Epidural Anesthesia


Article Author:
Adrian Avila-Hernandez


Article Editor:
Paramvir Singh


Editors In Chief:
Dustin Constant
Donald Kushner


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Avais Raja
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Mark Pellegrini
James Hughes
Beata Beatty
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes


Updated:
5/30/2019 3:44:03 PM

Introduction

Epidural anesthesia is a technique for perioperative pain management with multiple applications in anesthesiology. It is useful as a primary anesthetic, but most commonly it is used as pain management adjuvant. It can be a single shot or a continuous infusion for long term pain relief. Aside from the benefit of potentially providing excellent analgesia, its use reduces the exposure to other anesthetics and analgesics, decreasing side effects. It has also shown to decrease cortisol levels, expedite the return of bowel function, decrease the incidence of PE and DVT in the postoperative period, and shorten lengths of in-hospital stay.[1][2][3]

Anatomy

The spinal cord is about 45 cm shorter than the spinal canal in the adult. It ends at L1 in 50% of the adults and L2 in about 40%. In the newborn, it goes down to L2-L3. Below this level, the lumbar and sacral nerves converge to form the cauda equine. The spinal cord is suspended in Cerebrospinal Fluid and surrounded by the arachnoid membrane. The arachnoid (and subarachnoid space) extends caudally in the adult to S2, to S3 in children and S4 in the newborn. The arachnoid is close to the dura mater. The dura is attached to the spine by its outer endosteal portion. It envelopes the brain intracranially, the spine and it also extends out through the foramina intervertebralia to the epineural connective tissues of the spinal nerves. The spinal epidural space contains fatty and connective tissues as well as vessels and lymph channels. These vessels may dilate with gravidity or ascites, which increase the likelihood of bloody puncture. The distance between the skin and the epidural space is variable depending on factors like age or weight. It may be 4 cm in normal-weight adults to 8 cm or more in obese patients. The epidural space has a dorsal limitation by the ligamentum flavum. More superficially, the remaining layers are the ligamentum interspinale (located between the spinous processes), ligamentum supraspinale (located on the surface of the spinous processes), subcutaneous tissue and skin.[4]

Indications

Epidurals are useful for surgical anesthesia of thoracic surgery, major intra-abdominal surgery or spine surgery, granted that muscle relaxation is not needed. This technique may also be for intra-op or post-op pain management. It may decrease the surgical risk and morbidity of certain patient populations, for example, patients with ischemic cardiac disease. It also has shown to decrease post-op lung complications and increase the intestinal return of function after abdominal surgery.[4][3]

Contraindications

Absolute:

  • Refusal of the patient
  • Bacteremia
  • Local infection at the site of puncture
  • Hemorrhagic diathesis or therapeutic anticoagulation
  • Increased intracranial pressure

Relative[4]:

  • Significant aortic stenosis
  • Right to left shunt and pulmonary HTN
  • Anatomical deformities of the spine

Equipment

  • Epidural needles: Multiple types have been designed (Tuohy, Hustead, Crawford, Weiss, etc.), Tuohy being the most used one. These are usually 17 or 18 G and 3.5 inches long (up to 6 inches for obese patients).
  • Loss of resistance syringe: Either made of glass or plastic. It has very low friction between the plunger and the barrel to allow for the detection of the change in resistance at the epidural space. The syringes may be filled up with air, saline, or both, and this apparently does not affect the success at identifying the epidural space, nor does it change the rate of complications.[5]
  • Epidural catheters: used for continuous epidural anesthesia/analgesia. They may be flexible or stiff. They may also have a single hole or multiple ones.[6]

Personnel

  • Anesthesiologist
  • Nurse Anesthetist

Preparation

  • Emergency equipment and medications need to be available before the procedure.
  • An IV must be available for fluid and medication administration if needed.
  • Standard ASA monitors must be applied before proceeding.
  • The patient may be positioned in a sitting or lateral decubitus position. Arching of the back is advised for better exposure of intervertebral interspaces.
  • Aseptic management of the disposable epidural kit and preparation of the field must be performed.[4]

Technique

Two approaches exist, medial (midline) and paramedian.

In the medial approach, the site of the insertion of the needle is between the spaces created by the vertebral spinous processes. Upon locating the desired spot, lidocaine 1% must be injected in the skin and underlying tissues to decrease the discomfort with the advancement of the epidural needle. Once achieving local anesthesia, the epidural needle must be advanced with its stylet in place and with its bevel point cephalad; this is ultimately going to contribute to the proper location of the epidural catheter. The epidural needle must be advanced through the skin, subcutaneous tissue, supraspinous, and interspinous ligaments. Once there, the stylet must be removed, and the Loss of Resistance syringe (filled up with saline, air or both) must be attached to the needle. The needle must be advanced while applying pressure to the plunger. Once the ligamentum flavum is pierced, a loss in resistance will be noted; this is the epidural space, and 5 to 10 cc of saline may be injected to expand the epidural space; this may decrease the risk of vascular injury.

In the paramedian approach, the insertion site of the needle is 1 cm lateral to the vertebral interspace. Local anesthetic must be administered as described for the medial approach. The epidural needle must then be advanced through the paraspinal tissues. Given this location, the needle will not transverse the supraspinous or interspinous ligaments. The advancement of the needle must stop upon feeling the engagement in the ligamentum flavum. The loss of resistance syringe must be then attached, and the epidural space must be located as described for the median approach.

Once either the midline or paramedian approach locate the epidural space, the epidural catheter must be advanced inside the needle after removing the loss of resistance syringe. The epidural catheter must be advanced to the 20 cm mark. The epidural needle is then removed, paying attention to the depth of the epidural space as indicated by the marks in the epidural needle. The epidural catheter is then withdrawn, aiming to leave its tip 5 to 6 cm into the epidural space; achieved by adding 5 to 6 to the depth of the epidural space. The resulting number is the mark at which the epidural catheter must be withdrawn.

Once the catheter is in its final position, a 3 cm syringe may be used to gently aspirate and rule out CSF leakage. If CSF is detected, the epidural catheter may be in the intrathecal space and must be relocated.

A test dose to rule out the intravascular position of the catheter is then performed, done by injecting 3 mL of 1.5% lidocaine with epinephrine (1 to 200000). An increase in HR of 20 to 30 bpm or 15 to 20 mmHg in systolic blood pressure, may indicate intravascular injection.

Caudal Anesthesia:

Caudal anesthesia is a variation of epidural anesthesia widely used in childhood. It is useful for interventions under the umbilicus line (circumcision, herniotomy, orchiopexy). The indications and contraindications match the ones described above.

The patient positioning is in lateral decubitus, and fetal position, the area sterile prepped and the hiatus sacralis located at the vertex of the sacrum, between the cornua sacra. The sacrococcygeal membrane must be pierced with a 22 to 25 G venous catheter in a 45-degree angle relative to the longitudinal axis of the body. The catheter must be advanced until the loss of resistance is felt. No additional advance must be attempted since the distance between the sacrococcygeal membrane, and the caudal end of the dural sac may be less than 10 mm. If CSF or blood is noted, the catheter must be repositioned. Once properly located, a test dose with Epinephrine 0.5 mcg/kg may be performed to rule out an intravascular injection.[4][7][8]

Complications

The following complications can accompany epidural anesthesia[4]:

  • Hypotension
  • Nausea, vomiting
  • Bronchoconstriction
  • Post puncture headache after dural perforation
  • Transient neurological syndrome (symmetrical back pain, radiated to the buttocks and legs, without sensitive or motor component)
  • Nerve injury with possible neuropathy - paresis is extremely rare
  • Epidural hematoma
  • Epidural abscess
  • Meningitis
  • Accidental intrathecal injection with total spinal anesthesia
  • Osteomyelitis

Clinical Significance

The epidural technique is one of the earliest ones in the field of anesthesia. Properly performed, it is a safe technique that provides multiple benefits. It is usable as a sole anesthetic for surgical procedures, therefore decreasing the need for general anesthesia and airway management, with the risks that this implies. It also reduces the exposure to volatile anesthetics as well as it may potentially decrease the narcotics requirement, during or after a procedure. Hence lowering the incidence of the side effects associated with them; this is particularly relevant in the field of pediatric anesthesia since the controversy has been raised regarding the potential negative impact of certain anesthetic drugs in neurodevelopment. The epidural technique is also highly valuable for postoperative pain management as part of a multimodal approach.

Enhancing Healthcare Team Outcomes

There is a growing body of evidence that demonstrates the use of epidural anesthesia/analgesia techniques has positive effects like faster return in bowel function, a decrease of the hormonal stress response to pain, decrease in postoperative pulmonary complications, shortening in the length of in-hospital stay and patient satisfaction.

Close monitoring of the patient by nurses in the postoperative period is key to safety

Adequate consideration of risks and benefits is necessary on a case by case basis.

Safe and effective use of epidural anesthesia requires an interprofessional team approach, including physicians, specialists, specialty-trained nurses, and pharmacists, all collaborating across disciplines to achieve optimal patient results. [Level V]


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Epidural Anesthesia - Questions

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Which of the following is not a side effect of opioids during epidural anesthesia?



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A 35-year-old pregnant woman at 36 weeks of gestation with a history of preeclampsia has been at the hospital for prior 3 days due to intermittent uterine contractions. She has completed her course of steroids for fetal lung maturation. She has also been receiving unfractionated heparin for thromboprophylaxis. At this point, the Ob/Gyn team has decided to stop the utero inhibition and allow the progression of labor. An epidural catheter will be placed for epidural analgesia. Which of the following is the correct course of action before performing an epidural?



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A 60-year-old male is currently in the ICU after having suffered a motor vehicle collision. Some of the injuries sustained consist of numerous rib fractures. Your regional anesthesia team is consulted for a possible thoracic epidural. A paramedian approach is selected. Which of the following structures would not be transversed by the epidural needle while using this approach?



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A pregnant woman receives epidural anesthesia for a C Section after a failed induction of labor. Once the surgery is completed, and the epidural catheter is removed, which of the following is the patient most likely to report as the last residual effect of the epidural anesthesia?



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Your regional anesthesia team is consulted about a 45-year-old man who underwent a Whipple procedure the day before. This patient has already received pain medications of multiple types but continues to complain of unbearable pain. The primary team is requesting a thoracic epidural to address this patient’s pain. Which of the following factors will play a major role in the success of your intervention?



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A 23-year-old pregnant woman at term with a history of a prior C Section is admitted to the hospital for induction of labor. She requests an epidural for pain management. You agree to perform it but explain to her that as a result of the use of epidural analgesia there is an increased risk of which one of the following?



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A 25-year-old woman at term is admitted to the hospital in labor. She only attended one prenatal visit during her second trimester and was diagnosed with preeclampsia but no treatment was instituted. Her BMI is 35 and she has a prior diagnosis of OSA but she is not compliant with her CPAP treatment. Which of the following would preclude her from receiving epidural analgesia for labor?



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A 30-year-old pregnant woman at term is undergoing induction of labor. An epidural catheter has just been placed for pain management, and a bolus of Bupivacaine has been given. The patient complains of nausea after this. How could an anticholinergic medication be of use in this scenario?



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Epidural Anesthesia - References

References

Triffterer L,Marhofer P,Lechner G,Marksz TC,Kimberger O,Schmid W,Marhofer D, An observational study of the macro- and micro-haemodynamic implications of epidural anaesthesia in children. Anaesthesia. 2017 Apr;     [PubMed]
Strandness T,Wiktor M,Varadarajan J,Weisman S, Migration of pediatric epidural catheters. Paediatric anaesthesia. 2015 Jun;     [PubMed]
Moriarty A, Pediatric epidural analgesia (PEA). Paediatric anaesthesia. 2012 Jan;     [PubMed]
Gerheuser F,Roth A, [Epidural anesthesia]. Der Anaesthesist. 2007 May;     [PubMed]
Antibas PL,do Nascimento Junior P,Braz LG,Vitor Pereira Doles J,Módolo NS,El Dib R, Air versus saline in the loss of resistance technique for identification of the epidural space. The Cochrane database of systematic reviews. 2014 Jul 18;     [PubMed]
D'Angelo R,Foss ML,Livesay CH, A comparison of multiport and uniport epidural catheters in laboring patients. Anesthesia and analgesia. 1997 Jun;     [PubMed]
Harrison GR,Clowes NW, The depth of the lumbar epidural space from the skin. Anaesthesia. 1985 Jul;     [PubMed]
Afshan G,Chohan U,Khan FA,Chaudhry N,Khan ZE,Khan AA, Appropriate length of epidural catheter in the epidural space for postoperative analgesia: evaluation by epidurography. Anaesthesia. 2011 Oct;     [PubMed]

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