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