Anaesthesia And Pain

Nociceptors

Subjective, unpleasant sensory and emotional experience and is a protective mechanism. Memory of pain can help avoid future harmful events

Lasts more than 6 months, exaggerated afferent pain impulses or permanent sensitised dorsal horn or a poor descending pathway

Stimulus providing detecting by nociceptors, generation of an action potential and receptors reach the spinal cord via the dorsal root which synapses with the dorsal horn and ascends to the brain via thalamus and somatosensory cortex

Induction - inducing unconsciousness Maintenance - homeostasis and anaesthesia Emergence - unconscious - concious Recovery

Suppression of physiological responses to painful stimuli

Administration of meds that block feeling of pain / deep state of unconsciousness. Relieve pain and support physiological functions during a procedure

Induces absence of pain locally by injecting around a nerve / trunk to provide anaesthesia in the peripheral nervous system, inhibits excitation conduction process

Lack of awareness, Amnesia, Analgesia and Akinesia

Benzodiazepines - hypnotics /sedatives to relieve anxiety Analgesics - morphine/panadol/NSAIDS Anticholinergics - reduce saliva control/bradycardia/ antiemetic to reduce pop nausea Antis - reduce wound infection

An inhibitory neurotransmitter widely distributed in the CNS. Neuronal activation - GABA released to synapse and acts on post synaptic GABA receptors Thiopentone - mimics GABA - depresses excitatory neurotransmission

Acts on specific GABAa receptor to shorten channel opening times at nicotine’s ACh receptors - rapid induction

Glutamate receptor antagonist, interacts with Nictotinic ACh receptors and voltage gated CA channels

Face mask - alveolar capillary membrane- circulation. Binds to lipid layer of cell membranes to cause small expansion/swelling to distort ion channels - inhibiting excitatory brain and spinal cord activity

Desflurane Isoflurane Sevoflurane N20 All are triggers of malignant hyperthermia

Inhaled agents

myelinated delta fibres in response to mechanical and thermal pain unmyelinated C fibres (slow pathway) in response to chemical, slow burning

Substance P - activates ascending pathway to brain and Glutamate - neurotransmitter on dorsal horn, causes permeability changes to allow ca entry to dorsal horn = increased excitability. Opioids receptor inhibits at the afferent pain fibre synapse

inhibits pain transmission, endogneous opioids are released which inhibit substance p release and block the pain impulses to the brain

inhibit afferent pathway, activate descending pathway and inhibit excitation of sensory nerve terminals.

proposes how pain is reduced by activating a nonpainful sensation by the alpha delta smaller sensory nerve, decreasing pain in the dorsal horn. E.g rubbing a painful area

proposes how pain is reduced by activating a nonpainful sensation by the alpha delta smaller sensory nerve, decreasing pain in the dorsal horn. E.g rubbing a painful area

Mild pain - Non opioid, paracetomol, NSAID Mod Pain - Weak opioid & non-opioid Severe pain - strong opioid

Desflurane, Isoflurane, Sevoflurane, - act on alveolar-capillary membrane to enter systemic, crosses BBB (lipophillic) to distort ion channels and inhibit excitatory activity in CNS