Cyclical variation of blood pressure and heart rate in neonates

Wireless, Skin-Interfaced Devices for Pediatric Critical Care: Application to Continuous, Noninvasive Blood Pressure Monitoring

Indwelling arterial lines, the clinical gold standard for continuous blood pressure (BP) monitoring in the pediatric intensive care unit (PICU), have significant drawbacks due to their invasive nature, ischemic risk, and impediment to natural body movement. A noninvasive, wireless, and accurate alternative would greatly improve the quality of patient care. Recently introduced classes of wireless, skin-interfaced devices offer capabilities in continuous, precise monitoring of physiologic waveforms and vital signs in pediatric and neonatal patients, but have not yet been employed for continuous tracking of systolic and diastolic BP-critical for guiding clinical decision-making in the PICU. The results presented here focus on materials and mechanics that optimize the system-level properties of these devices to enhance their reliable use in this context, achieving full compatibility with the range of body sizes, skin types, and sterilization schemes typically encountered in the PICU. Systematic analysis of the data from these devices on 23 pediatric patients, yields derived, noninvasive BP values that can be quantitatively validated against direct recordings from arterial lines. The results from this diverse cohort, including those under pharmacological protocols, suggest that wireless, skin-interfaced devices can, in certain circumstances of practical utility, accurately and continuously monitor BP in the PICU patient population.

Avoid Drug Incompatibilities: Clinical Context in Neonatal Intensive Care Unit (NICU)

The administration of several intravenous products on the same catheter is a very common situation in neonatology, where the stakes are high and the dangers sometimes unknown to clinicians. A large number of factors are involved in this administration, directly related to the installation of the infusion line. Moreover, the therapeutics used are often limited, and excluding classic “Marketing Authorization”. Some of these products may prove to be incompatible and thus lose their effectiveness, or even generate particles that are likely to be administered to the patient. We must be aware of these risks in order to optimize the prescription and administration of these intravenous products, especially as we treat fragile and immature patients. The aim of this work is to review the literature on the subject for the prescribers of neonatology units.

A literature review on flow-rate variability in neonatal IV therapy

AIM

To provide an overview of factors influencing the flow rate in intravenous (IV) therapy for newborns.

METHODS

We conducted a review of the literature from 1980 to 2011 in PubMed and Web of Knowledge. Articles focusing on flow-rate variability and possible complications due to flow-rate variability were included.

RESULTS

Forty-one articles were selected for this review. IV therapy in (preterm) neonates is prone to significant start-up delays and flow-rate variability. The sudden changes in the volume delivered to (preterm) neonates may have serious consequences. Low preprogrammed flow rates, total compliance, and volume of the IV administration set, the presence or absence of antisiphon valves or inline filters and the vertical displacement of syringe pumps all contribute to flow-rate variability in IV therapy for neonates.

CONCLUSIONS

Flow-rate variability in IV therapy and its clinical relevance are due to the preprogrammed flow rate, the hydrostatic pressure changes, the complete IV administration set compliance and the type of substances supplied to the patient. To improve IV therapy, the internal compliance of the complete IV administration set should be minimized and the highest possible preprogrammed flow rate should be used in combination with small syringes and low-resistance valves.

The role of systemic hemodynamic disturbances in prematurity-related brain injury

Premature infants who experience cerebrovascular injury frequently have acute and long-term neurologic complications. In this article, we explore the relationship between systemic hemodynamic insults and brain injury in this patient population and the mechanisms that might be at play.

Low frequency pressure waves of possible autonomic origin in severely head-injured children

BACKGROUND

Useful information (both clinical and pathophysiological) which may be extracted from intracranial pressure (ICP) recordings include: (1) the mean level of ICP (and CPP), (2) cerebrovascular autoregulation status, (3) the intracranial pulse pressure (the pulse wave index, ICPpp/ICPm) or the pressure-volume compensatory reserve index (RAP) and (4) the presence of any abnormal ICP waveform. This paper describes a slow frequency ICP waveform in children with TBI and postulates the pathophysiological basis and whether it contains clinically useful detail.

METHODS

Children admitted to the Regional Head Injury Service in Edinburgh with TBI have continuously monitored ICP, MAP, CPP, and other physiological data (stored at a 1-min resolution). Slow frequency waveforms were noted, prompting a review of the stored monitoring from all cases over a 10 year period.

FINDINGS

Episodic slow pressure waves were detected in 11 of 122 severely head-injured (HI) children. The waveforms were detected in children of all ages (1.6-15 years) in the ICP signal, which were in phase with similar fluctuations in the MAP, CPP, and HR signals. Their mean periodicity was 1 per 7 min (range 1 per 5-10 min), with a mean ICP pulse wave amplitude of 5.45 mmHg (range 4-7.5), and mean MAP pulse wave amplitude (pulse pressure) of 10.4 mmHg (range 4-15 mmHg). The duration was variable (range approx 2 h to 4.5 days). They were detected in the preterminal phase after serious HI, as well as in those children who made an independent recovery (GOS 4/5). The waves were not related to the mean levels of ICP, CPP, MAP, temperature or the state of cerebrovascular autoregulation.

CONCLUSIONS

We postulate that these previously unreported slow waveforms may reflect the very low frequency (VLF) and ultra low frequency (ULF; < or = 1 per 5 min) components of heart rate and arterial blood pressure variability.

Flow rate, syringe size and architecture are critical to start-up performance of syringe pumps

BACKGROUND AND OBJECTIVES

Levobupivacaine in combination with sufentanil may be used for labour or postoperative regional analgesia. The risk of bacterial growth within these contained solutions for several hours at room temperature is unknown. We investigated the in vitro antimicrobial effect of levobupivacaine and sufentanil against common micro-organisms encountered during regional anaesthesia.

METHODS

Standardized suspensions of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli were incubated for 1, 3, 6 and 24 h at 25 degrees C, with saline (as control), sufentanil 0.5 or 0.75 microg mL-1, levobupivacaine hydrochloride 5.6 mg mL-1 and concentrations of 1.4, 2.8 and 5 mg mL-1 of levobupivacaine hydrochloride with sufentanil 0.5 microg mL-1. Colony counts were compared after 24 h incubation at 37 degrees C.

RESULTS

No bacterial growth was observed on any bacterial strain for any solution tested throughout the experiment.

CONCLUSIONS

Our results suggest that solutions of levobupivacaine combined with sufentanil may be used for 24 h at room temperature during regional anaesthesia with no risk of bacterial growth.

Blood pressure in the very low birth weight neonate

Few aspects of management of very low birth weight (VLBW; <1500 g) neonates have generated as much controversy as the assessment of blood pressure (BP) and need for treatment of perceived abnormalities of this physiologic variable. The approach to this problem may differ greatly among various institutions and even among clinicians within a given center. The purpose of this manuscript is to review available information regarding physiologic determinants and measurement of BP in VLBW neonates, normative data for BP, clinical factors that may affect BP in these at-risk neonates and studies in which presumed abnormalities of BP resulted in adverse clinical outcomes. Options for treatment of low BP in VLBW neonates also will be discussed.

Cyclical fluctuations in blood pressure, heart rate and cerebral blood volume in preterm infants

Many recently published papers describe cyclical changes of cerebral circulatory variables, mainly in cerebral blood flow velocity (CBFV) performed with Doppler sonography. In this paper we focus on another important variable of cerebral circulation: on cerebral blood volume (CBV) measured by near infrared spectrophotometry (NIRS). In a retrospective analysis of NIRS measurements in 20 preterm infants (median 27 3/7 weeks of gestation), the dominating frequencies and prevalence of cyclical changes of CBV and its possible correlation with peripheral circulatory variables (mean arterial pressure and heart rate) was examined. In 19 out of the 20 infants cyclical changes of CBV were found within a frequency range of 2-4.7 cycles/min which is comparable to the results of the Doppler studies describing fluctuations in CBFV. A dominating frequency of heart rate (HR), was found only in 12 out of 20 infants, and it was with 2.1-3.8 cycles/min in a similar range compared to CBV. In mean arterial blood pressure (MABP), however we detected cycles with longer periods every 1-2.5 min in 14 out of 20 infants. There was a significant coherence between MABP/CBV and HR/CBV. The area under the coherence curve, however, was significantly larger between MABP and CBV as compared to HR and CBV (P = 0.0007, Wilcoxon signed-rank test).

Intra-arterial blood pressure reference ranges, death and morbidity in very low birthweight infants during the first seven days of life

OBJECTIVES

We aimed to: (1) assess the association of average, low, high and variable mean blood pressure (mbp) on death and the common morbidities of very low birthweight infants, and in doing so, (2) to derive representative reference ranges for mbp in very low birthweight infants.

STUDY DESIGN

This five year retrospective study assessed 1 min computer recordings of intra-arterial mbp in 232 very low birthweight infants over the first 7 days of life in a tertiary NICU. Four measures of mbp were assessed: average, variability, maximum (per time period), and percentage of time with a mean blood pressure less than the infant's gestation. Correlation was made with death and the development of intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL) and retinopathy of prematurity (ROP).

RESULTS

The mbp increased with increasing birthweight and postnatal age (though with a slight decrease on days 6 and 7). Birthweight, gestation and colloid support (adjusted for birthweight and gestation) were the only factors significantly associated with mbp. IVH was predominantly associated with a low and variable mbp on the day IVH was noted or the day before. PVL and ROP were not associated with blood pressure.

CONCLUSIONS

These reference ranges include more infants and data than previously published and relate mbp in this cohort to morbidity and mortality. They could assist clinicians in judging appropriate mbp for birthweight.

A randomized, controlled trial of computerized physiologic trend monitoring in an intensive care unit

OBJECTIVE

To assess whether the provision of computerized physiologic trend data could improve outcome in newborn infants requiring intensive care.

DESIGN

Randomized, controlled trial, with subsidiary questionnaire studies.

SETTING

Tertiary neonatal intensive care unit with 12 intensive care cots.

PATIENTS

All infants admitted between January 1991 and September 1993 who were < or =32 wks gestation or >32 wks gestation, and ventilated for >4 hrs or asphyxiated.

INTERVENTIONS

Randomization to one of four groups for first 7 days of life: A) no display of trend data; B) continuous display of trend data; C1) alternating 24-hr display of trend data, starting with display in first 24 hrs; and C2) alternating 24-hr display of trend data, starting with no display in first 24 hrs.

MEASUREMENTS AND MAIN RESULTS

The short-term effects of monitoring on patient outcome was judged by volume of colloid given, number of blood gases taken, and by measurement taken from cranial Doppler ultrasound. Medium-term measures included time ventilated, time given supplemental oxygen, death, time to death or discharge, and cranial ultrasound at discharge. Long-term outcome was assessed by neurodevelopmental status at age 1 to 4 yrs of age. Staff and parent questionnaires assessed their respective attitudes to the introduction of this technology. None of the patient outcome measures, short-, medium-, or long-term, demonstrated any significant benefit from the provision of computerized physiologic trend monitoring. Staff questionnaires demonstrated an acceptance of the system and an improved understanding of neonatal physiology as a result of computerized physiologic trends. Parent questionnaires demonstrated increased anxiety caused by the system in 11% of parents, although only 1% of parents continued to have concerns if the system were able to help their child.

CONCLUSIONS

A randomized, controlled trial was unable to demonstrate any benefit to patients resulting from the introduction of a computerized physiologic trend monitoring system. Benefits of the system have been recognized, however, in subsidiary studies, staff education, and research studies.

Sleep state changes associated with cerebral blood volume changes in healthy term newborn infants

In order to assess the possible effects of sleep states on cerebral haemodynamics in healthy term infants, we measured cerebral oxyhaemoglobin, deoxyhaemoglobin and total haemoglobin concentration using near infrared spectroscopy. Thirty-seven sleep state changes in seventeen infants (gestational age: 37 to 41 4/7 weeks), aged between two and eight days were continuously registrated during 1-3 h. Transcutaneous PaO2, PaCO2, arterial O2 saturation and heart rate were simultaneously recorded and sleep states were clinically defined. There was a close relationship between sleep state changes and changes in total cerebral haemoglobin concentration, which increased from active to quiet sleep and decreased from quiet to active sleep. Changes in total cerebral haemoglobin were due, in the most part, to changes in the cerebral oxyhaemoglobin concentration. In conclusion, sleep states influence the cerebral haemoglobin concentration. Studies on cerebral haemodynamics should take sleep state into account in term newborn infants.

Hemodynamic effects of intravenous morphine infusion in ventilated preterm babies

BACKGROUND

the importance of sedation and analgesia of newborn babies in intensive care is only now receiving recognition in many neonatal units.

OBJECTIVE

to evaluate the hemodynamic effects of morphine on Cerebral Blood Flow velocities (CBFv), Cardiac Output (CO), Stroke Volume (SV), Mean Arterial Blood Pressure (MABP) and Heart Rate (HR) in ventilated preterm infants, before and during the infusion of a loading dose.

DESIGN

prospective, open, non-randomized, before-after intervention study with hemodynamic measurements made by Doppler ultrasound.

SETTING

neonatal Intensive Care Unit, Tertiary Care Center.

PATIENTS

sequential sample of 30 ventilated preterm newborns (gestational age (GA) 29 +/- 2 wks, range 27-31, birth weight (BW) 1240 +/- 440 g, range 800-1680).

INTERVENTION

each subject received an intravenous loading dose of morphine (100 mcg/Kg/h) for 2 h, followed by a continuous infusion of 25 mcg/kg/h.

MEASUREMENTS

the following Doppler parameters of the anterior cerebral artery were estimated: Peak systolic flow velocity (Vs), end-diastolic flow velocity (Vd), mean flow velocity (Vm) and Pourcelot' Resistance Index (RI). Measurements of CBFv, CO and SV (by Doppler ultrasound), MABP and HR were made 30 min before (baseline values) and at 15 (M15), 30 (M30), 60 (M60) and 120 min (M120), during the morphine loading infusion. Statistical evaluation analysis of variance, significance was calculated by Student-Newman-Kenfeld test.

RESULTS

there were no statistically significant changes in the cerebral and cardiac Doppler parameters before or during the 120 min of morphine loading infusion. There was a non-significant fall in MABP (MABP: Baseline value = 44 +/- 6 mmHg, M120 = 42 +/- 4 mmHg; reduction = 4%) and HR (HR = Baseline value = 148 +/- 12 beats/min., M120 = 140 +/- 16 beats/min.; reduction = 5%).

CONCLUSIONS

a loading dose of morphine over 2 h did not have any significant effect on MABP or cerebral and cardiac hemodynamics. No adverse effects were noted that could be attributed to morphine therapy.

Is post-hypoxic-ischemic cell damage associated with excessive ATP consumption rather than a failure of ATP production?

Secondary cell damage after ATP depletion due to hypoxia or ischemia is clinically important because it correlates with residual effects; post-hypoxic-ischemic fits can be associated with later cerebral palsy. The mechanisms involved in delayed secondary cell damage are not clear, possibly because extensive relevant evidence is often fragmented. However, a sequence of changes can be suggested; this cross-linked sequence is tentatively outlined in this review. The outline suggests explanations for otherwise ill-understood clinical disturbances such as the loss of inhibitory control in damaged cells and the well documented reduction of cellular ATP. Loss of control may be due to reduced synthesis of control proteins and the reduced ATP concentration may be due to increased energy consumption.

Blood pressure, heart rate, and skin temperature in preterm infants: associations with periventricular haemorrhage

The mean arterial blood pressure (MABP), heart rate, and skin temperature were monitored every 15 minutes in the first 10 days after birth in 34 preterm infants, gestational age 24 to 33 weeks. Ultrasound brain scans carried out daily showed that a periventricular haemorrhage (PVH) occurred in a subgroup of infants (n = 15) of lower birthweight and gestational age. In infants without PVH the daily median of MABP increased with birthweight and postnatal age; that of heart rate was not affected by postnatal age, body weight, or gestational age; and that of skin temperature showed a slight fall with postnatal age. In infants with PVH, on or before the day of PVH, daily medians of MABP and skin temperature were not significantly different from those of infants without PVH, but the daily median of heart rate tended to be slightly higher. The percentage of positive correlations between the 96 15 minute values per day for heart rate and MABP increased with postnatal age and with birthweight, but did not differ in infants who developed a PVH. The coefficient of variation (CV) of the 96 15 minute values for MABP tended to be higher in infants on the day of PVH, and a similar trend was apparent on the day before. The processes of development of blood pressure, heart rate, and skin temperature are similar in infants with or without PVH but at lower gestational ages altered blood pressure control may cause brain haemorrhage.

Elevated arterial blood pressure is associated with peri-intraventricular haemorrhage

In a prospective study, brain ultrasound scans were performed in 42 newborns (median birth weight 1700 g, range 1020-3720 g; gestational age 32 weeks, 26-36) to reveal peri-intraventricular haemorrhage (PIVH) (grades I-IV) as well as echodensities (ED) and/or periventricular leucomalacia (PVL). ECG and arterial blood pressure were recorded on magnetic tape at 8-h intervals during the first 24 h of life for further computer analysis. Heart rate (HR) and its variability (HRV) indices RMSM (long-term variability) and RMSSD (short-term variability), together with their coefficients of variation, were computed. Systolic (SBP), diastolic (DBP), and mean blood pressures (MBP) were detected as average values for 2-min stationary segments together with the respective minima and maxima. The indices of variability and their coefficients of variation were computed for the arterial pressure. PIVH was found in 12 newborns and ED in 8 (of whom two developed PVL). The remaining 22 served as controls. Neither HR, HRV nor BP variability differed between the groups. DBP was higher in the group with PIVH (39 mmHg) when compared to both the controls (33 mmHg, P < 0.05) and the ED group (32 mmHg, P < 0.01). MBP behaved respectively (45 mmHg, 38 mmHg, 37 mmHg, P < 0.01). SBP behaved also similarly when gestational age and birth weight were used as covariates (57 mmHg, 48 mmHg, 47 mmHg, P < 0.01).

CONCLUSION

Our results suggest that elevated diastolic, mean and systolic blood pressure are significantly associated with peri-intraventricular haemorrhage in preterm newborn infants.