Epidural anaesthesia

INTRODUCTION:
  • Epidural anesthesia are medicines that numb parts of your body to block pain. 
  • They are given through shots in or around the spine.
  • 1-2% lignocaine with or without adrenaline is used in epidural anaesthesia.
  • Epidural anaesthesia is preferred over spinal anaesthesia because of Prolonged duration of effect
  • One advantage of an epidural is that the muscle blockade can range from none to complete and can be regulated and changed by:
  1. Choice of drug
  2. Concentration of LA
  3. Dosage
  4. Level of injection
PHYSIOLOGY:
  • Local anesthetics or other solutions injected into the epidural space (steroids, narcotics) spread anatomically
  • Horizontal spread is to the region of the dural cuffs with diffusion into the CSF and leakage through the intervertebral foramen into paravertebral spaces
  • Longitudinal spread is preferentially cephalad in direction
  • Possible sites of anesthetic action include:
  1. Paravertebral nerve roots
  2. Intradural spinal roots
  3. Dorsal and ventral spinal roots
  4. Dorsal root ganglia
  5. The spinal cord
  6. The brain itself (by diffusion)
FACTOR AFFECTING:
  • Injection site
  • Dose
  • Volume
  • Concentration
  • Position
  • Age
  • Height and weight 
  • Pregnancy 
  • Speed of injection 
INDICATIONS:

Indications for epidural nerve block can be divided into the following categories:
  • Sole epidural anesthetic
  1. Orthopedics - Surgeries of lower limbs, including hip, knee, and pelvic areas
  2. Vascular surgery - Lower limbs, amputations
  3. Obstetrics - Cesarean delivery
  4. In pregnant patients with mitral stenosis, mitral regurgitation, aortic stenosis or aortic regurgitation epidural anaesthesia is the preferred route during labour.
  5. Gynecology - Surgeries of female pelvic organs
  6. Urology - Prostate and bladder surgeries
  7. General surgery - Lower abdominal surgeries, including appendectomy, bowel surgeries, hernia repair
  • Epidural anesthetic in combination with spinal anesthetic
  1. This combination is referred to as combined spinal epidural (CSE).
  2. All of the indications noted above & Lower Segment Caesarean section (LSCS)
  • Epidural anesthetic in combination with general anesthetic
  1. All of the indications noted above for sole epidural anesthetic may also be performed with CSE.
  2. Pediatric surgery - Penile procedures, inguinal hernia repair, lower limb orthopedic procedures
  3. Thoracic surgery -Thoracotomy, cardiac bypass, other cardiac surgeries
  4. Epidural analgesia combined with general anesthesia reduces the incidence of postoperative pneumonia in patients with chronic obstructive pulmonary disease who are undergoing major abdominal surgery
  • Epidural analgesia 
  1. Prolonged postoperative analgesia obtained by continuous or patient-controlled infusions of local anesthetics, opioids, adjuvants, or a combination thereof Labor epidural analgesia
  2. Single-shot epidural injection of depot form of morphine (Duramorph) can provide 6-24 hours of analgesia. DepoDur (EKR Therapeutics, Bedminster, NJ) is a formulation that provides more than 2 days of analgesia with a single injection.
  • Epidural for chronic pain management 
  1. Disk herniation, degeneration, and spondylosis
  2. Radiculopathy -Cervical, thoracic, lumbosacral
  3. Spinal stenosis and facet arthropathy
  4. Sympathetic mediated/maintained pain of upper or lower extremities
  5. Pelvic pain - Aid with pelvic floor physical therapy
CONTRAINDICATIONS:
  • Absolute contraindications
  1. Patient refusal
  2. Uncorrected hypovolemia
  3. Increased intracranial pressure
  4. Infection at the site
  5. Allergy to local anesthetic (For more information, see Local Anesthetic Agents, Infiltrative Administration.)
  • Relative contraindications
  1. Coagulopathy
  2. Platelet count < 100,000
  3. Uncooperative patient
  4. Spine abnormalities and surgeries
  5. Sepsis
  6. Unstable spine from trauma
  7. Positioning problems
  8. General anesthesia (controversial)
Technique
  • Identification of Epidural Space
  1. Epidural anaesthesia in pregnancy is Given through Epidural space
  2. T10 – S5 level outside dura of block is desired for painless delivery by epidural anaesthesia
  3. An epidural block up to the level T10 will be adequate in preventing pain arising from the uterus and structures below during labour.
  4. Epidural anaesthesia should only be given after the onset of active labour. ie cervical dilatation of more than 3 cm.
  • Insertion Techniques
Interlaminar technique
  1. Midline interlaminar approach 
  2. Paramedian interlaminar approach
  3. Lateral parasagittal interlaminar approach 
  • Transforaminal technique
  • Level of Insertion
  • The level of insertion is determined by the indication for epidural placement.
  1. Lumbar level
  2. Thoracic level
  3. Cervical interlaminar level
  4. Caudal level
COMPLICATIONS: 
  • CVS changes that occur in epidural anaesthesia are vasodilation which leads to peripheral pooling of blood, reduced venous return, reduced cardiac output and hypotension.
  • During injection of local anesthetic into a dural tear will result in a high block,manifesting as unconsciousness, severe hypotension, and respiratory paralysis requiring (causing hypopnoea).
  • Accidental dural puncture more often results in a severe headache.
  • Nausea & vomiting, total spinal analgesia, prolonged analgesia are other common complications.
  • A common complication of epidural anesthesia is prolonged blockade of parasympathetic fibers that innervate the bladder with resultant urinary retention.
Exam Question
  • Lower Segment Caesarean section (LSCS) can be carried out under Combined Spinal Epidural anaesthesia
  • In pregnant patients with mitral stenosis, mitral regurgitation, aortic stenosis or aortic regurgitation epidural anaesthesia is the preferred route during labour.
  • 2% concentration of lignocaine is used in epidural anaesthesia
  • Epidural anaesthesia in pregnancy is Given through Epidural space
  • Epidural anaesthesia in pregnancy Decreased venous return,Bladder distension,Hypotension,Nausea & Hypotension
  • Hypopnoea, Total spinal analgesia, Urinary retention are the complications of Epidural anaesthesia in pregnancy 
  • T10 – S5 level of block outside dura is desired for painless delivery by epidural anaesthesia
  • Epidural anaesthesia is preferred over spinal anaesthesia because of Prolonged duration of effect

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