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Biomedical subjects

H Thomas

Publications and source records attributed to H Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1998

The effect of dopexamine on ventilation perfusion distribution and pulmonary gas exchange in anesthetized, paralyzed patients.

UNLABELLED: We studied the effects of the beta2-adrenoceptor and DA1-receptor agonist dopexamine on ventilation perfusion (V(A)/Q) distribution in anesthetized, paralyzed patients (n = 17) undergoing major abdominal surgery. Intrapulmonary shunt (Q(S)/Q(T)) (percentage of cardiac output [CO]), perfusion of low V(A)/Q areas (percentage of CO), ventilation of high V(A)/Q areas (percentage of total ventilation [V(E)]), and dead space ventilation [percentage of V(E)]) were calculated from the retention/excretion data of six inert gases. In the control state, Q(S)/Q(T) was 11% +/- 9% (mean +/- SD) and little perfusion of low V(A)/Q areas (3% +/- 4%) was observed. Infusion of 1.0 microg kg(-1) x min(-1) dopexamine had no effect on Q(S)/Q(T) and low V(A)/Q areas despite an increased CO (7.7 +/- 2.2 L/min versus 6.2 +/- 1.2 L/min; P < 0.01). Pao2 increased from 15.5 +/- 5.6 kPa (116 +/- 42 mm Hg) to 17.3 +/- 6.3 kPa (130 +/- 47 mm Hg) (P < 0.05). Infusion of 2.0 microg x kg(-1) x min(-1) dopexamine further increased CO to 8.4 +/- 2.7 L/min (P < 0.01) without alterations of Q(S)/Q(T), perfusion of low V(A)/Q areas, and Pao2. We concluded that dopexamine (1.0 microg x kg(-1) x min(-1) and 2.0 microg x kg(-1) x min(-1)) has no adverse effects on V(A)/Q relationships and Q(S)/Q(T) in anesthetized, paralyzed patients. IMPLICATIONS: The I.V. administration of vasoactive drugs can improve oxygen delivery to different organ systems but may impair pulmonary gas exchange. In anesthetized, paralyzed patients, we studied the effects of beta2-adrenoceptor and DA1-receptor agonist dopexamine on ventilation perfusion distribution. Dopexamine (1.0 microg x kg(-1) x min(-1) and 2.0 microg x kg(-1) min(-1)) improved cardiac output and oxygenation without alterations of intrapulmonary shunt.

Adrenergic beta-Agonists↗
PubMed1998

The pharmacokinetics of acetyl starch as a plasma volume expander in patients undergoing elective surgery.

UNLABELLED: Acetyl starch (ACS) is a new synthetic colloid solution for plasma volume expansion and is now undergoing phase 2 clinical trials. We compared the pharmacokinetics of ACS with those of hydroxyethyl starch (HES) in 32 patients (ASA physical status I and II) undergoing elective surgery. In this randomized, double-blind trial, patients received either 15 mL/kg ACS 6% (average molecular weight [Mw] 200,000/molar substitution [MS] 0.5) or HES 6% (Mw 200,000/MS 0.5) i.v. up to a maximal dose of 1000 mL. Plasma colloid concentrations were measured by repetitive arterial blood sampling over 24.5 h. Plasma colloid concentrations were detected using a high-pressure liquid chromatography controlled enzymatic test. Standard pharmacokinetics were calculated, including initial half-life (t(1/2init)), i.e., the time required for a 50% decline of the maximal plasma colloid concentration at the end of drug infusion. Whereas HES was eliminated by second-order kinetics, ACS followed first-order characteristics. In the first hours after i.v. administration, t(1/2init) and clearances were similar in both groups. However, the terminal half-life of HES was significantly longer than that of ACS (9.29 +/- 1.43 h vs 4.37 +/- 1.06 h). After 16.5 and 24.5 h, ACS showed significantly lower plasma concentrations than HES, which indicates that the final degradation of ACS by esterases and amylase was significantly more rapid. ACS might be an alternative plasma volume expander, which avoids the accumulation of persisting macromolecules. IMPLICATIONS: We studied the pharmacokinetics of acetyl starch, a newly developed colloid solution for plasma volume substitution, compared with hydroxyethyl starch in 32 surgical patients undergoing elective major general surgical procedures. In contrast to hydroxyethyl starch, this new agent undergoes rapid and nearly complete enzymatic degradation.

Adolescent↗
PubMed1998

Intrathoracic and pulmonary blood volume during CO2-pneumoperitoneum in humans.

BACKGROUND: Induction of CO2-pneumoperitoneum may have significant effects on systemic and pulmonary haemodynamics. We hypothesized that intrathoracic (ITBV) and pulmonary blood volume (PBV) are affected during intra-abdominal CO2-insufflation, which may be pronounced by positional changes of the patient. METHODS: Sixteen anaesthetized patients were studied before, during and after CO2-pneumoperitoneum for laparoscopic cholecystectomy. A dye indicator technique was used to assess ITBV and PBV. In addition, gas exchange and haemodynamics were recorded. RESULTS: In the supine position, induction of CO2-pneumoperitoneum had no effects on ITBV, PBV and cardiac output. Mean systemic arterial pressure increased from 10.9 +/- 1.5 kPa (82 +/- 11 mmHg) to 12.7 +/- 1.5 kPa (95 +/- 11 mmHg, P < 0.01). In the reverse Trendelenburg position ITBV decreased from 19.8 +/- 5.1 ml.kg-1 to 16.7 +/- 3.7 ml.kg-1 (P < 0.05) during CO2-insufflation, but increased to control values after 20 min. PBV decreased from 4.2 +/- 1.2 ml.kg-1 to 3.4 +/- 1.1 ml.kg (P < 0.05) and remained decreased during CO2-pneumoperitoneum. Calculated venous admixture was unchanged throughout the study. Deflation of CO2-pneumoperitoneum increased ITBV (22.4 +/- 5.2 ml.kg-1, P < 0.05) and cardiac output above control values. CONCLUSIONS: In anaesthetized-paralyzed patients in the reverse Trendelenburg position intra-abdominal CO2-insufflation is associated with significant alterations of ITBV and PBV. The release of CO2-pneumoperitoneum is associated with a re-distribution of blood into the thorax.

Abdomen↗
PubMed1998

[Diagnosis of pneumonia in long-term ventilated patients. Value of digital luminescence radiography in comparison with clinical and microbiological monitoring].

PURPOSE: Pulmonary infection is one of the most feared complications in patients receiving long-term ventilation. We evaluated prospectively the diagnostic value of daily bedside chest radiography performed as digital luminescence radiography (DLR) in comparison to clinical findings and quantitative microbial culture. MATERIAL AND METHODS: Prospective evaluation of daily bedside chest radiography (DLR) and clinical parameters such as blood count, body temperature, and microbiological monitoring (quantitative culturing, microscopy) of 20 patients receiving long-term ventilation was undertaken. Altogether 325 chest radiographs were evaluated. RESULTS: 96% of the routine radiographs showed abnormal findings. Nosocomial pneumonia was suspected in 31% of all 330 days of observation by means of clinical and microbiological findings. DLR showed correct findings in 80% of this days (right-positive interpretation); a false-positive interpretation was resulted in 16 radiographs. Most common finding in nosocomial pneumonia was an alveolar pattern with air bronchogram. Fever and leucocytosis often precede radiological evidence of pneumonia. CONCLUSION: Daily bedside chest radiography performed as DLR shows abnormal finding in a high percentage. Bedside chest radiograph is in accordance to clinical and microbiological finding of nosocomial pneumonia in 80%.

Adult↗
PubMed1997

O-methylation of (+)-(R)- and (-)-(S)-6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline (salsolinol) in the presence of pig brain catechol-O-methyltransferase.

(+)-(R)- and (-)-(S)-salsolinol, dopamine-derived tetrahydroisoquinolines, were tested as substrates of pig brain soluble and membrane-bound catechol-O-methyltransferase (COMT) and as inhibitors of O-methylation of dopamine by soluble COMT in vitro. Methylation products were separated by high-performance liquid chromatography with electrochemical detection. Quantification of the products showed that O-methylation of (+)-(R)-salsolinol by soluble COMT afforded the 7-O-methylated product salsoline preferentially, whereas (-)-(s)-salsolinol yielded almost equivalent amounts of the 6- and 7-methyl ethers. Unlike O-methylation by soluble COMT, 7-O/6-O-methylation ratio produced by membrane-bound COMT varied with (+)-(R)-salsolinol concentration. As to the O-methylation of dopamine by soluble COMT, comparable competitive inhibition was observed with both (+)-(R)- and (-)-(S)-salsolinol.

Animals↗
PubMed1997

[Simultaneous long-term measurement of duodenogastric reflux and gastroduodenal motility].

We combined a newly developed ambulatory fiberoptic system for detecting intragastric bilirubin (Bilitec 2000, Synectics Medical Inc., Sweden) with prolonged measurement of gastroduodenal motility in 10 healthy volunteers and 10 patients followed BI resection. Circadian intragastric bilirubin exposure and the total number of tremendous changes of bilirubin absorption (more than 20%, over a period of at least 5 min) were significantly increased in the BI-resected patients (P < 0.05). In patients the interdigestive motility cycle (IMC) was characterized by the appearance of several types of abnormally propagated phase III activity fronts. Of the tremendous increases of bilirubin absorption in the patient group, 90.1% were associated with abnormally propagated phase III activity fronts. In cases of increased duodenogastric reflux, the combination of ambulatory intragastric bilirubin measurement and long-term manometry seems to be feasible to assess motility and reflux simultaneously.

Adult↗
PubMed1997

The correction of autonomic dysfunction in cirrhosis by captopril.

BACKGROUND/AIMS: Vagal dysfunction is reported in about 70% of patients with cirrhosis, irrespective of aetiology, as detected by cardiovascular reflex tests. We have previously shown that RR-variability on 24-h ECG is a more sensitive marker of vagal dysfunction in cirrhosis. Angiotensin II inhibits vagal function in animals, and it is elevated in cirrhosis and may be the cause of the vagal dysfunction. Our aim was to observe the effect of captopril on vagal dysfunction in cirrhosis. METHODS: Eight patients with cirrhosis (biopsy proven, male two, female six, mean age 54.25) had 24-h ECG RR-variability performed. They then received captopril 25 mg t.d.s. for 48 h. The 24-h ECG was repeated on therapy. RESULTS: Mean blood pressure remained unchanged: baseline 89.8 +/- 4.8 mmHg (mean +/- sem) versus 91.8 +/- 5.9 mmHg, p = not significant. Median baseline RR-variability was 791 (range 18-5344) counts/24 h and increased in all but one patient, with captopril, to 1548 (56-4824) p = 0.008. Three increased into the normal range. CONCLUSION: The vagal dysfunction of cirrhosis is caused by neuromodulation by angiotensin II and is not due to a neuropathy.

Adult↗
PubMed1997

Effectiveness of interferon alfa on incidence of hepatocellular carcinoma and decompensation in cirrhosis type C. European Concerted Action on Viral Hepatitis (EUROHEP).

BACKGROUND/AIMS: The role of interferon alfa treatment in improving morbidity endpoints in patients with chronic hepatitis C infection is currently under debate. The aim of this study was to evaluate the effectiveness of interferon in preventing hepatocellular carcinoma and decompensation in cirrhosis type C. METHODS: A retrospective cohort study was carried out on 329 consecutive Caucasian patients with cirrhosis followed for a mean period of 5 years at seven tertiary care university hospitals. Inclusion criteria were biopsy-proven cirrhosis, anti-HCV positivity, abnormal serum aminotransferase levels and absence of complications of cirrhosis. RESULTS: The yearly incidence of hepatocellular carcinoma was 2.3% for 136 untreated patients and 1.0% for 193 patients treated with interferon alfa. The yearly incidence of hepatic decompensation was 5.7 for untreated and 1.5 for the treated patients. Fourteen (7%) of 193 treated patients showed sustained aminotransferase normalization and none of them developed complications of cirrhosis. At enrollment, untreated patients were older and had more severe liver disease than patients treated with interferon. After adjustment for clinical and serologic differences at entry between treated and untreated patients, the 5-year estimated probability of the occurrence of hepatocellular carcinoma was 2.1% and 2.7% and of decompensation was 7% and 11% for treated and untreated cases, respectively. CONCLUSIONS: This analysis did not detect any significant benefit of interferon alfa on morbidity in patients with compensated cirrhosis type C, although it suggests a reduction in complications of cirrhosis for those with a sustained response to therapy, and it indicates the need for better therapies.

Antiviral Agents↗
PubMed1997

Role of quantitative cultures and microscopic examinations of endotracheal aspirates in the diagnosis of pulmonary infections in ventilated patients.

Endotracheal aspirates (EA) from 20 intubated patients in a surgical intensive care unit (mean ventilation time/patient = 16.5 days) were investigated serially by performing quantitative cultures using growth of 10(5) cfu/mL as a cut-off point. Microscopic examinations were made using Giemsa's stain for polymorphonuclear neutrophils (PMN). The spectrum of pathogens encountered was determined and compared with clinical data to distinguish colonization from infection of the lower respiratory tract. Out of 301 EA cultures, 156 (51.8%) were positive and 145 (48.2%) were below the cut-off point. Counts of PMN were significantly higher in samples which gave positive cultures. Seventy-five different bacterial strains were isolated (64% were Gram-negative bacilli). Seventeen patients (85%) were colonized with Gram-negative bacteria. Nine patients (45%) developed nosocomial pneumonia (NP), five (25%) had no signs of pneumonia, and six (30%) had an uncertain status. Main causative agents for NP were Pseudomonas aeruginosa, Enterobacteriaceae and Staphylococcus aureus. Quantitative EA cultures had a sensitivity of 81.5%, a specificity of 64.8%, a positive predictive value of 55% and a negative predictive value of 87%. Our results suggest that EA quantitative cultures (cut-off value 10(5) cfu/mL), species identification and microscopic examination of EA may help to differentiate tracheobronchial colonization and infection, especially when bronchoscopic techniques are not available.

Adult↗
PubMed1997

Sequencing, expression pattern and RFLP mapping of a senescence-enhanced cDNA from Zea mays with high homology to oryzain gamma and aleurain.

Sequence analysis of a 1.4 kb clone from a cDNA library of senescing Zea mays leaves reveals an open reading frame for a 360 amino acid protein. Both the DNA and deduced amino acid sequences are highly homologous to the cysteine proteinases oryzain gamma and aleurain. Northern analysis demonstrates that the corresponding RNA level increases during natural leaf senescence, seedling germination and in chilling of tolerant maize lines, but decreases in a sensitive line. The mRNA level also decreases in regreening leaves, in dark-induced senescence and in nutrient or water stress. Southern and RFLP analysis provide evidence that the gene has two copies, on chromosomes 2 and 7.

Amino Acid Sequence↗
PubMed1997

Cancer-related thromboembolic disease in patients with solid tumours: a retrospective analysis.

BACKGROUND: Cancer patients frequently suffer thromboembolic events. This study assessed the incidence and resource implications of cancer-related thromboembolic disease (CTD) in a single, large cancer centre. PATIENTS AND METHODS: A retrospective analysis of patients admitted with CTD and/or the complications of treatment of CTD over a two-year period has been conducted. Forty-eight patients (23 male, 25 female, median age 60 years) with a variety of solid tumours were identified. RESULTS: The initial presentations were venous thromboses (28 patients) and pulmonary embolism (20 patients). The median interval from cancer diagnosis to the initial episode of CTD was eight (range 0-112) months. Twenty-two patients suffered additional thromboses, despite maintenance warfarin anticoagulation in 18 patients. Six patients experienced anticoagulation-induced haemorrhage. Forty-one (85.4%) patients have died. The median survival from the first thromboembolic event was 8.5 months. The median inpatient stay for management of the first event was 10 (range 4-75) days, accounting for 729 inpatient days during the study period. Recurrent episodes of CTD or complications of anticoagulation resulted in 28 readmissions, accounting for 295 inpatient days. During the two-year period 1024 inpatient days were directly caused by CTD and its complications, representing 6.1% bed occupancy on our unit. CONCLUSION: This study demonstrates that CTD represents a significant cause of morbidity in cancer patients with considerable resource implications for cancer centres. Improvements in prevention and management of CTD would reduce morbidity and lead to considerable cost savings.

Adult↗
PubMed1997

Competency criteria and the class inclusion task: modeling judgments and justifications.

Preschool age children's class inclusion task responses were modeled as mixtures of different probability distributions. The main idea: Different response strategies are equivalent to different probability distributions. A child displays cognitive strategy s if P (child uses strategy s, given the child's observed score X = x) = p(s) is the most probable strategy. The general approach is widely applicable to many settings. Both judgment and justification questions were asked. Judgment response strategies identified were subclass comparison, guessing, and inclusion logic. Children's justifications lagged their judgments in development. Although justification responses may be useful, C. J. Brainerd was largely correct: If a single response variable is to be selected, a judgments variable is likely the preferable one. But the process must be modeled to identify cognitive strategies, as B. Hodkin has demonstrated.

Child↗
PubMed1997

Morbidity and mortality in compensated cirrhosis type C: a retrospective follow-up study of 384 patients.

BACKGROUND & AIMS: Few data are available concerning the long-term prognosis of chronic liver disease associated with hepatitis C virus infection. This study examined the morbidity and survival of patients with compensated cirrhosis type C. METHODS: A cohort of 384 European cirrhotic patients was enrolled at seven tertiary referral hospitals and followed up for a mean period of 5 years. Inclusion criteria were biopsy-proven cirrhosis, abnormal serum aminotransferase levels, absence of complications of cirrhosis, and exclusion of hepatitis A and B viruses and of metabolic, toxic, or autoimmune liver diseases. RESULTS: Antibodies against hepatitis C virus were positive in 98% of 361 patients tested. The 5-year risk of hepatocellular carcinoma was 7% and that of decompensation was 18%. Death occurred in 51 patients (13%), with 70% dying of liver disease. Survival probability was 91% and 79% at 5 and 10 years, respectively. Two hundred five patients (53%) were treated with interferon alfa. After adjustment for clinical and serological differences at baseline between patients treated or not treated with interferon, the 5-year estimated survival probability was 96% and 95% for treated and untreated patients, respectively. CONCLUSIONS: In this cohort of patients, life expectancy is relatively long, in agreement with the morbidity data showing a slowly progressive disease.

Carcinoma, Hepatocellular↗
PubMed1997

Effect of thoracic epidural anaesthesia on ventilation-perfusion distribution and intrathoracic blood volume before and after induction of general anaesthesia.

BACKGROUND: Gas exchange is impaired during general anaesthesia due to development of shunt and ventilation-perfusion mismatching. Thoracic epidural anaesthesia (TEA) may affect the mechanics of the respiratory system, intrathoracic blood volume and possibly ventilation-perfusion (VA/Q) distribution during general anaesthesia. METHODS: VA/Q relationships were analyzed in 24 patients undergoing major abdominal surgery. Intrapulmonary shunt (Qs/QT), perfusion of "low" VA/Q areas, ventilation of "high" VA/Q regions, dead space ventilation and mean distribution of ventilation and perfusion were calculated from the retention/excretion data of six inert gases. Intrathoracic blood volume (ITBV) and pulmonary blood volume (PBV) were determined with a double indicator technique. Recordings were made before and after administration of 8.5 +/- 1.5 ml bupivacaine 0.5% (n = 12) or 8.3 +/- 1.8 ml placebo (n = 12) into a thoracic epidural catheter and after induction of general anaesthesia. RESULTS: Before TEA, Qs/QT was normal in the bupivacaine group (2 +/- 2%) and the placebo group (2 +/- 3%). TEA covering the dermatomal segments T 12 to T 4 had no effect on VA/Q relationships, ITBV and PBV. After induction of general anaesthesia Qs/QT increased to 8 +/- 4% (bupivacaine group, P < 0.05 and to 7 +/- 2% (placebo group, P < 0.05). ITBV and PBV decreased significantly to the same extent in the bupivacaine group and the placebo group. CONCLUSIONS: TEA has no effect on VA/Q distribution, gas exchange and intrathoracic blood volume in the awake state and does not influence development of Qs/QT and VA/Q inequality after induction of general anaesthesia.

Anesthesia, Epidural↗