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Specialties > Anaesthetics > Flashcards

Anaesthetics Flashcards

1
Q

Difference between local and general anaesthetic

A

General: insensibility in the whole body, causing unconsciousness - reversible coma using centrally acting drugs (hypnotics and analgesics)
Local: insensibility of a region of the body, using drugs applied directly to the tissues to affect the nerve supply of that area

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2
Q

How do general anaesthetics work?

A

Suppress neuronal activity by opening chloride channels, hyperpolarising the neurone and suppressing exitatory synaptic activity (less likely to fire)
Cerebral function lost from top-down; complex processes, such as level of consciousness and hearing, lost first while primitive functions lost later (reflexes mostly spared)

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3
Q

Sequence of general anaesthesia

A

Induction with inhalational or IV agent Maintenance with inhalational or IV agent
(Usually IV then inhalational)
IV maintenance can occur with newer agents and computer controlled infusion
Additional regional analgesia and anaesthesia

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4
Q

How do IV anaesthetics work?

A

Rapid onset of unconsciousness (arm to brain time)
Fat soluble drugs, cross membranes quickly
Rapid recovery (leave circulation quickly/redistributed/metabolised)
One off bolus leads to temporary unconsciousness

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5
Q

How do inhaled anaesthetics work?

A

Halogenated hydrocarbons Via lungs (cross alveolar basement membrane easily, rely on concentration gradient from lungs to blood to brain - arterial conc ~ alveolar partial pressure)
Mininum alveolar concentration measures potency (low MAC=high potency)
Slower induction
Flexible duration (stop when needed)
Washout period as CG reversed

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6
Q

Why do we need balanced anaesthesia?

A

Different drugs do different jobs
Titrate them separately
Avoid overdose
Gives flexibility, tailored to needs (consciousness, need for analgesia, need for muscle relaxation, airway management)

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7
Q

Problems with balanced analgesia?

A

Polypharmacy, increased reactions, allergies
Artificial ventilation and need for airway management if using muscle relaxant
Separates relaxation and hypnosis stages, (potential for patient to be aware/’awake!!!)’

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8
Q

Induction of general anaesthesia requirements?

A

Quietness (dedicated anaesthesia room)
IV (propofol), gas (sevoflurane/halothane)
Monitoring of consciousness
Airway maintenance (triple airway, face mask, oropharyngeal airway, laryngeal mask, cuffed tube to avoid contamination)

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9
Q

How is consciousness level monitored?

A

Loss of verbal contact
Loss of movement
Respiratory pattern and ECG Planes: eyes roll and fix, loss of corneal/laryngeal reflexes, dilated pupils and loss of light reflex, intercostal paralysis with shallow abdominal breaths

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10
Q

Complications of general anaesthetic?

A

Ineffective triple airway manoeuvre
Airway device malpositioned or kinked
Laryngospasm (forced adduction of vocal cords, can obstruct completely, caused by airway stimulation in light planes)
Aspiration due to loss of protective reflexes, foreign material present (blood, gastric)

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11
Q

How does general anaesthetic affect the respiratory system?

A

Agents are respiratory depressants
Reduction in hypoxic and hypercarbic driver
Reduced tidal volume
Increased respiratory rate
Paralysed cilia
Decreased FRC (lower lung volumes, VQ mismatch)

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12
Q

How does general anaesthetic affect the cardiovascular system?

A

Central: depresses centre in medulla oblongata, reducing sympathetic outflow
Reduction in vasoconstrictor tone=vasodilation meaning decreased peripheral resistance
Venodilation leading to reduced venous return and decreased cardiac output
Agents are negatively inotropic (weaken the force of muscular contraction)

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13
Q

Brief description of pre-op assessment (History, examination, investigation, optimisation)

A

Co-morbidities, ability to withstand stress, cardiopulmonary disease, previous surgery, anaesthesia, drugs/allergies (stop diabetic drugs, anticoagulants beforehand) ETT, potential issues (airways, lying flat, reflux, obesity), cardiac risk index
Detect unknown/suspected conditions and severity, risk assessment, aware of complications, cardio/resp assessment
Optimising current control

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14
Q

When is intubation required?

A

Protect airway from gastric contents If muscle relaxant required
Need blood gas control
Shared airway with risk of blood contamination
Restricted airway access

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15
Q

Endotracheal intubation

A

Via mouth or nose (rarely, not in emergencies) Laryngoscope and muscle relaxant Abolish laryngeal reflexes ‘Sniffing the morning air’ - triple airway of head tilt, chin lift, jaw thrust

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16
Q

Risks of intubation

A 
Damaged teeth or dental work
Throat or tracheal injury 
Fluid build-up in organs or tissues 
Bleeding 
Loss of protective reflexes (corneal, joint position) 
VTE risk 
Aspiration 
Unable to consent/identify
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17
Q

Types of intubation

A

Triple airway manoeuvre (head tilt, chin lift, jaw thrust)
Anaesthetic face mask
Oropharyngeal airway or laryngeal mask airway (supraglottic)
Endotracheal cuffed tube if need to avoid contamination (infraglottic)

18
Q

Monitoring an anaesthetised patient

A

Peripheral saturation and fraction inspired (O2 rich air is above normal of 0.21, avoid oxygen toxcity)
ECG, blood pressure
Respiratory parameters
Agent monitoring
Temperature, urine, NMJ Venous/arterial monitoring (invasive)
Ventilator disconnect

19
Q

Recovering from anaesthesia

A 
Dedicated area, trained staff 
Check for issues with ABC (may not have regained consciousness, airway control) 
Pain management 
Post-op nausea, vomiting 
Need criteria for discharge or transfer
20
Q

How does local anaesthesia work?

A

Insensitivity in relevant part of body, applied directly to tissues (spinal, epidural, plexus or nerve block)
Block sodium channels responsible for single propagation (no depolarisation)

21
Q

Complications of local anaesthetic

A 
Cardiovascular depression 
Cardiopulmonary arrest 
Tingling/numbness of mouth and tongue 
Convulsions due to involuntary muscle contractions 
Coma Drowsiness, light-headedness 
Tinnitus, visual disturbance
22
Q

How is local anaesthetic delivered?

A 
Wound catheters 
Epidural (+/- opiates) 
Nerve plexus catheters 
Intrathecal (+/- opiates) 
Local infiltration of wounds
23
Q

When are spinal/epidural anaesthetics used?

A

Want to avoid general
Want to avoid airway problems (difficult intubation or obstruction)
Allergies
Severe respiratory disease

24
Q

Contraindications to spinal or epidural anaesthesia?

A 
Patient refusal 
Fixed cardiac output (aortic or mitral stenosis) 
Infection 
Hypocoagulability (drugs or disease) 
Technical difficulties 
Neurological defect
25
Q

How does spinal anaesthesia work?

A

Subarachnoid injection Block to T4???

26
Q

Intensive care is used when…

A

Reversible organ dysfunction or failure
Supportive treatment means definitive treatment will work
Patients need more care than lower levels NOT if progressive decline, chronic irreversible condition, ultimately fatal, will never become support-free, ultimate unacceptable quality of life

27
Q

Level 3 critical care…

A

Needs advanced respiratory support
OR basic RS plus support of two or more organ systems
OR multiple organ failure
Plus reversible, improvement possible

28
Q

Cardiovascular support in ITU

A

Invasive monitoring and appropriate fluid resuscitation Inotropic or vasoactive support Intraaortic balloon counter pulsation ECMO

29
Q

When is airway support needed in ITU?

A

Coma Acute or impending airway compromise (traumatic, infective)
Need for sedation e.g. delirium preventing treatment of underlying disorder

30
Q

How are airways supported in ITU?

A

CPAP Endotracheal tubes Ventilator Nitric oxide (pulmonary vessel dilation)

31
Q

Renal and hepatic support in ITU

A

Dialysis is rare due to dramatic physiological changes
Continuous venovenous filtration ‘Liver dialysis’ molecular adsorbent recirculating system (MARS)
Transplant in long term Supportive management in acute decomp

32
Q

Neurological support in ITU

A

Airway management Monitor intracranial pressure, treat with mannitol and hypertonic saline Metabolic, traumatic, infective, ischaemic

33
Q

Types of shock

A

Hypovolaemic (low volume or haemorrhage, empty tank)

Distributive (sepsis, anaphylactic or neurogenic cause due to vasodilation/blood redirection/loss of tone in small vessels, leaky pipe)

Cardiogenic and obstructive (tamponade, tension, failed ventricles, failed pump or blocked pipe)

34
Q

What is shock?

A

Acute circulatory failure
Inadequate or inappropriate perfusion
Cellular hypoxia

35
Q

How is pain classified?

A

Duration (acute, chronic)
Cause (cancer=progressive, or non-cancer)
Mechanism (nociceptive or neuropathic)

36
Q

Difference between nociceptive and neuropathic pain

A

Physiological or inflammatory pain with obvious tissue damage or illness; protective function, sharp or dull but well localised
Nervous system damage without tissue injury; not protective, burning or shooting with numbness, pins and needles, poorly localised

37
Q

Steps of pain

A

Peripheral (tissue injury leading to chemical release, nociceptor stimulation, signal travels in Aδ or C nerve to spinal cord)
Spinal cord (dorsal horn site of relay, Aδ or C synapse with second nerve which CROSSES OVER at same level)
Brain (second relay at thalamus, connects to cortex (site of pain perception), brainstem, limbic system
Modulation (descending pathway back to dorsal horn, normally depresses pain signal)

38
Q

Treating pain at each step (Peripheral, spinal cord, brain, descent/modulation)

A

Periphery; NSAIDs, non-pharmacoloigical (rest, elevate, compress, ice/heat), local anaesthetic

Spinal cord; local anaesthetics, opioids, ketamine, NP (acupuncture, massage, TENS)

Brain (psychological, paracetamol, opioids, clonidine

39
Q

Pain relief in nociceptive vs neuropathic pain

A

Use WHO pain ladder in NC
Mild: paracetamol (+/- NSAIDs)
Moderate: paracetamol (+/- NSAIDs) + codeine/alternative
Severe: paracetamol (+/- NSAIDs) + morphine, fentanyl, diamorphine, oxycodone

Neuropathic pain, no WHO ladder Amitryptiline, gabapentin, non-pharma

40
Q

What is neuropathic pain?

A 
Abnormal processing of pain signal 
Nervous system damage or dysfunction 
Needs to be treated differently 
Damage: nerve trauma, diabetic pain 
Dysfunction: fibromyalgia, chronic tension headache
41
Q

Measuring pain on a scale

A

Faces scale
Verbal scale (mild, moderate, sever)
Numerical scale
Visual analogue scale

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