Anaesthetics / Critical Care Flashcards
what does a pre-op assessment involve?
Hx
- PC - op, indication
- previous anaesthetics - method, problems, cx, malignant hyperthermia, sux apnoea
- DHx, allergies
- PMHx - all systems, quantify severity
- FHx
- SHx - drink, smoke, ADL, living situation
Examination
- CV, resp + abdo
- ECG, ECHO, CPET
- baseline bloods - FBC, U/E, LFTs, clotting, G+S
Airway assessment
- mouth opening
- jaw subluxation
- C-spine extension
- mallampati
- dentition
food and drinks rules before surgery?
- clear fluids >2hrs
- foods >6hrs
diabetes for operations
- on insulin with good glycaemic control (HbA1c<69) - if minor procedure - just adjust usual insulin regimen
- surgery with long fast / 1+ missed meal / poorly controlled DM - VRIII
- VRIII with OHAs if 1+ meal missed, poor glycaemic control, or risk of renal injury
rules for emergency cases needing op?
stabilise, resus, consider abx/blood
consent + inform relatives
special considerations for thyroid surgery?
Thyroid surgery – vocal cord check.
Parathyroid surgery – consider methylene blue to identify gland.
Thyrotoxicosis – lugols iodine/ medical therapy.
special considerations for SNB, thoracic duct surgery, pheochromocytoma surgery and colorectal cases
Sentinel node biopsy – radioactive marker/ patent blue dye.
Surgery involving the thoracic duct – consider administration of cream.
Pheochromocytoma surgery – will need alpha and beta blockade.
Colorectal cases – bowel preparation (especially left sided surgery)
steroid considerations for op?
- for pts on long term steroids
- major surgery - hydrocortisone with pre-med then 6-8hrly for 3d
- hydrocortisone for 24hr
Drugs to stop pre-op?
Insulin
- Sliding scale for major surgery
- Reduce bedtime dose + omit morning dose in minor surgery
Lithium
- Day before major surgery
Anticoagulants/platelets
- Warfarin 5d before with LMWH bridging (give dose vit K if INR>1.5 on day of)
- Antiplatelets 5-7d before
- Aspirin variable
cOCP/HRT
- 4wks before major, restart 2wks after
K sparing diuretics
- Day of surgery
Oral hypoglycaemics
- Metformin 48hrs before, restart 4d later when renal function ok
Perindopril / ACEi
- 24hrs before
triad of general anaesthesia + drug examples for each?
Analgesia
- fentanyl
- alfentanil
- remifentanil
- morphine
Hypnosis
IV
- propofol
- ketamine
- sodium thiopentone
- etomidate
Inhaled
- sevofluorane, desflurane, isoflurane
- NO
Muscle relaxation - block NMJ (ACh blocked)
Depolarising
- suxamethonium
Non-depolarising
- rocuronium
- atracurium
Reversal
- neostigmine (AChE inhibitor)
- sugammadex - non-depolarising
antiemetic options post op
- ondansetron - serotonin antagonist - beware long QT
- dexamethasone - corticosteroid - caution diabetics/immuno
- cyclizine - H1 receptor antagonist - caution HF/elderly
risks of GA?
- Sore throat
- Post-operative N+V
- Accidental awareness
- Aspiration
- Dental injury
- Anaphylaxis
- CV events - MI, stroke, arrhythmias
- Malignant hyperthermia
- Death
Propofol (hypnotic)
- GABA receptor agonist
- rapid onset, burns on IV injection, rapidly metabolised, anti-emetic, BP drops
- TIVA
Ketamine (hypnotic)
- NMDA receptor antagonist
- analgesia, may dissociate pt (nightmares/hallucinations), BP stable
Sodium thiopentone (hypnotic)
- barbiturate - potentiates GABA
- rapid onset, BP drops, unstable for maintenance
- lipid soluble
Etomidate (hypnotic)
- potentiates GABA
- little CV instability, may suppress adrenals
Suxamethonium (relaxant)
- depolarising - binds to AChR - persistent depolarisation at NMJ
- fast onset, muscular contraction before paralysis
- adverse effects - hyperkalaemia, malignant HTN
- CI - AACG
Atracurium (relaxant)
- non-depolarising - competitive antagonist of AChR
- lasts 30-45mins
- histamine release on administration -> facial flushing, tachycardia, hypotension
- broken down in tissues
- neostigmine to reverse
Vecuronium (relaxant)
- non-depolarising, lasts 30-40mins
- degraded by liver/kidney
- reverse with neostigmine
Pancuronium (relaxant)
- pancuronium
- 2-3min onset, 2hr duration
- partially reverse with neostigmine
Rocuronium (relaxant)
- non-depolarising
- sugammadex reversal
Lidocaine
- amide
- blocks Na channels in axon - prevents depolarisation
- hepatic metabolism, protein bound, renally excreted
- intralipid if OD
- max dose - 3mg/kg plain, 7mg/kg + adrenaline
Bupivacaine
- binds to intracellular Na channels, blocks Na influx, prevents depolarisation
- longer duration than lidocaine
- cardiotoxic
- levobupivacaine - less cardiotoxic/vasodilation
- max dose - plain 2mg/kg, +adrenaline 2mg/kg
Prilocaine
- Less cardiotoxic - used for Biers block / regional blocks
- max dose plain 6mg/kg, adrenaline 9mg/kg
Regional anaesthesia
- Numb specific nerve
- Use US to inject
- May use in combination with GA to reduce pain
Spinal anaesthetic
- Aka central neuraxial anaesthesia
- For c-sections, NOF repair, TURP
- LA injected into CSF, within subarachnoid space
- Needle inserted around L3/4 or L4/5
- Check it works with cold spray
Epidural anaesthesia + possible adverse effects
- For analgesia
- Most commonly during labour, or post-operatively after laparotomy
- Insert catheter into epidural space, outside dura mater
- Levobupivacaine +/- fentanyl inserted – diffuses into tissues + nerve roots
Adverse effects
- Headache if dura is punctured – CSF leaks from dural tap
- Hypotension
- Motor weakness in legs - urgent anaesthetic review needed – catheter may be sited in subarachnoid space
- Nerve damage
- Infection, meningitis
- Haematoma – may cause spinal cord compression
- Prolonged second stage labour
- Increased probability of instrumental delivery
tracheostomy + indications
- Hole in neck to access trachea
- Held in place with stiches or soft tie (trach tie)
Indications
- Resp failure with requirement for long term ventilation
- Prolonged weaning from ventilation (eg ICU pt weak after illness)
- Upper airway obstruction (tumour, head/neck surgery)
- Mx of resp secretions – pts with paralysis
- Reduce risk of aspiration (eg pts wth unsafe swallow / absent cough reflex)
Difficult airway stepwise plan
- Plan A - laryngoscopy with tracheal intubation
- Plan B - i-gel
- Plan C - face mask ventilation and wake pt up
- Plan D - cricothyroidotomy
ASA classifications
ASA I – normal, health patient
- Eg non-smoker, no disease
ASA II – mild systemic disease
- Mild disease, no functional limitations – eg current smoker, pregnancy, controlled DM/HTN
ASA III – severe systemic disease
- Functional limitations – eg poorly controlled DM, COPD, BMI>40, active hepatitis, >3mo ago of MI/CVA
ASA IV – severe systemic disease that is constant threat to life
- <3mo hx of MI/CVA, cardiac ischaemia, valve dysfunction, HF with reduced ejection fraction
ASA V – moribund patient not expected to survive without operation
- Eg ruptured AAA, massive trauma, intracranial bleed, ischaemic bowel
ASA VI – brain-dead patient, organs being removed for donor purposes
malignant hyperthermia- definition, Px, Ix and Mx
- hypermetabolic response to anaesthesia
- from excessive release of Ca from SR in skeletal muscle
- halothene, suxamethonium, antipsychotics
- autosomal dominant risk
Px
- hyperthermia
- increased CO2 production
- tachycardia
- muscle rigidity
- acidosis
- hyperkalaemia
Ix
- raised CK
- contracture tests with halothane + caffeine
Mx
- dantrolene - prevents Ca release from SR
IV access options
Peripheral venous cannula
- no inotropes / irritant drugs - eg TPN
Central line
- IJ, subclavian, femoral
- vas cath - 2/3 lumens
- portacath - port under skin, connects to subclavian vein
IO
- via marrow cavity
Tunnellled lines
- Gsoshong / Hickman lines
Peripherally inserted central cannula (PICC)
- insert peripherally, lumen ends centrally
- pulmonary artery catheter - Swan-Ganz
Nutrition in surgical patients
Oral
- easiest
- CI’d after certain procedures
NG
- via fine bore NG tube
- Cx - aspiration of feed, misplaced tube
- eg impaired swallow
- CI’d head injury
Nasojejunal
- avoids problems of feed pooling in stomach + aspiration risk
- insertion more complicated
Feeding jejunostomy
- surgically sited feeding tube
- can be long term
- low asp risk
Percutaneous endoscopic gastrostomy (PEG)
- Combined endoscopic and percutaneous tube insertion
- must be able to tolerate OGD
TPN
- where enteral feed CI’d
- need central line - phlebitis risk
- long term use - fatty liver, deranged LFTs
post op pyrexia?
Early causes (0-5d)
- Blood transfusion
- Cellulitis
- UTI
- Physiological systemic inflammatory reaction (usually within day)
- Pulmonary atelectasis
Late causes (>5d)
- VTE
- Pneumonia
- Wound infection
- Anastomotic leak
4 Ws – wind, water, wound, what did we do (iatrogenic)
Cx of periop hypothermia
- Coagulopathy, increased blood loss
- Prolonged anaesthetic recovery
- Reduced wound healing - local vasoconstriction
- Infection - poor site healing, reduced no of immune cells
- Shivering - increased metabolic rate, myocardial ischaemia in some populations
VTE prophylaxis
RFs
- reduced mobility, ortho surgery, >90mins surgery, acute surgical admission, cancer/chemo, >60yo, thrombophilia, BMI>35, comorbidities, critical care admission, HRT/cOCP, varicose veins, pregnant, <6wks post partum
Mx
- compression stockings
- intermittent pneumatic compression device
- fondaparinux / enoxaparin / heparin / doac
- mobilise asap after surgery, ensure hydrated
wound healing steps
- haemostasis
- inflammation
- regeneration
- remodelling
scar types
Hypertrophic scars
- excessive collagen
Keloid scars
- excessive collagen, extends beyond scar
Drugs which impair wound healing
- NSAIDs, steroids, immuno, anti-neoplastic
Closure
- delayed primary - leave open, close before granulation tissue forms
- secondary - allow granulation tissue to form
what are the 3 levels of care?
Level 1 - general acute ward
Level 2 - HDU
Level 3 - ICU - needing organ support
Scoring systems to predict mortality at ICU admission
APACHE - acute physiology and chronic health evaluation
SAPS - simplified acute physiology score
MPM - mortality prediction model
ICU cx
-ventilator-associated lung injury - volutrauma, barotrauma….
- VAP
- catheter-related bloodstream infections
- catheter-associated UTIs
- mucosal disease
- deliriun
- VTE
- critical illness myopathy / neuropathy
