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Static cerebrovascular pressure autoregulation remains intact during deep hypothermia
Author(s) -
Goswami Dheeraj,
McLeod Katherine,
Leonard Samantha,
Kibler Kathleen,
Easley Ronald Blaine,
Fraser Charles D.,
Andropoulos Dean,
Brady Ken
Publication year - 2017
Publication title -
pediatric anesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.704
H-Index - 82
eISSN - 1460-9592
pISSN - 1155-5645
DOI - 10.1111/pan.13205
Subject(s) - autoregulation , cerebral autoregulation , medicine , hypothermia , anesthesia , blood pressure , hemodynamics , perfusion , cerebral perfusion pressure , cerebral blood flow , cardiology
Summary Background Clinical studies measuring cerebral blood flow in infants during deep hypothermia have demonstrated diminished cerebrovascular pressure autoregulation. The coexistence of hypotension in these cohorts confounds the conclusion that deep hypothermia impairs cerebrovascular pressure autoregulation. Aim We sought to compare the lower limit of autoregulation and the static rate of autoregulation between normothermic and hypothermic piglets. Methods Twenty anesthetized neonatal piglets (5‐7 days old; 10 normothermic and 10 hypothermic to 20°C) had continuous measurements of cortical red cell flux using laser Doppler flowmetry, while hemorrhagic hypotension was induced without cardiopulmonary bypass. Lower limit of autoregulation was determined for each subject using piecewise regression and SR oR was determined above and below each lower limit of autoregulation as (%change cerebrovascular resistance/%change cerebral perfusion pressure). Results The estimated difference in lower limit of autoregulation was 1.4 mm Hg (lower in the hypothermic piglets; 95% C.I. −10 to 14 mm Hg; P =0.6). The median lower limit of autoregulation in the normothermic group was 39 mm Hg [ IQR 38‐51] vs 35 mm Hg [31‐50] in the hypothermic group. Intact steady‐state pressure autoregulation was defined as static rate of autoregulation >0.5 and was demonstrated in all normothermic subjects (static rate of autoregulation=0.72 [0.65‐0.87]) and in 9/10 of the hypothermic subjects (static rate of autoregulation=0.65 [0.52‐0.87]). This difference in static rate of autoregulation of 0.06 (95% C.I. −0.3 to 0.1) was not significant ( P =0.4). Conclusion Intact steady‐state cerebrovascular pressure autoregulation is demonstrated in a swine model of profound hypothermia. Lower limit of autoregulation and static rate of autoregulation were similar in hypothermic and normothermic subjects.