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Biomedical subjects

K N Christensen

Publications and source records attributed to K N Christensen.

At least 19 recordsLinked to original sources
PubMed1989

Computerized monitoring of depth of anaesthesia with isoflurane.

Changes in brain activity were studied at different depths of isoflurane anaesthesia. Ten healthy women (ASA group I) were investigated during non-critical surgery. Two channels of the EEG were stored on tape simultaneously with alveolar concentration of carbon dioxide, inspired oxygen concentration, mean arterial pressure, ECG and temperature. Signal processing was made offline. Spectral information from 2-s EEG segments was extracted using autoregressive modelling. Repetitive hierarchical clustering was used to define a common learning set of basic patterns. With this learning set, the EEG was classified, and the results presented in a class probability histogram. The basic patterns were related to the clinical depth of anaesthesia in all patients and assigned specific colours. Using this colour code, the class probability histogram showed a high degree of simplicity. Decreasing or increasing the isoflurane concentration caused the same trend in the class profile in all patients. This indicates that the EEG pattern might be a sensitive tool for decision making during administration of general anaesthetics.

Adult↗
PubMed1987

[Effects of induction and supplementary doses of atracurium. Dose-response relationship, spontaneous reversion period, cardiovascular effect and clinical signs of histamine liberation].

The effects of an induction dose of atracurium 0.6 mg/kg and supplementary doses of 0.2 mg/kg and 0.1 mg/kg were investigated in 20 patients undergoing non-urgent laparotomy while anesthetized with halothane-N2O-O2. Atracurium was the only muscle relaxant used. Complete neuromuscular block was achieved in all patients, lasting an average of 37 min. Following a supplementary dose of 0.2 mg/kg or 0.1 mg/kg the neuromuscular block was extended on average for a further 25 min (range 13-37 min) or 15 min (range 5-30 min), respectively. The time to spontaneous reversion of complete neuromuscular block at TOF = 0.75 was 39 min (mean). Neither blood pressure nor pulse rate changed significantly following injection of the induction dose. In 3 patients (15%) there was a brief period of erythema with no simultaneous change in pulse rate or blood pressure after administration of the induction dose. The erythema did not recur in the same patients following the supplementary doses. Transitory rises in AST and LDH were noted in 1 patient.

Adult↗
PubMed1979

Cameco anaesthetic ventilator with a modified Mapleson D circuit.

A modified Mapleson D circuit has been used in connection with a Cameco anaesthetic ventilator during neuroradiological procedures in general anaesthesia. In order to increase mobility of the patient, two or three lengths of corrugated rubber tubing were used to connect the patient to the ventilator. Blood gas analysis was carried out in 20 patients after ventilation to steady state with both circuits. The respiratory minute volume and fresh gas flow were preset in Bain's (Bain & Spoerel 1975) predictions. No significant difference could be detected in respect to Paco2 or Po2, whether 2 or 3 lengths of tubing were used. Mean values of Paco2 were higher compared with the results of Bain (0.37 kPa s.d. 0.50). It is concluded that this system gives maximum mobility of the patient during the radiological procedure and offers reliable adjustment of Paco2, even in patients with apparent increase of intracranial pressure.

Adolescent↗
PubMed1978

[Naloxone].

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Chemical Phenomena↗
PubMed1978

Flow requirements in the Hafnia modifications of the Mapleson circuits during spontaneous respiration.

The Mapleson A, B, C and D circuits can be changed into non-polluting circuits by employing continuous gas evacuation directly from the circuit, via an ejector flowmeter (Jørgensen 1974); Mapleson A and C circuits with this modification have been described previously as the Hafnia A and C circuits (Christensen 1976, Thomsen & Jørgensen 1976). If evacuation from a closed reservoir is employed, total removal of the expired and surplus gases from the operating theatre is obtained (Jørgensen & Thomsen 1976). There will be resistance to expiration in all the circuits with a relief valve for the discharge of surplus gas. If surplus gas is continuously removed directly from the anaesthetic circuit, the patient breathes in an air compartment at ambient pressure, as long as the removal rate equals the inflow of fresh gas. The relief valve is only included in the circuit to ensure that high pressures do not develop. As in any other circuit, the relief valve remains open except during controlled ventilation. A dumping valve may also be included as a safeguard against low pressures (Jørgensen & Thomsen 1976). The flow requirements of the Hafnia B and D circuits and the corresponding Mapleson circuits have been studied in conscious, spontaneously breathing subjects, and the results are discussed in relation to the flow requirements of other semi-closed system.

Anesthesia, Inhalation↗
PubMed1977

A simple method of monitoring carbon dioxide output in anaesthetized patients.

The mean CO2 output during anaesthesia in paralyzed patients can be monitored by continuous capnographic analysis of the total exhaled gases, the latter being mechanically integrated by pumice canisters. The gas is evacuated from the Hafnia A circuit via an ejector flowmeter. The results are not influenced by the flow rates employed.

Anesthesia↗