Archive for the ‘Dive Medicine’ Category

New! From The Wilderness Medicine Newsletter

February 10, 2012

For decades the Wilderness Medicine Newsletter has provided up-to-date information to pre-hospital and definitive care providers. Since becoming an on-line journal, the readership of the WMN has become international. Now the WMN has it’s own web site: www.wildernessmedicinenewsletter.com

Subscribers pay the same $15 a year subscription rate but have access to more than 165 articles from back issues as well as current issues. You can search the site either by category, or by key words making the Wilderness Medicine Newsletter site a much more useful reference for everything from reviewing splinting to the prevention and treatment of tropical diseases.

Check it out!

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VII. PAS – Secondary Survey – SOAPnote:

April 15, 2008

Part 7 of 9: PAS – SOAP note: What is our patient care plan? 

The SOAP note is organized into the Subjective date, Objective date, the Assessment, and the Plan.

Subjective:
The subjective date is their age, sex, the mechanism of injury (MOI), and the chief complaint (C/C), i.e., what they are complaining of.

Objective: 
The objective date consist of their vital signs, the patient exam, and the AMPLE history.

Vital signs: 
Time the vitals signs are taken:   
RR & Effort    
HR & Effort(BP)    
LOC    
Skin: C/T/M    

Patient exam:  Describe locations of pain, tenderness & injuries.
                                                                                                                                               
AMPLE history:
Allergies:           
Medications:             
Past pertinent medical history:         
Last intake & output:           
Events leading up to accident:         

A – Assessment:  (problem list)
1.                                                                                                                                                  
2.                                                                                                                                                   

P – Plan:  (plan for each problem on the problem list)
1.                                                                                                                                                   
2.                                                                                                                                                  
3.  MONITOR – reSOAP your patient every 5 – 15 minutes.

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Heat Loss Through the Head and Hypothermia

February 14, 2007

The rate of heat loss, at rest, with exercise, and with hypothermia

Since there has been a fair amount of interest regarding Myth #2 in the Wilderness Medicine Newsletter – Frozen Mythbusters, Nov/Dec 2004 – the topic deserves more discussion.

MYTH #2 states.  “If your feet are cold, cover your head because you can lose up to 75% of your body heat through your head alone.

The problem is that the head is only about 10% of the body surface area.  Thus, the head would have to lose about 40 times as much heat per square inch or centimeter compared to the rest of the body.
 
Gordon had heard this statement one too many times and finally decided to see if this was indeed true.  So he took several test subjects, all volunteers, of course, (you have to wonder what problem they caused at the university), wired them to monitor their core temperatures, and discovered that we do indeed lose heat through any exposed part of the body and the amount of heat we lose depends on the amount of exposed surface area.  The rate of heat loss is relatively the same for any exposed part of the body not simply the head. You do not lose heat significantly faster through the scalp than any other portion of the body with the same surface area. 

It is still a good idea to put on a hat (a hood really – what insulation does a baseball hat have?) if your feet are cold.  But what is BUSTED is that there is nothing peculiar or unique about the head. The idea that we lose heat faster through out scalp, because of the constant blood supply to the brain, is simply a myth. (One that I personally have believed for many years.)”

UPDATE & DISCUSSION
 
#1 Heat loss via the head at rest, during exercise, and with hypothermia:

I did have the opportunity to speak with Dr. Murray Hamlet about this topic, and we hope this additional information will help to clarify heat loss in the hypothermia patient.

The cerebral blood flow is supplied via the carotid and vertebral arteries (4 in total) and is constant. The blood flow to the brain does not change as the demand for oxygen is constant. As a result, when you look at total heat loss, the head accounts for about 7% of the heat lost. 

The cerebral blood flow does, however, vary based on cardiac output – the harder your heart beats, the greater the blood flow to the brain.  And as you increase the blood flow to the brain, you also increase the percentage of heat loss.  As it turns out, when you begin to exercise, there is increased cerebral blood flow. This increases the percentage of heat lost through the head to about 50% of total body heat loss.  But as the person continues to exercise, the muscles demand more oxygen which increases blood flow. To ensure thermoregulation and maintain normal core temperature (exercises increases body heat), the skin vasodilates which increases blood flow to the skin to cool the blood. The net result is a decrease in the total blood flow to the brain and a decrease in percentage of total body heat lost through the head to about 10%.  Once sweating begins, the percent lost through the scalp returns to 7%.

In Gordon’s research his test subjects were at rest in cool water, and the researchers were comparing the rate of heat lost by monitoring core temperature through different body parts and quantities of skin exposed.  At rest, they found that the rate of heat loss only depended upon the amount of skin surface area exposed, and the percentage of heat lost through the head was the same as the rest of the body.

Research at the Army Research in Environmental Medicine labs showed that there was a temporary increase in heat loss through the scalp that returned to the baseline of 7% as the subjects continued to exercise.

Now, what about hypothermia and heat loss through the head? 
If the hypothermia victim is not shivering, they are at rest, and the heat loss through the head remains about 7%.  But, this is important, if they are shivering, the percent of heat loss via the scalp can increase to upwards of 55%, so protecting the head well is a very important part of treating the hypothermia patient.  And as you can imagine, the primary defense against the cold and hypothermia is vasoconstriction of the peripheral circulation, this shunts blood to the core, reduces circulation to the skin, and increases the percent of heat loss through the scalp.

The difference is that the shivering hypothermia patient is indeed exercising, but they do not vasodilate the peripheral circulation; the shivering muscles increase metabolic demand and cardiac demand so the patients do increase their cardiac output; therefore, they do increase cerebral circulation; therefore, they do increase the percent of blood loss through their head.

Treatment of the hypothermia victim:
Remove from the cold.
Get them dry and keep them dry.
Insulate from the ground.
Hypothermia wrap:
Re-insulate with dry insulation.
Cover and protect the head from further heat loss.
Cover and protect the hands and feet from frostbite.
 Surround with a windproof and waterproof layer.
If conscious, feed warm, sweet liquids.
If unconscious, evacuate and handle very gently to prevent ventricular fibrillation.

#2 How does being in water change the equation?

Life-preserver, personal flotation device (PFD), research has shown that when in the water, if your head and neck are wet, you cool faster.  This is why modern PFD’s hold the person in the water with their head and neck out of the water; even if unconscious, to decrease the rate of heat loss into the water.

#3 What difference does hair on your head or facial hair make?

None. 
In order for hair or fur to provide a protective thermal barrier, it has to be much denser than what we humans grow and it has to be in layers of different types of fur to provide a thermal barrier.  Beards are great, but they do not keep you any warmer. And bald is beautiful.

We at the Wilderness Medicine Newsletter appreciate the comments and discussion.
 

BAROTRAUMA & DYSBARISMS #9

January 31, 2007

DECOMPRESSION SICKNESS (DCS):

Rapid reduction in ambient pressure, during ascent, causes dissolved gases to come out of
solution and form bubbles of nitrogen, the oxygen is rapidly metabolized in the tissues.

Gas bubbles can: 
– obstruct small blood vessels
– cause changes in blood chemistry
– stretch and damage tissues

Symptoms present within 12 hours.
– 80% within 1 hour of surfacing.
– 95% within 4 hours of surfacing.

TYPE I  – musculoskeletal limb pain
BENDS = periarticular pain in arms & legs (arms > legs)
pain relieved by direct pressure
pain can be mild, “Niggles,” to severe
skin/lymphatic involvement = pruritus, marbling, rashes

TYPE II – neurological
pain in areas other than the extremities
CNS changes = cord involvement or cerebral
spinal cord DCS = most common form of DCS in divers
paresthesia s – ascending numbness – paraplegia
urinary retention – fecal incontinence – priapism

Cerebral DCS:
classic CVA symptoms
pulmonary manifestations – “CHOKES”
occurs within minutes of surfacing
substernal chest pain – cough – dyspnea
can progress to respiratory failure and shock
labyrinthine or inner ear DCS – “STAGGERS”
vertigo – nausea/vomiting – tinnitus – hearing loss – nystagmus
                 
TREATMENT FOR DCS TYPE I & II:    
RECOMPRESSION
100% oxygen (helps to wash out nitrogen)
IV fluid therapy with crystalloid (hemoconcentration)
diazepam or phenergan for vertigo – nausea – vomiting
should not dive for 6 months after DCS & not until full evaluation

RECOMPRESSION – HYPERBARIC THERAPY
to reduce the size of the bubbles
to promote reabsorption
prevent further bubble production

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BAROTRAUMA & DYSBARISMS #8

January 29, 2007

ARTERAIL GAS EMBOLISM:  (AGE)Most serious of all dive injuries – frequently fatal.
Second only to drowning in fatalities in sport divers.
Ruptured airways allow air bubbles to enter the pulmonary circulation and go to the left side of the heart.
From the left ventricle may migrate to the coronary or cerebral circulation.
Resulting in:
ACUTE MYOCARDIAL INFARCTION (AMI)
CEREBROVASCULAR ACCIDENT (CVA)
AGE usually presents within 10 minutes of the “burst lung”.

SYMPTOMS: 
CVA = neurological symptoms:
change in mood or affect
visual disturbances
hemiplegia or hemiparesis
unconsciousness

AMI = apnea – dyspnea
chest pain – chest pressure
dysrhythmia s – asystole

SUDDEN LOSS OF CONSCIOUSNESS BEFORE SURFACING IS AGE UNTIL PROVEN OTHERWISE

TREATMENT:  RECOMPRESSION!!!
100% O2 while transporting
Transport supine & MONITOR AIRWAY

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BAROTRAUMA & DYSBARISMS #7

January 27, 2007

PNEUMOMEDIASTINUM & INTERSTITIAL EMPHYSEMA:
Ruptured airways allow air to escape into the soft tissues.
Air dissects into the mediastinal – into the pericardium – cephalad into the neck.

SYMPTOMS: 
subcutaneous air & crepitus on compression of the skin – neck
change in voice
dyspnea
pericardial air on x-ray

TREATMENT: 
Interstitial (subcutaneous) emphysema is not dangerous.
100% O2 will hasten recovery.
Must be monitored for other sequela = pericardial tamponade.

PNEUMOTHORX:   (TENSION PNEUMOTHORAX)
Ruptured airways allow air to escape into the pleural space.
Air trapped in the pleural space.

SYMPTOMS: 
Vary from mild to severe dyspnea with cyanosis.

TREATMENT: 
Monitor if mild.
100% O2 in severe cases, may require artificial ventilation.
Chest tube thoracotomy for severe = tension pneumothorax.
Needle thoracotomy in emergency.

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BAROTRAUMA & DYSBARISMS #6

January 25, 2007

ASCENT INJURIES:  “REVERSE SQUEEZE”

ASCENT   = expansion of the gas.     
The volume of gas increases by 2, doubles, every 33 fsw.

This is why it is an absolute rule that people with asthma cannot SCUBA dive!
ASTHMA and SCUBA diving = death
.
During ascent some of the air breathed at depth will get trapped in the alveoli and bronchioles, then during ascent that trapped air will expand and burst the alveoli and bronchioles, resulting in burst lungs and DEATH.

PULMONARY OVERINFLATION:
“Pulmonary Over Pressurization Syndrome” – POPS = “Burst Lung”
Usually occurs with a rapid ascent and breath holding.
Gas in the lung expands rapidly causing alveolar rupture.  (Boyle’s Law)
Alveolar rupture allows air to be forced into other tissues/spaces.
Resulting in escape of air under pressure into the:
Mediastinum = PNEUMOMEDIASTINUM/INTERSTITIAL EMPHYSEMA
Pleural Space = PNEUMOTHORAX
Pulmonary Venous System = ARTERIAL GAS EMBOLISM  (AGE)

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BAROTRAUMA & DYSBARISMS #5

January 22, 2007

ALTERNOBARIC VERTIGO: 

This occurs when there is unilateral pressure difference between middle & inner ear.
More common during ascent then descent.

SYMPTOMS: 

sudden transient vertigo – usually less than one minute.
overwhelming feeling of disorientation.
vertigo may persist on the surface.
accompanied with nausea, vomiting, nystagmus.
no tinnitus

TREATMENT: 

usually not required = transient.
decongestants may speed recovery, 
(occasionally a myringotomy is required.)

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BAROTRAUMA & DYSBARISMS #4

January 20, 2007

EXTERNAL EAR SQUEEZE:   “Barotitis externa”

The External Auditory Canal (EAC) is occluded by cerumen, ear plugs, or wet suit hood. 
As the external pressure increases during descent the “plug” prevents the outside pressure from equalizing in the EAC. 
The EAC becomes edematous and hemorrhagic.
Pain is not relieved by Valsalva or Frenzel maneuver.

PREVENTION:   STOP THE DESCENT and ASCEND to where it is pain free.

TREATMENT:    
Cortisporin Otic Solution or other steroid ear drop.

INNER EAR BAROTRAUMA:  “Barotitis interna”

A pressure differential develops between the middle and inner ears that causes an implosion or explosion of the round or oval windows that separate the inner and middle ear.

SYMPTOMS: 
sudden onset
severe vertigo
roaring tinnitus
nystagmus
fullness of the affected ear
sensorineural hearing loss
does not improve with ascent

TREATMENT:  Antivertigo drugs:
meclizine (Antivert)
diazepam (Valium)
Follow-up with ENT before diving again

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BAROTRAUMA & DYSBARISMS #3

January 18, 2007

BAROTRAUMA:  (Boyle’s Law) DESCENT = compression of the gas.  (volume decreases by 1/2 every 33 fsw)
ASCENT   = expansion of the gas.      (volume increases by 2 every 33 fsw)
(fsw = feet of sea water)

Boyle’s Law – This is why it is an absolute rule that people with asthma cannot SCUBA dive!ASTHMA and SCUBA diving = death.
During the dive some of the air breathed in at depth gets trapped in the alveoli and bronchioles.
Then during ascent that trapped air will expand and burst the alveoli and bronchioles, resulting in burst lungs and DEATH.
         
DESCENT INJURIES:  “SQUEEZE INJURIES”
DESCENT = compression of the gas.  (volume decreases by 1/2 every 33 fsw)

MIDDLE EAR SQUEEZE:  “Barotitis media”
The Eustachian Tube that connects the middle ear to the sinuses is not venting properly.
This prevents the air pressure from the SCUBA tank from getting into the middle ear. 
As a result, there is more pressure outside then in, increasing the pressure against tympanic membrane.
This causes the tympanic membrane (TM) to be pushed inward, causing pain and bleeding of the TM.
Increased pressure in middle ear causes mucosal bleeding and edema of the TM and the middle ear tissues.
If the diver ignores the pain and continues to descend the pressure will increase and the tympanic membrane may rupture inward. 
Water then rushes into the middle ear causing severe vertigo as a result of caloric vestibular stimulation.
 
PREVENTION: 
Valsalva or Frenzel maneuver, to equalize the pressures between the sinuses and the middle ear.   
Long-acting Decongestants/Antihistamines used for 3 days prior to dive.
Inhaled Nasal Steroids used for 7 days prior to dive.

TREATMENT:  
STOP THE DESCENT and ASCEND to where it is pain free.
Decongestant/Antihistamine.
Monitor for onset of Otitis Media.

CONTRAINDICATIONS FOR A DIVE:
Perforated Tympanic Membrane
Sinusitis
Upper Respiratory Tract Infection
Asthma is an absolute contraindication to diving, ever.

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