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Biomedical subjects

J Nauta

Publications and source records attributed to J Nauta.

At least 73 records · Page 4Linked to original sources
PubMed1987

[Renal tubular function in preterm neonates].

Renal tubular function and functional changes in the preterm neonate are discussed. The proximal tubule has a limited capacity in preserving sodium, leading to a daily sodium need from 3 to 5 mEq/kg/day. The reabsorption of glucose, phosphate and amino acids is also low compared to older children but increases quickly for glucose and phosphate. At the level of the distal tubule, a temporary insensibility for aldosterone leads to a lowered sodium-potassium exchange. A limitation in acid excretion is present. Concentration capacity is restricted with a maximal urine osmolality of 360 mosm/liter. Despite this immature tubular function a glomerulotubular balance exists even in the preterm neonate. The kidneys are thus capable to preserve their homeostatic function.

Acid-Base Equilibrium↗
PubMed1984

Cell survival in canine aortic heart valves stored in nutrient medium.

For transplantation of viable aortic valves a period of preservation will generally be needed. To maintain cell viability during this preservation period valves can be stored in nutrient medium after sterilisation in an antibiotic solution. To obtain quantitative data about the survival of aortic valve fibroblasts after preservation, we determined the number of viable fibroblasts in canine aortic valves after several weeks of preservation. The results shows that after storage of 1 week in nutrient medium cell survival is about 80%, after 2 weeks cell survival has declined substantially, while after 3 weeks survival is already unacceptably low. Storage for periods over 4 weeks results in almost completely non-viable aortic valves. These results show that only valves preserved for 1 to 2 weeks in nutrient medium can be considered as viable aortic valves.

Animals↗
PubMed1984

Ventricular free wall rupture: sudden, subacute, slow, sealed and stabilized varieties.

Six cases of acute myocardial infarction with blood in the pericardial sac are described. In one case rapid death followed myocardial rupture leaving no time for the possibility of intervention. Of two other cases acute symptoms developing after myocardial rupture, one was operated on promptly and the other, whose condition improved on pericardiocentesis, after a delay of a few hours. Both are now long term survivors A fourth patient probably had two episodes of rupture which apparently sealed off. He underwent cardiac catheterization, but no epicardial leak was found. Subsequently at operation a sealed myocardial rupture was detected and sutured over. The fifth patient suffered a silent myocardial rupture. A false aneurysm was diagnosed four months later and he withstood successful surgery. In the sixth patient, the course was similar to that of case 1, namely rapid death with a clinical picture suggestive of tamponade. Postmortem examination showed a covert rupture with some evidence of attempts to plug the opening. The purpose of this report is to emphasize the varying course which myocardial rupture can take.

Acute Disease↗
PubMed1984

Enhanced fibrinolytic activity during cardiopulmonary bypass in open-heart surgery in man is caused by extrinsic (tissue-type) plasminogen activator.

The nature of the enhanced blood fibrinolytic activity which is known to occur during cardiopulmonary bypass is not understood. We show here that the cause is an increase in extrinsic (tissue-type) plasminogen activator. In six patients, the nature of the enhanced blood fibrinolytic activity that evolved during cardiopulmonary bypass was characterized by differential inhibition using the fibrin plate method and was shown to be C1-inactivator-resistant (extrinsic-activator activity). The C1-inactivator-resistant-activator activity was completely quenched by an antibody against extrinsic (tissue-type) plasminogen activator but not by antiurokinase, proving that the activity was due to the presence of extrinsic (tissue-type) plasminogen activator. The concentration of extrinsic (tissue-type) plasminogen activator increased during cardiopulmonary bypass and disappeared rapidly thereafter. Fibrinogen, plasminogen and alpha 2-antiplasmin were not consumed during cardiopulmonary bypass, while no increase or occasionally a moderate one in fibrinogen degradation products occurred. This is in accord with the property of extrinsic (tissue-type) plasminogen activator which activates plasminogen predominantly at sites where fibrin is present and not in the free circulation.

Cardiopulmonary Bypass↗
PubMed1983

Anaesthetic induction with alfentanil: comparison with thiopental, midazolam, and etomidate.

The speed, side effects and cardiovascular changes associated with anaesthetic induction and endotracheal intubation following alfentanil (20 micrograms/kg/min, IV), thiopental (84 micrograms/kg/min, IV), etomidate (5 micrograms/kg/min, IV) and midazolam (20 micrograms/kg/min, IV) prior to halothane-nitrous oxide general anaesthesia were evaluated and compared in 80 patients undergoing elective general surgical operations. Anaesthetic induction was fastest with etomidate and thiopental (approximately one minute) and slowest with midazolam (about two minutes). Systolic arterial blood pressure (SBP) was decreased at the moment of unconsciousness with thiopental but unchanged with the other compounds. Heart rate (HR) was increased at unconsciousness with midazolam and thiopental but unchanged with etomidate and alfentanil. After intubation HR was increased in all groups except those induced with alfentanil. Arrhythmias were infrequent (5 per cent or less in all groups). Rigidity during induction only occurred with alfentanil (55 per cent) and pain on injection only with etomidate (35 per cent) and alfentanil (5 per cent). Postoperative vomiting was infrequent in all groups (15 per cent) except etomidate (55 per cent). No patient remembered any aspect of laryngoscopy or the operation and all rapidly regained consciousness at the end of operation. The results of this study demonstrate that with the exception of rigidity (which is easily overcome with succinylcholine) and a slightly slower onset of action, alfentanil compares favourably as an induction agent with thiopental and is better than midazolam and etomidate. Alfentanil is superior to all three other induction agents with respect to cardiovascular stability during induction and intubation.

Adjuvants, Anesthesia↗
PubMed1983

Echocardiography in chronic aortic insufficiency. Is valve replacement too late when left ventricular end-systolic dimension reaches 55 mm?

To determine whether a ventricular (LV) end-systolic dimension (ESD) greater than or equal to 55 mm and LV left fractional shortening less than 25% are risk factors for aortic valve replacement (AVR) in patients with aortic insufficiency, we analyzed the clinical course and M-mode echocardiograms in 47 consecutive patients who underwent AVR for isolated symptomatic AI. Group 1 patients (n = 27) had a preoperative ESD less than 55 mm (mean 44 mm, range 30-52 mm) and group 2 patients (n = 20) had a preoperative ESD greater than or equal to 55 mm (mean 62 mm, range 55-85 mm). One patient in group 1 and 10 patients in group 2 had left ventricular fractional shortening less than 25%. There were no perioperative or postoperative deaths during an average follow-up of 41 months (range 6-76 months). Five patients had perioperative myocardial infarctions (MIs), three in group 1 and two in group 2. Since myocardial protection with cold potassium cardioplegia was instituted, no patient has suffered a perioperative MI. The average preoperative New York Heart Association functional classification was 2.3 (group 1) and 2.6 (group 2). Postoperatively, it was 1.2 in group 1 and 1.1 in group 2. Thirty-three patients (20 in group 1 and 13 in group 2) had echocardiograms at least 1 year after AVR. Of these, LV-end diastolic dimension decreased fro 67 +/- 6 to 53 +/- 6 mm (mean +/- SD) in group 1 (p less than 0.001) and from 79 +/- 3 to 55 +/- 6 mm in group 2 (p less than 0.001). The LVESD also decreased, but this is difficult to interpret because of frequent postoperative abnormal interventricular septal motion. The LV cross-sectional area, an index of LV mass, decreased in group 1 from 25 +/- 5 to 20 +/- 5 cm2 (p lss than 0.001) and in group 2 from 32 +/- 9 to 20 +/- 5 cm2 (p less than 0.001). Postoperative end-diastolic dimension and cross-sectional area were not significantly different between the two groups. We concluded that in aortic insufficiency, a preoperative ESD greater than or equal to 55 mm does not preclude successful AVR, as judged by long-term survival, symptomatic relief, and normalization of LV dimensions assessed by echocardiography.

Adult↗
PubMed1981

Effects of the gelatin plasma substitutes Haemaccel, Plasmagel and Plasmion (Geloplasma) on collagen-, ADP- and adrenaline-induced aggregation of human platelets in vitro.

The effect of some gelatin plasma substitutes (Haemaccel, plasmagel and Plasmion (Geloplasma), which are widely used in Europe) on collagen-, ADP- and adrenaline-induced platelet aggregation in human PRP in vitro was studied under controlled conditions (pH, electrolyte composition). Haemaccel inhibited these aggregations, both in citrated as well as in heparinised PRP, whereas they were enhanced by both Plasmagel and Plasmion as compared to the appropriate control. Increasing teh concentration of the inducer overcame the inhibition by Haemaccel. Haemaccel inhibited, while Plasmion enhanced 14C-serotonin release induced by collagen, ADP or adrenaline. Also in the presence of indomethacin (90 muM) Haemaccel inhibited aggregation induced by high concentrations of collagen and the primary aggregation induced by ADP and adrenaline, while Plasmion enhanced these aggregations induced by ADP and adrenaline, while Plasmion enhanced these aggregations. The inhibition by Haemaccel was not caused by binding of Ca2+ to haemaccel.

Adenosine Diphosphate↗
PubMed1979

Fibroblast function and the maintenance of the aortic-valve matrix.

The long-term behaviour of the aortic-valve allograft seems to be dependent on the maintenance of its matrix. Protein and collagen synthesis was studied in rat aortic-valves. Quantitative and qualitative methods proved the production of at least two protein pools. One protein pool is localised intracellularily with a 'turn-over' time of about 2 weeks, and a second pool is localised extracellularly with a 'turn-over' time of at least 8 weeks. The latter protein pool mainly consists of collagen.

Animals↗
PubMed1979

Regional myocardial shortening in relation to graft-reactive hyperemia and flow after coronary bypass surgery.

Extent of regional shortening of myocardium in areas newly perfused by bypass grafting was determined in 56 patients by a new technique employing four to six radiopaque markers sutured in pairs to the epicardium near the coronary anastomosis. Paradoxical systolic expansion (PSE) was manifest in 16 regions (a 12% incidence) during the follow-up period, and six of these showed spontaneous remission. All cases of PSE were in the region of the left anterior descending artery. Correlation between graft flow measured during operation and regional shortening during the postoperative period revealed that the development of PSE could not be predicted from the hemodynamic measurements. In the majority of cases postoperative myocardial infarction could also be excluded as an explanation. At 1 year after operation most grafts were patent in PSE regions but collaterals, apparent preoperatively, could not be visualized. Excluding PSE, shortening fraction (ratio of shortening to maximum marker separation) for all graft regions at 1 week was 9.8%; 1 month, 12.8%; 3 months, 13.3%; and six months, 13.9%. Average graft flow was 56 ml. per minute and average reactive hyperemia was 25% with 37% of grafts showing no response. For those regions that did not develop PSE there was a positive correlation between shortening fraction and flow that became significant (null hypothesis: r = 0) when reactive hyperemia exceeded 20%. Correlation was greatest at 1 week and 1 month, but became nonsignificant at 6 months. These results are consistent with a simple interpretation of reactive hyperemia: Graft-reactive hyperemia is related to the dependence of viable tissue on the functioning of the graft.

Adult↗
PubMed1977

Ultrasonic demonstration of right ventricular myxoma.

A case of right ventricular myxoma masquerading as infundibular pulmonic stenosis with right-sided heart failure is presented. The unsuspected tumor was diagnosed with two-dimensional multicrystal real time scanning and single element echocardiography. Direct visualization of the tumor anatomy and its spatial relationships on cross-sectional images facilitates the diagnosis. On the other hand, the more accurate motion analysis form the time-motion display of the echo data yields additional functional information. Thus the two techniques are complementary to establish a diagnosis in those disorders where anatomy and function overlap. Ultrasonic examination yields a practical solution to the problem of screening patients to detect intracardiac tumors. This painless, noninvasive examination should be included in the analysis of every patient with cardiac symptoms.

Angiography↗
PubMed1975

On-line monitoring of mixed venous oxygen saturation after cardiothoracic surgery.

On-line monitoring of MVo2 sat. in vivo by means of fibreoptic reflectometry was studied in 19 patients as to its predictive value during the postoperative course after thoracotomy for periods up to 60 hours. In all but one of the 10 patients with MVo2 sat. less than 65% for at least one hour complications occurred. A fall of MVo2 sat. of more than 5% or a value below 60% predicted a period of hypotension in six patients. In two of them this coincided with a period of ventricular arrhythmias. In those with MVo2 sat. greater than 65% no postoperative complications such as arrhythmias, shock, respiratory dysfunction or oliguria took place.

Acid-Base Equilibrium↗
PubMed1975

Echocardiographic diagnosis of pseudoaneurysm of the left ventricle.

The echocardiographic features of postinfarction pseudoaneurysm of the left ventricle are described for the first time. Because ultrasound allows the detection of soft-tissue structures in a manner not possible with other diagnostic techniques, the left ventricular wall can be visualized separating the left ventricular cavity from the saccular aneurysm which is delineated by pericardium and/or extracardiac tissue. In addition to these anatomic findings, relevant qualitative hemodynamic data can also be obtained. Echocardiography seems to be a safe and specific method for the diagnosis of left ventricular pseudoaneurysm. It is suggested that echocardiography should be used in the incipeint phase of pseudoaneurysm formation to detect subacute cardiac rupture.

Acute Disease↗
PubMed1975

Detection of water-to-blood leakages in heat exchangers for cardiopulmonary bypass.

In the construction of heat exchangers, it is of great importance that when they are in use it shall be impossible for water to leak into the blood, as this might lead to hemolysis, intoxications, air emboli, or infection by microorganisms. In an investigation the aim of which was to discover water-to-blood leakages in the heat exchangers that are generally used during cardiopulmonary bypass, tests were carried out on 17 heat exchangers that are used all over the world and are supplied by five different makers. They included both disposable and nondisposable models. In six stainless steel heat exchangers, water leakages to the blood compartment were detected with the aid of helium. Some of these heat exchangers were brand new and had never been used. The size of the leakages was found to be sufficient to enable them to act as channels for the passage of foreign microorganisms.

Blood↗