PERI-OPERATIVE PAIN MANAGEMENT Dr P Chalmers CP4004 2010 - 2011.
-
Upload
randall-dickerson -
Category
Documents
-
view
215 -
download
1
Transcript of PERI-OPERATIVE PAIN MANAGEMENT Dr P Chalmers CP4004 2010 - 2011.
IASP definition
“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”
Mechanism of Pain
Cell Injury→Cytokines,prostanoids→Plasma
Leakage→macrophages, monocytes, mast cells, platelets→Cytokines,prostanoids→
nociceptive nerve endings (C and Aδfibres)
IASP definition
“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”
Process of Nociception
1. Transduction conversion of pain stimulus into a nerve impulse by sensory receptors
2. Transmission of nerve impulses from the periphery to the brain and spinal cord
3.Perception the recognition of these impulses or signals as pain
4.Modulation whereby descending neuronal tracts from the brain modify the nociceptive transmission in the spinal cord
Opioid system, noradrenergic, GABA, serotonin
Effects of PainNeurohumoral
• Psychological Anxiety• Resp:hypoventilation →hypercarbia and hypoxia hyperventilation• CVS: tachycardia, hypertension, subendocardial
ischaemia• Nausea and vomiting• Sweating• Increased stress response → catabolism
• Outcome:• Prolonged immobilisation and recovery• Prolonged hospital stay
Effects of Analgesia
• Reduces anxiety and stress response• Reduces respiratory complications• Reduces cardiovascular complications• Reduces autonomic effects
• Outcome:• Earlier mobilisation• Shorter hospital stay
Factors influencing pain
• Age
• Site of surgery
• Quality of care
• Patient autonomy
• Patient motivation
Assessment of pain
Intraop: Monitoring CVS, RS
Postop:• Visual cues facial expression body language• Psychological anxiety, restlessness, withdrawal• Verbal response• VAS• Imagery• Universal
Why multimodal
• Synergism
• Opioid sparing
• Reduced risk of tolerance and morphine sensitisation
• Reduced side effects and complications
• Pre-emptive
Advantages and disadvantages of im v PCA administration
IM PCA
Delayed onset Rapid onset
Fixed dose Dose matches pain
Painful Painless
Fluctuating plasma levels Continuous plasma levels
Gradual onset of Technical error or failure
side effects may be fatal
Enhances patient autonomy
Neural Blockade
Neuroaxial: Spinal
Epidural
Regional Blockade
Skin Infiltration
Local anaesthetics
Adjuvants
Requirementsfor Neural Blockade
• Consent
• Sterile condition
• Vascular access
• Monitoring
• Resuscitation equipment
• No clinical contraindications (coag,infections,allergies)
Effects of Neural Blockade
• Sensory Loss
• Muscle Paralysis
• Autonomic Effects (spinal, epidural)
ALWAYS aspirate before injection
beware of accidental intravascular administration
Complications Neuro-axial Block(spinal/epidural)
• Hypotension• Backache• Spinal cord/nerve root compression
(haematoma/abscess)• Dural headache (epidural)• Overextensive block • Total Spinal Block • Accidental Intravascular injection• Side Effects of drugs LA’s Opiods
Advantages of epidural analgesia
• Excellent analgesia for 72hrs or longer
• Avoids side effects of opiods
• Improves postop respiratory function
• Reduces thromboembolic phenomena
• Reduces incidence of persistent post surgical pain
Local anaesthetics
• Lignocaine
• Bupivicaine
• Levobupivicaine
• www.4um.com/tutorial/anaesth/Locals.htm
Lignocaine Bupivicaine
Onset of Action Fast Medium
Pka 7.9 8.1
% unionised 25 15
Weak bases mostly ionised at pH 7.4
Lignocaine Bupivicaine
Duration of action medium Long
% protein bound 70 95
Vasoactivity Dilatation at lo doses ++
Constriction at hi doses+
Dilatation at lo doses +
Constriction at hi doses++
Lignocaine Bupivicaine Laevo-bupivicaine
Onset of action
2-4 min
rapid
10 min
Duration 30-90min
medium
3-7hrs (16hrs)
Long
3-7hrs (16hrs)
Dosage 3mg/kg/4hrs
(adr 6mg/kg)
2mg /kg/4hrs
(adr 2 mg/kg)
Max dose 150mg; 400mg/24hrs
Local anaesthetics
Adrenaline 1:200,000=5micrograms/ml
Never used in spinals and epidurals
Max dose 8ug/kg/hr = 20mls of 1in 200,000/hr
Lignocaine Bupivicaine Laevo-bupivicaine
Toxic plasma conc ug/ml
>5 >1.5
Toxicity CNS +++ Cardiac +++
Cardiac +
Management of toxicity
• R/Lipid emulsion 20% a bolus of 100mls followed by an infusion of 400mls over 20min (approx 0.25mls /kg/min) Repeat if necessary
• PLUS supportive measures anticonvulsants, inotropes etc
Adjuvants in neural blocks
• Opiods→pruritus,delayed onset resp depression, nausea, vomiting
• Clonidine
Pain Syndromes
• Sensitisation occurs in response to repeated or prolonged noxious stimuli: lower activation threshold ,increased rate of firing
a. peripheral: Increased sensitivity and excitability of nociceptive receptors and damaged nerves
b.central: hyperexcitability of spinal neurones and descending modulating pathways
Activation of NMDA receptors
Pain Syndromes
• Opioid Induced Hyperalgesia : the use of opioid paradoxically increases the patient’s perception of pain excitatory descending modulating pathways
• Persistent Post Surgical Pain Syndrome The response outlives the initiating stimulus and lasts for 3 months or more
Risk Factors • History of poorly controlled pain (preoperatively and perioperatively)• Intraoperative nerve damage (surgical, anaesthetic)• History of preoperative neuropathic pain• Co-morbidities associated with neuropathy:Diabetes, alcohol abuse, uraemiaDrug induced neuropathyNutritional deficiency,vitB12, B6,• Malignancy• Chem/radiotherapy• Impaired immune system• Fibromyalgia• Major trauma• Depression/anxiety (the unemployed)
Prevention of Pain Syndromes
• Efficient and effective pain management in the perioperative period
• Multimodal analgesia with neuroblockade regular acetaminophan and Nsaids and opioids
• On going research regarding perioperative use of antihyperalgesic agents:
Pregabalin gabapentin NMDA receptor antagonists eg Ketamine Alpha agonists eg clonidine