Anaesthesia Machine and Monitoring Flashcards
The basic machine consists of:
- Supply of gases under pressure (pipeline, cylinders)
- Means of controlling and measuring gas flow
- Means of administering anaesthetic vapours
- Conduit to deliver gases/vapour to patient (breathing system)
- Means for providing IPPV (reservoir bag, mechanical ventilator)
- Additional safety devices
Breathing systems mostly used:
Open circuit: Jackson Rees modified Ayre’s T-piece (Mapleson F)
Closed circuit: the circle system
Signs of exhausted soda lime?
Colour change (white to purple)
Temperate (warm to cold)
Capnograph - rising baseline ETCO2
Clinical signs of hypercarbia (TOO LATE)
Modes of IPPV?
CMV (continuous mandatory ventilation)/ VCV (volume controlled ventilation)
PCV (pressure controlled ventilation)
PEEP (positive end-expiratory pressure)
SIMV (synchronised intermittent mandatory ventilation)
PSV (pressure supported ventilation)
Which mode of IPPV is used in adults with cuffed ETT?
CMV/VCV (preset tidal volume is delivered and airway pressures vary, therefore monitoring of airway pressure is NB)
Which mode of IPPV is used in paediatrics with uncuffed ETT?
PCV (compensates for leaks in the system)
Role of PEEP?
Aids oxygenation
Prevents atelectasis
Monitors of machine-patient interface?
Oxygen analyser (at common gas outlet)
Ventilation: TV, RR, flow rate, I:E ratio, MV
Airway pressure
Capnograph
Agent monitor for inspired and expired vapour concentration (i.e. fiISO, etISO)
Monitors of patient well-being?
Non-invasive: ECG, BP, Capnograph, Pulse oximeter, Temperature, Nerve stimulater
Invasive: Urinary catheter, CVP, arterial BP, pulmonary artery catheter (Swan-Ganz), trans-oesophageal echocardiograpy (TOE)
Maximum airway pressure to prevent barotrauma?
Normal tidal volume?
6-10ml/kg
Normal minute volume?
80-100ml/kg
Oxygen transport to tissues depends on:
Fi02
Airway
Breathing
Circulation
Normal SATS?
96-99%
Normal ET C02 with IPPV?
4-5,3kPa
Higher values may indicate hypo-ventilateion, and lower values may indicate hyperventilation.
Reasons for increased ET CO2?
Decreased alveolar ventilation:
Decreased RR and TV
Increased equipment dead space
Increased CO2 production:
Fever
Hypermetabolic state - malignant hyperthermia, thyrotoxicosis
Increased inspiratory CO2:
Rebreathing
Exhausted soda lime
External CO2 source
Reasons for reduced ET CO2?
Increased alveolar ventilation:
Increased RR and TV
Reduced CO2 production:
Hypothermia
Hypometabolic state - myxodoema
Increased alveolar dead space:
Reduced CO
PE
High PEEP
No CO2 delivery:
Cardiac arrest
Massive PE
Sampling error
Elements of CVS monitoring?
NIBP/invasive BP HR ECG CVP Pulmonary artery catheter
Monitoring the depth of anaesthesia:
Increased HR and BP (response to stimulation)
Processed EEG monitors - BIS and Entropy:
Slow EEG waves = deeper anaesthesia
Target: 40-60 where 0 is isoelectric EEG and 100 is awake
Auditory evoked potentials (AEP)
In which procedures should temperature be monitored?
All procedures > 15minutes
Places for temperature probe insertion?
Oral Nasal Oesophageal (core) Rectal Dermal In bladder (core) In outer ear
Why is heat loss is common in anesthesia due to:
Cold theatre temperatures
Cold circulating air (heat loss via convection)
Exposed body areas
Vasodilation from anesthetic agents
inability to shiver and generate heat (paralysed)
Adverse effects of hypothermia:
Vasoconstriction Shivering Poor enzyme function Respiratory depression Diminished muscle relaxant effect Slowed emergence from GA
Beneficial effects of hypothermia:
Brain cell protection from hypoxia (used to our advantage in cardiac surgical procedures or cardiac-pulmonary bypass)
