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Spinal +/- epidural anaesthesia

Overview

Spinal and epidural anaesthesia are types of local anaesthesia that are used to numb (block sensation) specific regions of the body. Both these anaesthesia techniques act by targeting the nerves near the spinal cord and are generally used for surgical procedures in the lower body, including childbirth, urological procedures, and orthopaedic (bone) surgeries. Though these two types of anaesthesia have certain similarities, they differ in terms of technique, onset, and applications.

As spinal anaesthesia causes profound loss of sensation (no pain felt) and muscle movement (inability to move the affected area) and reduction in the activity of the sympathetic nervous system (part of the nervous system that controls blood pressure, heart rate, and blood vessel constriction), it is effective for lower body procedures like orthopaedic surgeries (e.g., hip and knee replacement), abdominal surgeries (e.g., caesarean section and hernia repair surgery), and urological procedures (bladder surgery). In contrast, epidural anaesthesia provides pain relief without substantial loss of muscle movement (epidural analgesia, i.e., no muscle paralysis), and is therefore the anaesthesia of choice during labour where pain relief (labour pain management) is required without affecting consciousness. Epidural anaesthesia can be used in combination with general anaesthesia to improve pain control and reduce the dependence on systemic opioids (a class of pain-relieving medications that is often used during surgery—as part of the anaesthesia management plan—whose use in addition to causing addiction, is associated with side effects (like respiratory depression and gastrointestinal issues) and long-term complications.

Both spinal and epidural anaesthesia improve patient outcomes by providing effective pain relief and reducing the recovery time. This makes them safer and more targeted alternatives to general anaesthesia. I have enumerated a few benefits of these anaesthesia techniques blow.

  • Avoidance of risks associated with general anaesthesia: Both spinal and epidural anaesthesia are associated with low risk of nausea, vomiting, sore throat, and cognitive dysfunction (all of which are risks associated with general anaesthesia).
  • Enhanced safety due to the provision of patients remaining conscious during surgery: Conscious patients do not require airway management. This reduces the risk of complications like aspiration, respiratory depression, or adverse reactions to general anaesthetics.
  • Effective pain control: These techniques provide excellent pain relief, especially in the lower half of the body and are therefore considered the optimal methods of anaesthesia in that region, hence their use to ensure numbness and pain relief during labour and childbirth (labour pain management) and surgeries in the region below the chest.
  • Minimal systemic effects: As these techniques avoid the use of systemic (affecting the entire body) sedatives or narcotics, they do not cause drowsiness or respiratory depression.
  • Improved postoperative recovery: Owing to improved blood flow in patients undergoing these types of anaesthesia, patients are at a lower risk of developing complications like deep vein thrombosis (DVT) or pulmonary embolism. Additionally, these techniques are associated with faster return of gastrointestinal function compared to general anaesthesia. All of these aspects result in early post-operative mobilization and recovery.
  • Haemodynamic stability: These techniques reduce the surgical stress response, which leads to better blood pressure control during surgery (and hence smoother surgery).
  • Cancer pain relief: Local anaesthetics or opioid medications can be delivered into the epidural space (epidural) or directly into the cerebrospinal fluid (CSF; spinal block) to provide pain relief for advanced cancers that cause widespread pain in the lower body or abdomen. These strategies are often used in palliative care (aimed at improving the quality-of-life of individuals with life-threatening diseases) settings for continuous pain relief.
  • Chronic pain treatment: Epidural anaesthesia is an effective treatment option for chronic pain management, especially for conditions related to the spine, such as herniated discs, sciatica, and spinal stenosis.

As mentioned above, the techniques for spinal and epidural anaesthesia differ. However—just like in case of general anaesthesia—there is a preoperative stage where medical history, medications, and allergies are taken into account. The techniques for spinal and epidural anaesthesia (following the preoperative stage) have been provided below.

  • Spinal anaesthesia technique:
    • Checking of spinal anatomy: This is done to allow for safe needle placement and drug delivery to ensure reduced risk of complications, such as spinal cord injury, nerve damage, or failed anaesthesia.
    • Drug administration: A small amount of local anaesthetic is directly injected via a needle into the cerebrospinal fluid (CSF) in the subarachnoid space (the space surrounding the spinal cord) in the lower back (lumbar region). This results in the rapid numbing of the target region (1 to 5 minutes for numbing).
    • Monitoring: Vital signs like blood pressure, heart rate, and oxygen saturation are continuously monitored and complications like low blood pressure (hypotension) and slow heartbeat (bradycardia)—which may require treatment with intravenous fluids, ephedrine, or atropine—are looked out for.
    • Onset of anaesthesia: Numbing is checked using a pinprick test or cold swab.
    • Post-procedure care: After the completion of the procedure, patients are positioned flat on their back to allow even distribution of the anaesthetic and continuously monitored for complications like low blood pressure (hypotension), spinal headache (headache caused due to cerebrospinal fluid (CSF) leakage through the dura matter), nerve damage, and in rare cases, respiratory and cardiovascular compromise (a situation where the normal functioning of the lungs and heart is impaired or weakened, potentially leading to life-threatening conditions).
  • Epidural anaesthesia technique:
    • Identification of epidural space: The epidural space, i.e., the site of injection is identified to ensure safe needle placement.
    • Needle insertion and catheter placement: A Tuhoy needle is inserted to access the epidural space, which lies just outside the dura mater surrounding the spinal cord. Once the epidural space is located, a catheter is inserted to deliver local anaesthetics and/or pain relief medications.
    • Test dose administration: Before administering the final dose, a small amount of anaesthetic mixed with epinephrine is administered to the patient and the patient is subsequently checked for tachycardia (rapid heartbeat) or metallic taste (indicating accidental vein injection) and rapid numbness or motor block (indicating accidental dural puncture). If both are negative, the anaesthetic is administered.
    • Drug administration: A local anaesthetic (e.g., bupivacaine) is injected into the epidural space (the space outside the dura matter)— either as a single dose (bolus) or continuously—through the catheter to block nerve signals and provide pain relief. This technique results in slow numbing of the target region (10 to 25 minutes for numbing).
    • Monitoring: Vital signs like blood pressure, heart rate, and oxygen saturation are continuously monitored, and signs of low blood pressure (hypotension) looked out for.
    • Onset of anaesthesia: Numbing is checked using a pinprick test or cold swab.
    • Post-procedure care: After the completion of the procedure, the catheter is removed and patients are observed for complications like low blood pressure (hypotension), infection, or bleeding (and in rare cases, dural puncture‒associated headache).

As with general anaesthesia, the risks associated with spinal anaesthesia may be common or rare depending on the root cause or the patient’s medical history or genetics.

  • Common risks
    • Hypotension (low blood pressure): This is caused when the anaesthetic blocks the sympathetic nerves (nerves that control the body's "fight-or-flight" response, which prepares the body for situations requiring heightened alertness or quick action), resulting in reduced cardiac output. Symptoms include dizziness, nausea, fainting, or, in severe cases, cardiovascular collapse.
    • Post-dural puncture headache (PDPH): This is caused by the leakage of cerebrospinal fluid (CSF) through the puncture site in the dura mater. Symptoms include severe headache, stiffness in the neck, nausea, and sensitivity to light.
    • Nausea and vomiting: These are the result of low blood pressure (hypotension) or visceral nerve irritation (a condition in which, nerves that carry signals between the internal organs (viscera) and the central nervous system (CNS) get inflamed, injured, or compressed).
      Back pain: This is caused due to local tissue trauma or muscle spasm at the injection site.
    • Difficulty urinating (Urinary retention): This is caused due to the inability of sacral nerves—which control bladder function—to transmit signals.
  • Rare but serious risks:
    • High or total spinal block: This is caused by the excessive spread of the anaesthetic into higher spinal levels, potentially affecting respiratory muscles or the brainstem. Symptoms include difficulty in breathing, low blood pressure (hypotension), slow heartbeat (bradycardia), or loss of consciousness.
    • Neurological complications: These are caused as a result of direct nerve injury, spinal cord trauma, or hematoma (leakage of blood from the blood vessels into the surrounding tissue). Symptoms include persistent numbness, weakness, tingling, or in extremely rare cases, paralysis.
    • Infection: Meningitis (infection of the membranes enveloping the brain and spinal cord, i.e., meninges) and brain abscess (infection of the brain) can be caused as a result of contamination during the procedure. Symptoms include severe back pain, fever, and neurological issues, such as memory problems, difficulty in thinking, confusion, changes in sensation, and even seizures.
    • Bleeding (Spinal hematoma): This is caused due to the accidental puncture of the blood vessels during anaesthesia. This is especially common in patients with blood clotting disorders or who are on anticoagulants (agents that do not allow the blood to clot). Symptoms include severe back pain and neurological deficits ranging from ranging from pain and numbness to paralysis and autonomic dysfunction (a condition where the part of nervous system that controls core functions, like heart rate, blood pressure, digestion, and temperature regulation, does not function properly).
    • Allergic reactions: These are caused when the patient is sensitive to the anaesthetic drug or preservatives used. Symptoms include rash, itching, or anaphylaxis (a severe, potentially life-threatening allergic reaction that occurs immediately after exposure to an allergen).

If spinal or epidural anaesthesia fails, i.e., the anaesthetic does not work as expected and does not provide the desired level of pain relief, or if the patient is incompatible with the anaesthetics used in these techniques, the doctors can choose to go with general anaesthesia for the procedure.

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