Characterization of successful and failed autoresuscitation in human infants, including those dying of SIDS

Abstract

Our purpose was to identify and further characterize physiologic mechanisms relevant to autoresuscitation from hypoxic apnea in infants dying suddenly and unexpectedly. We studied cardiorespiratory recordings of 24 infants (age range, 0.8-21 months) who died suddenly while being monitored at home. These recordings were analyzed for features indicated by studies in animal models to be characteristic of hypoxic gasping, and of recovery from bradycardia and apnea associated with gasping (e.g., autoresuscitation). Findings in 5 infants diagnosed as having sudden infant death syndrome were compared with 6 non-SIDS infants whose deaths resulted from other conditions. Additionally, we studied 15 healthy infants during sleep, using home monitor and other respiratory recording techniques, in order to obtain comparison data. We found in recordings from 23 of 24 subjects that hypoxic gasps with characteristic features occurred immediately preceding death. A unique pattern of complex, closely spaced gasps ("double" or "triple" gasps) was present in many subjects. Evidence of partially successful autoresuscitation closely following one or more gasps occurred in 11 subjects, while another 4 had evidence of complete autoresuscitation with return of normal heart rate and resolution of apnea on one or more occasions. Significant differences between SIDS infants and those dying from other causes included increased occurrence of complex gasps and decreased occurrence of partial or complete autoresuscitation in the SIDS infants. The non-SIDS cases were different from the SIDS cases in that only one had "double" gasps (n = 7), while none had "triple" gasps, as compared with 4 out of 5 SIDS cases with these patterns (P < 0.05, chi-square). Also, in contrast with the SIDS cases, more of the cases with specific postmortem diagnoses had evidence of partial (5 out of 6 cases) or complete (1 out of 6 cases) autoresuscitation (P < 0.05, chi-square). We conclude that partial or complete autoresuscitation by gasping is not uncommon in moribund infants during the first year of life. Failure of autoresuscitation mechanisms other than failure to initiate gasping may be characteristic of infants dying of SIDS. Some SIDS infants appear to be different from infants dying with other diagnoses with respect to efficacy and characteristics of hypoxic gasping.

Proposal for mechanisms of protection of supine sleep against sudden infant death syndrome: an integrated mechanism review

“…A period of compensatory tachycardia usually follows successful autoresuscitation. It is likely that such AAEs occur in many normal healthy infants (57), but in these, autoresuscitation is effective in restoring normal breathing, heart rate, and blood pressure, see Figure 2.…”

Potential Asphyxia and Brainstem Abnormalities in Sudden and Unexpected Death in Infants

“…3,11,12 The association of unsafe sleep environmentswith SIDS raises the possibility that normal infants die of asphyxia and that eliminating these dangerous sleeping conditionswill in turn eradicate all SIDS deaths. Yet there is mounting evidence that at least some infants who die of SIDS are not "normal" before death but rather have underlying vulnerabilities, 5,[13][14][15][16][17][18][19][20][21][22][23][24][25][26] including genetic susceptibilities, 27 that put them at risk.…”

Possible Role or Respiratory Pacemaker Neurons in the Generation of Different Breathing Patterns

“…Second, hypoxia renders the respiratory network more vulnerable to the blockade of a single ionic mechanism: namely, the persistent Na + current (Peña & Ramirez 2002;Tryba et al 2006). Gasping is an important autoresuscitation mechanism that seems to fail in victims of sudden infant death syndrome (SIDS, Poets et al, 1999;Sridhar et al, 2003). Consistent with a change in configuration of the respiratory network, SIDS victims breathe normally during normoxia, but do not gasp effectively when exposed to hypoxic conditions (Poets et al, 1999;Sridhar et al 2003).…”

“…Indeed, failure to respond to severe hypoxia via gasping and autoresuscitation can result in death. Thus, dysregulation of the generation of gasping rhythm and/or autoresuscitation has been hypothesised to contribute to Sudden Infant Death Syndrome (SIDS; Poets et al, 1999;Sridhar et al, 2003;Peña, 2009). Breathing is commanded and regulated by the respiratory centres of the brainstem (Richter, 1982;Bianchi et al, 1995;Feldman, 1995).…”

“…Ventilation of the lungs as consequence of rhythmic contractions of the respiratory muscles constitutes a complex neuromuscular function that involves several brainstem and spinal cord circuits, several muscles such as the diaphragm, intercostal, laryngeal and pharyngeal muscles, as well as the lungs and the vasculature (Richter, 1982;Bianchi et al, 1995;Feldman, 1995) A reduction in such function can cause hypoxia, that evokes a response of the respiratory network that leads to the generation of gasping, which is considered to be the 'last-resort' respiratory effort to autoresuscitate and sustain life (Poets et al, 1999;Sridhar et al, 2003;Peña, 2009). Indeed, failure to respond to severe hypoxia via gasping and autoresuscitation can result in death.…”