Dltral tap. The incidence should be less than 0.5% in experienced hands. It usually occurs with the needle rather than the catheter and is immediately obvious because of the free flow of CSF. Puncture of the dura with a large epidural needle leads to a high incidence of headache. If this occurs, epidural block should be produced at an adjacent space, and 0.9% saline 40 ml hH should be infused epidurally for 36 h after surgery or labour to reduce the likelihood of headache. Simple analgesics may suffice if headache occurs; if not, an epidural blood patch should be performed.
Table 43.5 Guidelines for the insertion and removal of epidural catheters in association with low-molecular weight heparins (LMWH)
1. Patients who need DVT prophylaxis before theatre, should receive I.MWH the day before at approximately IK.00 h.
2. LMWH should not be given on the day of surgery — this allows 12 h before catheter placement; although the LMWH is providing DVT prophylaxis at Lhis time, plasma concentrations are below peak activity and therefore less likely to create a problem,
3. LMWH may be given 2 h after placement of an epidural catheter.
4 The epidural catheter should be removed 12 h after the last dose of LWMH and the next dose cannot be given until 2 h have elapsed.
5. Antiplatelet drugs and anticoagulant drugs should not be used concurrently with LMWH.
6. The smallest effective dose of LMWH should be used.
7. Patients should have regular (every 4 h I neurological examination after removal of the epidural catheter. This should include sensation, power and reflexes.
8- in cases of traumatic or repeated epidural puncture, administration of LMWH should be delayed for more dian 24 h; an alternative method of DVT prophylaxis should be used.
9. Epidural mixtures should contain a low concentration of bupivacaine so that motor function may be assessed.
10. If the patient develops a neurological abnormality either during epidural infusion or writhin 48 h of epidural catheter removal, an urgent MRI scan is required and a neurosurgical opinion should be obtained.
Accidental total spinal anaesthesia (see below) is rare because the dural tap is usually obvious.
Total spinal anaesthesia. This may occur if the large volume of solution used for epidural anaesthesia is injected into the subarachnoid space. The consequences may be:
• profound hypotension
• apnoea, unconsciousness and dilated pupils secondary to local anaesthetic action on the brain stem.
Paralysis of the legs should alert the physician to the possibility of subarachnoid injection. When using a test dose, motor function should be tested by asking the patient to raise the whole leg and not merely to wiggle the toes; movement of the toes may not be abolished for 20 min after SAB, if at all. It should be noted that relatively large volumes of local anaesthetic solution, e.g. 10 ml of bupivacaine 0.25%, may be injected into the subarachnoid space without total spinal anaesthesia occurring.
Provided that skilled resuscitation is undertaken rapidly, a total spinal should be followed by complete recovery. Appropriate personnel and equipment should be present before epidural analgesia is undertaken and whenever top-up injections are administered.
Massive epidural block and subdural block. A very high block may occur in the absence of subarachnoid injection. This may be associated with Horner's syndrome. Other complications include:
• intravenous toxicity (see Ch. 15)
• urinary retention
• nausea/vomiting - this may result from hypotension or visceral manipulation in the awake patient.
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