Anaesthetics Flashcards
(26 cards)
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
