Anaesthetics Flashcards
Contraindications to suxamethonium
Contraindicated:
− Severe hyperkalaemia
− In suspected muscular dystrophies, congenital myopathies or neurological disease involving extensive muscle wasting;
− Personal or family history of malignant hyperthermia;
− Severe metabolic acidosis with hypovolaemia and prolonged use of nondepolarising muscle relaxants due to the risk of suxamethonium-induced hyperkalaemia and cardiac arrest
> Use with caution in conditions such as electrolyte imbalance, severe sepsis, uraemia, burns (hyperK)
Difficult BVM: patient factors
Difficult BVM = BONES
Beard
Obese
No teeth
Elderly
Sleep Apnea / Snoring
Modified post-anaesthetic discharge score
Usually safe for discharge if score >/= 7
Difficult laryngoscopy: patient factors
Difficult intubation = LEMON
Look externally
Evaluate 3-3-2 rule
- Mouth opening 3 fingers
- Mandible to hyoid 3 fingers
- Mandible to thyroid notch 2 fingers
Mallampati score II-IV
Obstruction
Reduced neck Mobility
Drugs for RSI in suspected head injury
Ketamine
Dose - 1mg/kg, lower dose as drowsy
Advantages - Maintains BP and CPP, hypotension associated with worse outcome
Disadvantages - Previous concerns about raised ICP, however recent evidence and practice suggests this is same
Thiopentone
Dose - 3-5mg/kg, lower end more appropriate if drowsy
Advantages - Cerebroprotective function, anticonvulsant
Disadvantages - Significant chance of hypertension in higher doses, may need vasopressor use post-induction, less familiarity with staff
Why is paeds moving to cuffed rather than uncuffed tubes?
Narrowest part of paed airway subglottic.
Older paed ETTs - small volume, high pressure cuffs made of poorly tolerated materials leading to tracheal injury & subsequent subglottic stenosis.
Newer devices - larger volume, lower pressure cuffs
Median nerve block technique
- Consent, position patient
- Universal precautions, clean skin, aseptic technique
- Identify site of injection: proximal wrist crease, between FCR and PL tendons
- Inject 3-5ml at 10-15mm using 25G needle (or ultrasound guided)
- Infiltrate superficially, proximal to flexor retinaculum for palmar cutaneous branch
- Check block and record procedure in notes
Max. dose local anaesthetics
Symptoms of local anaesthetic toxicity (LAST)
Premonitory CNS symptoms
* dizziness
* tinnitus
* perioral tingling
* unresponsiveness
* agitation
* nystagmus
* muscle twitches
* potentiated by hypercapnia and acidosis
Seizures
* usually self-limiting due to drug re-distribution
- premedication with benzodiazepines provides significant prophylaxis
CNS depression
Cardiovascular
* hypotension
* arrhythmias
* bupivacaine most cardiotoxic
Treatment of local anaesthetic toxicity
Limit LA exposure
* Prolonged normal resuscitation
* Consider lipid emulsion administration
* Prevention of acidosis
* Mild symptoms – midazolam boluses IV (raises seizure threshold)
* Stop injecting or infusion!
* Call for help
o A – ETT
o B – FiO2 1.0, hyperventilate (avoid acidosis -> HCO3- 1mmol/kg)
o C – defibrillation, CPR, fluid, inotropes, amiodarone 5mg/kg,
o D – midazolam, propofol, thiopentone
o Lipid emulsion (20% intralipid)
- 1 mL\kg (over 1min) q3min x 3
- then Infusion 0.25mL\kg\min
Contraindications
- hypersensitivity to egg, soya or peanuts
Respiratory physiology of obesity - difficult airway
*high incidence of resting hypoxaemia and hypercarbia in the absence of underlying lung disease
*reduced TLC and VC due to
- decreased chest wall compliance
- increased abdominal cavity contents
*increased airway resistance
*decreased expiratory reserve volume from collapse of the small airways
- causes decreased basilar ventilation and VQ mismatch
- exacerbated by the supine position, sedation and paralysis
*FRC declines exponentially as BMI increases
- smaller oxygen reserve with pre-oxygenation
- 50% shorter time to oxygen desaturation
*increased oxygen consumption and carbon dioxide production
*inefficient respiratory muscles
*increased airway soft tissues
Initial ventilator settings in asthma
- Needs a safe approach. Mention permissive hypercapnia & lung protective strategy
- Tidal volume - low side - maximum of 8ml/kg (5-8)
- RR – may need to be low – 6-8 breaths/min start at 10 bpm, but be prepared to titrate
down - I:E ratio – > 1:2, may need to be 1:5. May need to adjust inspiratory time to achieve
- Fi02 titrated to keep SpO2 > 92-94%
- PEEP – controversial 0 – 5 mmHg (may have autopeep)
- Limits – Peak insp < 40, target plateau pressure < 20 cmH2O
Causes of climbing airway pressures in ventilated asthmatic patient
- Progression of disease – worsening bronchospasm
- Pneumothorax
- Air trapping/dynamic hyperinflation
- Mucous plugging (bronchial, endotracheal tube)
- Ventilator malfunction, inappropriate settings
- Patient-ventilator dysynchrony
Approach to analgesia in paediatric orthopaedic injury
- Opiate analgesia- IN fentanyl 1-1.5mcg/kg, IV morphine 0.1mg/kg
- Oral analgesia- paracetamol 15mg/kg, Ibruprofen 10mg/kg or codeine based
- Regional analgesia, as appropriate e.g. femoral nerve block/ FIB
- Non pharmacological- splint- Thomas splint/ traction
- Reassurance/ distraction by parents- (NOT adequate as only answer)
Signs of life-threatening asthma - need for intubation
- Drowsiness
- Collapse
- Refractory Hypoxia
- Bradycardia
- Apnoea
- Silent Chest
- Poor resp effort
- Investigative findings –relative hypercapnoea
Augmentation of intubation in patient with hypoxia and hypotension
- Fluid load – 0.9% saline 10ml/kg bolus, repeat to SBP >100mmHg
- Augmented induction agent – ie ketamine IV at reduced dose ie 0.5-1mg/kg, rocuronium 1.2mg/kg
- Co-administration of inotrope at induction – 1mcg/kg adrenaline with induction
- Optimised pre-oxygenation with ongoing NRBM at 15lpm PLUS NP O2 at 15lpm
- NP O2 at 15lpm throughout induction stage
- Mitigate hypoxia/acidosis by bagging through induction with BVM O2 at 15lpm
- Intubate at 30 degrees to minimise risk of hypoxia
Causes and treatment of post-intubation hypotension
- Acidosis - Hyperventilation, bicarbonate administration
- Anaphylaxis - Adrenaline iv
- Pericardial tamponade - Decompress
- Breath stacking - Disconnect tube, compress chest, alter ventilator settings, bronchodilators
- Hypovolaemia - IV fluid bolus
- Induction agent effect - Supportive management, fluid, pressors
- Tension PTX - Finger thoracostomy
- Electrolyte abnormalities - Identify and correct
Differences between paediatric and adult airway
- Smaller mandible
- Larger head and occiput
- Paediatric airways
- Tongue is relatively larger
- Epiglottis is longer and floppier
- Larynx is higher and more anterior
- Narrowest part is cricoid ring (subglottic) (until about 5 years)
- Airway is shorter and narrower
Management of laryngospasm
- Stop the procedure
- Call for expert help
- Administer 100% oxygen through a mask with a tight seal and a closed expiratory valve
(trying to force vocal cords open with positive pressure) - Suction to clear the airway of any blood or secretions
- Attempt manual ventilation while continuing to apply continuous positive airway
pressure (CPAP) - Attempt to break the laryngospasm by applying painful inward and anterior pressure at
Larson’s point/laryngospasm notch bilaterally while performing a jaw thrust - Consider deepening sedation (low dose propofol) to reduce laryngospasm
- If hypoxia continues, consider administering suxamethonium (0.1 – 0.5mg/kg). If severe,
need full dose (1-2mg/kg IV) and perform intubation. If no IV access, can give IM sux (3-
4mg/kg) - For bradycardia, atropine (0.02mg/kg)
Causes of hypercarbia following intubation
1) Increased CO2 production – fever, thyrotoxicosis
2) Increased pulmonary perfusion – High CO, hypertension
3) Poor alveolar ventilation – hypoventilation, bronchial intubation
4) Technical mechanical errors – leak or faulty valve
5) Underlying lung pathology (refer to bicarb for suggestion)
Criteria for extubation in ED
- Resolution of underlying issue that caused need for intubation
- Spontaneously breathing
- Resp parameters: O2 sats > 95% on FiO2 < 40%, PEEP < 5, RR < 30, TV > 6mL/kg
- Haemodynamic stability without need for inotropic support
- Sedation & paralysis worn off
- Not a difficult intubation
- Obeys commands
- Ideally: Significant medical comorbidities that may make extubation complicated such as asthma, OSA, cardiomyopathy.
Bonus non-clinical criteria:
- Staff skilled in managing extubation (Nursing & Medical)
- Staff available who can re-intubate if required
- Equipment available for re-intubation
- Rest of department workload suitable
- No more suitable place for this to occur (eg no ICU beds)
Equipment for safe extubation in ED
- Suction
- O2 mask & supply
- NIV set-up
- Intubation drugs & paralysis agents (Suxamethonium 1.5mg/kg drawn up)
- Equipment for urgent reintubation
Principles of ventilation in asthma
Ventilation should be a last option management in Asthmatics. It is very difficult to replicate the abnormal physiology of an asthmatic with ventilation.
Principles:
- I:E Ratio > 1:3 (4-8)
- Low rate (~8/min)
- Permissive Hypercapnoea
- Avoid hypoxia – FiO2 100%
- Tidal Volume (5-6ml/kg)
- PEEP 0-2mmHg – avoids dynamic hyperinflation and reduces risk of auto-peep
- Frequent pauses from ventilator
Causes of stridor in paediatric population
Croup
Bacterial tracheitis
Epiglottitis
Retropharyngeal abscess
Laryngeal FB
Angioneurotic oedema
Subglottic haemangioma
Laryngomalacia
Complications of extubation in ED and management of each
Cough/sore throat - Analgesia
Increased sympathetic response - Analgesia, GTN, cease any inotropes
Laryngospasm - Jaw thrust, Larsen’s point pressure, positive-pressure ventilation, suction, low dose sux, prepare for re-intubation
Bronchospasm - bronchodilators
Aspiration - Positioning, chest physio, antibiotics
Respiratory failure - NIV, re-intubation if required
Steps to trouble-shoot hypoxia in suspected blocked tracheostomy
Apply FiO2 100% to face and tracheostomy
-> Remove inner cannula or speaking valve and attempt FiO2 100% BVM
-> If not resolved, attempt to pass suction catheter and oxygenate via tracheostomy
-> If not able to pass suction catheter: deflate cuff and attempt to allow patient to breathe around or BVM applied around tracheostomy
-> If unable to do this, remove tracheostomy and attempt replacement
-> If unable to replace then proceed to RSI with direct laryngoscopy or surgical airway depending on indication for tracheostomy
