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DiMaio Lectures

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What is the difference between cause of death and mechanism of death?
1. COD: Injury/disease that produces physiological derangement resulting in death (e.g. gunshot wound, stab, coronary atherosclerosis, etc.)
2. MOD: Physiological derangement produced by cause (e.g. hemorrhage, septicemia, cardiac arrhythmia, etc.)
What factors are taken into account when estimating Time of Death?
1. Livor mortis
2. Rigor mortis
3. Body temp
4. Degree of decomposition
5. Chemical changes in vitreous
6. Stomach contents
7. Insect activity
8. Scene markers (most helpful factor!)
Livor mortis
Reddish purple coloration due to settling of blood by gravity in dependent areas of body (sometimes mistaken for bruising) - onset occurs 1/2 to 2 hours after death and maximal coloration occurs between 8 and 12 hours.
What is the difference between shift and fixed livor mortis?
"Shift" livor mortis is an intravascular collection of blood that can move from one area to another, whereas fixed livor mortis is blood that has hemolyzed and begun to diffuse into extravascular spaces (decomposition) - coloration will not move!
When does rigor mortis set in and in what order?
1. Onset 2-4 horus after death (fully developed within 6-12 hours)
2. Jaw, upper extremities, lower extremities (and decomposed in same order)
How does temperature affect rigor mortis?
1. Temperate climates - persists 36-48 hours
2. Hot weather - disappears in less than 24 hours
3. Cold weather - persists for several days
What is the problem with using body temperature as a determinant for time of death?
Not everyone has the same "normal" temperature, and different bodies cool at different rates (based on size, age, gender, clothing, surface, etc.).
What is the problem with basing time of death on vitreous potassium levels?
Time is not the only factor which affects rate of decomposition, which determines rise in potassium levels.
What are the characteristics of putrefaction?
1. Main cause of decomposition
2. Bacterial breakdown of tissue
3. GI tract is main source
4. Accelerated by hot environment and sepsis
5. Causes greenish discoloration in lower quadrants of abdomen
6. Green-black discoloration of face and neck (along with swelling, protruding eyes, tongue, decomposition fluid - purge fluid - from nose)
7. Body swells due to gas formation
8. Brain becomes porridge
9. Skeletonization
What is marbling of the skin?
Greenish black discoloration along blood vessels due to reaction of hemoglobin and hydrogen sulfide (skin color changes green then black)
Do medical examiners normally investigate natural deaths?
Not unless it was sudden or unexpected (especially if person was between 1 and 30 yo - unlikely to be natural).
What is the leading cause of death in men 20-65 yo?
Cardiovascular disease
What is the most common cause of sudden death medical examiners come across?
Coronary artery disease (75% of sudden deaths handled by medical examiners)
What are the most common anatomic findings in patients who die from coronary artery disease?
1. Severe coronary artery atherosclerosis (most common) - normally affects two vessels: LAD or left main
2. Myocardial scarring
3. rarely coronary artery thrombosis or myocardial infarct
What two things generally accompany hypertensive cardiovascular disease?
1. Cardiomegaly
2. Coronary artery atherosclerosis
What are the three categories of cardiomyopathy?
1. Congestive or dilated cardiomyopathy
2. Hypertrophic cardiomyopathy
3. Restrictive cardiomyopathy
What is normally the mechanism of death for natural cardiovascular deaths?
Cardiac arrhythmia
What are the five most common CNS natural causes of death?
1. Epilepsy
2. Intracerebral hemorrhage
3. Non-traumatic subarachnoid hemorrhage
4. Meningitis
5. Undiagnosed brain tumor
What are some clues that indicate death by epilepsy? What is the mechanism of death?
1. Person typically young and often found in bed
2. Complete autopsy generally negative and few detectable changes in brain
3. There may be anticonvulsants found
4. Bite wounds not a good marker
5. MOD: Cardiac arrhythmia
What is the most common cause of intracerebral hemorrhage, and how does it cause death?
1. Hypertension (other causes include amyloid angiopathy, AV malformation, tumors, bleeding diathesis, drugs, and vasculitis)
2. Death is due to secondary brain stem compression/herniation or intraventricular hemorrhage
What are the key signs that predict a nontraumatic subarachnoid hemorrhage?
There are non - 90% of cases are silent until rupture occurs
Which vessels are the most likely to rupture in case of nontraumatic subarachnoid hemorrhage?
80-90% of hemorrhages are found on the anterior portion of the Circle of Willis - death is rapid if not immediate
What percentage of sudden natural deaths is made up by respiratory causes?
Only 10%
What three main pulmonary diseases can result in sudden death?
1. Pulmonary thromboembolus (thrombus dislodges from lower extremities)
2. Bronchial asthma
3. Acute epiglottitis
What is the mechanism of death for a pulmonary thromboembolus?
Mechanical obstruction of pulmonary vasculature blocking the heart and vasoconstriction due to vasospasm in case of multiple small emboli.
What is the mechanism of death for bronchial asthma?
1. Reduced air flow with VP mismatch resulting in reduced oxygenation of blood/increased CO2 and right ventricular overload
2. Decreased air flow due to bronchial smooth muscle contraction
3. Intrabronchial mucus secretions
What is the mechanism of death for epiglottitis?
Edema of epiglottis and upper airway mucosa leading to mechanical obstruction of airway
What is the most common cause of epiglottitis?
Haemophilus influenza (or sometimes S. pneumoniae)
What are the four most common causes of death associated with pregnancy?
1. Ruptured ectopic pregnancy (hemorrhage)
2. Embolism (not as common as PE)
3. Pregnancy induced hypertensive complications
4. Infection
What are the five categories of intraoperative deaths?
1. Deaths due to underlying disease (not due to procedure)
2. Disruption of vital organ during procedure
3. Air embolism during surgery (most often during CNS, laminectomy procedure)
4. Anesthetic related deaths (usually overdose; allergic reaction RARE)
5. Cause of death cannot be ascertained
What factors can be used to date contusions?
1. Depth
2. Skin pigment
3. Location influence
4. Appearance
5. Time of onset (superficial bruises yellow sooner)
Note: It's hard to date contusions because people and bruises vary in coloration and Hg degredation. Also, there is no way to standardize terminology for describing bruises.
What should you look for when examining a laceration?
Presence of foreign material deposited by weapon or surface
What are hesitation marks?
Characteristic marks from self-inflicted incised wounds (you can see where person hesitated while cutting their self)
What are chop wounds?
Wounds produced by heavy instruments with a cutting edge (e.g. an ax) - most appear incised and combine cutting and crushing injuries.
What are the three "classic" signs of asphyxiation?
1. Visceral congestion
2. Petechiae (from increased IV pressure)
3. Cyanosis
What are the two types of asphyxial death?
1. Suffocation (smothering, choking, mechanical asphyxia)
2. Strangulation (closure of blood vessels and air passages of neck as a result of external pressure)
What are the three types of strangulation?
1. Hanging
2. Ligature strangulation
3. Manual strangulation
What is the mechanism of death for all forms of strangulation?
Cerebral hypoxia secondary to compression vessels supplying blood to brain (by compressing carotid or vertebral arteries)
What are the four cardinal features of a hanging victim?
1. Furrow on neck (where noose digs in)
2. Pale face
3. Protruding black tongue
4. Blood pools in dependent areas (Tardieu spots or punctate hemorrhages)
What is the difference between ligature and hanging strangulation?
Pressure on neck is applied by constricting band that is tightened by force other than body weight (virtually all homocides and same MOD as hanging)
What are the four cardinal features of ligature strangulation?
1. Face and neck markedly congested
2. Confluent scleral/conjunctival hemorrhages
3. Fine periorbital petechiae
4. Ligature mark encircling neck horizontally
What differentiates manual strangulation from the other two types?
There are generally marks of violence (abrasians, contusion, fingernail marks, etc.). There are also usually injuries to the internal neck (musculature hemorrhage, fracture of hyoid/thyroid in older patients, etc.).
How is SID syndrome diagnosed?
When there are no other apparent causes of death (diagnosis by exclusion)
What is the normal age range for SIDS?
2-4 months (92% less than 6 months)
What 5 things increase risk of SIDS?
1. Premature birth
2. When child is sleeping
3. Peak time is midnight or breakfast
4. Males
5. Temperature decrease
What is the difference between infanticide and neonaticide?
Infanticide: Killing of child 1st year
Neonaticide: Killing of child within 24 hours of birth (usually by young, unmarried mothers via smothering)
What are the three types of child homicide?
1. Classic battered child
2. Impulse or "angry" homicide (most child homicides)
3. Gentle homicide (smothering)
What are some key clues in identifying battered baby syndrome?
1. Significant discrepancy between history and clinical findings
2. Explanations of trauma vague/inconsistent
3. Head injuries from "falling out of arms, chair, etc." (yeah right)
4. Burns ("put hand in boiling water"_
5. Starvation ("fussy eater")
6. Often severe diaper rash ("tender skin", "allergic to everything")
What are the 4 main autopsy findings with battered baby syndrome?
1. Bruising/soft tissue hemorrhage
2. Death from head trauma w/ or w/o fracture
3. Retinal hemorrhage
4. Punched in abdomen (liver laceration, spleen rupture, tear mesentery)
What characterizes angry or impulse child homicide?
These make up most cases of child homicide and are generally characterized by a sudden violent act (throwing/slamming) triggered by a trivial provocation
What would you expect to find on autopsy after gentle homicide of child?
Nothing really - not much force is needed to smother a child so there is little evidence of trauma and the autopsy is typically unremarkable
What are two common methods in which mothers with Munchausen's Syndrome by Proxy harm their children?
1. They inject insulin into the kid to make him hypoglycemic
2. They prick the kid's finger and put blood in his urine
What is the main misconception about shaken baby syndrome?
Most people think death is due to breaking the baby's neck, but biomechanical studies and autopsies have shown that injuries to scalp and skull (contusions and fractures) are more commonly found in "shaken baby" syndrome, and it is virtually impossible to break a baby's neck from shaking it too hard. It is more likely that these parents are slamming the children against something hard, resulting in trauma to the head and neck.
What is the most common result of Shaken Baby Syndrome?
Retinal, subdural, and/or subarachnoid hemorrhage (but we think it may be due to trauma rather than shaking)
Why is it better to be shot by a handgun than a rifle?
When a bullet enters tissue, it generates a temporary cavity much larger than the permanent cavity. In higher velocity projectiles, injury can occur far from the path of the bullet, so tissue damage is more extensive. Think, when you shoot someone point blank their heads just explode, rather than shooting from far away and creating a nice neat hole.
What would you expect to find on autopsy of person killed by contact ballistic wound?
1. Scorching of wound edges
2. Soot in and around the wound
3. Muzzle impression (sometimes)
4. If over bone, stellate entrance wound
What would you expect to find on autopsy of person killed by near contact ballistic wound?
Entrance surrounded by wide band of seared blackened skin
What would you expect to find on autopsy of person killed by intermediate ballistic wound?
1. Powder tattooing
2. Soot present up to 12 inches for hand guns (can wipe off)
What would you expect to find on autopsy of person killed by distant ballistic wound?
1. No soot or tattoing (unlike intermediate)
2. Hard to determine exact range of weapon
3. Entrance wound with abrasion ring
4. Small, circular, or oval entrance
How are exit wounds different from entrance wounds?
1. Larger and more irregular
2. No abrasion ring
How do high velocity rifle wounds differ from handgun wounds?
1. External injuries to torso look the same, but severe internal injury is more common
2. Temporary cavity may fracture bone, injure vessels and organs far from bullet
3. Possible micro-tears around entrance
4. "Lead snowstorm" - shed lead that goes through body