Circulatory and respiratory factors in the experimental production of lung petechiae and their possible significance in the sudden infant death syndrome.

This study investigated the production of lung petechiae by 4 modes of death in anaesthetized rabbits: (i) apnoeic asphyxia from rapid intravenous overdose of pentobarbitone; (ii) obstructive asphyxia from 3 episodes of tracheal occluson (2 min, 2 min, 4 min); (iii) hypotensive insult from intra-cardiac electrocution, producing hypotension and death in 30-80 s; (iv) hypertensive insult from rapid intravenous noradrenaline, terminating in fatal cardiac arrhythmia (1.2-6.8 min). A single fatal episode of apnoeic asphyxia did not produce any petechiae. In contrast, many lung petechiae resulted from the repeated obstructive apnoeic episodes. These results confirmed previous work. However, petechiae were not confined to these asphyxial forms of death. They also occurred in hypotensive or hypertensive circulatory deaths, with or without gasping.. The peak level of systemic hyprtension, in the obstructive asphyxia and hpertensive experiments, did not correlate with the numbers of lung petechiae. Pulmonary oedema, confirmed microscopically, occurred in most animals except those in the apnoeic asphyxial group. The number of lung petechiae increased significantly (P < 0.025) with the severity of pulmonary oedema, defined by the index % lung/body weight. In future research, the aetiology of petechiae needs to be evaluated in terms of circulatory pressures as well as of respiratory factors.