INTRODUCTION TO ANESTH / PAIN & PATHWAY

anesthesiology

the medical specialty concerned with the total perioperative care of patients before, during and after surgery

it encompasses anesthesia, intensive care medicine, critical emergency medicine, and pain medicine

the core element of the specialty is the study and use of anesthesia and anesthetics to safely support a patient's vital functions through the perioperative period

perioperative period

the time period of a patient's surgical procedure

commonly includes ward admission, anesthesia, surgery, and recovery

a term which is often specifically utilized to imply 'around' the time of the surgery

the primary concern is to provide better conditions for patients before operation (sometimes construed as during operation) and after operation

3 phases of surgery

preoperative

intraoperative

postoperative

anesthesiologist / anaesthesiologist / anaesthetist

a physician specialized in this field of medicine is called an _____

medical professionals who can administer anesthesia

anesthesiologist

anesthetist

surgeons

physicians

dentists

veterenarians

types of anesthesia

general anesthesia

regional anesthesia

local anesthesia

sedation

general anesthesia

method of medically inducing loss of consciousness

reversible depression of the central nervous system

resulting in loss of sensation and response to all external stimuli in the whole body

regional anesthesia

the anesthesia injected near a cluster of nerve to numb only a specific area of your body that requires surgery when the patient is conscious

ex:

• spinal block

• subarachnoid block

• intra dural block

• intrathecal block

sedation

conscious sedation

a combination of medicines to help you relax (a sedative) and to block pain (an anesthetic) during medical or dental procedure

local anesthesia

temporary loss of sensation or pain in a circumscribed area of the body by topically applied or injected agent without depressing the level of consciousness

clinical significance of local anesthesia

produces loss of sensation without inducing a loss of consciousness

the only method and substance that induces a transient and completely reversible state of anesthesia in our clinical practice

causes of loss of sensation in local anesthesia

depression of excitation in nerve endings

inhibition or blocking of the conduction process in peripheral nerves

methods to induce local anesthesia

compression of tissues — mechanical trauma

low temperature — hypothermia

anoxia — extreme form of hypoxia (reduced amount of oxygen)

chemical irritants — alcohol & phenol

chemical agents — local anesthetics

botulinum toxin

an example of muscle relaxant

a chemical irritants

inhibits or blocks messages from brain / spinal cord to the muscles

desirable properties of local anesthetics

non- irritating

reversible

low degree of systemic toxicity

potent local anesthetic

rapid onset

sufficient duration

adequate tissue penetration

low allergic reactions

stable in solutions

sterile or capable of sterilization

pain

the most commonly experienced symptom in dentistry

yet, a precise definition of pain does not exist as pain has a subjective / psychophysiological aspect (a painful stimuli for one individual may not be painful for another)

it can be defined as "any unpleasant experiences may it be emotional, mechanical / physical or chemical with or without tissue damage usually initiated by a noxious stimulus”

dual nature of pain

physioanatomical aspect

psychophysiological aspect

physioanatomical aspect

pain perception

physiologic process involved

anatomical parts involved

similar in all individuals

psychophysiological aspect

pain reaction

psychological aspect of pain

different for each individual

pain reaction threshold

minimum intensity of the stimuli for it to be considered painful

lowest level of pain a patient will detect

2 types of pain reaction threshold

high pain threshold

low pain threshold

high pain threshold

hyporeactive px in response to stimuli

low pain threshold

hypereactive px in response to stimuli

pain reaction tolerance

the maximum intensity of pain a patient can tolerate without the need for intervation

classification and types of pain

duration

location

intensity

etiology

pain based on duration

acute pain

chronic pain

acute pain

sudden onset

1st pain

sharp, localized and throbbing

information carried through A delta fibers which are large and thinly myelinated neurons ( 100 m/s)

chronic pain

long lasting pain

dull and aching pain

information carried through C – fibers which are small and thin unmyelinated neurons ( 0.5-2m/s)

pain based on location

headache

joint pain

back pain

cardiac pain

stomach pain

referred pain

phantom pain

referred pain

pain felt in an area rather than the site of origin

psychogenic pain

pain profuced or caused by psychic or mental factors rather than organic factor

phantom pain

pain felt on part of the body that has been lost

pain based on intensity

mild pain (pain scale reading is 1-3)

moderate pain (pain scale reading is 4-6)

severe pain (pain scale reading is 7-10)

pain based on etiology

nociceptive pain

neuropathic pain

nociceptive pain

somatic and visceral pain

it send pain signals to the CNS

results from actual or potential damage to non-nervous tissues such as skin, muscles, bones, or internal organs

associated with actual tissue damage and is typically described as sharp or aching

neuropathic pain

peripheral neuropathic pain & central neuropathic pain

damage to the nerve itself causes typical pain symptoms

associated with actual tissue damage and is typically described as sharp or aching

results from damage or dysfunction in the nervous system itself, either peripheral (e.g., nerves) or central (e.g., spinal cord, brain)

can be caused by diseases, injuries, or conditions that affect the nervous system

nociceptors

a receptor preferentially sensitive to a noxious stimulus

this is modulated when there are analgesics & anesthetics drugs

neuralgia

pain present in the nerve

ex: trigeminal neuralgia (tic douloureux)

tx:

• carbamazepine (tegretol) — anticonvulsant drug

• mepivacaine — local anesthetic

pain theories

specifity theory

pattern theory

gate control theory

hydrodynamic theory

specifity of pain

describes pain systems as a straight-through channel from the skin to the brain

the most widely accepted theory of pain transmission through the end of 19th century

it advances the idea that the body’s neurons & pathways for pain transmission are as specific & unique as those for other body senses, such as taste or touch

it proposes that free nerve endings in the skin act as pain receptors, accept sensory input, and transmit this input along highly specific never fibers

these fibers synapse in the dorsal horns of the spinal cord, and cross-over to the anterior & lateral spinothalamic tracts

these nociceptors once activated carry the unpleasant experience to “pain center” within the brain

descarets in 1644

who developed the specifity theory of pain

thalamus

pain generation

cerebral cortex

pain localization

von frey in 1895

who developed the concept of specific cutaneous receptors?

pressure

paccinu’s corpuscle

cold

kalus end bulb

hot/stretch

ruffini end organ

pain

nociceptors

free nerve ending

pattern theory

proposed in the early 1900s

pain is not a separate entity but are produced by the over summation of other sensory input at the dorsal horn of the spinal cord

AKA: central summation

it identifies 2 major types of pain fibers:

1. A-delta — rapidly conducting fibers

2. C-fibers — slowly conducting fibers

goldscheider in 1894

who developed pattern theory of pain

spatial summation

space dependent

temporal summation

tempo / stimulation

time-dependent

stimulus intensity & summation

the critical determinant of pain

gate control theory

claims the existence of a so called “gate” in the spinal cord that controls the passage of information from periphery to brain

the information that travel faster have higher priority to pass the gate and arrive at brain

suggests that pain and its perception are determined by interaction of 2 systems: 1st & 2nd system

oligodendrocytes

myelination of central nervous system

schwann cells

myelination of peripheral nerve system

melzack & wall in 1965

who developed gate control theory of pain?

1st system

substantia gelatinosa in the dorsal horns of the spinal cord

it regulates impulses entering or leaving the spinal cord

2nd system

an inhibitory system within the brainstem

located in the brain stem

it is believed that cells in the midbrain, activated by a variety of functions such as:

• opiates

• physiologic factors

• presence of pain itself

• signal receptors in the medulla

these receptors in turn stimulate nerve fibers in the spinal cord to block the transmission of pain fibers

it is hypothesized that this brainstem regulatory system may help explain why even severe pain may not be perceived under certain circumstances, such as when an athlete fails to notice an injury until the competition is over

hydrodynamic theory

provides explanation for dentinal pain & sensitivity

suggest that the nerve endings near the pulp are stimulated due to the movement of dentinal fluids present in dentinal tubules

dentinal sensitive is caused by direct stimulation of sensory nerve ending in the dentin which are primarily located near the pulp

yet the most sensitive part of the tooth is at dentinoenamel junction where no nerve endings exist

factors that lower the pain threshold

anxiety

depression

fear

isolation

fatigue

anger

sleeplessness

persistent pain

factors that raise the pain threshold

symptom relief

rest

sleep

diversion

empathy

sympathy

medications: analgesics / anxiolytics / anti-depressants

psychophysiological nature of pain

age (the younger the patient, the more pain reaction)

gender (women have lower pain threshold)

race (southern europeans show more pain reaction than northern europeans)

fatigue

emotional stability

fear & apprehension

methods of pain control

removing the cause — restorative treatment, extraction, PDL treatment

blocking the pathway of painful impulses — local anesthesia

raising the pain pain threshold — non-opioid analgesics

preventing pain reaction by cortical depression — opioid analgesics, general anesthesia, tranquilizers

using psychosomatic methods

pathway of pain

describes how a certain stimuli can travel from periphery ( skin or tooth) to brain and be interpreted as pain

most of painful stimuli in dentistry are mechanical (a stimuli that causes physical injury to tissue)

can be further aggravated by inflammation and its chemical modifiers (mechanical + inflammation)

explains the physioanatomical aspect of pain (pain perception)

encompasses all theories of pain

1st order neuron

caries electrical impulse from periphery to spinal cord

synapse

point of communication between the primary & secondary neuron (impulse converts from electrical to chemical)

2nd order neuron

carries impulse from spinal cord to thalamus

thalamus

generates pain

part of the brain that interprets the impulse

3rd order neuron

carries impulse from thalamus to cortex

cortex

responsible for pain localization center

limbic system

where emotions are being processed

faciliation & retrieval of memories

hypothalamus

control conducting center

thalamus

pain generated

but doesn’t know where is the pain, only can feel the pain

2 types of nociceptors

A delta — sharp / fast : myelinated

C fibers — dull / slow : unmyelinated

opioid analgesics

have a supraspinal mode of action

they depress the cortex so the brain can not localize the pain

have a spinal mode of action which is considered indirect

cause activation of the descending modulatory pathway

the only indirect MOA: opiods

patients taking this usually describe it as “the pain is still there but it is not that bad”; this is due to them not knowing where the pain is coming from

modulatory pathways of pain

when the body needs internal processes to control pain

2 types of modulatory pathways of pain

ascending modulatory pathway

descending modulatory pathway

ascending modulatory pathway

entails creating faster impulses than pain impulses to overload the synaptic region

this is the reason you rub your hand when it is scratched or injured to lessen the intensity of pain

the synaptic region located in Substantia Gelatinosa of Spinal cord is the “Gate” in Gate control theory

recall that all sensory information enter the spinal chord at the dorsal horn (this includes pain, touch, hot, cold and etc.)

all their 1st order neurons synapse with their corresponding 2nd order neuron at substantia gelatinosa

all 1st order neurons produce their own neurotransmitters and saturate the synaptic region

descending modulatory pathway

inhibits production of neurotransmitters in the 1st order neuron

travels to the synaptic region

also activatesthe interneuron—releases its own neurotransmitter to saturate the synaptic region

inhibitory neurotransmitter

serotonin

norepinephrine

GABA

excitatory neurotransmitters

glutamine — A delta

substance P — C fibers

endogenous opioids

enkephalin & morphine-like substances produced inside the body saturate the region

inhibit neurotransmitter production in the 1st order neuron

prevent depolarization of the 2nd order neuron

prostaglandin

one of the chemicals produced that causes sensitization of free nerve endings (nociceptors)

tissue injury & infammation

leads to production of numerous chemicals at the site of injury

endogenous opioids

enkephalins

endorphins

dynorphins