Anaesthetics Flashcards
How to induct pt?
cannulate, give fentanyl and midazolam to relax, measure vitals (bp, O2 sats, ECG, CO2 trace); then to fully put patient to sleep give IV bolus of propofol
Why CO2 monitoring important?
o CO2 trace most important bit to see if airway is patent and being ventilated
Why ECG important?
identify any anomalies (can’t have any ST elevation/depression/indication of myocardial ischaemia without review before operation; wide QRS peaks indicating RBBB is fine though, LBBB not good tho; if do have ischaemic changes better to keep pt bradycardic as heart requires less O2 from coronary artery [which it can’t get as ischaemic] and there’s a longer diastole for more perfusion of blood through the coronary artery)
What to do if hypotensive?
give phenelephrine/metaraminol/noradrenaline (in order of strength from weakest to strongest; alpha agonist – vasoconstrictor) or ephedrine if really low bp (alpha agonist on vessels for vasoconstriction and beta agonist on myocardial muscle for greater contractility)
Pain control during and immediately post-op?
morphine IV or neural block (local anaesthesia directly to nerve branches where operating, use US probe and guide to fibrous tissue between muscles; agents = lidocaine or levobupivacaine)
Maintaining GA during op?
use agent like sevoflurane/isoflurane (inhaled) or can use NO
Max dose local anaesthesia?
lignocaine (3mg/kg without adrenaline, 6mg/kg with), bupivacaine (2mg/kg without adrenaline, 2.5mg/kg with)
Anti-emetics used?
dexamethasone at induction and if needed use ondansetron at end before wake up
Stage 1 anaesthesia?
analgesia/disorientation; pt feels effects of medication but not yet unconscious; known as the induction stage, sedated but can have convo, slow regular breathing; progresses in this stage from analgesia free of amnesia to analgesia with concurrent amnesia; stage ends with LOC
Stage 2 anaesthesia?
excitement/delirium; S+Ss = disinhibition, delirium, uncontrolled movements, loss of eyelash reflex, hypertension, tachycardia; airway reflexes remain intact and hypersensitive to stimulation (try not to manipulate airway especially endotracheal tubes and deep suctioning manoeuvres); high risk of laryngospasm (tonic closing of chords) especially if airway manipulation; spastic movements, vomiting, rapid and irregular insp can compromise pt’s airway; use fast-acting agents to make sure stage 2 to 3 asap
Stage 3 anaesthesia?
surgical anaesthesia; target for GA procedures; features = no eye movement and resp depression, airway manipulation safe; 4 planes, plane 1 = regular spontaneous breathing, constricted pupils and central gaze; plane 2 = intermittent cessations of resp with loss of corneal and laryngeal reflexes, halted ocular movements and increased lacrimation; plane 3 = complete relaxation of intercostal and abdo muscles and loss of pupillary light reflex; plane 4 = irregular resp, paradoxical rib cage movement and full diaphragm paralysis so apnoea
Stage 4 anaesthesia?
overdose; too much anaesthetic agent given relative to amount of surgical stimulation = worsening of already severe brain/medullary depression; starts with resp cessation and ends with potential death, skeletal muscles flaccid, pupils fixed and dilated, bp low, weak and thready pulse as suppression of cardiac pump and vasodilation in peripheries; make sure not in this stage and keep in stage 3 for as little as poss
What is important in pre-op hx PMH?
CVS (incl. hypertension and exercise tolerance, risk of acute cardiac event increased in anaesthesia), resp (adequate O2 and ventilation essential in reducing risk of acute ischaemic events in peri-operative period), renal (disease like anaemia, coagulopathy, biochemical disturbances increase incidence of surgical complications), endocrine (mainly DM and thyroid as meds need specific changes in perioperative period), other (female of reproductive age [preggers], African descent [undiagnosed sickle cell])
Past anaesthesia hx questions?
had it before, any issues, well intra and post-op, pt experienced any previous post-op N+V
Malignant pyrexia and its dangers (why asked in FH)?
autosomal dominant and leads to muscle rigidity even with neuromuscular block followed by rise in temp
SH questions in per-op hx?
smoking, alcohol and exercise tolerance
ASA grading after pre-op examination?
1-5 (normal, mild systemic disease, severe systemic disease, severe systemic disease with constant threat to life, moribund and not expected to live without op) and E if emergency
Pre-op investigations?
bloods = FBC (anaemia and thrombocytopenia to correct to reduce CVS), U+Es (assess baseline renal function, help inform any potential IV fluid management), LFTs (important for liver metabolism and function for med choice and dosing), clotting screen (any deranged coagulation from iatrogenic [warfarin], inherited coag or liver impairment), group and save or cross match (group and save determines blood type and cross-match mixes blood with donor to see if reaction for predicted transfusion); imaging = ECG (hx of CVS and major surgery), CXR (not routine and only if necessary = resp illness and no CXR in 12 months, new CVS symptoms, recent travel from area with endemic tuberculosis, significant smoking; can use spirometry as well if chronic); other = pregnancy (women of reproductive age), sickle cell (FH or African descent), urinalysis (any evidence or suspicion of ongoing glycosuria or UTI but not routine), MRSA swabs (all pts swabs from nostril, perineum and other sites and if isolated give topical ointment/wash pre-op)
Airway exam components?
look at face for any obvious facial abnormalities (retrognathia, dentures); ask pt to open mouth to assess: degree of mouth opening (better if inter-incisor dist above 3cm), do they have teeth/loose teeth, oropharynx (ask pt to protrude tongue and use Mallampati classification for intubation difficulty assessment); finally assess neck (flex, extend, laterally flex neck then maximally extend neck and measure dist between thyroid and chin [less than 6.5cm = intubation difficult])
Tool for pre-op management?
RAPRIOP (reassurance, advice, prescription, referral, investigations, observations, patient understanding and follow-up)
Advice for pre-op?
fasting (eating = 6 hours before, dairy = 6 hours, clear fluids = 2 hours); stomach empty of contents so less risk of pulmonary aspiration in perioperative period leading to aspiration pneumonitis (inflammation caused by acidic gastric contents leading to desquamation) and pneumonia (secondary infection after pneumonitis or direct aspiration of infected material)
Prescriptions management for pre-op?
– categories to either stop/alter/start meds; stop = CHOW (clopidogrel 7 days before, hypoglycaemics, oral contraceptive pill/HRT 4 wks before due to DVT risk, Warfarin stopped 5 days prior and changed to LMWH), need INR <1.5; alter = subcut insulin (switched to IV variable rate insulin infusion), long-term steroids (continued as Addisonian crisis if stopped, switch to IV if need be); start = LMWH (VTE risk assessment done and prescribe if needed, most pts unless Cis for neck/endo surgery; if GI surgery for cancer and lower limb joint replacement then should be discharged with TEDs and 28 days prophylaxis LMWH), TED stockings (all pts unless vascular surgery, check for cis [peripheral vasc disease, peripheral neuropathy, recent skin graft, severe eczema]), abx prophylaxis (orthopaedic, vasc, GI surgery mostly)
Advice for T1 DM pre-op?
(should be first on morning list); night before reduce subcut insulin by 1/3, omit morning insulin and start IV variable rate insulin infusion pump/sliding scale which is syringe with saline and Actrapid; also infusion 5% dextrose at 125ml/hr and check BMs every 2 hours (keep this until pt can eat and drink but have to overlap insulin infusion with normal SC insulin [give rapid acting SC 20 mins before meal and stop IV 30-60 mins after meal])
Advice for T2 pre-op?
only management if not diet controlled; metformin stopped morning of surgery and everything else 24 hours before and managed same as T1 diabetics peri-operatively
When to bowel prep for pre-op?
if colorectal then need laxatives or enemas to clear colon; bowel prep less common and harmful if elderly with cardiac/renal disease, prolongs stay and recovery time; general rule for not required = upper GI, HPB, small bowel, right hemi-colectomy or extended right hemi-colectomy; left hemi-colectomy, sigmoid colectomy or abdominal-perineal resection = phosphate enema on morning; anterior resection = 2 sachets picolax day before or phosphate enema morning
When to do group and save?
for major GI, HPB, vasc, gynae, ortho
Follow-up post-op recommendations?
most major = appt and follow-up clinic; day-case = telephone follow-up from nurse specialist
Extreme complications of N+V post-op?
anxiety, increased recovery time, hosp stay longer, aspiration pneumonia, incisional hernia, suture dehiscence, bleeding oesophageal rupture and metabolic acidosis
RFs for post-op N+V?
female, younger age, previous PONV/motion sickness, use of opioids, non-smoker, intra-abdo laparoscopy, intracranial/middle ear surgery, squint surgery, gynae, long ops, poor pain control post-op, opiate analgesia/spinal, inhalational agents (isoflurane/NO), prolonged anaesthesia, dehydration/bleeding, overuse of bag and mask ventilation
Patho for post-op N+V?
vomiting centre in lateral reticular formation of medulla oblongata (controls and coordinates movements in vomiting – diaphragm, stomach and abdo muscles) and chemoreceptor trigger zone in postrema in 4th ventricle and outside BBB so responds to circ stimuli (is input for vomiting centre with GI, vestibular and higher cortical structures); neurotransmitters (dopamine and 5HT3 at chemoreceptor trigger zone, Ach and histamine at vestibular apparatus, dopamine at GI and histamine and 5HT3 at vomiting centre)
Assessment for N+V pre-op?
check aspiration risk; may need NG tube; what operation, likely to cause PONV, ABCDE, which anaesthesia/drugs, any factors contributing, what antiemetic therapy; think of alternative causes of nausea = infection, GI (bowel obstruction/post-op ileus), metabolic (hypercalcaemia/uraemia/DKA), medication (abx/opioids), CNS (raised ICP), psych (anxiety)
Management of op N+V?
prophylaxis = reduce opiates/volatile gases/spinals, antiemetic therapy (dexamethasone); conservative measures = hydration, analgesia, no obstructive cause; pharma = impaired gastric emptying/gastric stasis (prokinetic agent like metoclopramide [dopamine antagonist – also if metabolic imbalance] or domperidone [dopamine antagonist] unless obstruction), hyoscine (anti-muscarinic) can help reduce secretions; opioid induced N+V responds well to ondansetron (5HT3 antagonist) or cyclizine (H1 histamine antagonist)
What is BiPAP?
biphasic; pressure gradient of air in means it breathes for you (e.g. 20 pressure then 5 and goes in waves so 15 times per min); for type 2 resp failure (high CO2)
What is PEEP?
positive end expiratory pressure; slight pressure during expiratory phase to keep alveoli open so don’t collapse (means more SA to V ratio for gas exchange)
What is CPAP?
continuous air in (pt can breathe a bit but not enough to breathe for self); for type 1 resp failure (low/normal CO2)
What is ASB?
automated spontaneous breathing = bit of pressure to aid in inspiration so can reach correct tidal volume
What is Quinsy?
peri-tonsillar abscess
What are the D and E from ABCDE?
D = anaesthesia and sedation, GCS, PERLA; E = bowels (assess), urine, E+D, glucose, insulin and fluid balance
What is the RASS score?
(Richmond agitation and sedation score) – scale from +4 to -5; +4 = combative, +3 = very agitated, +2 = agitated, +1 = restless, 0 = alert and calm, -1 = drowsy, -2 = light sedation, -3 = moderate sedation, -4 = deep sedation, -5 = unarousable
Causes of type 1 resp failure?
Fluid in alveoli, alveolar collapse causing inadequate oxygenation
Cause of type 2 resp failure?
Inadequate ventilation (instead of normal lung expansion, it is limited for COPD, muscular dystrophy etc)
Volume control for invasive ventilation?
Pressure increases until target volume reached then it stops and expiration occurs
Pressure control for invasive ventilation?
Pressure constant until target time reached then it stops and expiration occurs
Two types of muscle relaxants and what they are?
Depolarising (30 secs to work, for emergencies; suxamethonium; non-competitive inhibitor) and non-depolarising (routine anaesthesia, 120-180 secs; atracurium, rocunorium, vecuronium; competitive inhibitor of ach at muscle)
What to give with suxamethonium and why?
Atropine so no vagal effects of slowing the heart
Do you want high or low solubility in water of inhalational anaesthesia (sevoflurane/isoflurane etc) and high or low solubility in fat?
Low solubility in water so can build up a higher partial pressure in the alveoli and less circulates round the body so easier to get rid of after put under and wake up easier; higher fat solubility so can dissolve through the BBB and enter the brain so the pt feels its effects with lower partial pressure needed
What is regional anaesthesia?
target specific nerves (brachial plexus etc), for post-op pain relief
What is neuraxial anaesthesia?
spinal (subarachnoid block – needle into CSF so through ligaments and dura; single bolus, anaesthesia, injected at lumbar) and epidural (needle between ligaments and dura where catheter passed; continuous infusion, anaesthesia/analgesia, thoracic or lumbar)
Types of local anaesthesia?
lidocaine (15 mins duration, immediate onset, small procedures); bupivacaine (regional, spinal, epidural; 10 min onset; 2 hours anaesthesia and 12-24 analgesia)
Types of sedation?
short-term = midazolam (endoscopy, regional analgesia); long-term = propofol +/- alfentanil (ITU, intubated pts for transfer)
Types of inhalational anaesthetic agents?
isoflurane (cheapest, slower and offset), desflurane (quick onset and offset), sevoflurane (gas induction and quick onset)
IV hypnotic types?
propofol (quick onset and commonest), thiopenthal (quick and mostly emergencies) and ketamine (used in CVS instability and also analgesia)
