Comparison of imaging plates with track detectors for fast-neutron dosimetry

Imaging plate (IP) radiation detectors are widely used in industrial radiography, medical imagery and autoradiography. When an IP is exposed to ionising radiation, some of the energy is absorbed to form a latent image. The energy stored, which is proportional to the dose received, can be liberated by a selective optical stimulation and collected to reconstitute the distribution of the ionising radiation on the IP. In this work, IPs for use in fast-neutron measurements are characterised. The response of our IP dosemeters in conjunction with their reading system was found to be linear in dose between 75 microSv and 10 mSv. This performance is compared with those of dosemeters based on the plastic track detectors PN3 and CR-39.

[Changes of biomechanical parameters in dysplasia of the hip by total hip replacement]

AIM

Dysplastic hips or dislocated hips lead to loss of muscle strength claudication, and finally to coxarthrosis. This study analytically compares the hip joint forces in normal, dysplastic hips and hips after implantation of a hip prosthesis for several positions.

METHOD

The results of 173 total hip replacements in 153 cases of either severe congenital dysplasia or dislocation were analyzed. A 2 dimensional mathematical model of the hip was developed to evaluate the effects of surgically achievable mechanical alterations such as acetabular placement, femoral shaft-prosthetic neck angle, and neck length of the femoral prosthesis.

RESULTS

63 % of the hip prosthesis were implanted on the right, 72 % on the left. Before implantation, the femoral shaft-prosthetic neck angle in mean was 146 degrees +/- 10 degrees, after implantation it was 135 degrees. The hip centre was displaced on in average 10 mm distally. Postoperatively hip joint force was increased 21 %.

CONCLUSION

Minimum joint contact forces occurred when the femoral shaft prosthetic neck angles were small. The loads on the hip were lowered significantly by placing the centre of the acetabulum as far inferiorly and medially as possible. Another important finding is that displacement of the hip centre distally has a great effect on muscle performance and hip joint force.

Diaspirin cross-linked hemoglobin fails to improve left ventricular diastolic function after fluid resuscitation from hemorrhagic shock

In severe hemorrhagic shock, left ventricular (LV) diastolic dysfunction is an early sign of cardiac failure due to compromised myocardial oxygenation. Immediate fluid replacement or, in particular, administration of a hemoglobin-based oxygen carrier (diaspirin cross-linked hemoglobin; DCLHb) improves myocardial oxygenation; therefore, positive effects on LV diastolic function could be expected. The effects of fluid resuscitation from severe hemorrhagic shock with DCLHb were investigated in 20 anesthetized domestic pigs. After generation of a critical left anterior descending coronary artery stenosis (narrowing of the artery until disappearance of reactive hyperemia after a 10-second complete vessel occlusion), hemorrhagic shock (mean arterial blood pressure 45 mm Hg) was induced within 15 min by controlled blood withdrawal and maintained for 60 min. Fluid resuscitation consisted of replacement of the plasma volume withdrawn during hemorrhage by infusion of either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). After completion of resuscitation, an observation period of 60 min elapsed. Measurements of central hemodynamics, myocardial oxygenation, and LV diastolic function were performed at baseline, after induction of critical coronary artery stenosis, after 60 min of hemorrhagic shock, immediately after resuscitation, and 60 min later. While 5 out of 10 animals treated with HSA died within the first 20 min after fluid resuscitation from acute LV pump failure, all DCLHb-treated animals survived until the end of the protocol (p < 0.05). Despite superior myocardial oxygenation due to augmentation of the arterial O(2) content as well as of coronary perfusion pressure, no beneficial effects on LV diastolic function were observed after infusion of DCLHb. Peak velocity of LV pressure decrease (dp/dt(min)) did not reveal significant differences between the two groups. Immediately after completion of fluid resuscitation with DCLHb, the time constant of LV diastolic relaxation (tau) was prolonged when compared with HSA-treated animals (p < 0.05), indicating retardation of early LV diastolic relaxation. Our data suggest that DCLHb fails to improve LV diastolic function after fluid resuscitation from severe hemorrhagic shock. However, positive effects on myocardial perfusion and oxygenation result in a significant reduction of the mortality of severe hemorrhagic shock.

Changes in p(i)CO(2) reflect splanchnic mucosal ischaemia more reliably than changes in pH(i) during haemorrhagic shock

BACKGROUND

Gastric tonometry is intended to reveal alterations in splanchnic perfusion and oxygenation. Based on the tonometric measurement of gastric mucosal partial pressure of carbon dioxide (pCO(2)) and the simultaneous determination of arterial blood gas parameters (bicarbonate concentration [HCO(3-)], pH and pCO(2)), several parameters can be calculated.

AIMS

To identify the most suitable tonometric parameter [gastric mucosal pH (pH(i)), intramucosal pCO(2) (p(i)CO(2)), the difference between tonometric and arterial pCO(2) concentrations (pCO(2) gap), [H+] gap] that reliably reflects gastric hypoperfusion and hypoxia during severe haemorrhagic shock.

DESIGN

Randomised, controlled experimental study.

METHODS

An artificial stenosis of the left anterior descending coronary artery (LAD) was induced. Subsequently, the animals were haemorrhaged to a mean arterial pressure of 45 mmHg, which was maintained for 60 min.

MEASUREMENTS AND MAIN RESULTS

Tonometric measurements were performed in 17 land-race pigs before and after induction of LAD stenosis and after haemorrhagic shock. P values obtained using the Wilcoxon signed-rank testing were used to compare the level of significance for the tonometric parameters and the corresponding arterial blood gas values [arterial pCO2 (p(a)CO(2)), [HCO(3-)], arterial pH (pH(a))]. While induction of critical coronary stenosis did not provoke any changes, all parameters changed significantly during haemorrhagic shock. The lowest P value was found for pH(i) (P=0.00013) followed by [H+ gap] (P=0.0005). P values higher by a factor of ten were found for pCO(2) gap (P=0.00119) and were highest for p(i)CO(2) (P=0.00562). P values of the corresponding arterial blood gas parameters were lower by a factor of ten than the P value of p(i)CO(2).

CONCLUSION

pH(i), pCO(2) gap and [H+] gap are considerably influenced by changes of systemic arterial blood gas values. This is demonstrated by lower P values of the corresponding arterial blood gas values in comparison with p(i)CO(2). Therefore pH(i), pCO(2) gap and [H+] gap seem to indicate more likely systemic changes, whereas p(i)CO(2) appears to reflect disturbances of regional gastric tissue perfusion and oxygenation more reliably than any other derived tonometric parameter.

Diaspirin crosslinked hemoglobin enables extreme hemodilution beyond the critical hematocrit

BACKGROUND

Normovolemic hemodilution is an effective strategy to limit perioperative homologous blood transfusions. The reduction of hematocrit related to hemodilution results in reduced arterial oxygen content, which initially is compensated for by an increase in cardiac output and oxygen extraction ratio. To increase the efficacy of hemodilution, a low hematocrit should be aimed for; however, this implies the risk of myocardial ischemia and tissue hypoxia.

OBJECTIVE

To assess whether hemodilution can be extended to lower hematocrit values by the use of a hemoglobin-based artificial oxygen carrier solution.

DESIGN

Prospective, randomized, controlled.

SETTING

Animal laboratory of a university hospital.

SUBJECTS

Twelve anesthetized, mechanically ventilated pigs.

INTERVENTIONS

Isovolemic hemodilution was performed with either 10% diaspirin crosslinked hemoglobin (DCLHb Baxter Healthcare, Boulder, CO; n = 6) or 8% human albumin solution (HSA, oncotically matched to DCLHb, Baxter Healthcare; n = 6) to a hematocrit of 15%, 8%, 4%, 2%, and 1%.

MEASUREMENTS AND MAIN RESULTS

In both groups, measurements were performed at baseline at the previously mentioned preset hematocrit values and at the onset of myocardial ischemia characterized by critical hematocrit (significant ST-segment depression >0.1 mV and/or arrhythmia). To determine peripheral tissue oxygenation and myocardial perfusion and function, the following variables were evaluated: total body oxygen transport variables, tissue oxygen partial pressure (tPo2, MDO-Electrode, Eschweiler Kiel, Germany) on the surface of the skeletal muscle, coronary perfusion pressure, left ventricular (LV) end-diastolic pressure, global and regional myocardial contractility (maximal change in pressure over time, LV segmental shortening, microsonometry method), LV myocardial blood flow (fluorescent microsphere technique), LV oxygen delivery, and the ratio between LV subendocardial and subepicardial myocardial perfusion. In the HSA group, critical hematocrit was found at 6.1 (1.8)% (hemoglobin, 2 g x dL(-1)), whereas all DCLHb-treated animals survived hemodilution until hematocrit 1.2 (0.2)% (hemoglobin, 4.7 g x dL(-1)) was achieved without signs of hemodynamic instability. Although arterial oxygen content was higher in the DCLHb group at 1.2% hematocrit than in the HSA group at critical hematocrit (i.e., hematocrit, 6.1%; hemoglobin, 2 g.dL-1) neither oxygen delivery and oxygen uptake nor median tPo2 and hypoxic tPo2 values on the skeletal muscle were different between groups. In contrast, subendocardial ischemia was absent in DCLHb-diluted animals until 1.2% hematocrit was achieved. This was attributable to a higher coronary perfusion pressure (65 (22) mm Hg vs. 19 (8) mm Hg; p <.05), higher subendocardial perfusion (4.1 (2.6) mL.min-1.g-1 vs. 1.2 (0.4) mL x min(-1) x g(-1)), and subendocardial oxygen delivery (5.7 (2) mL x min(-1) x g(-1), p <.05) in DCLHb-diluted animals, resulting in superior myocardial contractility reflected by maximal change in pressure over time (3829 (1914) vs. 1678 (730); p <.05) and higher regional myocardial contractility (11 (8)% vs. 6 (2)%; p <.05). An increased LV end-diastolic pressure reflected LV myocardial pump failure in HSA-diluted animals but was unchanged in DCLHb-diluted animals. In the DCLHb group, systemic vascular resistance index remained at baseline values throughout the protocol, whereas coronary vascular resistance decreased. In contrast, both variables decreased in HSA-diluted animals.

CONCLUSION

DCLHb as a diluent allowed for hemodilution beyond the hematocrit value, determined "critical" after hemodilution with HSA (6.1% (1.8)%). Even at 1.2% hematocrit (hemoglobin, 4.7 g x dL(-1)) myocardial perfusion and function were maintained, although at the expense of peripheral tissue oxygenation. This discrepancy in regional oxygenation might be caused by a redistribution of blood flow favoring the heart, which is related to a disproportionate decrease of coronary vascular resistance index during hemodilution with DCLHb.

Extent of microbial contamination in United States pork retail products

To determine the extent of microbiological contamination of U.S. pork, 384 samples of retail pork were collected from 24 stores in six cities, including (i) whole-muscle, store-packaged pork; (ii) fresh, store-packaged ground pork and/or pork sausage; (iii) prepackaged ground pork and/or pork sausage; and (iv) whole-muscle, enhanced (injected or marinated; 60% store-packaged, 40% prepackaged) pork. Additional samples (n = 120) of freshly ground pork and/or pork sausage were collected from two hot-boning sow/boar sausage plants, two slaughter and fabrication plants, and two further-processing plants. Samples were analyzed for aerobic plate counts (APC), total coliform counts (TCC), Escherichia coli counts (ECC), and incidences of Salmonella spp., Listeria monocytogenes, Campylobacter jejuni, Campylobacter coli, and Yersinia enterocolitica. Mean log APC and TCC were highest (P < 0.05) for store-ground pork, while whole-muscle, enhanced products and prepackaged ground products had the lowest (P < 0.05) APC. Mean log APC and TCC were higher (P < 0.05) in samples from the slaughter and fabrication plants than in samples from hot-boning and further processing plants. Mean log ECC were lower (P < 0.05) in samples from further-processing plants compared to slaughter and fabrication plants and hot-boning, sow and boar sausage plants. L. monocytogenes was detected in 26.7% of plant samples and 19.8% of retail samples and was present more frequently in ground products. Y. enterocolitica was detected most often in whole-muscle, store-packaged cuts (19.8%) and in store-ground product (11.5%). Salmonella spp. were found in 9.6% of retail samples and 5.8% of plant samples, while C. jejuni and C. coli were found in 1.3% of retail samples and 6.7% of plant samples. Pork products exposed to the most handling and processing appeared to be of the poorest microbiological quality. These results should be useful in risk assessments that are directed at the identification of actions that could enhance food safety.

Diaspirin-crosslinked hemoglobin reduces mortality of severe hemorrhagic shock in pigs with critical coronary stenosis

OBJECTIVE

To evaluate the effects of resuscitation with a 10% diaspirin-crosslinked hemoglobin (DCLHb) solution on global hemodynamic variables, systemic and myocardial oxygen transport and tissue oxygenation, and contractile function of the left ventricle in an experimental model of severe hemorrhagic shock and critical stenosis of the left anterior descending coronary artery (LAD).

DESIGN

Prospective, placebo-controlled, randomized study.

SETTING

Experimental animal laboratory.

SUBJECTS

A total of 20 anesthetized pigs.

INTERVENTIONS

After implementation of a permanent critical LAD stenosis (ie, maintenance of basal blood flow but absence of reactive hyperemia after a 10-sec complete vessel occlusion), hemorrhagic shock (target mean aortic pressure, 45 mm Hg) was induced within 15 mins by programmed withdrawal of blood and maintained for 60 mins. Subsequently, the volume of plasma lost during hemorrhage was replaced by either a balanced electrolyte solution containing 10 g/dL DCLHb (DCLHb group; n = 10) or an 8 g/dL human albumin solution (HSA) oncotically matched to DCLHb (HSA group; n = 10). Data were collected immediately after the infusion of the different solutions and again after 60 mins had elapsed.

MEASUREMENTS AND MAIN RESULTS

Although five of ten HSA-treated animals died of acute left ventricular failure within the first 20 mins after complete fluid resuscitation, all of the DCLHb-treated animals survived the 60-min observation period after resuscitation (p < .05). This significant difference in mortality is explained by higher coronary perfusion pressure in DCLHb-treated animals (75 +/- 17 vs. 27 +/- 17 torr DCLHb vs. HSA group; p < .05) and persistence of subendocardial ischemia and hypoxia (radioactive microspheres method) in HSA-treated animals on resuscitation particularly affecting the LAD-supported myocardium (subendocardial oxygen delivery: 20 +/- 11 vs. 3 +/- 1 mL oxygen x g(-1) x min(-1), DCLHb vs. HSA group; p < .05). Except for enhanced myocardial contractility immediately on infusion of DCLHb (maximal left ventricular pressure increase: 2373 +/- 782 vs. 1730 +/- 543 torr x sec(-1) DCLHb vs. HSA group; p < .05), no differences were detected between groups concerning the variables of systemic oxygen transport, tissue oxygenation, and regional contractile function of the myocardium (determined with microsonometry).

CONCLUSIONS

Fluid resuscitation with 10% DCLHb solution completely reverses hemorrhagic shock-induced subendocardial ischemia and hypoxia in the presence of compromised coronary circulation and thereby prevents early death after resuscitation.

Effects of primary resuscitation from shock on distribution of myocardial blood flow

Hemorrhagic shock alters heterogeneity of regional myocardial perfusion (RMP) in the presence of critical coronary stenosis in pigs. Conventional resuscitation has failed to reverse these effects. We hypothesized that improvement of the resuscitation regime would lead to restoration of RMP heterogeneity. Diaspirin-cross-linked hemoglobin (10 g/dl; DCLHb) and human serum albumin (8.0 g/dl; HSA) were used. After baseline, a branch of the left coronary artery was stenosed; thereafter, hemorrhagic shock was induced. Resuscitation was performed with either DCLHb or HSA. At baseline, the fractcal dimension (D) of subendocardial myocardium was 1.31 +/- 0.083 (HSA) and 1.35 +/- 0.106 (DCLHb) (mean +/- SD). Coronary stenosis increased subendocardial D slightly but consistently only in the DCLHb group (1.39 +/- 0.104; P < 0.05). Shock reduced subendocardial D: 1.21 +/- 0.093 (HSA; P = 0.10), 1.25 +/- 0.092 (DCLHb; P < 0.05). Administration of DCLHb increased subendocardial D in 7 of 10 animals (1.31 +/- 0.097; P = 0.066). HSA was ineffective in this respect. DCLHb infusion restored arterial pressure and increased cardiac index (CI) to 80% of baseline values. Administration of HSA left animals hypotensive (69 mmHg) and increased CI to 122% of the average baseline value. Shock-induced disturbances of the distribution of RMP were improved by administration of DCLHb but not by HSA.

Integrated optical Ti:Er:LiNbO3 distributed Bragg reflector laser with a fixed photorefractive grating

For the first time to the authors' knowledge, an integrated optical distributed Bragg reflector laser with a fixed photorefractive grating in LiNbO(3) is demonstrated. Sample preparation, grating fabrication, and laser characteristics are reported. The device is pumped by a fiber pigtailed laser diode (lambda(p) approximately 1480 nm) through the Bragg grating in a double-pass configuration, yielding an emission in the backward direction at lambda=1531.7 nm . The laser threshold is 40 mW; as much as 5 mW of output power has been obtained at 110 mW of launched pump power in cw operation.

Heat stress does not modify lactate exchange and removal abilities during recovery from short exercise

Arterial and femoral venous lactate concentrations were measured before, during, and after short intermittent exercise (55-118% of maximal O2 consumption) in thermoneutral (N, 25 degrees C, 10.5 Torr) and hot (H, 45 degrees C, 17.5 Torr) conditions. The thermal load induced significantly higher heart rate and rectal temperature in H relative to N. All the arterial lactate (La) recovery curves were fitted to an equation containing two exponential time functions of the form La(t) = La(0) + A1a(1 - e-gamma 1at) + A2a(1 - e-gamma 2at) where the velocity constants gamma 1a and gamma 2a are the body's overall ability to exchange and remove lactate after exercise, respectively, and t is time. There was no significant difference in these constants, regardless of thermal conditions. The arterial lactate concentration at the end of exercise, the peak lactate concentration during recovery, the amplitudes A1a and A2a of the biexponential function, and the arteriofemoral venous lactate concentration difference during recovery were not significantly different in H relative to N. However, measured and computed arterial lactate concentrations during recovery, especially at the end of the tests, were higher in H (P < 0.04). The more elevated lactate concentrations in H at rest at the end of recovery denote a higher basal lactate production, and they were not due to muscle hypoxia.

Comparative lactate kinetics after short and prolonged submaximal exercise

Arterial blood lactate concentrations were determined in two groups of eleven males before, during and after near 2 W.kg body mass-1 bicycle exercise. One group of subjects cycled for 3 min, whereas the second group exercised for 60 min. All the lactate curves during recovery could be fitted to a bi-exponential time function consisting of a rapidly increasing and a slowly decreasing component. This typical evolution pattern indicates that the two-compartment model which has been proposed to represent the movements of lactate after short exercise applies also to recovery from prolonged exercise. Lengthening exercise duration decreased (respectively 10% and 28%) the value of both velocity constants of the fits to the lactate recovery curves, with the difference (28%) being statistically significant for the velocity constant describing the slowly decreasing part of the curves. This result indicates that extending exercise from 3 to 60 min impairs the ability to remove lactate after the exercise.

Lactate removal ability and graded exercise in humans

Venous lactate concentrations of nine athletes were recorded every 5 s before, during, and after graded exercise beginning at a work rate of 0 W with an increase of 50 W every 4th min. The continuous model proposed by Hughson et al. (J. Appl. Physiol. 62: 1975-1981, 1987) was well fitted with the individual blood lactate concentration vs. work rate curves obtained during exercise. Time courses of lactate concentrations during recovery were accurately described by a sum of two exponential functions. Significant direct linear relationships were found between the velocity constant (gamma 2 nu) of the slowly decreasing exponential term of the recovery curves and the times into the exercise when a lactate concentration of 2.5 mmol/l was reached. There was a significant inverse correlation between gamma 2 nu and the rate of lactate increase during the last step of the exercise. In terms of the functional meaning given to gamma 2 nu, these relationships indicate that the shift to higher work rates of the increase of the blood lactate concentration during graded exercise in fit or trained athletes, when compared with less fit or untrained ones, is associated with a higher ability to remove lactate during the recovery. The results suggest that the lactate removal ability plays an important role in the evolution pattern of blood lactate concentrations during graded exercise.

Blood lactate during constant-load exercise at aerobic and anaerobic thresholds

Venous blood lactate concentrations [1ab] were measured every 30 s in five athletes performing prolonged exercise at three constant intensities: the aerobic threshold (Thaer), the anaerobic threshold (Than) and at a work rate (IWR) intermediate between Thaer and Than. Measurements of oxygen consumption (VO2) and heart rate (HR) were made every min. Most of the subjects maintained constant intensity exercise for 45 min at Thaer and IWR, but at Than none could exercise for more than 30 min. Relationships between variations in [1ab] and concomitant changes in VO2 or HR were not statistically significant. Depending on the exercise intensity (Thaer, IWR, or Than) several different patterns of change in [1ab] have been identified. Subjects did not necessarily show the same pattern at comparable exercise intensities. Averaging [1ab] as a function of relative exercise intensity masked spatial and temporal characteristics of individual curves so that a common pattern could not be discerned at any of the three exercise levels studied. The differences among the subjects are better described on individual [1ab] curves when sampling has been made at time intervals sufficiently small to resolve individual characteristics.