Clinics in Anaesthesiology最新文献

SUMMARY

Paracervical and pudendal blocks may be used to provide obstetric analgesia for the first and second stages, respectively. The advantages of these two techniques are: (a) simplicity and ease of application; (b) lack of sedation or drowsiness in the mother; (c) no increase in the duration of the first and second stages, and (d) no decrease in the ability of the mother to bear down in second stage.

The disadvantages of these techniques are: (a) an unpredictable incidence of fetal bradycardia and acidosis with PCB; (b) the risk of maternal toxicity from vascular absorption of the local anaesthetic; (c) the risk of direct injection into the fetus; and (d) a variable degree of successful analgesia with either technique.

The safest local anaesthetic for either type of block is 2-chloroprocaine. Meticulous attention to anatomical landmarks and sterility are important.

Careful monitoring of both the fetus and the mother should be instituted prior to using these blocks and continued until after delivery.

Both paracervical and pudendal nerve blocks should be used in obstetrics only when other forms of analgesia are unavailable or inappropriate.

SUMMARY

This chapter has reviewed four methods of non-pharmacological pain relief for obstetric analgesia (prepared childbirth, acupuncture, hypnosis, and transcutaneous electrical nerve stimulation), presenting a brief explanation of each technique followed by their advantages and disadvantages. Prepared childbirth is by far the most widely practised method of non-pharmacological pain relief in obstetrics. Acupuncture, hypnosis and transcutaneous electrical nerve stimulation are all practised, but on a much more limited scale. The importance of each non-pharmacological method of pain relief will depend upon the patient's wishes and experiences during childbirth, as well as the availability of other modes of producing analgesia for childbirth.

SUMMARY

Bupivacaine is a widely used local anaesthetic of the amino amide class that is relatively free of side-effects if it is administered in an appropriate dosage and in the appropriate anatomical location. Toxic systemic reactions to bupivacaine and other local anaesthetics are largely restricted to the central nervous and cardiovascular systems. The acid-base status of the patient, the time course to peak blood concentration, and the relative potency of the local anaesthetic have correlated with ability to produce CNS symptomatology. The clinical impression that bupivacaine possesses unusual cardiotoxic properties has been demonstrated in laboratory animals. Neonatal effects appear to be minimal. The principles of safe use have been outlined. Bupivacaine is a very useful local anaesthetic in obstetrics and can be used safely, but it is not perfect. The search for new drugs with minimal systemic toxicity and bupivacaine-like efficacy continues.

SUMMARY

It is indicated that the local anaesthetic chloroprocaine is not toxic to neural tissue at the usual clinical concentration. The evident clinical toxicity of the commercial chloroprocaine solution (Nesacaine) is probably due to the drug medium. Three factors are identified and discussed: (a) the presence of the antioxidant sodium bisulphite in significant concentration (0.2%); (b) the profound acidity of the drug solution in the commercial preparation (pH 3.0); and (c) the use of large volumes of anaesthetic solution to increase potency and decrease latency. This overwhelms tissue buffering capacity and may, in addition, lead to vascular limitation to spinal neural tissues. Methods of prevention and treatment are presented.

It should be the aim of clinicians caring for patients with acute respiratory failure to produce the best outcome with the least complications and distress to the patient. Most patients with acute respiratory failure can contribute significantly to their own respiratory homeostasis with carefully applied airway pressure therapy, with the likelihood of reduced barotrauma and improved cardiovascular function. At present, the technique of CPAP + IM V is the method most suited to the above goals and allows independent treatment of the two forms of respiratory failure - hypoxaemia and hypoventilation. It offers flexibility in management of a wide range of conditions. Severe ARDS can be managed using high levels of CPAP, often with little or no mechanical ventilation, and invasive haemodynamic monitoring is frequently unnecessary. CPAP delivered by nasal prongs in adults is a useful new technique.