Biomedical subjects
Publications and source records attributed to F Bonnet.
The primary structure of a human platelet proteoglycan (P.PG) core was established by a combination of amino acid sequence analysis and cDNA cloning. The deduced 131 amino acid long protein contains eight Ser-Gly repeats. The significance of homologies observed between P.PG and promyelocytic leukemia cell line proteoglycans is discussed.
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Carotid endarterectomy can be complicated by neurological events due to different mechanisms. Monitoring cerebral function is difficult under general anaesthesia. By contrast, the monitoring of awareness and neurological deficit is very easy under regional anaesthesia. The aim of this study was to assess the requirement for arterial shunting during endarterectomy performed under cervical epidural anaesthesia, to analyse the neurological events and to compare the value of clinical and electroencephalographic monitoring. Sixty-four patients were included in this study. Cervical epidural anesthesia was performed with 0.375% bupivacaine and 100-150 micrograms fentanyl. In 19 high risk patients, a one-channel electroencephalographic filter processor (Cerebral function monitor, Critikon) was placed over the affected hemisphere. Before surgery, it was estimated, on angiographic and Doppler data, that 18 patients needed an arterial shunt for carotid clamping. An arterial shunt was in fact inserted during surgery in only four patients, because of cerebral ischaemia after carotid clamping. Transient obnubilation was observed during carotid clamping in three other patients; it disappeared on unclamping in two, and on increasing blood pressure in the third. An additional patient suffered from a very short loss of awareness after declamping, due to cerebral embolism. The cerebral function monitor never documented false positive results, but failed to detect one out of every five neurological events. Controlateral carotid occlusion and preoperative stroke were documented to correlate with peroperative neurological events. Cervical epidural anaesthesia, which maintains consciousness during surgery, reduced in high-risk patients the need for arterial shunting as well as that for the analysis of neurological events.
There is little data concerning failures in spinal anaesthesia. A retrospective analysis of 337 spinal anaesthesias performed in a teaching hospital gave a 9.8% failure rate. A failure was defined as the need to carry out part or all of a surgical act under general anaesthesia when spinal anaesthesia had been carried out. The main causes of failure were insufficiently or excessively extended neural blockade, insufficient duration or a poor quality sensory blockade with the patient feeling surgical or tourniquet pain. The local anaesthetics used were hyperbaric 0.5% tetracaine with and without 0.1 mg metaraminol, hyperbaric 0.5% prilocaine and isobaric 0.5% bupivacaine. The failure rate was 19.4% with plain hyperbaric tetracaine, 7.6% with tetracaine with metaraminol, 5% with prilocaine and 2.9% with isobaric bupivacaine. This rate was related neither to the experience of the anaesthetist, nor to the clinical features of the patients, nor to the position nor to the needle size. Although there were more failures during orthopaedic procedures, probably because of tourniquet pain, this was not significant. These results confirmed that spinal anaesthesia was a reliable technique. Hyperbaric plain tetracaine did not always guarantee a successful anaesthesia and isobaric bupivacaine should be more commonly used.
The constant monitoring of respiratory elastance and resistance can be of interest in patients who present a high risk of peroperative bronchospasm. The constant inspiratory flow method, proposed by Bates et al. (J Appl Physiol, 58: 1840, 1985) was chosen and automated. The inspiratory flow rate and pressure were measured respectively by a pneumotachograph linked to a differential pressure, and by a differential pressure transducer, both placed at the outlet of the inspiratory circuit. The pressure and flow signals were low-pass filtered, sampled, and then processed by an Apple II microcomputer, in order to obtain respiratory elastance and resistance. New results were displayed on the screen about every minute. The automated method was first tested in a series of 18 guinea-pigs; the respiratory parameters were compared with those obtained by the occlusion method proposed by Rossi et al. (J Appl Physiol, 58: 1849, 1985). They were found not significantly different and very strongly correlated (p less than 0.001). The ability of the constant flow method to detect changes in respiratory mechanics was then tested in a series of nine patients, after anaesthetic induction. The results obtained were in accordance with those previously published: a rise in both respiratory elastance and resistance. After giving 1 mg atropine intravenously, the respiratory resistance fell rapidly over a 5 min period, and then reached a plateau. The constant flow method, which avoids interruption in the mechanical ventilation and is sensitive to small changes in respiratory parameters, appears particularly convenient for the peroperative monitoring of patients.
The effects of a change in position on gas exchange and ventilation perfusion (VA/Q) distribution were studied in 12 patients, after abdominal surgery. VA/Q distribution was determined from retention and excretion curves of six inert gases of different solubilities, in supine and sitting patients, during spontaneous breathing. Changing position from supine to sitting resulted in an increase in minute ventilation and a decrease in PaCO2 without any change in PaO2. With regard to VA/Q distribution, an estimated shunt of 5.2% +/- 3.4 was documented in all the patients in the supine position, and was associated with a large percentage of low VA/Q regions (20.0% +/- 13.0) in six of them. Patients with associated estimated shunt and low VA/Q regions were those with the greatest amount of venous admixture (respectively: 27.3% +/- 7.2, and 14.9% +/- 3.0, for patients without low VA/Q regions, P less than 0.01). When patients were placed in the sitting position, the estimated shunt was not reduced, but the percentage of low VA/Q regions decreased when it was documented. Despite the improvement of VA/Q distribution in the sitting position, the lack of significant change in PaO2 may be explained by the simultaneous decrease in PVO2 caused by a decrease in cardiac output.
Goiter with major respiratory compromise is uncommon but troublesome. Evaluation and treatment of this condition are controversial. Of a total of 2,908 goiters operated on over a 17-year period, 58 cases with this particular complication were studied retrospectively to define optimal management. Twenty-two patients had severe or acute dyspnea, and four of them required immediate tracheal intubation. Thirty-six patients had chronic dyspnea without cyanosis. Carcinoma was present in these two groups in 50% and 11% of patients, respectively. Results of our retrospective study are as follows: long-standing tolerance of goiter did not preclude the possibility of compressive respiratory distress or carcinoma. Optimal management of goiter with respiratory compression was obtained when surgery was delayed until satisfactory operating room conditions and adequate possibilities of interpretation of pathologic conditions were united. In case of respiratory distress, tracheal intubation allowed to abide without risks. In other patients preoperative investigations were kept to a minimum. Technical artifices facilitated the extraction of the goiter via cervicotomy without sternotomy in 92% of patients with minimal morbidity. Whenever necessary, endotracheal intubation obviated the need for tracheostomy. These data suggest preventive removal of all large or substernal goiters.
Hyaluronic acid-binding region and trypsin-link protein were prepared from bovine nasal cartilage proteoglycan complex after trypsin digestion. Binary complexes were reformed between trypsin-link protein and hyaluronic acid-binding region or hyaluronate. Upon trypsin treatment of these complexes, two fragments deriving from trypsin-link protein were characterized. One of them, of 20 kDa, corresponds in fact to a 140-amino acid long fragment and bears the glycosylated site of trypsin-link protein; it appears to be involved in proteoglycan/link protein interaction. The other, of 22 kDa, corresponds to the 200 C-terminal amino acids of trypsin-link protein; it appears to be involved in the binding of link protein with hyaluronic acid. A structural model of bovine trypsin-like protein depicting two distinct domains involved in hyaluronate and proteoglycan subunit interactions is proposed.
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Eight patients with a delayed-onset heparin-induced thrombocytopenia, with thrombotic complications requiring immediate anticoagulation in 7 of them, were given low molecular weight heparin (LMWH) fractions as alternative therapy. This treatment led to normalization of platelet count within 3-5 days in 6 patients with clinical recovery in 5. In 2 patients, thrombocytopenia persisted despite LMWH therapy. In vitro platelet aggregation tests performed in all patients gave evidence of a relationship between the presence (or absence) of a LMWH-dependent platelet-aggregating factor in the patients' plasma and the persistence (or correction) of the thrombocytopenia with LMWH therapy. Although positive in vitro tests may not necessarily be associated with thrombocytopenia, in vitro testing may prove to be a useful guide before giving LMWH fractions as an alternative therapy in patients with heparin-induced thrombocytopenia requiring immediate anticoagulation.
To assess the hormonal response to captopril pre-treatment during sodium nitroprusside (SNP) -induced hypotension, 12 patients were studied during a spinal surgical procedure. Haemodynamic data, plasma-renin activity, aldosterone, adrenaline and noradrenaline levels were measured. Patients were randomly allocated to two groups: Group I, control patients; Group II, 3 mg kg-1 captopril pre-treated patients. SNP requirement for the same level (mean arterial pressure (MAP) = 55 mmHg) and duration of hypotension (88.5 +/- 28.7 vs. 95.2 +/- 22.5 min) was significantly lower in Group II than in Group I (16.5 +/- 14.2 mg vs. 39.3 +/- 16.7 mg; P less than 0.05) and a lower SNP infusion rate was required to induce and to maintain hypotension. In Group II patients, MAP remained significantly lower than the control and Group I values for 30 min after SNP withdrawal. Cardiac index (CI) remained stable in both groups. Heart rate was not modified in Group II during hypotension. Plasma-renin activity rose more dramatically in Group II patients than in Group I both during hypotension (13.9 +/- 7.5 vs. 2.8 +/- 0.9 ng ml-1 h-1; P less than 0.05) and after hypotension (23.4 +/- 15.4 vs. 2.2 +/- 0.8 ng ml-1 h-1; P less than 0.05). Plasma catecholamine levels increased in both groups during hypotension and remained raised in captopril patients after SNP withdrawal. It can be concluded that recovery from hypotension may be delayed when using captopril and that sympathoadrenal activity induced by hypotension is not substantially altered by captopril pre-treatment, suggesting that sympathetic blockade might not be the mechanism by which captopril reduces SNP requirement during controlled hypotension for surgical procedure in man.
PPAV is a type of Mollicutes that was isolated in SP4 medium from seeds of apples affected by proliferation, a disease in which mycoplasma-like organisms (MLOs) are involved. However, PPAV is probably not the etiological MLO agent for at least two reasons: 1) optimal temperature growth is 43 C, and 2) in spite of numerous isolation attempts over several years, no second PPAV culture could be obtained. PPAV is surrounded by a single cytoplasmic membrane and forms typical fried egg-shaped colonies on solid medium. The organism grows in simplified mycoplasma media, such as BSR. In growth inhibition, it shows no serological relationships with any other mycoplasmas or acholeplasmas, including those cultured from the surfaces of plants. The absence of relatedness of PPAV to other Mollicutes was confirmed by DNA hybridization studies. The genome of PPAV is close to 10(9) daltons and contains 25.2 mol % G + C. Its genome size is similar to that of Acholeplasma spp. and Spiroplasma spp. It has, however, a clearcut sterol requirement and therefore cannot be an acholeplasma. Neither is it a spiroplasma since, though filamentous in BSR medium, it has never shown signs of helicity. Hence, PPAV is a taxonomical paradox.
Structural homologies between link proteins and proteoglycan monomers are demonstrated. A possible redundancy in the proteoglycan monomers structure is discussed and the link proteins domains homologous to other proteins are specified.
The N-terminal sequence (residues 1-101) of trypsin-link protein from cartilage proteoglycan complex is reported: it presents structural homologies with the poly-Ig receptor and immunoglobulin domains.
The role of computerized tomography in the diagnosis and treatment of late complications of acute pancreatitis was evaluated in 25 patients with acute pancreatitis. The clinical severity of the pancreatitis was assessed by Ranson's criteria. In each patient. the scan showed abnormalities of the pancreatic and at least one intraabdominal extrapancreatic extension of the disease. The scan precisely locates the intraabdominal extensions secondary to acute pancreatitis, and thus can guide surgical drainage, but it is less accurate in differentiating solid infiltration of fat planes from necrotic collections. However, in most of our patients, the association of general signs of sepsis with a collection shown on computerized tomographic scan indicated necrosis requiring surgical drainage.
The consequences of controlled ventilation with positive end-expiratory pressure (PEEP) were studied, after cardiac surgical procedures, in two groups of patients supposed to have different lung and chest wall mechanical properties. The first group included 6 patients who had undergone coronary artery graft surgical procedures (CGS). The second group included 5 patients who had undergone a mitral valve replacement (MVR). Postoperatively, static lung and chest wall compliance was measured by stepwise inflation and deflation of the thorax. Esophageal, pericardial, and pleural pressures were then measured, and cardiac output was determined while PEEP was increased from 0 to 20 cm H2O. Lung and chest wall compliance values sharply decreased in MVR patients. This accounts for the lower values for pleural and pericardial pressures in this group than in the CGS patient group, but the transmission of airway pressure was identical in the two groups when PEEP was increased. The decrease in cardiac output induced by PEEP was similar in the two groups. The results suggest that the opposing influences of lung and chest wall compliance on airway pressure transmission could at least partly explain the hemodynamic effects of PEEP in patients in whom the mechanical properties of the lung and thorax are impaired. PEEP ventilation should be used cautiously in patients suspected of having thoracic rigidity.