Intrathecal Narcotics for Postoperative Analgesia

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Intrathecal Narcotics for Post-operative Analgesia

• Kristopher R Davignon, MD
• Dept of Anessthesia Grand Rounds
• March 2007

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Intrathecal Narcotics

• Opioids were know to the ancient Sumerians as of
  4000 B.C.
• 1971 Opioid receptor discovered
• 1973 Receptors found in the brain
• 1976 Receptors found in the spinal cord
• 1979 Early reports of intrathecal opioids
  producing analgesia

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Intrathecal Narcotics

• Thoracic and Upper Abdominal Procedures
• Elective Total Hip Arthroplasty
• 350,000 Procedures per year in the US
• 5 min to consent
• 15 min for procedure

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Overview and Goals

• Anatomy, Physiology Pharmacology
• Complications
• Evidence Based Practice
• Dose-Response
• Future Directions

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Anatomy, Physiology Pharmacology
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Anatomy, Physiology Pharmacology

• Drug disposition depends primarily on lipid
  solubility
• Any drug rapidly redistributes
• opioid is detectable in the cisterna magna within
  30 min of lumbar intrathecal administration

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Anatomy, Physiology Pharmacology

• Opiods
• Morphine
• Meperidine
• Hydromorphone
• Sufentanil Fentanyl
• Methadone

• Non Opiods
• Clonidine
• Neostigmine
• Adenosine
• Epinephrine
• Ketorolac
• Midazolam

Preservative
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Anatomy, Physiology Pharmacology

• Lipophilic opioids
• Rapidly traverse the dura sequestered in
  epidural fat (and enter systemic circulation)
• Rapidly penetrate the spinal cord and bind
  receptors and nonspecific sites

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Anatomy, Physiology Pharmacology

• Hydrophilic opiods
• Limited binding to epidural fat and nonspecific
  receptors
• Slower transfer to systemic circulation
• Higher CSF concentrations accounting for rostral
  spread

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Anatomy, Physiology Pharmacology
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Complications

• Pruritus
• Mechanism unclear likely opiod receptor
  mediated (not histamine)
• Incidence 30-100
• Rx Antihistamines, 5-HT3 antagonist, opiod
  antagonists (or agonist-antagonists), propofol

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Complications

• Urinary Retention
• Not dose dependent
• Can last 14-16 hours
• Most frequent with Morphine
• 35 incidence
• Mechanism related to sacral parasympathetic
  outflow inhibition
• Allows increase in maximal bladder capacity

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Complications

• Nausea and Vomiting
• Incidence 30
• Most profound with Morphine
• Likely due to cephalad migration of drug to area
  postrema

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Complications

• Respiratory Depression
• Incidence is dose dependent
• Very Rare 0.09 to 0.4
• Likely no more clinically relevant than for IV
  narcotics
• Monitoring for 18-24 hours when using lipophilic
  opiods

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Complications

• PDPH
• Age, Gender, History of PDPH, Obesity
• Multiple dural puncture, Needle size, Needle
  design

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Complications

• PDPH
• Rx
• hydration
• Caffeine
• Sumatriptan
• ACTH
• EBP

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Complications

• Neuropraxia/Paralysis
• Epidural hematoma
• Epidural abcess

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Evidence Based Practice

• What types of surgery is amenable to intrathecal
  narcotics?
• What doses should we use?
• What outcomes can we affect?

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Types of Surgery

• Thoracic
• Including Cardiac
• Intra-abdominal
• Including C/S, AAA, Open Cholecystectomy
• Lower Extremity
• Including THA TKA

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• Narcotic Only (worst)
• Narcotic LA (best)
• LA Only

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the Dose

• 1) Optimal dose depends on the surgical procedure
• 2) Incidence of side effects increases in
  proportion to dose (especially with doses gt 300
  ug)

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the Dose
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Dosing for THA

• Use lowest dose possible!
• Studies have used doses as low as 0.025 mg
• Older studies used doses as high as 0.5mg
• Ideal dose seems to be 0.1 mg
• Lower doses dont provide good analgesia
• Higher doses plagued with pruritis

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Dosing for THA
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Dosing for THA
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Affecting Outcomes
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Do Improved Pain Scores Matter?
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Future Directions

• Anticoagulants
• Use of stents and anti-platelet agents
• Aggressive DVT prophlaxis
• Absence of laboratory evidence of these agents
• Sustained release neuraxial narcotic
• Depodur

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Future Directions

• Depodur (morphine sulfate extended release
  liposome injection)

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Future Directions
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Future Directions

• Better Pain Scores for 48 hours
• Studied in Hip Arthroplasty, Cesarean Section,
  Lower Abdominal Surgery
• No significant difference in side effects from IV
  narcotic

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Conclusions

• Pain management in the in-patient setting is
  becoming a priority for adminstrative
  organizations
• A majority of in-patient pain management is
  post-operative
• Neuraxial narcotics consistently reduce patients
  VAS