Peridural Anesthesia

Peridural anesthesia (PDA) (synonym: epidural anesthesia (EDA); also called spinal anesthesia) is one of the procedures of regional anesthesia (conduction anesthesia) and is used to temporarily interrupt neuronal excitation conduction. The so-called peridural space surrounds the dura mater (hard meninges) and is located in the spinal canal, where it extends from the foramen magnum (lat. : large opening) of the skull base to the sacrum. Within the peridural space are fatty tissue, connective tissue, venous plexuses, arteries and lymphatic vessels. Peridural anesthesia focuses primarily on the spinal cord and spinal nerves (nerve roots that branch off from the individual segments of the spinal cord) and thus opens up a wide range of possible applications. This includes, above all, pain therapy during childbirth. Pain therapy during surgical procedures forms another indication area, and here the possible applications are almost identical to those of spinal anesthesia.

Indications (areas of application)

  • Anesthesia for major surgical procedures.
  • Treatment of chronic tumor pain
  • Diagnosis of chronic pain
  • Postoperative pain management: longer-term blockade via a peridural catheter.
  • Post-traumatic pain treatment: e.g., for a rib series fracture by peridural anesthesia in the thoracic region.
  • Pain therapy in normal vaginal birth.
  • Other indications include:
    • Expected difficult intubation
    • Non-fasted patients
    • Geriatric patients
    • Patients with cardiopulmonary diseases
    • Malignant hyperthermia, renal and liver disease, muscular disease, metabolic disease.

Contraindications

Absolute contraindications

  • Neurological diseases
  • Lack of patient consent
  • Infection at the injection site
  • Shock
  • Spinal stenosis (narrowing of the spinal canal)
  • Blood clotting disorders

Relative contraindication

  • Anamnestic severe back pain and/or headache.
  • Local diseases of the spine: arthritis (joint inflammation), disc prolapse (herniated disc), osteoporosis (bone loss), spinal metastases (osseous metastases)
  • Sepsis (blood poisoning)
  • Severe deformity of the spine
  • Hypovolemia (volume deficiency)

Before peridural anesthesia

Preoperatively, the patient’s medical history (anamnesis) is first taken. Important here is information on allergies to medications, especially local anesthetics, as well as systemic diseases that can lead to complications during the procedure (e.g., cardiovascular disease). This is followed by a physical examination, interpretation of laboratory results, and patient education. This is followed by administration of premedication (administration of medication before a medical procedure), which in this case is primarily for anxiolysis (anxiety resolution).

The procedure

In principle, the peridural space can be punctured at many sites. However, the safest procedure is to puncture the midline of the lumbar region, because the peridural space extends further here and thus there is less risk of spinal cord injury. Because of the roof tile-like position of the spinous processes, puncture in the thoracic region, for example, is very difficult. Thoracic puncture is used in abdominal and thoracic (chest) surgeries. The procedure can be performed in a sitting position or on a supine patient. Hand disinfection and extensive disinfection of the surgical area are performed before the procedure. The anesthesiologist is dressed in sterile headgear, sterile mouthguard and sterile gloves. First, the attending physician must anesthetize the puncture site and then locate the peridural space. For this purpose, the loss of resistance technique is available to him as a standard procedure. In the loss of resistance technique, the anesthesiologist is guided by the anatomical resistances encountered by his needle. He uses a syringe that is fluid-filled and whose plunger is smooth. The greatest resistance is formed by the ligamentum flavum (lat. : yellow band). When the needle passes the ligament, the anesthetist can determine whether he is already in the peridural space on the basis of the plunger mobility of the syringe.If this is the case, 3-4 ml of a test dose of the local anesthetic can be injected to rule out puncture of the dura mater (hard cerebral membrane; outermost meninges). Before doing so, however, it is necessary to check by aspiration (pulling on the syringe) whether a blood vessel has been punctured. If the drug enters the bloodstream, severe complications are the result. The test dose is injected under strict control of vital signs (cardiac activity, etc.). Now the remaining dose can be given. During the procedure, in addition to the local anesthetics, a vasopressor (substance used to raise or support blood pressure), usually epinephrine, (drug that has a vasoconstrictor effect) is injected, which improves the blockade and reduces the risk of a toxic reaction to the anesthetics. If a lower dose of the local anesthetic is chosen, sensory blockade is achieved, while a higher dose additionally leads to motor blockade. Common local anesthetics in Germany are:

  • Bupivacaine
  • Etidocaine
  • Lidocaine
  • Mepivacaine
  • Prilocaine
  • Ropivacaine

The analgesic effect (analgesic effect) occurs after 5 to 10 minutes and lasts a maximum of 20 to 30 minutes.

After surgery

After peridural anesthesia, special neurologic monitoring is indicated because in rare cases there is a possibility of spinal hemorrhage. This can lead to severe radicular pain (pain along the insertion areas of the nerve roots from the spinal cord), progressive motor and sensory deficits, and bladder voiding dysfunction and requires immediate neurologic treatment. The patient must be monitored as an inpatient and should take it easy.

Possible complications

  • Anaphylactic (systemic allergic) reaction.
  • Anterior spinal artery syndrome – ischemia (impaired blood flow) to the spinal cord caused by injury to the anterior spinal artery
  • Arachnoiditis – infection of the arachnoid (spider skin).
  • Blood pressure drop – due to sympathetic blockade (this part of the nervous system maintains blood pressure).
  • Cauda equina syndrome – bladder emptying disorders, breeches anesthesia (sensitive failures of the nerves in the sacrum (sacrum)), fecal incontinence, paralysis.
  • Purulent meningitis – bacterial meningitis.
  • Epidural hematoma – bleeding into the epidural space (space between the bones of the skull and the dura mater (hard meninges, outer boundary of the brain to the skull)).
  • Epidural abscess – infection in the epidural space with cavity formation.
  • Cephalgia (headache)Note: If dural puncture has occurred (postdural headache), bed rest after puncture cannot be recommended; bed rest is more likely to be detrimental and there is also no evidence for fluid supplementation
  • Myelitis – inflammation of the spinal cord
  • Nerve root injury
  • Reaction to vasoconstrictor addition – tachycardia (rapid heartbeat), increase in blood pressure, sweating, mental overexcitement, headache.
  • Toxic reaction with generalized convulsions
  • Total spinal or peridural anesthesia – bradycardia, drop in blood pressure, loss of consciousness, respiratory failure
  • Vagovasal reaction – “blackening before the eyes”.

Peridural vs. spinal anesthesia

While the effect of spinal anesthesia is very fast and stronger, peridural anesthesia requires a slightly longer latency period. In particular, the motor blockade with spinal anesthesia is stronger. The advantage here is a higher quality of anesthesia and better controllability with a smaller amount of anesthetic. Peridural anesthesia requires a higher dose of local anesthetics and is less predictable in its severity with lower anesthetic quality. In application, this means the following: Spinal anesthesia is popular for surgery because of better motor blockade, but it can lead to so-called postspinal headaches. Because of its longer-term effect, peridural anesthesia is used, among other things, in continuous nerve blockade, which can be carried out for days to weeks. Further notes

  • Instrumental or operative delivery is more likely to be avoided in primiparous women receiving epidural anesthesia if they adopt a recumbent position during the expulsion phase of labor. The absolute difference was 5.9 percent.This means that one in about 17 women can avoid an instrumental birth (from 54.6% to 50.6%) or a caesarean section (C-section; 10.2% to 8.3%) if she gives birth in a recumbent position.