Pre-induction Anaesthesia Flashcards
What are the patient factors that need to be verified pre-induction?
- Correct patient for correct procedure
- R/v of medical conditions and recent changes to health status, e.g. URTI
- Confirm fasting times + drug intake and allergies
- R/v of baseline parameters, medication charts, investigation results
- Remind patient of anaesthesia plan, reinforce risks
- Obtain consent
- IV cannulation (establish IV access) (inject LA lignocaine as needle gauge is large)
What are the equipment and drugs that need to be checked induction?
Check anaesthesia machine (ensure it is working, have soda lime, no leaks in gas circuit, etc), check suction
- Fresh gas flow (FGF)
- Manual mode (when patient spontaneous breathing), ventilator mode (when patient not spontaneously breathing; machine ventilates pt)
- Pink granules = soda lime; chemically removes expired CO2
Dilute and draw drugs – amnesia (sedation), analgesia, akinesia (muscle relaxant)
Check airway equipment: ETT + laryngoscope or LMA, tapes, syringe to inflat
Warm fluids
Standby blood products (if needed)
What patient vitals are under standard ASA monitoring?
ECG, pulse oximetry (SpO2), non-invasive BP (NIBP), ETCO2, partial pressure of anaesthetic gases (see Monitoring)
- ECG, SpO2: continuous
- NIBP: every 3-5 mins (machine measured)
- ETCO2: concentration, waveform morphology is important (at higher levels of anaesthesia training)
- Gas analyser (ETO2, ET(gases)): important to record, in order to prevent delivery of hypoxic gas mixture
What patient vitals are under non standard ASA monitoring?
Temperature:
- Nasopharyngeal (NP)/ oropharyngeal (OP) probes
- E.g. in laparotomy with high evaporative losses
JVP/CVP line: Trending intravascular volume status, e.g. in surgeries with anticipated major blood loss (or in patients with poor cardiac reserve)
IA line
EEG
- Neurological monitoring (increasingly performed routinely/standard)
- Ensures appropriate depth of anaesthesia (deep enough + not too deep)
What are the advantages of IV induction of anaesthesia?
☺ Fast onset – within 1 arm- brain circulation (if using propofol)
☺ Smooth and predictable
☺ Non-noxious to airway
☺ Allow for rapid sequence induction [RSI] (reduce aspiration risks)
☺ Suitable for most patients
What are the advantages of inhalational induction of anaesthesia?
☺ good for those w/ difficult IV access (e.g. paediatric, poor venous access, severe anxiety or needle phobia)
☺ good for those w/ airway anatomy that may collapse* and lead to airway obstruction w/ loss of muscle tone/spontaneous respiration, e.g. mediastinal mass, epiglottitis, airway FB
Reason: inhalational agents act MUCH slower than IV – effects of sedation but allows spontaneous breathing, just require pressure support on ventilator. Spontaneous breathing generates negative intra-thoracic pressure 🡪 keeps airway patent
What are the disadvantages of IV induction of anaesthesia?
☹ requires IV access – may be difficult in paediatric patients or difficult IV access (e.g. small veins)
☹ Fast onset of respiratory depression and apnoea – requires early support of airway and ventilation
☹ S/E of specific drugs, e.g. hypotension, cardiorespiratory depression
What are the disadvantages of inhalational induction of anaesthesia?
☹ noxious smell of gas
☹ requires patient (+parent) cooperation
☹ slow onset (also quick offset once stopped)
☹ risk of laryngospasm, coughing or involuntary movements
☹ environmental pollution
In what kind of surgeries are laryngeal mask airway used?
- Used in non-abdominal surgery (e.g. TKR, TURP, etc)
- Used in short surgeries w/o need for airway protection
- Used when ventilation is expected to be easy (when high pressures are not expected, e.g. patient is not obese)
What are the indications for intubation (ETT)?
Required for controlled airway and mechanical ventilation
Shared airway surgeries, e.g. ENT, maxillofacial (surgeries where definitive airway is important)
Difficult position during surgery, e.g. prone
Long surgeries
Surgeries requiring paralysis and relaxation
Protection against aspiration
Required for tracheal suctioning
How to confirm that ETT is intubated?
- Direct visualisation of intubation
- Misting of ETT with ventilation
- Bilateral chest rise, compliance of lung inflation
- Clinical auscultation at 5 points (epigastrium (r/o gurgling), bilateral apices and bases (r/o endobronchial and adventitial sounds))
- Detection of end tidal CO2 (ETCO2)
- CXR (not routinely done)
What are the complications of intubation?
- Trauma to lips, teeth/crown, larynx
- Laryngeal oedema and stridor post-operatively
- Nasal intubation 🡪 may cause epistaxis
- Hypoxaemia 2’ to failure to oxygenate/intubate
- Bronchospasm
- Haemodynamic effects – arrhythmias, hypertension (HTN)
What is permissible to eat > 8 hours before operation?
Food and fluids as desired
What is permissible to eat > 6 hours before operation?
Light meal (e.g. toast + clear liquids**); infant formula; non-human milk
What is permissible to eat > 4 hours before operation?
Breast milk
What is permissible to eat > 2 hours before operation?
Clear liquids** only; no solids or foods containing fat in any form
In which patients are RSI used?
Used in patients who are at increased risk of gastric aspiration
- Inadequate fasting time, e.g. emergency surgery
- Delayed gastric emptying, e.g. post-trauma, morbid obesity, etc
- Raised intra-abdominal pressure, e.g. obesity, pregnancy
- Anatomical, e.g. intestinal obstruction (IO), hiatus hernia, active reflux (GERD)
What are the physical factors affecting mask ventilation?
- Presence of beard
- BMI > 26
- Missing teeth
- Age > 55
- History of snoring
What are some CVS related history to take pre- surgery?
Known conditions
- IHD, previous AMI, arrhythmias, coronary disease, carotid artery stenosis
- Cardiovascular risk factors (CVRF): DM, HTN, HLD, smoking
- Decompensated heart failure (HF): refer to cardiovascular medicine (CVM), postpone surgery
- Functional murmur (soft + change/disappears with change in posture) 🡪 Ix: 2DE (TTE)
Symptoms (if new/worsening, must re-evaluate cardiac status)
- Shortness of breath (SOB), chest pain, chest tightness, palpitations
- Stable/unstable angina
- Swelling, orthopnoea, paroxysmal nocturnal dyspnoea [fluid overload]
Medications (DHx)
- Anticoagulants, antiplatelets
Diuretics
- Antihypertensives – BP under control is better than uncontrolled
Investigations (Ix)
- Last 2DE (TTE/TOE)
- Last stress test
*Determine a patient’s functional capacity/effort tolerance (in metabolic equivalents of task [METs])
What are some respi related history to take pre- surgery?
Patient-related risk factors (for perioperative pulmonary complications)
- Smoking
- Poor general health status (ASA > 2)
- Old age (> 70)
- Obesity
- COPD, asthma, ILD
- Inhalers (and colour), current symptoms/control (e.g. SOB)
- Refer to RM for assessment, optimisation of condition
- Previous TB, bronchiectasis
- Pneumonia 🡪 urgent referral to respiratory medicine (RM), postpone surgery
- *Recent URTI symptoms (runny nose/coryza, cough, sore throat)
- Cx: increased airway reactivity 🡪 increased risk of laryngospasm, bronchospasms during airway manipulation (during inhalation of anaesthesia, during intubation, etc)
- Cx: pooling of secretions in lung, as lung cannot cough sputum out during GA 🡪 increased risk of pneumonia
- ascertain symptoms + time course (fever, rhinorrhoea, sore throat, productive cough, general malaise, myalgia, within 2 week of planned date)
What are some hepatic and gi related history to take pre- surgery?
hiatal hernia, diarrhoea, bloody stools, heartburn, food regurgitation, gastric ulcers, nausea, vomiting, viral hepatitis (e.g. hep B), alcohol intake
Indications for rapid sequence induction (RSI) (i.e. high risk of aspiration)
- **N&V, regurgitation, GERD/reflux
- Surgical condition affecting abdominal viscera (e.g. acute appendicitis, acute cholecystitis) (risk of paralytic ileus and delayed gastric emptying)
- Raised intra-abdominal pressure, e.g. obesity, pregnancy
What are some endocrine
related history to take pre- surgery?
Diabetes mellitus (DM)
- Type, duration, severity
- Current therapy (diet, oral hypoglycaemic agent [OHGA], insulin)
- Morning blood glucose, HbA1c (determine control)
- Evaluate for IHD, HTN (because DM is a CVRF)
- Serum creatinine (assess DM nephropathy)
- Patients are instructed to take half their morning dose of insulin on the day of surgery but NOT omit it entirely
- Should be scheduled for elective surgery early in the day (first case preferable) to minimise impact of prolonged fasting on glycaemia management
- Start IV dextrose drip, if given insulin or CBG < 5.5
What are some renal related history to take pre- surgery?
“Have you been told that you have kidney problems?” (renal insufficiency, renal failure, dialysis dependence)
Do not need to ask about symptoms, as it cannot quantify degree of renal failure – instead check previous serum creatinine and medications
What are some neurologic related history to take pre- surgery?
Cerebrovascular accidents (CVA/stroke), seizures/epilepsy
Convulsions, tremors, headaches, nerve injuries, multiple sclerosis, tingling, numbness of extremity
Use of neuraxial blockade or regional nerve block (RNB) requires knowledge of any previous nerve injuries or deficits
What are some MSK related history to take pre- surgery?
Cervical spine pathologies, e.g. ankylosing spondylitis, cervical spondylosis with cervical myelopathy 🡪 be careful when mobilising neck for intubation
MSK disorders (e.g. myopathies) 🡪 be careful in giving neuromuscular blockade/muscle relaxants
For rheumatoid arthritis (RA) patients 🡪 Ix: XR dynamic view C spine for atlantoaxial joint instability (C1/C2 joint) 🡪
if instability present 🡪 avoid airway manipulation, attempt awake fibre optic intubation instead
Any aches and pains – warn/counsel about back stiffness and pain from lying in a strange position
Low back pain, radicular pain, prolapsed IV discs, chronic pain managed with opioids
What are the medications that need to be witheld during surgery?
ARB, ACEi – withhold on morning of surgery (to avoid intraoperative profound hypotension); other antihypertensives are continued to maintain good BP control pre-op
Check whether certain medications have been stopped, e.g. aspirin (may need to stop 7-10 days before surgery), warfarin and NOACs (e.g. warfarin to be stopped for 5 days (risk of thrombosis scored using CHA2DS2-VASc score 🡪 if high risk 🡪 bridging with heparin (Clexane)), DM medications (if continued, may cause hypoglycaemia due to concurrent need for prolonged fasting before surgery)
Traditional medications/supplement use (steroid content, antiplatelet effect)
Some medications need to be stopped for some types of surgery (e.g. antiplatelet agents). Recent drug eluting stent in a patient with recent MI 🡪 is a C/I to stopping dual antiplatelet therapy (DAPT) 🡪 postpone surgery until a more optimal date/optimal time
How to screen patients with OSA?
Symptoms - STOP
- Snoring loudly (louder than talking, or loud enough to be heard through closed doors?)
- Tired, fatigued, sleep during daytime?
- Observed you stop breathing during your sleep?
- Pressure (do you have, or are you treated for HTN
Demographics - BANG
- BMI > 35
- Age > 50
- Neck circumference > 40 cm
- Gender: Male
What are the common temporary side effects from anaesthesia?
- dizziness
- sore throat
- pain or bruising at injection sites
- nausea & vomiting
- blurred vision
- shivering
What are the infrequent complications from anaesthesia?
- muscle pains
- headaches
- allergic reactions
- temporary breathing difficulties
- damage to teeth, dental prosthesis
- damage to voice box which may cause temporary loss of voice
- damage to nerves or pressure areas
- chest infection
What are the extreme rare & serious complications from anaesthesia?
- severe allergic reactions
- permanent nerve damage
- damage to eyes
- awareness under GA
- brain damage
