Interventions/Procedures Flashcards

Question

Elective Craniotomy

Answer 1

Pre-operative * pathophysiology of underlying condition — symptoms of raised ICP, consider hydration status — symptoms of SOL - headache, poor balance, seizures, CN defects, on dex/PPI? — pituitary function - ACTH, Cushings, DI, SIADH, GH + acromegaly, hypo/hyperglycaemia — implications on renal function/electrolytes — posterior cranial fossa symptoms - e.g. cough/gag — neurological examination including ask regarding changes in vision/hearing * other health issues * consent for positioning complications, haemorrhage + transfusion, cardiovascular instability, post-op HDU/ITU * discuss positioning with surgeon Intra-operative * maintain adequate CPP (MAP) * avoid rise in ICP (maintain ETCO2 4.5) * full monitoring + temp, invasive BP, UO, depth of anaesthesia, PNS * 1-2 large bore peripheral IV access +/- CVC (consider position) - long extensions, foot cannulas * positioning - supine/prone/lateral/park bench * armoured ETT - secure with tapes * thio/prop + remi (gentle induction) + NMBA (monitor TOF)- may need sugammadex if using MEPs * maintenance - TIVA or volatile/remi * dexamethasone + anti-emetics * deep extubation - avoid coughing * multimodal analgesia - start giving morphine once starting to close/after extubation Post-operative * manage pain and vomiting * monitor GCS, signs of raised ICP, massive haemorrhage * pneumatic boots * avoid NSAIDs * watch for hyperglycaemia and other metabolic derangements

Answer 2

Pre-operative * usually young with few co-morbidities - hyperhidrosis, blushing, long QT, CRPS, angina * cardiovascular evaluation if for angina/long QT * G&S, warn about possibility of open procedure Intra-operative * routine standard monitoring +/- art line * GA usually (thoracic epidural/intercostal block) * standard ETT +/- BB/DLT/Proseal LMA with controlled ventilation (CO2 insufflation) * usually bilateral procedure (10-15 min per side) * intrathoracic LA under direct vision by surgeons * paracetamol + NSAID * big drip due to risk of catastrophic bleeding Post-operative * simple analgesia + opioids PRN * CXR in recovery * often day case if straightforward

Answer 3

Pre-operative * optimise glycaemic control/BP * smoking cessation + ETOH advice * weight loss * measure albumin + correct nutritional deficiency * patient education and counselling * pre-habilitation * optimise PMH and risk stratification * assessment and correction of anaemia * pre-op carb loading + “sip til send” * avoid bowel prep + sedating pre-med Intra-operative * minimally invasive * avoid NGT/drains * short acting agents, regional * temp control * PONV prevention * VTE prophylaxis * restrictive fluid Post-operative * early PO intake and IV discontinuation * multimodal analgesia + adjuncts * drains out early * early mobilisation * criteria based discharge

Answer 4

Daily nutritional requirements in critical care: *Water 30ml/kg, Energy 25cal/kg, Protein 0.8-1.5g/kg, Fat 1g/kg, Carbohydrates 2g/kg, Nitrogen 0.2g/kg, Na 1-2mmol/kg, K 0.8-1.2mmol/kg, Cl 1-2mmol/kg, PO4 0.5mmol/kg, Ca 0.1mmol/kg, Mg 0.1mmol/kg* When to start enteral nutrition on ITU? * as soon as feasible * ideally once fully resuscitated and off vasopressors * within 48hrs with cautious monitoring How? * no evidence that post-pyloric feeding is superior to NG * post-pyloric feeding is more complex and requires input from radiology or GI teams * early parenteral nutrition has not been found to affect outcomes * exhaust all EN strategies before considering PN (suggests after 3-7 days if not tolerating EN) Benefits of EN * Reduce stress related catabolism * Minimise bacterial translocation * Maintain intestinal mucosal integrity * Stimulates intestinal blood flow * Prevent or reverse malnutrition * Cheaper and simpler with fewer complications than PN * Improves healing, weaning and recovery Risks of EN * Aspiration (decreased with post-pyloric feeding) * Sinusitis * GI complications - perforation of organs, intolerance * Bowel ischaemia * Tube malpositioning/dislodgement * Metabolic complications e.g. refeeding syndrome, hyperglycaemia Benefits of PN * Can be started early * Does not rely on gastric/intestinal function * Less need for interruptions Risks of PN * CVC associated infection * Metabolic complications - hyperglycaemia, electrolyte abnormalities, Wernicke's, nutrient excess or deficiency, liver dysfunction, refeeding syndrome

Answer 5

Topical LA for eyes * Gel - 2% lidocaine gel applies topically to the cornea * Intracameral LA - <0.5ml 1% preservative free lidocaine instilled into the anterior chamber of the eye * Eye drops - fast onset 15-20s, 20 minute duration -- amethocaine 0.5% or 1% - stinging on application, relatively high degree of corneal toxicity, better analgesia -- oxybuprocaine 0.4% - less toxic than amethocaine -- proxymetacaine 0.5% - doesn't sting, lowest toxicity, preferred for kids * Regional blocks -- Sub-Tenon's -- Retrobulbar -- Peribulbar Sub-Tenon's Block * Tenon's capsule - connective tissue layer that encapsulates the sclera, fused posteriorly with the dural layer of the optic nerve head, attached to the bulbar conjunctiva anteriorly * Gives almost instantaneous sensory blockade then spreads posteriorly along the contour of the globe, through the capsule opening into the intraconal space leading to motor block * IV access + monitoring * LA drops + clean * Inferomedial quadrant with patient looking up and out * Non toothed forceps to lift conjunctiva, blunt ended scissors to dissect * Blunt, curved cannula following the curvature of the globe to the equator * 3-5ml of LA injected slowly -- 2% lidocaine (lasts ~40 mins) -- 0.75% levobupivicaine (slower onset, longer duration) -- hyaluronidase improves speed of onset and quality of block (7.5-15IU/ml) by hydrolysing bonds between glucosamine and glucuronic acid in hyaluronic acid, breaking down the extracellular matrix * Gentle pressure to eyelid * Advantages - wide range of procedures, lower risk of life/sight threatening complications, safe in anticoagulated or antiplatelet agents, can be topped up, doesn't increase IOP * Disadvantages - chemosis + subconjunctival haemorrhage can affect some procedures, risk of difficulties if scarring from previous procedures, potential damage to optic nerve or short posterior ciliary arteries if too posterior, eye may still be mobile if small volume LA used Retrobulbar block * Sharp needle technique * Injecting directly into the intraconal space - acts directly on sensory and motor nerves * IV access + monitoring * LA drops + clean * Gaze straight ahead, 31mm 23G needle inserted transconjunctivally just lateral to limbus * Directed posteriorly until tip just past the equator, then redirect upwards and medial towards the apex * 1-3ml injected slowly * Advantages - small volume injection, rapid onset of anaesthesia and akinesia * Disadvantages - tip of sharp needle close to optic nerve, dural sheath and ophthalmic artery, orbicularis oculi may not be paralysed Peribulbar block * Sharp needle technique * Injecting into extraconal space - spreads into intraconal space leading to action on sensory and motor nerves as well as lid akinesia * 2x injections - 1x medial, 1x inferolateral * IV access + monitoring * LA drops + clean * Gaze straight ahead, 25mm 25G needle medial to caruncle, directed back and medial then redirected posteriorly * 3-5ml slow injection * Gaze straight ahead, injection through conjunctiva just lateral to limbus, down towards bone, then redirected posteriorly and medially * 4-6ml slow injection * Advantages - suitable for a wide range of procedures, excellent akinesia or globa and lids * Disadvantages - sharp needle technique, increased risk of globe performation if longer axial length, difficult/hazardous if scleral buckle present Complications * Life-threatening - brainstem anaesthesia, anaphylaxis, intravascular injection of LA, LAST, CNS toxicity * Sight-threatening - globe perforation/penetration, prolonged dysfunction of extraocular muscles, orbital haemorrhage, optic nerve damage * Minor - pain, chemosis, proptosis, subconjunctival haemorrhage

Answer 6

Aim - to reduce risk of injury to neural structures during surgery. Usually carried out by dedicated neurophysiologists. Cause of Injury * direct mechanical disruption from surgical manoeuvres * thermal injury from surgical coagulation * pressure injury from patient positioning * ischaemia due to local or global hypoperfusion Types of Surgery * Vascular surgery involving carotids - SSEPs, MEPs * Resection of intracranial tumours/AVMs - SSEPs, MEPs * Posterior fossa/brainstem surgery - BAEPs * Surgery with risk of direct injury to spinal cord/roots or risk of compromising their blood supply e.g. scoliosis, thoracoabdominal aneurysm repair - SSEPs, MEPs, EMG * Surgery close to cranial nerves or peripheral nerves e.g. facial nerve in parotid preocedures, RLN in thyroid surgery - EMG Options * detection of spontaneous activity e.g. EEG, EMG * measurement of evoked electrical response of a specific neural pathway after an active stimulation e.g. SSEP, MEP, BAEP * wake up test EMG - electromyography * electrodes used to initiate an action potential in a peripheral nerve * action potential arrives at the NMJ, depolarises nerve terminal releasing ACh * ACh binds to the alpha subunit on the post junction all receptors, allowing influx of sodium * depolarisation of the end plate, activating further sodium channels allowing depolarisation away from the end-plates to both ends of muscle fibre at 3-5m/sec (7-7ms to spread through 5cm muscle) * muscle action potential via T-tubule system depolarises the membrane, releasing calcium, leading to excitation-contraction coupling * EMG is the sum of the action potentials of the adjacent fibres in a muscle * one electrode over the mid part of the muscle and the other at the end of the muscle * action potential is recorded as it travels down the muscle * repetitive stimulation gives normal response if there is no defect in neuromuscular transmission BAEPs - Brainstem Auditoy Evoked Potential * acoustic stimulus delivered at the ear canal * electrical signals, generated by the cochlear, travel along the vestibulocochlear nerve into the nucleus and brainstem * response recorded by an electrode at the mastoid or ear lobe SSEPs - Somatosensory Evoked Potential * monitors ascending sensory pathways through transcutaneous electrical stimulation of a peripheral nerve * ascends cord via dorsal columns * decussates at medulla, asends to thalamus and sensory cortex * median or ulnar nerve stimulation * posterior tibial nerve stimulation MEPs- Motor Evoked Potential * monitors integrity of descending corticospinal and corticobulbar tracts * stimulation at motor cortex * electrical activity descends along the motor tracts, travelling along the nerve, across the NMJ to produce muscle contraction * can be transcranial through the scalp or direct electrical stimulation on the brain * measures compound muscle actions potentionals - composite electrical activities within the effector muscles e.g. thenar muscles, tibialis anterior, abductor hallucis Anaesthetic considerations with IOM * anaesthetic agents produce dose-dependent suppression of evoked potentials - TIVA technique optimal, short acting NMBAs or reverse * need to provide stable physiology to facilitate meaningful interpretation of signal changes and accurate surgical guidance - maintain MAP, avoid hyperventilation, avoid hypothermia, avoid anaemia and hypoxaemia, maintain normoglycaemia * potential for nonsurgical causes of neural injury - need to act promptly to manage and prevent secondary injurys * risks of IOM e.g. bite injury, patient movement during stimulation, use of sharps

Answer 7

Fetal conditions amenable to fetal interventions * twin reversed arterial perfusion * twin-twin transfusion syndrome * catheter-based balloon aortic valvuloplasty or septoplasty for cardiac anomalies * CDG - fetal endoscopic tracheal occlusion * myelomeningocele - open or fetoscopic repair * sacrococcygeal teratoma - open resection * fetal cystoscopy/vesicoamniotic shunt for urinary tract obstruction * EXIT open airway management * intrauterine transfusion of RBCs Classes of intervension * Minimally invasive and fetoscopic - maternal laparotomy or percutaneous insertion of trocars into uterus, uterus remains intact, instrucments inserted into closed uterus under direct vision * Open fetal surgery - maternal laparotomy and hysterotomy with aim to close hysterotomy at the end of the case * Open fetal surgery with delivery at the end - maternal laparotomy and hysterotomy Risks of open fetal surgery * preterm birth * chorion-amnion separation * spontaneous membrane rupture * oligohydramnios * placental abruption * maternal pulmonary oedema * increased incidence of uterine thinning/dehiscence of the uterine scar at deliveru - will need C-sections Pre-operative * comprehensive history * physical examination * cross match * fetal studies - USS, MRI, echo, genetic testing * psychosoial evaluation and extensive counselling Intra-operative * from LA +/- sedation to deep GA depending on case * minimise risk of pulmonary aspiration - prophylaxis, position * left uterine displacement * low thoracic epidural + GA for open fetal surgery * RSI * invasive BP monitoring for optimal uterine perfusion pressure - phenylephrine infusion * restricted crystalloid due to risk of pulmonary oedema * high MAC (1.5-2) * magnesium sulphate bolus and infusion to prevent preterm labour

Answer 8

Pre-operative * full anaesthetic assessment - especially cardio, respiratory, nutrition * airway strategy (if head and neck) - MDT approach * investigation - FBC, U+Es, coag, G+S (LFTs, glucose) Intra-operative * hyper dynamic circulation - increased CO, decreased SVR, Hct 30% * invasive monitoring + catheter * minimise stress response (remi) * avoid barotrauma/atelectasis * controlled hypotension during dissection * increased MAP once anastomosing * caution with fluid (flap oedema) * ?NGT * smooth emergence (avoid surge in BP/flow to flap) Post-operative * HDU/flap monitoring * normothermia, normotension, Hct 30% * sats >94% (LRTI prevention - physio, mobilise) * analgesia * LMWH * avoid additional stress e.g. withdrawal

Answer 9

Pre-operative * paeds * often multiple previous procedures Intra-operative * adrenaline drops * ketamine GAs for kids * laser therapy * LA (? Lower volume) or GA acceptable Post-operative * most done as day case

Answer 10

Passive * cold water bath - sterile water reservoir through which gas is bubbled at room temperature (< 50% relative humidity unless either very low gas flow or large water surface area) * soda lime - energy produced by reactions of Ca(OH)2 and NaOH with CO2 * HMEF - conserves patients own heat and water without the need for an external power or water source, compact cheap and effective though efficiency reduces over time (60-70% relative humidity) Active * hot water bath - sterile water reservoir that is electrically heated through which gas is bubbled, risks of scalding and infection (100% relative humidity) * nebulisers - supplies water in droplet form, greatest relative humidity but risk of water intoxication (>100% relative humidity)

Answer 11

Controlled, induced or deliberate hypotension * 30% reduction in baseline MAP * effective at reducing blood loss * improves quality of the surgical field * extreme caution if impaired autoregulation or high risk of organ dysfunction * limit duration and extent even in fit and well individuals Elements * head up/elevation of surgical site for positioning * reduce SVR - calcium channel blockers, inhalational anaesthetic agents * reduce contractility - inhalational agents, beta blockers * reduce SV - beta blockers, remifentanil * selective alpha-2 adrenergic agonists * TIVA * use of histamine releasing agents - morphine, atracurium

Answer 12

CSF drainage for hydrocephalus Pre-operative * as for craniotomy * often paediatric patients * often have raised ICP * consider RSI if emergent Intra-operative * routine monitoring * art line/CVC not usually required * antibiotics + strict antisepsis * advancing trocar to allow tunnelling of shunt is particularly stimulating —> additional analgesia +/- relaxation Post-operative * monitor GCS * risk of intracranial haemorrhage if CSF drained too fast * risk of shunt blocking/infection * watch for pneumothorax

Answer 13

Physics * Lasing medium * Energy source - energizes particles in the gain medium - when the temporary excited state decays, a photon is emitted of a specific wavelength * Optical resonator - a cavity containing the lasing medium with 2 parallel mirrors on either side - one highly reflective, the other partially reflective allowing the ouput beam Safety * Burns - retina, optic nerve, skin * Fire - use air + low FiO2, avoid N2O, non flammable ETT, non reflective instruments and equipment, wet swabs, non combustible drapes * Theatre - laser operator, fire extinguisher, eye protection, doors locked with warning signs, windows covered Types * solid state eg. Ruby for hair removal and tattoo removal, Holmium:YAG for lithotripsy, Nd:YAG for cutting and coagulating * gas e.g. CO2 (far IR) for cutting, coagulating, resurfacing; argon for retinal surgery and AV malformations * dye e.g. pulsed yellow dye for birthmark removal or vascular skin lesions * semiconductor diode (red/IR) e.g laser pointer, hair removal, bar code scanners Intra-operative * designated laser safety officer * matt surfaces * locked doors and signs * eye protection * cover exposed skin * wet swabs to adjacent tissues * avoid flammable skin prep * LASER specific ETT - metallic tube with double cuff filled with saline/methylene blue (high volume, low pressure cuff) * avoid nitrous oxide * low flow, low FiO2

Answer 14

Pre-operative * As far any major abdominal surgery * Screening of liver function and coagulation Intra-operative * Large bore IV access +/- art line +/- CVC * Thoracic epidural * GA + ETT + IPPV * Aim for relatively hypotensive + low CVP to minimise blood loss * Minimise fluid input prior to resection * Active warming * POC coagulation if needed * Pringle manoeuvre for control of bleeding * Fluid load following resection Post-operative * HDU/PACU * Risk of coagulopathy and encephalopathy * Use short acting drugs * Avoid drugs that rely on hepatic metabolism or may cause encephalopathy * Consideration re: timing & removal of epidural if coagulopathy (may need FFP cover)

Answer 15

Pre-op Lung Function Tests * FEV1 >2L for pneumonectomy and >1.5L for lobectomy * ppoFEV1 and ppoDLCO >40% + oxygen says >90% = average risk * if either/both ppoFEV1 and ppoDLCO <40% --> CPET Exercise Tests * shuttle walk (25x10) - high risk if not completed * 6mwt - high risk if <70% of predicted distance achieved or <250m * stair climbing test - high risk if <22m * CPET — relatively good function if VO2 max >15ml/kg/min (BTS 2010) — high risk if VO2 max <10ml/kg/min or <35% of predicted (ACCP 2013) — moderate risk if 10-20ml/kg/min or 35-75% predicted — low risk if >20ml/kg/min or >75%

Answer 16

* Rotameters - variable orifice, constant pressure - needle valve controls the flow of gas through the flow meter and a tube which grdually increases in diameter with an internal bobbin, as the gas flow increases, the bubbin rises (calibrated for gas density) * Pheumotachograph - constant orifice - small wide tube with a mesh in it to reduce the volocity of the flow of gas, pressure drop is measured by a differential pressure transducer across the resistance - as the flow increases, the pressure drop across the resistance increases * Inferential flowmeter - Wright’s respirometer - set of very low resistance vanes, flow of gas causing them to spin - amount of spinning proprtional to flow rate * Wright Peak Flow Meter - variable orifice, as the internal diaphragm moves with the air blown it, it opens a larger orifice for air to escape * Hot wire anemometer - measures heat loss of an electrically heated wire placed in the air stream * Ultrasonic flowmeter - use sound waves to determine the velocity of a fluid flowing in a pipe

Answer 17

* Wet and dry bulb hygrometer - one bulb open to air, one wrapped in a wet rag - at 100% humidity, the wet and dry temperatures should be identical. As humidity decreases, evaporation occurs from the wet bulb, decreasing the temperature on the thermometer due to latent heat of evaporation * Regnault’s dew point - air blown through a silver tube containing ether - at dew point, condensation occurs on the outer surface of the tube * Hair hygrometer - increasing humidity increases length of hair * Mass of hygroscopic crystals - absorb moisture and weight vs dry weight can be used to measure humidity * Electrical methods — resistance sensors - measure the resistance change in a moisture absorbing material - impedence change usually has an inverse exponential relationship to humidity — capacitance sensors - hygroscopic dielectric material placed between a pair of electrodes that forms a small capacitor - capacitance increases with higher humidity * Mass spectrometry - principle of reduction in the UV light transmitted through the medium containing water vapour

Answer 18

Non Invasive - clinical signs - core-peripheral temperature - ballistography, bioimpedance - suprasternal Doppler - NICO - indirect Fick partial rebreathing Minimally invasive - oesophageal Doppler - pulse contour analysis (PICCO) Invasive (PAFC) - dye dilution - thermodilution - continuous CO, SVO2

Answer 19

Used for “SEMI-CRITICAL” items that touch mucous membranes or skin that is not intact - thermal washer disinfector - initial clean at <35 then 71 for 3 mins or 80 for 1 min or 90 for 1 sec - pasteurisation (low temp steam) - more than 70 for 30 minutes - boiling water for 5 minutes - chemical - 70% ETOH, iodine, glutaraldehyde, chlorine, hydrogen peroxide etc

Answer 20

* visual, tactile - ability to sustain head lift for 5s * electromyography - recording of a compound action potential that occurs during muscular contraction * mechanomyography - measurement of evoked muscle tension using a strain gauge transducer and recorder (arm and hand must be fixed with movement of the thumb along the length of the transducer for accuracy) * acceleromyography - measures acceleration of the contracting muscle to calculate force (f=ma), acceleration being measured by a piezoelectric ceramic wafer strapped to the thumb, producing a voltage proportional to its acceleration Qualitative: * Single twitch 70-80mA, 0.1ms * Train of four 70-80mA, 0.1ms at 4Hz - 4 equal twitches seen from about 70% receptor occupancy * Double burst stimulation - 2 sets of 3 twitches (70-80mA, 0.2ms, 50Hz separated by 750ms) * Post tetanic count 70-80mA, 0.1ms twitches at 1Hz after a tetanic stimulus of 50Hz for 5s - number of twitches present is inversely related to the length of time until recovery from block (9 = return of first twitch in TOF)

Answer 21

**Electrochemical** * polarographic (Clarke) electrode -- oxygen molecules diffuse across a teflon membrane -- current flows between a silver cathode and a platinum anode -- current is proportional to the partial pressure of oxygen in the inspiratory gas -- battery powered -- life expectancy ~3yrs due to deterioration of the teflon membrane * galvanic fuel cell -- on the inspiratory limb of the breathing system -- oxygen molecules diffuse across a membrane and an electrolyte solution to a gold (or silver) cathode, which is connected through the electrolyte solution to a lead anode -- electrical current generated which is proportional to the partial pressure of oxygen in the inspired gas -- response time of approx 20s, accurate to within 3% -- depleted by continuous exposure to oxygen, life span ~1yr **Physical** * paramagnetic -- presence of 2 electrons in unpaired orbits means it is weakly attracted into a magnetic field -- sample gas delivered to anaylser via sampling tube -- two chamber analyser separated by sensitive pressure transducer -- sample gas to one chamber, room air to reference chamber -- electromagnet rapidly switched on and off causing o2 molecules to be attracted and agitated -- results in changes in pressure on either side of the pressure transducer -- pressure difference is proportional to the oxygen partial pressure difference between the sample gas and the reference gas -- very accurate and highly sensitive -- affected by water vapour, have a water trap incorporated * mass spectrometry -- sample gas drawn or injected into a low-pressure sample chamber that is attached to another chamber, at a pressure nearing that of a vacuum -- molecular leak pathway constructed between the chambers -- molecules ionised in second chamber and accelerated by a cathode plate -- fixed magnets or electro,agnets influence the ions and allow separation by the ion's mass and charge -- ions are narrow-band filtered and detected by photo-voltatic receptors -- signal amplified and processes -- require powerful vacuum pumps and cannot return sample to patient -- response and delay times -- very accurate

Answer 22

Used for “critical” items that enter normally sterile tissue or the vascular system - steam - 121 for 30 mins or 132 for 4 mins - ethylene oxide - hydrogen peroxide (28-52 mins) - ozone - dry hot air - 160 for 2hr - ionising radiation e.g. cobalt-60, gamma

Answer 23

* Based on absorption of light shone through a sample * Absorption of deoxy-Hb and oxy-Hb is the same at 805nm - isobestic point * Deoxy-Hb has a high absorption at 660nm (red) and low at 940nm (IR) * Oxy-Hb has a high absorption at 940nm and low at 660nm * Absorbance of light through different substances - bones/flesh/tissue/venous blood are all static features and can be filtered out * Arterial blood is pulsatile so varying absorption * 2x LEDS shone from one side - 1 at 660nm, 1 at 940mm, flashing alternately * Photocell/detector on the other side of the finger then sees how much light is absorbed --> microprocessor calculate relative concentrations of Oxy and deoxy-Hb and hence, convert to oxygen saturations to display on a monitor * Most modern devices also include "off" within the cycle to compensate for stray ambient room light Errors * Pulsatiles venous blood flow e.g. AV fistulas, heart failure, placement of probe substantially lower than heart - will cause a lower reading due to pulsatile deoxygenated blood * Presence of carboxyhaemoglobin will cause over-estimation of saturations (CO-Hb has similar absorption spectra to Oxy-Hb) * Presence of light leaks * Presence of high bilirubin levels * Presence of intravascular dyes (methylene blue, indocyanine green) - cause artifactually lower readings * Surgical diathermy * Poor peripheral perfusion * Body movements * Inaccurate below 70%, completely unreliable below 50%

Answer 24

Physics * Patient placed in a strong magnetic field * Atoms with odd numbers of protons have an asymmetrical spin which allows them to align in the presence of an external magnetic field * Application of pulses of radio frequency energy causes protons to “flip” between energy levels * When the pulse is switched off, the protons “flip” back and release energy which can be detected * Energy detected can be processed and converted to visual images dependent on differences in the hydrogen nuclei density between tissues * Physical and chemical differences in the tissues produces 2 distinct relaxation patterns with time constants T1 and T2 * T1 - fat is bright and water dark. Good for grey-white matter contrast. * T2 - water is bright, fat is dark. Good for tissue oedema. * Addition of gadolinium contrast alters the relaxation rates of hydrogen nuclei Practicalities * MRI safety checks for patient and staff * MRI safe equipment incl. non ferrous trolley, MR compatible ventilator/anaesthetic machine or long tubing, long extensions to infusions or MR safe infusion pumps, MR safe monitoring leads (high impedance, braided, short ECG leads), fibreoptic probe connections for oximetry secure pilot balloon away from site of scan if ferromagnetic material —> monitoring transmitted to control room * Long tubing - risk of disconnections or delays in response * Risk of magnetic field heating tissues, avoid closed loops, coiled wires, any metal in clothing * Noise level - earplugs for patient * Remote site anaesthesia * Difficulty observing and monitoring patient while in scanner * Superconducting magnet needs to be kept cool - if there is sudden shutdown or spontaneous leak, helium will vapourise

Answer 25

* Optimise venous drainage from head - tapes not ties, 30 degree head up positioning, maintain TV 6-8ml predicted body weight, keep driving pressure <15 * Avoid increased ICP - control seizures, adequate analgesia, sedation * Optimise oxygen delivery to brain - PaO2 >11, maintain CPP (MAP >80mmHg), Hb >7g/dL * Maintain physiological normality - normothermia, normovolaemia, normoglycaemia, normonatraemia

Answer 26

Pre-operative * range of surgeries - lid, orbital decompression, nasolacrimal duct problems, eviscerations etc * may need to check TFTs Intra-operative * Rubens pillow * drops both eyes (for prep) * lots of cases have sedation for location * GA * throat pack/relative hypotension for dacrocystorhinostomy (? Art line) Post-operative * may be painful

Answer 27

Measurement based on the Doppler Principle: a doppler shift in frequency occurs when the ultrasound wave is reflected back from moving RBCs - the shift in frequency is proportional to the velocity of the blood flow * Small ultrasound transducer mounted on the top of a flexible probe * Inserted orally or nasally into the oesophagus * Lubricate with aqueous gel to prevent signal disturbance * Tip to lie around T5/6 (35-40cm oral length, 40-45cm nasal length) * Rotate bevel so it faces posteriorly * Tip adjusted to lie alongside descending thoracid aorta with beam at 45 degree angle to blood flow * Manipulate probe to achieve best signal Measures * Contractility - PV - peak blood velocity - peak of curve. Mormal range is age related * Preload - the "flow time" corrected for HR (low flow time corresponding to hypovolaemia or increased afterload) - width of the base of the curve * Stroke volume - the "stroke distance" is the area under the curve Numbers * CO - calculated from SV x HR * CI - CO corrected for BSA (based on input data on height/weight) * SV - stroke distance multipled by aortic diameter (usually averaged over several beats, based on nomograms from patient height and weight data correlated to aortic dimensions from CT) * SVI - stroke volume normalised for BSA * FTc - flow time is the duration of forward flow of blood in the aorta, corrected to heart rate of 60. Normal = 330-360m/s * MA - maximum acceleration - index of contractility (peak acceleration of blood flow in the aorta) * PV - peak velocity. Normal = 90-120cm/s at 20yrs, 70-100cm/s at 45yrs, 50-80cm/s at 70yrs Response * low SV or FTC --> give fluid * low PV --> give inotrope * low PV + low FTc --> decrease afterload Advantages * Minimally invasive * Provides real time measurements Disadvantages * May be inaccurate even if probe positioned appropriately e.g. coarctation, aneurysm, neuraxial anaesthetic (lower limb vasodilatation) * Cannot be used in patients with IABP * Should not be used in patients with known pharyngo-oesophageal pathology or injury * Learning curve - significant inter and intraobserver variability * Probe displacement requiring repositioning * Difficult to use in awake patient * Complications related to insertion of probe

Answer 28

Absolute Indications * prevent damage or contamination of health lung e.g. abscess * control distribution of ventilation e.g. bronchopleural fistula * facilitate single lung lavage e.g. in CF Relative Indications * to improve surgical access * *lung surgery, minimally invasive cardiac surgery, thoracic aneurysms, VATS, oesophagectomy, diaphragmatic surgery, scoliosis surgery* Indications for right sided DLT * surgery involving the left main bronchus - left pneumonectomy, left lung transplant left tracheobronchial disruption, left sided thoracoscopic surgery * distorted anatomy of left main bronchus - aneurysm of descending thoracic aorta, tumour compression of left main bronchus Lung isolation techniques * Double lumen tube - right or left?, 35/37/39/41Fr -- 39 for average male, 37 for average female (1 size up or down for larger and smaller patients) -- risk of malposition, airway trauma, tension PTX -- may be difficult to place in abnormal/distorted airways -- not ideal for postoperative ventilation -- allows suction and bronchoscopy of isolated lung -- can provided CPAP to operated lung, can alternate OLV to either lung -- can insert even if FOB not available * Bronchial blockers - coaxial or independent -- require use of FOB to confirm position and more time consuming for insertion and accurate positioning -- easier placement in difficult airways -- can allow selective lobar lung isolation and possibility for postoperative dual lung ventilation -- slow and incomplete collapse, suction not possible, bronchoscopy of isolated lung impossible, difficult to alternate OLV * Single lumen tube advanced into right or left main-stem bronchus -- easier placement in emergencies and difficult airways -- bronchoscopy, suction and CPAP impossible to isolated lung Confirmation fo DLT Placement * Sequential clamping and auscultation * Step 1 - inflate tracheal cuff to seal leak - PPV and auscultate to confirm bilateral air entry, obtain ETCO2 trace * Step 2 - clamp tracheal limb and disconnect, inflate bronchial cuff and ventilate, auscultate to confirm unilateral ventilation and no audible air leak * Step 3 - release tracheal lumen clamp and close port, auscultate to confirm resumption of bilateral air entry * Can also use fibreoptic bronchoscope, especially for right sided DLT (to ensure sustained RUL ventilation)

Answer 29

Pre-operative * most are young and fit * occasionally OSA or syndromic * airway plan - nasal tube with nasal prep Intra-operative * nasal tube with careful fixation + throat pack * minimise bleeding - induced hypotension, head-up, ETCO2 low-normal, normothermia * remifentanil, paracetamol + morphine * surgical nerve blocks * steroids * haemostasis challenge * suction under direct vision * deep/SGA exchange/awake extubation - avoid pressure to jaw/face Post-operative * airway risk +/- nasal bleeding —> soft tissue oedema/haematoma * PONV risk due to swallowing blood * multimodal analgesia * ?intermaxillary fixation

Answer 30

**Park bench position** - modified lateral position. Head flexed until the chin is almost at sternum, rotated contra-laterally to the lesion, and flexed 30 degrees laterally torward the contralateral shoulder (increases the angle between the atlas and foramen magnum). Risks * VQ mismatch (atelectasis of dependent lung) * Brachial plexus injury * Ear and eye injury * Suprascapular nerve injury of the dependent shoulder * Stretch injuries (axillary trauma) and decreased perfusion to the dependent arm **Sitting position aka Beach Chair position** - improves surgical access to the posterior fossa by facilitating gravity assisted drainage of blood and CSF and decreasing ICP. Improves surgical orientation, access to the midline structures and decreases the amount of surgical retraction needed to gain access to deeper structures. Also used for some shoulder surgery. Contraindications * Absolute - V-A shunt, R-->L shunt * Relative - PFO, uncontrolled hypertension, extremes of age, autonomic neuropathy Risks * Patients must be returned to supine position rapidly for resuscitative measures in case of an acute cardiovascular collapse * Cardiovascular instability - venous pooling in legs, surgical stimulation near vital structures may result in variable cardiovascular responses * VAE (site of surgery above the level of heart increases risk of air entrainment) * Pneumocephalus * Macroglossia - obstruction to venous and lymphatic drainage of the tongue because of flexed neck --> post operative respiratory obstruction * Quadriplegia - prolonged focal pressure on the spinal cord secondary to the acute flexion of the head, compromise to the cord during episodes of significant hypotension

Answer 31

Concerns * Patient - often paediatric so have parents to deal with as well, co-morbidities, aspiration risk? what is the FB? what urgency of removal * Surgical - type of FB, location, plan - local trauma to GI tract, impaction/obstruction, systemic toxicity? * Anaesthetic - induction method, maintenance, shared airway? Management * A-E approach - resuscitation and supportive care * Investigations guided by presentation and history to guide urgency - 10-20% require endoscopic removal, very few require open approach * Approach to patients and relatives * Focussed anaesthetic history and examination * MDT, senior support, trained assistant * Additional support needed e.g. ENT? * Warm theatre, paediatric equipment if paediatrics case * RSI vs inhalational induction - if needing theatre, likely GA recommended

Answer 32

Generic * Block type (anatomical name, nerves blocked) * Consent * Equipment * Monitoring * Venous access * Skilled assistant * Access to resus/intralipid * Ultrasound and/or nerve stimulator (0.5mA/0.1ms) * Asepsis - chlorhexidine 0.5% * ?LA to skin * PREP-STOP-BLOCK Specific * Patient position * Probe orientation and location * Ultrasound views - Structures identified * Needle type and size, angle of entry * Needle endpoint (in plane/out of plane) * Injection method (max 20ml/minute ideally) * Choice of LA and volume * Post block instructions

Answer 33

Peripheral Revascularisation vs Amputations Pre-operative * commonly cardiovascular disease + diabetes * multiple co-morbidities + usually elderly * high mortality with critical limb ischaemia Intra-operative * anaesthetic technique tailored to patient + co-morbidities * large IV access +/- invasive BP * neuraxial/regional or GA + block * keep MAP >55 * multimodal analgesia * propofol TCI + sedation if needed Post-operative * ongoing regional blockade post-amputation * likely to need ongoing opioids * ?ongoing oxygen for 24hrs for revascularisation

Answer 34

Transphenoidal Hypophysectomy Pre-operative * present with either mass effects of hypersecretion of hormones * special considerations for acromegalic patients or Cushings patients Intra-operative * as for craniotomy * throat pack following intubation +/- OG tube * ?Moffett’s solution to nose * risk of major haemorrhage Post-operative * codeine phosphate * anti-emetic (avoid dex) * head up * nasal pack * avoid PPV/BMV * high risk of post-op DI —> desmopressin * d/w endocrine re: replacement

Answer 35

ROTEM = Rotational Thromboelastometry TEG = Thromboelastography * Assessment of clotting of whole blood * Small amount of blood at body temperature added to a heated cuvette (a little cup) * Pin is suspended into the cup * TEG rotates the cup around the pin * ROTEM rotates the pin in the cup * Impediment to rotation develops as the blood clots * Connected with a mechanical-electrical transducer * Degree of impediment is recorded as "amplitude" and displayed on a time vs amplitude graph Parameters * CT/R - time taken for the amplitude to start climbing -- initiation of clotting -- prolonged if clotting factor deficient, heparin, warfarin, direct thrombin inhibitors -- replace factors e.g. FFP, concentrates or antagonise anticoagulants * CFT/K - time from clot initiation to 20mm -- amplification phase -- activity of clotting factors, effectiveness of fibrin polymerisation, platelet activity and Factor VIII activity -- prolonged in thrombocytopenia, platelet dysfunction, low fibrinogen or severe deficiency of other factors -- shortened in hypercoagulable states -- give cryoprecipitate, fibrinogen or platelet transfusion * a-angle - TEG - slope from 2mm-20mm, ROTEM - slope at 2mm amplitude - determined by rate of reaction between platelets, fibrin and clotting cascade factors -- used as measure of fibrinogen activity -- measure of the "thrombin burst" or propogation phase -- decreased angle in low fibrinogen, poor fibrinogen polymerisation, thrombocytopenia or platelet dysfunction -- give cryo/fibrinogen * MCF/MA - the point where the clot is at its thickest -- usually correlated with platlet count -- consider giving platelets or DDAVP if decreased * TMA/MCF-t - time it takes to reach maximum clot strength -- limited utility (e.g. how long to keep pressure on the groin wound after removing an IABP) * A10/A30/A60 - amplitude at a specific time -- surrogate marker of platelet function, platelet numbers and fibrin concentration -- decreased A10 with low fibrinogen, thrombocytopenia, platelet aggregation inhibitors * CL/LY30 - clot lysis -- consider TXA if accelerated lysis Handy Guide * brandy tumbler - do nothing * red wine glass - give FFP * test tube - give platelets * champagne flute - give cryo * upside down martini glass - give TXA

Answer 36

Diagnostic testing that is performed at or near to the site of the patient, leading to a potential change in the care of that patient. * Blood gas analysis - see separate card * Blood glucose - reaction with a chemical reagent produces a current which is measured and is directly proportional to the glucose concentration * Blood ketones - measures beta-hydroxybutyrate in the blood through an electrical current produced when blood is mixed with a reagent * Urinalysis - pads with reagent on are soaked with the urine sample and the color measured using reflectance colorimetry apart from specific gravity which uses a fibreoptic refractive index method * INR testing - coaguchek - blood mixes with reagent and current is created until the blood has clotted * ROTEM (rotating pin)/TEG (rotating cup) coagulation - see separate card * Hb - haemocue - microcuvette contains 2 reagents which convert Hb into methaemoglobinazide, photometer than measures absorbance at 570 and 880nm * Activated Clotting Time (ACT) - sample of blood mixed with coagulation activators - end point determined by the optical or mechanical properties of the clotting blood * Urine pregnancy tests * HbA1c Advantages * rapid data * increase potential for real time management * usually simple to use * usually low risk Disadvantages * cost * unauthorised use * staff training * sample handling errors * potential to lead to serious health consequences if not performed properly

Answer 37

**Risk Factors** APFEL score Patient related - female - age (not under ~3), teenage/young adult - non smoker - history of PONV - history of motion sickness - ?obesity - preoperative anxiety - intestinal obstruction, metabolic disturbance, uraemia Anaesthesia related - volatiles - N2O - opioids - untreated pain - increased doses of neostigmine - mask ventilation causing gastric distension Surgery related - procedure - eyes, ENT, gynae, neuro, laparoscopic - longer duration of surgery **Management** * Non pharmacological -- avoid gastric distension -- ensure adequate hydrate, minimise fasting -- acupressure * Pharmacological -- minimise exposure to opioids/volatile e.g. multimodal analgesia, regional anaesthesia, TIVA, avoid N2O -- prophylactic antiemetics - single individual antiemetics reduce risk by ~20-40% (RR cyclizine/ondanstron 0.6, dex 0.55, droperidol 0.65, metoclopramide 0.8, prochlorperazine 0.7) — avoid sedating anti-emetics in day case — second antiemetics are additive not synergistic — use multiple antiemetics with different mechanisms (70% reduction in relative risk is best that can be expected) — rescue antiemetics are ineffective if already used prophylactically -- active treatment of hypotension if awake

Answer 38

Pre-operative * may have decreased GCS and impaired airway reflexes - assess pulmonary function * assess ICP, fluid status, electrolytes and BM * assess cardiovascular function Intraoperative * as for craniotomy * NG if risk of post-op bulbar dysfunction * monitor for VAE and nerve tract injury - SSEPs, MEPs * avoid nitrous * TIVA or volatile + remi — TIVA - reduces CMRO2 and maintains auto regulation, reducing ICP, easily titrated during different phases of surgery, rapid smooth emergence with reduced PONV. Risk of awareness if IV dislodged, may be slow to wake, needs depth of anaesthesia monitoring — volatile + remi - no effect on auto regulation in the normal clinical range, possible ischaemic preconditioning * positioning - sitting/prone/lateral * often long procedures * increase analgesia/anaesthesia for pinning * NMBA or remi to prevent coughing * N.Saline maintenance - avoid dextrose containing solutions * Vasopressor infusion to maintain MAP (metaraminol/phenylephrine) * fully reverse with neuromuscular monitoring * maintain anaesthesia until supine and out of pins * deep emergence/airway exchange/remi technique to limit cough and hypertensive response Post-operative * can usually extubate and manage on neurosurgical ward * if significant oedema or loss of bulbar function - keep asleep and allow recovery in ITU * risk of airway obstruction * risk of post-op impairment of respiratory drive * post-op analgesia as for craniotomy * oxygen * anti-emesis

Answer 39

Process of enhancing an individual’s functional capacity to enable them to withstand a forthcoming stressor through an MDT approach Benefits include decreased length of stay, decreased post op pain and decreased post op complications. Medical optimisation * pre-op smoking cessation * reduction in alcohol intake * weight optimisation * management of anaemia * control of blood glucose * optimisation of pharmacological therapy Pre-operative physical exercise * strength and aerobic exercises Nutritional support * pre-operative enteral nutritional support if malnourished * pre-operative carbohydrate loading Stress/anxiety reduction * psychological support * maximise patients motivation * provision of information

Answer 40

Step 1: Prep - preparation - perform WHO sign in - prepare LA solution, place in dedicated tray + hand to assistant - position patient + equipment - pre-scan if required - don gloves + prep site (keep mark visible) Step 2: Stop - stop moment - “I’ve completed my prep, let’s stop before you block” - Assistant - “let’s stop before you block” - check block side - view surgical site mark, verbally confirm side + check consent form (+ ask patient if awake and unsedated) Step 3: Block - perform block - assistant hands tray back - immediately perform black - any delay = re-start (hand tray back to assistant) Aims to decrease incidence of wrong side blocks.

Answer 41

Risk factors * Stasis-endothelial injury - indwelling venous device, surgery, major trauma/burns, prolonged travel, paralysis, varicose veins * Thrombophilias e.g. factor V leiden, antiphospholipid syndrome, protein C/S deficiency * Medical conditions - malignancy, pregnancy, postpartum, MI, CHF, CVA, obesity, IBD, nephrotic syndrome, personal history of VTE * Drugs - COCP, HRT, chemotherapy e.g. tamoxifen * Other factors - increasing age, smoking Pathophysiology * site of vascular trauma or sluggish blood flow * accumulation of fibrin and platelets causes rapid growth of clot * organisation of thrombus, reducing venous return and narrowing the lumen Prevention of VTE * Mechanical methods -- graded anti-embolism stockings - increase blood velocity, promote venous return -- intermittent pneumatic compression - mimic muscle pump effect of walking and promote fibrinolysis -- foot impulse devices - compress plantar venous plexus * Pharmacological methods -- LMWHs -- UFH -- Warfarin -- Factor Xa inhibitors * Patient education * Use of regional anaesthesia * Physiotherapy and nursing care * Avoidance of dehydration

Answer 42

General management * minimum 6 staff to prone (head, feet, 2 each side) * disconnect infusions, monitoring and breathing system when proning to minimise injuries, accidental dislodgement * roll with arms by side, arm care to avoid brachial plexus injury * protect +/- pad eyes * securely fastened reinforced cuffed tracheal tube * care to avoid head rotation * chest and pelvis support with abdomen free * careful padding of pressure areas * CPR + defib in prone position Options for positioning * Pillows * Chest roll * Pelvic roll * Thoracic support/Montreal mattress * Allen table/Jackson table * Wilson frame * Mayfield clamp and pins * Pre-formed foam head support * Gel ring/gel support/gel horseshoe Adverse Effects * Limited access to airway * Increased airway pressure if abdomen splinted and reduced venous return * Displacement of tubes/lines during proning Complications * Direct pressure injuries - skin necrosis, contact dermatitis, tracheal compression, salivary gland swelling, breast injury, injury to the genitalia, compression of the pinna, compression of the femoral neurovascular bundle * Indirect pressure injuries - macroglossia and oropharyngeal injuries, swelling, mediastinal compression, visceral ischaemia - liver, pancreas, avascular necrosis of femoral head, peripheral vessel occlusion, limb compartment syndrome and rhabdomyolysis * Ophthalmic complications - corneal abrasian, visual loss - central retinal artery occlusion, ischaemic optic neuropathy (? due to reduce venous drainage and increased interstitial fluid around the optic nerve) * Peripheral nervous system - all superficial peripheral nerves are at risk from stretch or external compression (especially ulnar nerve, brachial plexus and lateral cutaneous nerve of the thigh) * Central nervous system - caution not to overextend or overflex the c-spine, log roll if necessary. Risk of ischaemic stroke of brain and spinal cord with hypotension and arterial hypoperfusion

Answer 43

Pre-operative * check for airway obstruction * check for reflux - pretreat with PPI * suitable as day case in some * warn about post op cough, haemoptysis, sux myalgia * may be emergency FB inhalation in child Intra-operative * full pre-oxygenation * inhalational induction with maintenance of spontaenous ventilation * benzo/opioid/propofol induction with FM or temporary use of SAD * maintenance - TIVA, intermittent IV bolus, intermittent/continuous volatile - deep anaesthesia required * local anaesthesia to the airway - spray lidocaine to cords * oxygenation - jet (manual/high frequency), spontaneous assisted ventilation, HFNO (apnoeic oxygenation), IPPV through ventilating bronchoscope * sux just prior to bronch/roc then sugammadex * may need gas induction in theatre if potential obstruction Post-operative * biopsied side down * sit fully upright once awake * risk of blood clot causing obstruction * risk of stridor in recory - nebulised adrenaline + ENT involvement

Answer 44

Risks * Pneumothorax

Answer 45

The removal and safe disposal of waste anaesthesia gases from the breathing circuit to avoid contamination of the theatre environment. Continuous exposure of staff to anaesthetic gases has been implicated in: * Cognitive impairment * Spontaneous abortion * Infertility * Haematological malignancy (lymphoid) Aldasorbers * charcoal canisters containing activated charcoal - efficiently adsorb volatile agents (adsorb = molecules present in gas or liquid adhere to the surface of another phase) * cannot remove nitrous oxide * very low resistance * cheap and easy to install in the expiratory limb of a breathing system * not recommended for current use Consists of * gas collection assembly -- connects to APL valve and ventilator relief valve, collects gas vented from the circuit -- uses a 30mm connector - prevents accidental connection to the breathing system * transfer tubing (wide bore) * scavenging interface - structure depends on type of system -- open interface --> active scavenging systems use a pump or fan to generate a pressure gradient, drawing gas to the disposal assembly (open to air to prevent negative pressure being transmitted to the patient) --> must be low pressure and high flow to remove up to 75L/min -- closed interface --> passive scavenging systems use a series of positive and negative pressure relief valves (when gas pressure in the collection assembly is increased, positive relief valve opens and gas enters a reservoir bag, when gas pressure in the disposal assembly falls, negative relief valve opens and gas enters disposal assembly) * more transfer tubing * disposal assembly (high flow) Passive disposal systems are no longer recommended because their outlets for waste anaesthetic gases cannot be strictly controlled, problems may arise due to direction/strength of wind, water vapour running back into the system or waste gases from one theatre passing back into another.

Answer 46

Pre-operative * kids, ex-prem, post hyperthyroid, ?MH Intra-operative * GA, avoid sux * oculocardiac reflex - glyco, ?block, normocapnia * anti-emetic Post-operative * multimodal analgesia (clonidine)

Answer 47

Procedures aimed at resecting epileptogenic foci, disconnection surgeries to reduce seizure frequency and propagation and procedures aimed at reducing seizure frequency via neuromodulation. History of chronic seizures that are refractory to medical therapy. MRI, EEG, neuropsychological evaluation required. Types of surgery * temporal resection - resection of anterior temporal lobe, amygdala and part of the hippocampus * extratemporal resection - focal lesion, lobar or multilobar resections in the frontal, occipital and parietal lobes * hemispherectomy - diffuse disease pathology affecting one cerebral hemisphere, risk of large volume blood loss * laser interstitial thermal therapy - fibroptic catheter via a burrhole for MRI guided laser ablation of selected epileptogenic foci (GA required) * disconnection surgery - total corpus callostomy, fewer risks than hemispherectomy * seizure modulation devices - vagal nerve stimulators - exact mechanism of action unclear, usually left sided - battery replacement is quick and can be undertaken as a day case with a SAD * deep brain stimulation - possibly reduces neuronal activity in the target area Pre-operative * thorough preoperative assessment * look for sodium/platelet/white cell and LFT abnormalities associated with long term antiepileptic use * FBC, U+Es, coagulation, LFTs, X match * ECG - Brugada type ST changes common and J wave abnormalities associated with sodium channel blocking AEDs * Clarify patients regular seizure type and pattern Intra-operative * maintenance of adequate cerebral perfusion pressure * avoid increases in ICP * arterial access and large bore peripheral access for craniotomies * remifentanil infusion helpful * consider use of normal saline rather than CSL if ketogenic diet being followed * intraoperative invasive EEG monitoring may be required - do not give benzos, potent short acting mu-agonists may be required to activate interictal epileptiform activities (alf 20-100mcg/kg) * reduce depth of anaesthesia during this period, warn of small risk of awareness, NMBAs may be used to prevent movement and interference * intraoperative functional neuromonitoring - TIVA, reinforced ETT and bite block if MEPs monitored * if seizures develop, cease stimulation, irrigate surgical field with ice cold saline, propofol boluses +/- benzos (in conjunction with neurophysiologist) Post-operative * delayed emergency common * avoid large doses of opioids * NSAIDs can be given if large blood loss not occurred and no other contraindications

Answer 48

Non electrical * mercury - increases in volume proportionally as temperature increases, much higher usable range than alcohol * alcohol - increases in volume proportionally as temperature increases, safer than mercury but measurable range less convenient * bimetallic strips - different metals expand at different rates as they warm up, causing the strip to bend in one direction or the other * bourdon gauge - as temperature increases, volume of gas in a tube increases, trying to turn the gauge * liquid crystal - contains heat sensitive liquid crystals that change colour to indicate different temperatures Electrical * resistance wire thermometer (usually platinum) - resistance of materials increases with increases in with temperature, slow but highly accurate * thermocouple - voltage produced when two disimilar metals come together, the voltage varies with temperature (usually copper/nickel alloy and copper construction) - linear response * thermistor - semiconductor,as temperature increases, the resistance to flow of electrical current through the material decreases - non linear response * thermography (IR thermometer) - detects proportion of radiation which is emitted in the IR specturm, proprtional to the amount of thermal energy present in the item being measured

Answer 49

Pre-operative * respiratory assessment including functional capacity, lung function tests, exercise testing * assessment of active cardiac conditions + cardiac risk factors * prediction of perioperative mortality e.g. thoracoscore Intra-operative * indications for lung isolation (DLT vs BB) * plan regional anaesthesia according to surgical approach e.g. thoracic epidural * invasive monitoring (consider site of CVC) * temperature + fluid management * consider TIVA * IV access in non dependent arm (if lateral) Post-operative * avoid post-op ventilation if possible * multimodal analgesia * physiotherapy * post-op humidified oxygen * HDU/ITU as appropriate * CXR in recovery

Answer 50

Pre-operative * thyroid status - history, examination, investigations - thyrotoxic? * airway - history, examination, investigations - FNE/CT/USS) — ask re: voice, positional dypnoea, exercise — trache narrowed/deviated — retrosternal Intra-operative * induction - NMBAs? Remi? * intubation - specialised ETT for monitoring recurrent laryngeal nerve * optimise surgical conditions - head up, hypotensive anaesthesia * haemostasis challenge prior to extubation - supraglottic exchange Post-operative * PACU/HDU - monitor airway * keep sat up * monitor neck for bleeding * measure calcium (PTH) - 2hrs post op * prescribe T4 * analgesia - paracetamol/NSAIDs +/- opioids * complications — vocal cord palsy — pneumothorax — laryngeal oedema — tracheomalacia — thyroid storm — haematoma - oedema causing obstruction — hypocalcaemia

Answer 51

A tracheostomy is a surgical procedure that creates and opening in the anterior wall of the trachea to facilitate airway access and ventilation. Most tracheostomies are placed between the second and third tracheal rings. Indications Emergency * acute upper airway obstruction with failed intubation or where intubation is impossible * people who have undergone an emergency cricothyroidotomy * select fractures of the oropharynx, face and neck (e.g. LeFort III fracture of the mid face) * penetrating laryngeal trauma Elective * In critical care — to assist weaning from artificial ventilation — to facilitate withdrawal of sedation — ongoing airway toilet/reduce secretion retention — long term ventilation in patients with chronic conditions — protect airway in neurological dysfunction * Planned surgical traches — severe OSA refractory to other therapies — severe subglottic stenosis or vocal cord paralysis not responsive to conventional therapies — prior to planned head and neck procedures Contraindications * Absolute - local sepsis of the anterior neck, absence of the cervical trachea, uncorrectable bleeding diathesis, patient refusal, tumour * Relative - haemodynamic instability, severe hypoxaemia, severe coagulopathy/anticoagulation, platelet dysfunction/thrombocytopenia * Percutaneous contraindications - gross distortion of the neck, suspected tracheomalacia or cartilage abnormalities, inability to palpate landmarks (short, fat neck), inability to extend neck, C-spine instability, immature trachea, blood vessels crossing the surgical field Techniques * Informed consent, monitoring, trained assistant, sterile field * Increased FiO2 prior to procedure * Palpation/ultrasound * Lidocaine/adrenaline * Open under GA though can be performed under local anaesthesia — incision made above the cuff of the ETT — cuff then deflated and pulled back slightly — tracheostomy tube placed through the incision — tracheostomy cuff inflated and tubing connected to ventilator/anaesthetic circuit — capnography to confirm placement before removal of ETT — bronchoscope to confirm device at least 2cm above the carina * Percutaneous dilational with single dilator (Seldinger wire/Rhino) usually under sedation and paralysis — tapered dilator modified Seldinger approach — bronchoscope at ETT tube tip to visualise whole process — bronchoscope tracheostomy tube after insertion to confirm position and to suction blood/secretions * Percutaneous dilation all with multiple dilators (Seldinger wire/Ciaglia) * Percutaneous with guidewire and dilating forceps Complications * Immediate — Bleeding — Pneumothorax or pneumediastinum from false passage creation or guide wire puncture — Oesophageal perforation — Tracheal ring fractures — Loss of airway — Airway fire (open procedure using electrocautery) — Failure * Early - bleeding, dislodgement, obstruction * Late - erosion into vessels, tracheal dilatation, cuff-related stenosis, granule at a, stenosis related to traumatic insertion, cord/laryngeal dysfunction National Tracheostomy Safety Project guidelines

Answer 52

**Immediate Immunologic** * acute haemolytic reaction * non haemolytic transfusion reaction (non haemolytic febrile reaction) * allergic reaction to proteins, IgA * anaphylaxis * TRALI **Immediate Non-Immunologic** * bacterial contamination * TACO (fluid overload) * non immune haemolysis * TRALI * related to IV access - air embolism, thrombophlebitis * related to infusion - hyperkaelamia, citrate toxicity --> hypocalcaemia, hypothermia * coagulopathy - dilutional/consumptive **Delayed Immunologic** * acute haemolytic reaction * transfusion associated graft vs host disease * immune sensitisation * immunomodulation **Delayed Non-Immunologic** * iron overload * disease transmission - viral, bacterial, parasites, prion ______________________________________________________________________________________ **Acute Haemolytic Reaction/ABO Incompatibility** * IgM binds to RBCs —> complement fixation * intravascular haemolysis * cytokine release, platelet activation, mast cell degranulation * causes head/chest/flank pain, fever/chills/rigors, anaphylaxis, SOB, AKI, hypo/hypertension, N+V, urticaria, haemoglobinura, DIC * stop infusion, support organs, maintain adequate renal perfusion, careful documentation and investigation **Delayed Haemolytic Reaction** * Minor incompatibilities * IgG antibodies bind to surface antigen but do not activate complement * extravascular haemolysis occurs over 7-21 days * cause low Hb, jaundice (unconjugated hyperbilirubinaemia) and positive DAT test **Febrile Non Haemolytic** (due to recipient antibodies reacting with donor antigens) * leucocyte antigens bind to antibodies --> bind complement * release of pyrogens IL-1/IL-6/TNF alpha * causes pyrexia, shivering, general discomfort, headache, myalgia * rarely may progress to hypotension, vomiting and respiratory distress * slow or stop the infusion and give antipyretic **TRALI** (due to donor antibodies reacting with recipient antigens) * leucocyte antibodies in donor blood activate neutrophil granuloctye in immune form * reactive lipid products released from the membranes of donor blood cells activate neutrophil granulocyte in non immune form * activated neutrophil granulocytes --> lodge within pulmonary vascularture --> endothelial damage --> pulmonary capillary leak syndrome with exudation of fluid and protein into alveoli * causes SOB, decreased sats, non cardiogenic pulmonary oedema, cyanosis, fever, tachycardia and hypotension * ARDS either during or within 6hr of transfusion **Allergic Reaction** * common and usually mild * presence of foreign proteins in donor plasma, IgE mediated * cause pruritus and urticaria, with or without fever * STOP transfusion and administer antihistamines * if symptoms resolve in < 30 mins + no CVS instability --> restart (if symptoms recur, then abandon that unit) * anaphylaxis may occcur in patients with hereditary IgA deficiency or pre-existing anti-IgA antibodies - reaction occurs immediately after commencing infusion - manage as per anaphylaxis **Transfusion Related Circulatory Overload (TACO)** * too much fluid or transfused too rapidly * acute LVF - dyspnoea, tachypnoea, non productive cough, raised JVP, hypotension, tachycardia * STOP transfusion, standard medical treatment for LVF *diuretic, oxygen etc* **Infections** * bacterial contamination - infrequent but can cause fulminant sepsis with high mortality * caused by contamination during venepuncture or if an asymptomatic bacteraemia at time of donation * causes high fever, rigors, erythema and cardiovascular collapse during or shortly after transfusion of the contaminated unit * contaminated bags may seem unusally dark in colour or contain gas bubbles * viral transmission -- hep A - negligible risk per unit of transfused blood -- hep B - 1 in 100000 -- hep C - < 1 in 1000000 -- HIV 1/2 - < 1 in 4000000 * prion infection - theoretical risk **Transfusion-associated graft-vs-host disease** * very rare * 90% of cases are fatal * donor-derived immune cells mount an immune response against host tissue * cause maculopapular rash, abdominal pain, diarrhoea and abnormal LFTs + pancytopenia

Answer 53

Physics In-Plane - can see needle tip - direct visualisation of whole needle/catheter - longer needle path (risk of damage to structures) - possibility of unrecognised tip Out-of-Plane - shorter path, increased patient comfort - easier for catheters - familiarity (vascular access ultrasound) - possibly decreases nerve injury - difficult to identify tip of needle Artefacts * Acoustic - reverberation, comet tails, speckle, mirror image * Anatomic - misinterpretation * Patient factors - obesity, air, oedema, muscle atrophy, abnormal anatomy Optimising Image * P - pressure * A - alignment * R - rotation * T - tilt * Gain * Depth

Answer 54

Preload - inadequate - low CVP - haemostasis, IV fluid - excessive - high CVP - diurese, ?CVVH Afterload - excessive - raised PVR/PAP - inhaled nitric oxide, sildenafil/prostacyclin Contractility - impaired - raised CVP, reduced PAP, reduced RVSWI - inotrope, 2nd Inotrope, adrenaline Heart Rate - inadequate - low HR - pacing - excessive - high HR - antiarrhythmic Heart Rhythm - abnormal - arrhythmia - DCCV, antiarrhythmia Coronary Perfusion Pressure - low MAP, low SVR - vasopressor, increase volume, IABP, ventricular assist device

Answer 55

Pre-operative * range of patients * previous eye surgery Intra-operative * block (most commonly) or GA (scleral buckle requires GA - risk of Brady) * avoid nitrous if GA + gas used * avoid tetracaine, high volume Sub-Tenons * dark room Post-operative * tends to be day case * positioning (to hold retina in place for healing) * no flying while bubble in eye * simple analgesia

Answer 56

Weaning = the process of liberating the patient from mechanical ventilatory support. Predictors of weaning failure * advanced age * prolonged mechanical ventilation * COPD * increased MV * positive fluid balance General requirements * lung disease stable/resolving * low FiO2 (<0.5) * low PEEP requireement (<5-8cmH2O) * haemodynamic stability (little to no inopressors) * able to initiate spontaneous breaths - good neuromuscular function * able to protect airway Predictors of success * RR <30 * TV >5ml/kg * FVC >15ml/kg * MV <15L/min * Maximum insp pressure <-30 * Other indices focussing on lung function Spontaneous breathing trial - on 5+5 support Optimising weaning success * optimise respiratory muscle power - nutrition, avoid NMBAs, decrease steroid use and other contributors to critical illness-induced weakness, avoid exhaustion, normal electrolytes, normal FRC, physiotherapy * decrease respiratory work - sit up, recrease respiratory demand (decrease CO2, correct metabolic acidosis), decrease resistance, increase compliance * optimise ventilatory drive (stop sedation, consider causes from the brain to the NMJ) * increase oxygenation and carrying capacity (sit up, avoid atelectasis, correct anaemia, correct acid-base disturbance) * address cardiac dysfunction - removal of positive pressure ventilation may unmask LV dysfunction, treat ischaemia * address sputum clearance - treat infection, chest physio, suction, bronch, mucolytics