Biomedical subjects
H J Ladegaard-Pedersen
Publications and source records attributed to H J Ladegaard-Pedersen.
A circle system without carbon dioxide absorption.
An anaesthetic circle system without a carbon dioxide absorber is described. The efficiency of the circle, i.e., the fraction of alveolar gas in the outflow from the circle, was measured in 15 patients during halothane anaesthesia or neurolept analgesia. The fraction ranged from 0.88 to 0.95 (mean 0.91), while the ratio between the alveolar ventilation and the fresh gas inflow ranged from 0.97 to 1.71. The efficiency was not correlated to this ratio. There was no need for hyperventilation if the fresh gas inflow was 10% higher than the alveolar ventilation required to maintain normal PaCO2. The circle was used in 50 patients manually ventilated by nurse anaesthetists. Mean fresh gas inflow was 60 ml/kg. Mean PaCO2 was 5.47 kPa (41 mmHg). In a similar group of 50 other patients, in which the standard circle used in the department was employed, the mean PaCO2 was 4.80 kPa (36 mmHg). The frequency of hypercapnia was equal in the two groups, but hypocapnia was not seen when the circle without absorber was used.
Accuracy and reproducibility of arterial blood-gas and pH measurements.
In 30 patients blood samples were taken from both radial arteries and analysed for PCO2, PO2 and pH. The influence of sampling technique on the accuracy of blood-gas analysis was determined. The 95% confidence limits for PCO2 measurements were +/-0.32 kPa (2.4 mmHg), and for PO2 measurements were +/-1.16 kPa (8.8 mmHg) in the range below 20 kPa, and +/-2.94 kPa (22.0 mmHg) above 20 kPa. For pH, the 95% confidence limits were +/-0.014. Only the PO2 measurements were significantly influenced by the sampling procedure.
Intravenous lidocaine as a suppressant of persistent cough caused by bronchoscopy.
The effect of intravenous lidocaine in the treatment of persistent cough occurring after diagnostic bronchoscopies performed under general anaesthesia was investigated in a controlled clinical trial. The study comprised 28 adults patients, all of whom had regained consciousness after anaesthesia. Fifteen patients were treated with lidocaine (1.05 mg/kg body weight) and 13 patients with placebo (saline). In each patient the intravenously injected dose was repeated once after 5 min. In 11 of the 15 patients (73%) who received lidocaine coughing ceased, while it continued in all 13 patients in the placebo group. The difference is highly significant (P less than 0.001). None of the patients developed side effects such as hypotension, arrhythmias, central nervous system symptoms or respiratory depression after injection of lidocaine. It is therefore concluded that intravenous lidocaine in man is a safe and useful cough-suppressant.
[Prolonged endotracheal intubation].
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[Letter: Blood pressure measured in mm Hg or kilopascal?].
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A comparison between the changes in the distribution volumes of inulin and [51Cr]EDTA after major surgery.
In 12 patients undergoing major surgery the distribution volumes of inulin (V1) and [51Cr]EDTA (V-E) were measured simultaneously by a single injection technique the day before and the day after the operation. Preoperatively V-I was correlated to V-E, and both these volumes were correlated to the plasma volume (PV). Postoperatively only the correlation between V-I and PV was found. The changes in V-I and PV were significantly correlated, but there was no correlations between the changes in V-I and V-E or between the changes in these volumes and in the body weight. Inulin seems to be a better tracer than [51Cr]EDTA, but the lack of correlation between the changes in V-I and V-E and the changes in body weight raises some doubts as to the physiological significance of the measured changes.