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Anaesthesia > Clinical IPPV & NMB > Flashcards

Clinical IPPV & NMB Flashcards

1
Q

When are circumstances where we need to breathe for the patient?

A
  • P is unable to ventilate (Thx Sx, diaphragmatic hernia Sx, NMB)
  • inadeq ventilation
  • increased ICP
  • administration of high dose opioid drugs
  • IPPV, only ventilate when indicated
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2
Q

Minute ventilation (MV) =

A

TV x RR

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3
Q

The efficiency of ventilation is assessed by…

A

the elimination of CO2

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4
Q

How do you measure the efficiency of ventilation?

A

By assessing the elimination of CO2 by capnograph or intermittent blood gases

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5
Q

Inadequate ventilation =

A

hypoventilation

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6
Q

When does hypoventilation occur?

A
  • too deep anaesthesia
  • geriatric P
  • obesity
  • pregnancy, space-occupying masses
  • muscle weakness
  • laparoscopy
  • pain
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7
Q

Hypoventilation increases partial pressure of

A

CO2 above normal

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8
Q

What are mild systemic effects of hypercarpia/hypercapnia?

A

Stimulation of the SNS by
- tachycardia
- vasoconstriction
- hypertension

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9
Q

What are the effects on the heart of severe hypercapnia?

A
  • Tachycardia increases myocardial O2 consumption
  • Neg inotropy (decreased cardiac contractility) leads to hypotension
  • Hypotension decreased myocardial oxygenation
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10
Q

What are the effects of severe hypercapnia on the respiratory system?

A
  • CO2 displaces O2 in alveoli leading to Hypoxaemia if there is no supplemental O2 administered
  • respiratory acidosis worsens arrhythmias
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11
Q

What effects are the effects of severe hypercapnia on the CNS?

A
  • CO2 regulates cerebral BV diameter so Low CO2 = constricted BV, High CO2 = dilated BV –> inside skull = increased ICP
  • Vasoconstriction –> decrease blood –> loss of consciousness
  • EtCO2 > 7.4 kPa (>56 mmHg) –> cerebral vasodilation –> increased ICP
  • High CO2 lvls –> anaesthetic effects = decreased consciousness
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12
Q

What is intermittent positive pressure ventilation?

A
  • Manual squeezing of the bag on the breathing system or an ambu bag
  • mechanical using a ventilator
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13
Q

What equipment is required for IPPV?

A
  • suitable breathing system (Circle, Bain, T-piece)
  • +/- automatic ventilator
  • Emergencies: ambu bag (self-inflating)
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14
Q

What do you need to do to carry out IPPV?

A
  • normal RR (10-20 bpm)
  • normal TV (10-20 ml/kg)
  • normal inspiratory to expiratory ratio (1:2) aka active inspiration faster than expiration (passive recoil of lungs)
  • watch pressure gauge on system and do not exceed peak inspiratory pressure of 20 cm H2O
  • monitor EtCO2 and aim for normal 4.6-6 kPa (35-45 mmHg) –> over ventilation reduces brain vessels –> hypoxaemia
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15
Q

normal partial pressure of CO2 is required to stimulate

A

the respiratory centre

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16
Q

When CO2 levels are below the normal, there is no drive to…

A

breathe, therefore P will stop breathing

17
Q

Long-term lack of breathing leads to…

A

brain damage due to cerebral vasoconstriction causing brain hypoxia

18
Q

My patient is breathing spontaneously, when should I start IPPV?

A
  • If EtCO2 is constantly > 7 kPa (55 mmHg)
  • if you have a cardiac P, start if EtCO2 is constantly >/= 6 kPa (45 mmHg)
  • if increased ICP, start immediately & maintain around 4.6 kPa (35 mmHg)
19
Q

IPPV raises… therefore it may reduce…

A

IPPV raises intrathoracic pressure, therefore it may reduce cardiac output –> drop in BP

20
Q

If a patient is breathing against a ventilator, what should you be aware of or do in response?

A
  • check depth of anaesthesia
  • may feel more pain so give more analgesia
  • use RR slightly faster than normal
  • increase tidal volume by ventilating so thx wall expansion is slightly greater than normal to reduce CO2 & respiratory drive, do NOT exceed PIP 20 cm H2O
21
Q

Why might a patient fail to breathe following IPPV?

A
  • deep anaesthesia
  • hypothermia
  • hypocapnia
  • pneumothorax
  • pain
  • residual NMB/opioids
  • hypoxic brain damage
22
Q

What are clinical methods of providing muscle relaxation?

A
  • deep anaesthesia
  • regional nerve blocks
  • paralyse the P
  • drugs w/ muscle relaxant properties (central action - diazepam, guaifenesin) (peripheral action - at the NMJ = paralysis)
23
Q

What are the ‘take-home messages’ of a neuromuscular blockade?

A
  • All skeletal muscle in paralysed so the patient cannot breathe or move
  • does NOT provide analgesia so P can feel all Sx incl pain & all will be consciously perceived
  • does NOT provide hypnosis or sedation so P is awake!
24
Q

What are potential indications for NMB?

A
  • to relax skeletal muscle
  • to facilitate control of respiration
  • ocular Sx
  • TRUE INDICATIONS ARE RARE AND NONE ARE IN GENERAL PRACTICE!
25
Q

What are some NMB considerations?

A
  • P must be as stable as possible
  • P must have rigorous pre-anaesthetic assessment
  • P must be intubated & provided w/ IPPV
  • Must ensure analgesia & hypnosis
26
Q

What signs are used to monitor depth of anaesthesia during NMB?

A
  • RR & depth
  • jaw tone
  • flexor withdrawal reflex
  • palpebral reflex
  • position of eye
  • ALL ARE OF LITTLE USE WHEN PROFOUND NMB IS PRESENT SO YOU CANNOT USE THESE TO ASSESS YOUR PATIENT!
27
Q

Under NMB, monitoring depth depends on…

A
  • CV system: BP, HR, Pulse qlty
  • pupil dilation, lacrimation, salivation
  • twitching of facial muscles/tongue
  • capnography to ensure adequacy of IPPV
28
Q

What are important things to remember about a nerve stimulator?

A
  • does not monitor depth of anaesthesia, just depth of paralysis
  • all muscle twitches must return back to normal & at normal strength and working diaphragm to generate adequate tidal volume
29
Q

What are the patterns of stimul used with a nerve stimulator?

A
  • Train of four
  • double burst
  • tetanic
30
Q

Reversal of NMB is…

A

ESSENTIAL!

31
Q

What drugs are used to reverse NMB?

A

Neostigmine, edrophonium (anticholinesterase drugs)
Sugammadex

32
Q

For adequate reversal of NMB, you MUST CONFIRM…

A
  1. adequate ventilation
  2. adequate oxygenation while breathing air
  3. airway protection

Anaesthesia (24 decks)

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