EFFECT OF BURN INJURY

Local

Regional

Systemic

Local effect

Tissue damage

Heating of tissue result in cell rupture or cell necrosis . Collagen is denatured and damage to peripheral microcirculation occurs .The capillaries are either thrombosed where the damage is severe or in less damaged areas there is increased capillary permeability such that  the tissue becomes edematous and there is external leakage of serous fluid . The essential difference between a partial and full thickness skin loss is the depth of injury .

Inflamation

There is  marked and immediate inflamatory response . In the area least damaged by burning, this is menifest simply as erythema .Mild areas of erythema  resolved within a few hours . More severely damaged tissue may developed a more prolong inflamatory response . Macrophage produces inflamatory mediators or cytokines and phagocytose necrotic cells . Neutrophils and later lymphocytes provide protection against infection .

Infection

The damaged tissue represents a nidus for infection .Burn wound almost inevitably be colonised by micro organism within 24-48 hours and this may remain as a local wound or regional infection .There may be bacteraemia or septicaemia  and metastatic infection may develop at other site .Bacteraemia is a common cause of fatality in severe burn and may occur at any time from the first day until the point when all wound have entirely healed .

Regional problem

Circulation

Limb circulation may be compromised .Direct damage to the main limb vessel is unlikely although it may occur from high tension electric burn .If there is gross edema in a limb following burning , the swelling and tissue tension may lead to venous obstruction .This is particularly where there is circumferential burn tissue (Eschar) which is incapable of distending .There is also possibility of a muscle compartmental syndrome affecting the flexor and or extensor compartment of upper limb and any compartment of lower limb .The circulation of the intrinsic muscles of the hand may be compromised by edema alone and this may lead to ischaemic fibrosis and contracture .

Systemic effect from burning 

Fluid loss

Fluid may be lost from damaged capillaries either by visible external loss or internally into the tissues from edema in the region of burn .In addition there may be  more extensive edema of the region or even in the entire body .It is likely that this is mediated by cytokines acting on the microcirculation .Prevention of hypovolaemia is the most important function in early burn resuscitation . Effective fluid replacement will minimise the risk of  other systemic complications .

Multiple organ failure

There may be progressive failure of renal or hepatic function or heart failure .The precise cause of these complications is uncertain and has often been attributed to fluid loss, toxaemia from infection or uncontrolled over reaction of the inflamatory response to sepsis . Multiple organ failure may however occur without obvious systemic infection .

INHALATION  INJURY

These occurs in those trapped  in enclosed spaces . These are particularly common in association with the burn of the head and neck . Various part of the respiratory tract may be injured . The inhalation of hot gases causes a thermal burn  to the upper air way . This is menefested early by  stridor ,hoarseness , cough and respiratory obstruction. Inhalation of product of combustion causes chemical burn of the bronchial tree and lungs  . This is menifest by hypoxia, acute respiratory distress syndrome and respiratory failure .