Dermatomal map.
A high spinal can occur in a number of situations:
The epidural catheter could be inadvertently placed into the subarachnoid (intrathecal) or subdural space. Giving a cautious test dose should enable recognition of an intrathecal catheter but not necessarily a subdural catheter.
A correctly placed epidural catheter can migrate into the intrathecal or subdural position during labour.
An excess dose of local anaesthetic can be given via the intrathecal or epidural route
The patient can be positioned incorrectly, such as steep head-down positioning after administration of a hyperbaric solution.
The initial signs and symptoms usually occur within a few minutes of injection, although the onset can be delayed. They include nausea, anxiety, dysaesthesia or paralysis of upper limbs, hypotension, dyspnoea, difficulty coughing and clearing secretions and a high sensory block. Progression can lead to bradycardia, aspiration of gastric contents, cranial nerve involvement (such as a Horner’s syndrome and altered speech), loss of consciousness, apnoea and cardiac arrest.
It is important to consider other potential causes and differential diagnoses. Massive thromboembolism, amniotic fluid embolism, local anaesthetic toxicity and cerebrovascular event could all present similarly and need prompt recognition and treatment.
Initial management aims to support the patient and limit the progression of the block. The patient should be reassured and the block level checked. Steep head-up positioning may help reduce further spread. Hypotension should be treated with an increase in IV fluid rate, leg elevation and boluses of vasopressor such as phenylephrine or metaraminol. Bradycardia should be treated with an anticholinergic. High-flow oxygen should be started. If the block progresses or the patient becomes compromised, a RSI should be performed. Appropriate reassurance should be given throughout and an induction agent should be used to minimize the risk of awareness. Once the airway is secure, ventilation and cardiovascular support should continue until return of adequate respiratory function can be demonstrated. This may warrant admission to ICU for ventilatory support.
Management of epidural top-up
You are called to anaesthetize a patient for a category 2 Caesarean section. She has an epidural that the midwife says has been working well.
How are you going to proceed?
As with any case you need to assess the patient for yourself. Review the anaesthetic chart, history and ask about the effectiveness of the epidural.
The patient may give you a range of answers but these will fall broadly into three categories:
1. Epidural has been persistently problematic. Impression: top-up probably not going to be effective. Plan: spinal or general anaesthetic.
2. The epidural has caused concern at some point but is now working well. Plan: if the epidural was straightforward consider offering the patient a spinal anaesthetic. If regional felt to be difficult then begin top-up but if not effective quickly, offer spinal.
3. The epidural has worked well since it was sited. Impression: top-up likely to be effective. Plan: proceed with top-up.
You decide to top up the epidural. How are you going to do this?
Where?
The top-up can be commenced in the patient’s room prior to transfer to theatre. It is essential that the patient can be monitored in the room before you give the top-up (blood pressure, heart rate and SpO2) and that you remain with them once you have started it. The alternative is to wait until arrival in theatre before administering any local anaesthetic.
How?
Start by checking the existing block; otherwise it will be difficult to know if the top-up is effective.
You should always check what the recommended top-up mixture is for your hospital. The two main options are:
1. 0.5% bupivacaine
2. 2% lidocaine – usually administered as part of a ‘quick mix’.
It is generally advisable to start with a 3–5 ml ‘test dose’ of either mix in case there has been any intrathecal catheter migration. Subsequent doses will depend on the block level, the urgency of the surgery and any medical conditions in the patient (e.g. cardiac problems). Generally, doses are 3–5 ml and spaced at least 5 minutes apart but if the block is below the umbilicus and the surgery is urgent then the next dose can be 10 ml.
Lidocaine as part of a ‘quick mix’ has a quicker onset of action than 0.5% bupivacaine.
A suggested ‘quick mix’ recipe is; 19 ml 2% lidocaine, 1 ml 8.4% sodium bicarbonate (increases pH, which promotes passage of local anaesthetic across the neuronal membrane), 0.1 ml 1:1000 adrenaline (increases speed of onset, prolongs effects, reduced peak local anaesthetic blood levels).
Opiates can also be given to improve the block. Either fentanyl 100 mcg or diamorphine 3 mg. Fentanyl acts quicker but diamorphine lasts longer. If the block is adequate then generally wait until after delivery and give diamorphine because of the hypothetical risk of respiratory depression on the neonate.
The block should be checked after each top-up to help guide further doses. It is important to check for sensory and motor block. Sensory block is generally assessed with cold and/or light touch. A level of T4 to cold and T5 to light touch is required for Caesarean section.
Motor block can be assessed using the Bromage score (see Table 11.2).
The Bromage Motor Block Scale
| Degree of motor block | Criteria | Score |
|---|---|---|
| No block | Full flexion knees and feet | 0 |
| Partial block | Just able to flex knees plus full flexion feet | 1 |
| Almost complete | Unable to flex knees, some flexion feet | 2 |
| Complete block | Unable to move legs or feet | 3 |
An epidural top-up may provide adequate anaesthesia without the complete motor block seen with a spinal anaesthetic.
Further reading
Complications of obstetric regional anaesthesia: management of post-dural puncture headache
A 32-year-old primiparous lady had a very difficult insertion of spinal anaesthetic for trial of forceps delivery 3 days ago. She is still complaining of a headache in the frontal region, worse on sitting up, especially in the evenings. She has been taking regular paracetamol, codeine phosphate and ibuprofen in addition to three cups of coffee per day for the past 2 days.
What would you do next?
a) Prescribe oral theophylline
b) Arrange for CT head scan to exclude other intracranial pathology
d) Administer a 5-HT1 agonist
Answer: c)
There are many causes of headaches in newly postnatal women, and it is important to take a very careful history and examination. The 2014 Saving Mothers’ Lives report highlights the importance of including subdural haematoma and cerebral venous sinus thrombosis in the differential. Other differentials are: non-specific/tension headache; migraine (unusual as a first presentation); hypertension/pre-eclampsia; posterior reversible leucoencephalopathy syndrome; subarachnoid haemorrhage; space occupying lesions; cerebral infarction or ischaemia; sinusitis and meningitis.
From the history given post-dural puncture headache (PDPH) is the most likely cause. A CT head scan to exclude other intracranial pathology is beneficial if the diagnosis of PDPH is less certain. Treatment options are conservative, pharmacological or epidural blood patch (EBP).
The natural course of PDPH is that it usually resolves over 7–14 days. However, it may take weeks, and the demands of being a new mother often mean that women are keen to be treated sooner. Simple treatments should be encouraged: paracetamol, dihydrocodeine (with laxatives), NSAIDs, bed rest and hydration. Caffeine may help via its cerebral vasoconstrictor effects, but there is no strong evidence for this. The recommended dose is 300 mg per day (a cup of coffee contains about 100 mg).
Epidural blood patch is the most effective treatment (supported by a Cochrane review) and it should be performed 24–48 hours after the dural puncture with conservative management in the interim. Higher failure rates are reported when performed within 24 hours. Contraindications to EBP include sepsis (check that the patient is afebrile first), coagulopathy and patient refusal. An experienced anaesthetist should perform the EBP at the same space or space below, and the venepuncturist must maintain full aseptic conditions. Ten to thirty millilitres (usually 20 ml) of blood is used and you should stop injecting when the patient complains of pain or radicular symptoms, or you have given 30 ml. The success rate for first-time blood patch is reported to be at least 50%. The patient may experience backache after EBP and should rest for 1–2 hours before resuming non-strenuous activities.
Subcutaneous 5-HT1 agonists (e.g. sumatriptan) and oral theophylline both cause cerebral vasoconstriction and have been used but with less success than an EBP. Synthetic ACTH (Synacthen) has also been reported to be effective for treating PDPH. There is no convincing evidence from randomized controlled trials to support these.
However the PDPH is managed, the MBRRACE report recommends that ‘best practice…should include outpatient follow up and notification of the woman’s GP’. The Royal College of Anaesthetists (RCoA) and Obstetric Anaesthetists Association (OAA) have produced a patient information leaflet for PDPH.
Further reading
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