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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
Q

What are the important questions within the pre-op assessment?

A
  • 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
Q

What are the important examinations within a pre-op assessment?

A

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
Q

What is the ASA classification?

A

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
Q

What are the important pre-op investigations?

A

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
Q

What are the important pre-op preparations?

A
  • drug therapy: continue or discontinue
  • starvation time
  • G&S and crossmatch
  • DVT prophylaxis
  • book HDU/ITU bed
  • fluids
30
Q

What is the difference in spO2 and paO2 in terms of the amount of oxygen measured?

A

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
Q

What is the standard emergency oxygen mask?

A

15l non-rebreathe mask

Put on for ~10min, then titrate oxygen to spO2 > 94%

32
Q

What are the different types of oxygen supply?

A

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
Q

How much oxygen should a COPD patient be given?

A

Give high flow oxygen immediately and then titrate to spO2 of 88%-92% and paCO2 to normal pH (kidneys compensate for hypercapnia)

34
Q

What does an ABG measure?

A
  • pH
  • paO2
  • paCO2
  • Hb
  • glucose
  • base excess
  • HCO3-
  • lactate
  • K+
35
Q

What does a VBG measure?

A
  • pH
  • lactate
  • K+
  • base excess
  • Hb
  • glucose
36
Q

What is normal urine output? Define oliguria and anuria.

A

Normal: 60ml/hr

Oliguria: <400ml/day (20ml/hr)

Anuria: <100ml/day

37
Q

What is the normal CVP? How should a low CVP be treated?

A

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
Q

What are the uses of capnography?

A
  • confirm tracheal intubation
  • detect acute airway problems e.g. tracheal tube blocked/dislodged
  • detect apparatus malfunction
  • detect acute alteration in cardioresp. function
39
Q

What is responsible for the for the typical appearance of a capnograph?

A

Dead space exhaled (no CO2) —> alveolar gas exhaled (rapid rise in CO2) —> plateaus —> end-tidal CO2 tension (0.5kPa-0.8kPa)

40
Q

When can the end tidal CO2 be increased?

A

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
Q

When can the end tidal CO2 be decreased?

A

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
Q

What is the Beer-Lambert law?

A

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
Q

Describe the pharmacokinetics and indications of suzamethonium.

A

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
Q

What are the ADRs of suxamethonium?

A
  • hyperkalaemia
  • bradycardia
  • increased intracranial pressure
  • increased intraocular pressure
  • prolonged paralysis
  • anaphylaxis
  • malignant hyperthermia
  • muscle pains
45
Q

What are the contraindications for suxamethonium?

A
  • recent burns
  • spinal cord trauma causing paraplegia
  • hyperkalaemia
  • severe muscular trauma
  • Hx of malignant hyperthermia
46
Q

What are the stages of rapid sequence induction?

A
  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
Q

Give some examples of sedative/induction agents.

A
  • lidocaine
  • midazolam
  • ketamine
  • fentanil
  • thiopentone
  • propofol
  • etonidazole
48
Q

Give some examples of paralytic agents.

A
  • succinylcholine
  • rocuronium
  • suxamethonium
49
Q

Give some examples of emergency drugs in anaesthetics.

A
  • atropine (bradycardia)
  • metaraminol (acute hypotension)
  • ephedrine (hypotension during spinals, bradycardia)

Peri-op (15 decks)

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