Animal study on Iung injury caused by simulant segmented shock waves

OBJECTIVE: To study the lung injury caused by segmented shock waves. METHODS: A total of 60 rabbits and 20 rats were used in this study. The process of transmission of shock waves was divided into three phases, i.e., the recompression phase (RP), the decompression phase (DP) and the underpressure phase (UP). And the recompression wave (RW), the decompression wave (DW) a nd the underpressure wave (UW) simulated the three phases, respectively, generated by the equipment designed by us. The RW test, DW test and UW test were respectively applied to the animals. And lung injuries caused by segmented shock waves were discussed. RESULTS: Under the experimental conditions, the RW did not cause obvious lung injury, but the DW could cause different severities of lung injuries. The greater the decompression ranged and the shorter the decompression duration was adopted, the more severe the lung injury was observed. The UW, to some extent, could cause obvious lung injury. CONCLUSIONS: It suggests that lung injury under shock waves probably occurs during the DP primarily. It probably does not cause direct obvious lung injury during the RP, but significantly influences the capability of causing lung injury during the DP.     

Rabbit lung injury induced by explosive decompression

Objective:To study the mechanism of rabbit lung injury caused by explosive decompression.Methos:A total of 42 rabbits and 10 rats were werved as the experimental animals.A slow recompression-decompression test and an explosive decompression test were applied to the animals,respectively.And the effects of the given tests on the animals were discussed.Results:The slow recompression-decompression did not cause an obvious lung injury,but the explosive decompression did cause lung injuries in different degrees.The greater the decompression range was,the shorter the decompression duration was,and the heavier the lung injuries were.Conclusions:Explosive decompression can cause a similar lung injury as shock wave does.The primary mechanical causes of the lung injury might be a tensile strain or stress in the alveolar wall and the pulmonary surface‘s impacts on the inside wall of the chest.     

The effect of extracorporeal shock wave lithotripsy on pancreatic enzymes

In order to assess the effect of electromagnetic shock waves on pancreatic tissue, we studied serum and urinary amylase and serum lipase levels prior to, 1 hour, 1 day and 1 week after extracorporeal shock wave lithotripsy (ESWL) in 150 patients with upper urinary tract stones. A control group consisted of 22 patients with lower ureteric stones who underwent ESWL. All three parameters increased after ESWL (p<0.001), however, this increase was within normal laboratory limits. There was no difference between the right and left renal units. In the control group there was no change of pancreatic enzymes after ESWL. High energy shock waves may cause some elevations of pancreatic enzymes, probably due to altered cell membrane permeability, however, ESWL with an electromagnetic shock wave emitter system does not cause significant injury to the pancreatic tissue.     

High-strain-rate brain injury model using submerged acute rat brain tissue slices

Blast-induced traumatic brain injury (bTBI) has received increasing attention in recent years due to ongoing military operations in Iraq and Afghanistan. Sudden impacts or explosive blasts generate stress and pressure waves that propagate at high velocities and affect sensitive neurological tissues. The immediate soft tissue response to these stress waves is difficult to assess using current in vivo imaging technologies. However, these stress waves and resultant stretching and shearing of tissue within the nano- to microsecond time scale of blast and impact are likely to cause initial injury. To visualize the effects of stress wave loading, we have developed a new ex vivo model in which living tissue slices from rat brain, attached to a ballistic gelatin substrate, were subjected to high-strain-rate loads using a polymer split Hopkinson pressure bar (PSHPB) with real-time high-speed imaging. In this study, average peak fluid pressure within the test chamber reached a value of 1584±63.3?psi. Cavitation due to a trailing underpressure wave was also observed. Time-resolved images of tissue deformation were collected and large maximum eigenstrains (0.03-0.42), minimum eigenstrains (-0.33 to -0.03), maximum shear strains (0.09-0.45), and strain rates (8.4×103/sec) were estimated using digital image correlation (DIC). Injury at 4 and 6?h was quantified using Fluoro-Jade C. Neuronal injury due to PSHPB testing was found to be significantly greater than injury associated with the tissue slice paradigm alone. While large pressures and strains were encountered for these tests, this system provides a controllable test environment to study injury to submerged brain slices over a range of strain rate, pressure, and strain loads.     

The diagnosis of intra-abdominal injury in patients with cervical cord trauma

A review of the records of 288 patients sustaining blunt cervical column and/or cord injuries revealed that twelve (4.2%) had significant intra-abdominal injuries, all occult, and all detected by peritoneal lavage. Three of 58 patients in shock (BP less than 100 mm Hg) with neurologic deficits were found to have intra-abdominal injuries. Shock in another 15 was the result of major associated injuries and/or the loss of sympathetic vascular tone. Thus 40 of these 58 patients (69%) had neurogenic shock. An analysis of the mechanisms of injury and associated injuries indicated that those at risk of having significant intra-abdominal injury are those who have been injured in a vehicular crash and those who have other obvious major injuries that can cause shock. The data indicate that patients not at risk of having intra-abdominal injury can be selected for early attempts at anatomic cervical realignment in an effort to achieve return of neurologic function.     

Prolonged but not short-duration blast waves elicit acute inflammation in a rodent model of primary blast limb trauma

BackgroundBlast injuries from conventional and improvised explosive devices account for 75% of injuries from current conflicts; over 70% of injuries involve the limbs. Variable duration and magnitude of blast wave loading occurs in real-life explosions and is hypothesised to cause different injuries. While a number of in vivo models report the inflammatory response to blast injuries, the extent of this response has not been investigated with respect to the duration of the primary blast wave. The relevance is that explosions in open air are of short duration compared to those in confined spaces.MethodsHindlimbs of adult Sprauge-Dawley rats were subjected to focal isolated primary blast waves of varying overpressure (1.8–3.65 kPa) and duration (3.0–11.5 ms), utilising a shock tube and purpose-built experimental rig. Rats were monitored during and after the blast. At 6 and 24 h after exposure, blood, lungs, liver and muscle tissues were collected and prepared for histology and flow cytometry.ResultsAt 6 h, increases in circulating neutrophils and CD43Lo/His48Hi monocytes were observed in rats subjected to longer-duration blast waves. This was accompanied by increases in circulating pro-inflammatory chemo/cytokines KC and IL-6. No changes were observed with shorter-duration blast waves irrespective of overpressure. In all cases, no histological damage was observed in muscle, lung or liver. By 24 h post-blast, all inflammatory parameters had normalised.ConclusionsWe report the development of a rodent model of primary blast limb trauma that is the first to highlight an important role played by blast wave duration and magnitude in initiating acute inflammatory response following limb injury in the absence of limb fracture or penetrating trauma. The combined biological and mechanical method developed can be used to further understand the complex effects of blast waves in a range of different tissues and organs in vivo.     

In vivo assessment of free radical activity during shock wave lithotripsy using a microdialysis system: the renoprotective action of allopurinol.

PURPOSE: Shock wave lithotripsy is believed to cause renal damage directly through cellular injury from high energy shock waves and indirectly through vascular injury and resultant ischemia, which gives rise to oxygen free radical compounds. The transient and volatile nature of free radicals and derived products makes their detection difficult. Moreover, certain medications may provide a protective effect against shock wave lithotripsy induced renal parenchymal injury. We introduced an innovative microdialysis system for in vivo sampling of interstitial fluids that can be analyzed for free radical mediated lipid peroxidation products after shock wave lithotripsy treatment in the swine model. In addition, this system was used to test the antioxidant or renoprotective action of allopurinol. MATERIALS AND METHODS: Ten juvenile swine were assigned to a nonmedicated control group that underwent shock wave lithotripsy or to a group that was premedicated with allopurinol before shock wave lithotripsy. Each group of animals underwent shock wave lithotripsy to the lower pole of the right kidney and received a total of 10,000 shock waves. Dialysate fluid was collected at 1,000-shock wave increments via probes surgically implanted into the lower pole of the right and left kidneys before lithotripsy. Samples were immediately preserved in liquid nitrogen and subsequently analyzed for the presence and concentration of conjugated diene levels, a measure of lipid peroxidation. Five additional juvenile swine were assigned to a sham treated group that did not undergo shock wave lithotripsy. Dialysate fluid was collected from the lower pole of the right and left kidneys to establish baseline or pre-lithotripsy levels of conjugated dienes. RESULTS: After shock wave lithotripsy conjugated diene levels increased almost 100-fold over that in the right kidneys of the nonmedicated control group. The difference was statistically significant compared to levels in the contralateral untreated kidneys (p <0.01). Right kidneys in the group premedicated with allopurinol did not demonstrate an increase in conjugated diene levels during shock wave lithotripsy. CONCLUSIONS: The results of this study confirm shock wave lithotripsy induced free radical activity as well the antioxidant and protective nature of allopurinol. The newly described microdialysis system enables real-time sampling of interstitial fluids during shock wave lithotripsy. It represents a unique method for assessing free radical formation and evaluating the protective effects of additional antioxidant medications.     

Secondary abdominal compartment syndrome is an elusive early complication of traumatic shock resuscitation

BACKGROUND: The term secondary abdominal compartment syndrome (ACS) has been applied to describe trauma patients who develop ACS but do not have abdominal injuries. The purpose of this study was to describe major trauma victims who developed secondary ACS during standardized shock resuscitation. METHODS: Our prospective database for standardized shock resuscitation was reviewed to obtain before and after abdominal decompression shock related data for secondary ACS patients. Focused chart review was done to confirm time-related outcomes. RESULTS: Over the 30 months period ending May 2001, 11 (9%) of 128 standardized shock resuscitation patients developed secondary ACS. All presented in severe shock (systolic blood pressure 85 +/- 5 mm Hg, base deficit 8.6 +/- 1.6 mEq/L), with severe injuries (injury severity score 28 +/- 3) and required aggressive shock resuscitation (26 +/- 2 units of blood, 38 +/- 3 L crystalloid within 24 hours). All cases of secondary ACS were recognized and decompressed within 24 hours of hospital admission. After decompression, the bladder pressure and the systemic vascular resistance decreased, while the mean arterial pressure, cardiac index, and static lung compliance increased. The mortality rate was 54%. Those who died failed to respond to decompression with increased cardiac index and did not maintain decreased bladder pressure. CONCLUSIONS: Secondary ACS is an early but, if appropriately monitored, recognizable complication in patients with major nonabdominal trauma who require aggressive resuscitation.     

体感诱发电位评价家兔脊髓冲击伤模型的神经机能变化

目的 探讨脊髓冲击伤前后的体感诱发电位的变化,评价家兔神经机能的改变程度.方法 应用改良霍普金森杠杆设备根据冲击波的压力不同(0.40 MPa,0.60 MPa,0.80 MPa)建立不同损伤程度的胸T9-T10脊髓冲击伤模型,12 h后用体感诱发电位仪分别计测家兔脊髓冲击伤前后的体感诱发电位,利用分析软件对诱发电位P...     

冲击波原理和生物学作用

冲击波是压力急剧变化的产物，它能在几纳秒内达到它的压力最大值。冲击波的负相波段可引起空化反应，其物理特性是由量化的参数来表示的。冲击波产生的快速上升的正相压力波和空化反应引起的微泡爆炸喷射会引起细胞膜表面张力增加，一定的张力作用可使细胞膜表面出现微孔或使细胞破裂。冲击波可将生物大分子(蛋白质和核酸)传人细胞内而不使细胞破裂，可应用于抗肿瘤生物分子跨细胞膜转送(定向导入)基因治疗和分析未知基因。能损伤细胞膜但不损伤其它细胞器的最合适剂量的冲击波可诱导人骨髓基质干细胞向骨母细胞分化并诱导骨小节形成，骨髓间充质干细胞的这种特性源于自然选择。体外冲击波疗法已被成功用于治疗骨关节系统的疾病，例如治疗长骨的延迟愈合和骨不连、肱骨外上髁炎、肩部的慢性肌腱钙化症、足底筋膜炎和股骨头坏死。冲击波疗法的首要优点是它的非侵入性和相对很少的并发症。     

Pressure-dependent effect of shock waves on rat brain: induction of neuronal apoptosis mediated by a caspase-dependent pathway

OBJECT: Shock waves have been experimentally applied to various neurosurgical treatments including fragmentation of cerebral emboli, perforation of cyst walls or tissue, and delivery of drugs into cells. Nevertheless, the application of shock waves to clinical neurosurgery remains challenging because the threshold for shock wave-induced brain injury has not been determined. The authors investigated the pressure-dependent effect of shock waves on histological changes of rat brain, focusing especially on apoptosis. METHODS: Adult male rats were exposed to a single shot of shock waves (produced by silver azide explosion) at overpressures of 1 or 10 MPa after craniotomy. Histological changes were evaluated sequentially by H & E staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL). The expression of active caspase-3 and the effect of the nonselective caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK) were examined to evaluate the contribution of a caspase-dependent pathway to shock wave-induced brain injury. High-overpressure (> 10 MPa) shock wave exposure resulted in contusional hemorrhage associated with a significant increase in TUNEL-positive neurons exhibiting chromatin condensation, nuclear segmentation, and apoptotic bodies. The maximum increase was seen at 24 hours after shock wave application. Low-overpressure (1 MPa) shock wave exposure resulted in spindle-shaped changes in neurons and elongation of nuclei without marked neuronal injury. The administration of Z-VAD-FMK significantly reduced the number of TUNEL-positive cells observed 24 hours after high-overpressure shock wave exposure (p < 0.01). A significant increase in the cytosolic expression of active caspase-3 was evident 24 hours after high-overpressure shock wave application; this increase was prevented by Z-VAD-FMK administration. Double immunofluorescence staining showed that TUNEL-positive cells were exclusively neurons. CONCLUSIONS: The threshold for shock wave-induced brain injury is speculated to be under 1 MPa, a level that is lower than the threshold for other organs. High-overpressure shock wave exposure results in brain injury, including neuronal apoptosis mediated by a caspase-dependent pathway. This is the first report in which the pressure-dependent effect of shock wave on the histological characteristics of brain tissue is demonstrated.     

Shock after blast wave injury is caused by a vagally mediated reflex.

OBJECTIVE: Bomb blast survivors occasionally suffer from profound shock and hypoxemia without signs of external injury. We hypothesize that a vagally mediated reflex such as the pulmonary defensive reflex is the cause of shock from blast wave injury. This study was a prospectively randomized, controlled animal study. METHODS: By using a previously described model of blast wave injury, we randomized rats to one of four groups: control, blast-only, bilateral cervical vagotomy plus atropine 200 microg/kg i.p. only, and bilateral cervical vagotomy plus atropine 200 microg/kg i.p. before blast injury. Cardiopulmonary parameters were recorded for 90 minutes after the blast or until death. RESULTS: Bradycardia, hypotension, and absence of compensatory peripheral vasoconstriction, typically seen in animals subjected to a blast pressure injury, were prevented by bilateral cervical vagotomy and intraperitoneal injection of atropine methyl-bromide. Hypoxia and lung injury were not statistically significant between the blasted groups, suggesting equivalent injury. CONCLUSION: Our data implicate a vagally mediated reflex such as the pulmonary defensive reflex as the cause of shock seen immediately after a blast pressure wave injury.     

Effect of acoustic shock waves on clonogenic growth and drug sensitivity of human tumor cells in vitro

Focused acoustic shock waves were studied for their effects on human tumor cell viability, clonogenicity, and sensitivity to chemotherapeutic agents. The elastic shock waves used in this investigation were generated with the Dornier HM3-Lithotripter by underwater spark discharge with fixed electrical parameters employing a voltage of 18 kV and a capacitance of 80 nanoFarads. These waves are characterized by a fast varying compression phase, strong asymmetrical pressure and tension phases, and a maximum amplitude of roughly 10(8) Pascal (kg.m-1 s-2). Doses as high as 2000 focused shocks showed little effect on the viability of two different cell lines. There was, however, a dose dependent inhibition of tumor cell proliferation as determined by the growth of clones in soft agarose. Each of the two cell lines showed a unique degree of colony inhibition by shock waves. It was demonstrated that shock wave effects resulted from elastic shock wave interaction with the cells and were not caused by the emission of ultraviolet light coincident with shock wave generation. Shocks were applied at a rate of 100 minute-1 in a 200 l. water bath, thereby removing the possibility for temperature changes during treatments. After treatment with shock waves it was found that tumor cells became more sensitive to growth inhibition by chemotherapeutic agents. Cisplatin, doxorubicin, and 4-hydroperoxycyclophosphamide were each more effective in blocking cell growth after the target cells had been treated with acoustic shocks. Enhanced efficacies ranged from three to 10-fold potentiation of colony inhibition. These results indicate that weak shock waves, which can be focused to a defined target region, may have utility as a cancer treatment modality either alone or in combination with cytotoxic agents.     

Temporal effects of shock wave lithotripsy.

Previous studies have demonstrated that renal parenchymal injury following extracorporeal shock wave lithotripsy is dependent upon shock wave power as well as the total number of shock waves administered. In order to determine the deleterious effects of temporal versus cumulative doses of shock wave administration, adult female rabbits were divided into five groups receiving either: 1000 shock waves in one session; 2000 shock waves in one session; 2000 shock waves in two sessions, one week apart; unilateral nephrectomy without lithotripsy; or anesthesia only as control population. One month following lithotripsy, renal functional studies for gamma glutamyl transferase and N-acetyl-beta-glucosaminidase revealed persistent enzymuria in the animals treated with 2000 shocks in one session. Pathologic studies in these animals confirmed an increased area of periglomerular and intratubular fibrosis when compared to animals managed by either 1000 shocks or 2000 shocks in divided doses (p less than 0.01). These findings suggest the importance of avoiding single treatments with large doses of shock waves and favor the administration of multiple small-doses of shock waves to minimize renal damage during the treatment of patients with hard or large calculi.     

Shock wave physics

Extracorporeal shock wave lithotripsy has significantly altered the management of symptomatic renal and ureteral calculi. Yet in an effort to limit the potentially harmful effects of shock waves, while still maintaining or maximizing stone fragmentation, one must understand basic shock wave physics. This report presents a brief overview of the physical properties of shock waves and describes three different areas of shock wave physics investigation: measurement of shock wave pressures, assessment of stone fragmentation, and development of a stone phantom to allow the comparison of various lithotripsy devices. It is only through additional study of the basic physics of high-energy shock waves that we will be able to further enhance the clinical benefits of extracorporeal shock wave lithotripsy. Further understanding of the individual characteristics of a shock wave pressure field such as peak positive pressure, peak negative pressure, pulse duration, and size/shape of the focal region will allow the subsequent enhancement of stone fragmentation while minimizing the potential for shock wave injury to surrounding tissues.     

Pathomechanism of shock wave injuries on femoral artery,vein and nerve. An experimental study in dogs

PURPOSE: To study the pathomechanism of shock wave injuries to the femoral artery, vein and nerve in dogs. MATERIALS AND METHODS: High-energy shock wave (0.47 mJ/mm(2) energy flux density) were applied to the right femoral artery, vein and nerve in nine mongrels, and the left side was used as control. Macroscopic examinations including structure integrity, edema, discolouration and extravasation; and microscopic examinations including detachment of the intima layer, disruption of the medium layer, capillary congestion, neutrophil margination and extravasation of the outer layer and the surrounding tissues were performed in 2 h, and in 4 days, respectively, after shock wave application. RESULTS: The most serious injuries included disruption of the medium layer with separation from the adventitia layer of the femoral artery. The injuries to the femoral vein and nerve predominantly involved the outer adventitia layer and the surrounding tissues. Mild nerve bundle swelling was noted in most cases. There were capillary congestion, neutrophil margination and extravasation indicative of inflammatory tissue reaction after shock wave application. CONCLUSION: High-energy shock waves caused serious injuries to the femoral artery, vein and nerve, especially the femoral artery and inflammatory reaction to the surrounding tissues.     

Addition of a water-soluble alpha-tocopherol analogue to University of Wisconsin solution improves endothelial viability and decreases lung reperfusion injury.

BACKGROUND: Reperfusion injury following lung preservation has been associated with free radical formation and subsequent endothelial cell damage. Trolox is a water-soluble analogue of the free radical scavenger alpha-tocopherol. We hypothesized that addition of this form of vitamin E to University of Wisconsin (UW) solution would decrease reperfusion injury and improve lung function after cold ischemic preservation. MATERIALS AND METHODS: Bovine aortic endothelial cells were cultured and stored at 4 degrees C for 12, 24, and 48 h in UW or UW + Trolox (UWT). Endothelial cell viability after storage was assessed by dimethylthiazole tetrazolium cytotoxicity assay. An isolated rat perfused lung (IPL) model was used and lungs were flushed with the respective solutions with cold storage times of 6 and 12 h. Following storage, the lungs were reperfused with fresh blood and lung function was assessed by blood gas analysis, alveolar-arterial gradient, and compliance. RESULTS: There was no difference in endothelial cell viability between UW and UWT after 12 or 24 h; however, UWT had higher endothelial cell viability than UW with 48 h of cold ischemic storage. Using the IPL model, the pO2 was higher with UWT than UW after 6 and 12 h of cold ischemia. The alveolar-arterial oxygen difference was significantly lower for UWT versus UW at 6 h. UWT provided increased compliance at 6 and 12 h of ischemia. CONCLUSIONS: The addition of a water-soluble vitamin E analogue to UW solution resulted in increased endothelial cell viability after prolonged storage and improved whole lung preservation in the postreperfusion period as evidenced by higher oxygenation and increased compliance. These results are clinically relevant as the lung is extremely sensitive to reperfusion injury and UW solution is being increasingly used in lung transplantation and remains the predominant solution in abdominal organ transplantation.     

Pelvic fracture in multiple trauma: classification by mechanism is key to pattern of organ injury, resuscitative requirements, and outcome

Three hundred forty-three multiple trauma patients with major pelvic ring disruption were studied and subdivided into four major groups by mechanism of injury: antero-posterior compression (APC), lateral compression (LC), vertical shear (VS), and combined mechanical injury (CMI). Acetabular fractures which did not disrupt the pelvic ring were excluded. The mode of injury was: MVA, 57.4%; motorcycle, 9.3%; fall, 9.3%; pedestrian, 17.8%; crush, 3.8%. The LC and APC groups were divided into Grades 1-3 of increasing severity. The pattern of organ injury: including brain, lung, liver, spleen, bowel, bladder, pelvic vascular injury (PVASI), retroperitoneal hematoma (RPH) and complications: circulatory shock, sepsis, ARDS, abnormal physiology, and 24-hr total fluid volume administration were all evaluated as a function of mortality (M). As LC grade increased from 1 to 3 there was increased % incidence of PVASI, RPH, shock, and 24-hr volume needs. However, the large incidence of brain, lung, and upper abdominal visceral injuries as causes of death in Grade 1 and 2 fell in LC3, with limitation of the LC3 injury pattern to the pelvis. As APC grade increased from 1 to 3 there was increased % injury to spleen, liver, bowel, PVASI with RPH, shock, sepsis, and ARDS, and large increases in volume needs, with important incidence of brain and lung injuries in all grades. Organ injury patterns and % M associated with vertical shear were similar to those with severe grades of APC, but CMI had an associated organ injury pattern similar to lower grades of APC and LC fractures. The pattern of injury in APC3 was correlated with the greatest 24-hour fluid requirements and with a rise in mortality as the APC grade rose. However, there were major differences in the causes of death in LC vs. APC injuries, with brain injury compounded by shock being significant contributors in LC. In contrast, in APC there were significant influences of shock, sepsis, and ARDS related to the massive torso forces delivered in APC, with large volume losses from visceral organs and pelvis of greater influence in APC, but brain injury was not a significant cause of death. These data indicate that the mechanical force type and severity of the pelvic fracture are the keys to the expected organ injury pattern, resuscitation needs, and mortality.     

The use of polynomial neural networks for mortality prediction in uncontrolled venous and arterial hemorrhage.

BACKGROUND: The ability to rapidly and accurately triage, evacuate, and utilize appropriate interventions can be problematic in the early decision-making process of trauma care. With current methods of prehospital data collection and analysis, decisions are often based upon single data points. This information may be insufficient for reliable decision-making. To date, no studies have attempted to utilize data at multiple time points for purposes of enhancing prediction, nor have studies attempted to synthesize prediction models with data reflecting both large-vessel venous and arterial injuries. Therefore, we performed a retrospective study to examine the potential utility of dynamic neural networks in predicting mortality using highly discretized uncontrolled hemorrhagic shock data. METHODS: One hundred forty-three swine with either grade V liver injuries or 2.8-mm aortotomies had hemodynamic data collected every minute throughout injury and resuscitation. The independent variables used as inputs to the polynomial neural networks (PNNs) included systolic blood pressure and mean arterial pressure (MAP). These inputs were used to predict mortality in individual swine 1 hour after injury using data up to 20 minutes after injury. Survival models were compared based on discrimination power (DP), i.e., where specificity equals sensitivity, and area under the receiver operating characteristic (ROC) curve (c-statistic). The Hosmer-Lemeshow (H-L) statistic was used to measure model calibration. RESULTS: The best PNN model predicted mortality at 60 minutes utilizing data from injury to 20 minutes after injury. This model produced a ROC area of 0.919, a DP of 0.857, and a H-L value of 16.47. A DP of 0.857 means that 85.7% of the survivors are correctly predicted to survive, and 85.7% of the nonsurvivors are predicted to die. MAP of survivors and nonsurvivors were graphed for comparative purposes. As this graph illustrates, the use of MAP alone cannot discriminate survivors from nonsurvivors. CONCLUSION: This study demonstrates that PNN models can effectively harness the dynamic nature of uncontrolled hemorrhagic shock data, despite utilizing data from large-vessel arterial and venous injuries. Utilizing the dynamic nature of hemorrhagic shock data in PNNs may ultimately allow the development of novel decision assist devices.     

The efficacy of a range of contact media as coupling agents in extracorporeal shockwave lithotripsy

OBJECTIVE: To determine if the nature of the coupling agent normally used between the lithotripter and the patient affects the stone fragmentation rate during extracorporeal shock wave lithotripsy. MATERIALS AND METHODS: A jig designed to hold 'phantom' 10-mm stones at the focal point was fixed against the shock wave delivery point of an electromagnetic lithotripter (Dornier Compact, Germany). A layer of either petroleum jelly (Vaseline, Cheeseborough-Ponds Ltd, London, UK) ultrasonography jelly, a eutectic mixture of local anaesthetic (EMLA) cream, Instillagel (Farco-Pharma, Cologne, Germany) or a commercial water-soluble lubricating jelly was placed between the jig and shockwave head, and the number of shock waves required to fragment the stones was recorded. RESULTS: Significantly more shock waves were required to fragment stones when petroleum jelly was used as the coupling agent than with all the other agents under test, whereas significantly fewer shock waves were required when using Instillagel or lubricating jelly than for all other agents. CONCLUSION: The coupling agent used in water-free lithotripsy can affect the stone fragmentation rate and should not be considered inert. Ultrasonography jelly is probably the optimum agent available for use as a lithotripsy coupling agent.