Anaesthetics Flashcards
What is the purpose of basic airway assessment in anaesthetics and what does it involve?
It focusses on the key question:
1. What is the risk of either bag-valve mask ventilation of endotracheal intubation being difficult?
History features:
- OSA
- tumour or mass in airway
- blood or secretions
- obesity
- restrictive lung disease or chest wall disease
Examination features:
- large neck
- small jaw or micrognathia
- beard
- Mallampati grade 3 or 4
- thyromental distance less than 6cm in adults
What are the indications for endotracheal intubation?
Endotracheal intubation is used for definitive airway control.
- respiratory failure
- aspiration risk, e.g. anaesthesia
- positioning, e.g. operation in prone position, abdominal muscle relaxation
What is hypoxaemia and what are its causes?
Hypoxaemia = low pO2 in blood
Four main causes:
- Low FiO2 (fraction of inspired oxygen)
- Hypoventilation
- V/Q mismatch
- Diffusion impairment or shunt
What are the different methods of monitoring oxygen levels?
Clinical methods
- patient’s colour
- respiratory rate (>24/min is sensitive indication of decompensation)
- posture
- pattern of accessory muscle use
- lung sounds
Non-invasive methods
- pulse oximetry
Invasive
- arterial blood gas analysis
What are the different routes of oxygen delivery?
- nasal prongs
- Hudson masks
- ## bag-valve-masks
What are the three main indications for IV fluids?
- resuscitation - restore circulating volume
- maintenance - daily fluid and electrolyte requirements
- replacement - volume lost via another route
How are fluids normally gained and lost from the body?
Intake:
- drinking
- water in food
- generated from metabolic processes
Losses:
- urine
- insensible losses from skin and lungs
- faeces
What are the types of IV fluids?
- Crystalloids: acqueous solutions of salts
- hypertonic
- isotonic (e.g. 0.9% NaCl, compound sodium lactate, plasmalyte)
- hypotonic - Colloids: large molecules in fluid that stay in intravascular space for longer period of time
- restricted to volume resuscitation
- albumin and gelatins - Blood products
What are the 5 main components of the perioperative assessment?
- Past anaesthetic history - complications incl. malignant hyperthermia
- Medical comorbidities - cardiac, respiratory, exercise tolerance, diabetes, liver disease, renal impairment, obesity
- Medications - allergies, adverse reactions, anticoagulants
- Investigations - may include FBE, UEC, coags, LFTs, ECG, CXR
- Discussion and consent
How is exercise tolerance described?
Exercise tolerance is measured in METs (metabolic equivalent).
1 MET = 3.5ml O2/kg/min
Walking on flat ground = 3 MET
Climbing 2 flights of stairs = 4 MET
Heavy housework = 5-6 MET
What is an ASA grade?
An ASA score is a subjective assessment of a patient’s overall health and physical status.
ASA 1 = fit and healthy with no systemic illness
ASA 2 = mild systemic illness
ASA 3 = severe systemic illness
ASA 4 = severe systmic illness that is a constant threat to life
ASA 5 = moribund patient not expected to survive 24 hours without operation
ASA 6 = declared brain dead person whose organs are being removed for donation
