Critical Care Flashcards
How is Abdominal Compartment syndrome diagnosed?
Presence of IAP>20 measured 3 times 1-6 hours apart or Abdominal Perfusion Pressure <60
and
new organ dysfunction
What are the causes of Abdominal Compartment Syndrome?
Increased intra-luminal contents
Increased intra-abdominal contents (e.g. fluid/blood/abscess)
Capillary leak/fluid resuscitation
Miscellaneous (hernia repair, obesity)
How is Intra-abdominal pressure measured? (technique and criteria)
Technique
-Empty bladder, then 25ml of saline introduced
-Connect catheter to pressure transducer
Criteria
- End-expiration
- Supine
- Zeroed to mid-axillary line
- Abdominal muscular contraction absent/paralysed
How is Intra-Abdominal Hypertension graded?
Grade 1 12-15
Grade 2 16-20
Grade 3 21-25
Grade 4 >25
What are the pathophysiological changes associated with abdominal compartment syndrome? (5 categories)
- Visceral - mucosal ischaemia
- Renal - impairment at 15, oliguria at 20, anuria at 30
- Pulmonary - splinting, decreased compliance/TVs, acidosis
- CVS - decreased CO,BP,SV, increased SVR, DVTs
- Cerebral - increased ICP, decreased CPP
What are risk factors for abdominal compartment syndrome?
Increased intra-luminal contents
Increased intra-abdominal contents
Capillary leak
Fluid resuscitation
Others (obesity, peritonitis, hernias)
What non-operative techniques should be used when abdominal compartment syndrome is suspected?
- Sedation
- Analgesia
- NM blockade
- Fluid optimisation
-NG/rectal decompression
What factors intraoperatively increase the risk of abdominal compartment syndrome?
Long operating time
Lots of fluids
Electrolyte abnormalities
Trauma triad
Closure under tension
How is Acute Kidney Injury defined? (3)
Within 48 hours
1) Rise of creatinine of ≥26
2) Rise of creatinine between 150-200% of normal
3) UO <0.5ml/kg/hr for >6 hours
What are the causes of Acute Kidney Injury?
Pre-renal - shock (haemorrhage, septic, distributive), ACS
Intra-renal - ATN (Hypotension), nephrotoxins, GN
Post-renal - Catheter problems, bilateral ureteral problems/injury
What factors lead to oliguria in the sick surgical patient ?
Stress response –> ADH, Cortisol –> retain water
Catecholamines –> renal vasoconstriction
Sepsis –> relative hypovolaemia and decreased renal perfusion
What are the stages of Acute Kidney Injury?
Stage 1 - Creat 1.5-2 x normal/ UO≤0.5 >6 hours
Stage 2 - Creat 2-3 x normal/ UO≤0.5 >12 hours
Stage 3- Creat >3 x normal/ UO≤0.3 >24 hours
How can pre-renal and intrinsic renal failure be differentiated?
Pre-renal –> sodium conservation and concentrated urine
Urinary sodium/osmolality
Prerenal - <20mmol/l Na and osmolality >500
Renal - >40mmol/l Na and osmolality <350
What are the priorities in treatment of Hyperkalaemia? (4)
1) Identification - tall T waves, broad QRS and absent P
2) Stabilise myocardium with 0.5ml/kg CaGluconate 10%
3) Reduce intravascular potassium - Insulin dextrose (10u in 50mls 50%) + Salbutamol nebs (10mg)
4) Offload Potassium - Calcium resonium, stop drugs, ?furosemide ?RRT
What are the main indications for renal replacement therapy? (5)
1) Refractory pulmonary oedema
2) Refractory hyperkalaemia
3) Refractory acidosis <7.1
4) Symptomatic uraemia (encephalopathy/pericarditis)
5) Poisoning
What are the differences between haemodialysis and haemofiltration?
Dialysis - solute diffusion - cheaper, easier
Filtration - solute convection/ultrafiltration - better BP control, larger molecules (e.g. lipids, large cytokines), more physiological
How is ARDS defined?
1) Acute onset
2) pulmonary oedema
3) hypoxaemia despite PEEP ≥5cmH20
4) not caused by cardiac failure
Berlin Criteria
How is the severity of ARDS graded?
Mild - PaO2/FiO2 ratio 200-300mmHg (26.6-40kPa)
Moderate - PaO2/FiO2 ratio 100-200mmHg (13.3-26.6kPa)
Severe - PaO2/FiO2 ratio <100mmHg (<13.3kPa)
What is lung compliance?
Change in lung volume for a unit rise in pressure
What are the physiological changes seen in ARDS?
Reduced resting lung volumes
Increased V/Q mismatch
Decreased compliance
Increased work of breathing
What is ventilator induced lung injury?
Direct damage to alveolar tissue
Barotrauma - macroscopic injuries
Volutrauma - >10-15ml/kg –> ARDS
Oxygen toxicity –> >50%FiO2 free radical toxicity
What are the causes of ARDS?
-Pulmonary (infection, contusion, aspiration, drowning, smoke)
-Indirect (sepsis, major trauma, burns, pancreatitis, fat/amnion/thrombotic embolism)
What pathological processes are seen in ARDS?
1 ) Diffuse alveolar damage (Hyperacute) with damage to type 1 pneumocytes > type 2 pneumocytes
2) Acute inflammatory response
3) Proliferative/fibrotic phase
What are the principles of management of ARDS (5)?
-Low tidal volume ventilation (6-8ml/kg)
-PEEP
-Fluid management
-Proning
-ECMO or HFOV
-Permissive hypercapnia/acidosis (until myocardial depression)
What are the options for surgical airway insertion?
Surgical cricothyroidotomy – clip + use 5-7mm ET tube
Scalpel Bougie technique
Needle cricothyroidotomy
What is Atrial fibrillation?
- Supraventricular tachcardia
- Uncoordinated atrial activity
- Irregularly irregular ventricular response if AV system intact
When should DCCV be considered for acute AF?
HR >150 with haemodynamic instability
What anti-arrhythmics can be used for AF?
Beta blockers esp where stopped prep
Amiodarone - central access only needs monitoring
Digoxin - less effective, more useful in chronic setting
What scoring systems might be used before starting anticoagulation for post operative AF?
HAS-BLED score (alcohol, meds, age, comorbidities)
CHA2DS2-VASc score >2 –> Anticoag
What are the goals of treatment for AF? (3)
Achieve ventricular rate control
Prevent thromboembolic events
Maintain sinus rhythm
When should anticoagulation be started after surgery?
Prophylaxis 6 hours
Treatment minor surgery 24 hours
Treatment major surgery 48-72 hours
What are the common congenital bleeding disorders?
- Haemophilia A (VIII - x linked –> Desmopressin/F8 concentrate)
- Haemophilia B (IX - x linked –> PCC /F9 concentrate)
- Von Willebrands disease (AD – linked to platelet activation –> Cryo/F8/Desmopressin)
What are the common acquired bleeding disorders?
- Vitamin K deficiency (II/VII/IX/X) from dietary, bile acid malabsorption, liver failure
- Liver Failure - decreased synthesis of clotting factors (Except F8 which is increased) and Vitamin K
- Platelet dysfunction - drugs, alcohol
- Thrombocytopenia - decreased production/survival DIC (also factor consumption)
- Renal failure
What are some common causes of AF?
PIRATES
Pulmonary Embolism
Ischaemia
Respiratory disease (pneumonia/atelectasis)
Atrial enlargement
Thyroid disease
Ethanol/Electrolytes
Sepsis/sleep apnoea
Also
-withheld drugs, hypovolaemia
What are the common acquired bleeding disorders?
Vitamin K deficiency (II/VII/IX/X) from dietary, bile acid malabsorption, liver failure
Liver Failure - decreased synthesis of clotting factors (Except F8 which is increased) and Vitamin K things
Platelet dysfunction - drugs, alcohol
Thromboyctopenia - decreased production/survival, DIC (also factor consumption)
Renal failure
What factors would make you suspicious of a hereditary thrombophilia?
History of recurrent VTE
History of idiopathic VTE (50%)
DVT <40
FH
Unusual site
What are the criteria for undertaking brainstem testing? (6)
- Evidence of irreversible brain damage of a known aetiology
- GCS 3 mechanically ventilated with apnea
- No sedation
- No muscle relaxation
- Normothermic
- Normal electrolytes/glucose
- Cardiovascularly stable
Who can undertake brainstem death testing? (4)
-Two medical practitioners registered > 5 years
-At least one consultant
-Not member of transplant team
-No clinical conflict of interest
What are the criteria for diagnosis of brainstem death?
Establishing absence of brainstem reflexes
1) General examination to exclude voluntary/involuntary movement
2) Pupils fixed and non responsive (II/III)
3) No corneal reflex (Va/VII)
4) No vestibulo-cochlear reflexes (caloric test III, VI, VIII)
5) No response to supraoribital pressure (VII/Vc)
6) No gag/cough reflex (IX/X)
Apnoea test
- Pre oxygenate patient for 10 minutes
- Allow PaCO2 to rise to 6.0 with SBP >90 (6.5 for COPD)
- Disconnect from Ventilator for 5 minutes
How would you define a major burn and what fluid resuscitation is generally indicated?
Adult >15% TBSA, Child >10% TBSA, partial/full thickness
Assess size - Lund/Browder chart or Wallace rule of 9s or palm measurement
Parkland formula - %burn x kg x 4 in 24 hrs, half in first 8 hours
What criteria suggest transfer to a burns unit?
Extremes of age
2-3rd 10% in a child/15% adult
Inhalation injury
Special areas
Electrical/chemical burns
NAI
Escharotomy
When does the Parkland formula tend to under-estimate fluid requirements?
Inhalational injury
Delayed resuscitation
Hyperglycaemia
Alcohol intoxication
What is the pathophysiology of a burn?
Local effects
- protein denaturation (42) and cell death (45)
- Jackson’s zones - Coagulation, Stasis, Hyperaemia
Systemic effects
- Respiratory (ARDS)
- CVS - SIRS response
- Loss of skin function
- Increased BMR
-Immune suppression
What are the principles of resuscitation of burns?
First aid at scene - extinguish flame, remove chemical irritants, cool burn (15deg water)
ATLS approach especially airway and breathing and initial fluid resuscitation
Good Secondary Survey and covering of burns with simple dressings e.g. cling film
Burns fluid resuscitation
Adjuncts - NGT if >20%, Tetanus, Eye assessment, warming
How is DIC diagnosed?
Low platelets
Abnormal clotting
Raised D-dimer/FDPs
Low fibrinogen
What is HIT?
Reduction of platelet count of >30-50%, usually 4-14 days post heparin administration
Type 1 - transient fall, not immune related
Type 2 - autoimmune with antibodies against platelet factor-4/heparin complex
What anticoagulants are suitable for use in patients with HIT?
Argatroban (direct thrombin inhibitor)
Danaparoid (factor Xa inhibitor)
Fondaparinux (factor Xa inhibitor)
What are common causes of DIC? (6)
Anything that activates coagulation system
Commonly
- Severe sepsis (Gram-ve)
- Organ destruction (Pancreatitis/Burns)
- Trauma
- Transfusions
- Some obstetric emergencies
- Disseminated malignancy
When can an epidural be sited/removed? (Anticoagulant related)
- 4 hours after Heparin
- 12 hours after prophylactic LMWH
- 24 hours after treatment LMWH
When Plt >100, INR <1.5
What are the fluid volumes in different compartments of a 70kg man
Intracellular (40% - 28L)
Extracellular (20% - 14 L),
- Interstitial ( 75% - 10.5L),
- Intravascular ( 20% - 3L),
- Transcellular (CSF, Intra-ocular 5% 0.5L)
What are the average daily fluid/electrolyte requirements?
NICE Guidelines
30ml/kg/day of fluid
1mmol/kg/day Na, K, Cl
50-100g/day glucose (avoid starvation ketosis)
What are the consequences of Duodenal and Jejunal high output fistulae?
Duodenum - Gastric/ Salivary - 4L/day –> Hypokalaemia/chloraemia
Jejunum - Variable, can be v high output can –> Hyponatraemia/kalaemia/ low bicarb (pancreas)
Why does gastric outlet obstruction cause aciduria?
Preferential preservation of Na+ in dehydration –> excretion of K+ and H+ ions
What is the typical dose of Octaplex?
25-50units/kg
What topical haemostatic agents can be used?
Biological - bovine albumin, fibrin glues, thrombin sealants (Floseal)
Dry matrix - gelatin matrix, oxidised regenerated methylcellulose (surgicel), veriset (PEG and cellulose)
What haemostatic drugs can be used to control intra-operative bleeding?
Anti-fibrinolytics (TXA, Aprotinin)
- TXA 1g over 1 mins then 1g over 8 hours
Recombinant factor VIIa
DDAVP
What is hepatorenal syndrome?
AKI with in patients with Acute/CLD
Usually associated with advanced CLD, cirrhosis and ascites, and up to 40% of patients with this will develop HRS
Two types - Type 1, rapid progressive decline in renal function, Type 2 moderate stable reduction
Prognosis poor
What is the pathogenesis of HRS?
Portal hypertension –> splanchnic vasodilation –> activation of RAAaxis –> renal vasoconstriction
What are the types of hyponatraemia?
True hyponatraemia (serum osmolality <280)
- Hypovolaemic (decrease in sodium > decrease in water, ECF decreased)
- Euvolaemic (increase in water, sodium unchanged, ECF decreased)
- Hypervolaemic (increase in water > Increase in sodium, ECF increased)
Pseudohyponatraemia (serum osmolality 280-295 caused by lipids or plasma proteins)
Translational hyponatraemia (serum osmolality >295 hyperglycaemia or mannitol)
How can different causes of hyponatraemia be classified and treated?
Treat underlying cause.
If hypovolaemic –> isotonic saline
Euvolaemic –> restrict water
Hypervoalaemic –> restrict water and diuretics
What common inotropes/vasopressors are used in critical care?
Noradrenaline α-1 agonist Vasopressor action, minimal effect on cardiac output
Adrenaline α and β receptor agonist Increases cardiac output and peripheral vascular resistance
Dopamine β1 agonist Increases contractility and rate (low dose renal vasodilation, med dose heart, high dose vasoconstriction)
Dobutamine β1 and β2 agonist Increases cardiac output and decreases SVR
Milrinone Phosphodiesterase inhibitor Elevation of cAMP levels improves muscular contractility, short half life and acts as vasodilator
Phenylepherine (pure alpha)
Metaraminol, Epheredine (sympathomimetics)
Vasopressin V1 for vasoconstriction and V2 for vasodilation (useful septic shock)
For Sepsis prob – NA + V
How can cardiac output be monitored non-invasively?
1) Analysis of arterial waveform (Lidco, PiCCO) –> area under systolic waveform = SV
2) Oesophageal doppler monitor (velocity of descending aortic blood flow)
3) Thoracic impedance/bioreactance techniques
What is a normal CVP?
Measured from sternal angle - 0-8mmHg
Tip of catheter at junction of SVC and RA
Indirect measure of volume status
What factors raise the CVP?
Increased intra-thoracic pressure (coughing, PEEP, CPAP)
Impaired right heart function (cardiac failure, tamponade, PE, SVC obstruction)
Decreased by hypovolaemia
How might CVP change with fluid resuscitation in hypovolaemic patients?
500ml fluid challenge:
Hypovolaemia –> non-sustained rise falling after 10 minutes
Normovolaemic –> rise above baseline with slow return
Overloaded –> persistent rise
What does a PA catheter measure?
Pulmonary artery wedge pressure - indirect measure of LV and diastolic (normally 8-12 mmHg)
Septic shock/hypovolaemia –> fall
Pulmonary oedema –> rise
ARDS –> normal
What is cardiac output?
Volume of blood pumped per minute == 5l/min
Indexed to BSA for cardiac index (2.2-3L/min/m2)
What is the Frank-Starling law?
Force of contraction/stroke volume increases with preload (up to a point)
What is the MAP?
DBP + 1/3 (SBP-DBP)
What is the mechanism of inotropes?
increased availability of calcium to cardiac myocytes by activation of adenyly cyclase leading to cAMP and calcium influx
What does a litre bag of Hartmanns contain?
131mmol/l Na
111mmol/l Cl
5mmol/l K
2mmol/l Ca
29mmol/l Lactate
What are colloids?
Large molecular weight containing infusatn usually >30000kda and exert oncotic pressure
Theory being they stay in the intravascular compartment longer
How should a high output stoma be managed?
Strict monitoring of input/output/electrolytes
Adequate IV fluid replacement including elecytolytes
Avoid hypotonic fluids and give balanced solutions
Fibre supplementation
Pharmacological treatments
Stoma nurse
What is DIC?
Consumptive coagulaopathy
Caused by release of free thrombin into circulation
Leading to widespread microvascular thrombosis
What is the pathohysiology of ARF with rhabdomyolysis?
Myonecrosis of postural muscles –> release of K+,PO4, CK-MM, LDH and myoglobin
Myoglobin binds to thick ascending limb of loop –> precipitate and tubular obstruction
Myoglobin = oxygen binding protein of muscle – source of O2 for muscle
What are the causes of rhabdomyolysis?
Direct muscle injury (Blunt trauma, reperfusion, burns, electrocution)
Excessive muscle contraction (status asthmaticus, taser injuries, statins)
How are hospital levels of care defined?
Level 0 - Normal <4hourly obs
Level 1 - At least 4 hourly obs, outreach support, additional monitoring or interventions e.g. chest drain
Level 2 - single organ support e.g. single agent vasopressor (not mechanical vent)
Level 3 - Advanced respiratory support or support of 2+ organ systems
How might level of care post operatively be decided (4)?
Local factors - e.g. some wards cannot manage epidurals
Patient factors e.g. comorbidities, risk calculation, CPET
Surgical factors e.g. flap observations, drains, continuous infusions, bleeding, major surgery)
Anaesthetic factors e.g. prolonged anaesthesia, need for vasoactive)
How do local anaesthetics work?
Block neuronal transmission by:
1) Sodium channel blockade
2) membrane expansion
Small fibres e.g. pain lost before touch sensation
What are the types of LA?
Ester - Cocaine, Procaine, Amethocaine
Amides
- Lidocaine (short acting 2 hours)
- Prilocaine (wide therapeutic index, used IV)
- Bupivicaine (long acting 4 hours)
- Levobupivicaine (less cardiotoxic/vasodilatory effects than bupivicanine)
How does adrenaline effect use of LAs?
Vasoconstriction reduces absorption, prolongs duration and reduces toxicity
In a crisis situation with life threatening haemorrhage what blood products would you administer?
If no grouped blood then O-ve x4 units (or O+ve for males)
How is massive haemorrhage defined?
1) >1 blood volume in 24 hours
2) >1/2 blood volume in 3 hours
3) >150ml/min
4) Transfusion of 10 units PRC in 24 hours with ongoing bleeding
5) Transfusion of 4 units PRC in 4 hours with ongoing bleeding
What does the major haemorrhage protocol comprise of?
20ml/kg PRC
20ml/kg FFP
10ml/kg Platelets
5ml/kg Cryo
In general
In practice what might a major haemorrhage pack comprise?
Pack 1
- 6 units PRC
- 4 units FFP
- optional platelets
Pack 2
- 4 units PRC
- 4 units FFP
- 1 unit platelets
- 2 pools of cryo
What lab parameters should be targeted in a major haemorrhage setting?
Hb. >80
INR <1.5
Plt >80 or 100 if multiple/CNS trauma
Fibrinogen >1g/L
Ionised calcium <1.13mmol/l
What are the complications of transfusion?
-Immune mediated (ABO/other, TRALI, immune modulation)
-Infectious (Hep, HIV, CMV, CJD)
-Metabolic (hypocalcaemia, hyperkalaemia)
-Volume related and idiosyncratic (TACO, thrombocytopenia, hypothermia, hypocalcaemia, hyperkalaemia, acidosis, coagulopathy)
What are some risk factors for nosocomial infection?
Patient factors (illness severity, comorbidity, nutrition, prolonged antibiotic use)
Environmental factors (poor hand hygiene, inadequate staff/space)
Organism factors (antibiotic resistance, pathogenicity)
How is a VAP diagnosed?
Systemic criteria (T<36 or >38 + WCC <4 or ≥12)
Pulmonary criteria ( new increased aspirates, worsening gas exchange, positive cultures, or radiography)
What organisms are associated with a VAP?
Gram-ve organisms (e.g. Gut)
Pseudomonas, Enterobacter, Kelbsiella, E.Coli
What factors can increase the risk of CVC infection?
Site
Poor technique
Multi-lumen
Poor hand hygiene
Frequent dressing changes
What factors can reduce the risk of CVC infection?
Aseptic technique
Early removal and regular review
Antiseptic/silver impregnated lines
Why is malnutrition important to surgical patients?
- Impaired wound healing
- Increased incidence of pressure ulcers
- Overgrowth of bacteria in the GI Tract
- Increases infective complications due immune dysfunction
- Prolonged mechanical ventilatory support
- increased muscle wasting
What are the benefits of enteral vs parenteral feeding?
Enteral
- Fewer infective complications
- Maintains normal gut mucosal integrity (stress ulcers, mucosal atrophy)
- Lower cost
Parenteral
- easier to provide full energy requirements
- does not require gut function/integrity
What are the negatives of enteral vs parenteral nutrition?
Enteral
- difficulty meeting requirements (absoprtion/ileus)
- diarrhoea
- increased risk of VAP
- aspiration
Parenteral
- Access related infections
- Liver dysfunction
- Trace element deficiency
What are the indications for PN?
Absolute - enterocutaneous fistula
Relative
- EN not possible
- Short bowel syndrome
- Prolonged bowel rest, obstruction
- Inflammatory states such as burns, trauma, pancreatitis if EN not possible
What is refeeding syndrome?
Metabolic disturbances that occur when introducing diet after a prolonged period of starvation.
- Hypophoshataemia, hypokalaemia and hypomagesaemia
What is the mechanism of refeeding syndrome?
- Insulin levels rise and cause cellular uptake of K, PO4, Mg
- Low PO4 depletes ATP and 2,3 DPG causing cellular dysfunction, resipratory and cardiac failure
Who is at risk of refeeding syndrome?
Any patients with poor intake for ≥5 days.
Specific
- Alcohol/drug abusers
- Chronically malnourished
- Anorexia
What are the typical daily requirements for components of TPN?
Water 30ml/kg
Calories 25-30kcal/kg (70% CHO, 30% Fat)
Protein 1-2g/kg
Sodium 1-2mmol/kg
Potassium 1mmol/kg
Calcium/Mg 0.1-0.3mmol/kg
How should sugars be managed in an ICU setting?
Tight glucose control is now less favoured
Aim for <10mmol/L
What are typical constituents of TPN?
Lipid emulsion 25% calories including essential fatty acids
CHO - Dextrose 75% calories
Protein 1-2g/kg (essential and non essential amino acids)
Water
Trace elements
What are the essential fatty acids?
- Alpha linoelic acid
- Linoleic acid
What is obstructive sleep apnoea?
- Repeated episodes of partial/complete pharyngeal collapse –> upper airway closure during sleep
- resultant T2RF leads to disruption of normal sleep cycle with awakening
- occurs in about 5%, of whom 80% undiagnosed
What are the consequences of OSA?
Increased risk of:
- MI
- Arrhythmia
- L/RVH
- Pulmonary hypertension
- CVD
- HTN
- Diabetes
How is OSA diagnosed and classified?
Polysomnography (sleep study)
Apnoea hypopnea index (AHI) - number per hour
Severity
- None (<5/hr)
- Mild (5-15)
- Moderate (15-30)
- Severe (>30)
How can you assess for OSA at bedside?
STOP-Bang assessment
- Snoring
- Tired during day
- Observed apnoea
- Pressure (BP)
- BMI ≥35
- Age >50
- Neck circumference >40cm
- Gender (male)
≥3 predicts risk of moderate-severe OSA
How is death defined?
Irreversible loss of consciousness combined with the irreversible inability to breathe, can be by either neurological or circulatory criteria
How is death by circulatory criteria confirmed?
Asystole and lack of respiratory efforts for 5 minutes, with loss of light and corneal reflexes
What factors govern delivery of oxygen to patients?
- Patient airway
- FiO2
- Adequate ventilation
- Alveolar function