Maritime health: Man overboard (MOB)

MAN OVERBOARD (MOB)

HOW WILL THE SHIP’S DOCTOR OR SISTER KNOW A MAN IS OVERBOARD

1) A crew member may be shouting “Man overboard”
2) The man who fell overboard may be waving or shouting
3) A crew member may be hitting a signal against the hull of the ship; three short strikes which is the signal for “man overboard” (and the signal for “O”)
4) The ships’ whistle or horn blowing three short blows which is the signal for man overboard
5) The ship’s whistle or horn blowing seven or more short and one long blow which is the international general emergency signal, signalling that all crew members must muster on deck immediately. The general emergency signal can mean there is a collision, flooding, fire or MOB.
6) A flare may be seen sent up near-vertically to draw the attention of other ships.
7) There can also be communication via vessel intercom system / telephone, voice pipe, loud hailer, cell phones if near port or via messenger (runner).

MOB is different than a “missing man” protocol. During the missing man protocol the position of the vessel is noted. The vessel slows down but stays on course. A thorough vessel search is conducted.

TERMINOLOGY
Drowning: respiratory impairment due to submersion in water
Fatal drowning: drowning resulting in death
Non-fatal drowning: drowning that has not resulted in death (the terms near drowning, wet and dry drowning is not used any longer)
Submersion: the head of the person is under water
Immersion: the body of the person is in the water

DETERMINANTS OF SURVIVAL OF THE VICTIM
– Temperature of the water: a person can swim a maximum of 800 meters in water that is 15 degrees Celsius if they are wearing a life jacket. They can only survive 15 minutes in water that is that cold
– The clothing of the person overboard. Layers of clothing protects the victim as the clothes can catch body-warmed water between the clothing layers. If they are clothed in immersion suits the body core temperature won’t drop lower than 2 degrees over a 6 hours period in water of 1 degree Celsius
– The ability of the MOB to swim. If the MOB is wearing a life jacket the chance on survival increases. If the MOB has a life ring or automatic flotation divice or even a floatable article like a fire bucket, their chances on survival increases. The 1/10/1 rule applies; one minute of initial cold water shock during which there is a major risk of aspirating sea water into the lungs; 10 minutes of body shutdown when you loose feeling and function of your hands and arms in freezing water (if you have a life jacket, you might survive this phase); one hour of hypothermia. You have one hour in which the ship can pick you up before you succumb due to hypothermia
– If the MOB complies with the training then the chances of survival increases. The MOB must not attempt to swim after the boat as this is futile. The MOB must wave, shout or blow a whistle to draw attention to the fact that they fell overboard. The MOB must go into the heat escape lessening position (HELP). In this postion the knees are drawn up over the chest and the arms crossed over the drawn-up knees. Multiple MOBs must huddle together. They must form a circle with their feet pointing to the middle. The most vulnerable one must be centred in the middle of the group with the rest surrounding him or her like the petals of a flower
– If the MOB does not get serious injuries caused by the fall or caused by the rescue attempt, the chances of survival increases. There is always the danger of bumping the MOB with the hull of the rescue boat during rescue. The risk of a C-spine, skull or other spine fracture is a real one.
– Experience and training of the rescue team in MOB retrieval. It may be difficult to extract a fully-clothed wet MOB from water due to the excess weight. A sling or hoist may have to be utilised to get the heavy wet body out of the water. Mouth-to-mouth resuscitation may have to be initiated by the rescuer while both still in the water
– The weather conditions play a big role in whether the MOB will be rescued successfully. The chances of succesfull rescue in a full-blown storm is very slim.
– The consciousness level of the MOB after falling into the water. A MOB that aspirated water into their lungs due to the uncontrolled gasping on submersion in freezing water have a worse prognosis
– The hypothermic MOB must be kept as horizontal as possible during the retrieval. If the MOB has to climb a ladder to gain access to the rescue ship or FRC, or has to escalate vertical scrambling netting up the side of the ship they can succumb to cardiac arrest. Even the dangling in a “horse collar” lifting sling during a helicopter retrieval can lead to circulatory collapse. It is advisable that the hypothermic survivor during helicopter retrieval has a double sling to keep him horizontal during helicopter retrieval and a basket stretcher to keep the MOB horizontal up the side of the rescue ship. It is not recommended that the MOB be placed in a basket stretcher on a FRC due to lack of storage space on such crafts

LEVELS OF HYPOTHERMIA
DEGREES CELSIUS SYMPTOMS
37 Normal body temperature
36 Cold exhaustion Shivering
35 Mild hypothermia Confusion
34 Amnesia, cramps
33 Moderate hypothermia CNS Sx pupils dilate, shivering stops
32
31
30 Severe hypothermia Slow pulse and RR
29 Arrhythmia
28 Unconsciousness Reflexes absent
27 VF
26 Critical hypothermia Rigdity absent
25
24 Max risk of VFib
23
22
21
20 Heart standstill
19

OTHER IMPORTANT FACTORS AT EXTRACTION OF MOB FROM THE SEA
– Get the MOB to the ship’s hospital ASAP
– Start rewarming ASAP while still in the rescue boat
– CPR while in acute hypothermia MAY be detrimental due to the risk of lowering the core temperature even more. ABC is more important than CAB in drowning victims. Pulmonary resucitation must continue. The protocols will depend on whether you are dealing with a drowned MOB, a drowned and hypothermic MOB, or a hypothermic MOB.

EXTENDED TRANSPORTATION TIME TO SHIP’S HOSPITAL
– Remove wet clothing. Replace with dry clothing or insulation (passive rewarming)
– Stabilise fractures, treat dislocations, control bleeding, cover wounds
– Warm IVs (be aware of hypoglycemia and treat with 50 ml 50% dextrose as necessary)
– Active rewarming
– Wrap patient. This is impotant if the time of accident-to-hospital door is predicted as extended and the injured person is exposed to environmental factors, such as outdoors. First plastic sheet on floor, then sleeping insulation pad, the layer of blankets, sleeping bag or bubble wrap, then patient and heating bottles, then wrapping of MOB “package”. Cover face partially but keep airways clear of obstruction. Putting normothermic rescuer in sleeping bag with hypothermic may be considered
– If Glascow scale 13 or less, nil per mouth due to the risk of aspiration

IN THE SHIP’S HOSPITAL
A MOB can be rewarmed throught the following organs
– the skin: place MOB in a warm bath of 40 degrees Celsius
– the airways; warm nebulised fluid (not appropriate for the non-fatally drowned MOB)
– the intravenous route: warmed IV normal saline and 5% dextrose at 40 degrees Celsius (remember the possibility of use of a microwave to warm the fluids)
– areas of superficial vasculature: place warmed normal saline liter bags next to carotids and between the scapulas, pit of stomach, axillae and near the genitals (prevent burn wounds by wrapping IVs in fleece)
– Intestine: Warmed fluids in condoms per rectum or in esofagus if the expertise is present
– Remember not to concentrate on warming the extremities first as the cold peripheral circulation will then cool the core temperature rapidly. Start with warming the core
– Keep c-spine injuries in mind during resucitation
– Remove wet clothing as a dry skin promotes warming
– Keep on resuscitating until “warm and dead” (keep on resuscitating three times longer than usual). Remember that dilated pupils alone are not neccesarily an indication of brain death in the hypothermic patient
– Do not massage frozen extremities
– Transcutaneous pacing (TCP) is contra-indicated in severe hypothermia (ACLS guidelines 2011).
– Remember Hypothermia is one of Hs and Ts of cardiac arrest as per ACLS protocol (ACLS guidelines 2011). The other Hs and Ts are Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo/Hyperkalemia, Tension pneumothorax, Tamponade, Toxins, Thrombosis (pulmonary), Thrombosis (coronary)
– A cardiac arrest patient in VF/ VT who has SEVERE hypothermia and a body temperature of less than 30 degrees Celsius (less than 86 degrees Fahrenheit) a single defibrillation attempt is appropriate. (ACLS guidelines 2011). If unsuccessful, continue CPR, BLS, active rewarming and vasopressor therapy
– A cardiac arrest patient with moderate hypothermia (30 to 34 degrees Celsius) [86 – 93 degrees Fahrenheit] start CPR, attempt defibrillation, give medications at longer intervals and if in hospital provide rapid active core rewarming (ACLS guidelines 2011)
– J- or Osborne waves are seen on ECG when hypothermic
– Hypothermia with all the other Hs and Ts can cause pulseless electrical activty (PEA) of the heart (ACLS guidelines 2011)
– A potassium level of more than 10 mEq/l may indicate that resucitation levels are futile and that death has occured
– Be aware of hypoglycemia

NON-FATAL DROWNING
Can be classfied into the following categories
– Totally asymptomatic patients; Nil to do
– Minor asymptomatic patients; give cough mixture
– Slight symptomatic patients; oxygen and 24 hour observation
– Medium symptomatic patients; treat pulmonary oedema and hospital admission
– Major symptomatic patients; treat pulmonary oedema (and possible ETI) and ICU admission
– Respiratory arrest patients; treat respiratory arrest with ETI and ICU admission
– Cardiopulmonary arrest patients; treat cardiopulmonary arrest and ICU admission

Note that drowning victims are prone to vomiting and therefore at risk of aspiration. Turn on side and GENTLY finger sweep after vomiting. Maintain c-spine as needed