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Biomedical subjects

R Larsen

Publications and source records attributed to R Larsen.

At least 127 records · Page 7Linked to original sources
PubMed1993

Haemodynamic changes produced by inhalation anaesthetics in the presence of phosphodiesterase inhibition.

We have investigated the circulatory effects of halothane and isoflurane in the presence of the phosphodiesterase inhibitor, enoximone, in 20 patients, ASA class III, aged 40-70 yr, undergoing coronary artery bypass grafting. After induction of anaesthesia (midazolam, fentanyl, etomidate and pancuronium) all patients received enoximone 0.5 mg kg-1, followed, 10 min later, by either halothane 1 MAC (group I; n = 10) or isoflurane 1 MAC (group II; n = 10). Haemodynamic variables were measured and blood samples (arterial and mixed venous) were obtained before (control, t0), 5 (t1) and 10 (t2) min after the injection of enoximone and immediately (t3) and 5 (t4) min after steady state conditions with halothane or isoflurane, as verified by the end-expiratory concentration. Heart rate, mean arterial pressure (MAP), mean pulmonary artery pressure, pulmonary capillary wedge pressure and right atrial pressure were recorded. Cardiac (CI) and stroke volume indices, systemic (SVR) and pulmonary vascular resistance, oxygen availability (QO2), oxygen consumption and oxygen extraction rate were calculated using standard formulae. MAP decreased significantly in both groups after bolus injection of enoximone (group I: 11%; group II: 7%). Under steady state conditions with the volatile anaesthetics, a further significant decrease in MAP was observed (group I: 12%; group II: 12%). Enoximone produced a significant increase in CI (group I: 25%; group II: 27% compared with control). After administration of isoflurane, CI remained essentially unchanged, while halothane decreased CI significantly by 20%. In both groups, SVR decreased significantly after administration of enoximone (group I: 26%; group II: 24%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Epidemic meningococcemia and purpura fulminans with induced protein C deficiency.

Patients with epidemic infections caused by Neisseria meningitidis serogroup C were studied to assess the relationship of abnormal coagulation parameters to prognosis. Patients were categorized into stages within the first hour of observation according to severity of illness. During the epidemic years 1986 through 1991, 113 patients with bacteriologically proven N. meningitidis infection were observed, 15 of whom died. Purpura fulminans was seen in 28 patients, of whom 14 (50%) died. Among the 14 surviving patients who had purpura fulminans, 10 suffered gangrene with deforming autoamputation secondary to the dermal microvascular thrombosis and hemorrhagic necrosis. Evaluation of the induced diffuse intravascular coagulation in 59 patients included studies of the naturally occurring anticoagulants, focusing on protein C and protein S. The magnitude of the declining levels of protein C, the degree of thrombocytopenia, and the presence of fibrin split products are directly related to the clinical severity of the illness (P = .0053). Thus, in individuals with severe disease expression, the risk of purpura fulminans with death or deformity was significantly increased when the platelet count was < 50,000 cells/mm3 (P = .0001) and protein C levels were low (P = .0158). The immaturity of the protein C system in children who are < 4 years of age may contribute to the rapid and more frequent pathogenesis of purpura fulminans. Therapy directed at replacement of the naturally occurring anticoagulants, such as protein C, may ultimately improve the prognosis for individuals with purpura fulminans.

Adolescent↗
PubMed1993

Comparative effects of crystalloid and small volume hypertonic hyperoncotic fluid resuscitation on hepatic microcirculation after hemorrhagic shock.

Hepatic microcirculation, leukocyte-endothelial interaction, and sinusoidal widths were studied by means of intravital microscopy in a non-heparinized fixed pressure hemorrhagic shock model in the rat. Asanguineous resuscitation was performed either with "adequate" amounts of lactated Ringer's solution (threefold shed volume/30 min) or 4 ml/kg/3 min 7.2% saline/10% Dextran 60 (HSDex) or 4 ml/kg/3 min 7.2% saline/10% hydroxyethylstarch 200/0.62 (HSHes). Hemorrhagic shock and resuscitation was paralleled by significant (P < 0.01) lumenal narrowing of sinusoids that remained largely uninfluenced by the type of fluid used for resuscitation (HSDex: 9.28 +/- 0.56; HSHes: 8.93 +/- 0.29, LR: 8.87 +/- 0.6 microns compared to 12.17 +/- 0.24 microns in controls). Whereas HSHes and LR-therapy resulted in comparably increased leukocyte adhesion to the sinusoidal wall, the dextran-containing solution led to a significant attenuation of leukocyte-endothelial interaction, suggesting involvement of dextran-binding adhesion molecules, e.g., selectins.

Animals↗
PubMed1993

[Comparative effectiveness and tolerance study of a new galenic etomidate formula].

OBJECTIVE AND STUDY DESIGN: One of the major disadvantages of etomidate is the high frequency of pain on injection. A new galenic formulation based on a lipid emulsion for etomidate (Etomidat-Lipuro) was compared with the commercial standard (etomidate in propylene glycol, Hypnomidate) in a prospective, randomised, double-blind clinical evaluation in 232 patients undergoing elective surgery in general anaesthesia. The patients were premedicated with flunitrazepam 2 hours before the investigation. Two intravenous cannulas were inserted in veins of forearm or back of the hand. One cannula was only used for the application of etomidate and removed immediately after injection. General anaesthesia was induced with 0.3 mg/kg etomidate at an injection rate of 20 mg/30 s. If the patient did not complain of pain or other sensations during injection spontaneously, he was questioned for 15 s after beginning of injection. The arm used for application of etomidate was kept free of any manipulation during the operation and the following five postoperative days. RESULTS: There were marked differences between the two etomidate preparations concerning venous irritation. About 20% of the patients receiving the hypnotic in propylene glycol complained spontaneously of pain on injection, whereas none with the lipid emulsion. No difference was found in the incidence of myoclonic movements. The time interval between the beginning of injection and loss of eyelid closure reflex was about 50 s and not different for the two galenic formulations. Blood pressure during and after induction of anaesthesia did not differ. The heart rate in the group of patients with etomidate in lipid emulsion was slightly increased before and immediately after intubation compared to the propylene glycol group. 4% of the patients in the propylene glycol group suffered from postoperative venous complications as reddening, swelling, induration or pain. These complications could not be seen in the lipid emulsion group.

Adult↗
PubMed1992

[Spinal anesthesia for surgery of inguinal hernia in infants at risk for respiratory complications. Initial experiences with 12 patients].

11 former premature babies born at a mean gestational age of 32 weeks (range 27-34 weeks) and one baby born at term with congenital diaphragmatic hernia scheduled for inguinal hernia repair were selected to receive a spinal anaesthesia after informed written consent was obtained from one of the parents. At birth, 10 infants were intubated and received assisted ventilation; the remaining two were on nasal CPAP for 24 hours after birth. The mean post-conceptual age of the former premature infants on the day of surgery was 39 weeks (range 36-43 weeks), the mean weight was 2.2 kg (range 1.8 to 3.6 kg). One boy with congenital diaphragmatic hernia who was intubated for 19 days after birth aged 4 months on the day of operation and weighed 5.3 kg. None of the children was oxygen-dependent on the day of surgery. Spinal anaesthesia was performed in 3 children in the lateral decubitus and in 9 children in the sitting position. In each group, there was one case when spinal anaesthesia could not be performed due to a bloody spinal tap. These children received general anaesthesia, one of them in combination with a caudal block. The 9 former premature received 0.6 ml isobaric bupivacaine 0.5%, and the child born on term with diaphragmatic hernia 0.8 ml isobaric bupivacaine 0.5%. The onset of the motor blockade in the former preterm infants was within 60-90 seconds, while in the older child the onset was 10 minutes. With the given dose, the operation could be performed without any problems.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Spinal↗
PubMed1992

[Effect of the volatile anesthetics halothane, enflurane and isoflurane on liver circulation in the human].

In 40 patients with normal liver function total hepatic blood flow (HBF) was determined by the indocyanine-green clearance method simultaneously with haemodynamic parameters, including cardiac output by means of the noninvasive thoracic electrical bioimpedance method. Furthermore, the influence of halothane, enflurane or isoflurane on HBF and the interaction with haemodynamic parameters was studied. HBF and the cardiocirculatory parameters were determined under normal conditions (waking state) and the 40 patients were then divided into 4 groups (each n = 10). After standardised induction of anaesthesia (0.3 mg/kg etomidate and 2 micrograms/kg fentanyl) and tracheal intubation (1.5 mg/kg suxamethonium chloride) an inhalation anaesthesia in O2/air under control of normal end tidal carbon dioxide concentration was performed by intermittent positive pressure ventilation. Anaesthesia was maintained in the 4 groups either with 1 MAC halothane, 1 MAC enflurane, 1 MAC isoflurane or 1.3 MAC isoflurane. The measurements were repeated at a steady of the desired end expiratory concentration of the respective volatile anaesthetic. All three anaesthetics produced a significant and comparable decrease of cardiac output and arterial blood pressure. Differences between halothane, enflurane and isoflurane in respect of haemodynamic parameters were only minimal. Contrariwise, marked differences could be seen in the effects of the anaesthetics on HBF. In the presence of halothane and enflurane HBF dropped to 58% and 56% resp. of the control value, whereas during isoflurane anaesthesia HBF remained unchanged. Furthermore, only during halothane anaesthesia a significant correlation between arterial blood pressure and HBF could be observed indicating a loss of autoregulation of the hepatic blood flow.

Adolescent↗
PubMed1991

The nature of Cux in cytochrome c oxidase.

We report here extensive and accurate analyses of the copper, iron, zinc, and magnesium contents in bovine heart cytochrome c oxidase by direct current plasma atomic emission spectrometry. The precision of an individual measurement is within +/- 5%. The analyses confirm a stoichiometry of 5Cu/4Fe/2Zn/2Mg per dimer. Seven enzyme preparations treated by various methods are also analyzed to investigate the nature of Cux. It is shown that Cux is removable by either monomerization of the enzyme or subunit III depletion. This result suggests that Cux is associated with subunit III and that it plays a structural role in enzyme dimerization. EPR measurements indicate that Cux is heterogeneous and mostly reduced. In addition, we find Cux has no effect on the spectroscopic properties and electron transfer activity of the enzyme.

Animals↗
PubMed1991

Molecular characterization of the gene encoding a rice endosperm-specific ADPglucose pyrophosphorylase subunit and its developmental pattern of transcription.

The gene encoding a rice endosperm-specific ADPglucose pyrophosphorylase (AGPP) subunit was isolated and its structure determined by nucleotide (nt) sequencing. A comparison of the genomic and cDNA nt sequences revealed a complex gene structure with ten exons and nine introns spanning over 6 kb. The exons ranged in size from 293 to 99 nt and the introns were between 1435 and 84 nt in size, with the first intron being the largest. All of the intron splice sites, except intron-2, contained GT/AG borders and were similar to the published splice site consensus sequences. Intron-2 had CA/CC borders at the 5' and 3' ends, but sequences adjacent to the splice site borders shared homology to the splice site consensus sequence, suggesting that the overall splice region, rather than the specific GT/AG sequence, determines the splice site. Several sequence motifs which may play a role in the regulation of plant genes were evident upstream from the transcriptional start point. Analysis of the developmental pattern of expression revealed a maximum level of mRNA transcripts for AGPP at five days after flowering coincident with starch accumulation. This result suggests that starch biosynthesis is controlled at the transcriptional level during seed development.

Amino Acid Sequence↗
PubMed1991

Comparison of sufentanil-nitrous oxide anaesthesia with fentanyl-nitrous oxide anaesthesia in geriatric patients undergoing major abdominal surgery.

We have measured haemodynamic changes and plasma concentrations of catecholamines during sufentanil-nitrous oxide and fentanyl-nitrous oxide anaesthesia in a controlled, randomized, double-blind study of 20 geriatric patients (age 65-86 yr) undergoing major abdominal surgery. Fentanyl 7 micrograms kg-1 followed by infusion of 3 micrograms kg-1 h-1 was compared with sufentanil 1 micrograms kg-1 followed by 0.4 micrograms kg-1 h-1. The opioid was supplemented with 60-67% nitrous oxide in oxygen. Haemodynamic changes, plasma concentrations of catecholamines (by high pressure liquid chromatography) and opioids (by radioimmunoassay), and myocardial lactate extraction were measured in the awake state, and at defined times during anaesthesia and surgery. Haemodynamic state was stable during induction and tracheal intubation in both groups, while during stressful operative periods there were increases in mean arterial pressure (17% in the fentanyl group; 11% in the sufentanil group), heart rate (fentanyl 20%, sufentanil 14%) and plasma concentrations of catecholamines (adrenaline: fentanyl 316%, sufentanil 86%; noradrenaline: fentanyl 78%, sufentanil 186%) in both groups. Sufentanil was similar to fentanyl in attenuating the haemodynamic and hormonal responses to surgical stimulation. In two patients in the fentanyl group and three in the sufentanil group, myocardial lactate production was observed temporarily, indicating myocardial ischaemia caused by surgical stress.

Abdomen↗
PubMed1991

Treatment of azotemic, nonoliguric, anemic patients with human recombinant erythropoietin raises whole-blood viscosity proportional to hematocrit.

It has been reported that patients with azotemia have reduced red blood cell (RBC) deformability. Since this is a major determinant of whole-blood viscosity (WBV) and rigid RBCs increase WBV disproportionately relative to the level of hematocrit, it is conceivable that sustained improvement of hematocrit with recombinant human erythropoietin (rhEPO) therapy in azotemic patients might result in abnormally raised WBV. To address this concern, WBV and plasma viscosity (PV) were measured in 9 adult patients (4 men, 5 women) with anemia (mean hematocrit 29.2 +/- 2.7%) and azotemia [mean serum creatinine concentration 339.85 +/- 102.44 mumol/l (3.8 +/- 1.1 mg/dl)] before and after 6 months of treatment with rhEPO (50-175 U/kg given intravenously thrice weekly). Baseline and post-treatment hematocrit, WBV and PV were compared to values derived in 50 normal adult subjects with normal renal function [25 women, 25 men; mean serum creatinine concentration 79.56 +/- 8.84 mumol/l (0.9 +/- 0.1 mg/dl), mean hematocrit 42.4 +/- 3.7%]. To compare rheologic factors at subnormal hematocrits, blood from subjects with normal renal function was diluted with autologous plasma to achieve a range of hematocrits from 20 to 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Cardiac output and liver blood flow in humans: effect of the volatile anesthetic halothane.

In 40 men with normal circulatory and liver function, from whom 10 were undergoing general anesthesia with halothane for minor orthopedic surgery, the relationship between hemodynamic parameters and total hepatic blood flow (HBF) was investigated. Cardiac output (CO) was measured noninvasively by means of the thoracic electrical bioimpedance method, systemic arterial blood pressure (BPsys, BPdia, mean arterial pressure) by an automated oscillometric device and HBF by indocyanine green clearance. In the subjects without halothane anesthesia no relationship was found between BP and HBF, but a significant correlation could be seen between CO and HBF, whereby the fraction of HBF decreased with increasing CO. In contrast, in the presence of halothane the systemic arterial blood pressure correlated with the HBF, indicating a loss of autoregulation of the liver circulation.

Adult↗
PubMed1990

[Propofol infusion for sedation in regional anesthesia. A comparison with midazolam].

50 non-premedicated ASA class I or II patients were allocated randomly into two groups and received either a variable infusion of propofol or midazolam for sedation during orthopaedic surgery with regional blockade. To achieve a well-sedated patient with eyes closed and able to follow commands, the dose requirements for propofol were 1.25 mg/kg +/- 0.5 as a loading dose followed by a mean infusion rate of 3.17 mg kg-1 h-1 +/- 1.4 and for midazolam 0.073 mg/kg +/-0.02 and 0.074 mg kg-1 h-1 +/- 0.14. Steady-state plasma concentrations of propofol averaged 1.23 micrograms/kg +/- 0.75 and of midazolam 134 ng/ml +/- 62. Recovery was significantly shorter for propofol: 3.42 +/- 2.5 versus 8.05 min +/6.2 for midazolam. Perioperative cooperation was similar in both groups providing good or excellent conditions in 76% with propofol and in 52% with midazolam. 2h after discontinuation of the infusion 92% of the propofol patients were alert, while 36% of the midazolam were sleeping again. Cardiovascular effects of both drugs were minimal; however significant respiratory depression and/or airway obstruction developed in both groups (propofol 48%, midazolam 52%) requiring therapeutic intervention. Additional undesirable effects were: severe cough (propofol 40%, midazolam 20%), inadvertent movements (propofol 36%, midazolam 24%), confusion (propofol 24%, midazolam 20%), euphoria (propofol 44%), pain on injection (propofol 32%). The results of the study indicate that both drugs are useful and controllable sedative agents for surgery under regional anaesthesia, provided that measures for continuous monitoring of respiration and emergency care are guaranteed.

Anesthesia, Epidural↗
PubMed1988

Interaction of cadmium ions with calcium hydroxyapatite crystals: a possible mechanism contributing to the pathogenesis of cadmium-induced bone diseases.

Cadmium ions adsorb onto calcium hydroxyapatite crystals (HA) and are as effective as inorganic pyrophosphate and aluminum ions in retarding the rate of in vitro dissolution of HA. In contrast, cadmium ions have no important retarding effect on the growth of HA, but are built into the crystals, thus making them very resistant to subsequent dissolution. These effects could interfere with bone remodeling, with cadmium protecting normal sites of resorption and thus causing resorption at pathological sites.

Bone Diseases, Metabolic↗
PubMed1988

Effects of propofol on cardiovascular dynamics and coronary blood flow in geriatric patients. A comparison with etomidate.

The cardiovascular and myocardial effects of propofol and etomidate were studied in 20 geriatric patients (age 65-84 years) who underwent major upper abdominal surgery. Ten patients received propofol 1.5 mg/kg for induction of anaesthesia followed by a continuous infusion of 0.1 mg/kg/minute for maintenance; 10 patients received etomidate 18 mg for induction followed by 2.4 mg/minute for maintenance. Vecuronium was used for neuromuscular blockade. Cardiovascular dynamics were recorded in the awake state one minute after induction and 1, 5 and 30 minutes after tracheal intubation; coronary blood flow (argon wash-in) and myocardial oxygen consumption were determined in the awake state and 5 and 30 minutes after intubation. Both anaesthetics decreased systolic, diastolic and mean arterial pressures, heart rate and cardiac index to the same extent. Myocardial blood flow and oxygen consumption were also reduced in both groups due to a reduction in cardiac work. Tracheal intubation produced a marked increase in arterial pressure in the etomidate group, while haemodynamic changes were absent in the propofol group, Myocardial lactate production was not observed in either group 5 or 30 minutes after tracheal intubation.

Aged↗
PubMed1988

[Myocardial metabolism as affected by propofol in geriatric patients. A comparison with etomidate].

This study was designed to compare the effects of propofol and etomidate on myocardial metabolism in elderly patients without clinical manifestations of heart failure or coronary artery disease. Twenty geriatric patients (age 65-82 years) scheduled to undergo elective major upper-abdominal surgery were studied and randomly allocated to two equal groups (propofol and etomidate). All patients were premedicated with piritramide, 7.5 mg, and promethazine, 25 mg, intramuscularly 1 h before arrival in the anesthesia room. Ten patients received propofol (1.5 mg/kg) for induction of anesthesia, followed by 10-min infusion of an induction dose; thereafter, anesthesia was maintained with a continuous infusion of 0.1 mg/kg per min. Ten patients received etomidate, 18 mg, for induction, followed by 2.4 mg/min for maintenance. Vecuronium was used for neuromuscular blockade. Cardiovascular dynamics were recorded while the patients were awake, 1-2 min after induction during apnoea, and 1, 5 and 30 min after tracheal intubation without surgical stimulation. Coronary blood flow (argon wash-in technique with sampling of blood from the coronary sinus), myocardial oxygen consumption and myocardial uptake of glucose, free fatty acids and lactate were determined in the awake state and 5 and 30 min after intubation. Arterial plasma concentrations of propofol (high-pressure liquid chromatography with fluorescence detection) and etomidate (gas chromatography) were measured every 5 min throughout the investigation period, which lasted 45 min. Overall mean plasma concentrations of propofol were 3.69 +/- 0.16 micrograms/ml and of etomidate 1.1 +/- 0.16 microgram/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

[Effect of preoperative continuous nifedipine maintenance medication on hemodynamics and myocardial lactate extraction in coronary surgery patients].

The cardioprotective efficacy of preoperatively maintained long-term oral nifedipine application to 21 patients undergoing coronary artery bypass grafting (CABG) was investigated during fentanyl-N2O-anaesthesia. Two groups were defined at random; one group of patients receiving their normal morning doses together with the premedication, the other, who received the last nifedipine medication in the evening before surgery. Measurements where performed: 1. before induction of anaesthesia (reference value), 2. after induction, 3. at skin incision, 4. during sternotomy. There were no significant differences of hemodynamic parameters between the two groups. The hemodynamic parameters heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), and coronary perfusion pressure (CPP) decreased after induction in accordance with the plasma-concentrations of epinephrine and norepinephrine in both groups and increased again during sternotomy with HR and CI remaining below and MAP and CPP rising above the reference value. The nifedipine-plasma-concentrations were significantly higher in the group with the morning dose and just within the minimal therapeutic range before and after induction of anaesthesia. But during skin incision and sternotomy the plasma levels fell below 10 ng/ml, i.e. below the therapeutic level. The incidence of myocardial lactate extraction values greater than 10% was highest immediately after induction of anaesthesia and lowest during sternotomy with one patient in both groups exhibiting negative lactate extraction as a symptom of myocardial ischemia. The results suggest that the preoperatively maintained oral nifedipine medication of 10-20 mg p.o. was not able to provide sufficiently high nifedipine-plasma-levels during sternotomy nor to improve the hemodynamic state in patients with CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗