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Peri-op > Anaesthesia > Flashcards

Anaesthesia Flashcards

1
Q

What are the components of the assessment stage of anaesthesia?

A
  • operation: appropriate? considerations?
  • risk: low/high, optimise risk
  • plan: local or general anaesthetic? monitoring req. (pre-, peri-, post-op)? level of monitoring during recovery?
  • information: post-op N&V, pain, risks
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2
Q

What is meant by the term “balanced anaesthesia”?

A

Mixture of small amounts of several neuronal depressants maximises the benefits (asleep, immobile, comfortable) whilst minimising the risks (resp. depression).

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3
Q

What is typically in the “big” syringe in anaesthesia?

A

Induction/hypnotic

e.g. propofol, ketamine

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4
Q

What is typically in the “small syringe” in anaesthesia?

A

Muscle relaxant/pain relief

e.g. non-depolarising muscle relaxant: suxamethonium
depolarising muscle relaxant: rocuronium

e.g. opioids: morphine (0.1-0.2mg/kg), remifentanil (t1/2 = 3min)

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5
Q

What are the components of the induction stage of anaesthesia?

A
  • location: induction/anaesthetic room, operating theatre (emergency, haemodynamically unstable, airway compromise)
  • monitoring: temp. (falls in first 30min of induction), gas analysis (O2, CO2, volatile agents), respiratory rate, BP, bpm, ECG, spO2, depth of anaesthesia
  • drugs: propofol, fentanil, ?muscle relaxants; reduced chest wall compliance; IV in obese, long procedure, unreliable airway, risk of vomiting
  • airway control: laryngeal mask airway (supraglottic; does not prevent airway being solied); endotracheal tube (prevents soiling of airway by entering trachea)
  • equipment: gas machine, syringe pump (total IV anaesthesia; used when thiopentone/gases are contraindicated e.g. porphyria, malignant hyperpyrexia), valve bag mask (if ventilation fails)
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6
Q

What is the normal appearance of a capnograph? How can appear abnormal?

A

Square waveforms - indicates chest wall movement, therefore endotracheal tube is in resp. tract

Hypoventilation = delay in measurement (~90s; compare to ECG)

Flatline = indicates dislodged tube/tube not in resp. tract

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7
Q

What are the components of the maintenance stage of anaesthesia?

A
  • !IV paracetamol!
  • IV NSAIDs
  • volatile agents
  • total IV anaesthesia (TIVA)
  • neuromuscular blockers
  • local anaesthetic (regional or central, can use in combination with general anaesthetic)
  • opioids
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8
Q

What is malignant hyperpyrexia?

A

Increased oxidative metabolism in skeletal muscle —> circulatory collapse

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9
Q

What are the components of the emergence stage of anaesthesia?

A
  • wear off: bolus IV, sodium thiopental, suxmethonium
  • withdraw: gas, TIVA
  • reverse: neuromuscular blockers, wellbeing —> C —> B —> A (wake before A if there is a risk of vomiting and after A increased venous pressure from coughing could pose a problem e.g. head injury)
  • antagonise: benzodiazepines e.g. flumazenil; opioids
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10
Q

What are the components of the recovery stage of anaesthesia?

A
  • post-op care unit (PACU)
  • intact reflexes?
  • O2?
  • monitoring?
  • transfer to ward when awake, pain & post-op N&V are controlled, no complications
  • PO drugs (paracetamol, oromorph) used as required for breakthrough pain as analgesia wears off
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11
Q

Reminder: define pain.

A

Unpleasant sensory and emotional experience associated with actual or potential tissue damage; requires consciousness.

  • ACUTE = recent onset, probable limited duration, identifiable cause
  • CHRONIC = persists beyond the time of healing of an injury, 3mnths
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12
Q

Reminder: what are the different types of nociceptors?

A 
A-delta = shap, localised, somatic pain
C = dull, diffuse, visceral pain
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13
Q

Reminder: how is nocicpetion transmitted to the brain?

A

A-delta & C fibres —> dorsal root ganglia —> laminae II & III —-> decussate to spinothalamic tracts —> cortex

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14
Q

What is the first class of drugs on the pain ladder?

A

Non-opioids:

  • paracetamol (4g/24hrs in adults)
  • NSAIDs
  • COX-2 inhibitors
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15
Q

What is the second class of drugs on the pain ladder?

A

Add weak opioids:

  • tramadol
  • codeine
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16
Q

What is the third class of drugs on the pain ladder?

A

Strong opioids:

  • morphine
  • fentanyl
  • pethidine
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17
Q

Outline the properties of paracetamol.

A

Antipyrexic
PO/IV
50kg

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18
Q

Outline the properties of NSAIDs.

A

Antipyrexic
Useful for inflammatory pain
e.g. ibuprofen, diclofenac (suppository for C section), paracoxib, ketorolac, aspirin
Caution in: renal failure, bleeding, fluid retention, bronchospasm, GI disturbance (esp. if NBM)

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19
Q

Outline the properties of codeine.

A

Co-codamol OTC

ADRs: N&V, resp. depression, constipation

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20
Q

Outline the properties of tramadol.

A

?5-HT activity

ADRs: N&V, constipation, dizziness, disorientation (caution in the elderly)

21
Q

Outline the properties of remifentanil.

A

Quick-acting

Use infusion to keep constant level

22
Q

Outline the properties of morphine.

A

Long-acting

Give to cover before stopping remifentanil

23
Q

List some examples of adjuncts to analgesics used in anaesthetics.

A
  • clonidine = prolongs effect of local anaesthetic up to 10-12hrs
  • ketamine = induction agent, maintains airway, dissociative state/hallucinations, good analgesia, good for shock (increased symp. activation), field agent, prevents chronic pain in spinal surgery/neuropathic pain,
  • gabapentin/pregabalin = pre-op and post-op neuropathic/chronic pain
24
Q

What is patient controlled anaesthesia? How is it limited?

A

50mg morphine syringe (1mg/ml)
Lockout interval of 5min
Therefore 1mg/5min
Req. monitoring: resp. rate, consciousness, N&V, O2 sats.

note: blocked tube may prevent analgesia, then flush causes bolus overdose

25
What are the important questions within the pre-op assessment?
- smoking: nicotine affects airway - previous anaesthesia: post-op N&V, reactions, duration of admission, ITU admission - CVD: hypotension, IHD, congestive heart failure, valvular heart disease, pacemaker - metabolic/endocrine: diabetes, thyroid, obesity - respiratory: asthma, COPD, pulmonary disease - neurological disease: epilepsy, TIA - renal disease - Rx - prophylaxis
26
What are the important examinations within a pre-op assessment?
General: ?anaemia, ?cyanosis, ?clubbing, ?jaundice, ?peripheral oedema, ?lymphadenopathy Airway: make ABCD plan for ventilation - Mallampati scoring: scale according to how much of the posterior pharyngeal wall and uvula can be seen - general appearance of neck, face, maxilla, mandible - jaw movement - head extension/flexion - teeth and oropharynx - soft tissues of the neck: ?masses - recent chest/cervical X-rays - mouth opening - loose teeth/dentures/piercings CVS: pulse, BP, JVP, heart sounds, murmur Resp,: tracheal position, chest expansion, percussion, auscultation Relevant system e.g. abdo. ASA classification
27
What is the ASA classification?
Classification of physical status: I = normal healthy patient II = patient with mild, systemic disease (inc. obesity, hayfever) with no functional limitations III = patient with moderate to severe disease that results in some functional limitation IV = patient with severe systemic disease that is a constant threat to life and is functionally incapacitating V = moribund patient who is not expected to survive 24hrs with or without surgery E = emergency procedure
28
What are the important pre-op investigations?
Baseline Bedside: urine dip., BM, BLOODS: - FBC = ?anaemia, ?sickle-cell, clotting profile - pregnancy - G&S IMAGING: - CXR: acute/recent worsening of cardiac/chest disease, ?TB FUNCTIONAL: - ECG: age>50yrs, Hx of IHD, hypertension, COPD
29
What are the important pre-op preparations?
- drug therapy: continue or discontinue - starvation time - G&S and crossmatch - DVT prophylaxis - book HDU/ITU bed - fluids
30
What is the difference in spO2 and paO2 in terms of the amount of oxygen measured?
98% of O2 bound to Hb therefore spO2 measures 98% of oxygen in blood 2% of O2 dissolved in solution therefore paO2 measures 2% of oxygen in blood
31
What is the standard emergency oxygen mask?
15l non-rebreathe mask Put on for ~10min, then titrate oxygen to spO2 > 94%
32
What are the different types of oxygen supply?
Nasal specs: - comfortable - max. flow of 4l (35% of which breathed in) - warms and humidifies air and secretions Venturi device: - 24%-60% oxygen range Hudson mask: - 60%-75% oxygen range Non-rebreathe mask: - 90% oxygen - reservoir of pure oxygen in bag - 15l/min flow High flow circuit: - 100% oxygen - 30l/min flow - noisy Anaesthetic circuit: - 100% oxygen - bag with reservoir
33
How much oxygen should a COPD patient be given?
Give high flow oxygen immediately and then titrate to spO2 of 88%-92% and paCO2 to normal pH (kidneys compensate for hypercapnia)
34
What does an ABG measure?
- pH - paO2 - paCO2 - Hb - glucose - base excess - HCO3- - lactate - K+
35
What does a VBG measure?
- pH - lactate - K+ - base excess - Hb - glucose
36
What is normal urine output? Define oliguria and anuria.
Normal: 60ml/hr Oliguria: <400ml/day (20ml/hr) Anuria: <100ml/day
37
What is the normal CVP? How should a low CVP be treated?
5-10cm H2O Low CVP (dehydration) give gelatin 250ml over 15min ---> review after 30min ---> further 250ml ---> senior help ---> titrate fluid until CVP has increased by 5cm (unless >15cm H2O)
38
What are the uses of capnography?
- confirm tracheal intubation - detect acute airway problems e.g. tracheal tube blocked/dislodged - detect apparatus malfunction - detect acute alteration in cardioresp. function
39
What is responsible for the for the typical appearance of a capnograph?
Dead space exhaled (no CO2) ---> alveolar gas exhaled (rapid rise in CO2) ---> plateaus ---> end-tidal CO2 tension (0.5kPa-0.8kPa)
40
When can the end tidal CO2 be increased?
Reduced alveolar ventilation - reduced resp. rate - reduced tidal volume - increased equipment dead space Increased CO2 production - fever - hypercatabolic state Increased inspired pCO2 - rebreathing - CO2 absorber exhausted - external source of CO2
41
When can the end tidal CO2 be decreased?
Increased alveolar ventilation - increased resp. rate - increased tidal volume Reduced CO2 production - hypothermia - hypocatabolic state Increased alveolar dead space - reduced CO - PE - high positive end-expiratory airway pressure during intermittent positive pressure ventilation Sampling error - inadequate tidal volume - water blocking sampling line - air entrapment into sampling line
42
What is the Beer-Lambert law?
Intensity of transmitted light decreases exponentially as conc. of substance increases AND intensity of transmitted light decreases exponentially as distance travelled through substance increases
43
Describe the pharmacokinetics and indications of suzamethonium.
Metabolised by plasma cholinesterase (5-10min) 30s-60s onset Indications: - rapid tracheal intubation - seizures after ECG Give IV 1-2mg/kg or 3mg/kg in emergency (total dose should not exceed 6-8mg)
44
What are the ADRs of suxamethonium?
- hyperkalaemia - bradycardia - increased intracranial pressure - increased intraocular pressure - prolonged paralysis - anaphylaxis - malignant hyperthermia - muscle pains
45
What are the contraindications for suxamethonium?
- recent burns - spinal cord trauma causing paraplegia - hyperkalaemia - severe muscular trauma - Hx of malignant hyperthermia
46
What are the stages of rapid sequence induction?
1. Pre-fill patient's lungs with high conc. of O2 2. Administer rapid-onset hypnotic (thiopentone) and NMJ-blocking drugs (suxamethonium) 3. Prompt unconsciousness and paralysis 4. Insert endotracheal tube Indicated when patient at high risk of pulmonary aspiration note: no artifical ventilation provided until intubation achieved (minimises insufflation of air into stomach)
47
Give some examples of sedative/induction agents.
- lidocaine - midazolam - ketamine - fentanil - thiopentone - propofol - etonidazole
48
Give some examples of paralytic agents.
- succinylcholine - rocuronium - suxamethonium
49
Give some examples of emergency drugs in anaesthetics.
- atropine (bradycardia) - metaraminol (acute hypotension) - ephedrine (hypotension during spinals, bradycardia)

Peri-op (15 decks)

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