Anaesthetics + Critical care Flashcards
1
Q
Pre-op assessment
A
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, rest etc
- ECG, ECHO, CPET
- baseline bloods - FBC, U/E, LFTs, clotting, G+S
Airway assessment
- mouth opening
- jaw subluxation
- C-spine extension
- mallampati
- dentition
2
Q
Food/drink before surgery
A
- clear fluids >2hrs
- foods >6hrs
3
Q
Diabetes for op
A
- 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
4
Q
Emergency cases for op
A
stabilise, resus, consider abx/blood
consent + inform relatives
5
Q
Special preparations for surgery
A
Thyroid surgery – vocal cord check.
Parathyroid surgery – consider methylene blue to identify gland.
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.
Surgery for carcinoid tumours – will need covering with octreotide.
Colorectal cases – bowel preparation (especially left sided surgery)
Thyrotoxicosis – lugols iodine/ medical therapy.
6
Q
Steroids for op
A
- for pts on long term steroids
- major surgery - hydrocortisone with pre-med then 6-8hrly for 3d
- hydrocortisone for 24hrs
7
Q
Drugs to stop pre-op
A
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
8
Q
Triad of general anaesthesia
A
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
9
Q
Antiemetics post-op
A
- ondansetron - serotonin antagonist - beware long QT
- dexamethasone - corticosteroid - caution diabetics/immuno
- cyclizine - H1 receptor antagonist - caution HF/elderly
10
Q
Emergence
A
- waking up whilst paralysed
- use nerve stimulator
- Train of four (TOF) stimulation - muscle twitches 4x with same strength if worn off (weakens if not)
11
Q
Risks of GA
A
- Sore throat
- Post-operative N+V
- Accidental awareness
- Aspiration
- Dental injury
- Anaphylaxis
- CV events - MI, stroke, arrhythmias
- Malignant hyperthermia
- Death
12
Q
Propofol (hypnotic)
A
- GABA receptor agonist
- rapid onset, burns on IV injection, rapidly metabolised, anti-emetic, BP drops
- TIVA
13
Q
Ketamine (hypnotic)
A
- NMDA receptor antagonist
- analgesia, may dissociate pt (nightmares/hallucinations), BP stable
14
Q
Sodium thiopentone (hypnotic)
A
- barbiturate - potentiates GABA
- rapid onset, BP drops, unstable for maintenance
- lipid soluble
15
Q
Etomidate (hypnotic)
A
- potentiates GABA
- little CV instability, may suppress adrenals
16
Q
Suxamethonium (relaxant)
A
- depolarising - binds to AChR - persistent depolarisation at NMJ
- fast onset, muscular contraction before paralysis
- adverse effects - hyperkalaemia, malignant HTN
- CI - AACG
17
Q
Atracurium (relaxant)
A
- non-depolarising - competitive antagonist of AChR
- lasts 30-45mins
- histamine release on administration -> facial flushing, tachycardia, hypotension
- broken down in tissues
- neostigmine to reverse
18
Q
Vecuronium (relaxant)
A
- non-depolarising, lasts 30-40mins
- degraded by liver/kidney
- reverse with neostigmine
19
Q
Pancuronium (relaxant)
A
- pancuronium
- 2-3min onset, 2hr duration
- partially reverse with neostigmine
20
Q
Rocuronium (relaxant)
A
- non-depolarising
- sugammadex reversal
21
Q
Lidocaine
A
- 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
22
Q
Cocaine
A
- salt, supplied in paste
- apply to nasal mucosa
- used in ENT
23
Q
Bupivacaine
A
- 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
24
Q
Prilocaine
A
- Less cardiotoxic - used for Biers block / regional blocks
- max dose plain 6mg/kg, adrenaline 9mg/kg
25
Regional anaesthesia
- Numb specific nerve
- Use US to inject
- May use in combination with GA to reduce pain
26
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
27
Epidural anaesthesia
- 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
28
Tracheostomy
- 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)
29
Difficult airway
- Plan A - laryngoscopy with tracheal intubation
- Plan B - i-gel
- Plan C - face mask ventilation and wake pt up
- Plan D - cricothyroidotomy
30
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
31
Malignant hyperthermia
- 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
32
IV access
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
33
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
34
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)
35
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
36
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
37
Wound healing
- haemostasis
- inflammation
- regeneration
- remodelling
....
38
Scars
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
39
Pain mx
Various bits + bobs in notes
....
40
Levels of care
Level 1 - general acute ward
Level 2 - HDU
Level 3 - ICU - needing organ support
41
Scoring systems to predict mortality at ICU admission
APACHE - acute physiology and chronic health evaluation
SAPS - simplified acute physiology score
MPM - mortality prediction model
42
Nutritional support in ITU
- dietician involvement
- enteral - mouth, NG tube, PEG
- TPN - via central line
43
ICU cx
-ventilator-associated lung injury - volutrauma, barotrauma....
- VAP
- catheter-related bloodstream infections
- catheter-associated UTIs
- mucosal disease
- deliriun
- VTE
- critical illness myopathy / neuropathy
44
CV / resp / renal support
see notes.....
