Hemodynamics, Death and Autopsy

Hemodynamics

• Hydrostatic Pressure:

  • Pressure exerted by water.

  • Pushes water out of a system.

• Oncotic Pressure:

  • Draws water into a system.

• Fluid Distribution:

  • Hydrostatic and oncotic pressures balance fluid in blood and interstitium.

• Forces at Play:

  • Hydrostatic pressure from blood and interstitium.

  • Oncotic pressure from blood and interstitium.

• Equilibrium:

  • In blood vessels, hydrostatic pressure pushes fluid out, while oncotic pressure pulls it in.

  • Ideally, these forces cancel out to maintain fluid within the vessel.

  • In the interstitium, hydrostatic pressure pushes fluid into the blood vessel, while oncotic pressure draws fluid out.

  • These forces balance to maintain fluid in the interstitium.

• Derangements:

  • Imbalance in hydrostatic and oncotic pressures leads to fluid leaks or shifts, causing edema and effusion.

Edema and Effusion

• Edema:

  • Accumulation of fluid in tissues.

• Effusion:

  • Accumulation of fluid in body cavities (pleural, pericardial, peritoneal).

Mechanisms and Examples of Effusion

• Increased Hydrostatic Pressure:

  • Seen in heart failure, where the heart's inability to pump effectively increases venous pressure.

  • This leads to fluid accumulation in veins and subsequent leakage into tissues, causing edema.

• Decreased Oncotic Pressure:

  • Oncotic pressure depends on protein concentration, especially albumin.

  • Conditions like malnutrition, nephrotic syndrome, and liver cirrhosis reduce protein levels.

  • Reduced oncotic pressure leads to fluid leaking into body cavities and tissues.

• Increased Vascular Permeability:

  • Damage to blood vessels (e.g., burns) or inflammation (e.g., infections) increases permeability.

  • In burns, severe damage to blood vessels causes widespread edema.

  • Infections trigger an inflammatory response with cytokines that act as vasodilators, leading to fluid leakage.

• Lymphatic Obstruction:

  • Compromised lymphatic system prevents fluid reabsorption, leading to edema.

• Sodium and Water Retention:

  • Renal diseases and renal hyperperfusion cause excess sodium retention.

  • Water follows sodium, leading to edema (e.g., puffy face or eyes).

Transudate vs. Exudate

• Transudate:

  • Caused by abnormalities in hydrostatic and oncotic pressures (Starling forces).

• Exudate:

  • Caused by increased vascular permeability.

• Light's Criteria:

  • Used to differentiate transudate from exudate.

  • Involves measuring lactic dehydrogenase (LDH) and protein levels.

  • If the ratio is greater than 0.5, it suggests exudate.

Morphology of Edema and Effusion

• Common Sites:

  • Subcutaneous tissues, lungs, and brain.

• Subcutaneous Tissue:

  • Dependent edema: Influenced by gravity.

  • Pitting edema: Depression from pressure due to displaced interstitial fluid.

  • Periorbital edema: Around the eyes, common in renal failure.

• Lungs:

  • Effusion causes lungs to become heavy (two to three times normal weight).

  • Biopsy shows frothy, blood-tinged fluid.

• Brain:

  • Effusion narrows sulci and flattens gyri.

• Body Cavities:

  • Hydrothorax: Fluid in the pleural area.

  • Ascites: Fluid in the peritoneum.

  • Hydropericardium: Fluid in the pericardium.

• Microscopic Appearance:

  • Clearing and separation of the extracellular matrix.

  • Subtle cell swelling.

  • Separation of the basement membrane and dermis.

Hyperemia and Congestion

• Hyperemia:

  • Active process involving arterial dilatation.

  • Tissues appear reddish due to increased blood flow.

  • Example: Hyperemic tonsils.

• Congestion:

  • Passive process involving reduced outflow of blood from a tissue.

  • Can be localized or systemic.

  • Tissues appear bluish or darker.

  • Examples:

    • Pulmonary congestion (lungs).

    • Hepatic congestion (liver).

Hemostasis and Thrombosis

• Hemostasis:

  • Formation of blood clots at sites of endothelial injury.

  • Involves endothelium, platelets, and coagulation factors.

  • Endothelium and platelets: Primary hemostasis.

  • Coagulation factors: Secondary hemostasis.

• Steps in Hemostasis:

  • Vasoconstriction.

  • Platelet plug formation.

  • Stabilization of the platelet plug by coagulation factors.

  • Thrombotic and antithrombotic events.

• Secondary Hemostasis:

  • Involves coagulation factors triggered by a damaged surface or trauma.

  • Intrinsic System: Initiated by glass surfaces, damaged surfaces, negatively charged surfaces that activate factor 12 into factor 12a, which then in turn activates factor 11 and factor 10.

  • Extrinsic System: Involves factor 7 combining with factor 3 (ultimately, the intrinsic and extrinsic pathways meet at factor 10).

  • Both pathways activate factor 10, which then activates prothrombin into thrombin.

  • Thrombin activates fibrinogen into fibrin, forming a fibrin glue around the platelet plug to enhance the adhesion.

  • Factor 13 enhances this gluing effect, creating a cross-linked fibrin clot.

Thrombosis

• Thrombus:

  • Pathologic formation of a clot.

• Virchow's Triad:

  • Endothelial injury.

  • Abnormal blood flow.

  • Hypercoagulability.

• Hypercoagulability Examples:

  • Obesity (increased cholesterol).

  • Female menopause (decreased estrogen).

• Morphology of Thrombosis:

  • Occurs anywhere in the cardiovascular system.

  • Composed mainly of fibrin, platelets, red cells, and inflammatory cells.

• Lines of Zahn:

  • Laminated appearance due to alternating pale platelet and fibrin deposits and darker red cell-rich layers.

  • Characteristic of antemortem thrombi (formed in flowing blood).
    *Clinical Importance:

  • Useful to see if the clot has formed post or antimortem

Fate of Thrombus

• Propagate: Accumulate more material.

• Embolize: Travel to other parts of the body.

• Dissolve: Rapid shrinkage and disappearance.

Embolism

• Embolism:

  • Thrombus travels through the bloodstream and causes obstruction or damage.

  • Can cause infarction, organ failure, and death.

• Mechanisms of Injury:

  • Mechanical injury (obstruction).

  • Biochemical injury (inflammatory response).

Types of Embolism

• Pulmonary Embolism:

  • Involves the lungs, causing pulmonary hemorrhage and impaired gas exchange.

  • Can lead to heart failure or sudden death.

• Systemic Thromboembolism:

  • Most common source is mural thrombi in the atria and ventricles.

  • Often affects lower extremities, leading to ischemia, gangrene, and amputation eventually.

• Fat Embolism:

  • Often due to bone fractures, releasing fat from bone marrow into the bloodstream.

  • Fat cells disrupt blood flow.

• Amniotic Fluid Embolism:

  • Amniotic fluid or fetal tissue enters maternal circulation during labor or postpartum.

  • Induces inflammatory reaction and activates the immune system, leading to systemic effects.

• Air Embolism:

  • Air enters the bloodstream, potentially causing obstruction.

  • Requires a significant amount of air to cause symptoms.

Decompression Sickness

• Diving to rapid ascent causes gasses to expand the lungs, leading to bends and chokes

Shock

• Shock:

  • Diminished cardiac output or reduced effective circulating blood volume impairs tissue perfusion, leading to cellular hypoxia. (aka low blood sugar)

• Types of Shock:

  • Cardiogenic: Heart fails to pump effectively, leading to generalized tissue ischemia.

  • Hypovolemic: Massive bleeding or fluid loss reduces blood volume.

  • Septic Shock: Systemic inflammation due to infection causes vasodilation and fluid leakage.

  • Anaphylactic Shock: Severe allergic reaction causes vasodilation and respiratory distress.

Death and Autopsy

Definition of Death

• Cessation of cardiopulmonary functions and/or brain activity (Organ Donation Act of 1991).

Life vs. Death

• Life: Sum total of vital processes that maintain physical integrity.

• Death: Termination of life marked by complete and irreversible cessation of all vital functions.

• Dying: Continuous process leading up to death.

Medical Legal Aspects of Death

• Civil personality is extinguished.

• Rights and obligations are transferred (inheritance).

• Partnership dissolution.

• Extinguishment of legal agency.

• Criminal liability is extinguished.

• Civil cases are dismissed.

Brain Death Criteria

• Deep, irreversible absence of electrical activity in the brain.

• No universally accepted criterion.

• Harvard Criteria:

  • Unreceptivity and unresponsiveness.

  • No movements or breathing.

  • Absence of reflexes.

  • Flat EEG.

• Philadelphia Protocol:

  • More specific clinical criteria.

  • Complete lack of responsiveness.

  • No spontaneous breathing for at least three minutes while breathing room air.

  • Generalized muscular laxity.

  • Falling arterial blood pressure.

  • Isoelectric EEG.

Reflex Testing in Brain Death

• Pupils: Fixed, dilated, and nonreactive.

• Corneal reflex: Absent.

• Airway stimulation: No response.

• Cold caloric test: No eye movement.

• Deep tendon reflexes: Absent.

• Superficial reflexes: Absent.

Cardiorespiratory Death

• Reliance on signs like absence of pulse and unresponsiveness.

• Commonly accepted by physicians and family based on intuition or practical judgement.

Kinds of Death

• State of Suspended Animation: Temporary loss of vital functions that can be potentially restored.

  • Severe illness (uremia).

  • Electrical shock.

  • Cataplexy (sudden loss of muscle control).

• Lazarus Phenomenon: Delayed return of spontaneous circulation (ROSC) after CPR has been stopped.

Signs of Death

• Cessation of Heart and Circulation:

  • Palpation of pulse.

  • Auscultation of heart sounds.

  • Peripheral Circulation Tests: Magnus test, I cards test, diaphanous test, application of heat.

• Assessment of Respiration:

  • Visual observation of chest movement.

  • Auscultation of breath sounds.

  • Mirror test, fiber test, glass of water test.

• Algor Mortis (Cooling of the Body):

  • Gradual cooling of the body after death.

  • Postmortem caloricity (initial increase in body temperature).

  • Can be used to estimate the time of death.

• Changes of the Skin:

  • Pale, waxy appearance.

  • Linear mortise (livid discoloration).

  • Postmortem contact flattening.

  • Opacity of the skin.

• Postmortem Lividity (liver Mortise):

  • Blood pools in dependent parts of the body due to gravity.

  • Starts around three to six hours postmortem and fully develops around twelve hours.

    • Indicates Body Position after Death

    • Estimate the Time of Death

    • Bright Pink = Carbon Monoxide

    • Bright Red = Snow or Ice

    • Coffee Brown = Potassium Chlorate

    • Unnaturally dark = Strangulation

• Changes in the Eyes:
  *Loss of Corneal Reflex
  * Eyes Fixated and Dilated
  *Flash Noir

• Muscular Changes:
  * Period of Muscular Irritability

• Postmortem Rigidity (Rigor Mortis):

  • Progressive stiffening of the muscles after death due to ATP depletion.

  • Occurs due to depletion of ATP
    -With the depletion of ATP, the muscles become locked, leading to contracting.

    • Tropical/Cold Countries - Lasts 28 to 48 Hours
      *Summer/Hot Weather - Last around 18 to 16 Hours

  • Heat stiffening: Coagulation of muscle proteins due to exposure to high temperatures.

  • Cold stiffening: Solidification of fats and fluids of the body.

  • Cadaveric spasm: Sudden stiffening of muscles at the moment of death due to extreme stress.

Putrefaction (Decomposition)

• Breakdown of complex body proteins into simpler substances.

• Involves foul-smelling gas production, discoloration of tissues, and liquefaction of the body.
  *Color Changes: Greenish to Black coloration on the right iliiac fossa
  *Marbling - Web pattern from expansion
  *Gas Formation - Bacteria begin to dissolve the bodies tissues creating gas formation and eventual bloating

• Special Modifications of Putrefaction:

  • Mummification: Extreme dehydration of the body.
    Artificial and Preservation methods
    Egypt Mummification

  • Saponification: Body fat transforms into a waxy, soap-like substance.

  • Maceration: Occurs in a fluid medium, leading to softening, peeling, and breakdown of fetal tissues (e.g., dead fetus in utero).

Presumption of Death and Survivorship

• Occurs if a catastrophic happens and no body has been recovered

• Presumption of Death: *10 Years Before Sucsession and Testiment

  • Occurs when a person has been missing under certain circumstances.
    (Four), if the person went missing during war from a ship or plane
    (Seven), other missing circumstances

• Presumption of Survivorship:
  -if multiple people are in the same boat, the determination of death affects inheritance
  *Age based determination - Depends on if <15, 15-60, or >60
  Medical Legal Examination of death - There are medical officers and individuals that can have the right to investigate.
  There are 5 individuals listed from judges to prosecutors

*When can an autopsy be perforemed - There can either be an electrive or a mandatory autopsy
Elective - Based on the approval of the next to kin of the body
Mandatory - The medical office holds the body and has the permission to work on the body.
Virchow Method - the bodies organs are removed individually to examine one by one
Rokitansky Method - Ensitue examination of the body to maintain its organic relationships.
Ghon Techniqu - Organs of the body are looked at in three blocks to maintain systematic integrity
Leutel Technique - Organs are removed at random in the body.
Manner of Cut: Y shape and Straight Cut Imcision

• Y Shape- begins in the shouler and goes down to the Crotis

  • straight Cut - begins at the Suprasternal notch and goes down to the pubis.

Violent Manner ofDeath - Accident, Suicide, Homocide and SIDS

Conclusion:

Guidelines in performing autopsy:
* must be a pathologist
* perform competently
*Body must be presented in the shape it came
Types of findings:

    (Negative) when the autopsy is completed properly and the test is still negative.
   (Negligent) improper preperation

Categories:
* Primary = Immediate
Secondary = After an extended period

Mechanism:
* Hemorrhlogic
* Metabolic
*Tamponade
*Death certified (If you can find COD, then state "Undetermined")