Hyperbaric Oxygen in the Treatment of Controlled Laser Induced Thermal Burns
Plastic Surgery Patients
Hyperbaric oxygen therapy (HBO) has established itself as an adjunctive treatment for thermal burns. The physiological damage of these burns is comparable to the thermal burns induced by CO2 Laser resurfacing. Laser resurfacing is a procedure for indications such as sun damage, telangiectasias, eliminating facial rhytides or wrinkles. The elective nature of the procedure allows for any patient with the will power and the financial freedom to undergo this procedure. The purpose of this article is to evaluate and compare thermal burns and controlled laser resurfacing thermal burns, their definitions, treatments and the possible adjunctive treatments. The subject of adjunctive hyperbaric oxygen therapy in the treatment of controlled laser induced thermal burns will also be compared, seemingly due to its role in the treatment of thermal burns.
Laser Resurfacing
Laser resurfacing has recently become the vogue for reducing or eliminating facial rhytides or wrinkles. The evolution of this process has been a long time in coming. Previously, CO2 lasers were used for cutting and destruction of tissues. This is a less controlled use of laser energy. The advent of the computer pattern generator revolutionized the laser industry. Now instead of physician judgment of how long and where to aim the laser, the computer would selectively irradiate the chosen tissue in a uniformly repeatable fashion for a specified period of time. This revolutionized the laser industry and brought about great research into laser biophysics. Thus in the early 1980?s, Anderson and Parrish developed the theory of Selective Photothermolysis (Anderson RR, Parrish JA; Selective photothermolysis; Precise microsurgery by selective absorption of pulsed radiation. Science 220:524, 1983) this theory states that the effects of a laser begin by energy being absorbed at specific sites called chromophores. The chromophore for a CO2 laser is water. Consequently, exposure to a CO2 laser will superheat the water molecule within the cell and thus cause the cell to vaporize. The distribution of laser heating in the skin is not only determined by the depth of laser penetration but also over the period of time that the laser energy was distributed.
Controlling these attributes allows us to ablate tissue and cause a controlled thermal burn, which results in a controlled scarring process that appears to eliminate wrinkles. A certain portion of energy extends into the underlying dermis by thermal conduction. Consequently we are not resurfacing the face with new tissue, we are allowing a controlled scar to evolve. Scars shrink over time, a process called contracture. This controlled contracture is what gives the appearance of youthful un-wrinkled skin.
Thermal effects on tissue are both time and temperature dependent:
42-45 degrees C-reversible protein and membrane changes
50-85 degrees C-structural protein denaturization
75-80-irreversible collagen coagulation
> 100-vaporization of tissue water, then ablation and carbonization.
Complications of CO2 Laser Resurfacing
Laser surgery has exploded in the past decade, both in the number of indications for its use as well as the number of types of lasers. As with all surgical modalities, excellent results are tempered by the existence of complications such as those listed below.
Hyperpigmentation
Postoperative hyperpigmentation can be seen after almost any cutaneous laser procedure, regardless of type. It is more common in patients with darker skin types and is, in the vast majority of cases, a temporary side effect that responds to time and topical bleaching therapy. It is relatively common after CO2 laser resurfacing, where it lasts for an average of 3-4 months.
Hypopigmentation
Postoperative hypopigmentation is also possible, particularly after pigment-specific laser irradiation. In these situations, it is seen more commonly after multiple treatments and is more common in darker skin types. As with hyperpigmentation, this complication is often temporary, although permanent hypopigmentation has been seen. Delayed permanent hypopigmentation has been recognized as a complication particular to CO2 laser skin resurfacing.
Postoperative Blistering
Blister formation (or vesiculation) is due to epidermal thermal damage induced by the laser. Explanations for its development include use of excessive laser fluencies or inadvertent absorption of laser energy due to the increased presence of an epidermal chromophore (e.g., melanin in a tan). The concomitant use of tissue cooling (through a contact chill tip or cryogen spray) serves to protect the epidermis from excessive thermal damage during laser irradiation.
Postoperative Crusting
This undesirable effect is also due to laser-induced epidermal damage (see blistering). Without appropriate postoperative care, crusting is inevitable after cutaneous laser resurfacing procedures.
Milia
Milia are often seen as a normal event in the postoperative course of patients who have undergone CO2 or erbium laser skin resurfacing. Their development may be reduced by application of topical tretinoin or glycolic acid.
Scarring
This is perhaps the most dreaded of laser complications and was relatively common with continuous wave lasers. The risk of scarring with more recently developed pulsed and Q-switched lasers utilizing the principles of selective photothermolysis is far less, but remains possible. Whether atrophic or hypertrophic in type, scarring is always due to excess damage to the dermis. This may be the result of direct laser-induced thermal damage or may arise from complications such as postoperative infection. In general, risk of scarring is low with pigment-specific lasers, non-continuous wave vascular lasers and pulsed hair removal laser systems. Cutaneous laser resurfacing (both CO2 and erbium) carries the highest risk of scarring because of the intended destruction of dermal tissue as well as the increased risk of infection in the de-epithelialized skin. Factors such as the number of passes delivered and energy used may affect the risk of scarring, this complication may be seen even in the hands of the most experienced surgeon.
Definition of Thermal Burns
A thermal burn is an injury caused by exposure to heat sufficient to cause damage to the skin, and possibly deeper tissue. Most thermal burns are caused in one of the following ways, FLAME, HOT LIQUIDS, HOT OBJECTS, FLASH INJURIES and SUNBURN. The burn wound is a complex and dynamic injury characterized by a zone of coagulation, surrounded by an area of stasis, and bordered by an area of erythema. Depending on the severity of the thermal burn the zone of coagulation or complete capillary occlusion may progress by a factor of 10 during the first 48 hours after injury. Edema formation is rapid in the area of injury but also develops in distant, uninjured tissue. There are changes also occurring in the distant microvasculature where red cells aggregate, white cells adhere to venular walls, and platelet thromboemboli occurs. This is a progressive ischemic process which, when set in motion, may extend the damage dramatically during the early days after injury. The continuing tissue damage seen in thermal injury is due to the failure of the surrounding tissue to supply borderline cells with oxygen and nutrients necessary to sustain viability. The impediment of circulation below the injury leads to desiccation, as fluid cannot be supplied via the thrombosed or obstructed capillaries. Topical agents and dressings may reduce, but do not prevent, desiccation of the burn wound and the inexorable progression of the injury to deeper layers. Regeneration cannot take place until equilibrium is reached; hence, healing is retarded. Prolongation of the healing process may lead to excessive scarring. Hypertrophic scars are seen in 4 per cent of patients taking 10 days to heal, in 14 per cent of patients healing in 14 days or less, in 28 per cent of patients taking 21 days, and up to 40 per cent of patients taking longer than 21 days to heal. Rational for Hyperbaric Oxygen Therapy in Thermal Burns
Initial burn therapy must be directed to minimizing edema, preserving marginally viable tissue, enhancing host defenses, and promoting wound closure. Adjunctive hyperbaric oxygen therapy can attack these problems directly, maintaining microvascular integrity, minimizing edema, and providing the essential substrate necessary to maintain viability. The beneficial effects are vasoconstriction & fibroblast proliferation.
Effects of Hyperbaric Oxygen on Thermal Burns
The postulated mechanisms of a beneficial effect of hyperbaric oxygen on burn wounds are decreased edema due to hyperoxic vasoconstriction, increased collagen formation, and improved phagocytic killing of bacteria. In a trial comparing burn treatment with and without hyperbaric oxygen in 16 patients, the healing time was significantly shorter in the group receiving hyperbaric oxygen. Rationale for Hyperbaric Oxygen Therapy in Laser Induced Thermal Burns. The mechanisms of insult in a controlled laser induced thermal burn are similar to the insult in a thermal burn. The controlled laser induced thermal burn has a less dramatic insult due in part to its controlled nature. The extent of thermal damage is generally from 200 to 400 microns, sufficient enough to be classified as a partial thickness burn, but could be less with HBO treatments early on after the surgery. The same pathophysiology of the thermal burn applies to laser burns, the edema, erythema but the ischemia is less severe.
Warly treatment of the controlled laser induced thermal burn has shown a reduction in edema, erythema and promotes faster wound healing. Because the severity of the burn is not considered 20 per cent of the body or life threatening as specified in most HBO literature as an indication for treating the thermal burn wound, the benefits seen in the treatment of the thermal burns are the same benefits seen in the treatment of controlled laser induced thermal burns. Treatment protocols for a less severe thermal burn like the laser induced thermal burn is anywhere from 5 to 10 treatments postoperatively. Each treatment is 90 minutes at 2 atmospheres (equal to 33 feet underwater). It has been observed that the patients whom elect to undergo the hour and a half HBO treatment protocol post laser resurfacing have healed 30 to 40 percent faster than those that don’t do the treatments, and the chances for hypertrophic scarring and other complications are reduced by as much as 80 percent.
Conclusion
Although the treatment for the controlled laser induced thermal burn is not an approved indication by insurance companies for hyperbaric oxygen therapy, the fact remains that the patient can benefit from the treatments. Insurance coverage is a moot point in the reimbursement for this indication due to its elective nature (laser resurfacing is an elective procedure). The research has been extensive in the adjunctive HBO treatment for thermal burns and should pass scrutiny based on its merits alone. The fact is that the treatment for thermal burns has itself not been widely accepted due to the lack of general understanding about Hyperbaric Oxygen Therapy and its benefits. This lack of understanding and ignorance hinders the progression of further research and usage of the treatment for indications that obviously benefit from its adjunctive use.
Remember hyperbaric oxygen therapy is not employed to replace any other treatment modalities but to be used adjunctively with them to get the best possible outcome FOR THE PATIENT. The treatment not only limits the doctor’s liability but also cuts the healing process for the patients thereby shortening the number of post-operative office visits.
(From Hyperbaric Medicine Today.)
Printed with Permission
