THE BURN EXAM IS A MICROVASCULAR EXAM

A patient presents with extensive burns to the left hand.  None of the fingers have circumferential burns, but both volar and dorsal aspects do have larger territories affected, with extensive skin sloughing.  How do we use bedside physical examination to guide prognosis and treatment?

The physical examination of burns is essentially a microcirculatory examination for signs of viability.  We are evaluating the viability of the dermis, because this is the organ thath will help mediate wound healing.  It has a plexus of vessels and nerves, so the burn examination assesses neurological and circulatory function of the dermis.

First degree burns are easily defined.  Everything is viable.  It hurts and it is red or pink with normal blanching, which is a sign of increased blood flow.  Every aspect of neurological sensation is normal.  Furthermore, the skin is intact, without blistering.

Third degree burns are, sadly, also quite clear.  The dermis is dead.  The skin is white and leathery.  Sensation to light touch is absent. There are no signs of viability, whether of sensation or of circulation.  Skin that is red but does not blanch means the blood is extravascular, and this is consistent with a third degree burn.  The patient will generally need skin grafting, except for some very small burns <1cm.

Second degree burns, also called partial thickness burns, pose more subtle complexity, and an astute physical examination is needed.  We differentiate superficial partial thickness from deep partial thickness burns.

Superficial partial thickness burns basically just mean first degree viability, but there is some blistering.  The stratum corneum was breached, which separates as a thin blister.  If the tissue beneath has good signs of circulation then this is a superficial partial thickness burn. Signs of good circulation include a healthy pink appearance, normal capillary refill, and normal sensation.  The prognostic importance of a superficial partial thickness burn is that the stratum corneum defense layer has been breached, and topical antibiotics will be needed when the blister breaks.

Deep partial thickness burns mean there are signs of both life and death. On neurological examination, sensation might be present but subjectively diminished.  On circulatory examination, areas are white, but areas are also pink or red and blanch on pressure.   The prognostic importance of a deep partial thickness burn is that prolonged healing is expected and skin grafting may be needed.

The examination changes with time

Because of the intermediate zone of stasis, the classification of the injury may require repeat examination in 1-2 days.  In a full thickness burn, the zone of coagulation looks dead and is dead.  But the intermediate zone of stasis is red, blanches with pressure on day 1, but stops blanching or turns white on day 2 or 3.  Only on day 2 or 3 can we confirm that this is a deep partial thickness burn.  Clues that this might turn out to be the case include early petechiae, a sign that the vessel integrity is compromised.

Additionally, a first degree burn on day 1 might blister by day 2, and then reveal a second degree burn.  Interval follow-up is indicated in all burns where there is any doubt.

Back to the case:

At the bedside, you take a closer look and find areas of pallid appearance, and areas of blanching red.  Sensation is intact and normal.  There are signs of death, and signs of life.  This is a deep partial thickness burn.  Because it affects a critical area (the hand), the patient requires transfer to a burn center.

Take home points:

-repeat examination in 1-2 days is required to reliably classify a burn

-Skin uniformly alive: first degree or superficial partial thickness, excellent prognosis

-Skin uniformly dead: 3rd degree, generally requires skin grafting

-Skin has mix of circulatory/neurologic life and death: deep partial thickness burn, may need skin grafting if wound not expected to heal within 3 weeks


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