Monitoring Anaesthesia Flashcards
What should be observed during anaesthesia? What can be monitored using equipment?
- depth
- mucous membranes
- pulse
- chest movement
- pupil size
- responses to surgery
- blood loss
- urine output?
machines
> respiratory gases
> pulse ox
> blood pressures
> ECG
> thermometer
> blood gases
What can be used to assess depth of anaesthesia?
- eye position
- presence of nystagmus
- lacrimation
- pupil size and response to light
- nuero responses (eg. cranial nerve reflexes)
- muscle relaxation (jaw, neck)
- EEG changes (people)
What does capnography measure? How can arterial CO2 be estimated?
- CO2 in resp gases
- end-tidal and inspired CO2
- End tidal = Alveolar = Arterial CO2
Normal PaCO2?
35-45mmHg
How can kPa be calculated from hhMg?
divide mmHg by 7.5 to give kPA
At waht PaCo2 is IPPV warranted?
> 60mmHg
Causes of hypercapnia?
- alveolar hypoventilation
- ^ CO
- hyperthermia
- bicarbonate administration
Causes of hypocapnia?
- v CO (eg. shock)
- hyperventilation/shallow breaths
- artefact
- hypothermia
What shape is the normal capnogram?
- log increase from baseline, alveolar plateaux phase, sharp drop to baseline (where end tidal values measured)
What can changes in the capnograph indicate?
- rebreathing
- asthma
- cardiogenic oscillations -> ripple effect
- VQ mismatch
- tachypnoea
What is FI/ET anaesthetic agent concentration useful for?
- helps assess depth
- need to know MAC for this to be useful
- useful when using v low flows in circle system
How can oxygenation be assessed?
- cyanosis
- pulse ox
- blood gases
What does pulse ox tell you? What does it not tell you?
Saturation of Hbg (SpO2%)
pulse rate
adequate tissue perfusion? (be aware may squash underlying vessels and give false reading)
- does NOT measure ventilation
How is oxygen delivery calculated?
Oxygen content x CO
Normal SpO2 range? What do low number indicate?
95-100%
<60mmHg = hypoxaemia
What is spirometry similar to?
Peto tube measuring airspeed in planes
Causes of low SpO2 on 100% oxygen?
- oxygen supply, probe position, BP may be affected reading, alpha 2 agonist given??
> R->L shunt - anatomical shunt
- intrapulmonary shunt (VQ mismatch) esp horses
> diffusion impaired (rare)
What effect does 2,3 DPG have on the O2 dissociation curve?
shifts it right
2,3-DPG produced in chronic anaemia
What does ECG not tell you?
- cardiac output
- blood pressure
- mechanical activity of the heart
What methods of measuring blood pressure are there?
- Invasive (direct, IBP)
- Non-invasive (NIBP) > doppler (cats true value between mean and systole) and oscillometry (tends to under read, MAP value most accurate)
Normal BP systole, diastole and mean?
- 100-160mmHg systole
- 60-100mmHg diastole
- 80-120mmHg mean
- mean must stay above 60 or renal perfusion will fall
Where does the transducer of invasive blood pressure probes need to be positioned?
- point of shoulder in dorsal recumbency
- manubrium sternea in lateral
> at level of the heart
Tx for blood pressure dropping < 60-70mmHg?
- reduce depth
- fluid bolus (5-10ml/kg)
- inotropes (dopamine, dobutamine)
- AVOID NSAIDs
Which blood gases are analysed for which parameters?
- arterial = ventilation
- venous = acid/base balance
