Nervenblockaden zur postoperativen Schmerztherapie

Summary

The procedures that can yield adequate postoperative pain relief in the paediatric age group fall basically into two groups: administration of antipyretic medication or opioids, and various local and regional anaesthetic techniques.

The administration of antipyretic analgesics cannot be expected to lead to any satisfactory pain relief after most surgical operations, while following the administration of opioids the danger of respiratory depression must be borne in mind. Following the performance of a large number of surgical interventions in children, it has become apparent that different forms of local and regional anaesthesia are the best options for postoperative pain control. The local anaesthetic of choice in these circumstances is 0.25 (−0.5)% bupivacaine, which has a long duration of action. The maximum dose is 2 mg/kg body weight. The procedures scheduled for postoperative analgesia normally have to be implemented during the general anaesthesia, because the children cannot realistically be expected to cooperate. If they are instituted before the start of the operation it is possible to work with a shallow level of anaesthesia and the amount of narcotic medication required during the operation can also be reduced.

Some local and regional anaesthetic techniques are particularly successful in the paediatric age group, e.g.:

• 1. Penile nerve block

• 2. Block of the ilioinguinal and iliohypogastric nerves

• 3. Infiltration anaesthesia at the operation wound

• 4. Surface anaesthesia

Occasionally a block of the axillary plexus is induced. Peridural anaesthesia should be reserved for a narrow range of very rare indications in children.

For a penile nerve block, both dorsal nerves of the penis are blocked, e.g. with the aid of a 24-G or a 22-G cannula, which is inserted at an angle of about 90° to the skin and advanced until contact with the lower edge of the pubic symphysis is perceived, then withdrawn a little way and again advanced a few millimetres further in the caudal direction. Bupivacaine 0.25–0.5%, 1–4 ml, is then injected.

The ilioinguinal and iliohypogastric nerves are blocked, for example, by inserting a 22-G cannula at a point about 1 cm medial and cranial to the superior anterior iliac spine and advancing the needle in a lateral and caudal direction as far as the inner side of the ilium. The needle is then withdrawn slowly while bupivacaine (0.5 mg/kg body weight) is injected. It is subsequently advanced towards the inguinal canal, i.e. in a caudal and medial direction. Following perforation of the aponeurosis of the obliquus external muscle a further 0.5 mg/kg bupivacaine is injected.

A further option for postoperative pain relief is surface anaesthesia, e.g. with a 10% lidocaine spray. Lidocaine can usefully be sprayed onto the wound following circumcision, for example. This gives effective pain relief for 4–5 h. The 5% EMLA (eutectic mixture of local anaesthetics) cream has a special position among the agents available for surface anaesthesia, effecting long-lasting, satisfactory analgesia of the intact skin within 30–60 min.

Axillary plexus block has a high success rate of 93–94% in children, but is seldom applied. For its implementation in a conscious child some degree of insight and cooperation is necessary, which cannot generally be expected in a child under 8 years of age.

Peridural anaesthesia should not be induced in a child unless very strictly defined indications are present. There is a great deal of controversy about the application of this procedure in children.

In summary, it can be said that local and regional anaesthetic procedures allow highly effective preventive pain therapy without involving the risk of respiratory depression. The simple and low-risk techniques in particular, deserve to be widely used.