Mechanisms of Disease Flashcards
(127 cards)
Exudative pus if HIGH ? LOW ? on pleural tap
Lights criteria for exudative pleural fluid
High acid, LDH, protein >35g/L
Low Glucose
Pleural protein: Serum protein ratio >0.5
Pleural LDH: Serum LDH ratio >0.6
Pleural LDH > 2/3rd of serum LDH
Exudative pus seen in
Local disease (High protein). Local factors influence the accumulation or clearance of fluid
Malignancy
Infection
Transudate <25g/L seen in
Systemic disease (Low protein <25g). Imbalance between oncotic and hydrostatic pressures
HF
Hypoalbuminaemia
Meig’s syndrome (Ascites, pleural effusion, ovarian tumour)
Bacteria that don’t gram stain
Chlamydia
TB - use Ziehl-Neelsen (Mantoux +ve when vccinated, IGRA -ve if vaccinated)
Bacteria that gram stain positive
Strep pyogenes + pneumoniae Staph aureus (coagulase +)
Bacteria that gram stain negative
E.coli
Neisseria Meningitides
Penetrance is
Expressivity is
Penetrance is how many develop it
Expressivity is how it manifests
This genetic test only detect gains and losses of chromosomes such as in Downs
Virtual karyotyping
Which genetic test can highlight subtle alterations to chromosomes
FISH Williams syndrome (7q11.23 deletion) - congenital heart disease, periorbital fullness, long smooth philtrum, super happy
Which test takes DNA sample and compares genes to a control to detect mutations
Microarray-based Comparative Genomic Hybridization (aCGH)/DNA sequencer
What tests for - Tumour markers e.g. AFP
Antibody-based: Immunohistochemistry
Trauma investigation after car crash with suspected subdural
CT SCAN or MRI
Pathophysiology of haemorrhage
- Increased sympathetic response - constriction and inotropy - due to reduced pressure detected by arterial baroreceptors
- Adrenaline and cortisol released
- Reduced renal perfusion - RAAS activated - more Na thus water retention
Early trauma induced coagulopathy
- Severe hemorrhage diminishes o2 delivery and causes hypothermia this in turn halts the coagulation cascade, preventing the blood from clotting (coagulopathy).
- In the absence of blood bound o2 and nutrients due to hypoperfusion, the bodys cells burn glucose anaerobically for energy, causing the release of lactic acid, ketone bodies, and other acidic compounds into the bloodstream, which lowers the bloods pH, leading to metabolic (acidosis).
- This increase in acidity damages the tissues and organs of the body and can reduce myocardial performance, further reducing oxygen delivery and thus (hypothermia).
How does mild acidosis help during trauma
Helps unload oxygen at the peripheral tissues
What tests and what results during trauma
ABG - acidosis, low HCO3- as its used up (low base excess), low CO2 as patient blows off CO2 to compensate for acidosis
HB - Low
Lactate - High due to anaerobic respiration
Treat trauma bleeding with
1Whole blood (all the clotting factors etc)
Resus would only dilute clotting factors
Pathophysiology of Disseminated Intravascular Coagulation
- Vascular damage/cytokines expose TF
- TF stats extrinsic pathway > Thrombin + Fibrin
- Excesss Thrombin cleaves fibrinogen into fibrin resulting in clots which trap plateletes (thrombocytopenia)
- Fibrin degradation prodcuts convert plasminogen into plasmin = fibrinolysis
Tissue factor builds up clots of fibrin and traps platelets (low platelets) AND then plasminogen in converted into plasmin to counteract the clotting thus bleeding occurs.
PT test is which pathway and which conditions result in prolonged time
Extrinsic
Vit K def (2, 7, 9 and 10) or Warfarin use (7)
APTT test is which pathway and which conditions result in prolonged time
Intrinsic Von WIllebrand (often comes with reduction in factor 8), Hemophilia A (factor 8), Hemophilia B (factor 9), Hemophilia (factor 11) or Heparin use (activates anti-thrombin which inhibits factor II, IX, X and XI) or Lupus anticoagulant (actually prothrombotic in vivo, but prolongs aptt time when tested in vitro)
Bleeding time refers to
Platelets thus Thrombocytopenia if prolonged
Haemorrhage and DIC: After excessive activation of coagulation runs out fibrinolysis occurs, what is used to treat this
Tranexamic acid (prevents plasmin from degrading fibrin)
Cerebral perfusion pressure = BP - ICP
What happens as ICP increases
as ICP increases, CPP decreases, body responds by raising BP and dilating cerebral blood vessels = increased cerebral blood volume thus even higher ICP! Vicious cycle!
How to compensate for high ICP
Brain empties CSF from ventricles into spine and into venous blood