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Biomedical subjects

E Mertens

Publications and source records attributed to E Mertens.

At least 19 recordsLinked to original sources
PubMed2003

Effect of preoperative beta-blockade on perioperative mortality in coronary surgery.

BACKGROUND: Many preoperative factors can influence perioperative mortality in cardiac surgery. Because the perioperative use of beta-blocking agents may reduce perioperative cardiac complications in non-cardiac surgery, we considered the possibility that beta-blocking agents could improve survival in coronary surgery patients. METHODS: In a retrospective study on 1586 patients undergoing coronary bypass surgery, the relative risk of 30-day mortality was determined in relation to preoperative risk factors and medication. Factors included patient characteristics, pre-existing illness, specific cardiovascular risk factors, cardiac status and urgency of surgery. Treatment with beta-blocking agents, calcium antagonists, angiotensin-converting enzyme inhibitors, nitrates, anti-arrhythmic agents, diuretics and antithrombotic agents was taken into account. RESULTS: Sex, age, chronic obstructive pulmonary disease, urgency and the preoperative use of diuretics and chronic beta-blocking therapy were found to be linked to mortality (P<0.05). Backward stepwise regression testing identified age, urgency and beta-blocking therapy as independent factors that could predict mortality. CONCLUSIONS: Increasing age and urgency of surgery are associated with greater mortality, whereas preoperative beta-blocking therapy is associated with less mortality. The characteristics of patients who received chronic beta-blockade did not differ significantly from those of patients who did not. The results suggest that chronic preoperative beta-blocker therapy reduces 30-day mortality in coronary surgery.

Adrenergic beta-Antagonists↗
PubMed2002

Effects of phosphodiesterase III inhibition on length-dependent regulation of myocardial function in coronary surgery patients.

BACKGROUND: Phosphodiesterase III inhibitors increase myocardial contractility and decrease left ventricular (LV) afterload. We studied whether these effects altered LV response to an increase in cardiac load and affected length-dependent regulation of myocardial function. METHODS: Before the start of cardiopulmonary bypass, a high-fidelity pressure catheter was positioned in the left ventricle and the left atrium in 10 coronary surgery patients. LV response to an increased cardiac load, caused by leg elevation, was assessed during baseline conditions and after administration of milrinone at a dose of 20 micrograms kg-1 over 15 min. Effects on contraction were measured by changes in maximal rate of pressure development (dP/dtmax). Effects on relaxation were assessed by analysis of changes in maximum rate of pressure decrease and by analysis of the load dependency of myocardial relaxation (R = slope of the relation between the time constant of isovolumic relaxation and end systolic pressure). RESULTS: Milrinone increased dP/dtmax but measures of relaxation were unaltered. Leg elevation had more effect on measures of contraction and relaxation after milrinone than at baseline. The relationship between R and changes in dP/dtmax shifted downwards and to the right with milrinone, whereas the relationship between R and changes in end diastolic pressure (EDP) shifted downwards and to the left. CONCLUSIONS: This suggests that milrinone improved contraction, reduced the load dependency of LV pressure decrease, and reduced the change in EDP after leg elevation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2001

The effects of the pericardium on length-dependent regulation of left ventricular function in coronary artery surgery patients.

OBJECTIVE: To analyze the effects of the pericardium on the length-dependent regulation of myocardial function in coronary artery surgery patients. DESIGN: Prospective. SETTING: University hospital. PARTICIPANTS: Patients scheduled for elective coronary artery surgery. INTERVENTIONS: In 10 patients, a combined micromanometer transducer conductance catheter was inserted into the left ventricle for measurement of left ventricular pressures and volumes. MEASUREMENTS AND MAIN RESULTS: Consecutive data were obtained during a progressive increase in left ventricular pressures and volumes obtained by leg elevation in closed chest-closed pericardium and open chest-open pericardium conditions. Pericardiotomy did not alter baseline left ventricular hemodynamics. The effects of leg elevation were different, however. In closed chest-closed pericardium conditions, stroke volume and stroke work remained unchanged, whereas these parameters increased in open chest-open pericardium conditions. This increase was related to the increase in end-diastolic volume that was observed in open chest-open pericardium conditions and not in closed chest-closed pericardium conditions. CONCLUSIONS: In coronary artery surgery patients, pericardiotomy does not alter baseline left ventricular function. When cardiac load is increased by leg elevation, however, use of the Frank-Starling mechanism is enhanced in open chest-open pericardium conditions.

Coronary Vessels↗
PubMed2001

Target controlled infusion of remifentanil and propofol for cesarean section in a patient with multivalvular disease and severe pulmonary hypertension.

A 36 year old parturient with known valvular heart disease was admitted with respiratory distress and fatigue after 35 weeks of pregnancy. Echocardiography revealed severe tricuspid regurgitation, mitral stenosis and aortic valve insufficiency. Following clinical examination and insertion of a radial and pulmonary artery catheter it was decided to perform a Caesarean Section. The pulmonary artery pressure upon arrival in the operating theatre was 105/50 mm Hg whereas cardiac output was 3.5 l/min. Induction of anesthesia was performed with a target controlled infusion of remifentanil and propofol combined with rocuronium bromide. Haemodynamic variables remained very stable during and after intubation. The lungs of the apnoeic baby were manually ventilated until spontaneous respiration began at 1 minute post delivery. Apgar scores were 3, 7 and 9 after 1, 5 and 10 minutes respectively. Umbilical artery pH was 7.29. The patient's haemodynamic status gradually improved over the following few days. Two months following delivery she underwent unevenful valvular surgery.

Adult↗
PubMed2000

Prevention of hypotension by a single 5-mg dose of ephedrine during small-dose spinal anesthesia in prehydrated cesarean delivery patients.

UNLABELLED: To evaluate the effectiveness of prophylactic ephedrine for the prevention of hypotension associated with spinal anesthesia, 50 parturients undergoing cesarean delivery received either ephedrine 5 mg or saline IV in a double-blinded fashion immediately after the induction of spinal anesthesia. Spinal anesthesia was performed with hyperbaric bupivacaine 6.6 mg combined with sufentanil 3.3 microg as part of a combined spinal-epidural technique. All patients received 1000 mL of lactated Ringer's solution and 500 mL of hydroxyethylstarch 6% before the spinal injection. Additional ephedrine boluses (5 mg) were administered IV when the systolic blood pressure or heart rate decreased by more than 30% from baseline values, when systolic blood pressure became <100 mm Hg, or when patients complained of nausea or feeling faint. The height of the block was equal in the groups; however, more patients in the placebo group were found to develop hypotension (58% vs 25%, P < 0. 05). Only 2 (8%) patients in the ephedrine group developed hypotension with systolic blood pressure values <90 mm Hg, whereas 10 patients (42%) in the saline group experienced hypotension of this severity (P < 0.05). In addition, there was a higher incidence of nausea in the placebo-treated patients. The total amount of ephedrine administered did not differ between groups. These findings suggest that the incidence and severity of hypotension are significantly reduced by the IV administration of a prophylactic dose of 5 mg ephedrine in patients receiving small-dose spinal anesthesia for cesarean delivery. IMPLICATIONS: Ephedrine is the drug most often used to correct hypotension during spinal anesthesia for cesarean delivery in healthy patients. A single IV dose of 5 mg decreases the occurrence and limits the severity of hypotension in prehydrated subjects receiving a small-dose spinal local anesthetic-opioid combination.

Adult↗
PubMed1999

Seven-year review of requests for epidural blood patches for headache after dural puncture: referral patterns and the effectiveness of blood patches.

A review was undertaken of all 190 patients who were referred over 7 years, from 1991 to 1997 inclusive, for an epidural blood patch as a treatment for headache after dural puncture. The patterns of referral and symptoms, the distributions of age and gender and the effectiveness of the blood patch were examined. Most of the referrals (n = 153) were after deliberate diagnostic dural puncture in neurology and neuroradiology, with a minority (n = 28) used for anaesthesia and obstetrics, which were mostly inadvertent. Another nine cases were related to placement of an intrathecal catheter. The numbers of referrals per year reached a maximum in 1995 before falling again, a curious inverse relation to the number of invasive neuro-radiological diagnostic procedures. Most of the patients were between 30 and 50-years-old, with 25 younger than 30 and 14 older than 60. Women accounted for 70% of the referrals for headache, although the gender ratio amongst patients subjected to at risk procedures appeared closer to 50:50. Neckache accompanied the headache in 85% of cases, auditory problems were volunteered by three patients and one patient had diplopia for 6 weeks. Of the 190 patients who were referred, 186 received at least one patch, the symptoms in the remaining four being too mild or atypical to warrant blood patch treatment. This provided initial relief in all but two patients, one of whom received a further epidural blood patch with no effect. There was sustained relief of symptoms in 136 and a partial relapse in 38 patients, which resolved without needing any further blood patch. A second patch was provided for seven patients and a third for three patients, of whom two were cured. Of the patients who needed more than one blood patch, nine were after inadvertent dural puncture with a Tuohy needle and, of these patients, six were in labour. A total of 200 patches were provided in all for the 186 patients and all but three patients had a satisfactory outcome. Epidural blood patches are effective in treating headache after dural puncture, but less successful than is commonly believed, especially after inadvertent dural taps. A relapse after treatment does not always require a second patch. Specialities other than anaesthesia seemed reluctant to accept the benefits in both cost and comfort of using needles of improved design for dural puncture.

Adult↗
PubMed1999

Patient-controlled extradural analgesia after caesarean section: a comparison between tramadol, sufentanil and a mixture of both.

In a double-blind randomised study into post-operative pain relief by extradural PCA, 66 Caesarean section patients were divided in to three groups to receive either sufentanil (2 µ g/ml), tramadol (10 mg/ml) or a mixture of both. After a loading dose of 10 ml, patients were allowed to ask for additional boluses of 2.5 ml, respecting a lock-out time of 10 min and a 1-h limit of 10 ml. Every 6 h, VAS pain scores, consumption of drugs, number of demands and side-effects were registered.At 6 h, pain was significantly less in the combination group compared to patients receiving tramadol alone. The 24-h dose requirements for sufentanil and tramadol when used alone were 123.5+/-10.3 µ g and 652+/-42 mg, respectively. Combining both drugs decreased the consumption and number of demands for tramadol only (22%, p<0.05 vs 18% for sufentanil, NS). In the tramadol groups, more failures and significantly more side-effects, mainly nausea and vomiting, were noticed.It may be concluded that the extradural use of tramadol is less beneficial than previously reported. Due to disturbing side-effects, relatively high dose requirements (even after the addition of a lipophilic opioid) and somewhat inferior analgesic quality, its extradural administration for postoperative pain relief cannot be recommended. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗
PubMed1999

Postoperative analgesia with i.v. patient-controlled morphine: effect of adding ketamine.

We have studied the effect of adding ketamine to i.v. morphine patient-controlled analgesia (PCA) for the treatment of pain after laparotomy. Thirty patients were allocated randomly to receive PCA with saline or ketamine in a double-blind, randomized study. Analgesia was started in the recovery room when visual analogue scale (VAS) scores were > 4. A bolus dose of morphine 3 mg was given to all the patients followed by i.v. PCA. Simultaneously, an infusion of ketamine 2.5 micrograms kg-1 min-1 or saline was started. Pain scores, morphine consumption and side effects were noted for up to 48 h after the start of PCA. VAS scores decreased significantly with time (P = 0.0001) and were similar (P = 0.3083) in both groups. Cumulative morphine consumption at 48 h was significantly lower in the ketamine group (28 mg) than in the control group (54 mg) (P = 0.0003). Nausea was less frequent in the ketamine group (P = 0.03).

Adolescent↗
PubMed1999

Contraction-relaxation coupling and impaired left ventricular performance in coronary surgery patients.

BACKGROUND: Dependence of left ventricular (LV) relaxation on cardiac systolic load is a function of myocardial contractility. The authors hypothesized that, if a tight coupling would exist between LV contraction and relaxation, the changes in relaxation rate with an increase in cardiac systolic load would be related to the changes in LV contraction. METHODS: Coronary surgery patients (n = 120) with preoperative ejection fraction >40% were included. High-fidelity LV pressure tracings (n = 120) and transgastric transesophageal echocardiographic data (n = 40) were obtained. Hearts were paced at a fixed rate of 90 beats/min. Effects on contraction were evaluated by analysis of changes in dP/dt(max) and stroke area. Effects on relaxation were assessed by analysis of R (slope of the relation between tau and end-systolic pressure). Correlations were calculated with linear regression analysis using Pearson's coefficient r. RESULTS: Baseline LV end-diastolic pressure was 10+/-3 mm Hg (mean +/- SD). During leg raising, systolic LV pressure increased from 93+/-9 to 107+/-11 mm Hg. The change in dP/dt(max) was variable and ranged from -181 to +254 mm Hg/s. A similar variability was observed with the changes in stroke area, which ranged from -2.0 to +5.5 cm2. Changes in dP/dt(max) and in stroke area were closely related to individual R values (r = 0.87, P<0.001; and r = 0.81, P<0.001, respectively) and to corresponding changes in LV end-diastolic pressure (r = 0.81, P< 0.001; and r = 0.74, P<0.001, respectively). CONCLUSIONS: A tight coupling was observed between contraction and relaxation. Leg raising identified patients who developed a load-dependent impairment of LV performance and increased load dependence of LV relaxation.

Aged↗
PubMed1998

Evidence for a new type of outer membrane lipid in oral spirochete Treponema denticola. Functioning permeation barrier without lipopolysaccharides.

A new class of outer membrane lipid (OML) was isolated from the oral spirochete Treponema denticola strain ATCC 33521 using a phenol/chloroform/light petroleum procedure normally applied for lipopolysaccharide extraction. In addition to chemical analysis, Fourier transform infrared (FTIR) spectroscopy was applied to compare the biophysical properties of OML with lipopolysaccharides (LPS) and lipoteichoic acids (LTA). Isolated OML fractions represent 1.4% of the total dry cell weight, are about 4 kDa in size, and contain 6% amino sugars, 8% neutral sugars, 14% phosphate, 35% carbazol-positive compounds, and 11% fatty acids (containing iso- and anteiso-fatty acyl chains). Rare for outer membrane lipids, OML contains no significant amount of 3-deoxy-D-manno-octulosonic acids, heptoses, and beta-hydroxy fatty acids. The fatty acyl chain composition, being similar to that of the cytoplasmic membrane, is quite heterogeneous with anteiso-pentadecanoic acid (12%), palmitic acid (51%), and iso-palmitic acid (19%) as the predominant fatty acids present. Findings of a glycerol-hexose unit and two glycerol-hexadecanoic acid fragments indicate a glycolipid membrane anchor typically found in LTA. There was also no evidence for the presence of a sphingosine-based lipid structure. The results of FTIR measurements strongly suggest that the reconstituted lipid forms normal bilayer structures (vesicles) expressing a high membrane state of order with a distinct phase transition as typical for isolated LPS. However, in contrast to LPS, OML of T. denticola has a lower Tm near 22 degreesC and a lower cooperativity of the phase transition. The results suggest a different kind of permeation barrier that is built up by this particular OML of T. denticola, which is quite different from LPS normally essential for Gram-negative bacteria.

Cell Membrane Permeability↗
PubMed1998

The pyrophosphate-dependent phosphofructokinase of the protist, Trichomonas vaginalis, and the evolutionary relationships of protist phosphofructokinases.

The pyrophosphate-dependent phosphofructokinase (PPi-PFK) of the amitochondriate protist Trichomonas vaginalis has been purified. The enzyme is a homotetramer of about 50 kDa subunits and is not subject to allosteric regulation. The protein was fragmented and a number of peptides were sequenced. Based on this information a PCR product was obtained from T. vaginalis gDNA and used to isolate corresponding cDNA and gDNA clones. Southern analysis indicated the presence of five genes. One open reading frame (ORF) was completely sequenced and for two others the 5' half of the gene was determined. The sequences were highly similar. The complete ORF corresponded to a polypeptide of about 46 kDa. All the peptide sequences obtained were present in the derived sequences. The complete ORF was highly similar to that of other PFKs, primarily in its amino-terminal half. The T. vaginalis enzyme was most similar to PPi-PFK of the mitochondriate heterolobosean, Naegleria fowleri. Most of the residues shown or assumed to be involved in substrate binding in other PPi-PFKs were conserved in the T. vaginalis enzyme. Direct comparison and phylogenetic reconstruction revealed a significant divergence among PPi-PFKs and related enzymes, which can be assigned to at least four distantly related groups, three of which contain enzymes of protists. The separation of these groups is supported with a high percentage of bootstrap proportions. The short T. vaginalis PFK shares a most recent common ancestor with the enzyme from N. fowleri. This pair is clearly separated from a group comprising the long (>60-kDa) enzymes from Giardia lamblia, Entamoeba histolytica pfk2, the spirochaetes Borrelia burgdorferi and Trepomena pallidum, as well as the alpha- and beta-subunits of plant PPi-PFKs. The third group ("X") containing protist sequences includes the glycosomal ATP-PFK of Trypanosoma brucei, E. histolytica pfk1, and a second sequence from B. burgdorferi. The fourth group ("Y") comprises cyanobacterial and high-G + C, Gram-positive eubacterial sequences. The well-studied PPi-PFK of Propionibacterium freudenreichii is highly divergent and cannot be assigned to any of these groups. These four groups are well separated from typical ATP-PFKs, the phylogenetic analysis of which confirmed relationships established earlier. These findings indicate a complex history of a key step of glycolysis in protists with several early gene duplications and possible horizontal gene transfers.

Amino Acid Sequence↗
PubMed1996

Central retinal artery occlusion after spinal surgery.

Central retinal artery occlusion can be caused by excessive extrinsic pressure on the eyeball during surgery. It is a rare and severe complication after elective spinal surgery. The authors report a case of central retinal artery occlusion in an adult after posterior lumbar spinal fusion in which a rectangular headrest was used.

Adult↗
PubMed1995

Central retinal artery occlusion after back surgery: a case report.

Central retinal artery occlusion can be caused by excessive extrinsic pressure on the eyeball during surgery. It is a well-known and severe complication after elective back surgery. The authors report a case of central retinal artery occlusion in an adult after posterior lumbar fusion in which a rectangular headrest was used.

Adult↗
PubMed1993

Pyrophosphate-dependent phosphofructokinase from the amoeba Naegleria fowleri, an AMP-sensitive enzyme.

PPi-dependent phosphofructokinase (PPi-PFK) was detected in extracts of the amoeba Naegleria fowleri, with a specific activity of about 15-30 nmol/min per mg of protein, which was increased about 2-fold by 0.5 mM AMP. PPi-PFK was inactivated upon gel filtration and could be re-activated by incubation at 30 degrees C in the presence of AMP. N. fowleri PPi-PFK was purified more than 1100-fold to near homogeneity with a yield of about 25%. The pure enzyme had a specific activity of 65 mumol/min per mg of protein, and SDS/PAGE analysis showed a single band, of 51 kDa. Size-exclusion chromatography revealed the existence of two forms: a large one (approximately 180 kDa), presumably a tetramer, which was active, and a smaller one (approximately 45 kDa), presumably the monomer, which was inactive, but could be re-activated and converted into the large form by incubation at 30 degrees C in the presence of 0.5 mM AMP. Reactivation was also observed at 30 degrees C in the absence of AMP, particularly at higher enzyme concentration or in the presence of poly(ethylene glycol). Inactivation of the tetrameric enzyme was promoted by 0.25 M potassium thiocyanate. The enzyme displayed Km values of 10 and 15 microM for fructose 6-phosphate and PPi, respectively, in the forward reaction, and of 35 and 590 microM for fructose 1,6-bisphosphate and Pi in the backward reaction. The activity was dependent on the presence of Mg2+. AMP increased Vmax. about 2-fold without changing the affinity for the substrates; its half-maximal effect was observed at 2 microM.

Adenosine Monophosphate↗
PubMed1993

Identification, purification and separation of different isozymes of NADP-specific malic enzyme from Tritrichomonas foetus.

Tritrichomonas foetus was found to contain NADP-specific malic enzyme. The activity was present in the cytosolic fraction and was about 5-fold higher in extracts of a metronidazole-resistant strain (KV1-1MR-100) than of the parent strain (KVc1). Electrophoresis under non-denaturing conditions and activity staining indicated the existence of 3 isozymes termed I, II and III in order of increasing electrophoretic mobility. Isozymes I and II were much less active than isozyme III in the parent strain, whereas all three isozymes had comparable activities in the resistant strain. NADP-malic enzymes were purified from the cytosolic fraction of the resistant strain to apparent homogeneity and were identified by SDS-PAGE as polypeptides of 41.5 kDa (I), 40.5 kDa (III) and as a mixture of both in equal amounts (II). The molecular mass of the three holoenzymes was about 180 kDa, as determined by gel-filtration on Sephacryl S-300 HR, indicating a tetrameric structure. Isozyme III was also purified from parent strain and shown to consist of the 40.5-kDa polypeptide. Km values for malate were 0.31, 0.65 and 1.35 mM for isozyme I, II and III, respectively. From these results we conclude that T. foetus+, which is required for the formation of ethanol by alcohol dehydrogenase, an NADP-specific enzyme in this species. This is particularly important for the resistant strain, in which ethanol is the major end-product of glucose metabolism.

Animals↗
PubMed1993

ATP versus pyrophosphate: glycolysis revisited in parasitic protists.

It is generally assumed that glycolysis is remarkably similar among all organisms, prokaryotic and eukaryotic. This view has been extended to protists. However, there is growing evidence that significant deviations from conventional glycolysis occur in protists. Very different species, some parasitic, rely on peculiar enzymes that use pyrophosphate as substrate. In this review, Emmanuel Mertens describes such unusual pyrophosphate metabolism in parasitic protists.

Journal Article↗