Misleading symptoms and successful noninvasive rewarming of a patient with severe hypothermia (23.1 °C).

Accidental severe hypothermia is a medical emergency in which symptoms may include coma, apnea, pulmonary edema, ventricular dysrhythmia or asystole. Despite optimal treatment, mortality remains high. This article reports a case of severe hypothermia in a geriatric hypothyroid patient, where despite a body core temperature of 23.1 °C the patient presented conscious and with stable vital signs, pronounced motor response, and a Glasgow Coma Scale score of 9. Blood gas analysis (alpha stat at 37 °C) indicated sufficient pulmonary function. A noninvasive rewarming approach proved successful and resulted in discharge without sequelae. This case highlights that symptoms considered pathognomonic for specific stages of hypothermia should be interpreted with great care in clinical practice. Hypothyroidism may have contributed to this uncommon clinical presentation. Body temperature needs to be taken into account when interpreting blood gas analyses. Even at the stage of severe hypothermia, noninvasive forced-air warming enabled rewarming without complications.

[Full-scale simulation in German medical schools and anesthesia residency programs : Status quo]. / Full-Scale-Simulation in der anästhesiologischen Lehre und Weiterbildung in Deutschland : Gegenwärtiger Stand.

BACKGROUND: Simulation has been increasingly used in medicine. In 2003 German university departments of anesthesiology were provided with a full-scale patient simulator, designated for use with medical students. Meanwhile simulation courses are also offered to physicians and nurses. Currently, the national model curriculum for residency programs in anesthesiology is being revised, possibly to include mandatory simulation training. OBJECTIVES: To assess the status quo of full-scale simulation training for medical school, residency and continuing medical education in German anesthesiology. METHODS: All 38 German university chairs for anesthesiology as well as five arbitrarily chosen non-university facilities were invited to complete an online questionnaire regarding their centers' infrastructure and courses held between 2010 and 2012. RESULTS: The overall return rate was 86 %. In university simulation centers seven non-student staff members, mainly physicians, were involved, adding up to a full-time equivalent of 1.2. All hours of work were paid by 61 % of the centers. The median center size was 100 m2 (range 20-500 m2), equipped with three patient simulators (1-32). Simulators of high or very high fidelity are available at 80 % of the centers. Scripted scenarios were used by 91 %, video debriefing by 69 %. Of the participating university centers, 97 % offered courses for medical students, 81 % for the department's employees, 43 % for other departments of their hospital, and 61 % for external participants. In 2012 the median center reached 46 % of eligible students (0-100), 39 % of the department's physicians (8-96) and 16 % of its nurses (0-56) once. For physicians and nurses from these departments that equals one simulation-based training every 2.6 and 6 years, respectively. 31 % made simulation training mandatory for their residents, 29 % for their nurses and 24 % for their attending physicians. The overall rates of staff ever exposed to simulation were 45 % of residents (8-90), and 30 % each of nurses (10-80) and attendings (0-100). Including external courses the average center trained 59 (4-271) professionals overall in 2012. No clear trend could be observed over the three years polled. The results for the non-university centers were comparable. CONCLUSIONS: Important first steps have been taken to implement full-scale simulation in Germany. In addition to programs for medical students courses for physicians and nurses are available today. To reach everyone clinically involved in German anesthesiology on a regular basis the current capacities need to be dramatically increased. The basis for that to happen will be new concepts for funding, possibly supported by external requirements such as the national model curriculum for residency in anesthesiology.

[The basis for well-founded simulations]. / Grundlagen für ein fundiertes Simulationskonzept.

In medical education, simulation is gaining increasing importance for teaching a variety of subjects. A well-founded educational approach is necessary for effective use. In addition to material aspects, simulation environment, curriculum, learning environment, and methods of debriefing have to be considered. The role of a competent instructor should be emphasized and the importance of an elaborate change management process to implement a good concept should not be underestimated.

[Amitriptyline-induced cardiac arrest : treatment with fat emulsion]. / Amitriptylinbedingter Herz-Kreislauf-Stillstand : Behandlung mit Lipidemulsion.

A case of successful resuscitation of a patient with severe amitriptyline intoxication is reported. The measured amitriptyline serum levels far exceeded those assumed to be lethal according to the literature. Resuscitation was successful with the administration of intravenous fat emulsion and the patient recovered without any neurological sequelae.

Transgenic animals in experimental xenotransplantation models: orthotopic heart transplantation in the pig-to-baboon model.

Pig organs are at risk for hyperacute and acute vascular rejection mediated by anti-pig antibodies, mainly binding to the Galalpha(1,3)Gal epitope. Acute cellular rejection is characterized by progressive infiltration of mononuclear cells. There is an ongoing search for immunosuppressive regimens that provide adequate protection against all patterns of xenograft rejection, but have no severe impact on the condition of xenograft recipients. Herein orthotopic heart transplantations were performed from hDAF or hCD46 piglets to nonsplenectomized baboons. Basic immunosuppression consisted of tacrolimus, sirolimus, GAS914, steroids, and ATG. Group 1 received basic immunosuppression. Group 2 was additionally treated with rituximab and group 3 with half-dose cyclophosphamide. Group 4 received cyclophosphamide and an anti-HLA-DR antibody. Three baboons received GAS914 and TPC. Monitoring included the regular assessment of anti-porcine antibodies, blood counts, therapeutic drug monitoring, and graft histology. Two grafts failed due to technical mistakes. In group 1, baboons died after 1 and 9 days. In group 2, maximum survival was 30 hours. In group 3, baboons lived 20 hours, 25 days, and 14 days. Group 4 survival times were 9.5 hours, 5.5 hours, 4 days, 34 hours, and 3 days. An increase of non-Galalpha(1,3)Gal antibodies was observed. Depositions of immunoglobulins and complement revealed a humoral rejection process. No cellular infiltration could be observed. In conclusion, suppressing cellular rejection with half-dose cyclophosphamide together with tacrolimus and sirolimus produced longer graft survival with a good general condition. Prevention of acute xenograft rejection further needs inhibition of non-Galalpha(1,3)Gal cytotoxicity by sufficient depression of B-cell activation.

Attenuation of the near-infrared and red photoplethysmographic signal by different depth of tissues.

Photoplethysmography enables non-invasive investigation of the volume pulse in the microvasculature of patients. We previously have shown that time-discrete analysis enables identification of highly reproducible characteristics of the volume pulse in absolute values. The method would be of particular interest, if the perfusion of deeper tissue layers like the skeletal muscle can be assessed. The aim of the current study was to investigate the attenuation of the photoplethysmographic signal by different tissues and up to which depth of tissue a time-discrete analysis of the photoplethysmographic signal would be possible. For the recordings we used the time-discrete near-infra-red photoplethysmography (NIRP), a reflection photoplethysmograph measuring at wavelengths of 840 nm and 640 nm. In an in vitro circuit filled with bovine blood we generated a typical and exactly reproducible volume pulse. On a platform the NIRP sensor probe was placed above the artificial vessel and recordings of the volume pulse were obtained by varying the sensor-vessel-distance with increasing layers of water, blood-agar or bovine skeletal muscle tissue. - The amplitude of the NIR signal was attenuated to 50% by each layer of 2.01 mm of water, 1.42 mm of blood-agar and 1.05 mm of bovine skeletal muscle tissue. A time-discrete analysis could be performed up to a depth of 15 mm of water, 6 mm of blood-agar and 5 mm of bovine skeletal muscle tissue. - As the photoplethysmographic curve is strongly attenuated even by a few millimetres of water we suggest that the NIRP signal mirrors the perfusion of the superficial tissue layer and mainly originates from the subpapillary capacious plexus. - We conclude that with the equipment used in this study volume pulsations in deeper layers of tissue like skeletal musculature can not be assessed.

Relationship between venous pressure and tissue volume during venous congestion plethysmography in man.

1. Venous congestion strain-gauge plethysmography enables the non-invasive assessment of arterial blood flow, fluid filtration capacity (Kf), venous pressure (Pv) and isovolumetric venous pressure (Pvi) in man. One of the major assumptions of this technique, that cuff pressure (Pcuff) applied to the limb equals Pv at the level of the strain gauge, was tested in this study. 2. In nine healthy male volunteers (mean age, 29.3 +/- 1.2 years) the saphenous vein was cannulated with an 18-gauge catheter proximal to the medial malleolus. The subjects were supine and Pv was continuously measured during the application of small step (8-10 mmHg) increases in congestion Pcuff (up to 70 mmHg). Pcuff, changes in limb circumference and Pv were recorded by computer for off-line analysis. Since the determination of Kf is influenced by the changes in plasma oncotic pressure, venous blood samples were obtained at the start of the study, when Pcuff was raised to 30 mmHg and again to 65 mmHg and 4 min after deflation of the cuff. 3. The relationship between Pv and Pcuff was linear over the range of 10-70 mmHg (n = 9, 69 measurements, slope 0.91, r = 0.97, P << 0.001). The non-invasively measured calf Pv, based on the intercept of the relationship between the vascular compliance component (Va) and Pcuff, was 8.0 +/- 0.4 mmHg, which was not significantly different from the corrected invasively measured Pv value of 8.8 +/- 0.3 mmHg (P = 0.08). 4. Venous blood lactate and haemoglobin concentrations, as well as colloid osmotic pressure, total protein and albumin concentrations were unchanged throughout the protocol, whereas significant decreases in PO2 and blood glucose concentration were observed when Pcuff reached 65 mmHg. Assuming a constant oxygen consumption, this may suggest a reduction in tissue perfusion. 5. This study demonstrates the close correlation between Pcuff and Pv in the saphenous vein. Since the small congestion Pcuff step protocol does not cause significant increase in plasma oncotic pressure, we conclude that Pv, as well as Kf, can be accurately determined with this venous congestion plethysmography protocol.

Cardiovascular monitoring of elective aortic aneurysm repair using methods of chaos analysis.

INTRODUCTION: Biological signals like arterial blood pressure (ABP) and electrocardiograms are usually displayed in a linear fashion. The often very complex structure may, however, be better described by phase space plots and time-delayed vectors, enabling an advantageous display of the dynamics contained in the signal. The potentials of such a display were investigated during elective aortic aneurysm repair, where profound haemodynamic changes frequently occur. METHOD: The peripheral volume pulse was recorded at a digit using noninvasive near infrared photoplethysmography (NIRP). All patients (n = 20, mean age 72.8 years) were invasively monitored using arterial and Swan Ganz catheters. The ABP signal was continuously recorded with a computer (sample rate 128 Hz). Two different phase space plots, [x(t), y(t + 8/128 s) and x(t), d(x(t + 8/128 s) - x(t))/dt] were calculated for the NIRP and the ABP signals and continuously displayed. The stability was subjectively assessed and the fractal dimension calculated using the 'Hausdorff dimension'. The correlation between stability, fractal dimension and frequently used parameters of patient monitoring were investigated. RESULTS: All patients included in the study had an uncomplicated operation. Cardiac index (CI) and oxygen delivery (DO2) increased, and systemic vascular resistance (SVR) decreased following declamping of the aorta. The ABP signal was generally more stable. After declamping of the aorta, 14 of 16 NIRP signals became unstable, and 9 of 14 ABP signals destabilised. The time required for stabilisation of the signal varied between the individual patients. Thirty minutes after declamping, 11 of 12 ABP signals were stable, whereas 3 out of 9 NIRP signals still revealed an unstable pattern. A fractal dimension was calculated by box counting, which revealed a linear regression over two orders of magnitude in a log-log plot (Hausdorff dimension between 1.19 and 1.71). The mean fractal dimension for NIRP was significantly higher than that of the ABP signal. On clamping and declamping of the aorta, a trend to a higher fractal dimension (p = 0.08) was observed for both signals analysed. No correlation was observed between the fractal dimension and ABP, SVR index, CI, DO2 index and oxygen consumption. DISCUSSION: The dynamic changes of the signals were emphasised when they were displayed as phase space plots calculated by time-delayed vectors. The time series of the signal revealed a fractal dimension, and the observed increase at the critical time points of the operation, where the need for cardiovascular regulation is most pronounced, support the contention that a physiological system based on non-linear behaviour may enable a rapid response to haemodynamic challenges. An on-line display of phase space plots calculated by time-delayed vectors may in future provide a valuable method of monitoring for high-risk patients.

Time discrete, near infrared photoplethysmography (NIRP) for non-invasive investigation of the volume pulse in man.

UNLABELLED: In pulse oximetry the principles of photoplethysmography are used for determination of heart rate and in some devices to also display the volume pulse. It has been suggested, that a more detailed analysis of the signal may allow quantitative analysis of peripheral hemodynamic events. We describe a new computer assisted time discrete analysis of the volume pulse, studying its reliability and the method s fundamental assumption of a linear relationship between changes in amplitude and changes in time sequences of the volume pulse. METHOD: In a finger clip two diodes emit near infrared (840 nm, NIR) and red light (640nm, RED) into the finger tip, where it is remitted mainly by the erythrocytes. 70 sec of recorded signal is filtered and the resulting volume pulse analysed off-line using a computer. On each volume pulse the time of the first (Tmax), the second maximum (time of dicrote, Td) and the duration of the volume pulse (Tp) are measured and the mean values displayed. In addition, the fundamental arterial oscillation Tag = Td - Tmax and all the above values in relation to Tp are calculated. Using NIRP, 54 healthy young volunteers (19 female, mean age 27.0 +/- 3.4 years) were studied and the individual mean values calculated from 960 measurements. The reliability during 10 repetitive measurements was investigated in 26 of the 54 volunteers. In 12 subjects 5 repetitive measurements were obtained from each finger and compared with each other. In 11 subjects the linear relationship between amplitude and time sequence was tested on > 30 000 single volume pulses. The finger clip photoelectrode was levelled with the right atrium in all measurements, skin close to the clip and room temperature were recorded. RESULTS: From the mean individual values the following time discrete values were calculated for the NIR signal (n = 41): Tp = 882.3 +/- 142.6 ms, Tmax = 214.8 +/- 28.3 ms, Td = 452.7 +/- 32.4 ms, Tdec = 667.4 +/- 133.6 ms, Tag = 237.9 +/- 36.3 ms, Tmax/Tdec = 0.34 +/- 0. 07, Td/Tdec = 0.7 +/- 0.11. For each parameter the individual standard deviation during 10 repetitive measurements (26 subjects) ranged between 2.2 and 6.1%. The time sequences found were not significantly different between the individual fingers. A linear relationship between changes in time sequence and changes in amplitude was found in all tested subjects (mean r = 0.96). CONCLUSION: These results show, that the values obtained with time discrete NIRP are highly reproducible and show an individual SD of less than 6.5% under steady state conditions. The linear relationship between time sequence and amplitude found in the present study has to be confirmed in further studies on patients with pathologies of the macro- and microcirculation.