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4th year > Perioperative and Critical Care > Flashcards

Perioperative and Critical Care Flashcards

1
Q

Respiratory failure

A

= PaO2 < 8kPa

Type 1 - Hypoxia with normal or low PaCO2
Type 2 - Hypoxia with hypercapnia (PaCO2 > 6kPa)

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2
Q

Causes of type 1 respiratory failure

A
  • Ventilation/perfusion mismatch – pneumonia, pulmonary oedema, PE, asthma, emphysema, pulmonary fibrosis, ARDS
  • Hypoventilation
  • Abnormal perfusion
  • Right -> left cardiac shunts
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3
Q

Management of type 1 respiratory failure

A
  • Treat underlying cause
  • Give oxygen by facemask (up to 60%)
  • Assisted ventilation if still low O2 despite 60% O2
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4
Q

Causes of type 2 respiratory failure

A
  • Pulmonary disease – COPD, asthma, pneumonia, end-stage pulmonary fibrosis, obstructive sleep apnoea
  • Reduced respiratory drive – sedative drugs, CNS tumour or trauma
  • Neuromuscular disease – poliomyelitis, myasthenia gravis, Guillain-Barre syndrome
  • Thoracic wall disease – flail chest, kyphoscoliosis
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5
Q

Management of type 2 respiratory failure

A
  • Treat underlying cause
  • Controlled O2 therapy, starting at 24%, then recheck ABG and gradually increase as long as PaCO2 stays steady or lowers
  • Consider assisted ventilation if rising hypercapnia and hypoxia
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6
Q

Indications for ABG

A
  • Unexpected deterioration in ill patient
  • Any acute exacerbation of chronic chest condition
  • Any impaired consciousness or impaired respiratory effort
  • Signs of CO2 retention (bounding pulse, drowsiness, flapping tremor, headache)
  • Signs of hypoxia (cyanosis, confusion, visual hallucinations)
  • To validate measurements from transcutaneous pulse oximetry
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7
Q

ABG interpretation

A
  1. pH acidosis or alkalosis?
  2. pCO2 high or low? does this fit with pH - if yes then respiratory problem
  3. HCO3 high or low? does this fit with pH - if yes then metabolic problem
  4. pO2 normal given FiO2?
  5. any compensation? partial or complete?
  6. anion gap, normal 10-18 = (Na+ + K+) - (Cl- + HCO3-)
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8
Q

Increased anion gap

A

Metabolic acidosis and increased anion gap

  • due to increased production or reduced excretion of fixed/organic acids
  • lactic acid (shock, infection, tissue ischaemia)
  • urate (renal failure)
  • ketones (DM, alcohol)
  • drugs/toxins
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9
Q

Normal anion gap

A

Metabolic acidosis and normal anion gap

  • due to loss of bicarbonate or ingestion of H+ ions
  • renal tubular acidosis
  • diarrhoea
  • drugs
  • addison’s disease
  • pancreatic fistula
  • ammonium chloride ingestion
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10
Q

Metabolic alkalosis

A

High pH, high HCO3-

  • vomiting
  • K+ depletion (diuretics)
  • burns
  • ingestion of base
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11
Q

Shock

A

= circulatory failure resulting in inadequate organ perfusion
= low BP, systolic <90 or MAP <65, and evidence of tissue hypoperfusion (mottled skin, low urine output, serum lactate >2, low GCS, pallor, cool peripheries, tachycardia, slow cap refill, tachypnoea, oliguria)
- BP = CO x SVR (so two causes of shock)

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12
Q

Shock - inadequate cardiac output

A

Hypovolaemia

  • bleeding
  • fluid loss (vomiting, burns, ‘third space loss’)

Pump failure (cardiogenic)

  • cardiogenic shock (ACS, arrhythmias, aortic dissection, acute valve failure)
  • secondary causes (PE, tension pneumothorax, cardiac tamponade)
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13
Q

Shock - peripheral circulatory failure

A

Sepsis (acute vasodilation from inflammatory cytokines - may be warm and vasodilated after fluid therapy, or cold and shut down before)

Anaphylaxis

Neurogenic (spinal cord injury, spinal anaesthesia)

Endocrine failure (Addison’s, hypothyroidism)

Drugs (anaesthetics, antihypertensives)

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14
Q

Management of shock

A

If BP unrecordable call cardiac arrest team.

Septic shock - abx, fluids (500ml boluses of crystalloids eg 0.9% saline), oxygen, critical care review

Anaphylaxis - secure airway, 100% O2 given, IM adrenaline every 5 mins, IV access for chloramphenamine and hydrocortisone

Cardiogenic - O2 titrate to normal, diamorphine IV, investigations and monitoring - correct arrhythmias/U+E abnormalities/acid-base disturbance, optimise filling pressure with either plasma expander or inotropic support

Hypovolaemic - raise legs, IV fluid bolus crystalloid, titrate to HR BP UO

Haemorrhagic - stop bleeding! 2L crystalloid, crossmatch blood, FFP with red cells

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15
Q

Sepsis

A

= life-threatening organ dysfunction caused by a dysregulated host response to infection

Moderate-high risk if…

  • altered mental status
  • raised resp rate
  • low BP
  • low urine output
  • signs of infection
  • rigors or temp <36
  • impaired immunity
  • recent surgery/trauma
  • mottled/ashen/cyanotic skin, non-blanching rash
  • -> sepsis 6!
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16
Q

Assessing fluid balance - underfilled

A
  • tachycardia
  • postural drop in bp (low bp is late sign)
  • reduced cap refill
  • reduced urine output
  • cool peripheries
  • dry mucous membranes
  • reduced skin turgor
  • sunken eyes
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17
Q

Assessing fluid balance - overfilled

A
  • raised JVP
  • pitting oedema of sacrum, ankles, legs/abdomen if severe
  • tachypnoea
  • bibasal crepitations
  • pulmonary oedema on CXR
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18
Q

Fluid challenge

A

Rapid infusion of (200ml) fixed volume to see effect on SV, CVP / PAWP and correct hypovolaemia

0.9% saline as isotonic and same Na+ content as plasma
Crystalloids (saline, Hartmann’s, plasmolyte) also

Colloids (eg gelatin-based or blood) useful for resus but are expensive and not for maintenance

19
Q

WHO analgesic ladder

A
  1. Paracetamol
    • NSAID
    • codeine
    • morphine (IV/PO/PCA) -codeine
20
Q

PCA review

A

Review daily by pain team or anaesthetist:

  • pain score
  • dosage history
  • pump settings
  • side effects
21
Q

Nine survival variables pre-surgery

A 
Age
Sex
Socioeconomic status
Hx of IHD
Hx of HF
Hx of cerebrovascular disease
Hx of peripheral arterial disease
Hx of renal failure
Aerobic fitness
22
Q

Pre-op assessment

A
  • systems review, especially CVS and resp, + endocrine, haem and neuro
  • ANY possibility of pregnancy
  • period of starvation, and assess reflux risk
  • meds, ALLERGIES
  • PMHx - for airway problems or spinal abnormalities if regional block
  • past anaesthetic hx - airway, drug used, side effects
  • FHx
  • SHx - smoking (recent –> higher risk bronchospasm + more mucus), alcohol (tolerance to sedation, increase risk to patient, risk delirium tremens)

+ confirm reasons for surgery - informed consent and proposed site confirmed

23
Q

ASA grading

A

1 – normal healthy patient
2 – mild systemic disease
3 – severe systemic disease
4 – severe systemic disease which is a constant threat to life
5 – moribund patient who is not expected to survive with or without the operation
6 – declared brain-dead, organs removed for donor purposes

24
Q

Reflux

A

2 hours clear fluids - water has half life of 10-20 mins

6 hours solids (if normal peristalsis!)

  • emptying rate is fastest for carbohydrates, then proteins, slowest for fats
  • milk should be regarded as a solid (will thicken and congeal in the stomach)
  • trauma and shock can cause delayed gastric emptying, so allow more time!
25
Q

Pharmacological control of reflux

A

PPI - 90 mins pre anaesthesia

  • lansoprazole, omeprazole
  • inhibit H+/K+ ATPase on parietal cells, so preventing excretion of H+ and reducing gastric juice volume

H2 antagonist - 90 mins pre anaesthesia

  • ranitidine
  • competitively blocks histaminergic H2 receptors and inhibit acid secretion by gastric parietal cells

Antacid - immediately before

Prokinetic - 90 mins prior, unreliable

26
Q

Risk factors for gastric reflux

A 
Obesity
Pregnancy
Hiatus hernia
Oesophageal stricture
Drugs lowering LOS pressure eg anticholinergics, opioids, ethanol
27
Q

Perioperative risk factors for thrombosis

A 
Hypercoagulability - surgery, cancer, oestrogen therapy, puerperium
Immobility
Dehydration
Poor CO
Obstructed venous return 
Age >60
Previous DVT, PE, thrombophilia
Recent CVS event
Acute medical illness/infection
Trauma
28
Q

Virchow’s triad

A

For thrombosis:
Hypercoagulability
Vessel wall injury
Venous stasis

29
Q

Diabetes control perioperatively

A

(all major surgery and critical illness affects glucose metabolism)
Stop all hypoglycaemics (metformin irrelevant)
Try not to stop insulin - eg maybe give half dose of long-acting insulin the night before, or treat with variable rate infusion - as risk of ketosis

30
Q

Opioids

A

If giving IV boluses, always ensure availability of naloxone and bag-valve-mask
Avoid post-op in day cases
Morphine 0.1-0.2mg/kg in adults, much less in elderly, titrate against response. Slow onset, peak effect 10-15 mins IV, so give small doses regularly (eg 2mg/5mins)
Fentanyl rapid onset of action, so give eg morphine before effects wear off.

Adjuncts to improve quality of analgesia and reduce requirements - NSAIDs, COX2 inhibitors, paracetamol - usually diclofenac suppository (CONSENT FIRST)

31
Q

Post-operative nausea and vomiting

A

25-30% after a GA
Caused by opioid anaesthesia, hypotension, dehydration, hypoxia, delayed return of GI function

Manage - ensure normal NEWS and hydration, adequate but not excessive analgesia, look for surgical cause, then give antiemetic (if one tried unsuccessful then try other class)

32
Q

Anti-emetics

A

5HT3 antagonists

  • effective, minimal side effects, can be given IV and rapid onset – good rescue remedy
  • ondansetron is most commonly used (4mg IV)

Dexamethasone

  • effective, long-half life, slow onset
  • best for prophylaxis

H1 antagonists

  • effective, but anticholinergic side effects, can cause tachyarrhythmias – give by slow IV and monitor ECG
  • cyclizine 50mg IV

Dopamine (D2) antagonists

  • slow onset of action, given IM
  • prochlorperazine (metoclopramide ineffective)
33
Q

Anaesthesia triad

A

ANALGESIA, hypnosis, muscle relaxation

34
Q

Fentanyl

A
  • Most common intraoperative opioid (synthetic) - better than morphine as rapid effects so reversible. Morphine only used after fentanyl induction.
  • 100x more potent than morphine

Administration

  • Bolus dose at induction of 1-3 micrograms/kg (before IV induction agent, also reduces laryngoscopy response)
  • Repeated doses if above 15-30 mins surgery
Unwanted effects
- Bradycardia
- Hypotension
- Respiratory depression
\+ maybe PONV, urinary retention, constipation, itching
35
Q

Can only discharge from recovery to ward when…

A
  • Fully conscious, maintaining own airway
  • Breathing and oxygenation satisfactory
  • Stable CVS
  • Pain and PONV adequately controlled
  • Temperature within acceptable limits
  • IV cannulae patent and flushed if necessary
  • All surgical drains and catheters checked

May also need ward visit by anaesthetist - if ASA III-V, epidural or PCA running, central venous line in, complicated intraoperatively

36
Q

Post-operative hypotension

A

Common in sick and elderly

  • Hypovolaemia - elevate legs, give fluid, assess for bleeding, take FBC
  • Arrhythmias - measure BP and perfusion, record ECG, correct electrolytes, treat
  • Left ventricular failure - oxygen, fluid restrict, diuretics, inotropic support
  • Septic shock - IV fluids, CVP monitoring, inotropic support, HDU/ICU, abx, look for surgical cause
37
Q

Post-operative hypoxia causes

A
  • Atelectasis
  • Pain
  • Chest infection
  • Pulmonary oedema
  • Aspiration
  • Pneumothorax
  • PE
  • Pleural effusion
  • ARDS
38
Q

Indications for intubation rather than LMA

A

Patient factors

  • severe reflux
  • recently eaten (emergency surgery) -> rapid sequence induction
  • obesity

Surgical factors

  • long surgery (>2-4hrs)
  • abdo/thoracic surgery where pressure on diaphragm
  • positioning unusual (eg neuro, where sitting upright, or if need face down)
  • if need to closely control ventilation and ensure no leak (eg neuro, where may need to increase CO2 to reduce bleeding in brain)
39
Q

Local anaesthetics

A

Lidocaine – less toxicity, quickest (2% = 20mg/ml. 3mg/kg is max dose, or 7mg/kg with adrenaline)

Bupivicaine – more toxicity (heart – broad QRS tachycardia, brain – tingling, fits, death), longer lasting

Chirocaine (levobupivacaine) – less cardiac toxicity but longer lasting

40
Q

Airway interventions

A
  • 100% O2 by reservoir bag
  • Chin lift/jaw thrust
  • Guedel or nasopharyngeal airway
  • Suction
41
Q

Breathing interventions

A
  • If RR = 0 – basic life support
  • If RR<5 – consider naloxone
  • If RR>25 – sit up, monitor SaO2, take ABG
  • Early intubation to treat respiratory acidosis

Resp rate is the most sensitive sign of a critically ill patient!

42
Q

Circulation interventions

A
  • HR + BP
  • Cap refill, peripheries
  • Large bore IV access – FBC, coagulation screen, biochem screen, ABG + lactate, cultures
  • 12 lead ECG
  • Fluid challenge if shocked – 500ml Hartmann’s, Ringers lactate or colloid
43
Q

Disability interventions

A 
- If GCS<8 or non-response to voice
o	Recovery position
o	100% O2
o	Check airway patent
o	Blood glucose 
o	Full neuro assessment
  • Also red flag if sudden fall in level of consciousness
44
Q

WHO surgical safety checklist

A

 Sign in before start of anaesthesia
 Time out before start of surgery
 Sign out at end of surgery

  • Correct patient
  • Correct operation
  • Correct site and side
  • Check consent form
    + allergies, metalwork, when last ate/drank, medical records available, surgeon available and ready, blood glucose control if diabetic

4th year (11 decks)

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