Search

During pregnancy there is a fall in functional residual capacity and expiratory reserve volume. The point of airway closure in relation to vital capacity and the expiratory reserve volume was determined in 11 post-partum patients who had previously been studied during pregnancy. The lung volume at which airway closure occurred in pregnancy and the post-partum period did not change in relation to the vital capacity whereas the expiratory reserve volume did, so that airway closure became imminent in the pregnant women during tidal ventilation, especially whilst in the suping position. The significance of this alteration in pulmonary function to obstetric anaesthesia is discussed.

SUMMARY Recently introduced plastic swivel connectors (both autoclavable and disposable) were examined under laboratory conditions for gas leakage. The leak from the autoclavable connectors before autoclaving nearly always exceeded 5% Although this leak was diminished after autoclaving, the swivelling property was greatly decreased. The position of maximal leakage was found to vary with the position of the connector on the tracheal or tracheostomy tube adaptor. The magnitude of the leaks obtained varied, only the disposable connectors complying with our own criteria. Comparison of the plastic connectors was made with one type of metal swivel connector which was also found to be acceptable for clinical use.

Summary The effectiveness in clinical practice of conventional analgesia, with pethidine and 50 per cent nitrous oxide in oxygen (Entonox) has been studied in 663 consecutive patients. More than 75 per cent of mothers stated that they had obtained little or no pain relief from pethidine in the manner in which it was administered. In comparison, nearly half the patients who received Entonox had satisfactory analgesia and the incidence of acceptable pain relief with both agents was unrelated to parity. The number of patients receiving satisfactory analgesia was disturbingly low.

Measurements of closing volume have been made in 20 women between the 36th and 40th weeks of pregnancy. The patients were studied in the erect and supine positions and the point of airway closure was related to functional residual capacity. The results show that airway closure occurred during tidal ventilation in 10 patients in the erect position and in six patients in the supine position. These results may explain the variation found in maternal arterial oxygen tension during pregnancy.

Anaesthesia was induced with equipotent doses of either thiopentone or methohexitone in 127 women undergoing Caesarean section. They divided into three groups: those having normal placental function, those with an undefinable degree of placental insufficiency, and emergencies. There was no clinical or biochemical difference in the neonates following induction of anaesthesia with either thiopentone or methohexitone. The clinical condition of neonates born of mothers with normal placental function was superior to the other two groups.

A study was undertaken in twenty-eight patients to compare the effects of the supplementation of nitrous oxide and oxygen anaesthesia with either 0.5--1.0% halothane or 50 microgram fentanyl/kg on the metabolic and hormonal response to gynaecological surgery. The results showed that the increases in blood glucose, plasma cortisol and growth hormone concentrations observed in the halothane group of patients were abolished in those who received fentanyl. It is postulated that the ability of large doses of fentanyl to inhibit the cortisol and growth hormone response to surgery may be of value in ameliorating the catabolic response to trauma.

The effect of epidural blockade on the metabolic and hormonal responses to pelvic surgery was investigated in 14 female patients. Central venous blood samples were collected every 30 minutes and analysed for free fatty acids, glycerol, beta-hydroxybutyrate, acetoacetate, glucose, lactate, pyruvate, cortisol and growth hormone concentrations. There was no change in fat and glucose metabolism except for a transient decrease in lipolysis after 30 minutes of surgery. Cortisol and growth hormone values were significantly increased (p less than 0.01) after 60 minutes. A small but statistically significant increase in blood lactate concentration was observed (p less than 0.01) and the concept of a "metabolic V/Q" abnormality is postulated to explain the lacticacidaemia.

Etomidate, a new intravenous hypnotic agent, significantly lowered the mean intraocular pressure (IOP) of fifty patients within 30 s of an intravenous injection from 15.7 to 9.5 mmHg. This effect was present even during the administration (to twenty patients) of low doses (0.25 mg/kg) when the mean reduction was from 15.6 to 7.6 mmHg. The reduction in IOP was unaffected by the presence of muscle movement. Low frequency pendular nystagmus was observed in five patients.

The induction characteristics of etomidate, a new i.v. hypnotic agent, were studied in 400 patients. Two hundred were premedicated with atropine and anaesthesia was induced with 0.2, 0.25, 0.3 or 0.35 mg/kg of etomidate. The remainder received one of four standard premedications and anaesthesia was induced with etomidate 0.3 mg/kg. Involuntary muscle movements occurred in more than 60% of patients receiving atropine alone. The frequency was reduced in the second group, but remained unacceptable in over 8% of patients. The incidence of other excitatory phenomena, such as cough and hiccup, was 10% approximately. Cardiovascular changes were minimal and no serious allergic phenomena were observed. Nausea and vomiting occurred after surgery in up to 30% of patients and was unrelated to the dose of etomidate or to premedication. Pain on injection occurred in up to 80% of patients when the drug was injected into small peripheral veins and occurred in more than % when using more proximal veins

Surfactant depletion was induced by lung lavage in 10 rabbits. Ascending aortic blood flow was measured at normocapnia at 0, 5 and 10 cm H2O PEEP before and after lavage. Aortic blood flow was reduced by PEEP, by a maximum of 24% before lavage and 60% after lavage. It was concluded that, although adequate arterial oxygenation can be maintained with 10 cm H2O PEEP in surfactant-depleted rabbit's lungs, the circulatory impairment may result in inadequate oxygen delivery.

Ninety-two patients who presented for outpatient dental extractions received methohexitone (1.5 mg . kg-1, 46 patients) or etomidate (0.3 mg . kg-1, 23 patients and 0.2 mg . kg-1, 23 patients). The induction characteristics of both drugs such as pain on injection, involuntary muscle movements and respiratory difficulties were comparable and the theoretical disadvantages of etomidate for dental anaesthetics did not prove troublesome in practice. Muscle movements did not interfere with the dentists' manipulations and pain on injection into veins of the antecubital fossa did not occur. The duration of operation for up to four extractions was three minutes and, following induction, anaesthesia was maintained with nitrous oxide, oxygen and halothane. Recovery was assessed by grading consciousness, airway control and motor activity. All the patients could maintain their airways one minute after the end of operation. The incidence of nausea and vomiting was significantly greater in the etomidate group.