Endotoxin effects on markers of autonomic nervous system function in the piglet: implications for SIDS.
The hypothesis was tested in 30 newborn piglets that the effects of a low dose of endotoxin (1 microg i.v. bolus; Salmonella abortus equi) would impair autonomic nervous system function. Two tests of autonomic function were performed following external warming (pre-endotoxin) and during endotoxin-generated thermogenesis: (1) analysis of heart rate variability in the time and frequency domains and (2) baroreflex sensitivity measured following intravenous injection of the vasoactive drugs nitroprusside and phenylephrine. Beat-to-beat heart rate variability (SDDeltaRR) fell by 2.2 ms from 7.0 ms before fever (p < 0.05). Low-frequency spectral power fell by 2.4 ms(2) from 4.1 ms(2) before fever (p < 0.05). The sensitivity of the baroreflex to changes in blood pressure induced by the vasoactive drugs decreased during fever by 0.72 ms/mm Hg for the nitroprusside test (p < 0.0005) and by 0.31 ms/mm Hg for the phenylephrine test (p < 0.005). These results indicate that in the piglet the balance of autonomic tone is altered and autonomic responsiveness reduced during the thermogenic phase of a fever. These findings are consistent with known risk factors for sudden infant death syndrome.
Voss
L J
LJ
Department of Physiology, University of Otago Medical School, Dunedin, New Zealand. VossL@waikatodhb.govt.nz
Bolton
D P G
DP
Galland
B C
BC
Taylor
B J
BJ
D000818:Animals; D000831:Animals, Newborn; D001341:Autonomic Nervous System / Q000187:drug effects* / Q000503:physiopathology; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001833:Body Temperature Regulation; D004731:Endotoxins / Q000008:administration & dosage*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D012475:Salmonella; D013398:Sudden Infant Death / Q000453:epidemiology / Q000209:etiology*; D013552:Swine
D004731:Endotoxins; D009599:Nitroprusside; D010656:Phenylephrine