Treestand Safety: Orthostatic Intolerance

Sponsored by Mountaineer Sports (maker of the life-saving Rescue One  ‘CDS’ Controlled Decent System) and the TreeSuit.

By: Richard L. Holdcraft, BA, MS, HHD Consulting Group, LLC

Regardless of which type of safety harness the hunter uses while hunting from treestands, they should be aware of a condition medical practioners describe as orthostatic intolerance.  Let’s take a minute to describe the signs and symptoms of orthostatic intolerance; discuss how orthostatic intolerance can occur while hunters are suspended following a fall; and outline recommendations for preventing orthostatic intolerance, as well as recommendations for hunter training and self-recovery and self-rescue.

Orthostatic intolerance may be defined as “the development of symptoms such as light-headedness, palpitations, tremulousness, poor concentration, fatigue, nausea, dizziness, headache, sweating, weakness and occasionally fainting during upright standing”.  While in a sedentary position, blood can accumulate in the veins, which is commonly called “venous pooling,” and cause orthostatic intolerance. Orthostatic intolerance also can occur when an individual moves suddenly after being sedentary for a long time. For example, a person may experience orthostatic intolerance when they stand up quickly after sitting still for a long time.

A well-known example of orthostatic intolerance is that of a soldier who faints while standing at attention for long period of time. The moment the soldier loses consciousness, he or she collapses into a horizontal position. With the legs, heart, and brain on the same level, blood is returned to the heart. Assuming no injuries are caused during the collapse, the individual will quickly regain consciousness and recovery is likely to be rapid.

Venous pooling typically occurs in the legs due to the force of gravity and a lack of movement. Some occurs naturally when a person is standing. In the veins, blood normally is moved back to the heart through one-way valves using the normal muscular action associated with limb movement. If the legs are immobile, then these “muscle pumps” do not operate effectively, and blood can accumulate. Since veins can expand, a large volume of blood may accumulate in the veins.

An accumulation of blood in the legs reduces the amount of blood in circulation. The body reacts to this reduction by speeding up the heart rate in an attempt to maintain sufficient blood flow to the brain. If the blood supply is significantly reduced, this reaction will not be effective. The body will abruptly slow the heart rate and blood pressure will diminish in the arteries. During severe venous pooling, the reduction in quantity and/or quality (oxygen content) of blood flowing to the brain causes fainting. This reduction also can have an effect on other vital organs, such as the kidneys. The kidneys are very sensitive to blood oxygen, and renal failure can occur with excessive venous pooling. If these conditions continue, they potentially may develop very serious results.

Orthostatic intolerance may be experienced by hunters using fall arrest systems. Following a fall, a hunter may remain suspended in a harness. The sustained immobility may lead to a state of unconsciousness. Depending on the length of time the suspended hunter is unconscious and immobile and the level of venous pooling, the resulting orthostatic intolerance may lead to serious consequences. While not common, such incidents often are referred to as “harness ­induced pathology” or “suspension trauma.”

Unconscious and immobile hunters suspended in their harness will not be able to move their legs and will not fall into a horizontal position, as they would if they fainted while standing. During the static upright position, venous pooling is likely to occur and cause orthostatic intolerance, especially if the suspended hunter is left in place for some time. Venous pooling and orthostatic intolerance can be exacerbated by other circumstances related to the fall. For example, shock or the experience of the event that caused the fall, other injuries, the fit and positioning of the harness, the environmental conditions, and the hunter’s psychological state all may increase the onset and severity of the pooling and orthostatic intolerance.  Unless the hunter is rescued promptly using established safe procedures, venous pooling and orthostatic intolerance could result in a serious injury, as the brain, kidneys, and other organs are deprived of oxygen.

The amount of time spent in this position, with the legs below the heart, affects the manner in which the hunter should be rescued.  Moving the hunter quickly into a horizontal position – a natural reaction – is likely to cause a large volume of deoxygenated blood to move to the heart, if the hunter had been suspended for an extended period. The heart may be unable to cope with the abrupt increase in blood flow, causing cardiac arrest.  Rescue procedures must take this into account.

If you fall, regardless of the harness system you only have moments to regain your footing before suspension trauma sets in followed by unconcousness and death. The only harness to avoid ST is the Rescue One 'CDS' from Mountaineer Sports.

Recommendations:

Prolonged suspension from fall arrest systems can cause orthostatic intolerance, which, in turn, can result in serious physical injury.  Research indicates that suspension in a fall arrest device can result in unconsciousness, with mores serious consequences in less than 30 minutes. To reduce the risk associated with prolonged suspension in fall arrest systems, hunters should initiate self-recovery/self-rescue as soon as possible after the fall.

Here are a few suggestions for self-recovery/self-rescue:

  1. Plan your hunt and hunt your plan.
  2. Let other hunters in your group know where you are hunting and when you expect to return.
  3. Always maintain 3 point of contact whenever your feet leave the ground to ascend, while in the stand and while descending.
  4. Carry a cell phone or two-way radio communication device with you.
  5. As soon as you fall, contact someone in your hunting group and let them know you are attempting self-recovery/self-rescue.
  6. Call them back once you have completed the self-recovery/self-rescue maneuver.
  7. Let other hunters in your group know that if you do not call them back in 3 to 5 minutes to come and assist you.
  8. Keep your legs moving to pump oxygenated blood through your body to major organs.
  9. Do not cut or loosen straps on the safety harness until it is absolutely safe to do so.
  10. Place your anchor line from your full-body harness to the tree at shoulder height or above and shorten the tether line to 24 inches or less.
  11. ever hunt from an elevated stand if using medications which induce drowsiness or which could result in you becoming unconscious.
  12. If you are in an elevated stand and become sleepy, sick or drowsy, call for help and quickly descend to the ground.
  13. If you receive a call from a member of your hunting group indicating they need assistance in recovery or rescue, follow these guidelines:
  14. Rescue suspended hunters as quickly as possible.
  15. Be aware that suspended hunters are at risk of orthostatic intolerance and suspension trauma.
  16. Be aware of signs and symptoms of orthostatic intolerance.
  17. Be aware that orthostatic intolerance is potentially life threatening. Suspended hunters with head injuries or who are unconscious are particularly at risk.
  18. Be aware of factors that can increase the risk of suspension trauma.
  19. Be aware that some authorities advise against moving the rescued hunter to a horizontal position too quickly.
  20. To avoid this problem entirely, we recommend that you use a RESCUE ONE ‘CDS’ safety harness.  Go to Mountaineer sports.com for more information.