What I wish I knew about spinals and epidurals as an O&G Resident

What I wish I knew about spinals and epidurals as an O&G Resident

Nov 10, 2020 0
anaesthetics,o&g,onthepods

In this podcast, Becky Taylor and Blake Kesby discuss spinals and epidurals, what they are, what the difference is, and how to manage patients going into labour requesting an epidural. Becky and Blake discuss when you might encourage spinals and epidurals, considerations to keep in mind, anaesthetic contraindications, and risks. They also cover an approach to postdural puncture headache (PDPH).

Summary Writers:  Becky Taylor and Jane McDonnell

Script Writer:  Jane McDonnell

Editor:  Blake Kesby

Interviewer:  Becky Taylor

Interviewee:  Blake Kesby

About Dr Rebecca Taylor

Rebecca (Becky) Taylor is a 5th year O&G trainee. Originally hailing from the UK, she trained at the University of Edinburgh where she also completed her internship and residency, before moving to Australia. She undertook her basic O&G training at Royal Prince Alfred Hospital in Sydney and is currently undertaking a six-month fertility fellowship at Westmead Hospital. When Becky’s not knee-deep in amniotic fluid she is a keen swimmer and free diver, a terrible cook and married to an anaesthetist she met at a Cat One Caesarean.

About Dr Blake Kesby

Blake Kesby is a Consultant Anaesthetist at Royal North Shore Hospital in Sydney, Australia. He has a special interest in medical education, particularly simulation-based training. When he’s not putting people to sleep he’s a keen free diver, an excellent cook, and married to the O&G Reg who roped him into this podcast.

What I wish I knew as about spinals and epidurals as an O&G Resident

With Dr Becky Taylor, Obstetrics & Gynaecology Fellow based in Sydney and Dr Blake Kesby, Consultant Anaesthetist at Royal North Shore Hospital.

Case

A 30-year-old primigravid woman, Annie, is in spontaneous labour at 39 weeks’ gestation. Her last vaginal examination was performed 3 hours ago and she was 4cm dilated. She has been using nitrous gas with good effect but now the pain is increasing and she is requesting an epidural. She has a pre-pregnancy BMI of 30 and no other medical issues.

  • A spinal or intrathecal injection involves using a very small needle, preferably with a pencil point tip, and inserting it into the intrathecal space, at a level below the termination of the spinal cord or conus medullaris which is at L1/2 in most people.
    • Spinals are normally inserted at L3/L4 or below, to minimise any risk to the cord.
    • When reaching the intrathecal space, we see flow back of cerebrospinal fluid (CSF), at which time we inject a mixture of local anaesthetic and sometimes opioids. The needle is then removed.
    • It is a single shot technique, and only lasts for the duration of the drugs injected (normally a few hours).
  • An EDB involves placing a catheter into the epidural space, a potential space between the ligamentum flavum, and the dura.
    • We do this using a loss of resistance technique with a Touhy needle, which is much larger than the spinal needles we use (to help find the epidural space and to insert a catheter through).
    • Unlike with a spinal, we do not want to puncture the dura or enter the intrathecal space.
    • When we reach the epidural space, a very small catheter is inserted through the large needle into the epidural space.
    • Because the nerve roots run through the epidural space, they become blocked when we inject local anaesthetic agents and opioids through the catheter.
  • Due to their differences, spinals and EDBs are used for different obstetric needs.
    • Spinals have a very fast onset, and produce a dense, reliable block 🡪 ideal for Caesarean sections.
    • Spinals also have a greater effect on the patient’s haemodynamics due to sympathetic blockade.
    • Due to their single shot nature, spinals are not appropriate for labour analgesia, as they only last a few hours.
    • EDBs are not as fast in onset, but can be infused through the catheter over a long period of time, making them suited to women in labour.
    • EDBs can also be used for a Caesarean section by injecting a higher concentration local anaesthetic agent, to achieve a dense, higher block for surgery.
    • Because lower concentrations of solutions are used to top up labor EDBs, patients are more haemodynamically stable and therefore they can be inserted on the birthing unit.
  • There are also combined spinal/EDBs – these are used for Caesareans which may take longer than expected (e.g. previous major intra-abdominal surgery or morbidly obese).
  • History
    • Haematological issues – e.g. gestational thrombocytopenia, pre-eclampsia, recent anticoagulants or antiplatelets.
    • Infection – fevers or systemic infection that hasn’t been treated.
    • Back issues – spinal surgery (may distort the anatomy of the epidural space), spina bifida, scoliosis.
    • Progression in labour – the obstetric team should have done a recent vaginal examination.
  • Investigations
    • Platelet count should be >80 – if the platelet count is lower, the risk of subdural or epidural haematoma is higher.
  • Consider how dilated the cervix is – if the woman is fully dilated and progressing quickly in the second stage, she may deliver her baby before the EDB is inserted or established. However, full dilatation is not a contraindication to an EDB. If there is slow progress in the second stage, it may be an optimal time to allow augmentation or an assisted delivery.
  • Anaesthetic indications
    • Conditions in which the strain of labour may worsen pre-existing conditions (e.g. cardiac conditions).
    • Obesity – can be more challenging in an emergency setting so having an elective EDB placed earlier may be prudent.
  • Obstetric indications
    • Twin pregnancy – in the event that an internal podalic version needs to be performed.
    • If women have gestational hypertension or pre-eclampsia, we often see a reduction in blood pressure following an EDB placement.
  • Absolute
    • Patient refusal
    • Allergy (true amide local anaesthetic allergy is very rare)
    • Local infection
    • Uncorrected hypovolaemia
    • Coagulopathy – guidelines suggest platelets > 75 and INR <1.4 does not increase the risk on neuroaxial technique.
  • Relative
    • Untreated systemic infection – if this is being treated with antibiotics, the risk of ‘seeding’ infection into the epidural space is minimal.
    • Cardiac disease – valvular stenosis and cardiomyopathy – extreme care must be taken to avoid changes in pre- and after-load. Intrathecal opioid without local anaesthetic may be advantageous for these patients.
  • Dural puncture 1:100 – 1:200
  • Post-dural puncture headache occurs in 50-70%
  • Subdural block 1:1000
  • Total spinal 1:25 000
  • Epidural haematoma risk is 1:500 000 in obstetric population
  • Epidural abscess 1:110 000
  • Temporary nerve injury 1:5000
  • Persistent or permanent neurological injury 1:20 000 – 1:1000 000
  • Hypotension due to sympathetic blockade and/or reduced uterine relaxation as there is less pain-induced adrenaline circulating which acts on B2 receptors on the uterus.
    • Treat with IV fluid bolus/ephedrine.
    • Ephedrine increases blood pressure and also relaxes the uterus.
  • Drugs used for EDB and spinals are similar.
  • For EDB
    • Aim is analgesia, not motor block. Motor and proprioception nerve fibers are much larger than pain or temperature fibers. Low concentration local anaesthetic agents preferentially block the smaller pain and temperature fibers whilst preserving the larger Motor and proprioception fibers.
    • Like to cover up to level T10 (around the umbilicus).
    • Ropivacaine is used as it is a long-acting agent. We normally use a dilute concentration of 0.1 or 0.2 percent. Patients are then given a pump which will provide a set dose per unit time, but also allow a pre-programed patient-initiated dose if required.
    • Opiates are also used – most commonly, fentanyl, which reduces the amount of local anaesthetic required and speeds up the establishment of the epidural.
  • Testing
    • Pain fibers are approximately the same size as temperature fibers, and therefore are blocked at the same time by local anaesthetic agents. To test the adequacy of the block, we use ice to determine which dermatomes have loss of sensation to temperature, and this tells us at what level the block is working.
    • Ability to move legs – some institutions are able to perform ‘walking epidurals’.
    • Importantly, patients will still be able to feel pressure and movement in Caesarean sections (pushing, pulling) but should not have pain..

Case: Annie’s epidural is working well. The obstetric registrar is asked to review her 4 hours later and she remains 4cm dilated. Her CTG demonstrates recurrent complicated variable decelerations and the decision is made to proceed to an emergency Caesarean section.

  • Options are:
    • Epidural ‘top up’ to make it adequate for performing surgery, or
    • Spinal anaesthetic (if EDB is not working well), or
    • General anaesthetic if the EDB is not working there is inadequate time to perform a spinal.
    • NB: We need a higher and denser block for a Caesarean section, up to about T3/4 level.

Case: Annie proceeds to an uncomplicated Caesarean section and delivers a healthy baby girl. She is reviewed the following day and complains of a headache which doesn’t resolve with paracetamol.

  • Headaches are very common postpartum – approximately 30% of women get a headache in this period.
  • Consider usual things – tiredness, dehydration.
  • Consider postpartum pre-eclampsia (examine RUQ tenderness, reflexes, clonus).
  • Meningitis – look for signs and symptoms.
  • Look for any neurological deficits.
  • Post dural puncture headache (PDPH)
    • With every spinal block, the dura is punctured but this is with a very small needle so the risk of a PDPH is 1:100 to 1:200
    • If we inadvertently puncture the dura with an epidural, because the needle is much larger, there is more likely to be a larger leak of CSF.
    • The leakage of CSF changes the hydrostatic pressure in the spinal column and this is why patients get ‘postural headaches’ – no headache or mild symptoms on lying, and headache recurs on sitting or standing in the frontal region, may be associated with nausea, vomiting, photophobia or visual disturbance.
    • Approximately 66% PDPH will occur within 48 hours and 90% within 72 hours.
  • Options for management are: conservative management (analgesia) or a blood patch.
  • Usually try a period of 24-48 hours conservative management (a clot will form and the process will self-resolve) with paracetamol and NSAIDs +/- caffeine therapy +/- opiates.
  • Most of the time the headache will resolve within 2 weeks.
  • If the headache is severe, we can perform a blood patch.
    • Blood patch is done in theatre under sterile conditions.
    • We obtain some blood from the patient’s arm and then another epidural is performed, except this time, the blood is injected into the epidural space.
    • The aim is that this blood will clot off the hole that is causing the CSF leak.
    • Good relief obtained in 50-80% time.
    • Some patients will require a second blood patch.
  • If calling for an EDB from the ward, try to have the following arranged:
    • Succinct past medical/antenatal history
    • Progress in labour
    • Allergies
    • FBC (especially platelet count)
    • An IVC in situ (for pre-loading with IV fluids)

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Tags: #Anaesthetics,#analgesia,#Caesarean Section,#catheter,#cerebrospinal fluid,#dural puncture,#EDB,#epidural,#epidural abscess,#epidural block,#epidural haematoma,#epidurals,#fentanyl,#fetal bradycardia,#gestational thrombocytopenia,#Gynaecology,#intrathecal administration,#intrathecal space,#nerve injury,#O&G,#O&G resident,#obstetrics,#pain management,#PDPH,#platelet count,#pre-eclampsia,#pregnancy,#pregnant patient,#primigravid,#ropivacaine,#spinal block,#spinals,#spontaneous labour,#subdural block,#subdural haematoma,#uterus

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