Wound healing

David A. Brown1, Nicole S. Gibran1, 2

1 University of Washington, Department of Surgery, USA

2 University of Washington, Regional Burn Center, USA

History of wound care

The science of wound healing occupies a central role in surgical history and continues to represent a common theme for all surgical subspecialties. As early as 1550 B. C., the Ebers Papyrus of ancient Egypt documents the use of a multitude of natural remedies in wound healing. The Egyptians observed that honey, now known to have hygroscopic and antibacterial properties, proved an effective wound dressing. Mild antiseptics such as frankincense, date-wine, turpentine, and acacia gum also found a place in the Egyptian pharmacopeia. The Egyptians are also credited with the first use of sutures for primary wound closure. In a strikingly early use of 20th century medicine, there is documentation of the application of sour or moldy bread to wounds, now understood to harbor antibiotic-producing fungus [1].

Galen of Pergamon, the celebrated surgeon and anatomist, undoubtedly derived a wealth of wound care experience from serving as a surgeon to the Roman gladiators. It was he who first emphasized the importance of maintaining a moist environment for wound healing, although not until recent times has it been understood that wound epithelialization is greatly enhanced in sufficiently hydrated wound beds [2].

The next major breakthroughs in wound care arrived almost two millennia later with the development of the germ theory of disease. Ignaz Phillip

Marc G. Jeschke et al. (eds.), Handbook of Burns

© Springer-Verlag/Wien 2012

Semmelweis, a Hungarian obstetrician, noted that the incidence of puerperal infections was significantly lower when medical students on the ward washed their hands with soap and hypochlorite after attending cadaver dissection. Louis Pasteur stands among the first to apply the microbial theory of disease to healthcare applications. In addition to relating natural phenomena such as the souring of milk the fermentation of sugar to microorganisms, he developed a heat treatment (pasteurization) of milk that prevented the transmission of tuberculosis or typhoid. Robert Koch remains another giant of the era, having formulated a generalized set of criteria for microbial infections, now known as Koch’s postulates [3].

Finally, the English surgeon Joseph Lister is widely credited as the father of antiseptic surgery. Lister’s use of carbolic acid for surgical sterilization is said to derive from his observation that sewage treated with the chemical was less murky than without. He began treating surgical instruments and instituted hand-washing protocols with carbolic acid, which initially led to his suspension from practice, but eventually paved the way for institution of sterile technique in surgery [3].

Types of wounds

The nature of the wound and the manner in which it may heal are fundamentally linked to the mech-

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anism of insult. Injuries by physical agents may be broadly classified into four groups: mechanical trauma, thermal injury, chemical injury, electrical injury, and injury caused by ionizing radiation [4]. These may be considered primary wounds, in contrast to the subtypes of each group are listed in Table 1 with typical characteristics of the wound.

Mechanical injuries take on a variety of forms, such as abrasions, contusions, lacerations, incisions, and puncture wounds. Abrasions are caused by scraping or rubbing and result in removal of superficial skin layers. More severe forms of abrasions are

Table 1. Categories of wounds and various subtypes

avulsions, which involve detachment of skin and possibly underlying tissue, and degloving injuries, in which the blood supply to the detached tissue is compromised. Contusions, or bruises, are caused by blunt trauma and characteristically rupture blood vessels. Extravasation of blood into the affected tissue is evident by skin discoloration, which evolves over time based on the degradation of hemoglobin. Lacerations and incisions refer to tissue separation extending through the skin, with lacerations caused by accidental trauma and incisions caused by purposeful dissection. Puncture wounds are the result of sharp penetration through the skin by an instrument or a projectile. They may extend into deeper structures and/or produce a second wound at the exit site (through-and-through wounds).

Thermal injuries demonstrate a characteristic cutaneous injury pattern, which is divided into three zones based on blood perfusion and tissue viability: zone of coagulation, zone of stasis, and zone of hyperemia. The innermost zone of coagulation represents the irreversibly damaged, necrotic tissue without perfusion. Surrounding the necrotic tissue is an area of moderately burned tissue that may survive or progress to coagulative necrosis depending on the wound environment. This so-called zone of stasis is characterized by increased capillary permeability and vascular damage. The final zone of hyperemia is an area of intense vasodilatation and inflammation that contains viable tissue and is not usually at risk of progression to necrosis [5].

Electrical injuries produce a variety of cutaneous and extra-cutaneous damage that depend upon the strength (amperage), duration, and path of transmission through the body. If the contact time is brief, damage is relatively restricted to the cell membrane and non-thermal mechanisms will dominate the injury pattern. With longer contact time, thermal injury dominates and the entire cell is affected. Higher voltage burns are associated with a greater degree of systemic complications such as ventricular fibrillation, rhabdomyolysis, compartment syndrome, and renal failure [6].

Chemical injuries are grouped by the causative agent, with alkali burns generally known as the most severe. Alkali burns induce fat saponification, profound cellular dehydration, and formation of alkaline proteinates that cause deeper tissue damage.