Peri-operative anaesthetic/ critical care Flashcards
(118 cards)
1
Q
Anaesthetic concerns re aortic stenosis
A
Pt has a fixed CO with a limited coronary blood supply. If after load is decreased (e.g. anaesthetic/ blood loss), cannot compensate
2
Q
How to calculate coronary perfusion pressure
A
Coronary PP = diastolic arterial pressure - LVED pressure
3
Q
Aortic stenosis examination signs re pulse and heart sounds
A
Pulsus alternans (alternating strong and weak beats with reg. rhythm)
Narrow pulse pressure (aka low SBP due to obstruction but maintained DBP)
Ejection systolic murmur (2nd ICS, R sternal edge)
Paradoxical splitting of S2 heart sound (aortic and pulm closure heard separately on expiration)
4
Q
Symptoms of aortic stenosis
A
Angina
SOB
Syncope/ pre-syncope
PND/ orthopnoea
5
Q
What should be given to preoperative patients with aortic stenosis?
A
Prophylactic abx for infective endocarditis
6
Q
Definition of preoperative hypothermia
A
Core temp <36 under GA
7
Q
How to measure core temp
A
Rectal
TM
Oral
Axillary
Oesophageal
8
Q
Risks/ contributors for perioperative hypothermia
A
Blood loss/ massive transfusion
Major surgery
GA - reduced hypothalamic function/ muscle activity/ metabolic heat/ shivering
Increased heat loss - evaporation, radiation to cold objects, exposure
9
Q
IVF recommended in diabetics periop
A
0.45% NACL
+ 5% dextrose
+ KCL (0.3 or 0.15%)
10
Q
Target BMs in diabetic during operation, and how often to check
A
Target = 6-10
Check hourly
11
Q
How to manage patient on warfarin pre-op
A
Low risk - stop 5 days before
High risk - stop 4 days before and bridge with LMWH (Rx dose)
- Stop LMWH 12-18hrs pre op + restart 6 hours postop
- finally stop bridging LMWH when INR therapeutic range again
Both:
-Aim INR <1.4 pre surgery
-Restart warfarin when oral fluids tolerated
12
Q
What surgical prep to use in
1) iodine allergy
2) MRSA
A
Chlorhexidine for both
13
Q
Whiter the 2 main skin prep solutions
A
Chlorhexidine gluconate
Povidone iodine (use with alcohol)
14
Q
What does NCEPOD stand for?
A
National Confidential Enquiry into Patient Outcome + Death intervention classification
15
Q
1% lidocaine - how many mgs/ ml
A
100mg/ 10ml
aka 10mg/ml
16
Q
Max dose of lidocaine
A
3mg/kg
7 if adrenaline
17
Q
Levobupivicaine max dose
A
2mg/kg (with/ without adrenaline)
MAX DOSE = 175mg
18
Q
prilocaine max dose
A
6mg/kg
9 with adrenaline
19
Q
Synthetic absorbable sutures - ?braided, + uses
A
Vicryl (polyglactin)
- braided
- skin / GI closure
PDS (polydiaxanone)
- mono
-mass abode wall closure
Monocryl (polyglecaprone)
- mono
- subcuticular/ fascia
20
Q
Non-absorbable sutures - ?braided, + uses
A
Silk
- natural braided
- drains
Prolene (polypropylene)
- Mono
-vascular anastomoses
Nylon/ Ethilon
- mono
- skin, eyes, nerves
Polyester
- braided
- anchoring
21
Q
What are Langer’s lines + what is their relevance in skin incision
A
Skin tension lines - correspond to natural orientation of collagen fibres in the dermis
Usually parallel to underling muscle fibres
Relevance - should aim to make small skin incisions along Langer’s lines
22
Q
What are the ratios of elliptical incision for mole removal
A
2mm margins - then x3 length wise
23
Q
How and why to pack an abscess wound
A
Why - to allow healing by 2y intention with granulation tissue
How - saline wick (then change to alginate after 24hrs) or alginate dressing. Change daily
**Alginate dressings are absorbent and promote autolytic debridement, HOWEVER shouldn’t be used in heavy bleeding/ friable tumours/ outwith wound edges as can clot + stick/ cause maceration
24
Q
How long can an abscess wound take to heal by 2y intention
A
8 weeks
25
Causes of renal failure/ anuria
Pre renal: hypovolemia
Dehydration/ burns / sepsis
Renal: GN, drugs, contrast, ATN
Post-renal: stones/ obstruction
26
If catheter inserted by not draining - what to do?
Reassess - feel bladder/ bladder scan
Aspirate
Suprapubic pressure
DO NOT FLUSH UNTILL URINE SEEN
27
What's the 'safe triangle' for chest drain insertion + ideal position
Post - Mid axillary line
Ant - pec major (lat border)
Inferior - 5th IC space
Ideally just infant of MAL to avoid long thoracic nerve.
Over superior aspect of inf rib to avoid intercostals NV bundle
28
Patient positioning for chest drain
30 degrees
Arm behind head
Regular obs monitoring
29
Size of surgical chest drain
24-30 Fr
30
How to fix chest drain in situ
1) silk stay suture
2) put in horizontal mattress for closure but leave untied - can cover with clear dressing
31
Chest drain insertion steps
1) Prep/ LA
2) incise (sup border inf rib, upwards direction)
3)blunt dissect with clamp
4) finger sweep
5)push tube in with clamp (after withdrawing central trochar)
6) attach to underwater seal and fix in place
32
Direction of chest tube into chest
Haemothorax - aim down
Pneumothorax - aim up to apex
33
Indications for contacting thoracic surgeons after chest drain insertion
-Persistent pneumo - ? bronchial tear
-Haemothorax
>1500 blood immediately evacuated
-Persistent bleeding >150ml/hr for 2-4hrs
-Persistent need for transfusion
34
At what rate should ventilation breaths be given (ATLS situation)
8-10/ min (every 6-8 secs)
35
Where are surgical airways inserted
Cricothyroidotomy - cricothyroid membrane through median cricothyroid ligament
Trachy - 2nd- 5th tracheal rings
36
Treatment options for rhabdomyolysis (2)
IVF
Mannitol
37
Risks of abdominal operation on a pregnant lady?
IUFD
Pre-term labour
DVT
38
How does pregnancy decrease BP/ cardiac output
Compression of IVC > decreased venous return to heart (preload) > decreased cardiac output
39
Define preload
End diastolic volume aka the stretch of the heart after filling in diastole
40
Define shock
Circulatory failure resulting in inadequate organ perfusion
41
What is the body response to decreased BP
Reduced preload > reduced CO/ BP > autonomic response:
Baroreceptor reflex (symp) = increased HR/ SV/ PVR - to inc CO + maintain BP
Homeones (Adrenal):
-Catecholamines = increased PVR
-Mineralocorticoids = salt + water retention
42
What are baroreceptors
Mechanoreceptors in carotid sinus + aortic arch
Sense arterial wall pressure change
43
What is baroreceptor nerve supply
Nerve of Herring (by CN 9 - glossopharyngeal)
44
How is BP regulated by standing up?
1) blood pools in legs
2) > decreased venous return to heart > decreased CO > decreased BP
3)a) baroreceptors sense + cause vasoconstriction (inc PVR)
3)b) Sympathetics - tachycardia + increased contractility
45
how to improve preload (interventions)
IVF
Inotropes/ vasopressors
46
inotropes vs vasopressor action
what situations should each be used
inotrope (e.g norad/ dobutamine) - increase heart contractility (via HR and SV) + PVR
- acts on myocardium
- use in cariogenic shock (e.g. after MI)
vasopressors (e.g. metaraminol) - Raise BP by increasing PVR
- acts on vascular smooth muscle
- use in septic shock to decrease widespread vasodilation
47
What nerve fibres is pain transmitted through
fast A-delta (sharp) + slow C fibres (dull) via spinothalamic tract to thalamus
48
Normal dose of morphine in a PCA bolus
0.5-2mg
49
Complications of pain
Resp: atelectasis/ infection
GI: delayed gastric emptying/ bowel movement, ileus
CVS: Inc HR/BP > MI
Rehab: immobility, DVT, psych
50
Mechanism of action of paracetamol
Prostaglandin synthesis inhibitor + ? element of COX2 inhibitor
51
What enzyme converts codeine to morphine in liver - how can this differ in people
cytochrome P450 (CYP2D6)
- high levels - rapid intoxication
- low levels - no effect of codeine
52
Management of paracetamol overdose
within 60mins: gastric lavage
within 30min - 2hrs: activated charcoal
N-acetyl cysteine (NAC) - replenishes glutathione antidote
Monitor liver function - may need transplant
53
What is Starling's law of contractility?
Increased stretch of myocardium > increased contractility
(to a point where it then becomes diminished if stretched too much)
54
What is the purpose of a fluid challenge/ how does it differ to just speeding up fluids?
Fluid challenge is also diagnostic, testing the pts CV response to fluids. Rapid fluid administration stretches LV and should increase CO as per Starling's law
Speeding up fluids will also rehydrate pt, but will not cause a rapid stretch of the LV to give insight to pt response.
55
What is the effect of surgery/ trauma on adrenal hormones - ACTH/cortisol/ aldosterone/ sex hormones
ACTH - increased
Cortisol + aldosterone increased
Sex hormones decreased
56
What is the effect of surgery/ trauma on TSH
should be unchaged
57
What is the effect of surgery/ trauma on renin/ ADH
increased
58
What is the effect of surgery/ trauma on insulin + glucagon
Insulin - decreased
Glucagon - increased
59
Where is ADH produced and released
Produced - hypothaamus
Released - post pituitary
60
How does a high epidural cause bradycardia/ hypotension
How to fix
Blocking of symp fibres at T1-5 -> unopposed p'symp action of vagus
Distributive shock (vasodilation)
Stop injection
Sit upright
O2
Inotropes/ atropine if req
61
How may epidural cause desaturation
Paralysis of intercostals/ diaphragm
Haemothorax/ pneumothorax during insertion
62
Which epidural levels for different surgeries:
Upper abdo
GU
Vaginal birth/ hip
Thigh/ leg
Foot/ ankle
Perineal/ anal
Upper abdo - T4
GU - T6
Vaginal birth/ hip - T10
Thigh/ leg - L1
Foot/ ankle - L2
Perineal/ anal - S2-5
63
How to test level of epidural bock
Temperature sensation (ice) - as spinothalamic is 1st to be affected, motor fibres last
64
Epidural block vs hypovolemic shock
Epidural = bradycardia, warm peripheries (psymp action of bradycardia + vasodilation)
Hypovolemia = cold clammy peripheries + tachy
65
Systemic effects of epidural
Hypotension + reduced cardiac output (peripheral vasodilation)
Bradycardia
Bradypnoea/ reduced ventilation
66
What are the 2 ways in which ADH increases water resorption from kidneys
1) In collecting duct - increases aquaporin channels - increases resorption of solute free water
2) also stimulates NaCl reabsorption in asc loop. Water then follows due to creation of osmotic gradient (between tubule + renal medulla)
67
Where is the main site of action of ADH/ vasopressin
Collecting duct
68
Describe the counter current multiplier mechanism of the kidney loop of Henle
Desc loop - permeable to water only, excreted into renal medullary space due to osmotic gradient created by asc loop, filtrate is hypertonic
Asc loop - impermeable to water, salt actively transported itself. This draws further water out of desc loop via osmotic gradient
These both stimulate each other to efficiently concentrate urine over short distance/ minimal energy spent.
69
What is Conn's syndrome (+ effect on electrolytes)
Primary hyPER aldosteronism
Serum:
Na - high (+HTN)
K - low
H - low (alkalosis)
70
Where does aldosterone act on kidney tubules
DCT/CD
71
Effects of aldosterone on kidney tubules
Increases Na channels (+Na/K ATPase channels)
- increased Na resorption
- water follows Na as long as ADH present (>raised BP)
- excretion of K+
- indirect excretion of H+ (>alkalosis)
72
Actions of angiotensin 2
Increase water resorption:
-Stimulate aldosterone release from adrenal
- Direct Increase Na resorption in kidney
- decrease GFR by contracting mesangial cells
Vasoconstriction:
-Directly
- Increased noradrenaline release by sympathetic stimulation
Acts on brain:
- increased release of ADH and ACTH
- decreased baroreceptor sensitivity
73
Small vs large bowel obstruction signs on XR
Small = place circulars extend full way of bowel
Large = haustra only go part of way through bowel
74
Complications of enteral feeding
Tube:
Kink, displacement, blockage, infection
Feed:
N/V/D, Aspiration, Refeeding syndrome, deranged LFTs, electrolyte imbalance
75
What is refeeding syndrome?
Metabolic disturbance after starvation (where insulin levels low and electrolyte stores depleted)
Introduction of carbs causes rapid cellular uptake of PO4/K+/Mg + insulin release.
>>> Hypokalaemia/ hypomagnesemia/ hypophosphatemia
Hypo or hyper glycemic
76
How to avoid referring syndrome
Daily bloods
Increase food slowly over 4-7 days (start around 10cal/kg/day)
Supplements:
- Oral thiamine - avoid Wernicke's encephalopathy
- K/Mg/PO4
77
What is Wernicke's encephalopathy + triad of sx
Neurological emergency resulting from acute vitamin B1 (thiamine) deficiency - which acts on brain for metabolism etc
Causes: malnourishment, alcoholism, refeeding syndrome
Triad: ophthalmoplegia, ataxia, confusion
78
Indications for TPN
Gut reasons:
Short bowel syndrome
Obstruction
IBD
EC fistula - gut rest
Radiation enteritis
Critical illness:
Severe malnutrition (>10%wl)
Polytrauma
Sepsis + MOF
Severe burns
79
Routes for TPN
PICC/ central line - because of high osmolarity
80
Electrolytes + components given in TPN
Na
Mg
K
Ca
Carbs, fat, proteins, vitamins, nitrogen
81
Complications of TPN
Refeeding syndrome
Gut atrophy
Electrolyte imbalance (hyperchloremic metabolic acidosis if Cl excess)
Fluid overload/ over feeding
Irregular blood sugars (hypo/hyper)
Ventilatory problems if ventilated - related to glucose
Hyperlipidemia/ hyperammoniemia
82
Why must fat/ protein also be used as energy source and not solely glucose in critically ill pts (in TPN)
Fatty liver
Resp failure - increased ventilation requirements due to extra CO2 released on glucose oxidation
Glucose intolerance of critical ill pts (poor utilisation due to stress response)
83
Management of fast AF
1) rate control (B blocker)
- or dig/ verapamil/ amiodarone
2)rhythm control (cardioversion) - amiodarone
- if <48hrs
3)Anticoagulant - assess risk with CHAD2VAS score
**If adverse features -> DC cardioversion
84
Management of atrial flutter and SVT
atrial flutter - beta blocker
SVT - vagal manouvers/ adenosine
**If adverse features -> DC cardioversion (+amiodarone)
85
Define perioperative hypothermia
Under anaesthesia = core temp of 36 degrees or less
86
Causes / risk factors for intraoperative hypothermia
Major exposed surgery - evaporation/ radiation
Blood loss/ massive transfusion
Anaesthetic agents
87
Complications of hypothermia intraoperatively
coagulopathy/ reduced plts (left shift of o2 dissoc curve)
arrythmia
Hypoperfusion of everything - cerebral, myocardium, renal
metabolic disturbance
88
Define DIC
Pathological activation of coagulation + fibrinolytic systems > formation of micro thrombi > exhaustion of factors/ plts > bleeding
89
Causes of DIC
Sepsis/ widespread endothelial injury/ hypothermia/ haemorrhage
-> release of tissue factor + activation of coal cascade
90
Treatment of DIC
FFP
Plts
Cryoprecipitates
91
Shelf life of platelets
5 days
92
Stages of haemostasis
1) vasoconstriction
2) put activation - adherence + plug
3) Coagulation - activation of coal cascade
93
which factors are deficient in stored blood
5 + 8
94
Define a massive transfusion
>50%of pts circulating volume in 12-24hrs
95
Complications of massive transfusion
TACO
TRALI /ARDS
Hypothermia
Hyperkaemia
Hypocalcemia
Coagulopathy - loss of factors 5 and 8
Thrombocytopenia - no plts in PRCs
Organ failure
96
What coag pathways are measured by:
PT
APTT
TT
PT = extrinsic + common
APTT = intrinsic + common
Thrombin time = fibrin -> fibrinogen (common only)
97
Indications for central line
TPN
Haemodialysis
TV cardiac pacing
Strict fluid balance monitoring
Failed peripheral access
98
Central line complications
Thrombus/ air emboli
Infection
Blockage
Injury during insertion - artery/ RA/ pneumothorax/ thoracic duct (chylothorax)
99
How to insert central line
Location: Triangle between 2 heads SCM + clavicle, lateral to carotid pulse (IJV)
Insert under US guidance
Insert needle at 30 degree angle down. Aspirate as advancing to get blood.
Seldinger technique
Suture
XR to confirm place + no pneumothorax
100
What position to remove central line + why
head down to avoid air embolism
101
Main organism causing infection in central line
Staph epidermidis
102
Why would a pt be oliguric post-op
Physiological stress response to surgery - increased glucocorticoids/ mineralocorticoids -> water and salt retention
Anaesthetics can stimulate vasopressin
Sepsis/ dehydration etc
103
How is CO2 transported in blood
Free dissolved
Bound to bicarb (70%)
Bound to carbaminohaemoglobin
104
What enzyme converts H20 + CO2 to carbonic acid
carbonic anhydrase
105
What is the chloride shift of an RBC
Cl- moved into cell as HCO3- moves out into plasma to keep balance
106
How does compensation occur for respiratory acidosis
1) Mins - Hrs: slight elevation of plasma bicarb
2) Days: renal compensation by excretion of carbonic acid + increased bicarb absorption
107
T1 and T2 resp failure causes
1= VQ mismatch: pneumonia, pneumothorax, PE, bronchitis
2= Inadequate alveolar ventilation: airway resistance, reduced resp effort, neuromuscular, deformed chest, decreased area for gas exchange (chronic bronchitis/ emphysema)
108
How does morphine cause resp depression
Binds to Mu receptors in resp centre
109
Naloxone dose
0.4-2mg IV bolus,
repeat 2-3 mins if no response to max dose 10mg
110
Action of K+ on cardiac muscle
Depolarises RMP > decrease action potential/ contraction > dilated flaccid heart with reduced HR/ contractility
111
ECG changes of hypo/hyperkalemia
Both: wide QRS
Hyper: tall T waves, flat P wave, long PR interval
Hypo: flat T wave, U wave (extra small wave between T + P)
112
Manifestations of hyperkalemia
GI: N/V/D
MSK: cramps/ weakness/ paralysis
CV: arrhythmia,death, hypotension
113
Management of hypokalemia
Ca gluconate - cardioprotective (bolus over 10 min)
Insulin dextrose - increase cellular uptake of K
Soda bic/ salbutamol/ dialysis
114
Effect of TURP syndrome on electrolytes/ how?
Glyceine absorbed > dilution hypotonic hypervolemia > dilution HYPONATREMIA
Can also cause raised ammonia as glycerine broken down to ammonia in liver
115
Management of TURP syndrome
Osmotic diuretic (mannitol) - to excrete water but conserve sodium
(can also use furosemide - loop)
116
Where/ how do loop/ thiazide diuretics work
Loop (furosemide): thick asc loop - inhibits Na/K/Cl cotransporter (aka reabsorption of these)
- excretion of Na and water follows (H+ and Cl also drop)
Thiazide - DCT - inhibits Na/ Cl symporter (increased excretion + water follows)
117
Where does spironolactone work
Collecting tubule
118
ECG finding of hypothermia
J wave - 2nd peak after QRS
Assoc with temp <32
