Postoperative Pain Managementmedinfo.psu.ac.th/nurse/paper_meeting/ortho/ortho3.pdf · The...
Transcript of Postoperative Pain Managementmedinfo.psu.ac.th/nurse/paper_meeting/ortho/ortho3.pdf · The...
Postoperative Pain Management
Nimmaanrat S, MD, FRCAT, MMed (Pain Mgt)
Topics to be Covered
Definition
Neurobiology
Classification
Multimodal analgesia
Preventive analgesia
Step down approach
Measurement
Methods of treating postoperative pain (various routes)
Patient-controlled analgesia (PCA)
Non-opioids
Weak opioids
Strong opioids
Regional analgesia
Pain
“An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage”
Neurobiology of Pain
Descartes (Cartesian)’s Model of Pain
Classification of Pain
Acute
Chronic
Duration
Nociceptive
Neuropathic
Pathophysiology
The Continuum of Pain
<1 month
Time to resolution
3-6 months
Acute Chronic
• Usually obvious tissue damage
• Increased nervous system activity
• Pain resolves upon healing
• Serves a protective function
• Pain for 3-6 months or more
• Pain beyond expected period of
healing
• Usually has no protective function
• Degrades health and function
Insult
Progression from Acute to Chronic Pain
Incidence of Chronic Pain after Surgery
Amputation
Thoracotomy
Mastectomy
Cholecystectomy
Inguinal hernia
Vasectomy
Dental surgery
30 - 85 %
5 - 67 %
11 - 57 %
3 - 56 %
0 - 63 %
0 - 37 %
5 - 13 %
Risk Factors for Chronic Postsurgical Pain
Preop factors Pain, moderate to
severe, > 1/12
Repeat surgery
Psychologic vulnerability
Workers’ compensation
Intraop factors Surgical approach with
risk of nerve damage
Postop factors Pain (acute,
moderate to severe)
Radiation to area
Neurotoxic chemotherapy
Depression
Psychologic vulnerability
Neuroticism
Anxiety
Adverse Consequences of Uncontrolled Postoperative Pain
Physiological effects
Psychological effects
Physiological Adverse Effects
Increase sympathetic activity
Increase risk of MI
Decrease GI motility (ileus)
Increase incidence of pulmonary complications (atelectasis, hypoxia)
Suppress immunity
Psychological Adverse Effects
Receive less attention than those asso. w chronic pain
But not less important
Failure to control postop. Pain
Anxiety
Insomnia
Inability to think and interact w others
etc.
Postoperative Pain Management
Multimodal analgesia
Preventive analgesia
Step down approach
Multimodal Analgesia
Clinically Meaningful Adverse Events – CMEs
The incidence of clinically meaningful adverse events is dose-related (level II)
Preventive Analgesia
Step Down Approach
Measurement of Pain
Pain Measurement
Pain is a subjective, personal experience
The logical and true assessment of pt’s pain must therefore be pt’s own report
Self report is gold standard
Unidimension
Multidimensions
Unidimensional Tools
Categorical scales
Numerical rating scales (NRS)
Visual analog scales (VAS)
Picture scales / pain drawings
Methods of Treating Postoperative Pain
Methods of Treating Postoperative Pain
Traditional administration of opioids
Parenteral administration of opioids
Non-parenteral administration of opioids
Local anesthetic techniques
Non-opioid analgesics
Non-pharmacological methods
Parenteral Administration of Opioids
Bolus IV administration
Continuous IV infusion
Patient-controlled analgesia (PCA)
Bolus IV
Bolus + infusion
Subcutaneous
Non-parenteral Administration of Opioids
Sublingual
Oral
Transmucosal
Rectal
Transdermal
Nasal
Inhalation
Intra-articular opioids
Non-opioid Analgesics
Non-steroidal anti-inflammatory drugs (NSAIDs)
Selective COX-2 inhibitors (COXIBs)
Paracetamol
NMDA antagonists
Central α2-adrenergic agonists
Patient-controlled Analgesia (PCA)
Patient-controlled Analgesia (PCA)
Patient-controlled Analgesia (PCA)
Advantages of PCA
Non-parenteral Opioid Administration
Non-parenteral Administration of Opioids
Sublingual
Oral
Transmucosal
Rectal
Transdermal
Nasal
Inhalation
Intra-articular opioids
Sublingual Opioids
Cooperation required
No need for painful injections
Popular for pts
Convenient for nurses
Buprenorphine
Partial agonist / ceiling effect
Oral Route
All opioids undergo extensive first-pass metabolism
Low oral bioavailability (20-30%)
Immediate postop. period : invariably reduction of gastric emptying
Oral Route
Absorption may be delayed, with poor analgesia
If given on regular basis : a danger of a large dose being propelled into upper GI tract when gastric motility returns to normal
Over dosage
Ventilatory depression
Transmucosal Route
Premedication in children
Onset of pain relief : 9/60
Rectal Route
Bioavailability varies according to site of suppository
Venous blood from lower part of rectum drains directly into systemic circulation
But upper part drains into portal circulation
Inhaled / Intranasal Route
Intranasal spray devices for fentanyl
Metered inhalers with improved pulmonary drug delivery systems and lockout times
Future : may allow noninvasive PCA administration
Pharmacological Approach
Classification of Pain Medications
Non-opioid analgesics
Opioid analgesics
Adjuvants
Paracetamol
Paracetamol (Acetaminophen)
Effective analgesic with antipyretic activity
Does not inhibit COX in peripheral tissues -> lack of anti-inflammatory activity
Mechanism of analgesic action remains unclear
Paracetamol
Generally well tolerated
Most serious adverse effect of acute overdosage is a dose-dependent
(150 mg/kg), potentially fetal, hepatic necrosis
Insufficient glutathione (liver disease, alcohol consumption> 3 units/day, malnutrition etc.)
NSAIDs
Mechanisms of Action
Selective COX-2 Inhibitors (COXIBs)
COXIBS
COX-2 is constitutively expressed in kidney
Maintenance of renal blood flow
Mediation of renin release
Regulation of Na+ excretion
COXIBs & NSAIDs have similar renal adverse effects
↑ed risk in pre-existing renal impairment,
hypovolumia, hypotension, use of
nephrotoxic agents & ACEIs
COXIBs
The pharmacological class of COXIBs appears to be associated with an increased risk of CV adverse events
The CV risks may increase with dose & duration of exposure
The shortest duration possible & the lowest effective daily dose should be used
COXIBs
Must not be used in pts with established
Ischemic heart disease
Cerebrovascular disease
Peripheral arterial disease
To exercise caution in pts with risk factors of heart disease
Hypertension
Hyperlipidemia
DM
Smoking
Opioids
Classification of Opioids
Weak opioids (mild - moderate pain)
Strong opioids (moderate - severe pain)
Weak Opioids
Codeine
Tramadol
Codeine
Classic weak opioid
Potency 1/10 of MO (CYP2D6, MO)
30-120 mg q 4/24
Dose limiting side effects (constipation, N/V,
confusion)
Fixed combination
Paracetamol vs Paracetamol plus Codeine
Tramadol
Dual-acting analgesic
Tramadol & M1 (CYP2D6) have affinity at
μ-opioid receptors
Also inhibits reuptake of serotonin &
noradrenaline
Potency 1/20 – 1/5 of MO
Tramadol
Max 400 mg/day
Max 200 mg/day in pts with hepatic /
renal impairment
Tramadol Retard (12/24)
Less sedation & constipation
Unfortunately, N/V frequently reported
Strong Opioids
Morphine
Pethidine
Fentanyl
Strong Opioids
Mainstay for the Rx of moderate to severe pain
Interpatient requirements vary greatly
Doses need to be titrated to suit each pt
In adults, age rather than weight is the predictor of requirement
Strong Opioids
All full agonists given in equianalgesic doses produce the same analgesic effects & side effects
One opioid is not superior over others but some are better in some pts (level II)
The incidence of clinically meaningful adverse effects is dose – related (level II)
Pethidine should be discouraged
Opioids
Assessment of sedation level is a more reliable way of detecting early opioid-induced respiratory depression
Morphine
M3G & M6G are main metabolites, excreted via kidney
M6G
Opioid agonist
May potent than morphine
M3G
No analgesic activity
May antagonise analgesic effect
May cause hyperalgesia, allodynia & muoclonus
Pethidine
Widely used even though it has multiple disadvantages
Despite common belief that it is the most effective opioid in treatment of renal colic, it is no better than morphine
Pethidine & morphine have similar effects on sphincter of Oddi & biliary tract
No evidence that pethidine is better
in the treatment of biliary colic
Norpethidine
Metabolized in liver to several inactive compounds and norpethidine
Accumulation leads to neuroexcitatory
Nervousness
Tremors
Twitches
Multifocal myoclonus
Seizures
Pethidine / Norpethidine
Impaired renal function → ↑ half-life of
norpethidine
Patients in renal failure are at ↑ed risk of
norpethidine toxicity
Naloxone not reverses & may ↑ norpethidine
toxicity
Overall, the use of pethidine should be discouraged in favor of other opioids
Fentanyl
High lipid solubility
Potency 100X of morphine
Lack of active metabolite
Fast onset
Short duration of action
Guideline for Postoperative Pain Management
(Example)
Regional Analgesia
Epidural Analgesia
Peripheral Nerve Block
Ultrasound-guided Peripheral Nerve Block
supraclavicular brachial plexus block
Peripheral Nerve Block
Single shot
Continuous infusion