DR S NAIDOO
ANAESTHESIOLOGY
KALAFONG
WHAT IS PAIN?
 Not only sensory
 Unpleasant and emotional experience
 Associated with tissue damage
NOCICEPTION
 Latin for damage or injury
 Only refers to the neural response to
injury
 All nociception causes pain
 BUT
 Other things also cause pain!!!
 Nociception causes ACUTE PAIN –
nociceptive pain
 Nociception and psycho-behaviouristic
factors cause CHRONIC PAIN –
neurogenic pain
THE
BASIC
PAIN
PATHWAY
 Tissue injury stimulate free nerve endings
 NOCICEPTORS
 Afferent nerve fibres (A∂ and C) conduct
stimuli centrally
 Peripheral afferents project into the
DORSAL HORN and other areas in the
SPINAL CORD
 SYNAPSES extend over to the
SPINOTHALAMIC TRACT and up to the
THALAMUS and to the CEREBRAL
CORTEX
FACTORS RESPONSIBLE
 PERIPHERAL MODULATION
 Locally secreted substances
 Sensitises the nociceptors
 Site of action for NSAIDs,
glucocorticoids, opioids
 SPINAL MODULATION
 Neurotransmitters like glutamate,
aspartate and substance P
 SUPRASPINAL MODULATION
 Descending inhibition in the dorsal
horn
 These inhibitory tracts are opioid and
ἀ-adrenergic
 COGNITIVE MODULATON
 Distraction of attention
 Therefore appropriate treatment agents
best suited for various types of pain can
be determined from causative agents
PAIN
 Requires treatment
 Accompanied by unwanted side effects
 Acute pain untreated adequately becomes
chronic in nature and even more difficult to
treat
 And has a high morbidity
SO…WHY TREAT PAIN?
SIDE EFFECTS OF PAIN
PULMONARY
Hypoventilation, hypoxaemia,
pneumonia
CARDIOVASCULAR
Hypertension, dysrhythmias,
myocardiaI ischaemia and cardiac
failure
GASTRO-INTESTINAL
Decreased motility
GENITO-URINARY
Urine retention
BLOOD CLOTTING
Decreased mobility prone to DVT
IMMUNOLOGICAL
Immunosuppression
ENDOCRINOLOGICAL
Stress response, decreased anabolism,
increased catabolism. Na and H2O
retention
NON-OPIATES
NSAIDS AND PARACETAMOL
Useful when prostaglandins contribute to the
injury
ASPIRIN
IBOPROFEN
DICLOFENAK
KETOROLAC
PARACETAMOL-CODEINE
COMBINATIONS
 ἀ₂ AGONISTS
 KETAMINE – 0,25mg/kg
 REGIONAL ANAESTHESIA
 The only way to blunt the afferent
sympathetic influence therefore the
stress response
 Analgesia for hours
momor
OPIOID RECEPTORS
 3 MAIN CLASSES
 Mu main pharmacological effects of morphine
analgesia, dependence & resp depression
 Kappa analgesia, resp depression, gastrointestinal
effects
 Delta
RECEPTOR PROFILE
 ANTAGONISTS
 FULL OR PARTIAL AGONISTS
CENTRAL EFFECTS OF OPIOIDS
 Analgesia
 Anaesthesia
 Muscle rigidity
 Pupils
 Thermoregulation
 Euphoria
OPIOIDS
 Drugs of choice for the treatment of
severe pain
 Patients do not get addicted to opioids,
they become tolerant
 Besides analgesia, opioids are sedating,
suppress ventilation, alleviates
coughing and can cause bronchospasm
EXAMPLES OF OPIOIDS
 NATURAL OCCURRING
 MORPHINE, CODEINE
 PAPAVERINE, NOSCARPINE
 SYNTHETIC
 PHENYLPIPERIDINES eg fentanyl, sufentanil, etc
 PENTAZOCINE, BUPRENORPHINE
CARDIOVASCULAR
 DECREASED SYMPATHETIC
OUTFLOW
 HISTAMINE RELEASE – CVS
COLLAPSE
 BLUNTS THE
SYMPATHETIC RESPONSE
TO INTUBATION
RESPIRATORY SYSTEM
 DECREASED SENSITIVITY TO AN
INCREASED PaCO₂
 HYPOXIC DRIVE DECREASES
 CHEST WALL RIGIDITY
 BLUNTS THE RESPONSE TO
INTUBATION
 BRONCHOSPASM
CENTRAL NERVOUS SYSTEM
 REDUCED CEREBRAL O₂
CONSUMPTION, BLOOD FLOW AND
INTRACRANIAL PRESSURE
 LITTLE EEG CHANGES
 MIOSIS
 STIMULATES THE CETZ
GASTROINTESTINAL SYSTEM
 DECREASED GASTRIC EMPTYING
 SPASM OF THE SPHINCTER OF
ODDI
 CONSTIPATION
ENDOCRINE SYSTEM
 DECREASED RELEASE OF STRESS
HORMONES
 ATTENUATES THE INTUBATION
RESPONSE
OTHER SIDE EFFECTS OF OPIOIDS
 NAUSEA
 VOMITING
 CONSTIPATION
 PRURITIS
 URINE RETENTION
 HISTAMINE RELEASE
 CHEST WALL RIGIDITY
 The application of several modalities to
alleviate pain
 Used in combination with regional
anaesthesia
 Administration of analgesia BEFORE
surgery
 Found to be less effective in man than
animal
 Including nerve blocks with or without
 Infusions of local anaesthesia
 Neuraxial blocks (spinal, epidural
block and paravertebral blocks)
 Patient controlled analgesia
Nerve Blocks
Neuraxial Blocks
Patient controlled analgesia
So... Please remember:
PAIN IS NOT AN OPTION WHEN
WE AS PHYSICIANS HAVE SUCH
A WIDE RANGE OF MODALITIES
TO TREAT IT!