Assessment of hemostaseologic alterations induced by hyperbaric oxygen therapy using point-of-care analyzers.

BACKGROUND: Exposure to hyperbaric conditions influences the coagulation system. Thromboembolic events and disseminated intravascular coagulation were observed. OBJECTIVES: To detect the effects of a hyperbaric environment on the human coagulation system using the point-of-care coagulation analyzers Multiplate and ROTEM. PATIENTS/METHODS: 20 patients were included. Each received 90 minutes of oxygen intermittently at 2.4 atmospheres absolute, as per the TS 240-90 wound-healing protocol. Blood samples were taken before and after hyperbaric exposure and ROTEM, Multiplate and standard laboratory assays were subsequently performed. RESULTS: ROTEM showed a significant increase of the maximum clot firmness (EXTEM MCF; p < 0.05) and the thromboelastometric platelet component of the clot firmness (MCF(EXTEM) - MCF(FIBTEM); p < 0.01). Multiplate showed a platelet activation mediated by thrombin (AU TRAP-test; p < 0.05) and by arachidonic acid (AUC ASPI-test; p < 0.01). Standard laboratory assays revealed a lower activated partial thromboplastin time (p < 0.05) and a higher leukocyte count (p < 0.05). No further changes were detected. A t-test was performed after testing if data followed normal distribution. CONCLUSIONS: ROTEM and Multiplate were able to detect an activation of platelets after HBO2 therapy via thrombin and arachidonic acid pathways. Previously reported fibrinolysis could not be confirmed.

Comparative assessment of coagulation changes induced by two different types of heart-lung machine.

The cardiopulmonary bypass (CPB) used in heart surgery has a deleterious effect on hemostasis. The aim of our study was to assess by means of standard laboratory and point-of-care methods changes induced by CPB in coagulation parameters, particularly in platelet function, and to determine whether these changes differ depending on the type of heart-lung machine (HLM) used: minimal extracorporeal circulation system (MECC) and standard HLM. The study enrolled 88 patients scheduled for coronary artery bypass surgery performed on pump. Forty-four interventions were performed with MECC and 44 with standard HLM. Blood was sampled preoperatively, after 30 min on CPB, after weaning from CPB, and 24 h postoperatively. Coagulation and platelet function were assessed using multiple electrode aggregometry (MEA), rotation thromboelastometry, as well as standard laboratory tests. Rotation thromboelastometry and standard laboratory reflected significantly impaired hemostasis after weaning from CPB but no significant differences between the two groups at different time points. Aggregation decreased significantly in both groups as early as 30 min after the institution of CPB (P < 0.05, Mann-Whitney U-test) and recovered within the first 24 h postoperatively, without reaching the preoperative level. Intraoperatively, aggregometry values reflected a significantly more severe reduction of platelet function in standard HLM group than in the MECC group (P < 0.01, ProcMixed test). Our findings suggest that MEA and thromboelastometry reflect impairment of coagulation in cardiac surgery performed on different types of HLM and that platelet function is less affected by MECC than by standard HLM.

Complex myograph allows the examination of complex muscle contractions for the assessment of muscle force, shortening, velocity, and work in vivo.

BACKGROUND: The devices used for in vivo examination of muscle contractions assess only pure force contractions and the so-called isokinetic contractions. In isokinetic experiments, the extremity and its muscle are artificially moved with constant velocity by the measuring device, while a tetanic contraction is induced in the muscle, either by electrical stimulation or by maximal voluntary activation. With these systems, experiments cannot be performed at pre-defined, constant muscle length, single contractions cannot be evaluated individually and the separate examination of the isometric and the isotonic components of single contractions is not possible. METHODS: The myograph presented in our study has two newly developed technical units, i.e. a). a counterforce unit which can load the muscle with an adjustable, but constant force and b). a length-adjusting unit which allows for both the stretching and the contraction length to be infinitely adjustable independently of one another. The two units support the examination of complex types of contraction and store the counterforce and length-adjusting settings, so that these conditions may be accurately reapplied in later sessions. RESULTS: The measurement examples presented show that the muscle can be brought to every possible pre-stretching length and that single isotonic or complex isometric-isotonic contractions may be performed at every length. The applied forces act during different phases of contraction, resulting into different pre- and after-loads that can be kept constant - uninfluenced by the contraction. Maximal values for force, shortening, velocity and work may be obtained for individual muscles. This offers the possibility to obtain information on the muscle status and to monitor its changes under non-invasive measurement conditions. CONCLUSION: With the Complex Myograph, the whole spectrum of a muscle's mechanical characteristics may be assessed.

Assessment of precision and reproducibility of a new myograph.

BACKGROUND: The physiological characteristics of muscle activity and the assessment of muscle strength represent important diagnostic information. There are many devices that measure muscle force in humans, but some require voluntary contractions, which are difficult to assess in weak or unconscious patients who are unable to complete a full range of voluntary force assessment tasks. Other devices, which obtain standard muscle contractions by electric stimulations, do not have the technology required to induce and measure reproducible valid contractions at the optimum muscle length. METHODS: In our study we used a newly developed diagnostic device which measures accurately the reproducibility and time-changed-variability of the muscle force in an individual muscle. A total of 500 in-vivo measurements of supra-maximal isometric single twitch contractions were carried out on the musculus adductor pollicis of 5 test subjects over 10 sessions, with ten repetitions per session. The same protocol was performed on 405 test subjects with two repetitions each to determine a reference-interval on healthy subjects. RESULTS: Using our test setting, we found a high reproducibility of the muscle contractions of each test subject. The precision of the measurements performed with our device was 98.74%. Only two consecutive measurements are needed in order to assess a real, representative individual value of muscle force. The mean value of the force of contraction was 9.51 N and the 95% reference interval was 4.77-14.25 N. CONCLUSION: The new myograph is a highly reliable measuring device with which the adductor pollicis can be investigated at the optimum length. It has the potential to become a reliable and valid tool for diagnostic in the clinical setting and for monitoring neuromuscular diseases.