Intensive Care Noise and Mean Arterial Blood Pressure in Extremely Low-Birth-Weight Neonates

ABSTRACT

Noise in neonatal intensive care units (NICUs) may impede growth and development for extremely low-birth-weight (ELBW, < 1000 g) newborns. We calculated correlations between NICU sound levels and ELBW neonates' heart rate and arterial blood pressure to evaluate whether this population experiences noise-induced stress. Sound levels inside the incubator, heart rate (HR), and arterial blood pressure recordings were simultaneously collected for eight ELBW neonates for 15 minutes during the first week of life. Cross-correlation functions were calculated for NICU noise, HR, and mean arterial blood pressure (MABP) recordings for each subject. ELBW neonates' HR and MABP were significantly correlated (r = 0.16 at 2-second lag time), with stronger correlation apparent for higher-birth-weight ELBW newborns (0.22 versus 0.10). Lower-birth-weight newborns responded to increased noise with HR acceleration from 45 to 130 seconds after noise events, and higher-birth-weight infants initially responded with an HR deceleration at 25 to 60 seconds, then HR acceleration ~175 seconds after noise increased. MABP was not as strongly correlated with NICU sound levels, although some correlation coefficients were slightly outside the 95% confidence interval. Higher-birth-weight newborns' more mature neurological systems may be responsible for stronger correlations between HR and MABP. NICU noise influenced newborns' HR, indicating that these infants hear and respond to NICU sounds. ELBW newborns in the first week of life seem to maintain a relatively stable blood pressure in response to moderate NICU sound levels (50 to 60 dBA).

KEYWORDS

Noise - neonatal intensive care - newborn - extremely low-birth-weight - blood pressure

REFERENCES

• 1 Hall R W, Anand K J. Physiology of pain and stress in the newborn.  NeoReviews. 2005;  6(2) e61-e68
• 2 Evans J B, Philbin M K. Facility and operations planning for quiet hospital nurseries.  J Perinatol. 2000;  20 S105-S112
• 3 Busch-Vishniac I J, West J E, Barnhill C, Hunter T, Orellana D, Chivukula R. Noise levels in Johns Hopkins Hospital.  J Acoust Soc Am. 2005;  118 3629-3645
• 4 American Academy of Pediatrics Committee on Environmental Health . Noise: a hazard for the fetus and newborn.  Pediatrics. 1997;  100 724-727
• 5 Morris B H, Philbin M K, Bose C. Physiological effects of sound on the newborn.  J Perinatol. 2000;  20 S55-S60
• 6 Vranekovic G, Hock E, Isaac P, Cordero L. Heart rate variability and cardiac response to an auditory stimulus.  Biol Neonate. 1974;  24 66-73
• 7 Wharrad H J, Davis A C. Behavioral and autonomic responses to sound in pre-term and full-term babies.  Br J Audiol. 1997;  31 315-329
• 8 Field T M, Dempsey J R, Hatch J, Ting G, Clifton R K. Cardiac and behavioural responses to repeated tactile and auditory stimulation by preterm and term neonates.  Dev Psychol. 1979;  15 406-416
• 9 Herd J A. Cardiovascular response to stress.  Physiol Rev. 1991;  71 305-330
• 10 Jurkovicova J, Aghova L. Evaluation of the effects of noise exposure on various body functions in low-birthweight newborns.  Act Nerv Super (Praha). 1989;  31 228-229
• 11 Williams A L, Van Drongelen W, Lasky R E. Noise in contemporary neonatal intensive care.  J Acoust Soc Am. 2007;  121 2681-2690
• 12 Diggle P J. Time Series: A Biostatistical Introduction. New York; Oxford University Press 1996
• 13 Mathews T J, MacDorman M F. Infant mortality statistics from the 2003 period linked birth/infant death data set. National Vital Statistics Reports. Hyattsville, MD; National Center for Health Statistics 2006 54(16)
• 14 Hack M, Klein N K, Taylor H G. Long-term developmental outcomes of low birthweight infants.  Future Child. 1995;  5 176-196
• 15 Wilson-Costello D, Friedman H, Minich N, Fanaroff A A, Hack M. Improved survival rates with increased neurodevelopmental disability for extremely low birth-weight infants in the 1990s.  Pediatrics. 2005;  115 997-1003
• 16 Tyson J E, Parikh N A, Langer J, Green C, Higgins R D. National Institute of Child Health and Human Development Neonatal Research Network . Intensive care for extreme prematurity: moving beyond gestational age.  N Engl J Med. 2008;  358 1672-1681
• 17 Lynch C D, Zhang J. The research implications of the selection of gestational age estimation method.  Paediatr Perinat Epidemiol. 2007;  21(suppl 2) 86-96
• 18 Gjessing H K, Skjoerven R, Wilcox A J. Errors in gestational age: evidence of bleeding early in pregnancy.  Am J Public Health. 1999;  89 213-218
• 19 Kramer M S, Platt R W, Wen S W Fetal/Infant Health Study Group of the Canadian Perinatal Surveillance System et al.. A new and improved population-based Canadian reference for birth weight for gestational age.  Pediatrics. 2001;  108 E35
• 20 Donovan E F, Tyson J E, Ehrenkranz R A National Institute of Child Health and Human Development Neonatal Research Network et al.. Inaccuracy of Ballard scores before 28 weeks' gestation.  J Pediatr. 1999;  135 147-152
• 21 Saltvedt S, Almstrom H, Kublickas M, Reilly M, Valentin L, Grunewald C. Ultrasound dating at 12–14 or 15–29 weeks of gestation? A prospective cross-validation of established dating formulae in a population of in-vitro fertilized pregnancies randomized to early or late dating scan.  Ultrasound Obstet Gynecol. 2004;  24 42-50
• 22 Morin I, Morin L, Zhang X et al.. Determinants and consequences of discrepancies in menstrual and ultrasonographic gestational age estimates.  BJOG. 2005;  112 145-152
• 23 Callaghan W M, Schieve L A, Dietz P M. Gestational age estimates from singleton births conceived using assisted reproductive technology.  Paediatr Perinat Epidemiol. 2007;  21 79-85
• 24 Engle W D. Blood pressure in the very low birth weight neonate.  Early Hum Dev. 2001;  62 97-130
• 25 Drouin E, Gournay V, Calamel J, Mouzard A, Roze J C. Assessment of spontaneous baroreflex sensitivity in neonates.  Arch Dis Child. 1997;  76 F108-F112
• 26 Mazursky J E, Birkett C L, Segar J L. Assessment of baroreflex control of heart rate variability in preterm infants.  Pediatr Res. 1995;  37 223A
• 27 Palmisano B W, Clifford P S, Coon R L, Seagard J L, Hoffmann R G, Kampine J P. Development of baroreflex control of heart rate in swine.  Pediatr Res. 1990;  27 148-152
• 28 Segar J L, Hajduczok G, Smith B A, Merrill D C, Robillard J E. Ontogeny of baroreflex control of renal sympathetic nerve activity and heart rate.  Am J Physiol. 1992;  263 H1819-H1826
• 29 Graham F K, Clifton R K. Heart rate change as a component of the orienting response.  Psychol Bull. 1966;  65 305-320