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The weak point of the field network is represented by E12 low-speed relay links. The situation requires savings of the bandwidth. For this purpose, the necessary bandwidth for voice transmission up to the level of the physical layer has been analyzed. As a suitable solution of network throughput increase, we propose the change of a Voice Payload Size. After finding the optimal Voice Payload Size, tests were carried out to verify the impact of the Voice Payload Size on call quality. A packet loss rate is chosen as a parameter for modelling real traffic. To obtain the expected voice quality, the E-model according to the G.107 Recommendation is applied. The theoretical results are compared with practical measurements, when using the proprietary Cisco Packet Loss Concealment algorithm to evaluate the voice quality. The results obtained have confirmed the suitability of the solution. [ABSTRACT FROM AUTHOR]

Aimed sympathetic denervation of the heart, i. e. bilateral removal of the stellate ganglion Th 1-Th 3 was used in Czechoslovakia since 1981 in eight patients who were followed up for prolonged periods. The patients were operated on account of angina at rest which caused deterioration of the quality of their lives. In case of extensive affection of the coronary arteries surgical treatment was not feasible and pharmacological treatment did not bring relief. At the time of a five-year check up 7 patients survived. All patients reported relief and their efficiency during ergometry improved. Four of the patients worked for several years. The authors discuss whether the above treatment is still justified.

One of the methods of donor heart protection against ischemia is a substantial lowering of temperature of the heart perfused with cardioplegic solution (CS). The achieved conservation of energetically rich compounds, however, does not guarantee the full restoration of heart function during reperfusion. Another possibility for heart preservation is repeated application of CS at 20 degrees C. This variant was tested in our experiments on isolated rat hearts perfused under constant pressure with the Krebs-Henseleit solution according to Langendorff. During global ischemia (180 min at 20 degrees C) we applied the St. Thomas Hospital CS lx or 4 x at 60 min intervals. During the ischemia, glycogen, ATP, lactate, Na+, K+ were assessed in the heart. The heart injury was monitored as the release of lactate dehydrogenase (LD) during the 60 min reperfusion. Repeated CS perfusion of the heart during ischemia lowers the contents of lactate and maintains ATP and glycogen content at elevated levels throughout ischemia. The improved condition of the heart after repeated CS application demonstrated as prevention of the gain of Na+ in the cells at the end of ischemia as well as after reperfusion. This was associated with reduced intracellular potassium depletion and LD release into the perfusate.

The following results were obtained in an experimental study in the dogs in general pentobarbital anaesthesia: Lidocaine type antiarrhythmics (lidocaine, Xylocaine ASTRA, Ethmozin USSR) administered shortly before artery ligation have a pro-fibrillation effect. This effect is indirectly proportional to the ischaemic focus development. A 3rd-generation beta blocker with intrinsic sympathetic activity (celiprolol, Selectol Chemie-Linz) had the same electrostabilizing effect on the ventricles in the acute phase of ischaemia as a 1st-generation beta blocker (metipranolol, Trimepranol SPOFA). The 3rd-generation blocker, however, stopped short of provoking a drop in the heart rate invariably associated with the 1st-generation beta blocker. The analgesic fentanyl (G. Richter) in combination with benzodiazepine (m,idazolam, Dormicum Hoffmann-La Roche) inducs analgosedation. In this way the dose of the analgetic can be reduced and yet the analgesia and electrostability of the heart remain the same. Due to the lower dose of the analgesic there is a lesser decrease in the heart rate and blood pressure. Analgosedation can be discontinued by administering an antagonist-agonist of benzodiazepines (flumazenil, Anexate Hoffmann-La Roche) or an antagonist of potent analgesics (butorphanol, Beforal SPOFA) without the risk of eliminating, at the same time, the electrostabilizing effect of analgosedation on the ischaemically damaged ventricles of the heart. For the prevention of sudden coronary death due to ventricular fibrillation in the acute phase of local myocardial ischaemia we can, on the basis of our experimental results, recommend analgosedation and the use of beta blockers with intristic sympathetic action. The use of lidocaine antiarrhythmics may lead to a reduction in the electric stability of the heart ventricles the ischaemic focus is developing under a certain "critical" blood level of the antiarrhythmics.

In a group of cadaveric kidney transplantations the problem of the dependence of the functional development of the graft on the function of donor kidney before explanation and on the total time of ischaemia in the immediate postoperative period was investigated. Based on the plasma concentration of endogenous creatinine (PKr), urea (PUrea) and the total ischaemic time (GI), the early function of the graft cannot be predicted. On the contrary, the values of PKr, GI and the kidney index (NIKI = PKr x GI) allow an accurate prediction that the early function of the graft will not be sufficient. Early function of the graft is not likely to develop when PKr is higher than 160 mumol/l, total ischaemic time is longer than 30 hours and the NIKI is over 3,500. Severe alterations in the level of serum potassium (SK) occurred in 61.4% of the donors. In cases where SK was 3.0 mmol/l or less, early function of the graft did not develop in 82.3%. With high probability haemodialysis was necessary. More pronounced alterations of the level of SNa occurred in more than 60% of the donors. When SNa was 125 mmol/l or less, early function of the graft did not develop in 76%. Diuresis over 400 ml/h increased significantly the number of early nonfunctional grafts. In cases where fractional sodium excretion (FENa) was over 5%, early function of the graft did not develop. With a FENa less or equal to 1%, early function of the graft was most likely to develop.

Using a model of local myocardial ischaemia in the dog, the authors studied the electrostabilizing effect of a combination of the benzodiazepine midazolam (Dormicum Hoffman--La Roche) and the strong narcotic analgesic drug Fentanyl (Richter). The electrostabilizing effect was assessed using the method of ventricular fibrillation threshold (VFT) measurement. The same increase in the fibrillation threshold as that induced by the administration of midazolam or fentanyl alone was achieved by a combination of both drugs given, however, in reduced doses. The electrostabilizing effect of benzodiazepines and potent analgesics is enhanced by their simultaneous administration. At the same time, the adverse side effects observed on the administration of fentanyl alone (bradycardias, hypotension, cardiac blockade) due to the prevalence of parasympathetic drive, are reduced. Simultaneous administration of a benzodiazepine and an analgesic has become a modern technique, in anaesthesiology, so-called analgosedation. Experiments have shown the technique, in addition to the generally recognized analgesia, sedation and anxiolysis, exerts electrostabilizing effects on the myocardium damaged by ischaemia. The authors therefore recommend analgosedation in the drug treatment of acute myocardial infarction.

The authors summarize their experience with intraaortic balloon counterpulsation (IABC) at the Institute for Clinical and Experimental Medicine between 1978-1984. A total of 756 cardiac surgery procedures were performed for ischaemic heart disease (IHD), and 266 procedures for rheumatic heart disease (RHD). Of patients operated on for IDH, IABC was used in 38 (5%) and, of those undergoing surgery for RHD, in 38 cases (14%). Overall, IABC was employed in 76 patients, i.e., 7%. Ventricular assistance using IABC was successful in 55% of patients. The technique was significantly more successful in IHD (68%) than in RHD (42%) patients. IABC was less successful in IHD patients suffering myocardial infarction intraoperatively. Moreover, the success of IABC depended on its early initiation. Eleven patients (14%) developed complications associated with IABC. The data do not differ from results reported by world's leading centres.

Premature ventricular contractions are relatively often encountered in patients after surgical treatment of ischaemic heart disease. Mercurascan (MSC), given at 0.05 mg/kg of body weight, favourably affected both the incidence and duration of arrhythmia. Unlike other antiarrhythmics, MSC did not affect the heart rate nor blood pressure. Postoperative treatment of ventricular arrhythmia with MSC is a promising procedure and merits further clinical and experimental investigation.

The pathogenesis of electrical instability of tissue in the earliest phase of ischaemia is well known. Convincing results in the prevention of ventricular fibrillation at this stage have been obtained only by agents inhibiting sympathetic activation of the heart, or by agents significantly prolonging the refractory period of heart cells. On the other hand, it was documented that sodium channel inhibitors are not suitable for prevention of electrical instability in the early phase of ischaemia and can, on the contrary, aggravate it. A question which is still unresolved and deserves further research is the effect of calcium channel inhibitors and of agents acting directly on the metabolism of ischaemic tissue.

By means of a Immunoskintest Sevac kit the authors examined 99 patients who were subjected to heart surgery with extracorporeal circulation. In the group of patients with an index of more than 1.0 were 7% postoperative infectious complications, in the group with an index smaller than 1.0 there were 19% and in the group of patients with anergy and relative anergy there were 66% infectious complications after operation. The authors consider as risk patients those where anergy or relative anergy was proved, as well as patients with an index lower than 1.0 and a weak response to 2-3 antigens. In risk patients it is essential to make a detailed immunological examination and to correct in a suitable way their immunodeficiency, e. g. by administration of transfer factors. From the results ensues moreover that the immune response of patients, and thus also the development of postoperative infectious complications, is related to the patient's age and the presence of rheumatic disease.

In 70 cadaverous donors the authors examined 2 hours before collection of organs the serum and urinary electrolyte levels and the creatinine and urea levels. Serious hypokaliaemia (less than 3.0 mmol/l) was found in 24.5% of the donors, hyperkaliaemia (more than 6.0 mmol/l) in 11.4%. Hyponatraemia (less than 125 mmol/l) was present in 11.4%, hypernatraemia (above 160 mmol/l) in 18.6% of the donors. Hyperchloraemia (above 130 mmol/l) was recorded in 22.8 percentage of the donors. In cases where SK less than or equal to 3.0 mmol/l, early functional development of the graft did not occur in 82.3% (p less than 0.001), in cases where SNa less than or equal to 125 mmol/l in 75% (p less than 0.01). When the value of FENa greater than or equal to 5%, early restoration of the graft did not occur in 81.3% of the cases (p less than 0.01). Conversely when FENa less than or equal to 1%, functional development of the graft was highly probable (p less than 0.001). Diuresis above 400 ml/h had an adverse (p less than 0.01) effect on the early functional development of the graft.

1. Benzodiazepines and strong analgesics raise considerably the ventricular fibrillation threshold and thus electrically stabilize the heart in the early stage of myocardial ischaemia. 2. Benzodiazepines markedly potentiate the electrostabilizing effect of the beta-blocker metipranolol. 3. Trimecaine per se does not electrically stabilize the heart in the first hour of ischaemia. When combined with a benzodiazepine, trimecaine stabilizes the heart also in this early stage of myocardial ischaemia. 4. Infusion of a benzodiazepine (midazolam) combined with fractionated administration of a potent analgesic (fentanyl) does not produce pronounced changes in the haemodynamics and ventilation of healthy subjects. 5. Benzodiazepines and strong analgesics exert a favourable effect on the neurovegetative stress response in the early stage of acute myocardial ischaemia. They can be therefore recommended as a component in the treatment of patients with acute myocardial infarction.

The paper list the results of a comparative study on the clinical and haemodynamic effects of 2 medicaments, registered in the Czechoslovak Socialist Republic, i. e. dobutamine hydrochloride, Dobutrex the Federal Republic of Germany) and Dobuject (Loiras, Finland). The medicaments were applied to high-risk patients (NYHA III-IV) after open heart surgery with the low cardiac output syndrome. Dobutrex was applied in 14 patients and Dobuject in 16 patients. Both preparations improved the cardiac output shown in an increased cardiac index and left ventricular stroke work index and the pressure decrease in pulmonary capillaries measured with a wedged-in catheter. Both these preparations (Dobutrex, Dobuject) appear to have comparable parameters as regards favourable positive inotropic effects.