Clinics in Anaesthesiology最新文献

SUMMARY

Nearly all obstetric drugs may require a change in anaesthetic care. Anticholinergics increase the threat of aspiration. Sedatives, tranquillizers and narcotics all impair consent, potentially depress the mother and infant, and increase the risk of general and regional anaesthesia. Magnesium sulphate decreases acetylcholine release at the neuromuscular junction, reduces end-plate sensitivity and muscle membrane excitability, and potentiates depolarizing and non-depolarizing muscle relaxants. Reduced renal function during pregnancy-induced hypertension increases the possibility of magnesium toxicity. Placental transfer and fetal toxicity may also occur. Oxytocin is a potent vasodilator and can cause severe hypotension, while ergometrine produces direct vasoconstriction and may cause severe hypertension, β-Agonists used for tocolysis lower the serum potassium, produce vasodilation, increase the heart rate and increase myocardial irritability. Caution should be used when inducing both regional and general anaesthesia. Importantly, these drugs may also generate pulmonary oedema in previously healthy parturients. The aetiology of pulmonary oedema remains unknown, but all cardiac complaints in patients on β-adrenergic therapy must be considered real until proved to be otherwise.

Anaesthetic involvement in complicated obstetrics is increasing at a rapid rate. The anaesthesiologist participating in perinatal care must be educated in the pharmacology of obstetric as well as anaesthetic drugs. Only then can the parturient fully and safely utilize the skill and expertise the anaesthesiologist can bring to the obstetric suite.

SUMMARY

The stimulus for the development of ‘failed intubation drill’ was a maternal death. The mother died from the consequences of silent pulmonary acid aspiration associated with a difficult endotracheal intubation. It occurred at a time when regional anaesthesia was rarely used for caesarean section in the locality. The purpose of the drill (or protocol) was to outline a safe plan of action following failure to intubate the trachea in a mother anaesthetized for an obstetric operation. It was necessary to take steps to effect oxygenation without aspiration. The details for enabling a safe changeover to a general anaesthetic without an endotracheal tube were given. The plan recognized that oxygenation would be difficult in some patients. Such cases were to be allowed to wake up before a decision on an alternative anaesthesia could be made.

The maintenance of cricoid pressure and placing the patient in the left lateral head-down posture remains essential to the protocol.

This chapter deals with some causes of unexpected difficulty with visualization of the larynx. Methods of improving the chance of successful intubation in problem cases are given. The factors which make intermittent positive pressure ventilation by face-mask difficult, or impossible, are reviewed, and the ways of clearing an obstructed airway when intubation has failed are outlined. The authors attach importance to the use of the triple airway manoeuvre, and forward displacement of the larynx by endo-oesophageal intubation in some cases. Where there is complete inability to ventilate by face-mask following a failed intubation, transtracheal oxygenation via a catheter inserted through the cricothyroid membrane is effective and life-saving.

A failed intubation protocol is presented.

SUMMARY

Spinal anaesthesia continues to be a valuable technique in obstetrics as it is simple to perform and highly reliable. By avoiding hypotension with acute hydration, left uterine déplacement and intravenous ephedrine, good maternal and neonatal outcome can be expected.

SUMMARY

A general critique of the large body of research on the neonatal behavioural effects of obstetric medication is given to provide the clinician with a better framework within which to conceptualize the problem. Study designs are examined to illustrate limitations in the interpretations of the findings. Investigators often fail to consider principles of perinatal pharmacology when researching drug effects and do not include control samples of infants of unmedicated deliveries. The effects of other perinatal variables which may interact with drug effects are generally ignored. Furthermore, many of the dependent measures of behaviour which are assessed do not adequately conceptualize neonatal behavioural functioning. A description of the Brazelton Neonatal Behavioral Assessment Scale is given as an example of a measure which examines neonatal behavioural functioning within an interactive setting. It is recommended that changes in behaviours over time be investigated to assess drug effects on the infant's recovery from labour and delivery. A recent study which investigated the effects of bupivacaine epidural anaesthesia and obstetric variables that alter its rate of placental transfer is discussed. Findings showed synergistic effects of bupivacaine and the perinatal variables on neonatal behavioural functioning and recovery from labour and delivery up to one month of age, but not at one year.

The chapter illustrates that research findings do not support a simple, linear picture of drug effects on behaviour. A systems approach is suggested, in which neonatal behavioural functioning and parent-infant interaction are viewed in the light of the interaction of maternal characteristics that influence medication decisions, the medication, and maternal and fetal conditions which alter its placental transfer. Ultimately, it is these systems that affect the infant's developmental outcome.