Hani L. Ashamalla, MD, Kevin Hardy, MD, and Joel W. Goldwein, MD < Last Modified: November 1, 2001
Radiation induced soft-tissue and bone necrosis, while rare, presents a
challenge to the treatment team. High radiation doses, previous surgery
and trauma all increase the risk of the necrosis. When it develops,
pain, disability, progression, or even death due to loss of protective
barriers may result.
Response to antibiotics and/or conservative debridement can be poor.
This is largely due to chronic hypoxia which is characteristic of
the necrotic tissue (Marx). Superimposed
infectious processes can further compromise the situation.
Roughly /3 of osteoradionecrosis occurs spontaneously with soft tissue
breakdown over nonviable bone. Trauma such as tooth extraction, biopsy, or
placement of dental appliances initiates the other 2/3.
Hyperbaric oxygen therapy (HBO), the administration of 100% oxygen under
high pressure, can improve the situation. Such therapy greatly increases
the amount of oxygen availabile to tissue. This is due to the gaseous/fluid
(oxygen/plasma) interface that enhances oxygen absorption and transportation
into the liquid phase of the blood. Under such circumstances, repair of
tissue damaged by high doses of ionizing radiation is facilitated.
Mechanisms of repair can be explained on the following bases;
Stimulation of Angiogenesis:
HBO-induced angiogenesis and fibroplasia have been studied by sequential
biopsies and transcutaneous monitoring. Myers and Marx in 1990 compared the
transcutaneous oxygen (TcO2) measurements of patients in a resting state
breathing room air to measurements breathing hyperbaric oxygen on the
same day. Measurements were taken at two sites: one in the center of the
radiation field, and the second in non-irradiated tissue. Plotting these
a characteristic curve
with three phases: lag, rapid rise, and plateau. The lag phase shows
no measurable angiogenesis but reflects capillary budding. The rapid
rise phase shows an increase to 82% of the non irradiated tissue level.
The geometric rise is due to capillary budding from preexisting vessels
in adjacent tissues. Neovascularisation is accomplished,
converting the hypovascular tissue to a more vascular tissue.
In the plateau phase, the TcO2 measurement levels off at 80%-85% of the
level in nonirradiated tissue. Here maximum angiogenesis was seen and
has been shown to be long lasting by long term follow up of the plateau
phase. Repeat measurements made between 1 and 4 years after
hyperbaric oxygen exposure have shown that the TcO2 values remain elevated.
Stimulation of Neovascularization:
Ketchum et al. and Manson et al. showed that
new blood vessels develop as a
consequence of HBO. A microangiographic technique demonstrated greater
numbers of new blood vessels developing in animal burns subjected to HBO
compared with control animals not subjected to HBO. Furthermore,
histochemical staining showed that lactate levels were reduced and
glucose levels were elevated along the flaps treated with HBO compared
with the control animal flaps.
APPLICATIONS OF HBO:
Reports of early administration of HBO alone without appropriate aggressive
surgical debridement were very disappointing, with a response rate of only
8%. HBO was thus used as an adjunct to conservative therapy, with
excellent response rates and TcO2 measurements reflecting 80%-85%
neovascularization of soft tissue. An increase in the success rate for
bone grafts to irradiated tissues was sought by Marx and Johonson in 1985.
They performed a prospective randomized trial involving
104 patients. Following exposure to 6,400 cGy,patients were randomized
into air breathing control groups and groups treated with HBO at
2.4 ATA (atmospheres absolute), for 90 minutes daily for 20 sessions.
A complication rate of 11% and success rate of 92% were found in the
HBO group, compared with a complication rate of 26% and a success rate
of 66% in the control group.
Marx et al. (Marx, 1985) reported a group of 74 high risk irradiated
patients. Prior to dental surgery, each had received at least 6,800 cGy
to the mandible. In the penicillin control group, 11 patients (29.9%)
developed osteonecrosis, whereas only two patients (5.4%) in
the HBO treated group developed it, and actually both were salvaged
by sequestrectomy and 10 additional treatments.
DELIVERY OF HBO THERAPY TO CHILDREN:
PREPARATION OF THE CHILD:
Puppet or doll pre-enactment.
Standard fire hazard precautions.
Consideration of ventilating tubes especially if upper respiratory
Consideration of accompanying adult.
HYPERBARIC OXYGEN PROTOCOLS FOR OSTEORADIONECROSIS:
Pressure 2.0 - 2.4 ATA.
Frequency of therapy = Daily.
Prophylaxis = 20 pre-op, 10 post-op.
Active ORN = 30 pre-op, 10 post-op.
PATHOGENESIS OF OSTEORADIONECROSIS:
Ionizing radiation causes an obliterative endarteritis to the main
endosteal blood supply of the relevant bone in the radiation therapy field.
Histlogically there is osteoblasts and osteocytes with fatty marrow
Patients receiving radiation to tumors related the mandible
develop osteoradionecrosis at five times the rate of patients
with tumors of other sites.
DOSE OF RADIATION:
The risk of osteoradionecrosis is increased
significantly at dosages of 6000 cGy or more, the risk is increased twofold
for patients receiving greater than 8000 cGy compared to 5000 cGy to
6000 cGy, and is almost five times as great as when the patient
receives 4000 cGy to 5000 cGy.
Dentulous patients are more prone to develop
osteoradionecrosis than are edentulous patients. Furthermore, patients
with dental disease are at twice the risk of dentulous patients patients
without dental disease.
The most common problem during hyperbaric oxygen treatment is
failure of pressure to equalize on the two sides of the eardrum.
This results in squeezing of the delicate vessels of the eardrum,
with pain and bleeding into the middle ear.
Patients with upper respiratory tract infection or congested
mucous membranes are usually placed on prophylactic nasal or
Myringotomies or pressure-equalizing tubes are resorted to
if there is an urgent need for pressurization.
Another ill effect of pressurization is development of mucous
plugs in patients with partly occluded or congested sinuses,
asthma, or obstructive airway disease.
In the sinuses, excruciating pain can result. In the alveoli,
rupture may ensue resulting in tension pneumothorax or even air
embolism in severe cases.
With careful patient selection this complication can be avoided.
If 100% oxygen at 3 atmospheres were used for two to three
hours, CNS toxicity would be produced in a large number of patients.
Present protocols for radiation induced necrosis call for use of
pressures equal to 33 to 45 ft of sea water (2 to 2.4 atm) for 60
to 120 minutes. CNS toxicity is very unusual at pressures less than
2.4 atm . Pulmonary toxicity is also uncommon with fractionated
regimens, allowing time for the pneumocytes to recover from
the toxic effects of oxygen.
Fire is less likely to occur in a multiplace chamber (where
compression is applied to 21% oxygen) than in a monoplace
chamber ( where the compression is applied to 100% oxygen).
RELATIONSHIP OF HBO TO CANCER:
To date there is no evidence linking HBO therapy with increased risk of
tumor formation. Davis and Hunt in 1988 studied 75 animals treated with
HBO and found no increase or progression of tumors in HBO group compared
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