The effect of free-electron laser pulse structure on mid-infrared soft-tissue ablation: biological effects

Previous studies have shown that changing the pulse structure of the free electron laser (FEL) from 1 to 200 ps and thus reducing the peak irradiance of the micropulse by 200 times had little or no effect on both the ablation threshold radiant exposure and the ablated crater depth for a defined radiant exposure. This study focuses on the ablation mechanism at 6.1 and 6.45 microm with an emphasis on the role of the FEL pulse structure. Three different experiments were performed to gain insight into this mechanism. The first was an analysis of the ablation plume dynamics observed for a 1 ps micropulse compared with a 200 ps micropulse as seen through bright-field analysis. Negligible differences are seen in the size, but not the dynamics of ablation, as a result of this imaging. The second experiment was a histological analysis of corneal and dermal tissue to determine whether there is less thermal damage associated with one micropulse duration versus another. No significant difference was seen in the extent of thermal damage on either canine cornea or mouse dermis for the micropulse durations studied at either wavelength. The final set of experiments involved the use of mass spectrometry to determine whether amide bond breakage could occur in the proteins present in tissue as a result of direct absorptions of mid-infrared light into the amide I and amide II absorption bands. This analysis showed that there was no amide bond breakage due to irradiation at 6.45 microm on protein.     

Serum and myocardial kinetics of amiodarone and its deethyl metabolite after intravenous administration in rabbits

The serum kinetics of amiodarone and its major metabolite the deethyl analogue were studied in rabbits after intravenous administration. The elimination of the drug and the metabolite from serum occurred as a biexponential function. Both compounds exhibited a rapid distribution phase (6.5 and 4.4 min, respectively) and had elimination half-lives of 136 and 235 min, respectively. There was a rapid uptake of both drugs by the myocardium, with maximal concentrations at 5 and 15 min. The myocardial concentrations were higher than the respective serum concentrations and declined with time. There was a wide scatter in myocardium-serum ratios, which ranged from 1 to 11 for amiodarone and 12 to 29 for the metabolite. Neither the drug nor the metabolite produced significant changes in the surface electrocardiogram after intravenous administration. These data suggest that accumulation of the metabolite does not account for the slow onset of action of amiodarone.     

Subdural Empyema

Subdural empyema is a distinct clinical entity not uncommon in Ceylon. Forty-seven cases have been analysed. The commonest sources of infection are otitis media and frontal sinusitis. These empyemas are often complicated by cortical thrombophlebitis, meningitis and intracerebral abscesses. The symptomatology is difficult to differentiate clinically from that of other forms of intracranial suppuration. Percutaneous carotid angiography is the investigation of choice. The treatment consists of surgical evacuation of pus combined with correct antibiotic therapy and skilled nursing. Our mortality of 25·5% was due to uncontrollable associated infections, usually the result of late referral.     

Challenges in increasing access to buprenorphine treatment for opiate addiction

The aims of this study are to assess psychiatrists' comfort using office-based opiate agonist treatment (OBOT) and to identify psychiatrist characteristics associated with OBOT comfort. A random sample of 2,323 AMA Masterfile of Physicians psychiatrists were surveyed through the 2002 APIRE National Survey of Psychiatric Practice (NSSP). Of the 52% responding (N = 1,203), 80.6% (SE = 1.8%) were not comfortable providing OBOT. Males, addiction-certified psychiatrists, and those treating substance abuse patients were more comfortable providing OBOT. These findings highlight significant barriers in providing buprenorphine treatment. Increasing the understanding of specific financing and services delivery barriers that clinicians face is needed to inform the development of effective integrated services models and policies to facilitate OBOT implementation.