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Anaesthesiology > GIT > Flashcards

GIT Flashcards

1
Q

How much of the cardiac output do the kidneys receive?

A

25%

cortex 66%, medulla 33%

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2
Q

How is the RAAS system stimulated?

A

• Decreased renal blood flow
• cause decreased chloride
• stimulate juxtaglomerular apparatus to stimulate RAAS and sympathetic system

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3
Q

Name 4 general effects of anaesthesia on renal function

A

• Decreased GFR as cardiac output decreases (by induction agents and volatiles)
• autoregulation remain intact
• surgical stress response: increased adh- concentrated urine
• IPPV (intermittent positive pressure ventilation) increase atrial pressure which decrease ANP. Therefore decreased sodium excretion

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4
Q

Sevoflurane effect on kidneys?

A

• Potentially nephrotoxic as produce free fluoride ions when metabolised in liver
• produce nephrotoxic metabolite compound A when degraded (rare)

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5
Q

Name 9 factors that increase risk perioperative renal failure

A

• Co-existing renal disease
• hypovolaemia
• liver cirrhosis
• sepsis
• multi organ trauma
• congestive cardiac failure
• abdominal aneurysm resection
• cardio pulmonary bypass
• advanced age (limited reserve)

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6
Q

Name 10 clinical issues that chronic renal failure patients have that may make anaesthesia difficult

A

• Anaemia: due to decreased erythropoietin. Cause increase co and OHEC shift to right due to metabolic acidosis (good thing)
• pruritis:sign of end stage disease with increased histamine.
• coagulopathy: defective platelet function, defective vWF
• altered hydration and electrolyte balance: unpredictable volume status. Easy to overload but hypovolaemic after dialysis. Hyper k > 5.5, hypo Ca due to decrease GFR (increase phosphate) causing renal osteodystrophy and decreased 1,25 DHCC production (decrease intestinal absorption ), hyper mg due to antacids (cause cns depression, potentiate muscle relaxants)
• metabolic acidosis: decreased h excretion . cause compensatory hyperventilation,decreased neuromuscular responsiveness
• systemic ht:cause fluid overload
• increased susceptibility to infections: decreased phagocytes, immunosuppressants, frequent transfusions
• pericardial disease: effusion, tamponade due to uremia
• CNS: encephalopathy, seizures (brain oedema)
• PNS: distal symmetric mixed polyneuropathy (median, peroneal)
• ans: resting tachy, attenuated response to hypovolaemia ippv, orthostatic hypotension, delayed gastric empty ( risk aspiration)

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7
Q

Define disequilibrium syndrome

A

CNS symptoms post dialysis due to more rapid lowering of extracelular osmolarity than intracellular in renal failure patients

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8
Q

Treatment hyperkalaemia? (3)

A

• Hyperventilation
• insulin and glucose
• cacl2 (physiological antagonist)

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9
Q

Name 7 indications pre-op dialysis in renal failure

A

• fluid overload
• hyper K
• metabolic acidosis
• pericarditis
• coagulopathy
• Drug toxicity
• refractory git symptoms

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10
Q

When transfuse chronic renal failure patients?

A

Only if Hb <6 or extensive surgery with high risk blood loss.
Very prone to fluid overload!

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11
Q

How should induction of anaesthesia be performed in chronic renal failure? (6)

A

• Pre-oxygenate
• careful fluid load especially after dialysis
• give lower dose induction agent (increased free fraction due to hypoalbuminaemia and acidosis )
• ketamine useful.
. RSI : due to delayed gastric emptying and vomiting due to uraemia. sux safe if k<5,5 otherwise do modified RSI with atracurium
• avoid steroid relaxants: dependent on renal excretion. Will accumulate. Risk recurarisization after reversal and weak post op

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12
Q

How should maintenance of anaesthesia be performed in chronic renal failure? (2)

A

• Safe vapours = isoflurane and desflurane
• narcotics opioids: use only short acting, lower doses eg remitentanil. Not morphine! Will accumulate

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13
Q

Which vapours are avoided in chronic renal failure patients and why? (4)

A

• Enflurane: organic fluoride production
• sevo = compound A
• halothane = dysrhythmias
• nitrous = decreased oxygen delivery in severe anaemia

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14
Q

Treatment ascites? (4)

A

• Restrict Na to <90 ekw/d
• spironolactone and furosemide
• paracentesis with or without iv albumin 6-8g/L
. Refractory: leveen shunt

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15
Q

Name 8 git complications and pathophysiological changes due to chronic liver disease

A

• Portal ht >10 mm hg
• gastro-oesophageal varices: cause massive bleeding, haemorrhoids.
• spontaneous bacterial peritonitis: cause low protein ascites
• increased risk aspiration: severe nausea and vomiting, delayed gastric emptying, abdominal distension, regurgitation
• gallstones, cholangitis
• duodenal ulcers
• ascites: hyper aldosteronism, increase adh, abnormal sodium retention, increase catecholamines, insensitive to circulating ANP
• hepatorenal syndrome:doesn’t respond to fluid resuscitation

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16
Q

Name 6 CVS and haematological changes caused by chronic liver disease

A

• anemia (megaloblastic). From GIT bleeding and/or malnutrition
• Thrombocytopenia, leukopenia: congestive splenomegaly
• homeostatic failure: bleeding risk
• increased cardiac output with hyper dynamic circulation → heart failure (late stage)
• coagulopathy: decreased synthesis clotting factors and metabolism of vitamin K
A systemic anteriovenous shunts with reduced peripheral resistance
• cardio myopathy presenting as CCF, seen in alcoholic cirrhosis
• porto-pulmonary syndrome: right ventricular failure secondary to severe portal and pulmonary ht

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17
Q

Name 8 metabolic/immunity complications of chronic liver failure

A

• Hypoglycaemia: secondary to depletion glycogen stores, impaired gluconeogenesis
• hypo na, hypo K (dilutional): aggravated by vomiting, diarrhoea, diuretics
• hypo-albuminaemia:reduced synthesis
• metabolic acidosis: lactate accumulation
• encephalophy: ammonia accumulation
• decreased pseudocholinesterase production
• altered drug metabolism: lower albumin to bind drugs
• impaired host defense mechanisms

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18
Q

Treatment hepatic encephalopathy? (5)

A

Initially reversible…
• restrict dietary protein and avoid precipitating factors
• oral lactulose.
• neomycin or metronidazole to sterilise gut
• flumazanil
• liver transplant is only true cure

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19
Q

Preoperative anaesthetic management of chronic liver disease patients ? (5)

A

• Correct coagulopathy with iv vit k
• haematocrit must be > 30%, INR ≤1,4 , platelets >100
• correct intravascular fluid deficiencies with colloids preferably
• paracentesis for tense ascites
• correct hypoglycaemia
NB aspiration prophylaxis

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20
Q

Premedication of chronic liver disease patients ? (2)

A

• avoid sedatives!
• aspiration prophylaxis nb

Can’t give steroid muscle relaxants, paracetamol, NSAID, halothane.

21
Q

When may regional anaesthesia be performed in chronic liver disease?

A

If no coagulopathy. Avoid hypotension.
Preferred

22
Q

Which volatile agent best maintains hepatic blood flow?

A

Isoflurane

23
Q

How should induction agents be administered in chronic liver disease?

A

Lower dose due to decreased protein binding

24
Q

How should the airway be managed intra-op in chronic liver disease and with which agent?

A

RSI! With modified atracarium
Decreased pseudocholine esterase in these patients so sux not the best drug (last long)
Avoid steroid muscle relaxants- they can’t metabolise them.

25
Q

Which volatile is contraindicated in chronic liver disease

A

Halothane: halothane hepatitis

26
Q

Treatment low urine output intra-op in chronic liver disease

A

Iv mannitol or low dose dopamine

27
Q

Name 2 special considerations to be made when performing blood transfusion in chronic liver disease

A

•Citrate toxicity (metabolic alkalosis)
• will need calcium replacement

28
Q

How should chronic liver disease patients be managed post op and what are some common complications (5)

A

• expect prolonged emergence
• only extubate when awake to reduce risk aspiration
• hepatic dysfunction common
•Increased morbidity due to sepsis, bleed, poor wound heal, renal failure, encephalopathy
• increased risk post op pulmonary oedema, atelectasis, pneumonia

29
Q

Which type of anaesthesia is preferred in obese patients?

A

Regional techniques to avoid difficult airway
If Ga required, must intubate.

30
Q

Why are renal failure patients at high risk of bleeding?

A

Platelet dysfunction due to elevated urea

31
Q

Why are liver failure patients at increased risk of bleeding? (3)

A

Decrease clotting factor production
Protein C and S deficiency
Decreased vitamin K stores

32
Q

Name 6 drugs that are contraindicated in renal failure

A

Enflurane
Sevoflurane
Halothane
N2O
Long acting narcotics: morphine, Tramadol, pethidine
Steroid muscle relaxants: pancuronium, rocuronium (accumulate)
NSAIDS eg diclofenac (inhibit synthesis vasodilatory prostaglandins through lipoxygenase and arachidonic acid pathway. In pts with high angiotensin II and norepinephrine, attenuation of prostaglandin synth may cause AKI)

33
Q

Describe your choice of premedication for renal failure and why (2)

A

• Anti-aspiration: metoclopramide, antacids etc
• careful administration of iv fluid because can easily under or overload patients. Don’t use ringer’s in anuric patients (contain k)

34
Q

Describe your choice of induction and maintenance for renal failure and why (6)

A

• Must decrease dose of induction agents, propofol is fine or etomidate
• SYNTHETIC opioids for analgesia (don’t accumulate). NSAIDs contraindicated, regional or neuraxial can only be done if no coagulopathy and no severe metabolic acidosis (decrease seizure threshold for local)
. Preferred muscle relaxant atra or cisatracarium (not metabolised or excreted by kidney). Can only use sux if K <5,3. Nb to do RSI

• preferred volatile = isoflurane (sevo produce compound A in sodalime)
• ventilate with ippv and aim for normocapnia (hypercarbia → resp acidosis → worsen acidaemia → circulatory depression and hyperk)
• maintain stable haemodynamics to preserve renal perfusion (can consider “renal protective” drugs: mannitol, furosemide, dopamine low dose, fenoldopam)

35
Q

Name 7 intra-op considerations in obese people

A

• Regional technique preferred to avoid difficult airway (all types of airways difficult in these patients), but often difficult
• If must do ga, intubation preferred due to aspiration risk and difficulties ventilating at high pressures with LMA
• nb effective pre-oxygenation - shortened apnoea time
• difficult bp monitoring, may need invasive bp monitor
• do awake extubation
• limit opioid use- further respiratory depression
• ramped positioning often useful to help with intubation, airway obstruction and aspiration

36
Q

Minimum haemoglobin level for Surgery in renal failure patients?

A

Usually anemic so can tolerate hb 6 or higher. Cancel if lower than 6.

37
Q

Name 6 CVS changes in renal failure

A

• Hypertension severe and difficult to control
. Coronary artery disease
• congestive cardiac failure: extracellular fluid overload, sodium retention, increased demand due to anaemia and ht
• pericarditis
• pericardial effusion
• cerebrovascular disease (uremic encephalopathy)

38
Q

Name 2 respiratory changes in renal failure

A

•Pneumonitis
• pleural effusion

39
Q

Name 5 acid base and electrolytes changes in renal failure

A

• Metabolic acidosis
• hyperkalaemia!
• hypocalcaemia!
• hypermagnaesemia
• hyponatraemia

40
Q

Name 4 haematological changes in renal failure

A

• Normocytic, normochromic anaemia
• white blood cell or platelet dysfunction due to high urea
• uraemic coagulopathy
• hypoalbuminemia

41
Q

Name 3 gastrointestinal changes in renal failure

A

• Nausea and vomiting
• delayed gastric emptying due to autonomic neuropathy → risk aspiration
• gastric hyperacidity
Diabetes is leading cause of renal failure so often comorbid diabetes

42
Q

Name 2 neurological changes in renal failure

A

• uremic encephalopathy
• peripheral and autonomic neuropathy

43
Q

Name 3 musculoskeletal changes in renal failure

A

• Secondary and tertiary hyperparathyroidysm
• osteodystrophy
• pathological fractures (hypoCa)

44
Q

When should a spinal not be done in a renal failure patient? (Specific lab value)

A

Urea > 12 (platelet dysfunction therefore coagulopathy)

45
Q

Name 7 respiratory changes due to liver cirrhosis

A

• hyperventilation (respiratory alkalosis)
• hypoxaemia: ortodeoxia
• displaced diaphragm: atelectasis
• pleural effusions
• hepatic pulmonary syndrome: decreased pao2 due to intrapulmonary shunting
• decrease FRC, v/q mismatch
• recurrent pulmonary infections: bacterial pneumonia, lung abscess, aspiration pneumonia

46
Q

Name 4 cns changes due to liver cirrhosis

A

• Hepatic encephalopathy
• mental obtundation, asterixis , foetor hepaticus ( rotten breath)
• cerebral oedema
• raised intracranial pressure

47
Q

Name 3 renal changes due to liver cirrhosis

A

• Decreased renal perfusion and GFR
• toxic or ischaemic tubular necrosis
• hepatorenal syndrome: functional renal failure- grave prognosis

48
Q

Describe the Childs turcotte Pugh score for surgical risk in liver disease

A

• Encephalopathy: 1-3 (stuporous, comatose)
• ascites: 1-3 (marked)
• total bilirubin: 1 (<25) -3 (>40)
• albumin: 1 (>35) - 3 (<30)
• prothrombin time seconds prolonged: 1 (1-4) -3 (>6)

5-6 low surgical risk; 5% mortality
7-9 moderate risk; 10% mortality
10-13 high risk; > 50% mortality

49
Q

Devise a safe anaesthetic plan for chronic liver disease patients (4)

A

• Induce with propofol (best), but use lower dose - decreased protein binding. Sodium thiopentone and ketamine (only if hypotensive) also acceptable.
• RSI: sux (prolonged - decreased synthesis pseudocholinesterase) initial then maintain with atracurium or cisatracurium (will need higher dose).
• maintain: desflurane best (least liver metabolism), may also use sevo (next best but theoretically causes fluoride ion release, affecting renal function), then isoflurane
• opioids: remifentanil safest. Use synthetic only (sufentanil), caution with fentanyl and pethidine. Morphine contraindicated.

Neuraxial contraindicated in most cases due to coagulopathey

Anaesthesiology (24 decks)

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