Sepsis Flashcards
Pyrexia - what is it?
What benefits does it have?
Fever
Pyrexia inhibits bacterial growth and mobilises immune defences, damaging membranes of both the body and the bacterial cells
Classic Symptoms of Sepsis?
- Hypo or hyper-thermia
- Elevated heart rate (>130 BPM)
- Low blood pressure
- Hypoxia /Hypoxaemia
- Shadowing on chest X-ray (‘white-out’) - fluid in the lung tissue due to inflammatory mediators
- Elevated white blood cell count - or reduced!
- Hyperglycaemia
- Altered mental state / consciousness
- Decreased urine output(<0.5ml/kg/hr)
- Coagulopathy - problems with clotting
2 x famous pyrogens?
what do they do?
- Tumor Necrosis Factor
- Interleukin 1
Both travel in the blood, to work directly to lower the set-point via the hypothalamus - heat conservation and generation mechanisms are initiated e.g. shivering
OR indirectly via release of prostoglandins
What happens when cell membranes are broken down?
e.g. through trauma, bacterial infection
Bigger the insult, bigger the pyrogen release
Release pyrogens (proteins)
What are cytokines?
Pro-inflammatory proteins, chemical messengers produced by damaged tissue and WBC’s
e.g. IL-1, TNF
What does TNF do?
Acts on hypothalamus directly.
Induces IL-1 and IL-6 release
Macrophage activation
How can you explain pyrexia?
3 ways
- Release of pyrogens
- Direct action of cytokines
- Increased metabolic rate (organs fighting infection work harder)
How does Pyrexia damage human tissue?
- Disrupting the Golgi apparatus
- SWELLING THE MITOCHRONDIA (inhibiting ATP production)
- Change cellular permeability
- Disrupt the nucleus and aggregation of chromatin (DNA + proteins in nucleus)
- Elevating protein synthesis
What symptoms are explained by fever & reduced ATP production?
- normal electrical activity - heart, nervous system
- cardiac arrest
- seizures
- changes in level of consciousness
Sepsis can also cause hypothermia - why?
Poor oxygen delivery to tissues - organs start to shut down
Liver - under-perfused, become cold
Elevated heart rate - why/how?
3 x explanations
- Stress response - the Sympathetic nervous system stimulates an increased release of ADRENALINE and NORADRENALINE from the ADRENAL MEDULLA (stress response), stimulating heart rate and contractibility by acting upon ALPHA and BETA receptors in the heart
- In response to falling blood pressure (low circulating volume) - Baroreceptors -> Medulla Oblongata -> Vagus nerve (release the break) - > increased HR
- Sweating due to fever - dehydrated, this can drop BP
Elevated Respiratory Rate - how / why?
- Acidosis - falling pH
BP low? perfusion to tissues is low, respiration becomes anaerobic? -> lactic acid/ lactate
BP low? perfusion to kidney is low, this can impact urine output - retain hydrogen
Fast HR? More CO2 being produced - acidosis
ALL CAUSES…
Chemoreceptors -> Medulla Oblongata -> Phrenic and respiratory nerves -> stimulates lungs!
- Stimulation of medulla oblongata by endotoxins and other inflammatory mediators (e.g. TNF) has been proposed as a cause
Inflammatory Mediators:
Histamine
Bradykinin
Cytokines - TNF, IL-1,2,3 etc.
What does HISTAMINE do?
Makes the capillary wall and the alveoli wall increasingly permeable. A profound vasodilator. Found in MAST and BASOPHIL cells.
Water leaves capillary bed into alveoli
relevance for anaphylaxis
Why can you have ‘white out’ on a chest x-ray due to Sepsis?
Due to release of inflammatory mediators, cells become increasingly permeable, water leaves capillary bed and enters alveoli.
Why might someone with sepsis become hypoxic?
Inflammatory mediators -> permeability of cells, fluid into alveoli
Switch from aerobic to anaerobic respiration (fewer ATP’s)
Compare Anaerobic and anaerobic respiration
Aerobic - 36 ATP
Anaerobic - 2 ATP’s plus lactate and lactic acid
What is the difference between lactate and lactic acid?
Lactic acid increases in anaerobic respiration due to a lack of oxygen being delivered to cells resulting in anaerobic respiration producing large numbers of hydrogen acids.
Lactate is an alkali bicarbonate substance - it increases in your cells in an attempt to buffer lactic acid and normalise pH levels in cells.
pH reducing due to hypoxia…as pH falls, lactate increases
Why other than anaerobic respiration, can someone have high levels of lactate?
If tissues are poorly perfused, if you have kidney or liver problems.
Lactate is metabolised by liver (50%) and kidneys (20-30%)
Elevated WBC count- how / why?
Lymphocytes
Lymphocytes develop and mature as a young child
They dormant until activation - called lymphocyte proliferation
The body has only a few lymphocytes that recognise invading organisms, but hundreds of thousands are required to fight infection
Body has a ‘memory’ of previous pathogen - when phagocytosis takes place a ‘warning system’ is set up - phagocyte kills the pathogen, then retains a tiny tiny amount of pathogen DNA- in the future helper T cell can be quickly activated - WBC quickly divide and increase.
HIV destroys Helper T cells - this is why it is so devastating to immune system - normally trivial infection becomes serious
Hypotension - how / why?
- Dehydration can lead to hypotension (via increased respiratory rate OR fever)
- Widespread vasodilation and increased tissue permeability -> BP will fall
due to 4 x classic inflammatory mediators
What does KININS do?
e.g. BRADYKININ
Kinins are rapidly generated in blood plasma after tissue injury leading to VASODLATION, INCREASED VASCULAR PERMEABILITY and CELL MIGRATION
What does CYTOKINES do?
Protein, chemical messengers produced by damaged tissue and WBC
e.g. IL-1, TNF
What are the 4 x classic inflammatory mediators
- Cytokines
- Prostoglandin
- Kinins
- Histamine
Altered Mental State - how/ why?
Slurred speech?
Optimal brain funct. requires stable brain environ - pH, temp, o2, glucose delivery
Hypo-perfusion
Not entirely understood, believed t be a problem with protein/ amino-acid metabolism
= poor oxygen, poor cellular activity
Hyperglycaemia - how / why?
Stress response…
Glucagon releasing cells in the pancreas are stimulated to release glucagon into the liver, this acts on the liver, this breaks down glycogen into glucose into the bloodstream.
Decreased urine output - how / why?
- Poor perfusion to kidneys due to low BP
The renal system responds to hypotension by stimulating RENIN secretion from the juxtaglomerular apparatus in the bowman’s capsule of the nephron.
Renin converts ANGIOTENSIN to ANGIOTENSIN 1, which is subsequently converted to ANGIOTENSIN 2 by the lungs
ANGIOTENSION 2 has 2 x effects:
- vasoconstriction of smooth muscle
- stim of aldosterone by adrenal cortex
- Hypothalamus senses decreased blood volume / increased osmolarity
ADH is released from the posterior pituitary gland in response to a decrease in BP (detected by baroreceptors)
ADH indirectly leads to an increased reabsorption of water and salt by the distal tubule, the collecting ducts and the loop of Henle in the nephron
ANGIOTENSION 2 has 2 x effects:
- vasoconstriction of arteriolar smooth muscle
- stimulation of ALDOSTERONE secretion by the adrenal cortex
this increases salt and water conservation in the kidney, thereby reducing urine output
What does ALDOSTERONE do?
Increases salt and water conservation in the kidneys
What does ADH do?
Anti-diuretic hormone
Hypothalamus senses decreased blood volume / increased osmolarity
ADH is released from the posterior pituitary gland in response to a decrease in BP (detected by baroreceptors)
ADH indirectly leads to an increased reabsorption of water and salt by the distal tubule, the collecting ducts and the loop of Henle in the nephron
Coagulopathy - how / why?
The ENDOTHELIUM lining of blood vessels is a major contributor to the inflammatory response and is an active metabolic organ responsible in part for both coagulation and anticoagulation
-> during inflammatory response, mediators are released into the bloodstream leading to uncontrolled intravascular inflammation.
LIVER- involved a lot in clotting, a lot of the clotting substances are metabolised by the liver
What does osmolarity mean?
The concentration of a solution expressed as the total number of particles per litre.
Fibrin
Dissolving fibrin clot
fibrin clot - coagulation part of healing
= anticoagulation part of healing, strongly suggested that ENDOTHELIAL LINING controls how long you clot for , how long you pause, and when the clot is broken down
Inappropriately clotting and bleeding - coagulopathy (explains mottled / strange skin appearance)
Sepsis - definition
A life-threatening organ dysfunction due to a dysregulated host response to infection
- Sepsis Campaign & EICS
(SC = offshoot of European Intensive Care Society)
‘Dysregulated’ ?
Normal responses / changes become problematic - e.g. induce a seizure
What’s unclear?
Why one person may have normal
Infection - definition:
Microbial phenomenon characterised by an inflammatory response to the presence of micro-organisms or the invasion of normally sterile host tissue by those organisms
e.g. bactaraemia
bactaraemia
presence of viable bacteria in the blood
Global burden of sepsis?
Difficult to ascertain - WHO 2018
30 million people worldwide each year
Estimated that 3 million new-borns and 1.2 million children suffer from sepsis globally each year
3 of every 10 deaths due to neonatal sepsis are thought to be caused by what?
Resistant pathogens (WHO 2018)
How often does someone die of sepsis in the UK?
Every 4 hours.
Sepsis Campaign (Sepsis Research 2020)
How many deaths annually in the UK?
52,000 deaths in the UK each year (more than breast and bowel cancer combined)
Sepsis Campaign (Sepsis Research 2020)
How many people die globally each year from sepsis?
Around 11 million people per year
That’s 1 in 5 of all deaths
Sepsis Campaign (Sepsis Research 2020)
Where does sepsis stand in comparison to other diseases?
Number 1 cause of preventable death in the world
Up to 15,000 lives a year could be saved in the UK through prompt diagnosis and treatment
Sepsis Campaign (Sepsis Research 2020)
York Health Economics Consortium (YHEC)
Over 14,000 lives a year could be saved in the UK through prompt diagnosis and treatment
Costs £15.6 billion per year in the UK - £2.8 billion could be saved
One in four NHS hospital trusts is failing to give antibiotics to half their patients with sepsis in the recommended timeframe
How many deaths associated with pregnancy and childbirth is due to maternal sepsis?
one in ten
-WHO, 2018
Who is at risk of sepsis?
Anyone, especially vulnerable populations e.g.
- elderly
- pregnancy
- neonates
- those in hospital
- chronic health conditions
60% of cases of sepsis are caused by?
Bacteria!
Can also be virus, fungi, parasites…
Parts of bacteria?
ribosome mesosome plasma membrane CELL WALL capsule plasmid DNA bacterial flagelium chromosomal DNA (floating in cytoplasm) fimbriae
What do bacterial cells not have that humans do?
ER
golgi bodies
cell
nucleus
What do antibiotics tend to do?
Damage the cell wall of bacteria
How do bacteria replicate?
How fast?
Via binary fission - requires protein synthesis (cell division)
Can multiple 2.x every 20 minutes!
How can you test bacteria?
Gram stain test
Gram stain test - what does +/- mean
Gram +ve : Stains purple, thick cell wall
Gram -ve : Not coloured, thinner cell wall, have an additional lipid coat (phospholipid)
Gram stain test (Hans Gram)
- Differentiates bacteria based on whether or not stain
- respond to thickness of cell wall
How can bacteria be classified?
By shape:
- Cocci (spherical)
- Bacili (rod-shaped)
- Spirals
- Strept - chains
- Staph - bunched together
By gram stain
Examples of bacteria which are:
- Cocci (spherical)
- Bacili (rod-shaped)
- Spirals
- bacili - anthrax (gram+ve)
Example of
Gram positive bacteria
Gram negative bateria
Gram +ve: streptococcus pneumoniae
Gram -ve: e-coli
Endotoxin: Definition
Structural components of bacterial cells - part of the cell wall (Lipopolysaccharides)
Liberated when bacteria is destroyed by the immune system
Toxic to human cells
Endotoxin - what are the effects?
Stimulates:
- TNF (cytokine protein)
- IL-1, IL-2
- Histamine (vasodilator -> permeability of cells fluid-> into tissues)
- Bradykinin (vasodilator)
- Prostaglandin
- Activation of coagulation system
meaning dead bacteria can continue to damage cells post-death
Exotoxin: Definition
Products of micro-organisms that are harmful to the host - some produce one significant toxin e.g tetanus
Bacteria with endo and exotoxin?
Pseudomonas
Examples of enzymes(?) released by bacteria and their actions:
STREPTOKINASE (streptococci) dissolves fibrin clots this preventing the isolation of infection by the inflammatory response
HYALURONIDASE
(pneumococci, streptococci, staphylococci) digest ell membrane permitting tissue penet
Examples of ENZYMES released by bacteria and their actions:
STREPTOKINASE (streptococci) dissolves fibrin clots this preventing the isolation of infection by the inflammatory response
HYALURONIDASE
(pneumococci, streptococci, staphylococci) digest ell membrane permitting tissue penetration
LEUOCIDIN
(staphylococci, streptococci) disintegrates phagocytes
- note - all of these are streptococci
HAEMOLYSIN
(clostridia, staphylococci) dissolves red blood cells, inducing anaemia and limiting oxygen delivery
Inflammatory response in sepsis is:
exaggerated, excessive
driven by bacterial endo and exotoxins
What do the inflammatory mediators cause?
Widespread vasodilation and increasing permeability of tissues
In sepsis - driven by endo/extoxins
What does PROSTAGLANDINS do?
A potent hormone-like substance found in most tissues, influences:
- vascular tone
- platelet aggregation
- inflammatory response
Skin - deter bacteria, why?
- low pH
- fatty acids in sebaceous secretions
- presence of lysozymes
- loads of resident bacteria
What if bacteria gets in a cut?
process
They can release enzymes which can;
- dissolve fibrin clots
- dissolve cell membranes
Allowing travel into the circulatory system - 5 l per minute! ‘super-highway’
= bacteraemia (blood poisoning)
Big WBC?
Macrophages
Monocytes
What happens during bacteraemia?
Macrophages/monocytes hunting bacteria, bacteria ‘hunting’ WBC’s
- Bacteria gains entry
- Bacterial ENDOTOXIN binds to CD14 MACROPHAGE receptor
- This stimulates release of TNF
- TNF acts on numerous WBC, stimulating further cytokine release
AKA - CYTOKINE STORM
Clinical Effect of TUMOUR NECROSIS FACTOR
pro-inflammatory mediator
Activation of inflammatory cascade
-> fever, hypotension, tachycardia, tachypnoea, hyperglycaemia, metabolic acidosis, third spacing (fluid shift)
Clinical Effect of IL-1
pro-inflammatory mediator
Pyrogen
-> fever, increasing WBC, release amino acids from skeletal muscle, decreasing systemic vascular resistance AKA vasodilation (lower BP)
Clinical Effect of IL-6
pro-inflammatory mediator
Fever, antibody secretion, neutrophil production
Clinical Effect of IL-8
pro-inflammatory mediator
Stimulates neutrophil function and attracts inflammatory cells to the site of infection / injury
Clinical Effect of TISSUE FACTOR
pro-inflammatory mediator
Initiates blood clotting
Clinical Effect of INTERFERON - Y
pro-inflammatory mediator
‘interferes’ with the activity of virus’
- Macrophage activation
What is ‘third spacing’?
Fluid shift in circulatory system
cytokine storm?
sudden, dramatic release of inflammatory mediators following bacterial stimulation of endotoxin of CD14 receptors (found on white macrophage cells)
Sequential Organ Failure Assessment (qSOFA) HAT i.1. 2 or more of the following:
HAT
H - hypotension SBP less than or equal to 100 mmHg (mm mercury) - but, consider baseline
A - Altered mental state
T - Tachypnoea RR greater or equal to 22
*Critique - BTS - RR above 30
NICE / RCUK - 25 and above
Assessment for Sepsis?
qSOFA (Sequential Organ Failure Assessment):
Respiratory rates - when to worry?
NICE / RCUK - 25 and above
BTS- 30 and above
qSOFA - 22 and above
Respiratory rate - what do you assess?
Rate, depth, pattern
Classic sepsis symptoms:
- Fast HR over 90 BPM
- High or low WBC (under 4,000 /mml or over 12,000 mmL)
- High lactate over 4
- Temperature over 38 or under 36
- Hypoxaemia
- Decreased urine output (0.5/kg/hr minimum)
- Hyperglycaemia
- Coagulopathy
NICE Risk stratification tool for suspected sepsis - what
- Altered level of consciousness
- Raised RR, 25 p/m or more
- Low systolic BP, or a drop
- Sig increased HR
- Poor urine output
- Mottled or ashen appearance
- Rash?
- Cyanosis
- BUT - only mention of temperature is BELOW 36 degrees
NICE ‘red flag’ tool
ONE:
Unresponsive / pain / voice Fast HR Fast RR Cyanosis Poor urine output Elevated
Parliamentary and Health Service Ombudsman (2013)
S E P S I S
S - Slurred speech E - Extreme muscle pain P - Passing no urine S - Severe breathlessness I - I feel I might die S - Skin mottled / discoloured
