Background: Premature very low birthweight (VLBW) infants are born with an underdeveloped parasympathetic nervous system (PNS) which may limit their ability to respond adequately to feeding and may limit their capacit...Background: Premature very low birthweight (VLBW) infants are born with an underdeveloped parasympathetic nervous system (PNS) which may limit their ability to respond adequately to feeding and may limit their capacities for extrauterine growth and development. Objectives: To describe the patterns of autonomic response to feeding and identify relationships between change in heart period variability measures over time with selected infant characteristics. Methods: Individual growth curve analysis techniques were used to describe the patterns of change over time in sympathetic and parasympathetic tone as measured by low and high frequency heart period power. Results: Sixteen mechanically ventilated VLBW infants with a mean corrected gestational age of 30.4 weeks participated in the study. The low frequency (LF) power slope was - 17.67 (P=0.0002) and the high frequency (HF) power slope was - 0.92 (0.0003). There was a significant relationship between HF slope and birth gestational age (r=- 0.49, P=0.05). Conclusions: HF power, representing primarily parasympathetic activity, did not increase with enteral feeding as anticipated. LF power, an indicator of sympathetic tone, decreased during and after feeding suggesting the anticipated effect of inhibition of the sympathetic nervous system in response to the gut stimulus. Critically ill VLBW infants possess an overriding sympathetic response, but may not have adequate PNS tone development.展开更多
Objectives: To investigate the negative chronotropic response(NCR) to low-dose atropine in postoperative patients with congenital heart disease(CHD). Background: Low-dose atropine causes a NCR through the central nerv...Objectives: To investigate the negative chronotropic response(NCR) to low-dose atropine in postoperative patients with congenital heart disease(CHD). Background: Low-dose atropine causes a NCR through the central nervous system muscarinic receptor and is attenuated in adult heart failure patients. It has never been evaluated in CHD patients. Methods: NCR corrected for basal heart rate(HR)(minimal HR/-basal HR=cNCR) was determined after low-dose atropine(3 μg/kg) administration in 124 postoperative CHD patients(97 biventricular repair and 27 Fontan patients) and 11 controls and was compared with the cardiac autonomic nervous and functional status. Results: The cNCR in simple CHD(post atrial or ventricular septal defect closure), complex biventricular CHD, and Fontan patients were 0.92±0.04, 0.94±0.04 and 0.96±0.04, respectively, and higher than in controls(0.87±0.03, p< 0.001). In the complex CHD patients, higher cNCR was mainly associated with the lower pharmacologically determined cardiac parasympathetic nervous tone(PST), HR variability, high atrial natriuretic peptide, and lower right ventricular ejection fraction(p< 0.0001). In Fontan patients, the lower βsensitivity of the sinus node and the PST mainly determined the higher cNCR(p< 0.01) and the cNCR did not correlate with either hemodynamics or exercise capacity. Conclusions: NCR is attenuated in proportion to the impaired cardiac parasympathetic nervous system and hemodynamics in postoperative complex biventricular CHD patients. In addition to PST, βsensitivity of the sinus node significantly influences the NCR in Fontan patients.展开更多
文摘Background: Premature very low birthweight (VLBW) infants are born with an underdeveloped parasympathetic nervous system (PNS) which may limit their ability to respond adequately to feeding and may limit their capacities for extrauterine growth and development. Objectives: To describe the patterns of autonomic response to feeding and identify relationships between change in heart period variability measures over time with selected infant characteristics. Methods: Individual growth curve analysis techniques were used to describe the patterns of change over time in sympathetic and parasympathetic tone as measured by low and high frequency heart period power. Results: Sixteen mechanically ventilated VLBW infants with a mean corrected gestational age of 30.4 weeks participated in the study. The low frequency (LF) power slope was - 17.67 (P=0.0002) and the high frequency (HF) power slope was - 0.92 (0.0003). There was a significant relationship between HF slope and birth gestational age (r=- 0.49, P=0.05). Conclusions: HF power, representing primarily parasympathetic activity, did not increase with enteral feeding as anticipated. LF power, an indicator of sympathetic tone, decreased during and after feeding suggesting the anticipated effect of inhibition of the sympathetic nervous system in response to the gut stimulus. Critically ill VLBW infants possess an overriding sympathetic response, but may not have adequate PNS tone development.
文摘Objectives: To investigate the negative chronotropic response(NCR) to low-dose atropine in postoperative patients with congenital heart disease(CHD). Background: Low-dose atropine causes a NCR through the central nervous system muscarinic receptor and is attenuated in adult heart failure patients. It has never been evaluated in CHD patients. Methods: NCR corrected for basal heart rate(HR)(minimal HR/-basal HR=cNCR) was determined after low-dose atropine(3 μg/kg) administration in 124 postoperative CHD patients(97 biventricular repair and 27 Fontan patients) and 11 controls and was compared with the cardiac autonomic nervous and functional status. Results: The cNCR in simple CHD(post atrial or ventricular septal defect closure), complex biventricular CHD, and Fontan patients were 0.92±0.04, 0.94±0.04 and 0.96±0.04, respectively, and higher than in controls(0.87±0.03, p< 0.001). In the complex CHD patients, higher cNCR was mainly associated with the lower pharmacologically determined cardiac parasympathetic nervous tone(PST), HR variability, high atrial natriuretic peptide, and lower right ventricular ejection fraction(p< 0.0001). In Fontan patients, the lower βsensitivity of the sinus node and the PST mainly determined the higher cNCR(p< 0.01) and the cNCR did not correlate with either hemodynamics or exercise capacity. Conclusions: NCR is attenuated in proportion to the impaired cardiac parasympathetic nervous system and hemodynamics in postoperative complex biventricular CHD patients. In addition to PST, βsensitivity of the sinus node significantly influences the NCR in Fontan patients.
