The conversations that we always have on course but never really pay much heed to because they are so uncommon. But how much do we really know about lightning strikes and the effect that they have on the human body? And would you know what to do to provide medical care for someone who was struck by lightning?
This super fascinating blog by Dr. James Jordan gives out a lot of very useful information and whilst these things are rare, it is always worth remembering that Worse Things Happen at Sea!!
What is the risk at sea?
According to US insurance statistics, roughly one in every thousand boats is damaged by lightning each year. In some areas, such as the Mediterranean and Caribbean, up to 10% of all maritime insurance claims relate to lightning strikes.
Advice abounds on measures to protect against catastrophic damage from lightning. The effectiveness of various methods is still debated, but it is generally agreed that protection systems involving air terminals and grounded conduction pathways can reduce the risk to the fabric of the boat. No system, however, can reliably prevent boats from being struck in the first place, and whenever this occurs there is a significant risk to the health of the crew.
Lightning can bypass taller structures like masts and strike crew members directly, or it can jump sideways from other parts of the boat. The current can travel along the deck or through metal and electrical equipment, and it can arc through the air from one charged object to another, passing through anybody unlucky enough to be in the way.
General advice to crews caught out in lightning storms is to shelter down below and put on dry clothing. Commercial ships usually have effective lightning protection systems which reduce the risk of lightning passing through the cabins, but crew should still try to avoid touching metal structures or wired electrical items. If crew members have to go out on deck, they should try to stay away from tall structures if possible. Some sources suggest that wearing insulating boots and gloves can improve safety, and that wet foul weather clothing worn over a dry layer can protect the wearer by routing lightning around their body, but the evidence for these measures is not strong.
How does lightning cause harm?
Lightning injuries are often compared to high-voltage electric shocks from mains electricity, but the effect of lightning is actually very different. In mains electrocution, electrical current passing through the body can heat the tissues, causing significant burns. Lightning strikes involve very high voltages but are also very brief, typically lasting only one-thousandth to one-tenth of a second, and much of the electrical current flows over the outside of the victim’s body. The tissue heating effect is relatively small so major internal burns are rare. Any moisture on the skin, however, may vapourise into steam, blowing victims’ clothes and shoes off and causing superficial burns. Metal jewellery may melt and become ‘tattooed’ into the skin.
Rather than causing major burns, lightning strikes tend to inflict significant neurological injury. 70% of those struck by lightning are rendered unconscious, and damage often occurs to the central and peripheral nervous systems. Survivors may have a range of neurological symptoms immediately after being struck, a common example being ‘Keraunoparalysis’ in which the lower limbs are temporarily paralysed. Injury to the autonomic nervous system - the nerves responsible for controlling body functions like heart rate and blood pressure - may also wreak physiological havoc, altering blood flow or even stopping the heart.
Most deaths from lightning strike are due to sudden cardiac arrest. This can be triggered by autonomic dysfunction but in most cases is thought to be caused by direct electrical disruption of the heart muscle.
Lightning victims may also suffer trauma from blast injuries or flying shrapnel. They can be thrown some distance by the strike, risking secondary trauma or being lost overboard.
What are the long-term outcomes?
Around 90% of people who have been struck by lightning survive, but three-quarters of survivors are left with permanent disability. Long-term neurological and psychiatric dysfunction can include paralysis, memory impairment, mood changes or fatigue. Damage to the eyes or optic nerves can cause blindness, and cataracts can form within days of being struck. Chronic pain due to nerve damage is unfortunately also common.
To summarise, those whose hearts keep beating after a strike will probably survive, and those who initially appear dead may respond well to CPR and rapid defibrillation. Lightning victims may have burns or trauma that require immediate stabilisation on board, but even apparently well survivors will need to be evacuated to shore-based care for investigations and monitoring. Given the wide range of injuries and likely long-term harm suffered by lightning victims, by far the best way to manage lightning strikes at sea is to take early action to protect crew by encouraging them to shelter below deck. As the US National Weather Service says, “when thunder roars, go indoors!”