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Central Neural Blockade
Hasan Arafat5rd Year Medicine Student
An Najah National University
RELATED ANATOMYVertebral Column, Spinal Cord and Spinal Roots
EPIDURAL ANESTHESIA
Definition
• The injection of a local anesthetic into the extradural (epidural) space
• The space extends from the craniocervical junction at C1 to the sacrococcygeal membrane just above the lower border of S2
• Virtually, it’s safe to inject an anesthetic at any level– Thoracic area -> abdomen– Lumbar-> pelvis and lower limb
Technique
• The epidural space is located using the “loss of resistance” method
• The needle is inserted through skin and advanced horizontally until the spinal ligaments (resistant, hard area) are entered
Touhy Needle
Technique (Cont’d)
• The needle tip is removed and an air/saline filled syringe is attached
• If the tip of the needle is in the spinal ligament, it would be difficult to inject into it
• The needle is advanced slowly while pressing and injecting
• As the needle traverses the ligamentum flavum, resistance drops, marking entry into the epidural space
Notes
• A single injection of anesthetic is enough for short procedures
• In longer operations, a catheter is inserted to provide continuous anesthesia and analgesia
Drugs Used in Epidural Anestheisa
• Lidocaine• Concentration: 1.5-2% soln.• Dose: 15-30 mL• Onset: 10-15 min.• Duration: 1.5 hours
• Bupivacaine• Concentration: 0.5% soln.• Dose: 15-25 mL• Onset: 15-20 min.• Duration: 3-5 hours
Note: Epinephrine can be used with both drugs †
Indications
• Surgical procedures in the abdomen, pelvis or lower limb
• Relief of acute pain (labor, post-op pain). A LA or opioids can be used
• Relief of chronic pain (sciatica, CA)• Relief of post-dural puncture headache using
an epidural blood patch
Contraindications
Absolute• Patient refusal• Full anticoagulation or
coagulopathy• Sepsis (systemic/local)• Uncorrectable hypovolemia• Severe fixed cardiac output
state (severe aortic stenosis)• Allergy to LA• Absence of resuscitation
equipment
Relative• Neurological disease in the
lower limbs• Vertebral column deformity• Cardiac disease• Elevated ICP
Complications
• High risk of LA toxicity• Total spinal shock• Post-dural puncture headache• Systemic toxicity• Backache• Broken Catheter
SPINAL ANESTHESIA
Definition
• Injection of a local anesthetic in the subarachnoid space
• Puncture for spinal anesthesia is done below the level of L2 and above S1 †
Drugs Used in Spinal Anesthesia
• Lidocaine 2% and Bupivacaine 0.5% †• Add dextrose ‡• Epinephrine can be added
Operation Site Concentration
Perineum 1-1.5 mL
Lower limbs 2-2.5 mL
Lower abdomen 2.5-3 mL
Above the umbilicus 3-4 mL
Physiological Effects of Spinal Anesthesia
• Nerve Fibers: finer nerves are blocked in the following order:
Autonomic-> temperature -> pain -> touch -> deep pressure -> somatic motor fibers Recovery: reversed
• CVS: – hypotension
Sympathetic blockade -> venous and arterial vasodilation -> pooling of blood in lower limbs -> reduced venous return -> reduced cardiac output -> hypotension
Hypotension sympathetic Blockade∝– BradycardiaUnopposed vagal tone †, Frank-Starling law ‡, hypotension
Physiological Effects of Spinal Anesthesia
• Respiratory effects:• Inspiratory muscles are barely affected †• No effect on pulmonary function or gas exchange• Respiratory arrest: high levels of drug leading to brain
ischemia due to hypotension
• GIT • Increased secretions• Relaxation of sphincters• Hyperperistalsis can cause N/V• Mucosal damage‡
Physiological Effects of Spinal Anesthesia
• Renal Effect• Non-significant, minimal reduction in renal blood flow
and urinary retention
• Reduction of Stress Response to Surgery• Reduced catecholamines, anti-diuretics and
hyperglycemic response
Factors Increasing the Level of Spinal Block
• Dosage• Increased intra-abdominal pressure and
pregnancy |• Site and rate of administration †• Position (lateral, head down) and coughing• Barbotage• Baricity ‡
Indications & Contraindications
• Same as those for epidural• Except that it’s not used for the relief of
chronic pain or post-dural puncture headache
Complications of Spinal Anesthesia
Intra-operative• Failure• Broken needle• N/V• Bradycardia• Hypotension• Cardiac arrest• Total Spinal• Hypothermia
Post-operative• PDPH• Backache• CN VI palsy• Urinary Retention• Meningitis• Neurological sequalae• Spinal hematoma
RELATED CONDITIONSTSA, PDPH and CES
TSA
• Cause: spread of the LA to the cervical area and brain stem
• S/Sx: profound hypotension, bradycardia, N/V, LOC, dilated pupils, apnea
• Rx: – EARLY RECOGNITION!– IV colloids and vassopressors– Intubation and mechanical ventilationNote: the patient is still awake, so sedate.
PDPH
• Cause: decreased CSF pressure secondary to leak, leading to traction on the meninges and CN’s
• S/Sx: intense headache (frontal/occipital) and neck pain worse in upright position, diplopia and blurred vision.
• Usually 24-72 hours post puncture• Higher incident in women, less in elderly and
when smaller needles are used
PDPH, Rx
Preventive• Using smaller needles• Inserting the needle bevel
parallel to fibers• Maintain adequate
hydration
Curative• In 80%, no treatment is
needed• Keep the patient flat in bed
and give analgesics• Epidural blood patch• Epidural fibrin glue from the
meninges
CES
• Cause: trauma from puncture, spinal or epidural hematoma, abscess or ischemia
• S/Sx: refer to your neurology text• Rx:– EARLY RECOGNITION!– Decompression of hematoma (elimination of the cause)
• Complications: chronic adhesive arachnoiditisNote: the syndrome, as well as its complications are
extremely rare
Read About These
• Differences between spinal and epidural anesthesia
• Combined spinal-epidural anesthesia• Difference between epidural anesthesia and
analgesia
References
• Anesthesia for Medical Students, 1st edition• Clinical Anesthesia Lecture Notes, 4th edition• Toronto Notes 2016, 32nd edition• Netter’s Clinical Anatomy, 3rd edition• Nucleus Medical Media Channel, YouTube