Introduction Definitions acute pain implies presence of tissue damage chronic pain (3-6 months) no implication of tissue damage necessary pathologic pain pain from abnormal nervous system functioning (neuropathic) Pathophysiology afferent pain pathways nociceptors transduce signal through various substances Substance P a sensory neurotransmitter that plays an important role in pain depletion of substance P increases the threshold to painful stimuli Capsaicin is thought to function by decreasing Substance P peripheral nerves nociceptors transmit pain to type A and C peripheral nerve fibers spinal cord peripheral nerves transmit the pain signal via the dorsal column and spinothalamic tract brainstem spinal cord transmits the pain signal to the thalamus site of pain modulation with endogenous opiates Agents (details below) Acetaminophen NSAIDS Opiates Gaba synthesis agents Adjunctive agents Indications & Special Consideratoins Pediatric patients follow specific dosing guidelines for children which have been tested and recommended by the American Academy of Pediatrics Geriatric patients may have increased sensitivity to opioid pain medicines with higher rates of side effects decreased total body mass with increased body fat percentage potentially decreased hepatic and renal function Obese patients achieving adequate peri-operative pain control in the morbidly obese can be difficult the most accurate method to control pain and avoid respiratory depression should include patient controlled analgesia (PCA), which is based on the patient's ideal weight intramuscular injections should be avoided due to the difficulty of avoiding injection into muscle and the poor vascularity of the subcutaneous adipose tissue Red-haired patients often require more anaesthesia to maintain MAC levels and higher opioid dosages postoperatively compared to other hair types Chronic regional pain syndrome Vitamin C has been shown to possibly prevent CRPS specifically related to distal radius fractures Acetaminophen Mechanism not fully understood inhibits prostaglandin synthesis minimal antinflammatory effects As effective for pain control as aspirin Toxicity overdose leads to hepatic disfunction contraindicated in the setting of pre-existing hepatic dysfunction NSAIDs Mechanism decrease transduction of pain See anti-inflammatory medications Local anesthetics Mechanism decrease transduction of pain interfere with nerve conduction to provide a reversible loss of sensation in a specific location affects the depolarization phase of action potentials (cells fail to depolarize enough to fire after excitation leading to a blocked action potential) Examples amide family lidocaine (Xylocaine) bupivacaine (Marcaine) esters of p-aminobenzoic acid procaine (Novocain) butethamine (Monocaine) esters of meta-aminobenzoic acid cyclomethycaine (Surfacaine) metabutoxycaine (Primacaine) esters of benzoic acid cocaine ethyl aminobenzoate (Benzocaine) Adverse effects FDA warning on the administration of continuous intra-articular infusion of local anesthetics for pain control Some patients have been noted to have chondrolysis following infusion Opiates Overview useful in chronic nociceptive pain Mechanism perispinal method affects modulation of pain systemic opiates change the perception and modulation of pain Administration oral, IV, intraspinal oral administration preferred (more convenient and less costly) bony procedures require more analgesia than soft tissue procedures patient compliance can improve with long-acting preparations that providue more uniform serum drug levels implantable systems are available for intrathecal administration Prescription dosing guide for upper extremity surgery no narcotics trigger finger release, nonop Dupuytren's release, small lumps/bumps 10 narcotic tablets mucous cyst, carpal tunnel, deQuervain’s, Dupuytren’s releases and small joint fusion 20 narcotic tablets wrist ganglion cysts, hand fracture ORIF, LRTI and tendon transfers 40 narcotic tablets large trauma, wrist fusion, open carpal surgery and DRUJ reconstruction Chronic use addiction occurs in a minority of patients chronic opiates should be prescribed by pain management specialists written contracts should be obtained prescriptions should always be refilled in person Methadone Synthetic diphenylheptaine-derivative opioid receptor agonist High bioavailability (three times as much as morphine), effective, and inexpensive Metabolism cytochrome P450 system Rapid distribution phase (2-3 hours) and prolonged elimination phase (15-60 hours) Caution can accumulate to high levels with repeated dosing rates of elimination vary considerably risk of respiratory depression, cardiac toxicity (torsades de pointes) consult with a qualified pain specialist when prescribing for the first-time GABA agents Agents Pregabalin (Lyrica) Gabapentin (Neurontin) Mechanism decrease transduction of pain reduce hyper-excitability of voltage dependent Ca2+ channels in activated neurons. Gabapentin is an anticonvulsant also used to treat neuropathic pain binds presynaptic calcium channels to inhibit release of neurotransmitters Efficacy evidence of effectiveness primarily for postherpetic neuralgia, diabetic nueropathy, and fibromyalgia little evidence for other uses, though often prescribed for other forms of chronic neuropathic pain (such as complex regional pain syndrome, CRPS) gabapentin has been shown to be as effective and less expensive than pregabalin Discontinuation requires a tapering dose Muscle relaxants Overview Useful to treat pain secondary to muscle spasms Agents Cyclobenzaprine (Flexeril) mechnism of action not fully understood centrally acting potentiates norepinephrine and binds serotonin receptors Use may decrease pain during first two weeks after an injury no proven benefit after first two weeks may be effective for fibromyalgia not effective to reduce spasticity secondary to neuromuscular disorders Toxicity overdose rare may interact with other substances MAOIs alcohol Adjuvant agents Heterogeneous class of medications the provide additive analgesic effect to traditional NSAIDs and opioids anticonvulsants antidepressants antihistamines psychostimulants anti-spasmodics
QUESTIONS 1 of 6 1 2 3 4 5 6 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ08.249) What is the most appropriate delivery route for pain medication to a morbidly obese post-operative patient to ensure a therapeutic plasma concentration? Review Topic QID: 635 1 Oral tablets 4% (48/1297) 2 Oral liquid solution 1% (7/1297) 3 Subcutaneous injections 1% (14/1297) 4 Intravenous patient controlled analgesia based on actual body weight 40% (522/1297) 5 Intravenous patient controlled analgesia based on ideal body weight 54% (702/1297) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 5 (OBQ11.226) A 35-year-old male presents with pain and limited range of motion 3 months after arthroscopic Bankart repair of his right shoulder. His postoperative course included a continuous intra-articular infusion pump for 3 days, use of a sling for 4 weeks, and initiation of passive range of motion below the level of the shoulder. At 4 weeks postoperatively he started active range of motion exercises, and started an isotonic strengthening program at the 9 week interval. Which of the following options is the MOST appropriate step in his management? Review Topic QID: 3649 1 Reassurance and appropriate followup 10% (162/1666) 2 Focused physical therapy on aggressive ROM exercises and modalities 26% (427/1666) 3 Intra-articular injection of corticosteroids to decrease post-operative inflammation 3% (46/1666) 4 Shoulder radiograph series to assess for chondrolysis 60% (998/1666) 5 Arthroscopic vs open Bankart revision surgery for failed repair 1% (23/1666) ML 3 Select Answer to see Preferred Response PREFERRED RESPONSE 4
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