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Biomedical subjects

R Trawöger

Publications and source records attributed to R Trawöger.

At least 19 recordsLinked to original sources
PubMed2001

A standardized method of oleic acid infusion in experimental acute respiratory failure.

UNLABELLED: Commonly, acute respiratory failure (ARF) in laboratory animals is induced through the intravenous infusion of oleic acid (OA). The methods by which OA is infused, and the methods by which droplets are generated, differ greatly among investigators. The resulting ARF, and the distribution of the underlying pulmonary pathology, are not highly reproducible. A method was developed that generated a reproducible, known spectrum of OA microdroplets. This method was applied to infuse a known volume of OA into the vena cava superior (VCS) in sheep, to induce ARF. In vitro studies were conducted in an observation chamber filled with saline or plasma. The distal end was cut off a 7F Swan Ganz catheter. The catheter was immersed in an observation chamber. Through one of the channels OA was infused at a low flow rate while saline was infused at variable high flow rates through a second channel. The size and the distribution spectrum of the so generated OA droplets were determined from flash photographic studies. The distribution and the size of the microdroplets depended on the media in the observation chamber, and on the saline infusion rate. In vivo studies were conducted in six anesthetized and ventilated sheep. We chose in our in vivo studies a saline flow rate of 126 mL/min and at an OA flow rate of 3 mL/min, that generated OA microdroplets 125 +/- 32 microm SD in size. OA microdroplets were generated in situ in the VCS and where then embolized into small pulmonary vessels. A total dose of 0.06 mL/kg of OA was administered in three separate doses of 0.02 mL/kg, each 10 min apart. The evolving ARF was manifested by a progressive deterioration in arterial blood gases, and a uniform opacification of all lung fields on chest X-ray films. At autopsy the lungs were diffusely consolidated. CONCLUSION: A method was developed to standardize the infusion of OA in laboratory animals that resulted in diffuse involvement of the all lungs, with a predictable and reproducible severe acute respiratory failure.

Acute Disease↗
PubMed2000

[Thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in 13 children: a case series].

Since thromboembolic events (TE) are rare among children there is only limited information on the optimal choice of antithrombotic agents, dose and duration of antithrombotic therapy. Recombinant tissue plasminogen activator (rt-PA) is increasingly used for thrombolytic therapy of organ- and limb threatening thrombosis in children. We investigated retrospectively the efficacy and safety of rt-PA in 13 children treated consecutively between 1996-1999, following the same protocol. The median age was 3.9 years (3 days to 16 years). All children suffered from underlying diseases. In addition, 7 children had cardiac catheters and central venous catheters and two children suffered from Factor V Leiden mutation. Seven children presented with a TE in the arterial system, 6 with one in the venous system. All children were treated with continuous infusion of rt-PA (median dose 0.05; 0.0125-0.2 mg/kg/h) together with low-dose standard heparin (median dose 8; 5-15 IU/kg/h). Thrombolysis was performed for a median time period of 102 hours (6 hours to 16 days). Treatment effects on the thrombus were regularly confirmed by ultrasound. Plasma levels of fibrinogen and haemoglobin decreased moderately during treatment. No cumulative effect or increased dose requirement of rt-PA was detected during extended treatment. Patency of obstructed vessels was achieved in all children. One child developed severe gastrointestinal bleeding. Six children (46%) developed minor bleeding at the site of catheter puncture. One child developed rethrombosis at the site of the previous thrombus 2 weeks after completion of rt-PA treatment. Under rigorous laboratory and ultrasound control, our protocol using low dose rt-PA over a prolonged period of time was effective and safe.

Adolescent↗
PubMed2000

Dependence on a respiratory ventilator due to an atrial septal defect.

An atrial septal defect is commonly thought of as a benign cardiac lesion especially in infancy. The haemodynamic consequences for the lungs, nonetheless, can be comparable to that produced by patency of the arterial duct. In a preterm boy, this lesion led to the development of broncho-pulmonary dysplasia, and dependence on a respiratory ventilator. He could be extubated shortly after surgical closure of the septal defect.

Bronchopulmonary Dysplasia↗
PubMed2000

High-frequency oscillatory ventilation does not decrease endothelin release in lung-lavaged rabbits.

UNLABELLED: High-frequency oscillatory ventilation (HFO) has been shown to reduce lung injury and pulmonary arterial pressure (PAP). We hypothesized that HFO leads to decreased endothelin 1 (ET-1) and endothelin 3 (ET-3) release when compared to conventional mechanical ventilation (CMV) in lung-lavaged rabbits. DESIGN: Prospective, randomized, controlled animal study. In 26 adult New Zealand White Rabbits ventilated by CMV or HFO under hypoxemic and normoxemic conditions after lung lavage (CMV-hypo: n = 5; CMV-normo: n = 8; HFO-hypo: n = 7; HFO-normo: n = 6) we recorded systemic and PAP, measured blood gases, ET-1 and ET-3 and calculated intrapulmonary venous admixture during a 4-h experiment. ET-1 was significantly increased after lavage (p < 0.05) with no further increase until the end of the experiment. Neither pulmonary arterial nor systemic arterial ET-1 differed between CMV and HFO or between hypoxemia and normoxemia. Systemic arterial ET-3, however, was significantly higher in HFO-hypo than in the other two groups ventilated under normoxemic conditions at the end of the experiment (HFO-hypo vs. CMV-normo, p < 0.05; HFO-hypo vs. HFO-normo, p < 0.05). PAP showed a continuous increase in all groups (p < 0.05). We did not find any correlation between PAP and ET-1 or ET-3. Intrapulmonary venous admixture increased in animals ventilated under hypoxemic conditions, whereas it decreased after lung lavage in those ventilated under normoxemic conditions until the end of the experiment (HFO-normo, p < 0.05). CONCLUSIONS: This study suggests that HFO does not decrease ET-1 and ET-3 release compared to CMV in lung-lavaged rabbits. Hypoxemia, however, may increase ET-3 release from the lungs, leading to an increased intrapulmonary shunt.

Animals↗
PubMed1999

Intraosseous lines in preterm and full term neonates.

AIM: To evaluate the use of intraosseous lines for rapid vascular access in primary resuscitation of preterm and full term neonates. METHODS: Thirty intraosseous lines were placed in 27 newborns, in whom conventional venous access had failed. RESULTS: All the neonates survived the resuscitation procedure, with no long term side effects. CONCLUSION: Intraosseous infusion is quick, safe, and effective in compromised neonates.

Asphyxia Neonatorum↗
PubMed1999

Efficacy of tracheal gas insufflation in spontaneously breathing sheep with lung injury.

Tracheal gas insufflation (TGI) decreases dead space (V D) and can be combined with continuous positive airway pressure (CPAP) to decrease minute volume (VE) and effort of breathing. In 11 anesthetized sheep, we induced acute lung injury (ALI) through oleic acid (OA) infusion and studied the effects of TGI combined with CPAP (CPAP-TGI) at different TGI flows and with catheters of different designs. Sheep were randomized to two groups: Group A (n = 7) was placed on CPAP and CPAP-TGI at 10 and 15 L/min of insufflation flow delivered through a reverse thrust catheter (RTC). Group B (n = 4) was placed on CPAP and CPAP-TGI at a flow of 10 L/min delivered through a RTC, and through a straight flow catheter (SFC). Compared with CPAP alone, CPAP-TGI resulted in significantly lower VD, VE, pressure time product, and work of breathing. We found no additional benefit from TGI flow of 15 L/min, compared with 10 L/min, and no statistically significant difference between the SFC and the RTC. In conclusion, TGI can be combined with CPAP in this model of ALI to reduce ventilation and effort of breathing.

Animals↗
PubMed1997

Changes in left ventricular function in shocked newborns.

OBJECTIVE: To assess whether the change in cardiac output after volume replacement is due to elevation of stroke volume or heart rate and to determine the effect of mechanical ventilation on the hemodynamic situation. DESIGN: Prospective study. SETTING: A ten-bed neonatal intensive care unit (level III) at a university hospital. PATIENTS: 15 consecutive newborns with blood pressure below the 10th percentile related to age and weight. INTERVENTIONS: Volume replacement with Ringer's lactate 20 ml/kg body weight. MEASUREMENTS AND RESULTS: Before and after volume replacement, arterial pressure recordings, blood gas analysis, and an echocardiographic study were carried out. Left ventricular and aortic diameters were measured by the two-dimensional M-mode technique and velocity time integral of aortic flow by the pulsed color Doppler technique. From these data, stroke volume and cardiac output were calculated. Cardiac output (703 +/- 204 vs 826 +/- 166 ml/ min, p < 0.005) and cardiac index (267 +/- 69 vs 302 +/- 55 ml/min per kg body weight, p < 0.01) changed significantly due to an appreciable elevation in stroke volume (5.2 +/- 1.7 vs 5.8 +/- 1.7 ml, p < 0.05), whereas heart rate was unaltered (140 +/- 12 vs 142 +/- 20 beats/min; NS). The change in blood pressure (32 +/- 5 vs 38 +/- 8 mm Hg, p < 0.01) was also significant. Cardiac index before and after volume replacement showed a significant inverse correlation with the severity of respiratory disease expressed as alveolar-arterial oxygen difference (A-aDO2) (A-aDO2 vs cardiac index before volume replacement: r = -0.77, p < 0.001; after volume replacement: r = -0.73, p < 0.005) or oxygenation index (oxygenation index vs cardiac index before volume replacement: r = -0.73, p < 0.005; after volume replacement: r = -0.73, p < 0.005). Changes in left ventricular diastolic diameter, left ventricular systolic diameter, and fractional shortening were not significant. CONCLUSIONS: These results indicate that the major regulator of left ventricular output in newborns with hypovolemic or cardiogenic shock is stroke volume and not heart rate and that cardiac output depends on the severity of the respiratory disease.

Cardiac Output↗
PubMed1997

Tracheal mucus velocity remains normal in healthy sheep intubated with a new endotracheal tube with a novel laryngeal seal.

BACKGROUND: Tracheal mucus velocity (TMV), an index of mucociliary clearance, is reduced markedly in patients intubated with standard endotracheal tubes (ETTs) with high-compliance low-pressure (hi-lo) cuffs. The authors developed a new ultra-thin walled ETT in which the inflatable cuff is replaced with a no-pressure seal, positioned at the level of the larynx. The seal consists of 12 to 20 toroidal layers of thin polyurethane film ("gills") at the level of the vocal cords and prevents both air leak and fluid aspiration. The authors hypothesized that ETTs with the new laryngeal seal may impair TMV less than ETTs with inflated hi-lo cuffs do. METHODS: The TMV was measured in seven healthy female sheep by radiographically tracking the motion of small discs of tantalum inserted into the trachea through a bronchoscope. The TMV was measured in spontaneously breathing sheep before intubation (baseline) and after intubation with either a hi-lo ETT (control group) or after intubation with a new ETT with gills (study group). Four to six weeks later, the studies were repeated, but the sheep that were previously in the control group served as the study group, and those in the study group served as controls. RESULTS: Baseline TMV did not differ in the two groups. In the control group, TMV decreased significantly (by 67%) from baseline. In the study group, TMV did not differ significantly from baseline and remained steady during 3 h of intubation. CONCLUSIONS: The TMV does not change in sheep intubated with new ETTs with gills. The new ETT's may help promote a normal mucociliary clearance in patients who require ventilation.

Animals↗
PubMed1997

Clearance of mucus from endotracheal tubes during intratracheal pulmonary ventilation.

BACKGROUND: Intratracheal pulmonary ventilation (ITPV) is a form of tracheal gas insufflation in which all gas emerges in a cephalad direction from the tip of a reverse-thrust catheter positioned within an endotracheal tube. In vitro experiments have shown that this rapid gas flow, with 5 ml/h of normal saline added to the gas flow, continuously removes tracheal secretions from within the endotracheal tube. The authors evaluated its effectiveness to remove mucus in long-term studies in sheep. METHODS: Fourteen healthy sheep were tracheally intubated and ventilated for 3 days with ITPV or with volume-controlled ventilation. Measurements were made of the total amount of secretions within the endotracheal tubes (weight gain), the protein content within the endotracheal tubes, and the increase in resistance to constant air flow. The structure of the airways was examined grossly and histologically. Three additional sheep were ventilated for 24 h with ITPV, and Evans Blue dye was added to the saline to assess the distribution of the infused saline. RESULTS: There was significantly less mucus in endotracheal tubes of sheep ventilated with ITPV than with conventional ventilation, as shown by minimal weight gain (0.70 +/- 0.14 g vs. 2.44 +/- 0.81 g; P < 0.001), lower protein content (14.09 +/- 10.79 mg vs. 294.99 +/- 153.06 mg; P < 0.001), and lower resistance to constant air flow (6.15 +/- 0.54 cm H2O x 1(-1) x s(-1) vs. 15.34 +/- 5.28 cm H2O x 1(-1) x s(-1); P < 0.001). Results of gross and histological examinations of the tracheas of animals in both groups were similar, and the tracheas were well preserved. More than 95% of the instilled saline was recovered during ITPV. Only traces of Evans Blue dye were found near the tip of the endotracheal tubes. CONCLUSION: Intratracheal pulmonary ventilation makes it possible to keep the endotracheal tubes of sheep ventilated for 3 days free of mucus without suctioning.

Animals↗
PubMed1997

Intratracheal pulmonary ventilation and continuous positive airway pressure in a sheep model of severe acute respiratory failure.

STUDY OBJECTIVES: Previously we have shown that optimal pulmonary gas exchange can be sustained at normal airway pressures in a model of severe acute respiratory failure (ARF), using intratracheal pulmonary ventilation (ITPV), with weaning to room air. In an identical model of ARF, we have now explored whether ITPV, combined with continuous positive airway pressure (CPAP), can sustain adequate ventilation, with weaning to room air. DESIGN: Randomized study in sheep. SETTING: Animal research laboratory at the National Institutes of Health. INTERVENTIONS: ARF was induced in 12 sheep, using mechanical ventilation at peak inspiratory pressure of 50 cm H2O, but excluding 5 to 8% of lungs. Sheep were then randomized into two groups: the CPAP-ITPV group (n=6), in which ITPV was combined with a novel CPAP system; and a control group (n=6) in which the same CPAP circuit was used, but without ITPV. MEASUREMENTS AND RESULTS: All sheep in the CPAP-ITPV group were weaned to room air in 38.7+/-14 h. PaO2/fraction of inspired oxygen (FIO2) progressively increased from 108.8+/-43 to 355.7+/-93.1; PaCO2 remained within normal range; respiratory rate (RR) ranged from 18 to 120 breaths/min, and tidal volume (VT) was as low as 1.1 mL/kg. All sheep in the control group (CPAP alone) developed severe respiratory acidosis and hypoxemia after 4.8+/-4 h. PaO2/FIO2 decreased from 126.6+/-58.2 to 107.2+/-52.5 mm Hg, with a final PaCO2 of 166.8+/-73.3 mm Hg. CONCLUSIONS: All sheep treated with CPAP-ITPV maintained good gas exchange without hypercapnia at high RR and at low VT, with weaning to room air. All control animals treated with CPAP alone developed severe hypercapnia, respiratory acidosis, and severe hypoxemia, and were killed.

Acidosis, Respiratory↗
PubMed1996

Comparison of different modes of high-frequency ventilation in surfactant-deficient rabbits.

Various modes of high-frequency ventilation (HFV) have been developed to avoid the disadvantages of conventional mechanical ventilation. In the present study, we examined the hypothesis that high-frequency oscillation (HFO) is superior to high-frequency positive pressure ventilation (HPPV) and combined high-frequency ventilation (CHFV) in surfactant-deficient rabbits. The aim of the ventilator strategy was to adjust the mean airway pressure to 2 cm above critical opening pressure of the inflation limb of the respiratory system pressure volume (P/V) curve, achieve a normal tidal volume (VT) (5 ml/kg body weight) and apply repeated sustained inflations. We studied the effect of these HFV modes on oxygenation, lung mechanics and lung histology in 15 New Zealand White rabbits during a 6-hour experiment. Statistically, the HFO group demonstrated significantly better oxygenation (P < 0.05), lung mechanics (lung stability index: P < 0.05), and better lung tissue histology compared to the HPPV and CHFV groups. In contrast to the HPPV and CHFV groups, the P/V curves of the HFO group showed significant recovery over the 6-hour period after lavage. The lungs of the HFO-treated group had a more uniform distribution of alveoli and less overdistention than the HPPV group (P < 0.002), and less atelectasis than the CHFV group (P < 0.05). The HFO group had less lung injury than the CHFV groups (P < 0.01) and its lungs contained significantly less water than both other groups (P < 0.05). We conclude that the relationship between mean and end-expiratory pressures impacts strongly on both oxygenation and the progression of injury during HFV at the same mean airway pressures. The HFO group showed less acute lung injury than the other ventilatory groups.

Animals↗
PubMed1994

Spontaneous pneumocephalus in a newborn infant with myelomeningocele and hydromyelia.

The authors report a preterm boy, born at 35 weeks gestation with hydrocephalus and an open sacral myelomeningocele. Cranial ultrasound showed ventricular dilatation with posture-dependent intraventricular bright echoes, representing air. Ultrasound of the cervical spine and the craniocervical junction revealed marked hydromyelia of the whole spinal cord, as well as a Chiari II malformation. Air penetrating the enlarged central canal through the neural tube defect and subsequently ascending to the cranial cavity was demonstrated by fluoroscopy. After a review of the literature, the authors conclude that the association of spontaneous pneumocephalus with myelomeningocele could indicate severe hydromyelia. These malformations are readily demonstrated by ultrasound in newborn infants.

Humans↗
PubMed1991

Incidence of congenital heart disease in Tyrol, Austria 1979-1983.

The congenital heart disease incidence study was designed to collect valid data with respect to new diagnostic methods and to an improved system of preventive health care in order to compare the results with former studies. In the years 1979-1983 there were 41,725 live births in the Tyrol. Among these, 341 cases of congenital heart disease were recognised giving an incidence of 8.2 per 1000. This does not imply a real increase in congenital heart disease, but can be explained by differences in methodological bias. As in previous investigations as well in our study, ventricular septal defect has been noted as the most common cardiac lesion. A remarkable result is a 56% incidence of spontaneous closures. Within five years, 81 children died; 89% of them died by the age of one year.

Austria↗