's chair or alternative belay position.
• If it is necessary to hang in your harness, change position as necessary to keep comfortable and try to regularly tense your calves to maintain circulation
• Always wear a chest harness so that you can lean back without risk of turning inverted or falling from your harness if consciousness is reduced or lost for any reason
• If you feel at all faint or unwell at any time, let others know, tense your legs repetitively and try to lower your head and raise your legs.

Patients / people being rescued:

• Stabilise the patient as well as possible before a lift
• Ensure cold patients are adequately insulated with dry and waterproof clothing or a plastic bag and blankets or hypothermia bag if in a stretcher - do not forget to insulate the head.
• Rehydrate if possible - oral water or sports drinks if conscious, IV fluids if medicla or paramedic assistance enables this.
• If exhausted, provide some easily digestible energy source - glucose sweets etc.
• Treat any cold or exhausted person as a patient and ensure they are closely monitored and, if possible, hoisted horizontally in a stretcher rather than allowed to climb or be hoisted in a harness only.
• If a horizontal stretcher hoist is not feasible, consider an under knees strop to hold the patient more horizontally.
• If vertical hoist is unavoidable, minimise lift time
• Accompany patients during lifts wherever possible
• Monitor vital signs - both ask the patient how they feel and check pulse rate as a minimum - changes make give you warning of impending collapse
• Ask conscious patients to do leg contractions to assist circulation

Treating Suspension Induced Shock Syndrome

• Get the patient horizontal as soon as possible, consistent with safety for rescuers
• If collapse occurs mid hoist and intervention is not possible on the rope, complete hoist or lower patient rapidly - whichever will get the patient to a stable position with at least one rescuer to provide care
• Provide Basic Life Support as needed for any unconscious or arrested patient
• Elevate legs if faint or warning signs only
• Stabilise patient further before attempting to continue lifting and change to horizontal lifting system if at all possible.