Outside the medical world, it is commonly thought that little is known about the effects and potential consequences of being upright and motionless (orthostasis), for example, as one would be if unconscious and suspended in a harness.
However, over the past three years much has been discussed and even some courses have been available to educate the workforce on its effects and prevention techniques, usually coupled with rescue devices or rescue training.
This article is designed to educate the reader, not in these well discussed techniques, but in the roots of issue and how our human physiology sometimes works against us. I shall conclude with some recommended practices however, as I feel that these should be reiterated wherever possible.
Orthostatic syndrome and orthostatic syncope
Orthostatic syndrome and its causes are well known in the medical field. Standing up quickly or for periods without moving can cause the person to feel dizzy, nauseous, to have hot flushes and unusual sweating and to faint. When fainting occurs in this kind of situation it is known as orthostatic syncope. This is quite common and is said to be related to the current state of evolution of the human being in that we have not yet totally adapted to standing upright. In certain circumstances, the effect can be serious and can lead to death.
The most popular example of this is that of the soldier who faints while stood to attention for a long period of time. The moment the soldier loses consciousness, he collapses and becomes horizontal. Therefore, the time spent in the vertical while unconscious is minimal. This has significant bearing on the result of the collapse. Assuming no injuries caused during the collapse of the soldier, return to consciousness will ensue quickly and recovery is likely to be rapid.
If a person is suspended in a harness in a situation in which the legs are immobile, for example, due to injury after a fall, there is no such “natural” move to the horizontal. The time spent in this unmoving suspended position, with the legs below the heart can have fatal consequences.
The fundamental cause of orthostatic syncope seems to be venous pooling.
Venous pooling is the accumulation of blood in the veins (typically in the legs) due to gravity. Some venous pooling when a person is stood up is normal. Muscular action in moving the limbs, together with one-way valves in the veins, normally assists the return of blood in the veins back to the heart. If the legs are completely immobile, these “muscular pumps” do not operate and an excess of blood accumulates in the veins, which are capable of considerable expansion, and therefore, considerable capacity. Retention of blood in the venous system reduces the circulating blood volume available to the heart. Thus the circulatory system is disturbed. During excessive venous pooling, cardiac output and arterial pressure fall, which may critically reduce the quantity and /or the quality of (oxygenated) blood flowing the brain and precipitate syncope.
A common term for syncope is fainting. Syncope is described as the temporary loss of consciousness and postural tone (balance and ability to stand) due to a decrease in the quality and / or quantity of blood flow to the brain. The brain is not good at coping with low blood oxygen or low glucose levels and, in such circumstances, syncope can occur. The warning symptoms that are given before syncope, such as palpitations, nausea, dizziness, sweating and confusion are known as pre-syncope.
When a person is upright, for example stood up or suspended in a harness, blood has to be forced against gravity to the head, which requires special blood pressure regulation. The body does not take kindly to anything that interferes with its blood circulatory system, such as venous pooling, and sets off a series of intended compensatory reactions at the first signs of any imbalance, the result of which are the symptoms experienced in pre-syncope. The body is now in a state of (orthostatic) shock.
Loss of consciousness assures that a person suspended will not be moving his or her limbs, so venous pooling will increase, which will in turn reduce the circulating blood volume even further. In addition, any restrictions of the femoral arteries and veins caused by the harness straps could be a contributory factor to venous pooling. Thus, the detrimental effects are increased. These include not only a potentially fatal reduced blood flow to the brain, but also the effect on other vital organs, such as the kidneys.
The kidneys are also very sensitive to blood oxygen levels and renal failure as a result of excessive venous pooling is a real possibility.
Unless a casualty is rescued very quickly and unless the rescuers follow a particular procedure, the effects of venous pooling and syncope are likely to lead to death, as the brain and kidneys are deprived of vital oxygen. Moving the casualty quickly into a horizontal, a natural reaction, is likely to cause a massive return of deoxygenated (and possibly toxic) blood to the heart, which is unable to cope, causing cardiac arrest.
Tolerance to the effects of orthostasis appears to vary between individuals. However, evidence shows that given sufficient time, orthostatic shock, presyncopal effects and syncope will occur. The onset of these effects can be exacerbated by various factors. These include the shock of experiencing the event that caused them to be suspended and immobile in the first place, the injuries suffered by the casualty, their harness comfort level, and possibly their psychological state.
Prevention of suspension trauma, rescue and treatment of casualties
The first action in helping to prevent the onset of suspension trauma is in the choice and adjustment of the harness. Before using a harness for the first time, users should carry out a suspension test in a safe place, to ensure that their harness is the correct size, has sufficient adjustment and is of an acceptable comfort level for the intended use and a comfortable, properly adjusted harness could delay the onset of suspension trauma.
Steps should be taken to ensure as much as possible that a person using a harness will not be put in a position where they will be at serious risk of suspension trauma. There should always be a well thought-out and practised rescue plan in place appropriate to the workplace, and appropriate rescue facilities should always be on hand to enable an immediate and safe rescue should the need arise. Knowledge of and adherence to the following points should minimize the risk:
• Awareness that anyone who is suspended in a harness may be at risk of suspension trauma if they were to hang motionless in the harness
• Awareness that suspension trauma is life threatening. Whatever the type of harness, motionless suspension is not physiologically safe and can lead to very serious blood circulation problems, including death
• Awareness that anyone sustaining a head injury while on a rope is particularly at risk, especially if they lose consciousness. Casualties immobilised in a stretcher in a vertical lift or head-up position may also be at risk “there should always be a well thoughtout and practised rescue plan in place appropriate to the workplace”
• Awareness of the symptoms of suspension trauma (i.e. the symptoms of pre-syncope) and precautions
• Awareness that leaving an unconscious person suspended on a rope can cause death in a relatively short period of time
• Release of a casualty from the suspended position as quickly as possible
• Rope access workers and rope rescuers should not attempt long or difficult ascents (or descents) when fatigued, dehydrated, hypothermic or low on energy
• Tasks should be avoided that require a long period of suspension in a harness with little support of the legs or movement of them
• Workers should never be allowed to work at height alone where there is a possibility of immobile suspension, either in an emergency or otherwise
• Frequent “pumping” of the legs, preferably against a firm surface will activate the muscles and reduce the risk of venous pooling. This applies to workers in a normal working environment, e.g. rope access workers, and to conscious persons suspended after a fall
“the first action in helping to prevent the onset of suspension trauma is in the choice and adjustment of the harness”
• For suspended persons, the use of a footloop will alleviate pressure (and therefore pain) on parts of the body such as the wrists and thights. Reducing pain could delay presyncopal and syncope. The footloop would also provide support to facilitate “muscle pumping”
• If possible, conscious casualties awaiting rescue who are unable to perform “muscle pumping” should arrange themselves or be arranged so that their legs are in a substantially horizontal position or with knees elevated
Following this basic guidance it should be noted that the HSE in the UK carried out a review and noted that: -
“The literature review revealed no documented cases of suspension trauma occurring during industrial use of fall protection. The term “suspension trauma” is one that has developed as a parlance amongst many who work in the fall protection industry and training sector. It is used to describe the situation of a person falling into suspension in a harness and then becoming unconscious. In this scenario the loss of consciousness is not due to any physical injury, but rather, it is thought that orthostasis, motionless vertical suspension, is responsible. “Trauma” is therefore an inappropriate term which may be better replaced by the descriptive term “syncope” which is the sudden transient loss of consciousness with spontaneous recovery, as may occur with a simple faint.”
In finality, it should be noted that there is a distinct lack of scientific published literature regarding the circumstances and consequences of harness suspension, and none that tests the effect of sitting a rescued casualty in the semi-recumbent posture that some authors have suggested. I sincerely hope that this changes in the coming years so that we can better understand the physiological consequences and act to prevent this potentially deadly situation.
Published: 10th Feb 2010 in Health and Safety Middle East