Peri-operative Medicine/Anaesthesia Flashcards
What is Virchows triad
Abnormal blood flow- stasis
Abnormal blood components- hypercoagubility
Abnormal vessel wall- endothelial injury
What are risk factors for VTE?
older age previous VTE smoker malignancy pregnancy recent prolonged immobility
How may a DVT present?
Unilateral calf swelling Tender Painful Low grade pyrexia Pitting oedema 65% are asymptomatic
How do you investigate a possible DVT?
Ultrasound
D-dimer
Wells score
d-dimer is not specific to DVT
Explain the wells score
Each is worth one point Clinical signs of DVT Heart rate > 100bpm Recent surgery or immobilisation Previous PE or DVT Haemoptysis Malignancy Alternative diagnoses less likely than PE
Less than or equal to one- DVT is unlikely and need a D-dimer to exclude
Greater than 1- DVT needs to be confirmed using ultrasound
How would you treat a patient with a confirmed DVT
DOACs, however in some cases vitamin K antagonist. Patients with a provoked DVT will need it for 3 months .
Unprovoked DVT or recurrent DVT may need lifelong anticoagulation
Which drugs need to be stopped pre-op?
CHOW:
Clopidogrel- stop 7 days pre-op
Hypoglycaemics- most sto pped 24 hours before. Metformin stopped the morning of . Sub cut insulin, stopped, reduce dose by 1/3 and omit morning insulin
Oral Contraceptive pill or HRT- stop 4 weeks before
Long term steroids- may be switched to IV to reduce risk of Addisonian crisis
What drugs do you start pre-op
LMWH
TED stockings
Abx prophylaxis
What is the ASA score?
Determine if a patient is healthy enough to tolerate anaesthesia
ASA1: normal, healthy patient
ASA2: A patient with mild systemic disease e.g. obesity, well controlled DM/HTN, smoker
ASA3: A patient with severe systemic disease e.g. poorly controlled DM,HTN, COPD morbid obesity,
ASA4: A patient with a severe systemic disease that is a constant threat to life e.g. recent MI, TIA, sepsis, ESRD not undergoing regular dialysis
ASA5: Moribund patient, not expected to survive without the op e.g.ruptured AAA, massive trauma
ASA5: A declared braindead patient who’s organs are being donated
What investigations would you do pre-op?
Bloods- FBC/ U+Es/LFTs/ condition specific e.g.TFTs, HbA1c, clotting
ECG- if hx of cardiac disease or major surgery
Spirometry e.g. COPD and asthma patients
Urinanalysis- identify a UTI
MRSA swab
Briefly outline the WHO pain ladder
Simple analgesics: paracetamol–> NSAIDS
Weak Opiates: codeine and tramadol
Strong opiates: fentanyl and morphine
What are the two types of fluids available?
Crystalloid, colloid.
For each patient, what should you consider when prescribing fluids?
Age, weight, cardiac function, co-morbidities. Reason for admission. Electrolytes recently given?
What is the aim of maintenance fluids?
To hydrate - all distribute into all compartments.
What is the aim of resuscitation fluids?
To improve tissue perfusion - will stay in intravascular space.
What are the 5R’s of fluid prescribing?
Resuscitation, Routine maintencence, Replacement, Redistribution, Reassess.
A patient is depleted of fluids. What signs should you look for when assessing fluid status?
Dry mucous membranes, reduced skin turgor, decreased urine output, orthostatic hypotension, increased cap refill time, tachycardia, hypotension.
A patient is overloaded with fluids. What signs should you look for when assessing fluid status?
Raised JVP, sacral odema, peripheral oedema, pulmonary oedema.
In what circumstances may you replace ongoing losses?
Third space losses (i.e. fluid losses into spaces that are not visible e.g. bowel lumen in bowel obstruction). In diuresis. When pt is tachypnoeic or febrile. When pt is losing electrolyte-rich fluid.
In what conditions are electrolyte imbalances common?
Dehydration - high urea:creatine ratio.
Vomiting - low K+, low Cl-, alkalosis,
Diarrhoea - low K+ and acidosis.
What fluids would you prescribe for patient with sepsis?
Fluids that get into intravascular space
What is the 4, 2, 1 rule regarding paediatric fluid maintenance?
First 10kg = 4ml/kg/hr. Next 10kg = 2ml/kg/hr. Thereafter = 1ml/kg/hr.
Why is hyponatremia so important to correct?
Can lead to transient or permanent brain damage due to cerebral oedema.
How do you manage a patient on long term oral steroids in the peri-operative period?
Switch oral steroids to 50-100mg IV hydrocortisone
If any associated hypotension, fludrocortisone can be added
Minor ops- oral prednisolone can be restarted immediately post op. If surgery is major than they may require IV hydrocortisone for up to 72 hours post op
What might you find on physical examination of a pt in pain?
Tachycardia, tachypnoea, hypertensio, sweating, flushing, agitation, unwilling to mobilise
Why is the WHO pain ladder used?
To titrate analgesia
A pt is already on NSAIDs and they are not aiding in their role as pain relief. What would you think of prescribing next? (on who pain ladder)
Weak opiates - codeine, tramadol.
What is the mechanism of action of NSAIDs?
Inhibit COX enzymes needed to convert arachidonic acid to downstream products in the prostanoid pathway. This stops the synthesis of prostaglandins so reeduces inflammatory response
Name 3 side effects of NSAIDs
I-GRAB Interactions with other meds (e.g. warfarin) Gastric ulceration Renal impairment Asthma sensitivity (trigger!) Bleeding risk
How do NSAIDs increase the bleeding risk of a pt?
Reduce platelet function (they stop prostacyclin which usually promotes platelets)
If you are worried of a patient having NSAIDs for a long time due to side effects, what can you prescribe alongside it?
PPI
Why do NSAIDs cause renal impairment?
Prostaglandins are inhibitied in this pathway. Usually, prostaglandin cause vasodilation of the afferent arteriole of the kidney to help maintain GFR. When your pt takes NSAIDS, they inhibit this vasodilation. SO you get poor renal perfusion - and kidney is more unable to respond to a reduced GFR
What are two side effects of opiates?
Constipation, nausea, sedation, confusion, pruritus, respiratory depression
What can you prescribe alongside opiates if a pt suffer with their side effects?
Laxatives and anti-emetics
Why wouldn’t you co prescribe a weak opiod with a strong opiod?
They inhibit the same receptor !! (Mop u)
Which opioids would you consider giving to someone who had eGFR of 50?
Oxycodone or Fentanyl as pt has renal impairment
What is patient controlled analgesia?
- Used when analgesia required exceeds the capacity of the nursing staff.
- So, an IV pump is used to provide a bolus of analgesia when a button on the pump is pressed.
- This allows the analgesia to be tailored to the pt’s requirements.
- The device records the opiod being administered.
Why may a pt present with neuropathic pain after an operation?
Irritation to a nerve or nerve injury during the procedure.
What drugs can be used to manage peri-operative neuropathic pain?
Gabapentin, Amitriptyline, Pregabalin
How can pain be assessed?
Subjectively - use SQITARS/SOCRATES. Objectively - HR, HTN?, Sweating, flushing? Agitiated, unwilling to mobilise?
Can assess in multiple environments - in bed, when taking a deep breath in, when mobile.
How does surgery affect the stress response?
Heightens it !! Huge increase in stress hormone and sympathetic response.
What hormones are involved in stress response? Describe this process
Increase in adrenaline, ACTH, cortisol, glucagon, GH = all catabolic (to create more glucose). Insulin tries to counteract this.
What are risks of a diabetic pt having anaesthesia and surgery?
- During surgery: Stress of surgery/trauma/infection can make hyperglycaemia harder to control as there is insensitivity to insulin
- Before and after surgery:GA/NBM before surgery/ post surgery vomiting means keeping glucose in normal range is challenging
- Increased risk of hospital infections
- Renal impairment
- MI and cardiac ischamia can be painless in a DM pt.
- Ketoacidosis can be mistaken
What is the target blood glucose in peri-operative /anaesthesia management?
Target capillary blood glucose 6-10mmol/L (for DM pt).
What three groups are DM pt divided into peri-operatively?
Insulin dependent, oral hyperglycaemic managed, diet controlled.
How do you (peri-operatively) manage insulin dependent DM pt?
- Establish good diabetic control before the operation.
- Give insulin as a continuous iv infusion during operative period
- Give infusion of dextrose through op (to balance the insulin or to make up dietary intake)
- Add potassium to dextrose
- Monitor blood glucose and electrolytes in op and after.
How do you manage DM pt’s who have oral hyperglycaemia?
Stop metformin - risk lactic acidosis. Stop Sulphonylureas can be stopped on the day of the op.
If blood glucose rises a little bit, can do sub-cut insulin to control insulin.
If patient has diet controlled DM, how would you manage them peri-operatively?
Do blood glucose. May not need intervention.
How do you manage poorly controlled DM on emergency admission?
Risk of DKA. Aim is to control glucose with rehydration and infusion of insulin, glucose and potassium.
What should be given alongside VRIII?
IV glucose, K, NaCl substrate solution
What is the aim of a pre-assessment before an operation?
- Assess good glycaemic control <8.5% Hba1c.
- Determie safest anaesthetic
- Timing of operation on the list (i.e. do they need to be first to limit starvation)
- VTE assessment risk
- Need for home support after surgery
- Assess other co-morbidities and complications
- Bloods
Regarding blood sugar, what are your aims whilst in the operating theatre?
- Regular blood glucose measurements.
- Feet visible, limit pressure sores, ensuring fluids are given.
What are post theatre aims for pt with DM?
- Maintain blood glucose.
- Maintain electrolyte balance
- Optimise renal and cardiac function
- Anti-emetics
- Fluids - Hartmann’s
What is the half life of IV insulin?
6mins. Some are 15 mins.
Why is insulin having a fast half life an advantage in surgery?
Fast half life = easy to adjust in surgery where there can be haemodynamic changes,
How many kcal in 1L of 5% dextrose?
170 kcals
Why are anticoagulants used in surgical patients?
Prevention of stroke, VTE embolism, PE, DVT, non-valvular AF
With regard to warfarin, what measurements mean a patient is fit for surgery?
INR of 1.5 or below.
Why might a surgical pt be on warfarin?
May have a mechanical heart valve. May have had a recent VTE?
How is warfarin reversed in emergency surgery?
- IV Vit K if surgery can be delayed by 6-12hrs and INR is >1.5.
- If surgery can not be delayed, human prothrombin complex (1 hr reversal).
- Fresh frozen plasma if HPC not available. FFP- contraindicated in fluid overload
A high risk pt usually on warfarin has had it reversed for surgery. What do you prescribe to ensure their blood does not clot?
LWMH for high risk pts. Can be stopped shortly before surgery then restarted after.
A pt on rivaroxiban is due to have surgery soon. When should they stop taking it?
24-72hrs before surgery. This depends on their kidney function, half life and the surgical procedure
What is the name of the antidote for dabigatran?
Idarucizumab - rapid reversal for emergency surgery or bleeding
What is the name of the antidote for apixaban?
Andexanet alfa
When should he COCP be stopped before surgery?
4 weeks before
Why should COCP be stopped before surgery?
Risk of VTE
What is commonly used as DVT prophylaxis?
Dalteparin
How is dalteparin administered?
Subcut injection
What should be given alongside LWMH prophylaxis?
Graduated compression stockings
Why should you wait 4 hours after inserting an epidural anaesthetic before giving LWMH?
Risk of epidural haematoma - blood accumulates in the epidural space which mechanically compresses the spinal cord - not good.
Which surgical procedures would need extended dalteparin/lwmh prophylaxis after surgery?
Major procedures such as orthopaedic (THR/TKR) as they have a higher risk of VTEs —> DVT/PE
A pt is already taking prednisolone. How should they be managed during surgical procedures (including pre and post)?
IV Hydrocortisone at induction AND immediately post op for first 24 hours.
Double normal steroid dose once eating/drinking fro 24-72 hours depending on the operation
What happens when a pt’s (who has been taking steroids) steroids are stopped suddenly?
Addisonian crisis
Describe what happens in addisonian crisis?
Reduced glucocorticoid and mineralcorticods. Hyponatraemia Hyperkalaemia Hypoglycaemia Reduced consciousness Low BP/blood vol
Why is addisonian crisis hard to detect post surgery/in surgery?
- Manifestations = hypotension, tachycardia, hypoxia and fever. These mimic common post op complications
- Can present as nausea, vomiting, diarrhoea = similar to effects of anaesthetic drugs
What are the 7 sources of pyrexia (7 C’s)?
Chest (infection) Cut (wound infection) Catheter (UTIs) Collections (abdo, pelvic) Calves (DVT) Cannula (infection) Central line