Epidural Anesthesia and Analgesia

Epidural anesthesia and

analgesia

Anesthesiology dep. R2 Mei-Hui, Yang 2004/08/16

Wide application

 Epidural block can be performed at the sacral

(caudal), lumbar, thoracic or cervical levels.

 Epidural techniques are widely used for operati

ve anesthesia, obstetric analgesia, postoperati ve pain control, and chronic pain management.

 Dose judgment could be single shot, intermitte

 Differential block:

By using relatively dilute concentrations of local anesthetic combined with an

opiate, an epidural can block the smaller sympathetic and sensory fibers wile

 Segmental block:

Due to local anesthetic is not spread rea dily in CSF as spinal anesthesia, a well-d efined band of anesthesia at certain nerv e roots without those above and below bl ocked can be achieved with epidural tec hniques.

Advantages in conjugation with GA

 CV systems:

Blockade of cardiac sympathetic

innervation (arise at T1-T4) with dilute local anesthetic postoperatively via a thoracic epidural catheter can reduce myocardial ischemia in patients with coronary artery disease.

Respiratory system

 Thoracic or upper abdominal surgery is a

ssociated with

1.decreased diaphragmatic function post operatively from decreased phrenic nerv e activity

2. decreased FRC

these can lead to atelectasis and hypoxi a via V/Q mismatch

 Some evidence suggests that

postoperative thoracic epidural analgesia in high-risk patients can improve

pulmonary outcome by decreasing the incidence of pneumonia and respiratory failure, improving oxygenation, and

decreasing the duration of mechanical ventilatory support

Metabolic and endocrine system

 Surgical trauma produces increases in ACTH,

cortisol, epinephrine, norepinephrine and vasopressin and activate RAA system.

 Neuraxial blockade can partially suppress

(during major invasive surgery) or totally block (during lower extremity surgery) this stress

response and then reduce perioperative arrhythmias and the incidence ischemia possibly. A T11 block can block adrenal pathways and blunt hyperglycemia.

Complication of neuraxial block

 Headache

 Urinary retention  Maternal fever

 Transient neurologic symptoms (TNS):

back pain radiating to the legs without sensory or motor deficits, occurring after the resolution of spinal block and resolving spontaneously within several days

 High or total spinal anesthesia  Subdural injection

 Cardiac arrest  Systemic toxicity

 Cauda equina syndrome & other neurologic def

icits, transient or permanent

 Maningitis & arachnoiditis  Epidural abscess

Paraplegia after delayed detection

of inadvertent spinal cord injury

during thoracic epidural

catheterization in an anesthetized

elderly patient

Ming-Chang Kao, MD, Shen-Kou Tsai, MD, PhD, Mei-Yung Tsou, MD, PhD Dep. Of Anesthesiology and Radiology, TVGH Anesth Analg 2004, Aug.;99:580-3

Foreword

 Permanent paraplegia after epidural

anesthesia is extremely rare; the incidence is <0.02%

 The cause are diverse, including epidural

hematoma, epidural abscess, direct cord trauma, spinal infarction and

neurotoxicity by accidental subarachnoid injection or chemical contamination.

Case report

 An 81-yr-old man with acute cholecystitis

and common bile duct stones underwent open cholecystectomy and choledocholit hotomy.

 Medical hx: HTN with baseline BP 166/6

7 mmHg

 Thoracic epidural for postoperative pain r

 After explanation the possible risks, inclu

ding potential cord injury, the procedure was performed after the induction of GA due to his fear about the procedure when he was awake.

 With left lateral position, a17-gauge Tuoh

y needle was introduced at the T9-10 int erspace.

 Three needle passes were made to locat

e the epidural space by using the loss-of-resistance-to-air technique.

 A 19-gauge single-end port catheter was

inserted 3.5 cm cephalad.

 There was some resistance to catheteriz

ation through the needle. Catheter aspira tion was negative.

 Lidocaine 2% 2 ml with 1:200000 epinephrine

was injected as a test dose. The arterial BP slightly decreased from 130/64 to 110/52 mmHg 5 min later.

 Ten minutes after the test dose injection, an

epidural bolus of 0.2% bupivacaine 8ml with morphine 1 mg was given. ABP gradually

decreased to 70/40 mmHg within the next 10 min but returned to 110/60 mmHg after

ephedrine 16 mg and lactated Ringer’s solution 500ml IV were administered.

 OP lasted for 2.5 h and was uneventful.  In the PACU, he was pain free and did

not complain of motor or sensory

impairment. PE showed freely movable extremities but relative weakness in the lower extremities, with muscle strength of 4/5 and poor response to pain and sensory stimulus.

 Negative catheter aspiration was confirmed

again to exclude intrathecal placement.

 PCA pump was then programmed to deliver

0.1% bupivacaine with fentanyl 1ug/ml at a basal rate of 4ml/h, with a demand dose of 2 ml and a lockout interval of 20 min. The SBP was 100-130 mmHg in the PACU and he was returned to the ward 1h later without significant further decreases in muscle strength.

 The patient first complained of numbness and

weakness of the lower extremities 8 h after surgery, early the next morning.

 NE revealed:

1.sensory loss below T11

2.paraplegia with no movement of either lower extremity

 No blood was aspirated from the catheter and

 A total volume of 44ml of bupivacaine

with opioid was given.

 NE remained unchanged 4h after

discontinuation of the pump infusion.

 Emergent CT showed an intramedullary

 MRI revealed extensive intramedullary a

bnormally high signals on T2-weighted i mages from dorsal T12 extending upwar d to ventral T4.

 The intramedullary air bubble at T9 was

Following treatment

 Methylprednisolone 30 mg/kg IV bolus over 15

min, followed y a 5.4mg/kg/h IV infusion for the next 23h was given according the neurologist’s suggestion.

 Summarized neurologic deficits on

postoperative Day 3 revealed bowel and

bladder incontinence, flaccid paraplegia with areflexia, loss of pain and temperature

perception but preservation of touch and position sensations of both legs.

 MRI on postoperative Day 22 revealed a

small residual intramedullary abnormally high signal on T2W at ventral T8

 The final follow-up 6 mo later showed

partially improved sensory function of the lower extremities and muscle strength to 1-2/5.

Discussion

 Severely spondylotic spine

 The air injected into the spinal cord split the cord

and thus facilitated the following catheterization

 The “some resistance” to catheterization was

ignored

 The hypotension after the initial epidural bolus

dose during surgery and the relative

postoperative hypotension were attributed to the intramedullary bupivacaine and opioids.

 The pump infusion may have increased t

he intracord pressure and compormised cord perfusion resulting in a vicious cycle of cord injury.

 In addition to the residual anesthetic effe

cts, the intramedullary bupivacaine and o pioids should have masked the patient’s discomfort during the continuing cord trau ma.

 Besides, delayed response of this elderly

patient and lack of regular neurologic

checkups by acute pain team members

at night also served as obstacles to early recognition.

 There was no direct neurologic complicat

ion related to lumbar epidural catheteriza tions in 4298 anesthetized patients.

~by Horlocker et al Anesth Analg 2003;96:1547-52

 There are insufficient data to support the

assumption of increased risks of thoracic epidural catheterization under general an esthesia.

 Two thirds of the patients with neurologic

deficits had either a paresthesia during n eedle placement or pain on injection.

~Yves Auroy, M.D, Anesthesiology, V87, No3, Sep 1997

 As a result, thoracic epidurals was sugge

sted to be performed only in conscious p atients. This will not eliminate the risks of

cord injuries but will help to identify them earlier.