Surgery Flashcards
What are the 7 steps of a pre-op assessment?
- patient ‘clerked’
- physical exam
- procedure explained, consent forms signed
- opportunity for questions
- discuss post-op care
- meds rec
- peri-operative medicines management
What are the 8 steps of the elective surgical pathway?
Patient sees GP
Referred to specialist
Diagnosis
Adjunct treatment (e.g. chemotherapy)
Decision made for surgery
Patient usually seen at pre-operative assessment clinic a few weeks pre-op
Patient arrives in Admission Suite 07:30 – morning of surgery
What are the 8 checks for pre-op fitness?
- Blood tests – eGFR, Hb, Crossmatch
- Weight – important for medication doses
- MRSA screen and eradication
- BP – may need treatment
- Cardiac function: ECG / ECHO
- HbA1c – optimise diabetes management pre-op
- Medication history
- Prescribing e.g. anticoagulant bridging therapy
What does NBM pre-op mean?
Technically nil-by-mouth, but small sips of water and usual medications are okay (if given go-ahead)
6 hours fasted for food, up to 170ml/hr non-milky fluids
Why is the meds rec done pre-op?
If not performed, no accurate source of medication to inform prescribing
Potential for critical missed doses
Pre-op patient is alert, with family / carer, medication is available
Post-op patient is drowsy, family not available, medication may have been sent home
Why are there specialist pre-op pharmacists?
In pre-op assessment clinics
Medication experts that can ensure appropriate advice given on management of long terms conditions
Minimise post-op complications
Prepare patient for discharge
Stable workforce compared to rotating junior doctors
What is the procedure on the morning of surgery?
Patients arrive 07:30
First operation scheduled for 08:00
Surgeon finalises operation detail and consents patient
Anaesthetist ensures fit to proceed
Nurse gives pre-meds, TED stockings, takes observations
Re-check of medicines reconciliation
What is the procedure during and after surgery?
Operation takes place in theatre (intra-operative period)
Recovery – woken up, orientated, pain relief, PONV prophylaxis
Patient sent to ward (post-operative period)
Duration of stay depends on:
Surgical procedure
Previous co-morbidities
Need for IV medication (pain relief, antibiotics)
Post op complications
Enhanced recovery pathway
What are the pre-op considerations for Warfarin?
- it has a long half life, so stop 5 days before surgery
- INR must be under 1.5 to proceed with surgery
What are the post-op considerations for Warfarin?
- usually restart asap after surgery depending on bleed risk
- consider all bleeding risks (wound, internal, epidural)
- can use LMWH as prophylaxis/bridging therapy if bleeding risk is high
What are the considerations for Warfarin for emergency surgery?
- give vitamin K within 4-24 hours, best if surgery can be delayed 4 hours
- not always best as you can go too far with it
What are the main reasons for anti-coagulant therapy?
Mechanical Heart Valves:
- Depends on type of valve
- Generally considered high risk of thrombosis if anticoagulation held
- “Bridging” usually needed
Deep Vein Thrombosis or PE:
- Risk is very high in first 3 months post thrombosis
- If >3 months: Most patients can receive just prophylactic dose LMWH post procedure
- “Bridging” may be needed if recurrent DVTs/PEs or in last 3 months
Atrial Fibrillation:
- Depends on thrombosis risk: previous TIAs and CHADS2 score
What are the considerations for DOACs for elective surgery?
- short acting so wear off, bridging not usually required
- stopping time varies as clearance rate varies (renal function, drug half-life)
- Bridging not usually required as can usually stop prior to surgery
What are the consideration for anti-platelets?
- aspirin: if under 150mg, continue, if over 150mg, reduce until under
- clopidogrel: stop 7 days pre op, sub for aspirin if possible
- however different considerations for cardiac surgery and dual antiplatelet
What are the considerations for restarting antiplatelets and DOACs?
- usually restart DOACs within 24-72 hrs, with considering all bleeding risks
- DOACs can be covered with LMWH prophylactic dose
- antiplatelets can be continued from morning after
What are the considerations for cardiac medications?
- surgery can increase HR and BP so meds continued
- ACEi/ARB + diuretics may be omitted due to risk of hypotension
- always continue beta blockers, digoxin, anti-arrhythmics
What are the considerations for long term steroid therapy?
- patients on steroids may have pituitary-adrenal suppression and natural stress response impairment which leads to circulatory collapse
- stress from surgery causes plasma adrenocorticotrophic hormone and cortisol levels to rise
- all oral steroids considered, other routes sometimes
What are the steroid replacements for minor surgeries?
- usual dose in morning
- or hydrocortisone 25-50mg IV
- recommence after surgery
What are the steroid replacements for moderate/major surgeries?
- usual dose morning of, + hydrocortisone 100mg IV
- hydrocortisone 25-50mg IV TDS between 24-72 hrs post-op
What are the considerations for non-insulin hypoglycaemics?
- continue metformin, pioglitazone, DDP4 inhibitors, GLP-1 analogues, restart when eating and drinking normally
- omit SGLT2 inhibitors 24-72 hrs pre-op and restart once E+D restarted and VRII stopped
What are the considerations for short-acting insulins?
- omit doses for meals skipped while NBM
- restart when VRIII stopped and eating post-op
What are the considerations for long/intermediate insulins?
- continue at 80% of usual dose throughout surgery
What are the considerations for mixed insulins?
- halve usual morning dose
- restart post-op if adequate oral intake
What is VRIII?
- two IV lines
- line 1: 50 units actrapid in 50ml saline
- line 2: 500ml 5% dextrose over 5 hrs
- aim for 6-10 mmol L-1 for VRIII
- continue long acting and GLP-1 analogues
What are the considerations for HRT?
- Oestrogen containing birth control caries 3x risk of VTE
- mini pill carries no extra risk
- suggest stopping COCs 4-6 weeks prior to major surgery
What must be done for a patient on HRT needing emergency surgery?
Thromboprophylaxis
What are the considerations for Tamoxifen?
- carries increased VTE risk
- consider stopping 4 weeks before surgery
- always discuss with oncologists
What are the considerations for MAIOs?
- potentially fatal interactions
- reduce and stop 2 weeks before or
- switch to reversible MAIO or
- choose MAIO-safe anaesthetic
What are the potential interactions for MAIOs?
- analgesics - CNS toxicity or increased convulsant risk
- sympathomimetics - increased risk of hypertensive crisis
What are the considerations for Lithium?
- fluid imbalance can precipitate toxicity
- preferably stop 1-2 days before surgery
- if continued
- monitor lithium levels and fluid
- avoids NSAIDs
What are the considerations for anti-convulsants?
- continuation is essential
- consider by alternative routes if NBM
What is an ‘-ectomy’?
removal of
What is an ‘-otomy’?
opening of
What is an ‘-ostomy’?
bring to surface
What is an ‘-scopy/scopic’?
looking into
How can you check the status of your post-op patient?
General appearance
Signs e.g. NBM, free-fluids (FF), E&D
Fluids, drains, NG tubes
TPN, enteral feeds
Pumps e.g. PCA, epidural, heparin, Sliding scale
Mobility
Vomit bowl
Oxygen requirement
Dressings
What are the considerations for antibiotic prophylaxis?
- type of surgery
- duration depends on degree of contamination
- drug depends on causative organism
- IV route preferred
What are the three degrees of contamination?
Clean
- non-traumatic, no inflammation, no break in technique
Clean-contaminated
- non-traumatic but breach in technique or unsantiary area
Contaminated
- major break in technique
- gross spillage
- traumatic wounds
What is virchow’s triad of VTE risk?
- prothrombotic change
- vascular wall injury
- circulatory stasis
What are the 3 actions of VTE prophylaxis?
- mobilise patient asap
- avoid dehydration
- stop meds that increase risk
What are the 2 mechanical ways of VTE prophylaxis?
- stockings
- intermittant pneumatic compression devices
What are the 4 pharmalogical solutions of VTE prophylaxis?
- LMWH
- UFH
- DOACs
- fondaparinux
What is the reccomended VTE prophylaxis for a hip replacement?
- LMWH for 10 days, aspirin for next 28 days or
- LMWH + AES for 28 days or
- DOAC OD for 35 days
What is the reccomended VTE prophylaxis for a knee replacement?
- aspirin 75-150mg OD for 14 days or
- LMWH + AES for 14 days or
- Rivaroxaban 10mg for 14 days
Why must pain be well managed?
↓ Recovery & ↑ length of stay
↓ Mobility & ↑ VTE risk
↓ wound healing
↑ BP & Pulse
↑ Anxiety & disturbed sleep
What does WHO recommend for mild pain?
- regular
- paracetamol
- +/- NSAIDs
- PRN
- Tramadol
- Codeine
What does WHO recommend for moderate pain?
- regular
- paracetamol + tramadol or codeine
- +/- NSAIDs
- PRN
- Oxycodone
- Morphine
What does WHO recommend for severe pain?
- regular
- paracetamol + morphine or oxycodone
- +/- NSAIDs/tramadol
- PRN
- short acting strong opioid
- codeine
What are epidurals?
- Analgesia localised to chest, pelvis, lower limb depending on catheter site
- Can provide better pain relief than other methods
- Usually local anaesthetic +/- opiate (e.g. Levobupivacaine and Fentanyl)
What are the risks associated with epidurals?
- motor neurone block
- haematoma
- infection
- dural puncture
What is patient controlled analgesia?
- strong opioid (fentanyl, oxycodone, morphine)
- bolus dose when button pressed with 5 min lock time
What are the risk factors for PONV?
- female
- history of motion sickness
- non-smoker
What causes PON+V?
Anaesthetic agents
Opioid analgesia
Bowel surgery
Antibiotics
U&E disturbances
Bowel obstruction
Why are some patients NBM post op?
After most surgical procedures, patients can eat and drink the same day
Post major GI surgery may be NBM for several days or have impaired absorption e.g. oesophagectomy, Whipple’s
How must medicines be managed post op?
- surgical procedures take away need for certain meds
- new medicines may be needed to replace certain organ functions
- medicines may be altered by different organ function
What 3 things are required of an anaesthetic?
- abolition of sensation
- abolition of pain
- triad of GA
- unconciousness
- analgesia
- muscle relaxation
What are the 3 routes of administration of anaesthetics?
- inhalation (gases or vapours)
- IV
- intradermal
What are the 4 advantages of inhaled anaesthesia?
- controllable
- rapid
- stable
- potent
What are the 4 stages of anaesthesia?
Stage 1: analgesia
- conscious, drowsy, amnesia
Stage 2: excitement
- loss of consciousness, delirium, apnoea, gagging
Stage 3: anaesthetic
- regular respiration, loss of reflex + muscle tone
Stage 4: medullary paralysis
- depression of cardio-respiration, death
What are the 7 inhaled anaesthetics and their properties?
- chloroform (obsolete)
- desflurane (fast on and off)
- halothane (vets use, dev countries)
- isoflurane (non-epileptogenic)
- enflurane (fast, potent, hepatotoxic)
- sevaflurane (fast, potent, hepatotoxic)
- NO
What are the 6 IV anaesthetics and their properties?
- propofol (rapid metabolism, induction + maintenance)
- fospropofol (water soluble, prodrug)
- barbiturates (pre-op)
- opioids (provides analgesia + supplemental sedation)
- ketamine (slow onset, dissociative, analgesic)
- etomidate (rapid metabolism, muscle jerks)
What is the lipid theory of GA?
- potency is proportional to lipid solubility
What is the protein theory of GA?
- Luciferase inhibition correlates with anaesthetic potency
- anaesthetics interact with membrane proteins
- receptors + ligand gated ion channels
What is the MoA of GA?
- anaesthetics don’t belong to any particular drug class
- affect different types of ion channels
- block excitatory ligand-gated ion channels
- enhance activity of inhibitory ion channels
- reduce neuronal excitability through effects on K channels
What are the 5 types of local anaesthetics?
- topical
- infiltration
- nerve block
- spinal
- epidural
What are topical anaesthetics?
- applied directly to the skin or mucous membranes
- top 3, benzocaine, lidocaine + tetracaine
- used to relieve or prevent pain from minor burns, irritation or itching
- can numb before an injection
- adverse effects involve skin irritations + hypersensitivity
What are infiltration anaesthetics?
- produce loss-of-sensation restricted to a superficial, localised area
- injection of anaesthetic solution directly into area of terminal nerve endings
- used for minor surgical + dental procedures
What are nerve block anaesthetics?
- regional anaesthetics
- injection of a local anaesthetic to numb the nerves supplying a particular part of the body
What are spinal anaesthetics?
- a single injection with a thin needle that puts the local anaesthetic close the nerves
- used to numb the lower body
- rapid onset, only lasts a few hours
- side fx - low BP, headache, back pain
- provides pain relief post surgery
What is epidural anaesthesia?
- injection into space outside sac
- tube left in epidural space, anaesthetic pumped continously
- slow onset, long duration
- side fx - heart rhythm problems, seizures, hematoma in epidural space
What is the MoA of LA?
- block voltage-gated Na+ channels
- no entry of Na+ ions into cell
- no depolarisation
- no generalisation of action potential
- no generation + conduction of impulse to CNS
What are the 5 combined approaches in surgical anaesthesia?
Pre-op (sedation, anxiolysis, amnesia)
- midazolam and other benzodiazepines
Rapid unconsciousness
- i.v. of rapid short acting agent eg. thiopental
Maintain unconsciousness
- inhalation agents eg.nitrous oxide, halothane
Supplement analgesia
- i.v. agents eg.fentanyl
Paralysis
- neuromuscular block eg.suxamethonium
What are the 6 types of imaging?
Plain film (x-ray)
Ultrasound
CT
Fluoroscopy
MRI
Nuclear medicine imaging
What are the 3 types of contrast media used for scans?
Iodine based Contrast Media
Gadolinium based Contrast Media
Barium Sulphate
What are the 4 types of CVADs?
Acute Central Catheter
Hickman/Apheresis -Tunnelled
PICCs/Acute – Non Tunnelled
Implanted Ports – Chest & Arm
What are the 5 advantages of CVADs?
- Provides reliable long-term venous access
- Multiple blood sampling
- Administration of blood products, medication, PN, fluids, chemotherapy, contrast media
- Removes the need for constant venepuncture and/or peripheral cannulation
- Outpatient / ambulatory Antibiotic Therapy, chemotherapy
What are the 5 disadvantages of CVADs?
- Pneumothorax, haemothorax, air/catheter embolus, haemorrhage, haematoma, malposition, nerve damage,
- Infection risk
- Thrombosis risk – new Endexo technology now available
- Hospital / community nursing and medical staff knowledge / skill in caring for the device
- Implications related to body image and daily living – external catheters, scarring, children, physical activities, seat belt use
What are the 5 steps to care for and maintain a CVAD?
Site Inspection – signs of infection
Securement – Type of dressing
Dressing change & type - ANTT
Cleaning solution – ChloraPrep
Flushing – Positive pressure
What 4 complications can arise from a CVAD?
- Infection – systemic/local
- Thrombus
- Catheter Fracture
- Extravasation
Why must muscle reflexes be supressed during anaesthesia?
- During induction of anaesthesia reflexes mayhamper intubation
- Often important to immobilize the area underinvestigation
- Muscle spasms can occur due to mechanicalmanipulation of limbs and nerves
- Reflexes not suppressed until deep anaesthesia
How is ACh released at the NMJ?
- Action potential conducted along the motor nerve
depolarisation - Influx of calcium at nerve terminal
- ACh released from storage vesicles into the synapse
- High density of nicotinic receptors (nAChR)
- ACh metabolised by acetylcholine esterases
What is the NMJ end plate?
- ACh binding to nicotinic receptors leads to Na+ influx
- Initiates opening of voltage-gated Na+ channels
- Action potential in muscle cell membrane
What are the two types of neuromuscular-blocking agents?
Non-depolarising agents:nicotinic antagonists
Depolarising blocking agents:weak nicotinic agonists
What are non-depolarising agents?
- Competitiveantagonists of ACh receptors at the endplate
- Curare is a mixture of alkaloids found in South American plants including d-tubocurarine
- Causes paralysis by blocking neuromuscular transmission but not nerve conduction or muscle contractility
- Used by Indigenous South Americans in poison arrows
- Poor oral absorption – safe to eat
What is d-Tubocurarine
- Binds to nicotinic receptor at NMJ as an antagonist
- Much more ACh than needed is released when NMJ activated, so need to block about 90% of receptors to have any effect
- Blocking receptors causes a decrease in end-plate potential
- Synthetic derivatives now used clinically:gallamine, rocuronium,pancuronium,vecuronium
What is the effect of tubocurarine on neuromuscular transmission?
- Nerve stimulation initiates end-plate potential (epp)
- Initiates action potential
- Tubocurarine reduces the epp amplitude so that no action potential is generated
How do you recover from non-polarising NMBA?
- Rocuronium – fast onset, intermediate duration
- Determined by susceptibility to cholinesterases and clearance
- Newer non-depolarising blockers have shorter duration of action
- Safer
- Paralysis fades after surgery
What are the 6 side effects of non-depolarising blockers?
Hypotension due to ganglion blockade
M2blockade(gallamine,pancuronium) (tachycardia
Histamine release from mast cells
Bronchospasm in sensitive individuals
Respiratory failure (assisted ventilation used)
Autonomic ganglion block at high doses
What are depolarising NMBAs?
- Initially bind and activate nicotinic receptor
- Opens end-plate voltage-sensitive Na+ channels
- Depolarises muscle
- Slowly hydrolysed by cholinesterases
- Depolarisation maintained at the end-plate
- Lossof electrical excitability
- Produces initial twitching of skeletal muscleprior to block
- Decamethonium,suxamethonium(succinylcholine)
What is phase 1 block?
- Depolarising block
- Bind to nicotinic receptors
- Prolong ion conductance & depolarisation
- No repolarisation
- Potentiation by AChE inhibitor
What is phase 2 block?
- Desensitisation block
- Persistent stimulation ofnicotinic receptors leads to desensitisation
- Channel no longer open inresponse totransmitterbinding tonicotinic receptor
- Muscle becomes flaccidas Ca2+taken intostores
What are the 4 advantages of depolarising NMBA?
- Rapid onset, short duration of action
- Useful for intubation (paralyse larynx)
- Surgery during pregnancy/caesarean section
- Suxamethonium ionised so crosses blood-placenta barrier poorly and does not affect newborn respiration
What are the 6 side effects of depolarising NMBA?
- Bradycardiadue to direct muscarinic action
- Hyperkalaemia which can cause ventricular dysrhythmia
- Prolonged paralysis incholinesterasedeficient individuals
- Increased intraocular pressure
- Contraction of extra-ocular muscles
- Post-operative pain
What are the 3 differences between depolarising and non-depolarising NMBA?
Non-depolarising blockers work by competing with acetylcholine for receptors, reversed by increasign ACh concentration
Depolarising agents cause prolonged stimulation and subsequent desensitisation of the receptors, producing initial small involuntary twitches
How are NMBAs reversed?
Neostigmine
- Acetylcholinesterase inhibitor
- Raises ACh in synapse
- Reverses non-depolarising block
- Potentiates depolarising block
Sugammadex
- Chelates aminosteroid non-depolarising blockers
- reverses steroidal non-depolarizing neuromuscular blocking drugs (rocuronium and vecuronium)
What is neostigmine?
- Quaternary ammonium compound
- Competes with ACh on cholinesterase
- Lipid insoluble, does not cross blood–brain barrier
- Onset (i.v.) within 1 min, peak effect in 10 min
- Duration of action 20–30 min
- Slowly metabolised by plasma esterases
- Increases postoperative nausea and vomiting, GI disturbance
- Anti-muscarinic usually co-administered
What are general anaesthetics?
Sedative-hypnotics act by enhancing the inhibitory actions of GABAA receptors
What are the 3 ideal properties of GA?
Fast onset and recovery (titratable)
Few side effects/high therapeutic index
Aqueous solubility for easy formulation
How was propofol improved?
- it was insoluble as an o/w emulsion
- was transformed in water soluble fospropofol
What are benzodiazepines?
- Widely used as anxiolytics, amnestics and sedative-hypnotics
- Less used as anaesthetic induction agents due to cv depression and prolonged recovery times
