Anaesthetics and perioperative care Flashcards
Dropping sats following intubation →
? oesophageal intubation - does not allow for adequate lung ventilation
Capnography should also be present to confirm the correct siting
When is jaw thrust preferred over head-tilt/chin-lift?
suspected c-spine injury
When are oropharyngeal airways most commonly used?
bridging to more definitive airway
Easy to insert and use
No paralysis required
Ideal for very short procedures
Laryngeal masks are commonly used in day surgery.
Why are they unsuitable in non-fasted patients?
Poor control against reflux of gastric contents
Also not suitable for high pressure ventilation
When are tracheostomies useful? What is the issue with them?
Reduces the work of breathing (and dead space)
May be useful in slow weaning
Dries secretions - requires humidified air
Abdominal pain, bloating and vomiting following bowel surgery →
?postoperative ileus
deranged electrolytes can contribute so measure K+, magnesium and phosphate
Volatile liquid anaesthetics (isoflurane, desflurane, sevoflurane) are used for induction and maintenance of anaesthesia. What are their potential adverse effects?
Myocardial depression
Malignant hyperthermia
Halothane (not commonly used now) is hepatotoxic
Nitrous oxide is used for maintenance of anaesthesia and analgesia. What is the main contraindication?
May diffuse into gas-filled body compartments → increase in pressure.
Should therefore be avoided in certain conditions e.g. pneumothorax
What is propofol used for?
Mechanism of action?
Adverse effects?
Use:
Very common induction agent for GA and also used in ICU for ventilated patients
Has some anti-emetic effects - useful for patients with a high risk of post-op vomiting
MOA:
potentiates GABAa
ADRs:
* Pain on injection (due to activation of the pain receptor TRPA1)
* Hypotension
What is thiopental good for?
Mechanism of action?
Adverse effects?
Use:
highly lipid soluble so quickly effects brain
MOA:
barbituate, potentiates GABAa
ADRs:
laryngospasm
What is Etomidate good for?
Mechanism of action?
Adverse effects?
Use:
Causes less hypotension than propofol and thiopental during induction and is therefore used in haemodynamic instability
MOA:
Potentiates GABAA
ADRs:
* Primary adrenal suppression (secondary to reversibly inhibiting 11β-hydroxylase)
* post-op vomiting
* Myoclonus
What is Ketamine good for?
Mechanism of action?
Adverse effects?
Use:
* Acts as a dissociative anaesthetic.
* Doesn’t cause a drop in blood pressure so useful in trauma
MOA:
Blocks NMDA receptors
ADRs:
* Disorientation
* Hallucinations
What are the oral fluids/fasting rules before surgery?
patients having surgery may drink clear fluids until 2 hours before their operation
clear fluids are water, fruit juice without pulp, coffee or tea without milk and ice lollies
Patients are generally advised to fast from non-clear liquids/food for at least 6 hours before surgery
How is nasogastric feeding administered?
Contraindication?
Risk?
Usually administered via fine bore naso gastric feeding tube
May be safe to use in patients with impaired swallow
Often contraindicated following head injury (esp basal skull fractures) due to risks associated with tube insertion
Complications relate to aspiration of feed or misplaced tube
When is naso-jejunal feeding used?
Safe to use following oesophagogastric surgery
Insertion of feeding tube more technically complicated (easiest if done intra operatively)
Avoids problems of feed pooling in stomach and risk of aspiration
What is a feeding jejunostomy?
Risks?
Surgically sited feeding tube
May be used for long term feeding
Low risk of aspiration and thus safe for long term feeding following upper GI surgery
Main risks are tube displacement and peritubal leakage immediately following insertion, which carries a risk of peritonitis
Who is Total Parenteral Nutrition (TPN) used in?
Where should it be inserted?
Risk of long term use?
definitive option in those patients in whom enteral feeding is contra indicated
Should be administered via a central vein (e.g. subclavian) as it is strongly phlebitic and would collapse peripheral veins
Long term use is associated with fatty liver and deranged LFTs
What is the guidance for use of metformin peri-operatively?
take as normal leading up to surgery
on day of surgery:
if taken BD take as normal
if taken three times a day, omit lunchtime dose
What is the guidance for use of sulfonylureas peri-operatively?
prior to admission take as normal
on day of surgery:
if taken once daily in the morning omit the dose that day
if taken BD, omit the morning dose for morning surgeries or both doses for afternoon surgeries
How should gliptins and GLP-1 analogues be used perioperatively?
take as normal throughout including on day of surgery
How should SGLT-2 inhibitors (gliflozins) be used peri-operatively?
take as normal prior to admission, omit completely on the day of surgery
How should once daily insulins (e.g. Lantus, Levemir) be used peri-operatively?
Dose reduction of 20% the day before and the day of surgery
How should twice daily Biphasic or ultra-long acting insulins (e.g. Novomix 30, Humulin M3) be used peri-operatively?
on the day of surgery:
Halve the usual morning dose. Leave evening dose unchanged
Outline the American Society of Anaesthesiologists (ASA) classification
ASA I = A normal healthy patient
ASA II = A patient with mild systemic disease Examples include: current smoker, social alcohol drinker, pregnancy, obesity (BMI 30 - 40), well-controlled Diabetes /Hypertension, mild lung disease
ASA III = A patient with severe systemic disease Substantive functional limitations
ASA IV = A patient with severe systemic disease that is a constant threat to life (e.g. MI/HF/stroke)
ASA V = A moribund patient who is not expected to survive without the operation
ASA VI = A declared brain-dead patient whose organs are being removed for donor purposes
Which surgical patients are considered to be at higher risk of VTE?
hip/knee replacement
hip fracture
GA and a surgical duration of > 90 minutes
surgery of the pelvis or lower limb with GA and a surgical duration of > 60 minutes
acute surgical admission with an inflammatory/intra-abdominal condition
surgery with a significant reduction in mobility
Advice for women on COCP/HRT approaching surgery?
stop for 4 weeks leading up to surgery
What is the most suitable course of action for a patient on warfarin about to have major abdo surgery?
Stop his warfarin and commence treatment dose low molecular weight heparin
Outline the timings of the most common causes of post-op fever
Day 1-2: ‘Wind’ - Pneumonia, aspiration, pulmonary embolism
Day 3-5: ‘Water’ - Urinary tract infection (especially if the patient was catheterised)
Day 5-7: ‘Wound’ - Infection at the surgical site or abscess formation
Day 5+: ‘Walking’ - Deep vein thrombosis or pulmonary embolism
Any time: Drugs, transfusion reactions, sepsis, line contamination
Why does poor post-op pain management carry a risk of pneumonia?
period of significant pain = shallow breathing
lack of deep breathing is a risk factor for both atelectasis and respiratory tract infections
Isolated fever in well patient in first 24 hours following surgery?
physiological reaction to operation
Surgical diabetic patients are likely to have what 3 things?
increased risk of wound & respiratory infections
increased risk of post-operative AKI
increased length of hospital stay
Most patients taking only oral antidiabetic drugs may be managed by manipulating medication on the day of surgery, depending on the particular drug.
What are the exceptions?
How would you manage these patients?
if more than one meal is to be missed
patients with poor glycaemic control
risk of renal injury (e.g. low eGFR, contrast being used)
in such cases a VRIII should be used
Which insulin dependent patients can be managed post-op by adjustment of their normal insulin regime as opposed to starting a VRII?
patients treated with insulin who have good glycaemic control (HbA1c < 69 mmol/mol) and are undergoing minor procedures
Excessive infusions of any intravenous fluid carry what risk?
development of tissue oedema and potentially cardiac failure
excessive administration of sodium chloride is a recognised cause of hyperchloraemic acidosis
so Hartmans solution may be preferred
Why should you avoid of using hypotonic (0.45%) sodium chloride in paediatric patients?
risk of hyponatraemic encephalopathy
How should a patient with a v low Hb the day before surgery be managed?
Pre-operative blood transfusion
What is the agent of choice for rapid sequence of induction?
Sodium thiopentone- rapid onset of action
Metabolites build up quickly
Unsuitable for maintenance infusion
Which drugs are patients with myasthenia gravis very sensitive to?
Non-depolarising agents, such as rocuronium (blocks nicotinic receptors)
The myasthenic patient has fewer available nicotinic receptors meaning that they are more sensitive to non-depolarising blockade
may require more prolonged ventilation
When would you Cross-match 2 units for surgery?
transfusion likely
Salpingectomy for ruptured ectopic pregnancy, total hip replacement
When would you Cross-match 4-6 units for surgery?
transfusion definite
Total gastrectomy, oesophagectomy, hepatectomy, oophorectomy, cystectomy, Elective AAA repair
cause of new onset atrial fibrillation following gastrointestinal surgery?
anastamotic leak
What is the muscle relaxant of choice for rapid sequence induction for intubation?
ADR? Contraindications?
Suxamethonium (succinycholine)
ADR: transient hyperkalaemia, fasciculations
Contraindications: patients with penetrating eye injuries or acute narrow angle glaucoma, as suxamethonium increases intra-ocular pressure
What is required prior to surgery for patients taking 10mg or more of prednisolone?
Hydrocortisone supplementation to prevent Addisonian crisis
what is local anaesthetic toxicity? How can it be treated?
initial overactivity of the central nervous system (CNS) and subsequent depression either due to intravenous administration or excess usage
It can be treated with IV 20% lipid emulsion (the most commonly used brand is Intralipid).
Which anaesthetic agent has one of the strongest analgesic effects?
ketamine
Which anaesthetic agent reverses the action of midazolam?
Flumazenil
Which anaesthetic agent is associated with hepatotoxicity?
Halothane
It should be avoided in patients with hepatic dysfunction, and scavengers should be used in theatres as accumulation of the drug may be harmful to theatre staff
How does lidocaine work? ADRs?
it is an amide - blockage of sodium channels
ADRs: nausea, dizziness, tinnitus and tremor.
How are surgical patients at low and high risk of VTE managed?
low risk - anti-embolism compression stockings (TED stockings)
high risk - TED stockings + pharmacological prophylaxis
drugs:
Fondaparinux sodium (SC injection)
LMWH e.g. enoxaparin
Unfractionated heparin (UFH) (alternative to LWMH in patients with CKD)
Best method to obtain IV access in a child who is peripherally shut down?
intraosseous infusion - proximal tibia
Best method of IV access for long term chemo in a patient who is peripherally shut down?
Hickman line- most reliable long term option
Most Hickman lines are inserted under local anaesthesia with image guidance
Best method of temporary IV access in a patient who is haemodynamically stable with good veins?
20 G (pink) peripheral cannula
Long term mechanical ventilation in trauma patients + choking and bringing up sputum after meals = ?
tracheo-oesophageal fistula formation
When should LMWH be started in relation to hip replacement surgery?
6-12 hours after surgery
What bowel prep is required leading up to colonoscopy?
laxatives the day before
no food 24hours before procedure
What is malignant hyperthermia? How should it be managed?
autosomal dominant disorder presenting as a hypermetabolic crisis
-hyperthermia, hypercapnia, tachycardia, muscle rigidity, rhabdomyolysis, and arrhythmia
commonly associated with volatile inhalational anaesthetic agents and the muscle relaxant succinylcholine (suxamethonium)
IV dantrolene therapy
Complications of perioperative hypothermia?
Coagulopathy: increased intra-operative blood loss
Prolonged recovery from anaesthesia
Reduced wound healing: local vasoconstriction which reduces perfusion to the skin
Infection
Shivering: significant increase in metabolic rate which can result in myocardial ischaemia in some patients
What are the recommendations for post-op wound cleaning?
Use sterile saline for wound cleansing up to 48 hours after surgery.
Advise patients that they may shower safely 48 hours after surgery.
What drugs may impair wound healing?
Non steroidal anti inflammatory drugs
Steroids
Immunosupressive agents
Anti neoplastic drugs
Outline the use of cocaine in anaesthesia
cocaine hydrochloride- used in paste form as a local anaesthetic
applied topically to the nasal mucosa in ENT surgery
It has a rapid onset of action and causes marked vasoconstriction.
Use of Bupivacaine?
much longer duration of action than lignocaine so may be used for topical wound infiltration at the end of surgical procedures
cardiotoxic and is therefore contra indicated in regional blockage in case the tourniquet fails
agent of choice for intravenous regional anaesthesia e.g. Biers Block?
Prilocaine
Which patients may need an ECG before surgery?
over 65 before major surgery
diabetics and patients with renal disease before intermediate surgery
What is suxamethonium apnoea?
Pseudocholinesterase deficiency - rare abnormality in the production of plasma cholinesterases
increased duration of action of muscle relaxants e.g. suxamethonium and will cause resp arrest unless pt is ventilated
Name the key transfusion reactions
Got a bad unit
G raft vs. Host disease
O verload
T hrombocytopaenia
A lloimmunization
B lood pressure unstable
A cute haemolytic reaction
D elayed haemolytic reaction
U rticaria
N eutrophilia
I nfection
T ransfusion associated lung injury
What is the blood transfusion threshold and Hb target?
Without ACS:
threshold = 70 g/L
target = 70-90g /L
With ACS
threshold = 80 g/ L
target = 80-100 g/ L
How quickly should one unit of red cells be transfused?
emergency = STAT
non urgent = over 90-120 minutes
Irradiated blood products are required in patients following bone marrow and stem cell transplants for what reason?
to prevent graft versus host disease
(depleted of T lymphocytes)
How is TRALI differentiated from TACO?
hypotension in TRALI vs hypertension in TACO
How should TRALI be managed?
Titrate oxygen, give IV fluids and consider escalation of care
Which blood product is most likely to cause an iatrogenic septicaemia with a Gram-positive organism?
Platelets - stored at room temperature
The first step in management of any suspected transfusion reaction is what?
stop the transfusion!!!
Fever, abdominal pain, hypotension during a blood transfusion →
acute haemolytic reaction
due to RBC destruction by IgM-type antibodies
Hypotension, dyspnoea, wheezing, angioedema during a blood transfusion →
anaphylaxis
What is the universal donor of FFP?
AB RhD negative blood
What are the key steps to take before initiating a blood transfusion?
Process for blood transfusion:
1. Confirm patient identity
2. Check compatibility
3. Check expiry date and unit number
4. Inspect bag for integrity of plastic casing
5. Blood out of fridge over 30 mins should be
transfused within 4 hours or discarded
6. Record everything
What is involved in blood conservation technique?
1.Increase red blood cell mass – e.g. correct iron deficiency
2.Reduce peri-operative blood loss – e.g. op for regional not GA where possible
3.Optimising transfusion practice – allogenic transfusion/ autologous transfusion (cell salvage)
When should you stop warfarin pre-op? DOAC?
warfarin = 4-5 days
DOAC = 2 days
What factors increase risk of post-operative nausea and vomiting?
young female
non-smoker
PMH of motion sickness
use of volatile anaesthetics
