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37 Cards in this Set
- Front
- Back
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malignant hyperthermia
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- autosomal dominant condition
- triggered by suxamethonium and volatiles - characterised by hypermetabolic state with associated muscle rigidity and breakdown |
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malignant hyperthermia pathophysiology
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- loss of skeletal muscle cell calcium homeostasis
- deceptive ryanodine receptor - excessive Ca release results in excessive actin and myosin interaction - excessive actin-myosin interaction leads to: rhabdomyolysis increase in temperature hypoxia from increased O2 demand acidosis from lactate and CO2 production K release |
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malignant hyperthermia management
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- activate MH protocol
- call for help -remove trigger (volatile) and commence TIVA - finish surgery - ABCDE approach |
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malignant hyperthermia management
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A and B
- change circuit if able - hyperventilate C -dantrolene, initial dose 2.5mg/kg. Repeat dosing up to 10mg/kg until see tachycardia, rise in CO2 and temp improve - treat K via insulin/dextrose and Ca chloride if excessively high to protect against arrhythmias - full set of bloods incl CK - insert art line and CVC - insert IDC, aim UO 2mls/kg to limit damage from rhabdo, can give mannitol D - insert temp probe and commence active cooling with cool fluids, forced air, ice blankets |
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follow up MH
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- IVCT with halothane and caffeine
- high sensitivity - get strips of muscle (can use LA + sedation, regional, TIVA GA or spinal) - if positive, family offered genetic testing, but many different DNA mutations so poor sensitivity - if DNA test is negative immediate family members undergo IVCT |
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delayed emergence
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- pharmacological eg volatile, opioids, muscle relaxants, benzos, D2 antagonists, central anticholinergic syndrome, total spinal
- CVS: low CO state eg cardiogenic shock - Resp: hypoxia, hypercarbia - CNS: CVA (ischaemic or haemorrhagic), cerebral oedema, seizures, - Metabolic: hypothermia, hyponatraemia, hypothyroid, hypoglycaemia, uraemia - Psych: psychogenic - Muscular: MS, myaesthenia gravis, guillian-barre - pres-existing state: ETOH intoxication, drugs |
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factors affecting aspiration
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patient:
- PHx GORD, - unfasted - fatty meal - reduced gastric motility eg drugs (anticholinergics), pain, anxiety, autonomic neuropathy - obstruction to gastric motility eg tumour, - decreased conscious state - compromised airway reflexes eg bulbar dysfunction, muscular dystrophy, multiple sclerosis Anaesthetic: - difficult BMV leading to gastric insufflation - difficult intubation (increased time to secure airway) - unprotected airway eg facemask, LMA, uncuffed ETT - inadequate depth of anaesthesia - post-operative residual paralysis surgical: - trendelenburg - intra-abdominal procedures, particularly pneumoperitoneum |
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managing aspiration
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- decrease risk of further aspiration eg turn lateral head down
- 100% O2 - if patient is awake/nearly awake suction oropharynx and keep in recovery position - if unconscious and breathing spontaneously then place cricoid pressure on and perform RSI - if unconsious and apnoeic intubate - once intubated, insert NGT and decompress stomach - reduce FiO2 as much as possible to maintain SpO2 - perform bronchoscopy and lavage - steroids and antibiotics are not routine |
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TURP syndrome
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- stop surgery
- call for help - send urgent ABG and full bloods including serum osmolality - treat seizures with benzodiazepines if needed - treat bradycardia with atropine and hypotension with vasopressors and/or calcium - if in APO give frusemide - if Na <120mmol/L or symptomatic give 3% saline TBW x 0.6 x2 = mls/hr which will raise serum Na by 1mmol/hr - transfer to HDU for ongoing management |
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risk factors for TURP syndrome
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- long procedure (>than 1/24)
- big prostate - large venous plexus - height of irrigation fluid and pressure on irrigation fluid - irrigation of >1.5L - capsular perforation allowing fluid into peritoneal cavity |
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radial artery complications
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- limb ischaemia (increased risk witgh larger non teflon coated cannula, small radial artery, no heparin flush, advanced atherosclerosis, low perfusion or shock, use of vasoconstrictors)
- nerve injury - infection and sepsis - occult haemorrhage from disconnection - injection of intraarterial drugs - air embolism |
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complications of tourniquets
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- local: pressure effects on skin, muscle, nerves
- regional: ischaemia of tissues distal to tourniquet - systemic CVS: -autotransfusion with tourniquet inflation increases preload, wary in CCF - tourniquet pain with time leads to SNS activation - removal of tourniquet leads to release of ischaemic mediators leading to hypotension Resp: - increased CO2 with release of tourniquet CNS: - increase in CBF with release of tourniquet Haem: - tourniquet associated with hypercoagulable state - wary with sickle cell must have limb exsanguinated |
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tourniquet logistics
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- upper arm systolic +50-100mmHg and 2x systolic for lower limb (generally 200 and 250mmHg respectively)
- duration no longer than 2/24 - AHA says cuff should be diameter of arm +40% for width and 15cm longer than circumference |
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risk factors for peri-op nerve injury
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patient:
- smoking - extremes of weight - existing neuropathy - systemic disease eg atherosclerosis, DM, PVD, HTN surgery - CABG - long duration anaesthetic - GA >regional - positioning - IJV cannulation - hypotension - hypothermia - hypoxia - dehydration |
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positions to avoid nerve injury
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supine
- head in neutral position - arms at less than 90 degrees and excessive supination - avoid posterior displacement of arm lateral: - dependent arm anterior to thorax - axillary roll to keep pressure off brachial plexus prone: - avoid arm abduction >90 degrees brachial plexus: - at risk when arm abducted >90 degrees and supinated and head turned away |
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residual paralysis complications
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Need to block 70% of nAchR
Resp: - aspiration - hypoxia - hypercarbia - atelectasis - pneumonia CVS: - SNS stimulation (HR and BP) leading to increased O2 demand Neurological - Increased ICP from hypercarbia Other: - prolonged PACU stay, increased nursing requirement |
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NMJ testing
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clinical:
- sustained head lift >5secs (prob most accurate clinical test but may only identify TOF 0.5) - sustained grip strength - SV with TV of 5-7mls/kg - all clinical tests have low sensitivity clinical with tactile/visual assessment: - TOF 2Hz, 4 stimuli at 0.1msec - looks at number of twitches generated and TOR ratio (comparison of 4th to 1st twitch) - need TOF ratio of 0.9 to safely extubate -DBS - 2 bursts at 3 0.2msec stimuli at 50Hz seperated by 0.75sec - no more sensitive then TOF, may be easier to feel -tetanic stimulation - high freq 5 sec supramaximal stimulus - should produce sustained tetanic stimulation -post-tetanic count - stimulation 1Hz after tetanic stimulation - number of twitches is inversely proportional to block - 1st TOF returns at PTC 9 can add mechanomyography to above but muscle must be held still, not practical (gold standard) acceleromyography, use acceleration of muscle. Provides quantitative assessment piezoelectric effect - crystal produce a change when compressed |
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sugammadex
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- cyclodextran
- dose depends on degree of paralysis 16mg/kg if immediate reversal required 4mg/kg for PTC 1-2 to TOF1 2mg/kg for PTC ≥2 |
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awareness
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-post-operative recall of intraoperative events under general anaesthesia
- may be implicit or explicit - implicit is unable to recall events but has subsequent impact on behaviour - explicit is the ability to recall events - occurs 1-2/1000, but higher incidence in high risk group 1/100 - most common cause due to inadequate anaesthesia |
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BIS
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- analysis of single channel frontal spontaneous EEG
- calculates value based on bispectral analysis of 0-100 where 0 is deep anaesthesia, 100 is awake and 40-60 has a low probability of awareness - advantage is to reduce awareness but minimise depth of anaesthesia |
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risk factors for awareness
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patient
- poor cardiac reserve eg aortic stenosis, pulm HTN, low CO - poor respiratory reserve (due to poor gas exchange, ET doesnt reflect blood and brain concentration - increased anaesthetic requirement eg substance abuse (benzo, opioids, chronic ETOH), young age, red hair, pyrexia, hyperthyroid, anxiety -difficult airway surgical -likely CV instability eg cardiac, trauma -interruption to anaesthetic delivery eg bronchoscopy - obstetric (due to concern regarding reduction in uterine tone anaesthetic - human factors such as omission errors (failed to turn on volatile, TCI pump), programming errors (inappropriate settings on pump), distraction or inattention (failure to recognise low ET/BIS, signs of awareness eg tachy, HTN, sweating, tear production - equipment failure (failure of pump or disconnection) - technique (relaxants increase risk, TIVA |
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Entropy
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- analysis of EEG and FEMG
- reports static and response entropy - static entropy anaylses brain EEG only, reflects hypnotics activity on brain, 0-90 - response entropy uses higher frequency, looks at both EEG and frontalis activity, scored 0-100 with faster response time. May activate during surgery to indicate pain or movement of muscles |
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B-aware
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-lancet 2004
-multicentre RCT - inclusion was adults at high risk of awareness undergoing relaxant GA - comparison of routine care vs BIS (aim 40-60) - found a RR reduction of 80% in BIS group and NNT of ~140 |
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B-unaware
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-NEJM 2008
- single centre prospective RCT - comparison of ET volatile vs BIS guided - found no difference between awareness, maybe more implicit awareness in BIS guided group - underpowered study and included patients at low risk cf B aware trial |
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BAG-RECALL
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- NEJM 2011
- follow up multicentre RCT to B unaware - compared BIS guided to ET guided anaesthesia - increased awareness in BIS group but not statistically significant |
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pericardial tamponade from CVC insertion
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- results in fluid accumulation in the pericardial sac which obstructs venous return and impairs cardiac filling leading to reduced CO
-signs CVS: tachycardia, kussmauls sign, muffled heart sounds, pulsus paradoxus, hypotension, syncope and presyncope, R heart failure ECG: low voltage CXR enlarged cardiac silhouette |
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TTE signs of pericardial tamponade
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- fluid in pericardial space
- chambers collapse - deviated septum to L with inspiration - abnormal venous flow - exaggeration in cardiac and venous flow with respiration |
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Ideal CVC position
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- patient specific
- ideal to have CVC outside pericardial reflection, ideally 2-3cm above the atrio-caval junction |
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CVC complications
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- damage to surrounding nerves
-arterial puncture -PTx - air embolism - needlestick injury - discomfort on insertion - arrhythmias - PA rupture if PAC - pericardial tamponade - anaphylaxis from prep or antibiotic coating - thrombosis - infection |
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beachchair position
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CVS:
- poor venous return - hypoperfusion to tissues above the heart - VAE - risk of DVT - poor access to IVs Resp: - poor access to airway CNS: - possibility of obstructed venous return from flexed neck - cerebral ischaemia PNS: - nerve injury, keep knees slightly flexed |
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prone position risks and how addressed
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CVS
- reduced VR = keep legs in plane with torso, use of calf compression stockings and TEDs - arrests and CPR = bed available to transfer supine if arrests and surgically appropriate Resp: - decreased FRC due to limited abdominal excursion = use of wilson frame to allow abdominal contents to move freely with respiration - difficult airway access = reinforced ETT secured carefully CNS: - external ocular pressure increasing risk of ION or CRAO = use of head foam and eyes free and checked regularly - increased ICP from occluded venous return = neck in neutral position - increased epidural venous pressure due to transmitted pressure from abdomen PNS: - brachial plexus and ulnar nerve damage = ensure free from pressure and arms not abducted more than 90 degrees Musculoskeletal - pressure areas = check dependent areas are padded appropriately |
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PONV incidence
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- occurs in ~20-30% general surgical population and 70-80% of high risk group (4 risk factors)
1 risk factor = 20% 2 RF = 40% 3 RF = 60% 4 RF = 80% |
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PONV risk factors
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major
1/ female 2/ non-smoker 3/ PHx PONV or motion sickness 4/ post-op opioid use Minor anaesthetic - use of volatiles - use of N20 - duration - use of neostigmine surgical - inner ear surgery - blood into stomach (emetogenic) - gynae |
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IMPACT trial
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- dexamethasone 4mg, ondansetron 4mg and droperidol all had absolute risk reduction of ~20% (NNT of 5) or RR of 26%
- propofol TIVA had RR of 19% avoidance of N2O RR reduction of 12% |
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steroids
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- hydrocotisone 100 = dexamethasone 4mg = prednisolone 25mg = methylprednisolone 20mg
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steroid replacement
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- if <10mg then dont need replacement
- if >10mg and minor surgery then 25mg hydrocortisone on induction - if >10mg and moderate surgery then usual pre-op steroid and 25mg hydrocort on induction and 100mg/day for 24/24 - if >10mg and major surgery then usual pre-op, 25mg hydrocort on induction and 100mg/day for 48-72/24 - if stopped within 3/12, treat as if still on - if stopped >3/12 no peri-op steroids needed - if 5/7 days of pred >10mg within 3/12 period, treat as >10mg above |
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perioperative CVA
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- majority occur 2/7 postop
patient: - CVA (if within 6/52 risk is 20x increased) - co-morbidities eg HTN, atherosclerosis, DM, smoking, renal impairment, PVD, IHD, CCF, AF - carotid stenosis - abrupt discontinuation of anti-thrombotic therapy - inflammation or infection anaesthetic factors - uncorrected hypotension/hypovolumia - beachchair position - duration of surgery - emergency surgery - arrhythmias surgical - carotid or aortic arch surgery - CABG |
