anaesthetics intra-op Flashcards
pre-op routine tests NICE
which drugs are controlled
Drugs that are in ‘controlled’ - opiods, ketamins, ie drugs of abuse
drugs that might be given in a drug error eg K looks like NaCl - accidentally give K = death
what is positive pressure ventilation
where air is forced by a mechanical ventilator into a non-breathing patient
benefits of positive pressure ventilation
improved CO elimination
improved oxygenation
relief from exhaustion as the work of ventilation is removed
High concentrations of oxygen (up to 100%) may be administered accurately.
what is positive end expiratory pressure
If adequate oxygenation cannot be achieved, a positive airway pressure can be maintained at a chosen level throughout expiration;
by attaching a threshold resistor valve to the expiratory limb of the circuit.
to re-expand underventilated lung areas -> reducing shunts and increasing PaO2.
what can ventilators control
- Tidal volume—which provides precise control of volume and PaCO2 (ie volume controlled)
- Pressure necessary to inflate the lungs (ie pressure controlled)—which re-duces risk of barotrauma
- I:E ratio (I:E= the ratio of inspiratory to expiratory time)
- Respiratory rate
- Inspiratory time.
Other controls may be available to adjust:
- Inspiratory flow waveform
- End-tidal pause.
risks/considerations when using positive pressure ventilation
- Everyone’s lungs blow up to a different volume – so if you put a fixed pressure you avoid barotrauma
- But you could cause volume trauma
- If have empysema – less ability for lungs to expand – so if you put pressure in = possible damage to the lungs – potentially blown lobe
acute mx of asthma
- O SHIT ME
- Oxygen
- Salbutamol
- Hydrocortisone or prednisolone
- Ipratropium
- Theophylline
- Magnesium sulphate
- Everything else
- Can go into T1 or 2 resp failure
- If in type 2 – exhausted, not ventilating properly
acute Mx of pneumothorax
- Tension = CVS problems, high/low HR, low BP
- Needle aspiration
- Drain if not tensioning
Never ventilate someone with a pneumothorax – put pressure into the lungs – force air out of the hole – make a tension pneumothorax – lung collapses as it gets smaller and smaller
surgeons can do chest compressions
mx of haemothorax
drain
Mx of anaphylaxis
- Adrenaline
- Steroids – hydrocortisone
- Antihistamine
- Keep them in hospital because have second spikes of anaphylaxis
Mx of aspiration in surgery
- Turn pt head down
- Suction
- Might need AB when they go onto the wards
indications for invasive blood pressure monitoring
intra-arterial in high risk or long cases,
significant co-morbidities
when difficult IV access is anticipated,
when pt seriously ill and need titrated vasoactive medicine
indications for non-invasive BP monitoring
measured in all cases,
needs to be maintained within 10% of the patients normal BP -
give vasopressor drugs or ionotropic drugs to raise
indications for invasive monitoring
- Pt factors
- Surgical factors
- Beat to beat BP
- Electrolyte
- Long surgery
- Blood loss
- Pt unwell
cautions with arterial lines
- If think there might be a clot you need to open up the line and let the blood come out so that the clot can be removed
- Need to flush regularly so that reduce chances of there being a clot
- The clot might come out in the saline when you take everything out
- If flush and there is a clot there, the clot will go distally because it is an arterial line = ischemia of finger
why give fluids in surgery
because have been starved - so increase blood vol and rehydrate
hypotensive
colloids
stay in intravascular space
people are allergic
use crystalloids
considerations with crystalloids
don’t use plasmalyte if increase in K, or kidney problems
triggers for giving a blood transfusion
- If haemorrhage
- Loss certain percentage of blood vol/hr
- Ongoing severe blood loss – Hb 80 in IHD, Hb 70 in normal
if have HbS - might give prophylactic transfusion
why do people get cold in surgery
drugs cause vasodilation - lose heat
lower the threshold for body to warm itself up
stop shivering - muscle relaxant
spinal blocks SNS response to temperature - no shiver or goosebumps
the drugs going into the system are cold
not conscious so can’t do behavioural response
why is a low body temperature a problem
- Reduces coagulation because the enzymes work slower
- Reduce drug metabolism because liver enzymes work slower
- Unpleasant when wake up because SNS kicks in = shiver etc
- Worse wound healing – wound infection
how is body temperature increased theatre
- Bair hugger
- Warming the IV fluids
- Warm gasses through the humidifier
indications for an arterial line
- Monitor BP if previous cardiac problem - beat to beat
- cardiac surgery
- py really inwell - sepsis, need to know readings to monitor
- Look at glucose - dm
- Look at blood gases
surgical factor - blood loss
importance of team brief
gives everyone a voice - so they feel empowered to point out any mistakes or things that are going wrong
oropharyngeal airway
guedel airway
Bag and mask airway
ET tube
I-gel
supraglottic airway
not definite airway
pre-op when do you do UE, FBC, BM
most patients
if Hb <100g/L tell anaesthetist
UE important if:
- starved
- dm
- diuretics
- burns
- hepatic or renal disease
- ileus
- parenterally fed
pre-op cross match
blood type is identified and units are allocated to patient
group and save
blood type identified and held
waiting crossmatch if required
when do you do an ECG pre-op
if >55yrs or poor exercise tolerance
hx of myocardiac ischemia
HTN
rheumatic fever
or other heart disease
when do you do an echo pre-op
if suspicion of poor LV function
when do you do pulmonary function tests
if known pul disease or obesity
when do you do lateral cervical spine XR
flexion and extension views
hx of RA/ankylosing spondylitis/Down’s
to see if difficult intubation
when do you do MRSA screen pre-op
according to local policy
not CI to surgery
place last on list to minimise risk, and prophylaxis AB
document
when would you do specific blood tests pre-op
LFT - jaundice, malignancy, alcohol abuse
amylase - acute abdo pain
blood glucose - if dm
drug levels
clotting studies - liver/renal disease, DIC, massive blood loss, if on valproate/warfarin/heparin
TFT if thyroid disease
sickle test - Africa, west indies, mediterranean, and if origins in malarial areas - including most of india
indication for LA
if unfit/unwilling to undergo GA
local nerve blocks eg brachial plexus or spinal blocks (CI if anticoagulated, or local infection)
use long acting LA eg bupivacaine
epidural anaesthesia
anaesthetizing pain fibres L3/4 space is usually used. (in labour of T10-S5)
safe and effective
reduced catecholamine secretion
can be regularly topped up - catheter is left in epidural space
help lower BP in pre-eclampsia
Before siting an epidural, check platelet count is >75x10(9),
insert wide-bore IV access
Full aseptic technique
monitor BP every 5min for 20min, and record block height and density.
Continuous electronic fetal monitoring is required.
It is not uncommon to see a fetal bradycardia following epidural insertion due to maternal hypotension. Give IV fluids—it almost always recovers.
Top-ups are required ~2-hourly. Recall anaesthetist if inadequate pain relief within 30min.
If the epidural is used for LSCS, remember that the block will take longer to establish compared with spinal.
complications of epidural anaesthesia
failure to site
patchy block
hypotension
dural puncture (<1:100)
post-dural puncture headache
transient or permanent nerve damage (extremely rare)
increased risk of operative vaginal delivery
benefits of combined spinal epidural anaesthesia
quicker pain relief
option of prolonging with the epidural
spinal anaesthesia
used for most C sections
reaasier than epidurals
produce dense block
single injection - so may wear off if the procedure is lonh (>2hrs)
more profound hypotension than an epidural
summarise regional anaesthesia
regional anaesthesia is split into peripheral nerve blocks or neuraxial anaesthesia
aim is to reduce nerve conduction of painful impulses to higher centres via the thalamus where the perception of pain occurs
either used alone or as a supplement to GA by gibing prolongued and effective postoperative analgesia
especially useful for operations on the lower limbs and abdo where avoidance of GA is preferable because of co-morbidities (cardiac and pul)
may still cause loss of airway and need same resus fascilites as for GA
locating peripheral nerves need US or peripheral nerve stimulators to minimise nerve trauma and maximise success rates
continuous regional anaesthesia
involves placement of a catheter near nerve to allow continuous delivery of LA, as compared to a single dose of LA
adrenaline with LA
slows systemic absorption of LA = increases LA duration
useful in areas of increased vascularity eg intercostal blocks where risk of systemic absorption is higher
systemic effects from adrenaline are especially hazardous in CVS disease or raised BP
contraindicated in digital or penile blocks, and around the nose or ears (risk of local ischemia)
lidocaine
max dose in healthy adult =3mg/kg IBW
prilocaine
moderate onset, dose is 3-5mg/kg IBW.
MAx 400mg,
low toxicity - drug of choice for bier’s block (IV regional anaesthesia)
bupivacaine
(t1/2=3hrs) = slow onset and prolonged action.
More cardiotoxic than the others.
CI in bier’s block.
Dose for local infiltration is 2mg/Kg IBW to a max of 150mg
levobupivacaine
isomer of bupivacaine, less cardiotoxic.
Dose for local infiltration or peripheral nerve block: 2mg/kg (max 150mg).
Use <150mg (use 5–7.5mg/mL solution) for epidural; <15mg for intrathecal.
ropivacaine
(t1/2=1.8h) dose 2mg/Kg IBW, less cardiotoxic than bupivacaine, less motor block when used epidurally.
CI for IV regional anaesthesia (Bair’s block) and paracervical block in anaesthetics
tetracaine
(t1/2=1h) slow onset, high toxicity.
eye drops for topical anesthesia and now topically as an alternative to EMLA.
Also available as a gel (combined with adrenaline and lidocaine) for open wounds
benefits of regional anaesthesia
- Spinal = less chronic pain after the surgery
- Better for the patient
- Less anaesthesia needed
- Patients recover better
- Epidural used if long surgery because you can attach a catheter, also top and bottom so pt can mobilise faster
administering spinal anaesthesia
- at L3/4 – feel the release of pressure
- weighted - Need to know what time it goes in so you can test how well it is working.
- Because weighted can tilt the pt so that the bolus moves so that it is more effective
use in a short op
administering epidural
reduce tension syringe – when tension reduces know in the epidural space – don’t go further otherwise pierce dura = post puncture headache
- Skin, subcutaneous tissue, supraspinous ligament, intraspinous ligament, ligamentum flava
use in long operation and post-op
opioids and anaesthetics are given into the epidural space by infusion or boluses
conduct of anaesthesia
principles - hypnosis, analgesia, muscle relaxation
induction - IV propofol or thiopental, or gaseous sevoflurane or nitrous oxide mixed in with Ox
airway control - facemask or oropharyngeal airway, or intubation - intubation needs muscle relaxation with a depolarising/non-depolarising neuromuscular blocker
maintenance of anaesthesia - either volatile agent added to nitrous oxide ox mix, or high dose opiates with mechanical ventilation, or IV anaesthesia eg propofol
recovery - change inspired gases to 100% ox, stop anaesthetic infusions and reverse muscle paralysis. Extubate when spontaneously breathing - ox by facemask
signs of LA toxicity
peri oral tingling and paraesthesia
progressing to drowsiness, seizures, coma and cardioresp arrest
Mx - ABC resus, lipid emulsion
paracetamol
0.5-1g/4hr PO
(up to 4g daily;
15mg/4hr IV over 15mins
in children <50Kg; up to 60mg/kg/d)
caution in liver impairment
NSAIDS
ibuprofen
- 400mg/8hr PO
- for musculoskeletal pain and renal or biliary colic
CI
- peptic ulcer
- clotting disorders
- anticoags
- in children due to risk of Reye’s syndrome
cautions
- asthma
- renal/hepatic impairment
- HF
- IHD
- pregnancy
- elderly
morphine and diamorphine
morphine - 10-15mg/2-4h IV/IM
diamorphine - 5-15mg/2-4h PO, SC, slow IV - but may need much more
can give transdermal (once baseline requirements are established) or sublingual
CI of opioids
hepatic failure
head injury
reversal of opioids
naloxone (100-200mcg IV followed by 100mcg increments every 2mins until responsive
SE of epidural analgesia
less because the drug is more localised
watch for resp depression and LA induced autonomic blockade (reduced BP)
adjuvant analgesics
radiotherapy for bone cancer pain
anticonvulsants
antidepressants
gabapentin or steroids for neuropathic pain
antispasmodics eg hyoscine butylbromide (buscopan 10-20mg/8hr PO/IM/IV) for intestinal or renal tract colic
if brief pain relief needed - inhaled NO2 with 50% O2 as entonox with an on-demand valve
Transcutaneous electrical nerve stimulation (TENS), local heat, local or regional anaesthesia, and neurosurgical procedures (eg excision of neuroma) may be tried but can prove disappointing.
