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Biomedical subjects

G J Scheffer

Publications and source records attributed to G J Scheffer.

At least 37 records · Page 2Linked to original sources
PubMed2001

The differential effect of propofol on contractility of isolated myocardial trabeculae of rat and guinea-pig.

1. The effects of propofol on myocardial contractility were studied in rat, in which the contractile activation mainly depends on calcium derived from the sarcoplasmic reticulum (SR), and guinea-pig, in which transsarcolemmal influx of calcium plays a major role. 2. Intact and chemically skinned trabeculae from the right ventricle were studied. Intact trabeculae were electrically stimulated and force development during steady state and post rest contractions was measured. In saponin skinned trabeculae Ca(2+) uptake and release by the SR was studied. In Triton skinned trabeculae the influence of propofol on calcium sensitivity of the myofilaments was studied. 3. In intact rat trabeculae propofol in concentrations of 28, 112 and 280 microM did not change peak force development nor the pattern of post rest contraction. In guinea-pig trabeculae propofol significantly reduced peak force to respectively 64, 40 and 23% of control values and the post rest contractions were potentiated. In skinned trabeculae propofol did not affect Ca(2+) handling by the SR, nor did it change force production and Ca(2+) sensitivity of the myofilaments. 4. This study shows that, in contrast to rat, in guinea-pig propofol directly depresses myocardial contractility, probably by decreasing transsarcolemmal Ca(2+) influx. There is no significant influence of propofol on Ca(2+) handling by the SR, nor on the contractile proteins.

Anesthetics, Intravenous↗
PubMed2001

Liver and renal function after volatile induction and maintenance of anesthesia (VIMA) with sevoflurane versus TIVA with sufentanil-midazolam for CABG surgery.

We compared liver and renal function after volatile induction and maintenance of anesthesia (VIMA) with sevoflurane and minimal dose sufentanil versus total intravenous anesthesia (TIVA) with moderate dose of midazolam and sufentanil in patients undergoing CABG surgery. Eighty nine patients were studied retrospectively after VIMA (44 patients) or after TIVA (45 patients). Liver and renal function were measured before (T0), then 1 (T1), 2 (T2), 5 (T3) days and 6 weeks (T4) after the operation. Serum levels of aspartate aminotransferase (ASAT) and lactate dehydrogenase (LDH) increased in both groups at T1, T2 and T3 and the highest levels were at T1. Levels of total bilirubin (TBil) increased at T1 only in the TIVA group. Levels of g-glutamyl transpeptidase (GGT) and alanine aminotransferase (ALAT), increased in both groups at T3. Serum levels of creatinine (Cr) were high in both groups on T1 and T2. Blood urea nitrogen (BUN) was high in both group at T2, and T3 with the peak levels in T2. Six weeks after the operation all liver and renal functions were normal in both groups. We concluded that VIMA with sevoflurane during cardiac surgery has no untoward effects on liver or renal functions. The transient reversible elevation was comparable in the VIMA and TIVA groups which was most probably due to the effect of the operation itself.

Aged↗
PubMed1999

Antral follicle counts by transvaginal ultrasonography are related to age in women with proven natural fertility.

OBJECTIVE: To investigate the relation between reproductive age and ultrasound (US)-based follicle counts and the reproducibility of follicle counts in regularly cycling women with proven fertility. DESIGN: Prospective observational study. SETTING: Tertiary fertility center. PATIENT(S): Healthy female volunteers with proven fertility, recruited by advertisement in local newspapers. INTERVENTION(S): The number of antral follicles sized 2-10 mm and ovarian volume were estimated by transvaginal US in the early follicular phase of the menstrual cycle in 162 women. A subgroup of 81 women underwent transvaginal US at several times in three subsequent cycles. MAIN OUTCOME MEASURE(S): Antral follicle count and total ovarian volume. RESULT(S): Women aged 25-46 years (n = 162) were studied. The relation of age with the US indices was computed after natural log transformation. Antral follicle count showed the clearest correlation with age (R = -0.67). A biphasic linear model gave the best fit to the data. Before the age of 37 years, the antral follicle count showed a mean yearly decline of 4.8%, compared with 11.7% thereafter. The reproducibility of the antral follicle count in two subsequent cycles was moderate. CONCLUSION(S): The number of small antral follicles in both ovaries as measured by US is clearly related to reproductive age and could well reflect the size of the remaining primordial follicle pool.

Adult↗
PubMed1998

Developmental and endocrine aspects of normal ovarian aging.

Supplies of follicles are established during early fetal life and decrease exponentially thereafter by a process called atresia. Subfertility only starts at a mean age of about 30-31 years, when the remaining follicle reserve has become a fraction of its original number. Thereafter, a further decrease in both oocyte quantity and quality dictates the subsequent reproductive events including decrease of fertility, increased abortion rate, the end of fertility, the beginning of cycle irregularity and, when almost no follicles are left, the occurrence of menopause. The same remarkable variation of age at menopause almost certainly is also present for the preceding reproductive events. When quantity and quality of antral follicles drop below a critical threshold, there is a subsequent drop in inhibine B resulting in the selective FSH rise at a mean age of 37-38 years. This FSH rise explains the accelerated follicle depletion, the increased proportion of growing follicles reaching the selectable stage, the shortening of the follicular phase and the increased incidence of dizygotic twinning. The concurring decrease of oocyte quality is in line with the increased incidence of abortions and chromosomal aberrations after age 35.

Aging↗
PubMed1998

Ovarian reserve tests in infertility practice and normal fertile women.

The decline in fecundity with the age of the woman is mainly attributed to the loss of follicles from the ovary and a decrease in oocyte quality. Evaluation of the aging status of the ovary in an individual woman has been hampered by a lack of knowledge with regard to the relative contribution of these two factors. Most if not all so called ovarian reserve tests (ORT) reflect indirectly the remaining follicle pool in the ovary. Direct a priori assessment of oocyte quality is not possible to date. In this section the predictive value of several ovarian reserve tests for the outcome of fertility treatment is listed and commented. In addition, the study of several of the ORTs in normal, fertile women is described. From the data presented dynamic testing of the ovarian function by the clomiphene citrate and GnRH agonist stimulation test, as well as static testing by the use of ultrasound based antral follicle counts seem to offer the highest clinical value. Studies performing direct comparison of these tests are needed, as well as analysis of the way these tests should direct decision making in infertility diagnosis and treatment.

Aging↗
PubMed1998

[Perioperative mortality and the role of anesthesiologic activity at the Vrije University Hospital in Amsterdam].

OBJECTIVE: To determine the perioperative mortality and the share of anaesthesiological activity in it. DESIGN: Retrospective, descriptive. SETTING: VU University Hospital, Amsterdam. METHOD: Patients who in the period 1989-1994 had died within 7 days after a clinical surgical intervention were identified using the database of the hospital information system. The following data concerning these patients were collected from the database of the department of Anaesthesiology: age, sex, classification according to the American Society of Anesthesiologists (ASA), urgency (elective or emergency operation), type of operation (12 categories), duration of the operation, time and place of death. Four independent investigators classified the deceased patients with the aid of their medical files as to the degree of connection between the anaesthesiological activity and the death according to the Edwards classification. RESULTS: A total of 62,969 operations had been performed. following which 314 patients (0.5%) had died within 7 days. Death was connected with the anaesthesiological activity in 16 cases (2.5 per 10,000 operations): there was a connection with the anaesthesiological activity exclusively in two patients (0.3 per 10,000 operations) and with both anaesthesiological and surgical factors in 14 patients (2.2 per 10,000 operations). Advanced age, male sex, a higher ASA category, traumatological operations and emergency operations were associated with a higher mortality rate. CONCLUSION: The mortality rate within 7 days after a clinical surgical intervention was 0.5%. A connection with anaesthesiological activity was present in 2.5 per 10,000 operations.

Adolescent↗
PubMed1998

Evaluation of catheter-mounted transducers for intra-oesophageal pressure recording in respiratory function tests.

Oesophageal pressure measurements in respiratory function tests are commonly performed using a balloon-catheter system. This study investigates the usefulness of catheter-mounted pressure transducers as an alternative to balloon-catheter systems. Calibration related physical properties of the catheter mounted pressure transducers are evaluated in vitro. The behaviour of these transducers in vivo is evaluated in ten volunteers by relating pressures measured in the oesophagus to airway opening pressures and by comparing these relationships with those sequentially obtained by a balloon-catheter system. The catheter-mounted pressure transducers show no drift after a proper preparation procedure. These catheters, with integrated pressure transducers, are tolerated significantly better by the subjects than are balloon catheters. The catheter-mounted pressure transducers are found to give an equivalent performance compared with the balloon-catheter system, if relative pressures are of interest. However, unpredictable and uncontrollable shifts in offset occur during the in vivo measurements, disturbing absolute pressure readings. Possible explanations for these shifts are the presence of bubbles and adhesion of mucus to the transducers, exerting Van der Waals forces, and contact with the tissue of the oesophageal wall. These shifts are found to be quite stable throughout a period of measurement and therefore of minor disturbance to relative pressure measurements, for instance in assessing the elastic properties of lungs.

Adult↗
PubMed1998

Intraoperative continuous hemofiltration for metabolic management in acute aortoiliac occlusion.

Acute aortoiliac occlusion, or Leriche's syndrome, carries a risk of the development of severe ischemia-reperfusion injury, characterized by electrolyte and acid-base balance disturbances. These injuries are often fatal, because of the rapid deterioration of multiple organ systems. We present a case in which we intraoperatively and postoperatively treated hyperkalemia and metabolic acidosis by high-volume, continuous, veno-venous hemofiltration, which is a recently developed form of continuous renal replacement therapy.

Acute Disease↗
PubMed1997

[Is the pulmonary artery catheter discredited because of ignorance?].

Recently in an observational study the use of a pulmonary artery catheter in critically ill patients was associated with an increase in both mortality and utilization of resources when compared with case-matched control patients. The authors corrected for selection bias by using a propensity score. The publication of this article elicited a flood of commentary in both medical journals and the lay press. Critical assessment of this study and other studies about pulmonary artery catheterization in our opinion supports the view that it is probably not the use of the catheter itself, but physicians' insufficient knowledge of right heart catheterization and the specific treatment resulting from its use that is at fault.

Cardiac Catheterization↗
PubMed1997

Endoluminal pulse oximetry combined with tonometry to monitor the perfusion of the sigmoid during and after resection of abdominal aortic aneurysm.

Early detection of colonic ischaemia after aortic grafting is essential if mortality is to be decreased when this complication develops. The aim of this study was to determine changes in the sigmoid colon during and after abdominal aortic grafting using endoluminal pulse oximetry (SmO2). Oxygen saturation was measured on the mucosa (SmO2) and serosa (SsO2) of 20 sequential patients undergoing elective surgery for abdominal aortic aneurysm; intramural pHi was also measured. Initially, all patients had a normal SmO2 in the sigmoid; however, before cross-clamping eight patients had a reduction in the SmO2. The pulse curve disappeared immediately after cross-clamping in 15 patients, with only five still showing a pulse curve in the sigmoid colon. Before declamping, 13 patients regained their pulse curve. The intraluminal pHi showed a large interindividual variation (2 S.D. approximately 0.4). Patients were classified into three groups according to SmO2: group A, no pulse; group B, diminished saturation (< 90%); and group C, normal saturation (> or = 90%). There was significant correlation with the pHi after cross-clamping in all groups. One patient who developed ischaemia of the sigmoid colon demonstrated a prolonged reduction in the SmO2, a decreased perioperative pHi, and an increased oxygen saturation in the inferior mesenteric vein during cross-clamping.

Aged↗
PubMed1997

Haemostasis during infrarenal aortic aneurysm surgery: effect of volume loading and cross-clamping.

OBJECTIVES: To study thrombin and plasmin activation during elective abdominal aortic aneurysm surgery. DESIGN: Prospective study. SETTING: University Hospital. MATERIALS: Nine consecutive patients undergoing elective surgery were included. The mean age was 72 years (range 60-79). Blood samples were drawn: (1) before induction of anaesthesia; (2) after induction and Swan Ganz catherisation; (3) just before cross-clamping; (4) before declamping; (5) 8 h postoperatively; (6) 18 h postoperatively. CHIEF OUTCOME MEASURES: Assays included: prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, prothrombin fragments (F 1 + 2), anti-thrombin III (ATIII), plasminogen, alpha 2-antiplasmin, haematocrit, platelet and serum protein for correction of haemodilution. Data were expressed as mean (S.D.). Differences between mean values were tested by means of the ANOVA for repeated measures and the Wilcoxon signed rank test. MAIN RESULTS: The APTT and TT did not change until heparinisation. The F 1 + 2 were already elevated preoperatively. After correction for haemodilution the AT III and alpha 2-antiplasmin decreased in time (p = 0.009 and 0.0023, respectively) and the F1 + 2 increased (p < 0.0001). Postoperatively (t5 and 6) the values normalised again. CONCLUSIONS: The coagulation and fibrinolytic systems are activated during and after elective aortic replacement. Standard tests, like the prothrombin and partial thromboplastin time, are unreliable when assessing the coagulation status of the patient.

Aged↗
PubMed1996

Analysis of P50 and oxygen transport in patients after cardiac surgery.

OBJECTIVE: To determine whether standard P50 after cardiac surgery decreases and whether decreased P50 is related to the transfusion of red blood cells (RBCs), acid-base changes, body temperature, oxygen parameters and/or duration of cardiopulmonary bypass (CPB). DESIGN: Pilot study in cardiac surgery patients. SETTING: University hospital. PATIENTS: 12 Consecutive elective cardiac surgery patients. INTERVENTIONS: Blood was taken before surgery, after CPB and in the intensive care unit until 18 h post-operatively. Cardiac output and oxygen consumption were measured. Buffy coat-poor RBCs were transfused, anticoagulated with citrate-phosphate-dextrose buffer and stored in saline-adenine-glucose-mannitol at 4 degrees C, when haemoglobin was < 5.6 mmol.l-1. MEASUREMENTS AND RESULTS: Standard P50 was calculated from measured partial pressure of oxygen and of carbon dioxide, pH and oxygen saturation in mixed venous blood (SvO2) using the Severinghaus formula. Median length of RBC storage was 25 days. Standard P50 after surgery was significantly lower than baseline value (p = 0.0001). The number of RBC units transfused and duration of CPB were conjointly associated with P50 (R2 = 0.72). Patients who received more RBCs consumed more oxygen. CONCLUSION: Cardiac surgery patients receiving more RBC units have lower standard P50 and consume more oxygen. P50 decreased more when the CPB took longer. Because a decrease in P50 implies a low ratio of mixed venous oxygen tension (PvO2) to SvO2, a shift in P50 should be taken into account when using SvO2 as a measure of global oxygen availability. When a direct measurement of SvO2 is not available, PvO2 should be used instead of calculated SvO2.

Analysis of Variance↗
PubMed1996

Sigmoidal ischaemia after aortic grafting, detected by endoluminal pulse oximetry.

Colonic ischaemia after abdominal aortic grafting is a severe complication. Late detection of transmural ischaemia will result in a high mortality rate. No simple specific methods are available to detect the early stage. The aim of this pilot study was to detect and monitor sigmoidal ischaemia after aortic surgery with a new endoluminal sigmoidal probe, based on pulse oximetry. Twelve patients with sigmoidal ischaemia were included, the endoluminal probe being introduced into the sigmoid at least 25 cm proximal to the anal verge. It is shown that with this method, mucosal and transmural ischaemia can be graded and differentiated. Patients who showed no wave-form had transmural ischaemia; those with mucosal ischaemia showed reliable wave-forms with oxygen saturation from 40-85%. Colonic ischaemia after aortic grafting can be detected by endoluminal pulse oximetry but the clinical outcome will only improve by early detection in the preclinical stage.

Aged↗