Biomedical subjects
Publications and source records attributed to P Beer.
In a 27-year-old woman a spontaneous perforation of the bowel developed after cesarean section. The clinical picture, pathophysiological aspects and prophylactic treatment of Ogilvie's syndrome are discussed. This rare but serious complication could have been avoided if the clinical picture and its simple conservative treatment had been known.
In relation to the Swiss average our hospital has had a constant high rate of spontaneous deliveries and a low rate of cesarean sections. On the other hand the rate of obstetrical peridural anesthesia has been increasing significantly since 1986. This is above all related to its more frequent usage in cases of cervical dystocia and intolerable birth pain. Exactly in these indications peridural anesthesia has been very successful. In almost three quarters of the above-mentioned cases a cesarean section can be avoided due to peridural anesthesia.
A case of a 67-year old woman with adenosarcoma of the uterus is reported. Adenosarcoma is a mixed mesodermal tumour with a low malignant potential. It is characterised by a benign glandular and a malignant stromal component. Adenosarcomas are usually treated by hysterectomy with bilateral salpingo-oophorectomy. Patients with myometrial invasion have an increased risk of recurrence. It may be appropriate, to consider adjuvant chemotherapy or radiation treatment for these patients.
Maternal lung edema due to the use of beta-mimetic tocolytic agents is a well-documented complication. The risk increases if several other factors are present: infectious diseases, the use of inhaled anesthetics, EPH gestosis, hydramnios, twin gestation and preexisting cardiovascular disease. The complications induced by beta-mimetic tocolytic agents can be reduced by remembering their side effects and contraindications and restricting fluid intake. During obstetric general anesthesia in patients undergoing tocolysis, the infusion of large amounts of saline, as is widely practised today, is strictly contraindicated.
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Within the first 14 days after implantation, thresholds were measured at three transvenous pacemaker electrodes with different surface areas. It should be verified, 1. to what extent a correlation existed between maximal threshold increase and electrode surface, 2. how electrode impedance and 3. how the amplitudes of the R-wave voltages developed. The results were: At initial implantation, thresholds were all the lower the smaller the electrode-surface area was. On overage, 9-10 days after implantation the highest thresholds were reached. Thereby, in small surface area electrodes the threshold-increase factor was greater than in larger ones. In all cases the current threshold increase exceeded that one for voltage thresholds. 14 days later, thresholds had dropped again compared to the maximum. And this decrease was depending on the electrode-surface area also. The electrode impedance decreased after implantation to rise later on once more to 80-88% of the original value. The magnitude of the detected R-wave was independent on electrode-surface area. Indeed, using small surface electrodes, signal reductions up to 50% could be found. But 14 days later they reached again 80-95% of the initial amplitude. The key finding there is that when applying small surface-area electrodes and presuming suitable initial thresholds it seems to be possible to connect low-output pacemakers (output 5,4 V and impluse duration 0.25 ms or 4 V at 0.5 ms) to those electrodes. By this reduction of the safety margin, a considerable increase in pacemaker lifetime could be achieved.
Based upon experiences with 14 patients the clinical feasibility of transmediastinal retrocardial stimulation of the heart, of the left atrium as well as in one case of the left ventricle, is reported. Principally both can be stimulated by thus introduced pacemaker electodes. Thus on the one hand thresholds and consequently pulse effectivity appear to be a function of the electrode distance from the myocardium, whilst on the other hand the transmediastinal retrocardial thresholds are initially rather high in analogy to the majority taken from the atrial endocardial surface. Nevertheless, the transmediastinal retrocardial technique is possibly applicable for permanent cardiac pacing. However, additional tests about this are still necessary.
The clinical utilization of atrial programmed pacemakers is limited by the lead systems available for sensing of atrial activity. The endocardial method of lead placement is burdened by a dislodgement rate of up to 30 per cent. Alternatively, the patient must submit to the risks of a thoracotomy. Thirty-one patients have been treated with a transmediastinally, retrocardially positioned atrial detector electrode. In 20 patients (65 per cent) the detector performed as desired with no postimplant revision. In 11 patients (35 per cent) corrective measures were required primarily to correct lead placement; seven of these were corrected under local anesthesia merely by pulling the catheter. Spontaneous lead dislocation occurred in four patients. Four patients (13 per cent) underwent remediastinoscopy due to cranial displacement of the detector electrode with a resulting decrease in atrial potential to less than 0.5 mV. For technical reasons, the lead placements were performed without the benefit of x-ray illumination, with only an ECG check of the posterior atrial wall, and this may account for the relatively high incidence of revision. Transmediastinal placement of sensing electrodes presents a practicable alternative to methods presently used.
Between March 1972 and December 1975 87 atrial leads were implanted into 85 patients. In 37 cases the transmediastinal retrocardial approach was preferred. In all the other cases the electrodes were introduced transvenous endocardially. The results showed: 1. There exist techniques of atrial lead emplacement which, when applying suitable lead designs, guarantee an anatomic stable positioning either on the left or in the right atrium. Especially the new transvenous J-shaped electrodes of type Medtronic TJL can be positioned easily. The dislodgement ratio of these leads amounts of only 6%. 2. Retro- as well as intracardially very high action voltages were found. The ones sensed by the J-tip-electrodes from the endocardial surface of the right appendage even run up to 5,4 mV. 3. In spite of relatively high initial thresholds, no exit block was seen in any of the 34 cases, in whom atrial leads were inserted transvenous endocardially for permanent atrial pacing.