Asphyxia and Drowning - PDF

Asphyxia Dr. Isam ELHASSAN  Asphyxial Deaths It means lack of oxygen. Although literally it means absence of pulsation. Any thing that interferes with oxygen transfer can called asphyxia  Types of hypoxia (anoxia) 1.Hypoxic hypoxia. 2.Anemic hypoxia. 3.Stagnant hypoxia....

Asphyxia Dr. Isam ELHASSAN  Asphyxial Deaths It means lack of oxygen. Although literally it means absence of pulsation. Any thing that interferes with oxygen transfer can called asphyxia  Types of hypoxia (anoxia) 1.Hypoxic hypoxia. 2.Anemic hypoxia. 3.Stagnant hypoxia. 4.Histotoxic hypoxia. ❖Anoxic (hypoxic) Anoxia: ❑ Ambient: due to decrease oxygen content in the atmosphere as in cases of: A- High altitudes. B- Presence of irrespirable gas (Co2, Co, N2,…). ❑ Central: due to depression of respiratory center as in cases of: A- Central depressants as barbiturates. B- Medullar herniation. C- Electric shock. ❑ Peripheral: due to paralysis (muscle relaxants overdose, botulism,…) or spasm (strychnine poisoning,…) of respiratory muscles. ❑ Mechanical (violent asphyxia): A- Occlusion of respiratory openings (smothering). B- Occlusion of respiratory passages in the neck (strangulation, throttling, hanging). C- Prevention of respiratory movements (traumatic asphyxia). D- Internal airway obstruction by foreign body (chocking) or water (drowning). ❖ anemic anoxia: It is the decreased oxygen carrying capacity of blood due to : - Abnormal hemoglobin ( COHb in CO poisoning or methemoglobin in nitrates toxicity). - Massive blood loss ( massive hemorrhage). - Hemolysis ( arsine gas toxicity , incompatible blood transfusion etc.) ❖ Stagnant Anoxia : (stagnant hypoxia ) It is the reduction of the oxygen delivery / unit time due interference with flow of blood to the tissues as in: - Advanced heart failure. - Vagal or histaminic shock. ❖ Histotoxic anoxia: (Histotoxic hypoxia ) It is diminished ability of cells to utilize oxygen as in: - Cyanide poisoning. - Exposure to extreme cold.  Asphyxial Deaths There are different levels of asphyxia from outwards inwards include the followings: Absence or reduction of oxygen tension in the external atmosphere Obstruction of the external respiratory orifices, smothering or gagging Blockage of the internal respiratory passages  Restriction of the respiratory movements of the thorax as traumatic asphyxia Diseases of the lungs that prevent or reduce gaseous exchange e.g. pulmonary oedema Reduction in cardiac function leading to impaired circulation of oxygenated blood, stagnant anoxia Reduced ability of the blood to transport oxygen as in severe anaemia, Inability of the tissue cells to utilize oxygen as cynide poisoning ❖ Stages of mechanical or violent asphyxia 1- stage of dyspnea : - it is a physiologic response to hypoxia leading to stimulation of respiratory center. - Clinical picture : dyspnea ( forced expiration then forced inspiration ). The victim appears apprehended, irritable, gasping and the lips are blue. 2- stage of convulsions : - Cerebral irritation occurs due to anoxia and CO2 accumulation. - Clinical picture : cyanosis, constricted pupils, hypertension, convulsions loss of consciousness, the tongue is protruded and the eye balls are prominent. - The elevated blood pressure affect the fragile capillaries ‘ due to anoxia’ leads to rupture of capillaries and petechial hemorrhages as subpleural or subpericardial known as ‘Tardieu Spots’.  This petechail hemorrhages are also found in the respiratory passages, meninges, subconjunctival and even all over the face. - Convulsions increase intraalveolar pressure leading to rupture of the unsupported subpleural alveoli, glistening air bubbles under the pleura called ‘Silvery Spots’. 3- stage of irregular breathing : Clinical picture : loss of consciousness with: - Irregular breathing ‘cheyne-stokes respiration’. - Cyanosis becomes deeper. - Dilated fixed pupils. - Hypotension, weak rapid pulse, arrhythmias. - Flaccidity of muscles and loss of reflexes. - Death occurs about 5 minutes.  Classical Signs of Asphyxia: Petechial Haemorrhage: Small pin-point collections of blood lying in the skin, sclera, conjunctivae and under thoracic serous membranes Vary in size from millimeters to 2 cm. Tardieu’s spots other term used to indicate petechial haemorrhages, it should be restricted to those laying in the visceral pleura Are not due to rupture of capillaries (bleeding from capillaries is rather microscopical) actually bleeding comes from small venules  Congestion and Oedema: Congestion of the face, lips and tongue become swollen and reddened. Internal organs also become congested. Cyanosis : Depends on the absolute amount of reduced haemoglobin rather than the proportion of reduced Hb/Oxy Hb.  Suffocation Usually refers to a death caused by reduction of the oxygen concentration in the respired atmosphere e.g cabin failure of aircraft at high altitudes, in fires  Smothering Mechanical occlusion of the mouth and nose, Examples include; Overlaying of infants. SIDS( sudden infant death syndrome) or cott death. Plastic bag suffocation.  Chocking Blockage of the internal airways usually between the pharynx and the bifurcation of the trachea. Death may be due to: Pure asphyxia, where we found petechae and congestion. Neurogenic cardiac arrest – sudden death in which no signs of asphyxial death can be detected on autopsy examination.  Causes: Foreign bodies. Denture and haemorrhage. Acute obstructive lesions. Diphtheria and Haemophilus influenzae epiglottitis in children. Aspiration of vomitus as in acute alcoholism.  Traumatic Asphyxia Mechanical fixation of the chest. Occurs in: Chest and the abdomen are compressed by a substance or an object Crushing in crowds  Postural asphyxia in which the person remains in a certain position for an extended time. Either due to being trapped or being in a drunken or drugged state which prevents adequate respiratory movements and impair normal venous return to the heart, as in person trapped upside down  Fatal pressure on the neck Fatal pressure on the neck is common in forensic practice. Mechanism of death in pressure on the neck:- Airway occlusion, direct compression. Occlusion of the neck veins Compression of the carotid arteries vagal cardiac arrest  Manual Strangulation (Throttling) A common method of homicide Commonly seen in domestic homicide when a husband kills his wife, in sex related murders again the victim is a woman, and in child killing. Manual strangulation is rarely committed by a woman except on a child and a man rarely kills another man of equal physique by manual strangulation.  Autopsy findings : Bruising and abrasions on the neck. Bruising discoid marks Bruising scratches, finger-nail marks, linear scratches Fractured hyoid bone and superior thyroid horn (more common).  Strangulation by Ligature Most ligature strangulations are homicidal. Pressure on the neck may be affected by constricting all or part of the circumference of the neck by a ligature. The ligature mark tends to encircle the neck horizontally and at a lower level compared to hanging. Often there is a cross over point. Fracture of the hyoid bone is lesser compared to manual strangulation.  Hanging A form of ligature strangulation in which the force applied to the neck is derived from the gravitational drag of the weight of the body or part of the body. Judicial Hanging : - Here is a use of a drop effected suddenly by arrested, the cervical spine would be dislocated resulting in traction on the spinal cord with consequent spinal cord or brain stem disruption.  complete hanging where the body is completely suspended, feet are not touching the ground. incomplete hanging where the feet are touching the ground. Hanging marks : - Never completely encircles the neck, unless a slip-knot was used. Point of suspension is indicated by a gap in the skin mark. Situated higher on the neck than in strangulation.  Most hangings are suicidal. Accidental hanging can occur in ; Sexual asphyxia; auto-erotic or masochistic practices. In children TYPE OF SUSPENSION IN HANGING a) complet e b) partial Typical hanging : the term is applied when the point of suspension is placed centrally over the occiput. A typical hanging : is referred to other position of the point of suspension (front or either side of the neck). the head is bent to the opposite side of suspension.  Drowning The entry of air into the lungs is prevented by water or other fluid due to submersion of mouth and nostrils  Incidence of Drowning: - Accidental: - commonest form, seen among fishermen, bathers, dock workers and epileptics. Suicidal: - fairly common especially among females. Homicidal: - rare form of death.  Pathophysiology of Drowning: - Inhalation of water in drowning is followed by its absorption into circulation through alveolar membrane, leading to electrolytes imbalance and other concomitant results, which occurs within few minutes of submersion. It is claimed that the victim while die within 2-5 minutes of complete submersion as asphyxia supervenes within 2 minutes and heart function stops next 2-5 minutes.  Mechanism of Death : - In fresh water drowning: - Large quantity of water cross alveolar membrane leading to haemodilution + overload of circulation haemolysis hyperkaleamia ventricular fibrillation and death within 4-5 minutes. Salt water drowning: - Water is hypertonic will draw water to lungs severe oedema of lung, which followed by haemoconcentration, hypovolaemia and shock then asphyxia (death within 10-12 minutes) ❖ Phases of drowning: Submersion is followed by struggle which subsides with exhaustion and drowning begins. Breath holding lasts until carbon dioxide accumulation stimulates respiration resulting in inhalation of water. Gulping of water coughing and vomiting is rapidly followed by loss of consciousness. Profound unconsciousness and convulsions are associated with involuntary respiratory movements and the aspiration of water. Respiratory failure precedes heart failure in one-third of cases it is coincident in one-third and follows it in the other third. Death occurs within 2 to 3 minutes. Death is almost invariable when the period of submersion exceeds 10 minutes. The survival rate from potentially fatal salt water submersion is about 80% whereas in fresh water it is less than 50%.  Postmortem findings in drowning : congestion of the face and conjunctivae. fine froth ( blood stained) coming from the nose and the mouth. When remover it comes again, it is due to mixture of water and air in the presence of the surfactant substance. cutis anserina ( goose skin), orange peal skin. Washerwoman’s hands, wrinkling of the hands due to long immersion in water.  Hands holding grass or mud lungs are pale, grayish, voluminous, edematous Stomach contains water, mud and algae Diatom test is positive. This test is useful in differentiating true drowning from immersion. Throwing bodies into water is a common way of hiding crimes. In this test the presence of diatoms( silica containg algae) in the bone marrow samples as takes as indication of true drowning. Diatom as seen under the microscope. the test depends on the fact that, silica coat of this unicellular algae resist digestion by strong acids. In the test the bone marrow sample is treated by strong acid and examined under the microscope.  ❖ Mechanisms of death in drowning: I. Direct causes. II. Indirect causes. III. Secondary drowning (post-immersion syndrome) I. Direct causes: Immediate death: 1- Mechanical anoxia: due to filling of the respiratory passage with water. 2- Hypothermia: from cold water. Death after recovery from water: 1- Hydremia &hemolysis: hypotonic fresh water → hemodilution (the blood volume increase by 50% → hypotonic plasma → hemolysis of RBCS. 2- Electrolyte imbalance: ▪ Fresh water → ↓Na + ↑K (release of potassium from hemolysed RBCs)→ ↓BP. & V.F. ▪ Sea water → ↑Na → ↑BP & cardiac failure. 11- Indirect causes: Give PMP other than that of drowning (Atypical drowning): 1- Reflex cardiac inhibition: due to vagal stimulation: ▪ Sudden rush of cold water in nasal sinuses. ▪ Water whip on trigger zone. 2- Head or other traumatic injuries as in striking solid objects. 3- Dry drowning: in sensitive persons, exposure to cold water→ severe laryngeal spasm→ asphyxial death before entrance of water. 111- Secondary drowning (post-immersion syndrome): The victim survive the episode of submersion and suffers from restlessness, increasing pulse and respiratory rate, pain in the chest, cough and cyanosis (a picture of acute pulmonary edema). The case ended fatally if untreated. Later complications include pneumonitis, broncho-pneumonia and hyaline membrane disease.