The determination of in vivo human tissue optical properties and absolute chromophore concentrations using spatially resolved steady-state diffuse reflectance spectroscopy.

A method is described for measuring optical properties and deriving chromophore concentrations from diffuse reflection measurements at the surface of a turbid medium. The method uses a diffusion approximation model for the diffuse reflectance, in combination with models for the absorption and scattering coefficients. An optical fibre-based set-up, capable of measuring nine spectra from 400 to 1050 nm simultaneously, is used to test the method experimentally. Results of the analyses of phantom and in vivo measurements are presented. These demonstrate that in the wavelength range from 600 to 900 nm, tissue scattering can be described as a simple power dependence of the wavelength and that the tissue absorption can be accurately described by the addition of water, oxy- and deoxyhaemoglobin absorption.

Photodynamic therapy in a cell culture model of human intimal hyperplasia.

OBJECTIVE: To investigate the effectiveness of photodynamic therapy (PDT) in eliminating proliferating vascular smooth muscle cells (VSMCs). This may have a potential role in reducing restenosis rates clinically. MATERIALS AND METHODS: Human VSMCs were successfully cultured from 15 long saphenous veins (SV) and seven restenotic lesions (RL) removed during revision coronary and peripheral vein graft surgery. Cultured VSMCs were incubated with photofrin at doses of 0-5 micrograms/ml for 48 h, and then exposed to 4 J/cm2 of polychromatic light. Cell destruction was quantified by a colorimetric assay using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. RESULTS: Results are expressed as a mean percentage survival +/- standard error. Cells were minimally affected by either photofrin alone (SV: 95.5% +/- 5.3; RL: 119.8 +/- 4.8) or light alone (SV: 75.38% +/- 3.99; RL: 100.1 +/- 11.0). The combination of 2 micrograms/ml of photofrin and 4 J/cm2 of polychromatic light energy, i.e. PDT, was severely toxic to cells derived from saphenous veins (5.52% +/- 0.85) as well as cells derived from restenotic lesions (9.6 +/- 2.3). These doses are comparable to doses that can be achieved in vivo. CONCLUSION: PDT in the appropriate drug and light doses can eliminate human VSMCs, including those responsible for vascular restenosis.

Trauma in pregnancy.

Trauma is a major cause of maternal death in pregnancy. The pregnant woman who has been involved in an episode leading to her arrival in an accident and emergency department presents with specific problems that often require specialist attention. The correct initial management of such patients should not be beyond the capabilities of an average trauma team and such management is clearly taught as part of the Advanced Trauma Life Support course now available in the UK. This review outlines the physiological changes associated with pregnancy that become important during resuscitation and definitive care. It discusses the presentation and management of specific problems, and the safety--or otherwise--of commonly administered drugs. Only the initial resuscitation of the patient is considered; specialist obstetric care is beyond the scope of the article.

Efficacy of urgent thoracotomy for trauma in patients attended by a helicopter emergency medical service.

Over a 12-month period the Helicopter Emergency Medical Service underwent 1084 missions attending casualties in the London area. Sixteen patients required an emergency thoracotomy for resuscitation, nine of which were performed at the scene and seven in the emergency department. The median injury severity score of these patients was 29.9 (SIR 11.8) of which 11 had suffered blunt injuries. Medical attention at scene was administered 16.2 min (SIR 4.0) following the London ambulance service receiving the emergency call. Significantly longer time was spent attending patients who had a scene thoracotomy (35.1 min SIR 16.4) compared with those in whom the thoracotomy was performed in the casualty department. No patient in this series survived resuscitative thoracotomy. It is suggested that scene thoracotomy be abandoned and emphasis placed upon the rapid transport of patients to an emergency facility. This enables other resuscitative measures in addition to thoracotomy to be applied effectively and concentrated over a brief period by a multidisciplinary team.

On-scene medical decision making and overtriage.

This study examined whether a hospital-based helicopter trauma service led to 'overtriage' of patients back to the multispecialty base hospital. All accident-site triage decisions made during 1991 were studied. Seven of the 574 decisions (1.2 per cent) led to inappropriate movement of the patient to a specialist centre. Twenty-six decisions (4.5 per cent) were based on mechanism of injury alone and the possibility of overtriage by this method is discussed. A trained doctor can select the correct destination for a patient with trauma without inappropriately using the base hospital in preference to local centres.

Iliac artery rupture during percutaneous angioplasty.

Percutaneous transluminal angioplasty of the iliac vessels is a generally safe procedure with good results. A rare but potentially fatal complication is iliac artery rupture; we present such a case with its management and review the literature.

Laser angioplasty with a pulsed NdYAG laser: early clinical experience.

Since December 1986, 40 laser angioplasty procedures have been performed using the energy from a pulsed NdYAG laser, delivering near infrared light (1064 nm) in 100-microseconds pulses of approximately 300 mJ per pulse, directly through a transparent sapphire tipped device. All patients had total occlusion of the superficial femoral artery and symptoms severe enough to warrant surgery, with ulceration or gangrene in eight, rest pain in 14 and severe claudication interfering with life-style in the others. The device was introduced through an antegrade puncture of the superficial or common femoral artery and laser recanalization was followed by attempted balloon angioplasty in all cases. Occlusions were a median length of 15 cm (range 2-35 cm); ten patients had previously undergone failed attempts at conventional balloon angioplasty and four had occluded femoropopliteal grafts. Thirty-seven legs of 34 patients were treated with an average of 60 J (range 10-235 J) with successful recanalization in 27 and immediate reocclusion in seven. The 20 successful recanalizations have been followed up for up to 24 months (median 7 months) with only one late occlusion at 5 months. Failed recanalization was due to poor transmission by the delivery device in the early part of the series (five cases), repeated passage of the device down a collateral branch (four cases), dissection at the site of previous surgery (two cases) or no apparent reason (two cases). Immediate reocclusion was due to very poor run off in patients with severely ischaemic limbs (three cases) or technical difficulties with balloon dilatation (two cases). Complete symptomatic relief was obtained in all the cases of radiologically successful laser angioplasty. Early surgery was required in one case following reocclusion of the artery when an angioplasty balloon failed to deflate, and one patient suffered a skin reaction thought to be due to inadequate removal of the sterilizing solution. A different sterilizing procedure is now followed. Laser angioplasty can reduce the number of patients requiring bypass surgery and improvements in the device and access methods may reduce the number of untreatable cases.

Assessment of a new device for laser angioplasty.

Experimental work has shown that a transparent laser device delivering pulsed energy to an artery results in a smaller area of surrounding damage than does an opaque device with a continuous wave laser. The combination of a transparent ball-tipped device with a pulsed Nd-YAG laser has been investigated. The system delivers pulses of 100 microseconds at a rate of 10 Hz and average energy of 0.5 J per pulse with an energy loss of 5-10% between the output at the laser rail and the fibre tip. The dose/response was measured and showed that on normal aorta under saline the device produces craters with a depth of 5 microns/J and 1.5 mm radius. There is a 100% increase in dose response with diseased aorta and a 50% increase when exposure is carried out under blood. The effect of a varying angle of incidence upon the arterial wall has been measured. Angulation of the device at 10 degrees from the perpendicular reduces the crater depth to 50%, as compared with a 50% reduction at 60 degrees using a bare fibre. As estimated with a thermal camera in air, the device heats up to a maximum of 50 degrees C during a 50 J exposure, compared to 110 degrees C after 5 J for the sapphire device. Artificial circulation experiments were carried out using diseased femoral vessels occluded by a ligature. The new system recanalised 100% of occlusion in straight vessels, and 40% of occlusions in curved vessels at a radius of 2.5 cm.(ABSTRACT TRUNCATED AT 250 WORDS)

Perforation thresholds and safety factors in in vivo coronary laser angioplasty.

Laser angioplasty can cause early (acute perforation) or late (stenosis or aneurysm) complications. To find how much intravascular laser energy can be delivered via a 100 microns core optical fibre passed down a balloon angioplasty catheter without causing angiographic abnormalities up to 10 days later, argon laser energy was delivered percutaneously under radiographic screening to the coronary circulation of 12 normal closed chest dogs. With the balloon inflated, sequential laser pulses were delivered to the same site. Angiograms were recorded before, immediately, and again at one week, after laser delivery. There were two laser-induced perforations (both fatal). Mechanical perforation with the 100 microns fibre occurred four times, but there were no haemodynamic sequelae. To find the acute perforation threshold of similar sized arteries to energy delivered via the bare 100 microns core fibre, the tip of which was held in contact with the luminal surface, 32 argon laser pulses were delivered transluminally in vivo to separate sites in normal rabbit iliac and canine coronary arteries. The acute perforation threshold with energy delivered via the angioplasty catheter lay between 6 and 10 J and that without the balloon angioplasty catheter lay between 3 and 4 J. After delivery of up to 6 J via a balloon angioplasty catheter, there were no angiographic abnormalities at one week. Fibre optic transluminal delivery of laser energy may improve the primary success rate of, and perhaps widen the indications for, coronary angioplasty.

Ankle blood pressure measured by automatic oscillotonometry: a comparison with Doppler pressure measurements.

Oscillotonometry using Dinamap machine was investigated for the measurement of ankle and brachial blood pressures in our vascular practice. It was validated by comparison with intra-arterial pressure measured by transducer. Systolic ankle and brachial pressures in 43 patients were compared using the Dinamap and Doppler techniques, and significant correlation was found. Ankle and brachial systolic, diastolic and mean pressures and ankle/brachial pressure indices for all three pressures were measured in a group of 12 normal subjects supine at rest, and after treadmill exercise, and a range of normal values defined. The main limitation of the Dinamap is its failure to measure pressures below 50mmHg. The Dinamap technique is a noninvasive, simple, reproducible and quick method of measuring ankle and brachial pressures in vascular surgical practice.

The physical properties of tissue ablation with excimer lasers.

The current controversy regarding the interaction between the output of the excimer laser and human tissue concerns the relative importance of photothermal and photoablative effects. Two experiments using an excimer laser on vascular tissue, aimed at defining the precise laser-tissue interaction, were performed. The experiments argue strongly in favor of photoablative effects that result from multiple photon interactions with ablated tissue.

Arterial healing in the dog after intraluminal delivery of pulsed Nd-YAG laser energy.

The application of laser energy to percutaneous recanalization of diseased blood vessels is of interest to vascular surgeons and radiologists. We have examined the effect of pulsed infrared light from a 100 microseconds pulsed Nd-YAG laser on the dog aorta in order to determine the dose response, perforation thresholds and healing properties in vascular tissue. We used 100 microseconds pulses of 0.5 J energy at 10 Hz repetition rate via a 400 micron optical fibre to make 205 craters in 10 dogs at total energies of 5-25 J. The perforation threshold was 15 J in six animals and 20 J in four. The dose response was linear at 10 micron tissue vaporized per Joule delivered. Animals were killed immediately and at intervals of 24 h, 4, 7 and 10 days, 2, 3 and 6 weeks, and 3 and 6 months. Material was retrieved for histology and examined by light and scanning electron microscopy. The tissue exhibited features of laser damage that were less marked than those seen with continuous wave lasers; there was less heat damage surrounding the craters which healed well, even after perforation. This laser is likely to be suitable for human laser angioplasty provided the energy is given in increments of 15 J or less.

Chemical lumbar sympathectomy for ischemic rest pain. A randomized, prospective controlled clinical trial.

The results of a randomized, controlled, prospective double-blind trial of phenol chemical sympathectomy against placebo bupivacaine injection in 41 limbs (24 treatment and 17 control) have been presented. Ablation of the skin potential response was used as an indication of successful sympathectomy. Rest pain was relieved in 83.5 percent of patients at 1 week with a placebo response of 23.5 percent (chi-square test, p less than 0.002). Sixty-six percent of patients remained free from rest pain at 6 months (chi-square test, p less than 0.02). The ankle-brachial systolic pressure index and resting and peak (reactive hyperemic) blood flows were measured in the foot; there was no demonstrable improvement in these hemodynamic factors. Chemical sympathectomy in these circumstances is probably acting as a pain-relieving injection but nevertheless produces useful remission of rest pain in these inoperable but otherwise relatively stable patients. It can also be employed while relevant investigations are carried out before direct arterial surgery.