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 (J ørgensen 1974); Mapleson A and C circuits with this modification have been described previously as the Hafnia A and C circuits (C hristensen 1976, T homsen & J ørgensen 1976). If evacuation from a closed reservoir is employed, total removal of the expired and surplus gases from the operating theatre is obtained (J ørgensen & T homsen 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 directlyfrom 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 (J ørgensen & T homsen 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 systems.
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.
Summary A definite relationship between the use of contaminated anaesthetic equipment and subsequent pulmonary infection remains to be established. There is however indirect and circumstantial evidence suggesting that cross‐infection may occur, and further an increased susceptibility of surgical patients to pulmonary infections has been demonstrated. Decontamination should be recommended before the equipment is re‐used. Pasteurisation may prove sufficient and this can be obtained employing a specially designed dish‐washing machine.
The treatment of vasospasm during ergotism has been difficult and unconvincing.1 2 3 A combination of hyperbaric oxygen and sympathetic blockade by means of continuous epidural anesthesia has been claimed to have some effect in limiting the ischemic peripheral gangrene induced by ergotism.4 Carliner and his co-workers1 reported a case of ergotism with extreme peripheral ischemia successfully and rapidly treated with continuous infusion of sodium nitroprusside. The two cases of ergotism presented below were treated with sodium nitroprusside in combination with continuous epidural anesthesia.Case ReportsCase 1 (Fig. 1). A 58-kg 44-year-old woman with a moderate intake of ergotamine owing to . . .
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.
