In epidural anesthesia, analgesics (e.g., local anesthetics, opioids) are administered into the space surrounding the dural sac. After gastrointestinal procedures, thoracic epidural anesthesia not only offers analgesic effects but also positive effects on the cardiac (less myocardial ischemia), pulmonary (less atelectasis, pneumonia) and gastrointestinal (faster recovery of motility) physiology of the patient.

1. Indications

  • Colon surgery
  • Pancreatic resections
  • Gastric resections
  • Cystectomy with neobladder
  • Abdominal aortic surgery

2. Contraindications

  • Patient refusal
  • Coagulation disorders (see below)
  • Lack of communication with the patient
  • Infection at puncture site
  • Anatomical changes in the spine
  • Certain neurologic disorders

2.1 Epidural anesthesia and anticoagulation

To prevent any bleeding complications in anticoagulated patients, certain time intervals must be met before and after insertion/withdrawal of epidural catheters. The German Society of Anesthesia and Intensive Care (DGAi) has consented pertinent guidelines which are updated regularly and reflect current scientific knowledge. The most important rules are listed below (version February 2009).

UFH: on fractionated heparin, NMH: low molecular weight heparin

3. Workflow description

  • Upon transfer check patient identity and the planned procedure (patient file, informed consent documents)
  • Attach leads for monitoring: ECG, NIBP, pulse oximetry
  • IV access and infusion
  • Document baseline measurements in anesthesia record
  • Check lab panel, particularly INR, pTT and platelet count, WBC and CRP
  • Position patient sitting on OR table
  • Thoroughly prep the skin with disinfectant (single-shot contact time of 60 seconds is sufficient, no wiping, the skin must be wetted)
  • Thoroughly disinfect hands (contact time at least 30 seconds)
  • Face mask, sterile gown and scrub cap for anesthesiologist
  • Identify desired location for puncture by counting the palpable spinous processes, e.g., starting with the prominent 7th cervical vertebra. The line between the lower tips of the shoulder blades transects the spine at the level of the C7 and may therefore be used as a reference.
  • A rule of thumb for the level of puncture is that the tip of the epidural catheter should rest roughly in the middle of the segments to be blocked. The following table may serve as reference when selecting the puncture level.
  • The spinous processes of T1 and T2, as well as T10-12 are almost horizontal in the sagittal plane. The other spinous processes T3-9 differ in their angulation and overlap each other. This central region of the thorax therefore requires a steeper angle of puncture (about 45° to the skin).
  • Sterile draping with fenestrated drape
  • Infiltrate puncture site with local anesthetic (1-3 mL scandicaine 1%) Contact with the bones when probing the anatomy with the thin needle helps to define the direction of puncture with the Tuohy needle
  • Introduce the 17G or 18G Tuohy needle with mounted 10 mL syringe filled with saline
  • Advance the needle under continuous pressure on the plunger of the syringe. Thumb and index finger of the left hand (when right-handed) hold the wings of the needle, while middle finger, ring finger and little finger firmly rest on the patient's back. This is a mandatory safety measure against sudden and unplanned deep advance of the needle.  While advancing the needle the right thumb (when right-handed) exerts steady pressure on the plunger.
  • Both control of the needle slowly advancing through the tissue and the pressure on the plunger are technically demanding. Because of possible injury to the spinal cord, thoracic epidural anesthesia should only be performed by experienced physicians.
  • Withdraw the needle in case of paresthesia and/or muscle twitching.
  • Correct the needle position in case of unilateral paresthesia and in accidental puncture of an epidural vein.
  • When passing through the flaval ligament the plunger of the syringe will suddenly give way (loss of resistance).
  • Gently inject saline into the epidural space.
  • Remove the syringe and advance a 20G catheter no more than 3-4 cm into the epidural space, with the opening of the Touhy needle pointing craniad or caudad but not to the side.
  • After successful aspiration testing administer a 3-5 mL test dose of local anesthetic (e.g., scandicaine). Wait at least 5 minutes for any effect of the test dose in case of subarachnoid malposition.
  • Cutaneous catheter fixation. For monitoring over the next few days, cover the puncture side with sterile transparent adhesive.
  • After repositioning the patient induce general anesthesia.

4. Medication in epidural anesthesia

Intraoperative

The rule of thumb for the volume to be administered is about 1 mL of local anesthetic for each segment to be anesthetized. Usually, in single injections this calls for 6-10 mL of local anesthetic. For intraoperative administration, the patient should be in stable cardiovascular condition before the first injection. Particularly in general anesthesia the spreading epidural anesthesia may result in significant blood pressure loss. These adverse reactions should preferably be treated with vasoconstrictive medication and not by administering excessive volume.

Postoperative

Postoperative analgesics are best administered with the pump continuously injecting the local anesthetic into the epidural catheter. Low dose bupivacaine (e.g., 0.25%) or ropivacaine (0.1-0.2%) is well suited for this. Motor function should not be impaired. If needed, the local anesthetic may be combined with an opioid (e.g., sufentanil) and administered via the injection pump. This may improve analgesia without blocking motor function.

5. Hints and notes

  • Do not advance the catheter more than 3 – 5 cm. In many cases, advancing the catheter further may deflect its tip to one side or even flip it caudad thereby producing an inadequate effect.
  • Iatrogenic perforation of the dura is seen in 0.3-1.2% of thoracic epidural anesthesia cases, and postspinal headache in 70-80% of patients.
  • Injection rate, height and body weight do not correlate with the required dose of local anesthetic.
  • The indwelling catheters are visited daily and the following findings obtained and recorded: Pain score, spread of analgesia, signs of motor block, bladder function, appearance of puncture site. When combining the local anesthetic with an opioid also check for itching, nausea/vomiting, signs of systemic opioid effect (e.g., respiratory depression, sedation).
  • Usually, the catheter is removed on postoperative day 4 to 7 (only by an anesthesiologist). In doing so, the time intervals regarding any anticoagulation must be observed (see above). The catheter is only withdrawn after the effect of the local anesthetic has worn off; this will ensure early detection of neurologic symptoms resulting from the presence of epidural hematoma.

Signs of epidural hematoma:

  • Sharp pain in the back and legs
  • Sensory deficits
  • Weakness or paralysis in both legs

Signs of epidural abscess (S. aureus):

  • Severe back pain and tenderness
  • Fever and leukocytosis
  • Progressive para-/tetraparesis

In general, care of patients with indwelling epidural catheters calls for close operation with the nursing staff of the patient’s ward. The staff should be properly trained to recognize the symptoms of neurologic complications in overdosed or underdosed epidural anesthesia.

Author: Prof.C. Diefenbach, MD

Head, Department of Anesthesiology and Surgical Intensive Care

St. Katharinen-Hospital Frechen GmbH, Germany