Introduction to Septicaemia Flashcards
What is sepsis?
Sepsis is a syndrome defined as life-threatening organ dysfunction due to a dysregulated host response to infection.
The immune system overreacts to an infection and starts to damage your body’s own tissues and organs.
Sepsis and septicaemia are not the same thing.
Sepsis, severe sepsis and septic shock are a continuum and not three separate conditions. You can progress from one to the other.
What is septic shock?
Septic shock is sepsis with persisting hypotension requiring vasopressors to maintain a mean arterial pressure ≥ 65mmHg, and having a serum lactate level > 2mmol/l, despite adequate fluid resuscitation.
- Fluids given, but BP not adequately raised
- Evidence of lack of blood flow/oxygenation to major organs
- Progressive organ failure
What is the pathophysiology of sepsis?
Since sepsis is about the body’s acute and overwhelming response to infection, we are looking at excessive activation of post-defence mechanism rather than the direct effect of micro-organism.
In sepsis, molecules from the infectious agent or released from dead post cells bind to host immune cell receptors, causing the release of pro-inflammatory cytokines and reactive oxygen species that help kill bacteria.
This causes activation and proliferation of leukocytes, activation of the compliment system cause a wide range of damage to host cells and tissues. This results in various effects such as increased vascular permeability (leaky), the gaps in the vessels are big enough to allow some proteins to escape as well as fluid. Patients can become oedematous and blood volume falls, which is the reason for lower blood pressure. The body responds by shutting down peripheral blood vessels which are less essential to try and keep the organs perfused. Heart rate increases in response to low blood pressure. Platelets can aggregate and block small vessels. This is called disseminated intravascular coagulation.
Why is it harder for oxygen to reach the tissues in sepsis ?
The interstitial space has a small amount of fluid across which the oxygen dissolves to reach the tissue cells. In sepsis, the release of cytokines causes the endothelium to become leaky, allowing large molecules and fluid to cross into the interstitial space which is between the micro vasculature and the tissue. This makes it harder for oxygen to reach the tissue cells.
Also explained the drop in blood pressure because of the reduced volume in the circulatory system.
What causes hyper coagulability of sepsis?
Hypercoagulability of sepsis is caused by the release of tissue factors from disrupted endothelial cells. These tissue doctors causes systemic activation of coagulation cascade resulting in thrombin production, platelet activation and platelet fibrin clots formation. These microthrombi can cause local perfusion defects resulting in tissue hypoxia and organ dysfunction.
What is disseminated intravascular coagulation?
Disseminated intravascular coagulation is a condition in which blood clots form throughout the body’s small blood vessels. With fewer platelets and clotting factors in the blood serious bleeding can occur. DIC can cause internal and external bleeding, there is a problem of how to reduce the clotting in the microvascular while the patient remains at risk of serious bleeding.
What effects does sepsis have on the brain?
- Micro-clots: mini infarctions
- Reduced circulation (low bp)
- Damage from cytokines and other inflammatory mediators
The brain is one of the first organs to be affected.
Long term damage may occur: Impaired cognition
What effects does sepsis have on the heart?
Sepsis cardiomyopathy is due to circulating cytokines such as TNF Alpha and interleukin 1 beta, among others. This causes depression of cardiac myocytes and interference with their mitochondrial function.
Reduced cardiac output reduces perfusion of organs. Body responds by constricting small vessels in muscle/tissue to protect vital organs.
Because of the arterial and venous dilation induced by inflammatory mediators and consequent reduced venous return, a state of hypertension and distributive shock is produced by sepsis. There is dilation of all three component of the microvasculature, the arterials, venules, and capillaries. This is exacerbated by the leakage of intravascular fluid into the interstitial space because of loss of endothelial function induced by alteration in endothelial tight junctions.
Is septic cardiac myopathy reversible?
yes
What effects does sepsis have on the lungs?
Gas exchange across the alveolae is comprised as fluid and proteins leak into the lungs casing a drop in systemic oxygen saturation and a rise in carbon dioxide levels. The body attempts to compensate by increasing its respiratory rate, but the problem is ultimately compounded by increasing its respiratory rate. Meaning that even if oxygen rich air is present there is little blood flow in which gas exchange can take place.
What effects does sepsis have on the kidney?
Sepsis causes a decrease in effective intravascular volume resulting from systemic hypotension, direct renal vasoconstriction, cytokine release and neutrophil activation by endotoxins and other peptides which contribute to renal injury.
It is important for practitioners to appreciate that urine output is a fantastic window for assessing the patient circulatory system. If the urine output falls, it is likely that cardiac output has also fallen, and urgent action is required.
Acute kidney injury is common in sepsis and associated with worse patient outcomes, so it is therefore essential to monitor urine output closely.
What effects does sepsis have on the liver?
- Reduced cardiac output reduced perfusion.
- Liver enzyme rises.
- May reduce clotting factor production.
- Shock causes an increase in the body’s own noradrenaline and adrenaline production and an increase in cortisol. This stimulates the liver to produce more glucose, but cells are less able to take it up and use it.
What are the risk factors in sepsis?
- Impaired immunity:
o The very young (< 1)
o The elderly > 75years old
o Frail elderly
o Chemotherapy for cancer
o Diabetes
o Those without a spleen (Sickle cell/trauma)
o Long term steroids
o Immunosuppressants e.g. autoimmune diseases; transplant patients
- Recent surgery (< 6 weeks)
- Recent cuts/burns/blisters/skin infections
- IV drug misuse
- Indwelling lines or catheters
- Recently given birth / miscarriage / termination, particularly if have other risk factors for low immunity or recent contact with someone with confirmed group A strep
- Genetics: some people more susceptible
What are the pathogens & sources that can cause sepsis?
- Gram +ve or +ve bacteria
- fungal in immunocompromised patients
- Pneumonia - 50%
- Urinary tract - 20%
- Abdomen - 15%
- Skin, soft tissue, bone & joint - 10%
- others - 5%
Name 5 common pathogens in adults that can cause sepsis in adults
- Staph aureus
- Strep pyogenes
- Klebsiella spp
- E. coli
- Pseudomonas aeruginosa
