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Biomedical subjects

O Werner

Publications and source records attributed to O Werner.

At least 109 records · Page 6Linked to original sources
PubMed1984

Gas exchange and haemodynamics during thoracotomy.

Cardiac index, systemic and pulmonary arterial pressures, carbon dioxide elimination and ventilation of each lung were studied during thoracotomy. Seventeen patients, placed in the full lateral position, were ventilated mechanically through a Carlens' tube to moderate hypocapnia. Mean cardiac index increased by 12% as the pleura was opened (P less than 0.05), with no further change during surgery on the still ventilated upper lung. Mean arterial pressure was unchanged after opening the pleura, but decreased from 114 +/- 15 mm Hg (mean +/- 1 SD) to 104 +/- 18 mm Hg during surgery on the lung (P less than 0.01). Mean pulmonary artery pressure was unchanged. There was a significant (P less than 0.01) increase in carbon dioxide elimination from the upper lung when the pleura was opened. In addition, the ventilation of this lung increased significantly (P less than 0.05). Mean end-tidal PCO2 of the lower lung increased from 4.1 to 4.2 kPa after opening the pleura, while that of the upper lung increased from 3.0 to 3.6 kPa (P less than 0.01). VD/VT decreased from 43 to 38% as the pleura was opened (P less than 0.01). During surgical handling of the lung, marked decreases in ventilation, compliance, carbon dioxide elimination and end-tidal PCO2 were observed in the upper lung. We conclude that ventilation-perfusion mismatch decreased on opening the pleura, and that neither opening the pleura nor the subsequent lung surgery (both lungs being ventilated) caused any clinically important derangements in haemodynamics or oxygenation.

Anesthesia, General↗
PubMed1984

Carbon dioxide elimination from each lung during endobronchial anaesthesia. Effects of posture and pulmonary arterial pressure.

The ventilation and carbon dioxide elimination of each lung, and pulmonary arterial pressure, were studied in 17 patients during the early phases of anaesthesia for pulmonary surgery. The patients were ventilated mechanically to moderate hypocapnia. Expired tidal volume and carbon dioxide elimination rate of the lung to be operated on, and of the other lung, were similar in the supine position. There was a significant (P less than 0.01) increase in ventilation and a decrease in end-tidal PCO2 of the upper lung after turning the patient on to the side. Simultaneously, the physiological deadspace fraction of tidal volume (VD/VT) increased from 42 to 45% (P less than 0.05). Mean pulmonary arterial pressure (MPAP) increased slightly as surgery on the chest wall commenced. A concomitant increase of carbon dioxide elimination from the upper lung occurred also, although the distribution of ventilation, between the lungs, was unchanged in comparison with the conditions during undisturbed anaesthesia. Individual changes in MPAP (delta MPAP) and corresponding changes in VD/VT (delta (VD/VT)) were negatively correlated (r = -0.68, P less than 0.01). The regression equation was delta (VD/VT) (%) = 0.7 - 0.83 X delta MPAP (mmHg). It was concluded that variations in pulmonary arterial pressure during surgical stimulation may significantly affect the pattern of carbon dioxide elimination in the lungs. However, there was no evidence that these effects were important clinically.

Anesthesia, Inhalation↗
PubMed1984

Halothane dissolved in fat as an intravenous anaesthetic to rats.

The anaesthetic properties of a halothane-in-fat solution given either as a single i.v. dose or as a continuous i.v. infusion were investigated in rats. 0.3 ml of a 5% solution of halothane in fat emulsion was injected i.v. into 15 awake rats. At the end of the 30 s injection, all rats had collapsed from the upright position and showed no response to a firmly applied tail clamp. Breathing usually became shallow and irregular just after injection. Two rats died. In the surviving rats, movement in response to clamping of the tail reappeared after some 30 s (range 15-90 s). The rats regained the upright position after about 100 s, and appeared fully awake about 3 min (range 2-5 min) after injection. Surviving rats behaved normally after the experiment, and gained in weight. They were killed 1-29 days later. The lungs, kidneys, heart, brain and liver had a normal macroscopic and microscopic appearance. In a second set of experiments (n = 9), a 10% solution of halothane was continuously infused i.v. (3.75 microliters min-1). The anaesthetic depth, as well as the mean arterial pressure, heart rate, respiratory rate and arterial PCO2 and PO2 were similar to values observed during inhalation of halothane in air at an inspired concentration of 1.1%. By doubling the infusion rate, MAP was reduced by 23%. It was easy to adjust anaethestic depth by changing the infusion rate and recovery was fast.

Anesthesia, Intravenous↗
PubMed1984

Intravenous infusion of halothane dissolved in fat. Haemodynamic effects in dogs.

Eight harrier dogs received an i.v. infusion of halothane dissolved 1:9 in a fat emulsion for i.v. nutrition (Intralipid, Vitrum). The rate of infusion was adjusted to maintain end-tidal halothane concentrations of 0.7% and 1.4%. At 1.4%, mean arterial pressure decreased to 76 +/- 8 mmHg (10.1 +/- 1.0 kPa) (mean +/- s.e.mean) from a pre-infusion value of 122 +/- 6 mmHg (16.2 +/- 0.8 kPa) (P less than 0.01). The concomitant decrease in cardiac output was 39% and left ventricular maximum dp/dt decreased by 50% (P less than 0.01). Changes in systemic vascular resistance and pulmonary arterial pressure were small. The haemodynamic responses during halothane inhalation, to corresponding end-tidal concentrations, were similar. Arterial and mixed venous halothane concentration increased in proportion to end-tidal concentration. There were no changes in arterial PO2 during the halothane-in-fat infusion. Triglyceride concentrations in plasma increased 12-fold. Haemodynamic recovery after the infusion was fast. We conclude that the halothane-in-fat infusion caused a dose-dependent depression of myocardial contractility and arterial pressure, similar to that seen during inhalation, and that end-tidal concentration could be used for control of the infusion rate.

Anesthesia, Intravenous↗
PubMed1984

Some notes on the hormonal and haemodynamic responses to stressful stimuli.

The symptoms of hypertension in pregnancy may be exacerbated by pain or other stressful stimuli, arising during labour. The anaesthetist has a part to play in alleviating these problems, through his knowledge of analgesic techniques. In addition, pre-eclampsia sometimes necessitates delivery by cesarean section. Increases in arterial pressure during intubation and surgery may be poorly tolerated. Proper anaesthetic management of pre-eclampsia therefore requires knowledge of circulatory and other, e.g. hormonal, responses to pain and other types of stress. The present paper gives a short review of these aspects.

Adrenergic beta-Antagonists↗
PubMed1983

Sources of error and their correction in the measurement of carbon dioxide elimination using the Siemens-Elema CO2 Analyzer.

The Siemens-Elema CO2 Analyzer 930 allows calculation of carbon dioxide elimination from the instantaneous measurement of expired gas flow (VE) and carbon dioxide fraction (FECO2). VE is measured in the ventilator and FECO2 at the Y-piece. The most important source of error in the measurement of carbon dioxide elimination is rebreathing, which corresponds to about 24 ml of end-expiratory gas per breath with the standard Y-piece and tubing. This problem may be decreased by the use of non-return valves in the Y-piece. Allowance must be made for the effects of intermolecular interaction between carbon dioxide and the carrier gas, as the reading is about 20% greater with nitrous oxide than with oxygen. This problem can be largely circumvented by calibration with appropriate gas mixtures. Errors resulting from analyser delay are small, and are eliminated completely by the inclusion of fast electronic components. Carbon dioxide analysis is linear with air as carrier gas, but slightly alinear with nitrous oxide in oxygen mixtures. This error can be minimized by using calibration gases with a carbon dioxide content close to that of expired gas. The expiratory flow meter is linear if kept in good condition. Variations in temperature and water content of expired gas cause overestimation of mean expired carbon dioxide fraction (FECO2) by a factor of 1.01-1.02. Compressed gas in the tubing causes a small error which may be neglected at normal airway pressures with tubing of low compliance. Carbon dioxide measurement is slightly affected by barometric pressure. During mechanical ventilation of the lungs in 10 patients with air, FECO2 obtained after corrections for known errors agreed well with Scholander analysis of mixed expired gas.

Carbon Dioxide↗
PubMed1983

Metoprolol, fentanyl and stress responses to microlaryngoscopy. Effects on arterial pressure, heart rate and plasma concentrations of catecholamines, ACTH and cortisol.

Forty patients undergoing microlaryngoscopy were anaesthetized with thiopentone and nitrous oxide. Twenty patients received metoprolol 200 mg in a slow-release tablet once daily for 4 days up to, and including, the morning of operation, and 10 mg i.v. shortly before induction of anaesthesia. The other patients received placebo tablets and physiological saline i.v., instead. Both groups of 20 patients were further subdivided, half of the patients receiving fentanyl 1.0-1.5 mg during anaesthesia, the effect of which was antagonized by naloxone at the end of the procedure. The other patients received saline i.v. instead of fentanyl or naloxone. Metoprolol decreased heart rate and the general level of arterial pressure during anaesthesia, but did not affect the fluctuations in pressure. Arterial plasma noradrenaline concentrations during microlaryngoscopy were enhanced by metoprolol, in comparison with placebo, the reverse being the case for cortisol concentrations. Fentanyl decreased arterial pressure and plasma ACTH and cortisol concentrations regardless of whether the patient had received metoprolol. Plasma adrenaline and noradrenaline concentrations were decreased by fentanyl in the patients receiving metoprolol.

Adrenocorticotropic Hormone↗
PubMed1983

Ventricular arrhythmia or supraventricular arrhythmia with aberrant conduction? An electrocardiographic study in halothane-anaesthetized children undergoing adenoidectomy.

The electrocardiograph (ECG) was recorded continuously in 20 children undergoing adenoidectomy during halothane anaesthesia. Five surface ECG leads and an oesophageal lead were used. In 11 children, there were QRS complexes which had a shape distinctly different from that of the ordinary sinus-evoked beats. Except in one child, these anomalous QRS complexes first made their appearance during surgery, although the arrhythmia continued until 0-1 min after adenoidectomy in some children. The severity ranged from that of occasional anomalous QRS complexes with uniform shape to that of a fast irregular rhythm with a variety of QRS shapes. Although the anomalous QRS complexes were premature, P waves and P-P intervals were unchanged. In some children, there appeared to be ventricular capture beats and fusion beats. Because of this, and in view of evidence gathered from studies in animals, by other authors, we considered it likely that the anomalous beats were ventricular in origin.

Adenoidectomy↗
PubMed1983

Narcotic antagonism by naloxone. Few side-effects after a short procedure?

Twenty patients undergoing microlaryngoscopy were anaesthetised with thiopentone and nitrous oxide. Half of the patients received 1.0-1.5 mg of fentanyl during anaesthesia, the effect of which was antagonised by naloxone 0.4 mg intravenously and 0.4 mg subcutaneously. The other patients served as controls and received saline instead of fentanyl and naloxone. Fentanyl markedly reduced mean arterial pressure and the heart rate-systolic arterial pressure product during microlaryngoscopy. Conversely, there were significant increases in these measurements after naloxone had been given. However, there were no significant differences between patients given fentanyl with naloxone, and those given saline, in respect of arterial pressure, heart rate or dysrhythmia during recovery. No patient vomited, or appeared nauseated when observed afterwards in the operating room. One patient vomited several hours after naloxone.

Aged↗
PubMed1983

Cardiac arrhythmias in non-intubated children during adenoidectomy. A comparison between enflurane and halothane anaesthesia.

The incidence of cardiac arrhythmias, heart rate, blood pressure, capillary perfusion and end-tidal CO2 tension were studied in 167 healthy children 1-12 years of age undergoing adenoidectomy (n = 82) and myringotomy (n = 85) during enflurane and halothane anaesthesia. The incidence of cardiac arrhythmias was significantly lower during myringotomy than during adenoidectomy. In children undergoing adenoidectomy the incidence of arrhythmias was 38.9% during enflurane anaesthesia and 86.6% during halothane anaesthesia (P less than 0.001). In the halothane group ventricular arrhythmias were observed in 19 patients (41.3%) but only in one child (2.8%) in the enflurane group. The ventricular arrhythmias seen during halothane anaesthesia were unifocal in six patients and multifocal in five and classified as ventricular tachycardia in eight children. Heart rate was increased by about 40% at the onset of ventricular arrhythmias. The heart rate remained unchanged with enflurane anaesthesia during surgery, which may reflect a decreased sympathomimetic activity. It is suggested that the low incidence of ventricular arrhythmias during enflurane anaesthesia may be explained by the combination of a reduced sympathomimetic activity and a lowered susceptibility of the myocardium to the actions of endogenous catecholamines.

Adenoidectomy↗
PubMed1983

Modification by baroreceptor feedback of circulatory responses to noxious stimuli during anaesthesia in cats.

In eight cats anaesthetized with chloralose, the carotid sinus on one side was either exposed to systemic arterial pressure or perfused with a pump in order to control sinus pressure. Baroreceptor influences from the contralateral carotid sinus and from the aortic arch were interrupted by denervation. Arrangements were made for intermittent electric stimulation of pain fibres in somatic and visceral nerves with stimulation parameters chosen to elicit reproducible increases in arterial blood pressure and in skeletal muscle vascular resistance. The elicited increases in arterial pressure and muscle vascular resistance were both about 40% smaller when the carotid sinus was exposed to systemic arterial pressure in comparison with the experimental condition of a constant carotid sinus pressure. I.v. metoprolol (0.1-0.3 mg kg-1) reduced base-line arterial pressure, but did not attenuate the arterial blood pressure increase in response to pain stimulation. The baroreceptor modulation of the haemodynamic response to the pain stimulation was not affected by metoprolol.

Anesthesia, General↗
PubMed1982

Effect of cardioselective beta-blockers on the heart rate and arterial pressure responses to laryngoscopy.

The effects of the cardioselective beta-blockers practolol (Eraldin, ICI) and metoprolol (Seloken, Hässle) were studied during microlaryngoscopy. I. v. practolol (0.4 mg/kg before and 0.2 mg/kg during anaesthesia) did not protect against increases in arterial pressure, although heart rate was reduced. Oral metoprolol (0.2 g for 4 days) reduced the level of arterial pressure both before and during anaesthesia. Variations in arterial pressure were not attenuated. Very low levels of arterial pressure were seen, and variations in arterial pressures were attenuated when metoprolol was combined with fentanyl.

Adrenergic beta-Antagonists↗