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