A comparison of CT lung voxel density analysis in a blast and non blast injured casualty.

INTRODUCTION: Primary blast lung injury (PBLI) is a prominent feature in casualties following exposure to blast. PBLI carries high morbidity and mortality, but remains difficult to diagnose and quantify. Radiographic diagnosis of PBLI was historically made with the aid of plain radiographs; more recently, qualitative review of CT images has assisted diagnosis. METHODS: We report a novel way of measuring post-traumatic acute lung injury using CT lung density analysis in two casualties. One casualty presented following blast exposure with confirmed blast lung injury and the other presented following extremity injury without blast exposure. Three-dimensional lung maps of each casualty were produced from their original trauma CT scan. Analysis of the lung maps allowed quantitative radiological comparison exposing areas of reduced aeration of the patient's lungs. RESULTS: 45% of the blast-exposed lungs were non-aerated compared with 10% in the non-blast-exposed lungs. DISCUSSION: In these example cases quantitative CT lung density analysis allowed blast-injured lungs to be distinguished from non-blast-exposed lungs.

Modelling primary blast lung injury: current capability and future direction.

Primary blast lung injury frequently complicates military conflict and terrorist attacks on civilian populations. The fact that it occurs in areas of conflict or unpredictable mass casualty events makes clinical study in human casualties implausible. Research in this field is therefore reliant on the use of some form of biological or non-biological surrogate model. This article briefly reviews the modelling work undertaken in this field until now and describes the rationale behind the generation of an in silico physiological model.

A model describing the use of a bronchial blocking device and a sheathed bronchoscope for pulmonary aspiration studies in the Gottingen minipig.

The administration of test substances into a single lung, or lung lobe, allows the remaining untreated lung to act as an experimental control and effectively halves the number of animals required in a given experiment. It reduces the likelihood of early fatal pulmonary failure when noxious substances are studied which may lessen the need for replacement animals. However, the ease of substance administration and the subsequent analysis of its effects, for example by bronchoalveolar lavage or bronchoscopy, depend critically on the size of the animal model. The advantages of using minipigs; ease of handling, reduced housing requirements, genetic homogeneity, etc. are reduced if their diminutive size makes lung studies difficult. This article describes the use of a bronchial blocking device and a sheathed bronchoscope which enabled sterile endobronchial substance administration in Göttingen minipigs, and allowed pulmonary aspiration studies to be conducted with each animal acting as its own control.

Vascular access on the 21st century military battlefield.

Timely and appropriate access to the vascular circulation is critical in the management of 21st century battlefield trauma. It allows the administration of emergency drugs, analgesics and rapid replacement of blood volume. Methods used to gain access can include; the cannulation of peripheral and central veins, venous cut-down and intraosseus devices. This article reviews the current literature on the benefits and complications of each vascular access method. We conclude that intraosseus devices are best for quick access to the circulation, with central venous access via the subclavian route for large volume resuscitation and low complication rates. Military clinicians involved with the care of trauma patients either in Role 2 and 3 or as part of the medical emergency response team (MERT), must have the skill set to use these vascular access techniques by incorporating them into their core medical training.

Experience with a low profile bipolar, active fixation pacing lead in pediatric patients.

Continued miniaturization of permanent pacing systems has promoted use of this technology in younger and smaller pediatric patients. Intermedics ThinLine 438-10 active fixation pacing leads (4.5 Fr lead body) were implanted in 26 patients (17 males/9 females; 9.9 +/- 6.9 years). Twenty of 26 patients received dual chamber systems, 6 of 26 patients single lead systems. Each patient has been followed 3 months. Pacemaker analysis at implant and 6 months later evaluated pulse width thresholds at 2.5 V (atrial 0.07 +/- 0.02 vs 0.13 +/- 0.02 ms [P = 0.01]; ventricular 0.08 +/- 0.04 ms vs 0.20 +/- 0.04 ms [P = 0.01]); sensing thresholds (atrial 4.1 +/- 0.41 mV vs 4.0 +/- 4.2 mV [P = NS]; ventricular 9.7 +/- 0.72 vs 9.3 +/- 0.94 mV [P = NS]); and impedance (atrial 345 +/- 12 vs 370 +/- 120 O [P = 0.04]; ventricular 412 +/- 17 vs 458 +/- 190 O [P < 0.01]). One volt lead failed with exit block at approximately 6 weeks. The youngest (9 months to 5 years) and smallest (6.5-18.0 kg) ten patients have each shown by venography to have at least mild venous stenosis at the lead(s) insertion site; five patients demonstrated collateral formation around asymptomatic obstruction, with no thrombus formation. The Intermedics 438-10 ThinLine pacing lead has demonstrated good and stable early postimplant electrical parameters. Angiographic evaluation in our smaller patients has shown evidence for asymptomatic venous obstruction.

The Pediatric Radiofrequency Ablation Registry's experience with Ebstein's anomaly. Pediatric Electrophysiology Society.

INTRODUCTION: Abnormal anatomy and complex electrophysiology in patients with Ebstein's anomaly of the tricuspid valve may confound attempts at radiofrequency ablation (RFA). METHODS AND RESULTS: Data for 65 pediatric Ebstein's patients (9.8+/-5.4 years, 4 months to 20 years; 39+/-25 kg, 5.1 to 108 kg) were obtained from the Pediatric Radiofrequency Ablation Registry. The degree of tricuspid regurgitation (DOTR) and the degree of Ebstein's anomaly were assessed with echocardiography/Doppler. Leading indications were drug refractoriness (24 [37%] of 65 patients) and life-threatening arrhythmia (14 [22%] of 65 patients). For the 65 patients, 82 typical (nondecremental) accessory pathways (APs) (62% right free wall, 34% right septal, and 4% left sided), 17 other supraventricular tachycardias (1 ectopic atrial, 7 AV reentry, 5 Mahaim, and 4 intra-atrial reentry tachycardias), and 1 ventricular mechanism were mapped. Thirty-four (52%) of 65 patients had a single AP (21 right free wall, 10 septal, and 3 left); 19 (29%) of 65 patients multiple APs; 6 (9%) of 65 patients a single AP plus a non-AP mechanism; and 6 (9%) of 65 patients non-AP mechanism(s) only. RFA acute success rates and recurrence rates for right free wall, right septal, and other mechanisms were 79%/32%, 89%/29%, and 75%/27%. Mild DOTR and a body surface area (BSA) < or = 1.7 m2 independently predicted a better acute success rate. BSA < or = 1.7 m2 also predicted long-term success. CONCLUSION: In this patient subset, life-threatening arrhythmias and multiple electrophysiologic mechanisms are commonly encountered during RFA. Mild DOTR and a BSA < or = 1.7 m2 predict a higher acute success rate. While acute success rates are relatively high, recurrence is frequent.

The medical therapy of cardioinhibitory syncope in pediatric patients.

A small percentage of pediatric patients with neurally mediated syncope will have an asystolic response during upright tilt table testing. The purpose of this study is to evaluate the incidence of asystole during tilt table testing, and to assess the outcome of medical management of such patients. Of 398 patients undergoing evaluation for recurrent syncope between January 1989 and 1994, 18 (4.5%) experienced asystole lasting > or = 5 seconds during baseline tilt test. Patients had experienced a mean of four episodes of syncope, with a mean age at the time of tilt test of 11.1 +/- 4.0 years. The median duration of asystole was 10 seconds (range 5-40 s). Treatment was individualized to increased fluids and salt intake (3 patients), metoprolol (8 patients), pseudoephedrine (4 patients), disopyramide (1 patient), or combination therapy with fludrohydrocortisone (2 patients). During a median duration of follow-up of 31 months, no additional syncope was experienced by 78% of patients. Recurrent syncope in 4 patients was associated with either noncompliance or discontinuation of therapy in 3 patients; in 1 patient, increasing the dose of metoprolol was effective in preventing recurrences. We conclude that young patients with recurrent syncope and asystole during tilt test may be safely and effectively managed with pharmacological therapy, without resorting to pacemaker implantation.

Transhepatic access to the atrioventricular ring for delivery of radiofrequency energy.

INTRODUCTION: Transcatheter radiofrequency ablation is an effective, safe treatment of arrhythmias in children. However, despite technical advances, patients with obstructed venous access to the heart have not been candidates for this treatment. METHODS AND RESULTS: Two children (8.2 and 10.9 kg) with complex congenital heart disease, supraventricular tachycardia, and obstructed venous access underwent successful radiofrequency ablation of either a right (one patient) or left (one patient) accessory pathway using the transhepatic route to the heart. CONCLUSION: This experience underscores the usefulness of the transhepatic approach in small patients, in patients with limited venous access, and in patients with complex congenital heart disease.

Incidence of hypertension in infants on extracorporeal membrane oxygenation.

Systemic hypertension has been associated with extracorporeal membrane oxygenation (ECMO) applied in neonatal respiratory failure. To determine the incidence of ECMO-related hypertension, we reviewed blood pressure measurements from indwelling aortic catheters in 31 infants consecutively placed on ECMO. Systemic hypertension (systolic blood pressures greater than 100 mm Hg for 4 or more consecutive hours) developed in 18 of the 31. Causes investigated included the roles of renin secretion, sodium, and colloid loads. There was no evidence of increased plasma renin activities in hypertensive infants (H), when compared with their own pre-ECMO controls or with the nonhypertensive infants (NH). Sodium and colloid loads and their rates of delivery were not different between H and NH. No consistent duration of ECMO was clearly associated with development of hypertension (mean time on ECMO at onset of hypertension, 43.8 +/- 38.5 hours; range, 1 to 142 hours). Demographic information was not statistically significant. Contrary to previous reports, H did not seem predisposed to an increased incidence of intracranial hemorrhage. Development of hypertension during ECMO is not related to increased plasma renin activity, sodium or colloid loads, or their rates of infusion.

Dose-response models for the radiation-induction of skin tumours in mice.

Extensive data on radiation-induced skin tumours in mice were examined using 8 models, all based on the concept that incidences of radiation-induced tumours depend on a combination of two radiation effects: a tumour induction process and the loss of reproductive integrity by the potential tumour cells. Models with and without a threshold were used, in spite of theoretical objections to threshold models. No model fitted well both the epidermal and the dermal tumour data and models which proved to be statistically satisfactory for some of the data were rejected for biological reasons. It is concluded that, for skin tumours, dose-response curves depending on a combination of cancer induction and loss of cellular reproductive integrity are distorted by some special, relatively radio-resistant, factor which we have previously postulated as being involved in radiation skin carcinogenesis.

Incidence of radiation-induced skin tumours in mice and variations with dose rate.

Mice were exposed to weakly penetrating beta-particles from an external source, using 12 different surface doses ranging from 5.4 to 260 Gy and given at four different dose rates from 200 to 1.7 cGy/min. As in previous investigations, both epidermal and dermal tumours occurred with the latter predominating. The lowest surface dose to produce a statistically significant increase in skin tumours was 21.7 Gy, no effect being detected with doses of 5.4-16.3 Gy. The dose-response curves rose steeply when obvious increases occurred. Consideration of these findings and the fact that radiation-induced skin tumours can have an exceptionally long latent period leads to the suggestion that there is some relatively radioresistant factor which normally restrains potential radiation-induced cancer cells in the skin from becoming tumours until the skin is subjected to high local doses. Tumour-induction was unaffected by reducing the highest dose rate by a factor of 10 and the dose-response curves were almost identical. Further reductions of dose rate, encompassing a further factor of 10, in general resulted in fewer tumours.

Reflections on the terms stochastic and non-stochastic as currently used in radiological protection.

The meanings, past and present, of the word stochastic are discussed and related to the way in which "stochastic" and "non-stochastic" may be used to describe the categories of biological damage from ionizing radiation. "Haplocytic" and "polycytic" are suggested as alternatives: these terms allow a classification according to the numbers of cells involved initially and, therefore, according to the basic mechanisms. For more speculative concepts relating to carcinogenesis the word "syncytic" is suggested, together with some potentially useful terms derived from it.

Tumour incidence and longevity in neutron and gammairradiated rabbits, with an assessment of r.b.e.

Rabbits were kept for the whole of their natural life-span (6--9 years) after exposures of 440--1410 rad of gamma-rays or 180--550 rad fission neutrons. Irradiated rabbits did not live as long as unirradiated controls but the difference was statistically significant only after the higher doses of neutrons. Earlier deaths were explained by increased incidences of a wide variety of tumours. The increases were statistically significant for basal-cell tumours of the skin, fibroasarcomas, osteosarcomas and Sertoli-cell tumours of the testis. Other phenomena assoicated with natural ageing were unchanged or decreased in irradiated rabbits. The r.b.e. of the neutrons was assessed as 3--3.5 for tumour induction and 3x5--4x0 for longevity. Comparisons with previous data on acute and subacute effects suggest that the r.b.e. increased linearly with the logarithm of time for 5--2000 days after irradiation.