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Biomedical subjects

O Werner

Publications and source records attributed to O Werner.

At least 91 records · Page 5Linked to original sources
PubMed1987

Variations in lung volume and compliance during pulmonary surgery.

Functional residual capacity (FRC) and breath-by-breath compliance of the ventilatory system (Crs) were measured in 10 mechanically ventilated patients during anaesthesia for lung surgery (pneumonectomy, lobectomy, lung or pleural resections or exploratory thoracotomy). In eight patients not requiring pneumonectomy, FRC of the lower lung decreased by 8 +/- 9% (mean +/- 1 SD) (P less than 0.05) while that of the upper lung increased by 75 +/- 24% (P less than 0.001) when the patient was turned to the lateral position. When the pleura was opened, FRC of the lower lung decreased by a further 10 +/- 10% (P less than 0.01). One-lung ventilation (OLV), however, increased FRC of the lower lung back to the value found in the supine position before surgery. When two-lung ventilation was re-established, FRC of the lower lung was about the same as during corresponding stages before OLV. In the two patients who underwent pneumonectomy, FRC of the remaining lung was about 30% greater after OLV than at corresponding stages before surgery. In the patients not requiring pneumonectomy, Crs decreased from 29 +/- 6 ml/cm H2O to 23 +/- 6 ml/cm H2O (P less than 0.05) on the lower side when the patient was turned on his side. The corresponding figures on the upper side were 24 +/- 8 ml/cm H2O and 30 +/- 5 ml/cm H2O respectively (P less than 0.05). There was no further significant change when the pleura was opened. After surgery when the patient was turned to the supine position, Crs of the lung not operated on was almost the same as before surgery.

Adult↗
PubMed1987

Hemodynamic effects of dopamine during thoracic epidural analgesia in man.

The cardiovascular effects of dopamine were studied before and during thoracic epidural analgesia (TEA) in eight patients prior to abdominal aortic surgery. Dopamine was infused at rates of 2, 4, and 8 micrograms X kg-1 X min-1. Mean plasma dopamine concentration increased proportionally to the infusion rate. Before TEA, dopamine 8 micrograms X kg-1 X min-1 decreased systemic vascular resistance 4 +/- 4 mmHg min X 1-1 (m +/- SD) (P less than 0.05), but increased mean arterial pressure 15 +/- 12 mmHg (P less than 0.01), cardiac output 1.9 +/- 1.0 1 X min-1 (P less than 0.01), heart rate 10 +/- 9 beats X min-1 (P less than 0.05), and plasma norepinephrine concentration 544 +/- 252 pg X ml-1 (P less than 0.01). After the induction of TEA, which extended above the T2 dermatome and below the L2 dermatome, saline and albumin were infused to maintain central venous and pulmonary capillary wedge pressures. TEA reduced mean arterial pressure from 96 +/- 18 to 55 +/- 8 mmHg (P less than 0.01), cardiac output from 4.7 +/- 0.9 to 3.9 +/- 0.9 1 X min-1 (P = 0.05), systemic vascular resistance from 21 +/- 6 to 14 +/- 3 mmHg min X 1-1 (P less than 0.05), and plasma norepinephrine concentration from 394 +/- 141 to 207 +/- 73 pg X ml-1 (P less than 0.01). The plasma epinephrine concentration was reduced 49% after the induction of TEA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Measurement of lung volume by sulfur hexafluoride washout during spontaneous and controlled ventilation: further development of a method.

An open circuit tracer gas washout method for measurement of lung volume in patients during anesthesia and intensive care is described and tested. The method employs a device for dispensing the tracer gas, sulfur hexafluoride (SF6), a fast SF6 analyzer, a pneumotachograph, and a computer. The dispensing device delivers SF6 into the airway in proportion to instantaneous inspiratory flow so that inspiratory SF6 concentration is held constant, usually at about 0.5%, regardless of the inspiratory flow pattern. The amount of SF6 present in the lungs at the end of a washin is calculated during washout from signals representing expired SF6 concentration and expired flow. From this, lung volume is derived. Accurate and reproducible results were obtained in lung model tests during ventilation with air, N2O in O2, and halothane in O2. Functional residual capacity (FRC) was measured both with SF6 washout and nitrogen washout in five mechanically ventilated patients. This gave the regression equation: FRCSF6 = 10 ml + 1.04 x FRCN2, r = 0.99. A similar close agreement was observed for total lung capacity (TLC) and residual volume (RV) measurements in eight healthy, spontaneously breathing subjects: TLCSF6 = 91 ml + 1.01 x TLCN2, r = 0.99; RVSF6 = -32 ml + 0.97 x RVN2, r = 0.95. Comparison with body plethysmography in eight healthy, sitting subjects gave the regression equation: FRCSF6 = 180 ml + 0.96 x FRCbox, r = 0.99. The median (range) for the coefficient of variation at duplicate determinations in 10 anesthetized, paralyzed, and mechanically ventilated adults was 3.0% (0.2-6.6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Left-to-right shunt assessed by thermodilution during surgery for congenital heart disease.

In nine children with congenital heart defects, left-to-right shunting was assessed during open-heart surgery by injecting cold 5% glucose solution through a left atrial line and detecting temperature change with a pulmonary arterial thermistor. The shunt was quantified by recording the temperature after injecting the same amount of cold glucose solution also through a central venous line. Oximetric determination of the left-to-right shunt was used as a reference. The result was expressed as shunt flow divided by pulmonary blood flow (Qshunt/Qp). The regression equation then obtained was Qshunt/Qp by thermodilution = 0.05 + 0.87 x Qshunt/Qp by oximetry. The residual standard deviation around the line of regression was 0.03. The thermodilution technique can be used for rapid assessment of the presence and magnitude of left-to-right shunting, provided that there is opportunity for the indicator to mix adequately in the main blood stream before shunting occurs.

Blood Pressure↗
PubMed1986

Haemodynamic effects of pretreatment with metoprolol in hypertensive patients undergoing surgery.

Thirty hypertensive patients scheduled for cholecystectomy or hernia repair under general anaesthesia with thiopentone-fentanyl-nitrous oxide-pancuronium were divided into two groups of 15. One group received metoprolol tablets 200 mg in a slow release form, once daily for at least 2 weeks including the morning of surgery. In addition, metoprolol 15 mg was injected i.v. shortly before the induction of anaesthesia. The other group received placebo tablets and saline. Two patients in the treatment group and one patient in the placebo group were subsequently excluded, because of complications during treatment. Metoprolol significantly reduced arterial pressure both during undisturbed anaesthesia, during intubation and after extubation. A similar tendency was observed also during surgery, although it was not quite significant (P = 0.055). However, metoprolol had no effect on variations in systemic vascular resistance. Mean pulmonary arterial pressures during anaesthesia and surgery were significantly greater in the control, than in the metoprolol, group. Central venous pressure (CVP) and pulmonary arterial occlusion pressure (PAOP) increased significantly in both groups in response to the surgical stimulus. There was no significant difference between the groups in PAOP and CVP. One patient in the metoprolol group had marked bradycardia (minimum heart rate 26 beat min-1) after neostigmine and atropine; otherwise metoprolol pretreatment was tolerated well.

Adult↗
PubMed1986

Changes in functional residual capacity during cardiac surgery.

A gas washout technique was used to measure the functional residual capacity (FRC) in eight patients during anaesthesia for cardiac surgery. The patients were anaesthetized with droperidol, fentanyl and nitrous oxide, alcuronium was given and the lungs were ventilated with a volume controlled ventilator. FRC was measured at three stages before skin incision, after sternotomy but before cardiopulmonary bypass, and after closure of the sternum. The pleural cavities were intact in all patients during the operation. FRC before skin incision was 1.7 +/- 0.5 litre (mean +/- 1 SD). A 55% mean increase in volume was noted after sternotomy and placement of the sternal retractor (P less than 0.001). Mean FRC after sternal closure was 16% lower than the preincision value (P less than 0.05). Arterial Po2 was measured in 22 other patients who underwent coronary artery bypass surgery and in whom F/o2 was 0.5. Pao2 increased significantly when the sternum was opened, but decreased after cardiopulmonary bypass. There was a further significant decrease on closure of the sternum.

Aged↗
PubMed1986

Clonidine and the sympatico-adrenal response to coronary artery by-pass surgery.

Clonidine was administered intravenously in an attempt to limit sympatico-adrenal activity and thereby reduce the incidence of arterial hypertension associated with coronary artery by-pass graft surgery (CABG). Forty patients scheduled for CABG were assigned to two groups. Twenty patients received clonidine 4 micrograms kg-1 before surgery, 2 micrograms kg-1 after cardiopulmonary by-pass and 1 microgram kg-1 when the skin was sutured. The other 20 patients served as controls. All patients were anesthetized with fentanyl, droperidol, nitrous oxide and alcuronium. During surgery 5 min after sternotomy, mean arterial pressure was 13 mmHg lower (P less than 0.01) in the clonidine group, while after operation the difference between the groups was negligible. Both during and after surgery the plasma catecholamine concentrations were significantly lower in the clonidine group (P less than 0.01). The greatest difference between the groups was seen 90 min after operation, when plasma noradrenaline and plasma adrenaline concentrations in the clonidine group were less than 1/3 of those in the control group (P less than 0.01). As judged by catecholamine concentrations clonidine was effective in attenuating sympatico-adrenal hyperactivity during and after surgery. Postoperative arterial hypertension was not reduced, however, and it is concluded that other factors besides sympatico-adrenal hyperactivity must be important.

Adrenocorticotropic Hormone↗
PubMed1986

Changes in lung volume and lung-thorax compliance during cardiac surgery in children 11 days to 4 years of age.

To examine the effects of cardiac surgery and cardiopulmonary bypass (CPB) on the lung, functional residual capacity (FRC) and lung-thorax compliance were measured at four stages during open heart surgery in 15 children. The patients were anesthetized with fentanyl/droperidol and N2O/O2, paralyzed, and ventilated with volume-controlled mechanical ventilation at 20-30 breaths/min. FRC was measured by tracer gas washout. Static lung-thorax compliance (CLT) was calculated as tidal volume divided by the airway pressure difference between the end of the postinspiratory pause and the end of the expiration, and also from the increase in FRC caused by adding 5 cmH2O of PEEP (CLT[FRC]). Before skin incision, both FRC and compliance were closely correlated with weight and length. During this stage, FRC was 21 +/- 5 ml/kg, CLT 0.90 +/- 0.21, and CLT(FRC) 1.28 +/- 0.35 ml X cmH2O-1 X kg-1 X PEEP 5 increased FRC by 34 +/- 9%. In patients with intact pleural cavities throughout the operation (n = 10), FRC increased by 4 +/- 2 ml/kg when the sternum was retracted (P less than 0.01). During CPB, FRC decreased by 4 +/- 3 ml/kg (P less than 0.01), and FRC at the end of surgery was 5 +/- 4 ml/kg less than before skin incision (P less than 0.01). In these ten children, there was a 13% and 6% decrease in mean CLT and CLT(FRC), respectively, during the operation (P less than 0.05) and mean CLT(FRC) was at least 40% greater than CLT during all four stages (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1985

An analyzer for in-line measurement of expiratory sulfur hexafluoride concentration.

An infrared analyzer for the inert tracer gas sulfur hexafluoride (SF6) is described and evaluated. The analyzer consists of a transducer and a processor unit. It is designed to operate in a nonrebreathing system with a ventilator and a computer. The transducer, which is placed over a cuvette with windows in the ventilator tubings, reads the SF6 concentration in the airway during the expiratory phase. At the end of the inspiratory phase, the zero level of the instrument is automatically reset. The response time and linearity of the analyzer were tested, and interference by other gases was assessed. Full response was reached within 20 ms after a sudden introduction of 0.5% SF6 into the cuvette. The analyzer-computer system had adequate linearity below 0.5% of SF6. Oxygen, nitrogen, and humid air had no influence on the analyzer signal. One hundred per cent nitrous oxide, 4% enflurane, 4% isoflurane, and 4% halothane caused signals corresponding to 0.010, 0.023, 0.022, and 0.043% SF6, respectively. Due to the method for zero reset, the importance of interference from these gases is greatly reduced when inspired and expired concentration approach each other. The disturbance from CO2 (10% CO2 gave a signal corresponding to 0.020% SF6) can be compensated for by including a CO2 analyzer in the set-up. The rapid response and the high sensitivity of the analyzer may make it useful for studies of pulmonary gas mixing and for measurements of lung volume during mechanical ventilation.

Equipment Design↗
PubMed1985

Measurement of functional residual capacity by sulfur hexafluoride washout.

Measurement of functional residual capacity (FRC) by the open-circuit multiple breath tracer gas washout technique is an established method. A system based upon washout of sulfur hexafluoride (SF6) during mechanical ventilation is described. The central unit in the system is a sensitive and rapid-response infrared SF6 analyzer. SF6 is washed in until the alveolar concentration of SF6 is 0.5%, a concentration so low that the supply of other gases is hardly influenced. During washout, the flow of SF6 from the lungs is calculated by a computer every 10 ms from signals representing expiratory flow and SF6 concentration. The total volume of SF6, washed out, is calculated by integration of SF6 flow. Since the alveolar concentration at the end of washin is known, the lung volume may be obtained. The measurement procedure is highly automated and the result is presented by the computer immediately after washout. Accurate and reproducible results in model lung tests were obtained during air and N2O/O2 ventilation. Comparison with body plethysmography (FRCBOX) in eight sitting healthy subjects gave the following: FRCSF6 = 7 ml + 0.98 X FRCBOX, r = 0.99. Comparison with nitrogen washout (FRCN2) in five postoperative patients gave the following: FRCSF6 = 59 ml + 0.97 X FRCN2, r = 0.97. FRCSF6 during N2O/O2 ventilation was the same as during air/O2 ventilation in a group of paralyzed patients. The measurement system has not been tested in patients with obstructive lung disease.

Adolescent↗
PubMed1985

Antagonism of fentanyl and alfentanil by intravenous plus subcutaneous naloxone. Pattern of ventilatory depression after a short procedure.

Twenty patients undergoing microlaryngoscopy were anaesthetized with thiopentone. Half received fentanyl supplementation (about 8.5 micrograms/kg) and the other half alfentanil (about 65 micrograms/kg). Both groups were given naloxone 0.4 mg intravenously plus 0.4 mg subcutaneously shortly after the procedure which lasted some 12 minutes. The degree of ventilatory depression was assessed by a CO2 rebreathing test. The ventilation at an end-tidal PCO2 of 8.0 kPa (V8.0) was noted, and the findings related to a control value obtained on the day before anaesthesia. In the fentanyl group, V8.0 was significantly (p less than 0.05) less one hour after naloxone than 15 minutes after, and remained significantly below the control value for the first 8 hours after microlaryngoscopy. A second peak in plasma fentanyl concentration was observed four hours postoperatively in three patients. Respiratory depression in the alfentanil group was less pronounced and of shorter duration than in the fentanyl group. Postoperative plasma alfentanyl concentration decreased progressively with time in every patient.

Aged↗
PubMed1985

Cardiovascular studies during controlled baroreflex activation in the dog: I. Effects of enflurane.

In chloralose-anaesthetized dogs the carotid sinuses were bilaterally perfused with blood from a femoral artery, either at systemic arterial pressure through a direct by-pass or with a pump in order to control the sinus pressure. Influences from cardiac receptors and aortic baroreceptors were eliminated by denervation. Administration of enflurane (1.6% end-tidal concentration) with the presence of barostatic modulation, i.e. the carotid sinuses were perfused at prevailing systemic arterial pressure, reduced cardiac performance (cardiac output, cardiac contractility, heart rate and left ventricular stroke work) and mean arterial pressure. When barostatic compensation of enflurane-induced circulatory changes was prevented by maintaining sinus perfusion pressure constant at the pre-enflurane level, these haemodynamic alterations, with the exception of cardiac output, were significantly more pronounced. Furthermore, systemic vascular resistance decreased. We conclude that barostatic reflexes significantly modify cardiovascular depressive effects of enflurane.

Animals↗
PubMed1985

Hemodynamic effects of sternum closure after open-heart surgery in infants and children.

Eight children (age 4 months - 9 years) were studied after surgical correction of congenital heart defects. Sternum closure reduced mean arterial pressure by 7% (p less than 0.05) and cardiac output by 14% (p less than 0.01), and increased central venous pressure by 2 mmHg (p less than 0.05). There was evidence of a decrease in intracardiac blood volume. It is suggested that the circulatory effects of sternum closure were due to increased pressure outside the heart, which reduced the pressure across the heart wall and the end-diastolic volume.

Age Factors↗