**Hemodynamic Monitoring in Neonates**

**Hemodynamic Monitoring in Neonates**

#### Petja Fister and Štefan Grosek Petja Fister and Štefan Grosek Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.69215

#### **Abstract**

Sick neonates are often hemodynamically unstable, hence their organs are inadequately supplied with oxygen. In order to maintain blood flow to vital organs, a number of compensatory mechanisms divert the blood flow away from the non‐vital organs. If hemodynamic changes are detected early, the cardiovascular compromise can be rec‐ ognized in compensated phase and thereby the escalation to decompensated phase of low cardiac output syndrome might be prevented. In the treatment of hemodynamically unstable neonate venous filling, contractility of the heart muscle, blood pressure in the aorta, systemic blood flow, and regional distribution of blood flow should be evalu‐ ated. There are many evaluation and measurement methods based on different physical basis, each of them having their advantages and disadvantages. For most of them, it has not been demonstrated that they improve outcomes of sick neonates. Using these methods, useful hemodynamic data for the treatment of sick neonates can be obtained. Using new techniques will clarify the pathophysiology of cardiovascular failure in sick neonates, assess the effects of drugs on blood pressure and perfusion of the heart and other organs.

DOI: 10.5772/intechopen.69215

**Keywords:** neonate, hemodynamics, oxygenation, perfusion, arterial blood pressure, cardiac output, peripheral vascular resistance

### **1. Introduction**

In neonatal intensive care unit (NICU), hemodynamic instability is an important cause for admis‐ sion and treatment after respiratory distress syndrome (RDS) and most common problems of prematurity [1]. Therefore, hemodynamic monitoring is important especially in transitional period to extrauterine life and during the next following days. Hemodynamic monitoring is also crucial in neonates with congenital heart defects (CHDs) and other complex surgical anom‐ alies of neonates. During early transitional period, cardiac output (CO) is not dependent solely

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© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

on the performance of the neonate's left ventricle but also on pulsating blood flow through the umbilical vein. This pulsating blood flow is extremely important especially if newborn is under fetal distress, and it is usually prudent to postpone ligation of umbilicus for a short period of time to add additional pulsatile and volume support to neonate's CO [2, 3]. Even later in the life, neonate with RDS requires hemodynamic monitoring due to disturbances related to RDS or other common problems of prematurity or immaturity. Besides prematurity, immaturity of cardiovascular system in the first days and weeks of life and altered physiology of systemic and pulmonary circulation in neonates with CHD may need frequent hemodynamic monitoring, whether invasively or noninvasively.

health‐care team of impending cardiovascular crisis, to obtain information specific to the dis‐ ease processes, which may facilitate diagnosis and treatment and allow one to monitor the response to therapy, and also to derive estimates of performances and physiological reserve that may in turn direct treatment [4]. The purpose of hemodynamic monitoring is to attain the optimal goals of cardiovascular therapy. Three functional‐based questions should be addressed: (1) Will blood flow to the body increase (or decrease) if the neonates' intravascu‐ lar volume is increased (or decreased), and if so, by how much? (2) Is the decrease in arterial blood pressure due to loss of vascular tone or merely due to inadequate blood flow? (3) Is the heart capable of maintaining an effective blood flow with an acceptable perfusion pressure

Physiologically, hemodynamic parameters can be divided into central or macro‐hemody‐ namic parameters, which assess blood flow and pressure in the heart, vena cava, pulmo‐ nary artery, and the aorta, and the peripheral or micro‐hemodynamic parameters, which assess the regional microvascular blood flow and tissue oxygenation (**Table 1**). The major‐ ity of existing hemodynamic monitoring assesses the central part of the cardio‐circulatory

In the past, hemodynamic monitoring data were attained in neonates with CHD after heart surgery when the invasive and frequently inaccurate pulmonary artery catheters have been inserted [5]. Recently, efforts have been made to monitor the newborns as noninvasively

> Estimating jugular venous pressure, hand pressure on the liver, elevation of the legs

pulses, heart rate\*, capillary refill time, peripheral‐core temperature difference

Palpating peripheral

Microcirculation Laser‐Doppler method,

**Table 1.** Physiologic hemodynamic parameters in neonates, assessed clinically, noninvasively, and invasively.

pulses

**Peripheral or micro** Regional blood flow Skin color, lactate Perfusion index\*, near‐

Cardiac output Palpating peripheral

**Clinical assessment Noninvasive** 

**measurement**

Inferior vena cava diameter and its collapsibility, lung ultrasonography

Echocardiography, cardiac magnetic resonance, electrical cardiometry\*, arterial pulse waveform analysis\*, electrocardiogram

Cuff oscillometry, Doppler ultrasound

infrared spectroscopy\*

video microscopy, xenon clearance techniques

**Invasive measurement**

Hemodynamic Monitoring in Neonates http://dx.doi.org/10.5772/intechopen.69215 29

Central venous catheters\*

Arterial catheters\*

Arterial catheters\*

without going into failure?

system.

**Hemodynamic parameter**

\*

**Physiologic parameter**

Afterload—arterial blood pressure

Continuous method, all others are intermittent.

**Central or macro** Preload—venous filling

## **2. Methods**

We conducted electronic searches of articles on hemodynamic management and care of neonates, using key terms: neonate, hemodynamics, oxygenation, perfusion, arterial blood pressure, cardiac output, and peripheral vascular resistance in the PubMed data base from the years 2000 to 2017 and reported the most relevant ones. The article lists the methods for the evaluation of the venous filling, cardiac output, blood pressure, regional blood flow, and microcirculation, from the clinical methods to the noninvasive and invasive ones. Some methods for monitoring the cardiovascular status of neonates are mainly used for research purposes. This chapter includes the impact of optimal arterial blood pressure, tissue perfu‐ sion, and persistent ductus arteriosus on the hemodynamic management in neonates. Also, the short‐ and long‐term outcomes in respect of hemodynamic management of neonates in the intensive care unit are addressed.

## **3. Physiology of hemodynamics**

Hemodynamics describes the dynamics of blood flow in the body. Blood flows in the cir‐ culatory system, which is composed of the central pump—the heart—and the blood ves‐ sels, and is controlled by homeostatic mechanisms. The pulsatile rate of blood flow out of the heart is called the cardiac output. The main role of the cardio‐circulatory system is to match the oxygen and nutrient needs of the organs and tissues and elimination of the metabolic wastes. The cardio‐circulatory system should provide an appropriate blood flow to the organs and by that an appropriate tissue perfusion. In the physiologic conditions, the tissue oxygen and nutrient needs are matched by their supply. In cardiovascular com‐ promise, the compensatory mechanisms allow the redistribution of blood flow to the vital organs—the brain, heart, and suprarenal gland in the neonate—at the expense of decreased blood flow to the non‐vital organs.

#### **3.1. Hemodynamic monitoring**

Hemodynamic monitoring encompasses the observation and measurement of hemody‐ namic parameters over time. The ultimate goals of hemodynamic monitoring is to alert the health‐care team of impending cardiovascular crisis, to obtain information specific to the dis‐ ease processes, which may facilitate diagnosis and treatment and allow one to monitor the response to therapy, and also to derive estimates of performances and physiological reserve that may in turn direct treatment [4]. The purpose of hemodynamic monitoring is to attain the optimal goals of cardiovascular therapy. Three functional‐based questions should be addressed: (1) Will blood flow to the body increase (or decrease) if the neonates' intravascu‐ lar volume is increased (or decreased), and if so, by how much? (2) Is the decrease in arterial blood pressure due to loss of vascular tone or merely due to inadequate blood flow? (3) Is the heart capable of maintaining an effective blood flow with an acceptable perfusion pressure without going into failure?

on the performance of the neonate's left ventricle but also on pulsating blood flow through the umbilical vein. This pulsating blood flow is extremely important especially if newborn is under fetal distress, and it is usually prudent to postpone ligation of umbilicus for a short period of time to add additional pulsatile and volume support to neonate's CO [2, 3]. Even later in the life, neonate with RDS requires hemodynamic monitoring due to disturbances related to RDS or other common problems of prematurity or immaturity. Besides prematurity, immaturity of cardiovascular system in the first days and weeks of life and altered physiology of systemic and pulmonary circulation in neonates with CHD may need frequent hemodynamic monitoring,

We conducted electronic searches of articles on hemodynamic management and care of neonates, using key terms: neonate, hemodynamics, oxygenation, perfusion, arterial blood pressure, cardiac output, and peripheral vascular resistance in the PubMed data base from the years 2000 to 2017 and reported the most relevant ones. The article lists the methods for the evaluation of the venous filling, cardiac output, blood pressure, regional blood flow, and microcirculation, from the clinical methods to the noninvasive and invasive ones. Some methods for monitoring the cardiovascular status of neonates are mainly used for research purposes. This chapter includes the impact of optimal arterial blood pressure, tissue perfu‐ sion, and persistent ductus arteriosus on the hemodynamic management in neonates. Also, the short‐ and long‐term outcomes in respect of hemodynamic management of neonates in

Hemodynamics describes the dynamics of blood flow in the body. Blood flows in the cir‐ culatory system, which is composed of the central pump—the heart—and the blood ves‐ sels, and is controlled by homeostatic mechanisms. The pulsatile rate of blood flow out of the heart is called the cardiac output. The main role of the cardio‐circulatory system is to match the oxygen and nutrient needs of the organs and tissues and elimination of the metabolic wastes. The cardio‐circulatory system should provide an appropriate blood flow to the organs and by that an appropriate tissue perfusion. In the physiologic conditions, the tissue oxygen and nutrient needs are matched by their supply. In cardiovascular com‐ promise, the compensatory mechanisms allow the redistribution of blood flow to the vital organs—the brain, heart, and suprarenal gland in the neonate—at the expense of decreased

Hemodynamic monitoring encompasses the observation and measurement of hemody‐ namic parameters over time. The ultimate goals of hemodynamic monitoring is to alert the

whether invasively or noninvasively.

the intensive care unit are addressed.

**3. Physiology of hemodynamics**

blood flow to the non‐vital organs.

**3.1. Hemodynamic monitoring**

**2. Methods**

28 Selected Topics in Neonatal Care

Physiologically, hemodynamic parameters can be divided into central or macro‐hemody‐ namic parameters, which assess blood flow and pressure in the heart, vena cava, pulmo‐ nary artery, and the aorta, and the peripheral or micro‐hemodynamic parameters, which assess the regional microvascular blood flow and tissue oxygenation (**Table 1**). The major‐ ity of existing hemodynamic monitoring assesses the central part of the cardio‐circulatory system.

In the past, hemodynamic monitoring data were attained in neonates with CHD after heart surgery when the invasive and frequently inaccurate pulmonary artery catheters have been inserted [5]. Recently, efforts have been made to monitor the newborns as noninvasively


**Table 1.** Physiologic hemodynamic parameters in neonates, assessed clinically, noninvasively, and invasively.

as possible and many new techniques have been applied in this vulnerable population to measure the central (arterial blood pressure and systemic blood flow) and peripheral hemodynamic parameters (peripheral vascular resistance). Arterial blood pressure is mea‐ sured either noninvasively by sphygmomanometer or invasively through arterial catheters. Systemic blood flow is noninvasively assessed by echocardiography, cardiac magnetic reso‐ nance, electrical cardiometry, and arterial pulse waveform analysis. Invasive methods for measuring the systemic blood flow are applied through centrally inserted vascular cath‐ eters. It is not known whether laser‐Doppler and spectroscopy in the near‐infrared spec‐ trum (near‐infrared spectroscopy, NIRS) can reliably monitor peripheral vascular resistance (**Figure 1**) [6].

**4. The central hemodynamic monitoring**

secretion, and the autonomic nervous system.

**4.1. The preload assessment**

**4.2. Cardiac output**

The central hemodynamic monitoring assesses the blood flow and the blood pressure in the heart and major vessels. The heart function and by that the stroke volume (SV) are determined by the preload—the venous filling, contractility of the heart muscle, and the afterload—which can be estimated only partially with the pressure in the aorta. The CO is the product of the SV and the heart rate (HR). Neonates increase their CO mainly by increasing the HR as they can‐ not sufficiently increase the SV. The HR is influenced by the body temperature, catecholamine

Hemodynamic Monitoring in Neonates http://dx.doi.org/10.5772/intechopen.69215 31

Clinically, the preload can be assessed visually assessing the jugular venous pressure, which is rarely possible in neonates with short neck. Using the hand pressure on the liver or eleva‐ tion of the legs increases preload and is a simple method of assessing preload but less used in the NICU. The venous filling in neonates can be measured by inferior vena cava (IVC) diameter, and its collapsibility during respiration indicates volume responsiveness [7, 8]. IVC assessment is not an accurate marker of volume status and fluid responsiveness in cases of (1) increased right atrial pressure, (2) tricuspid or pulmonary valve regurgitation, (3) pulmo‐ nary hypertension, or (4) right ventricular dysfunction. Another method for assessing volume status of a neonate is lung ultrasonography (US) [9, 10]. Sonographic visualization of B‐lines and measurement of extravascular lung water may aid diagnosing early volume overload in neonate. In a neonate with RDS after receiving surfactant, the B‐lines are still visible [11].

The measurement of CO is the most important parameter of the central hemodynamic moni‐ toring, assessing the perfusion of organs. It is vital for the etiopathogenic diagnosis of low cardiac output syndrome, being due to either hypovolemia, myocardial dysfunction, vasodila‐ tation, tamponade, pneumothorax, obstructive shock, pulmonary hypertension, or acute RDS. CO should be measured in the following clinical conditions: congenital and acquired heart diseases, shock, multiple organ failure, cardiopulmonary interactions during mechanical ven‐ tilation, clinical research, and assessment of new therapies [12]. The following three questions guide us in the interpretation of the adequacy of CO: (1) Is the delivery of oxygen adequate to meet the metabolic need of the patient? (2) Is oxygen delivery occurring with an adequate perfusion pressure? (3) Is the patient able to utilize the oxygen delivered, and if not, why so? [13]. Not only the measurement but also adequacy of CO and oxygen delivery is important, reflecting in clinical (capillary refill and core‐peripheral temperature difference) and labora‐ tory (lactic acid) parameters. But caveat is needed; normal values do not mean that regional perfusion is adequate, as well as abnormal values do not provide us with etiologic clue.

Clinically, CO with the systemic blood flow and perfusion can indirectly noninvasively be assessed by palpating the peripheral pulses and heart rate, capillary refill time, and measuring the peripheral‐core temperature difference [14]. None of clinical methods for the evaluation

**Figure 1.** Assessment of hemodynamic status in neonatal intensive care unit. Adapted from Ref. [64]. aEEG, amplitude‐ integrated electroencephalogram; BGA, blood gas analysis; ECG, electrocardiogram; NIRS, near‐infrared spectroscopy; PICCO, pulse‐induced contour cardiac output.
