Laser surgery of port wine stains using local vacuum [corrected] pressure: changes in calculated energy deposition (Part II)

BACKGROUND AND OBJECTIVES

Application of local vacuum pressure to human skin during laser irradiation results in less absorption in the epidermis and more light delivered to targeted vessels with an increased blood volume. The objective of the present numerical study is to assess the effect of applying local vacuum pressure on the temperatures of the epidermis and small vessels during port wine stain (PWS) laser treatment. STUDY DESIGN/ MATERIALS AND METHODS: Mathematical models of light deposition and heat diffusion are used to compute absorbed energy and temperature distributions of skin and blood vessels with different diameters (10-60 microm) at various depths (200-800 microm) exposed to laser irradiation under atmospheric and vacuum pressures.

RESULTS

Under 50 kPa (15 in Hg) vacuum pressure, peak temperatures at the inner walls of small diameter vessels (10-30 microm) located 200-300 microm below the skin surface are approximately 10 degrees C higher than those under atmospheric pressure, and peak temperatures in the epidermis of patients with skin phototype II are approximately 5 degrees C lower. In patients with darker skin phototype (IV), the peak temperature at the inner wall of a 10 microm diameter vessel located 200 microm below the skin surface is approximately 5 degrees C higher than that under atmospheric pressure, and the peak temperature in the epidermis is approximately 10 degrees C lower.

CONCLUSIONS

Additional energy deposition in a larger blood volume permits higher temperatures to be achieved at vessel walls in response to laser irradiation. While more energy is deposited in every vessel, temperature gains in small diameter vessels (10-30 microm) are greater, increasing the likelihood of irreversible thermal damage to such vessels. In addition, temperatures in the epidermis decrease because less energy is absorbed therein due to reduced epidermal thickness and concentration of melanin per unit area.

Heterotopic ossification in rehabilitation patients who have had internal fixation of an acetabular fracture

High-energy trauma patients often have multiple injuries and are frequently seen by a physiatrist following their acute care. Acetabular fractures are common in this patient population. Following surgical treatment of acetabular fractures, a very high incidence of heterotopic ossification can occur. We describe 94 patients who underwent posterior surgical fixation of an acetabular fracture. Of these, 87 received heterotopic ossification prophylaxis in the form of irradiation or indomethacin; 5 did not receive prophylaxis. Seven of the 45 patients who were initially started on indomethacin had their medication discontinued for various reasons. Of the 12 patients who did not receive adequate prophylaxis, 5 developed disabling heterotopic ossification. We present our experience with this patient population, and we discuss the importance of adequate prophylaxis for heterotopic ossification.

Anesthetic efficacy of the periodontal ligament injection after an inferior alveolar nerve block

The purpose of this study was to determine the contribution of the periodontal ligament injection (PDL) to the inferior aveolar nerve (IAN) block in human first molars. Using a repeated-measures design, 40 subjects randomly received a combination IAN block and PDL injections of the first molar using 2% lidocaine with 1:100,000 epinephrine and a combination IAN block and mock PDL injections (needle penetration only) at two successive appointments. The first molar and adjacent teeth, and contralateral canine (positive and negative controls) were blindly tested with an Analytic Technology pulp tester at 2-min cycles for 60 min. Profound anesthesia was defined as no subject response at an 80 reading. One hundred percent of the subjects had lip numbness with the IAN block. When the combination IAN/PDL injections were compared with the IAN block, the incidence of successful pulpal anesthesia (80 reading) was significantly greater for the combination injections through the first 23 min of pulp testing. However, after 23 min, there was no increase in anesthetic success by adding the PDL to the IAN injection. We concluded that adding the PDL injection to an IAN block increased the incidence of pulpal anesthesia for the first 23 min in the first molar.

Hydromorphone and hydrocodone interference in GC/MS assays for morphine and codeine

The specificity of a GC/MS assay of morphine and codeine was examined with particular regard to the potential interference due to hydromorphone and hydrocodone, compounds that cross-react extensively in opiate screening tests. A GC/MS method with solid-phase extraction and acetylation or trimethylsilylation was used. The equilibrium between keto and enol forms of the potential interferents was evaluated. Sodium borohydride was tried as a means for converting potential interferents into products that are more clearly separated from morphine and codeine. It was found that borohydride reduction proceeded easily and led to products that could be distinguished from morphine and codeine. Moreover, the quantitation of morphine in the presence of hydromorphone was improved if the borohydride step was included in the analysis.