Physiology Flashcards
(142 cards)
1
Q
Scoring system which is part of the current international consensus definition for sepsis and septic shock?
A
- SOFA
2
Q
qSOFA?
A
- Quick Systemic Organ Failure
- Components: RR, GCS and SBP < 100mmHg
- qSofa > 2 is 10% mortality
3
Q
Surviving sepsis campaign, compnents? Hour-1 bundle?
A
- Measure lactate and check again if > 2
- Blood culture before antibiotics
- Broad spectrum abx
- 30ml/kg crystalloid for hypotension or lact > 4
- Vasopressor to aim MAP > 65
4
Q
Bugs responsible for necrotising fascitis?
- Type (1) - Polymicrobial?
A
- Staphylococci
- Anaerobes
- Gram negative
- Immunocompromised
5
Q
Bugs responsible for necrotising fascitis?
- Type (2) - Monomicrobial?
A
- Beta-haemolytic streptococci group A (S. pyogenes)
- Co-infection with S. Aureus
- Trauma
6
Q
Options for diagnosis & management of Necrotising Fascitis?
A
- Fascia biopsy
- Immediate surgery
7
Q
Pharmacokinetics of antibiotics?
A
- Dose given reaches Cmax (maximum concentration)
- Distribution & elimination occurs
- MIC reached (Minimal inhibitory concentration).
8
Q
Minimal inhibitory concentration, properties?
A
- Concentration must be above MIC
- All beta-lactams work by duration above MIC
9
Q
Antibiotics of choice in Necrotising fasciitis?
A
- Vancomycin if MRSA is a concern
- flucloxacillin for staph. Aureus
- clindamycin for streptococci (Good tissue penetration)
10
Q
Coverage of Clindamycin?
A
- Anaerobic cover
- Streptococcus
11
Q
Immunoglobulin as adjunctive therapy in sepsis?
A
Effective for necrotising fasciitis. InStinct trial (Scandinavian)
12
Q
AF and SVV?
A
There is a decrease in SVV with AF
13
Q
Tricyclic antidepressant overdose and ECG changes?
A
- Prolonged QRS / QTc
14
Q
Timing of inflation of intra-aortic balloon should be timed with which portion of the ECG?
A
Middle of T-wave
15
Q
Mechanical assist cardiac device, indication?
A
- Intractable arrhythmias in severe LV dysfunction
- Chronic HF causing renal & hepatic dysfunction
- Intractable angina with poor LV function despite medical & revascularization treatment
- Post-cardiotomy shock
16
Q
What is the commonest cause of pulmonary HTN?
A
- Left heart disease
16
Q
What is the commonest cause of pulmonary HTN?
A
- Left heart disease
17
Q
Effect of high respiratory rate on RV and LV?
A
- This will increase the pre-load of the RV
- It increases LV afterload
- Increased transmural pressures
18
Q
PEEP & cardiovascular response?
A
- Decreases transmural pressures
- Reduces RV pre-load
19
Q
What contributes most to ventilator-induced lung injury?
A
Plateau airway pressure
20
Q
Peak airway pressure is related more to ?
A
Airway resistance
21
Q
Airway driving pressures will decrease with increasing what ventilator setting?
A
PEEP
22
Q
How to calculate driving pressures?
A
Driving pressures = Plateau pressures - PEEP
23
Q
Calculation of compliance ?
A
Compliance = Volume / Driving pressure
24
Calculation of CO2 gap?
CO2 gap = PaCO2 - ETCO2
25
Conditions causing increased CO2 gap?
- PE
- Dead-space ventilation
- Low filling status - Needs fluid resuscitation
26
Uses of Esophageal pressure monitoring?
- Used to assess whether ventilation is lung-protective
- Measures estimated pleural pressure
- It can measure patient's work of breathing
27
NAVA (Neurally-Adjusted Ventilator Assist)? Functions & uses?
- Measures the electrical activity of the coastal diaphragm
- Allows for proportional ventilation
28
Wasted effort can be illustrated using what diagram?
The campbell diagram
29
Improve patient - ventilator interaction?
- Increasing trigger sensitivity
30
Factors affecting cardiac output?
- Pressure within the venous system
- Capacitance of the venous reservoir
- The resistance to venous return
- Peripheral distribution of the blood flow
31
What is Cardiac output?
CO = HR x SV
32
Factors influencing SV?
Preload, contractility & afterload
32
Factors influencing SV?
Preload, contractility & afterload
32
Factors influencing SV?
Preload, contractility & afterload
33
Preload dependent on ?
Venous return
34
Afterload dependent on?
Arterial pressure
35
What is CVP?
- Equivalent to the RA pressure
- Filling pressure of the right side of the heart
- Determinant of cardiac function
- It is a key determinant of venous return
36
Venous valves in the thorax?
There are no venous valves in the thorax
37
Factors increasing CVP?
- Increased circulating volume
- Decreased venous capacitance
- Increased venous tone (vasopressors)
- Decreased cardiac function (HF/Obstructive acute HF - PE/Tamponade)
38
Etiology of shockable rhythms?
- IHD/ AMI
- Electrolyte abnormalities
39
Etiology non-shockable rhythms?
- Hypovolaemia
- Hypoxia
- Hypothermia
- Electrolyte abnormality
- PE
- Tamponade
- Tension PTX
- Trauma & Toxins
- AMI
39
Etiology non-shockable rhythms?
- Hypovolaemia
- Hypoxia
- Hypothermia
- Electrolyte abnormality
- PE
- Tamponade
- Tension PTX
- Trauma & Toxins
- AMI
40
Factors causing falsely elevated oxymetry readings?
- Carboxy-haemoglobin
- Met-haemoglobin
41
Factors causing falsely low oxymetry readings?
- Ambient light
42
Location of the respiratory centre?
Medulla oblongata
43
Location of the respiratory centre?
Medulla oblongata
44
Functions of the central chemoreceptors?
- Directly senses CO2 changes (conc. of hydrogen ions in the CSF)
-
45
Location of peripheral chemoreceptors?
- Carotid
- Aortic arch
46
Function of peripheral chemoreceptors?
- Sense PO2
- Sense change in pH of blood
47
Calculation of PaCO2?
PaCO2 = CO2 production / Minute volume
48
Calculation of alveolar ventilation?
Alveolar ventilation = RR x (Tidal volume - Dead-space)
Effective tidal volume diminishes with increased RR
49
What is dead-space ?
- Volume not participating in gas exchange
50
What are the different components of dead-space?
- Anatomical dead-space (2ml/kg)
- Alveolar dead-space
- Instrumental dead-space
51
Physiology of alveolar dead-space?
- Ventilated but not perfused
- Increased arterial CO2 due to lack of excretion via the lungs
52
Causes of alveolar dead-space?
- PE
- Hypoperfusion
- Intrinsic PEEP
53
Calculation for measuring dead-space?
VD/VT = PaCO2 - PeCO2 / PaCO2
PeCO2 - Mixed expired CO2
54
Causes of hypercapnia ?
- Low minute volume
- Increased dead-space
- High CO2 production
55
Potential systems which could be affected that causes hypercapnia?
- CNS
- PNS
- Respiratory muscles
- Chest wall and pleura
- Upper airway
- Lungs
56
What is the alveolar gas equation?
PAO2 = FiO2 x (P.atm - P. H2O) - PaCO2 / RQ
Ex;
PAO2 = 0.21 x (760 mmHg - 47) - 40 / 0.8 = 100 mmHg
PACO2 = Alveolar O2
57
gases and vapors in the alveolar?
- Nitrogen
- Oxygen
- CO2
- Water vapor
58
Hypoxia & altitude ?
The atmospheric pressure is lower at higher altitude hence low amount of FiO2
58
Hypoxia & altitude ?
The atmospheric pressure is lower at higher altitude hence low amount of FiO2
59
Causes of hypoxia?
Elevated A-a gradient
- Shunt (A-a gradient elevated)
- V/Q mismatch (A-a gradient elevated)
Low A-a gradient
- Altitude (A-a gradient low)
- Hypoventilation (A-a gradient low)
- High CO2
- Diffusion limitations ( Rare ) - Chronic lung disease / COPD
60
What is shunting ?
This is volume of blood not taking part in gas exchange
61
Anatomic shunt?
- Normally < 5% in healthy individuals
- No response to increased FiO2
62
Venous admixture or low V/Q (Shunt)?
- Improves with increase FiO2
- Chemo-sensors prevent admixture by Hypoxic vasoconstriction
63
Physiology of hypoxic vasoconstriction?
- Low Oxygen levels detected inside the alveolar
- Capillary vasoconstriction occurs
- Blood diverted to more well oxygenated capillaries
64
Calculation of A-a gradient ?
- It should normally be very low
A-a gradient = PAO2 - PaO2 = FiO2 x (P.atm - P.H2O) - PaCO2 -PaO2 / RQ
65
Shunt equation?
See EDIC notes
66
Shunt equation?
See EDIC notes
67
Treatment for MH?
Dantrolene
68
Temperature is higher in pyrexia or hyperthermia?
Higher in hyperthermia
69
Hyperthermia?
- Temperatures higher than pyrexia
- Thermoregulatory mechanisms are lost
- Temperatures usually > 41.3 degrees Celsius
70
Where is thermoregulation processed ?
At the hypothalamus
71
Definition of fever ?
Core temperature > 38.3 degrees Celsius
72
Pyrexia and thermoregulatory mechanisms?
Thermoregulatory mechanisms are preserved
73
What chemical results in an elevated temperature setpoint in the brain?
PGE2 in the CNS
74
Total body mass constitution?
- Made up of 60% of water
75
Total body fluid is divided into ?
- 2/3 intracellular fluid
- 1/3 Extracellular fluid
76
The ECF is divided into?
- Interstitial fluid = 80%
- Plasma = 20%
77
Intracellular compartment volume?
25 litres
78
Extracellular compartment volume?
17L
79
What are the intracellular electrolytes ?
- Potassium = 140mEq/L
80
What are the extracellular electrolytes ?
- Sodium = 140mEq/L
81
Osmolality of the fluid compartment?
280 mOsm/kg
82
Units of hydrogen ion concentration ?
nmol/L (Nano-moles / Litre)
83
Normal hydrogen ion concentration ?
40 nmol/L
84
Acuity of liver failure?
Hyper-acute = < 7 days (Drugs induced or hypoxia)
Acute = 7 - 28 days ( Autoimmune or drug related)
Sub-acute = > 28 days (Unknown cause)
85
KCH criteria to identify patient's at risk of death from liver failure?
- PT > 100s & INR > 6.6 ( + Encephalopathy)
86
KCH criteria to identify patient's at risk of death from liver failure? Any three out of 5 criterias? (+ Encephalopathy)
- Age: < 10 or > 40
- Bilirubin > 300
- Duration of jaundice before the onset of encephalopathy > 7 days
- PT > 50s or INR > 3.5
- Non-hepatitis A or B / drug induced
87
Scoring systems in liver failure?
- MELD
- APACHE II
- CLIF-SOFA
- Child-Pugh Score
88
Scoring systems in liver failure?
- MELD
- APACHE II
- CLIF-SOFA
- Child-Pugh Score
89
Primary (hepatic) causes of acute liver failure?
- Drug related
- Viral hepatitis
- Toxin induced ALF
- Budd-Chiari syndrome
- Autoimmune
- Pregnancy related
90
Secondary (extra-hepatic) causes of ALF?
- Ishcaemic hepatitis
- Haemophagocytic syndrome
- Metabolic disease
- Infiltrative disease
- Lymphoma
- Infections (e.g malaria)
91
Primary causes of chronic liver disease?
- Wilson's disease
- Autoimmune
- Budd-Chiari
92
Seconadary causes of chronic liver disease ?
- Liver cancer
- Alcoholic hepatitis
93
Hypoxamia mechanisms ?
- inadequate fio2
- inadequate delivery to target organ
94
What is the oxygen cascade?
Transfer of oxygen from the environment to the alveoli and subsequently arterial blood.
95
Oxygen cascade & oxygen content?
Reduction in oxygen tension from the environment to arterial blood.
96
Main factors causing hypoxia ? See individual breakdown of the below points ……
- low fio2 (altitude, hypoxic gas mixture)
- Alveolar hypoventilation
- diffusion impairment
- V/Q mismatch & shunt
97
Consequence of alveolar hypoventilation?
- decrease in V/Q
- A-a gradient is usually normal
98
Causes of pulmonary diffusion impairment?
- Increased thickness of alveolar membrane (fibrosis)
- Decrease in capillary transit time ( severe sepsis)
- Decrease in capillary blood volume (hypotension)
99
Variation of V/Q from base to apex?
0.6 - 3.0
100
V/Q mismatch causing hypoxia?
- Reduction of ventilation relative to perfusion (low V/Q).
101
Hypoxic pulmonary vasoconstriction?
Physiological pulmonary vasoconstriction will reduce blood flow to poorly ventilated alveolar units, thus a shunt
102
Atmospheric pressure at sea level?
101.3 kPa
103
Calculation of atmospheric PO2?
PO2 = FiO2 x Atmospheric pressure
104
Outline processes of the oxygen cascade ?
- inspired oxygen
- Trachea - humidification
105
What is hypoxaemia?
This is low arterial oxygen tension occuring due to pathology in transfer of oxygen from the atmosphere to the left side of the heart.
106
Hypoxia is a consequence of either ?
- Inadequate arterial oxygen tension
- Inadequate delivery of oxygen to the end organ
107
Inspired oxygen within the oxygen cascade?
- FiO2 is 21% in RA
- Atm pressure 101.3 kPa at see level
- PO2 = FiO2 x Atm pressure
- Pathologies - Altitude , hypoxic gas mixture
108
Trachea in the oxygen cascade?
- Humidification
- Saturated vapour pressure of water - 6.3 kPa @ 37 degrees
- PO2 = FiO2 (Atm pressure - SVP H2O)
- Normal PO2 19%
109
Alveoli in the oxygen cascade?
- Ventilation
- Normal PACO2 5.3 kPa
- Alveolar gas equation is used to calculate PO2 (Google it)
- Hypoventilation will cause hypoxia
110
Pulmonary capillary in the oxygen cascade?
- Diffusion
- The rate of diffusion across the alveolar member determined by Fick's law
- A - a gradient = PAO2 - PaO2
- Pathologies; Emphysema, fibrosis & Oedema
111
Artery in oxygen cascase?
- Admixture / shunt
- Oxygenated blood from the lungs mixes with deoxygenated blood in the left heart (<3%)
- Admixure arises physiologically from Thebesian and bronchial veins.
- Pathologies; Intra-cardiac or intra-pulmonary shunts, ARDS, effusion, PTX
- Oxygen content = (SPO2 x Hb x 1.34) + 0.003 x PO2
112
Hypoxia corrected with increasing FiO2?
- V/Q mismatch
- Diffusion impairment
- Alveolar hypoventilation
- Low inspired oxygen
113
Hypoxia with normal A-a gradient?
- Alveolar hypoventilation
- Low inspired oxygen
114
Hypoxia with normal shunt fraction?
- Diffusion impariment
- Alveolar hypoventilation
- Low inspired oxygen
115
The P50?
Represents the PaO2 at which Hb is 50% saturated
116
Properties of oxygen?
- Low solubility in plasma
-
117
Haemoglobin and ODC?
- Affinity for oxygen increases with every molecule of oxygen it binds
- Left shift of the curve - Increases Hb affinity for oxygen
118
Factors determining left-ward shift of the ODC?
- Decreased temperature
- Decreased CO2
- Decreased 2,3-DPG
- Increased pH
119
Factors determining right shift of ODC?
- Increased temperature
- Increased arterial CO2
- Increased 2,3-DPG
- Decreased pH
120
Determinants of oxygen delivery (DO2)?
- Transfer of oxygen from atmosphere to blood
- Carriage of oxygen in blood bound to Hb
- Systemic blood flow (Cardiac output)
121
Oxygen delivery flux equation?
DO2 = CO (SaO2 x Hb x 1.34) + 0.003 x PO2
122
Classification of hypoxia?
- Hypoxaemic hypoxia - Low arterial oxygen tension
- Anaemic hypoxia - Low Hb or impaired (Methaemoglobinaemia, carbonmonoxide poisoning)
- Stagnant hypoxia - Low cardiac output
- Cytotoxic hypoxia - Abnormal cellular utilization of oxygen. Failure of aerobic respiration (Cyanide poisoning)
123
Properties of carbondioxide?
- About 22 times more soluble than oxygen
- Affected only by ventilation - Alveolar CO2 and minute ventilation are directly related
124
Components of dead-space?
- Anatomical dead-space
- Alveolar dead-space
- Physiological dead-space
125
Anatomical dead-space?
- Consists of the conducting airways
- Do not contribute to gas exchange
- Its approximately 2ml/kg
- Reduced by ETT
- Fowler's method is used to measure anatomical dead-space
126
Alveolar dead-space?
- Proportion of tidal volume entering the alveolar - Not perfused
- Increased in disease
- Present in PE & low cardiac output state
127
Physiological dead-space?
- Combination of anatomical and alveolar dead-space
- Calculated using the Bohr's equation
128
What is the Bohr's equation?
- Used to calculate physiological dead-space
- VD/VT = PaCO2 - PeCO2 / PaCO2
129
Lung volumes?
- IRV = 2500mls
- TV = 500mls
- ERV = 1500mls
- RV = 1500mls
- TLC = 6000mls
- VC = 4500mls
130
Calculation of alveolar MV?
- (TV - dead-space) x RR =
- Main determinant of Mv is arterial CO2
- Central chemoreceptors in the medulla detect changes in pH associated with changing CO2
- PO2 becomes a determinant of MV only in hypoxia
131
Barriers to infection and percentage of protection?
- Physical barriers (99%)
- Innate immune response (0.9%)
- Adaptive immune response (0.1%)
132
Components of physical barriers to infection?
- Skin
- Cilia
- Acidity
- Lysozomes
- Normal bacterial flora
133
Components of innate immune response?
- Neutrophils
- Mast cells
- Macrophages
- NK cells
- Complements
- Acute phase
134
Components of Adaptive immune response?
- B-lymphocytes
- T-lymphocytes
135
Causes of dynsfunction to physical barriers? skin
- Burns
- Trauma
- Steven-Johnson's Syndrome
- Kartagener's
- Prolonged antibiotics
136
Causes of dysfunction to innate immune response?
- Wiscott-Aldrich
- Leucocyte adhesion defect
- Complement defect
- Steroids
- TNF-alpha inhibitors
- Chemotherapy
- Diabetes
- SLE
- Liver failure
- Malignancy
137
Causes of dysfunction to adaptive immune system?
- Hypogammaglobinaemia
- DiGeoge's syndrome
- Common variable immunodeficiency
- Lymphoma
- HIV
- Chemotherapy
