Montserrat Rigol

Short-Term Effects of Transdermal Estrogen Replacement Therapy on Coronary Vascular Reactivity in Postmenopausal Women With Angina Pectoris and Normal Results on Coronary Angiograms

OBJECTIVES This study sought to analyze the effect of short-term transdermal estradiol treatment on in vivo coronary endothelial function in postmenopausal women with angina and normal results on coronary arteriograms. BACKGROUND The incidence of coronary heart disease increases in women after menopause. Estrogen replacement therapy has been associated with a global reduction in cardiovascular disease incidence and mortality. In addition, coronary endothelial dysfunction has been demonstrated in a group of postmenopausal women. It has been shown that intravenous or intracoronary estrogens improve endothelial function in postmenopausal women with coronary atherosclerosis. However, the efficacy of this treatment is unknown in patients with angina and normal coronary arteries. METHODS Endothelium-dependent coronary reactivity was analyzed in 15 postmenopausal women with angina and normal coronary arteries at baseline and after 24 h of estradiol transdermal administration (100 microg). RESULTS Estradiol concentration increased from 22 +/- 8 pg/ml (mean +/- SEM) at baseline to 76 +/- 13 pg/ml (p < 0.01) at 24 h. At baseline, acetylcholine induced vasoconstriction, with a mean diameter reduction of -23 +/- 6% (p = 0.002). After estrogen treatment, there was no vasoconstriction with acetylcholine, with a mean diameter change of 0 +/- 4%, significantly different from the pretreatment diameter reduction observed (p = 0.003). Similarly, estimated coronary blood flow significantly increased in response to acetylcholine after estrogen treatment, with a mean change of 50 +/- 30% compared with 5 +/- 24% before estradiol administration (p = 0.04). CONCLUSIONS Early after transdermal estrogen administration, endothelium-dependent coronary vasomotion is improved in postmenopausal women with angina and normal coronary arteries.

Efficacy of linezolid compared to vancomycin in an experimental model of pneumonia induced by methicillin-resistant Staphylococcus aureus in ventilated pigs.

Objective:To assess the efficacy of linezolid compared with vancomycin in an experimental model of pneumonia induced by methicillin-resistant Staphylococcus aureus (MRSA) in ventilated pigs. Methods:Forty pigs (30 kg) were intubated and challenged via bronchoscopy with a suspension of 106 colony forming units of MRSA into every lobe. Afterwards, pigs were ventilated up to 96 hours. Twelve hours after bacterial inoculation, the animals were randomized into 4 groups of treatment: group 1, control; group 2, vancomycin twice daily; group 3, continuous infusion of vancomycin; and group 4, linezolid. Clinical and laboratory parameters were monitored throughout the study. Bacterial cultures of bronchoalveolar lavage fluid and lung tissue samples were performed at the end of the study. Measurements of histopathology derangements of lung samples and studies of intrapulmonary drug penetration were performed. Results:A total of 34 animals completed the study. No differences in clinical and laboratory parameters were observed. The percentage of bronchoalveolar lavage fluid and lung tissue samples with positive cultures for MRSA in controls and groups 2, 3, and 4 was respectively 75%, 11%, 11%, and 0% (p < .01); 52%, 9%, 24%, and 2.5% (p < .01). Histopathology studies demonstrated signs of pneumonia in 95%, 69%, 58%, and 57% and signs of severe pneumonia in 48%, 29%, 22%, and 0% of controls and groups 2, 3, and 4, respectively (p < .01). In addition, pharmacokinetics/pharmacodynamics profile in serum and lung tissue showed better results for linezolid compared with both vancomycin treatments. Conclusions:In this animal model of MRSA pneumonia, linezolid showed a better efficacy than vancomycin showed because of a better pharmacokinetics/pharmacodynamics index.

Allogeneic adipose stem cell therapy in acute myocardial infarction.

Stem cell therapy offers a promising approach to reduce the long‐term mortality rate associated with heart failure after acute myocardial infarction (AMI). To date, in vivo translational studies have not yet fully studied the immune response to allogeneic adipose tissue‐derived mesenchymal stem cells (ATMSCs). We analysed the immune response and the histological and functional effects of allogeneic ATMSCs in a porcine model of reperfused AMI and determine the effect of administration timing.

Effects of duty cycle and positive end-expiratory pressure on mucus clearance during mechanical ventilation*.

Objectives:During mechanical ventilation, air flows may play a role in mucus transport via two-phase gas liquid flow. The aim of this study was to evaluate effects of duty cycles and positive end-expiratory pressure on mucus clearance in pigs using mechanical ventilation, and to assess their safety. Design:Prospective randomized animal study. Setting:Animal research facility, University of Barcelona, Spain. Subjects:Eight healthy pigs. Interventions:Pigs were intubated and on volume-control mechanical ventilation for up to 84 hrs. After 4, 24, 48, and 72 hrs of mechanical ventilation, six levels of duty cycle (0.26, 0.33, 0.41, 0.50, 0.60, and 0.75) with no associated positive end-expiratory pressure or 5 cm H2O of positive end-expiratory pressure were randomly applied. Surgical bed was oriented 30 degrees in the reverse Trendelenburg position, as in the semirecumbent position. Measurement and Main Results:Inspiratory and expiratory flows and hemodynamics were measured after each 30-min ventilation period. Mucus movement was assessed through fluoroscopy tracking of radio-opaque markers. Mucus velocity was described by a positive vector (toward the glottis) or negative vector (toward the lungs). No effect of positive end-expiratory pressure was found; however, as duty cycle was increasingly prolonged, a trend toward reduced velocity of mucus moving toward the lungs and increased outward mucus velocity was found (p = .064). Two clusters of mucus velocities were identified as duty cycle was prolonged beyond 0.41. Thus, duty cycle >0.41 increased mean expiratory–inspiratory flow bias from −4.1 ± 4.6 to 7.9 ± 5.9 L/min (p < .0001) and promoted outward mucus velocity from −0.22 ± 1.71 mm/min (range, −5.78 to 2.42) to 0.53 ± 1.06 mm/min (−1.91 to 3.88; p = .0048). Duty cycle of 0.75 resulted in intrinsic positive end-expiratory pressure (2.1 ± 1.1 cm H2O [p < .0001] vs. duty cycle 0.26–0.5), with no hemodynamic compromise. Conclusions:In the semirecumbent position, mucus clearance is improved with prolongation of the duty cycle. However, in clinical practice, positive findings must be balanced against the potentially adverse hemodynamic and respiratory effects.

Linezolid limits burden of methicillin-resistant Staphylococcus aureus in biofilm of tracheal tubes.

Objective: To evaluate the effects of systemic treatment with linezolid compared with vancomycin on biofilm formation in mechanically ventilated pigs with severe methicillin-resistant Staphylococcus aureus–induced pneumonia. Design: Prospective randomized animal study. Setting: Departments of Pneumology, Microbiology, and Pharmacy of the Hospital Clínic, Barcelona, and Scientific and Technological Services of the University of Barcelona. Subjects: We prospectively analyzed 70 endotracheal tube samples. Endotracheal tubes were obtained from pigs either untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). Interventions: The endotracheal tubes were obtained from a previous randomized study in tracheally intubated pigs with methicillin-resistant Staphylococcus aureus severe pneumonia, and mechanically ventilated for 69 ± 16 hrs. Measurements and Main Results: Distal and medial hemisections of the endotracheal tube were assessed to quantify methicillin-resistant Staphylococcus aureus burden, antibiotic biofilm concentration by high-performance liquid chromatography or bioassay, and biofilm thickness through scanning electron microscopy. We found a trend toward a significant variation in biofilm methicillin-resistant Staphylococcus aureus burden (log colony-forming unit/mL) among groups (p = .057), and the lowest bacterial burden was found in endotracheal tubes treated with linezolid (1.98 ± 1.68) in comparison with untreated endotracheal tubes (3.72 ± 2.20, p = .045) or those treated with vancomycin (2.97 ± 2.43, p = .286). Biofilm linezolid concentration was 19-fold above the linezolid minimum inhibitory concentration, whereas biofilm vancomycin concentration (1.60 ± 0.91 µg/mL) was consistently below or close to the vancomycin minimum inhibitory concentration. Biofilm was thicker in the vancomycin group (p = .077). Conclusions: Systemic treatment with linezolid limits endotracheal tube biofilm development and methicillin-resistant Staphylococcus aureus burden. The potential clinical usefulness of linezolid in decreasing the risk of biofilm-related respiratory infections during prolonged tracheal intubation requires further investigation.

Cocaine administration enhances platelet reactivity to subendothelial components: studies in a pig model

Myocardial infarction in cocaine abusers may be related to a direct platelet‐activating effect. We analysed this possibility in an experimental model. Studies were carried out in eight normal, anaesthetized pigs with a weight of 30.7 ± 3.7 kg. Blood samples were withdrawn before and 20 min after i.v. administration of cocaine (10 mg kg−1; at 1 mg kg−1 every 2 min). Modifications in platelet responses to arachidonic acid (AA; 1.4 mmol L−1), ADP (1–4 μM), synthetic thromboxane endoperoxide analogue (U46619; 1 μM), collagen (2.5–5 μg mL−1), adrenaline (10 μM) and ristocetin (0.8–1 mg mL−1) were tested by conventional aggregometry. Changes in the capacity of platelets to form aggregates on damaged subendothelium were assessed by means of an ex vivo perfusion system in which blood was circulated for 10 min at 800 s−1, a shear rate similar to that found in normal coronary arteries. The interaction of platelets with perfused denuded arterial segments was morphometrically quantified and expressed as a percentage of damaged vessel surface covered by platelets (%CS). Cocaine administration did not influence platelet aggregation patterns in pigs. However, there was a significant increase in the interaction of pig platelets with subendothelial structures after cocaine infusion (%CS = 40 ± 17% vs. 27 ± 16% baseline; mean ± SD; P < 0.01). Cocaine administration in this animal model increases the reactivity of platelets exposed to subendothelium. These results support the concept that the administration of cocaine to pigs has a prothrombotic effect by facilitating the interaction of platelets with damaged arteries.

A Novel Porcine Model of Ventilator-associated Pneumonia Caused by Oropharyngeal Challenge with pseudomonas aeruginosa

Background: Animal models of ventilator-associated pneumonia (VAP) in primates, sheep, and pigs differ in the underlying pulmonary injury, etiology, bacterial inoculation methods, and time to onset. The most common ovine and porcine models do not reproduce the primary pathogenic mechanism of the disease, through the aspiration of oropharyngeal pathogens, or the most prevalent human etiology. Herein the authors characterize a novel porcine model of VAP due to aspiration of oropharyngeal secretions colonized by Pseudomonas aeruginosa. Methods: Ten healthy pigs were intubated, positioned in anti-Trendelenburg, and mechanically ventilated for 72 h. Three animals did not receive bacterial challenge, whereas in seven animals, a P. aeruginosa suspension was instilled into the oropharynx. Tracheal aspirates were cultured and respiratory mechanics were recorded. On autopsy, lobar samples were obtained to corroborate VAP through microbiological and histological studies. Results: In animals not challenged, diverse bacterial colonization of the airways was found and monolobar VAP rarely developed. In animals with P. aeruginosa challenge, colonization of tracheal secretion increased up to 6.39 ± 0.34 log colony-forming unit (cfu)/ml (P < 0.001). VAP was confirmed in six of seven pigs, in 78% of the cases developed in the dependent lung segments (right medium and lower lobes, P = 0.032). The static respiratory system elastance worsened to 41.5 ± 5.8 cm H2O/l (P = 0.001). Conclusions: The authors devised a VAP model caused by aspiration of oropharyngeal P. aeruginosa, a frequent causative pathogen of human VAP. The model also overcomes the practical and legislative limitations associated with the use of primates. The authors’ model could be employed to study pathophysiologic mechanisms, as well as novel diagnostic/preventive strategies.

Effects of manual rib cage compressions on expiratory flow and mucus clearance during mechanical ventilation.

Objectives:We investigated the effects of two different types of manual rib cage compression on expiratory flow and mucus clearance during prolonged mechanical ventilation in pigs. Design:Prospective randomized animal study. Setting:Animal research facility, University of Barcelona, Spain. Subjects:Nine healthy pigs. Measurement and Main Results:Pigs were tracheally intubated, sedated, paralyzed, and mechanically ventilated. The animals were prone on a surgical bed in the anti-Trendelenburg position. The experiments were carried out at approximately 60 and 80 hrs from the beginning of mechanical ventilation. Two types of manual rib cage compressions were tested: Hard and brief rib cage compressions synchronized with early expiratory phase (hard manual rib cage compression) and soft and gradual rib cage compressions applied during the late expiratory phase (soft manual rib cage compression). The interventions were randomly applied for 15min with a 15-min interval between treatments. Respiratory flow and mucus movement were assessed during the interventions. Respiratory mechanics and hemodynamics were assessed prior to and after the interventions. Peak expiratory flow increased to 60.1±7.1L/min in comparison to 51.2±4.6L/min without treatment (p < 0.0015) and 48.7±4.3L/min with soft manual rib cage compression (p = 0.0002). Similarly, mean expiratory flow increased to 28.4±5.2L/min during hard manual rib cage compression vs. 15.9±2.2 and 16.6±2.8L/min without treatment and soft manual rib cage compression, respectively (p = 0.0006). During hard manual rib cage compression, mucus moved toward the glottis (1.01 ± 2.37mm/min); conversely, mucus moved toward the lungs during no treatment and soft manual rib cage compression, –0.28 ± 0.61 and –0.15±0.95mm/min, respectively (p = 0.0283). Soft manual rib cage compression slightly worsened static lung elastance and cardiac output (p = 0.0391). Conclusions:Hard manual rib cage compression improved mucus clearance in animals positioned in the anti-Trendelenburg position. The technique appeared to be safe. Conversely, soft manual rib cage compression was not effective and potentially unsafe. These findings corroborate the predominant role of peak expiratory flow on mucus clearance.

Nitric oxide synthase II mRNA expression in cardiac tissue of patients with heart failure undergoing cardiac transplantation

OBJECTIVES To examine whether inducible nitric oxide synthase is expressed in myocardial tissue of patients with heart failure. BACKGROUND There is increasing evidence that alterations in nitric oxide synthesis are of pathophysiologic importance in heart failure. Nitric oxide (NO) can exert negative inotropic and cytotoxic effects on cardiomyocytes. A number of studies have shown altered nitric oxide production by the endothelial constitutive isoform of nitric oxide synthase (NOS III), but there is little information on the role of NOS II. Expression of NOS II could lead to excessive production of NO in the myocardium and affect cardiac contractility. METHODS NOS II mRNA expression in myocardial tissue of 18 patients with idiopathic dilated cardiomyopathy (DCM), 7 patients with ischemic cardiopathy and severe ventricular dysfunction (ISCH), 4 patients with acute myocardial infarction (AMI) and 11 controls. Serum concentration of NO2-/NO3- (NOx) was also measured. RESULTS NOS II gene expression occurred in all the patients with DCM, in 1 out of the 7 ISCH patients, in 2 out of the 4 patients with AMI and in none of the controls. Moreover, DCM patients showed a significant 6-fold increase in NOx concentration (253+/-47 nm/ml) as compared to controls (40+/-2 nm/ml) P < 0.001, a phenomenon not observed in ISCH patients (56+/-3 nm/ml). CONCLUSIONS NOS II expression occurs in failing human cardiac myocytes and can play an specific role in the pathogenesis of DCM.

Gravity predominates over ventilatory pattern in the prevention of ventilator-associated pneumonia.

Objective:In the semirecumbent position, gravity-dependent dissemination of pathogens has been implicated in the pathogenesis of ventilator-associated pneumonia. We compared the preventive effects of a ventilatory strategy, aimed at decreasing pulmonary aspiration and enhancing mucus clearance versus the Trendelenburg position. Design:Prospective randomized animal study. Setting:Animal research facility, University of Barcelona, Spain. Subjects:Twenty-four Large White–Landrace pigs. Interventions:Pigs were intubated and on mechanical ventilation for 72 hours. Following surgical preparation, pigs were randomized to be positioned: 1) in semirecumbent/prone position, ventilated with a duty cycle (TITTOT) of 0.33 and without positive end-expiratory pressure (control); 2) as in the control group, positive end-expiratory pressure of 5 cm H2O and TITTOT to achieve a mean expiratory-inspiratory flow bias of 10 L/min (treatment); 3) in Trendelenburg/prone position and ventilated as in the control group (Trendelenburg). Following randomization, Pseudomonas aeruginosa was instilled into the oropharynx. Measurements and Main Results:Mucus clearance rate was measured through fluoroscopic tracking of tracheal markers. Microspheres were instilled into the subglottic trachea to assess pulmonary aspiration. Ventilator-associated pneumonia was confirmed by histological/microbiological studies. The mean expiratory-inspiratory flow in the treatment, control, and Trendelenburg groups were 10.7 ± 1.7, 1.8 ± 3.7 and 4.3 ± 2.8 L/min, respectively (p < 0.001). Mucus clearance rate was 11.3 ± 9.9 mm/min in the Trendelenburg group versus 0.1 ± 1.0 in the control and 0.2 ± 1.0 in the treatment groups (p = 0.002). In the control group, we recovered 1.35% ± 1.24% of the instilled microspheres per gram of tracheal secretions, whereas 0.22% ± 0.25% and 0.97% ± 1.44% were recovered in the treatment and Trendelenburg groups, respectively (p = 0.031). Ventilator-associated pneumonia developed in 66.67%, 85.71%, and 0% of the animals in the control, treatment, and Trendelenburg groups (p < 0.001). Conclusions:The Trendelenburg position predominates over expiratory flow bias and positive end-expiratory pressure in the prevention of gravity-dependent translocation of oropharyngeal pathogens and development of ventilator-associated pneumonia. These findings further substantiate the primary role of gravity in the pathogenesis of ventilator-associated pneumonia.