The use of local anaesthetic in orthopaedic medicine
For injections and infiltrations lidocaine and procaine are used.
The anaesthetizing effect of procaine starts after 5-10 min. and lasts about 45 min. The maximal quantity should not exceed 50 ml in a 0.5 % concentration.
Procaine is used in concentrations of 0.5 % and 2 %.
The anaesthetizing effect starts after 2 min. and lasts about 60 min.
Lidocaine is used in a 2 % concentration.
- Procaine 0.5 % is used as a diagnostic aid, but also therapeutically in cases of chronic bursitis, muscle belly lesions and in epidural local anaesthesia.
- Procaine 2 % is used to dissolve calcium deposits in tendons or bursae, and in case of a sinuvertebral nerve block.
- Lidocaine 2 % without ADR is used as a diagnostic aid, and for superficial anaesthesia of the skin in epidural local anaesthesia.
When using local anaesthetics, both a toxic and an allergic reaction can occur.
1. Toxic reaction
This reaction presents mainly when the maximal dose is exceeded or in intravenous application of the anaesthetic.
Either a stimulation or a depression of the central nervous system occurs, in conjunction or not with a cardiovascular suppression.
Next to an immediate reaction, also a delayed one is possible ; it occurs 5-30 min. after the injection. Therefore, after an epidural local anaesthesia, the patient must be kept under observation for another 30 min.
2. Allergic reaction
Its frequency, when using procaine, is 1/50.000.
Besides the general urticarian reaction, a serious anaphylactic shock can occur, fortunately only very exceptionally with respiratory and cardiac arrest.
Next to an immediate reaction, also a delayed one is possible, as long as 30 min. after the application.
Previous interrogation of the patient as to the presence of an allergy can help avoiding allergic reactions ; in case of doubt, a small intradermal application can be considered.