Essential Neonatal Medicine (eBook)

Luke Jardine, Lawrence Miall, Sunil Sinha (Autoren)

eBook Download: EPUB

2017 | 6. Auflage
352 Seiten
Wiley (Verlag)
978-1-119-23575-0 (ISBN)

Infos

Providing a comprehensive yet concise guide for trainee doctors, neonatal nurses and midwives, Essential Neonatal Medicine continues to be an indispensable resource that combines the depth and breadth of a textbook with the efficiency of a revision guide.

Extensively updated and full-colour throughout, this edition includes new chapters on neonatal transport and palliative care, as well as further content on pathophysiology and embryology, quality improvement and risk management, infection control, and non-invasive ventilation.

With an improved artwork programme and a new glossary of terms, Essential Neonatal Medicine is ideal for all trainee health professionals new to neonatology, or looking for a comprehensive aid to support them.

Sunil Sinha
Professor of Paediatrics
University of Durham
Consultant Neonatologist
James Cook University Hospital
Middlesbrough, UK

Lawrence Miall
Consultant Neonatologist
Quality Lead, Leeds Children's Hospital
Leeds General Infirmary
Leeds Teaching Hospitals NHS Trust
Leeds, UK

Luke Jardine
Deputy Director Neonatology, Mater Mothers' Hospital
Senior Staff Specialist Neonatology, Mater Mothers' Hospital
Honorary Researcher, Mater Research
Associate Professor, The University of Queensland
Australia

Inhalt

Preface to the Sixth Edition vii

Acknowledgements vii

Preface to the First Edition viii

Abbreviations ix

How to use your textbook xi

About the companion website xii

1 The fetus, placenta and changes at birth 1

2 Perinatal epidemiology and audit 14

3 Multiple births 19

4 Neonatal consequences of maternal conditions 25

5 Resuscitation at birth 33

6 Examination of the newborn 46

7 Birth injury 65

8 Genetic disorders 73

9 Infant feeding and nutrition 82

10 Infection in the newborn 98

11 The extreme preterm infant 114

12 The low-birthweight infant 124

13 Respiratory physiology and respiratory support 131

14 Respiratory disorders 144

15 Apnoea, bradycardia and upper airway obstruction 160

16 Cardiovascular disorders 168

17 Gastrointestinal and abdominal disorders 186

18 Renal disorders 201

19 Jaundice 210

20 Haematological disorders 221

21 Endocrine and metabolic disorders 233

22 The central nervous system 250

23 Neurodevelopmental follow-up and assessment of hearing and vision 270

24 Developmental care and the neonatal environment 277

25 Organization of perinatal services 287

26 Neonatal transport 291

27 Discharge and follow-up of high-risk infants 297

28 Parent-infant attachment and support for parents of critically ill infants 306

29 Ethical issues and decision-making process in the treatment of critically ill newborn infants 311

30 End-of-life care and palliative care 316

Index 323

Textauszug

CHAPTER 1
The fetus, placenta and changes at birth

Key topics

• Placental function
• Fetal homeostasis
• Fetal circulation
• Assessment of fetal well-being
• Screening during pregnancy
• Fetal monitoring during labour
• Fetal compromise

Introduction

The discipline of ‘perinatal medicine’ spans the specialities of fetal medicine and neonatology. The obstetrician must have a thorough knowledge of pregnancy and its effects on the mother and fetus, as well as fetal development and physiology. The neonatologist specialises in the medical care of the infant immediately after birth, but must also have a thorough understanding of fetal development and physiology. This chapter reviews fetal assessment and physiology to provide the paediatrician and neonatal nurse with a better understanding of normal perinatal adaptation, and the adverse consequences arising from maladaptation.

Placental function

The placenta is a fetal organ that has three major functions: transport, immunity and metabolism.

The uterus is supplied with blood from the uterine arteries, which dilate throughout pregnancy, increasing blood supply 10-fold by term. Maternal blood bathes the intervillous space and is separated from fetal blood by the chorionic plate. Transport of nutrients and toxins occurs at this level. Oxygenated fetal blood in the capillaries of the chorionic plate leaves the placenta via the umbilical vein to the fetus (Fig. 1.1).

Figure 1.1 Diagram of placental structures showing blood perfusion.

Transport

The placenta transports nutrients from the mother to the fetus, and waste products in the other direction. This occurs in a number of ways, including simple diffusion (for small molecules) and active transport, which is used for larger molecules. The placenta is crucially also responsible for gaseous exchange of oxygen and carbon dioxide. Oxygen diffuses from the mother (PO2 = 10–14 kPa, 75–105 mmHg) to the fetus (PO2 = 2–4 kPa, 15–30 mmHg), where it binds to fetal haemoglobin. This has a higher affinity for oxygen than maternal haemoglobin for a given PO2. The dissociation of oxygen from maternal haemoglobin is also facilitated by a change in maternal blood pH.

Immunity

The placenta trophoblast prevents the maternal immune system from reacting against ‘foreign’ fetal antigens. Rejection does not occur because the trophoblastic cells appear to be non-antigenic, although it is known that fetal cells can cross into the maternal circulation where they can trigger an immune reaction (e.g. rhesus haemolytic disease). Maternal IgG antibody – the smallest of the immunoglobulins – can cross the placenta, where it provides the newborn with innate immunity to infectious diseases. These IgG antibodies can also cause perinatal disease such as transient hyperthyroidism (see Chapter 21).

CLINICAL TIP

Because IgG antibody crosses the placenta, the presence of IgG antibody in the newborn’s blood does not necessarily mean it has been congenitally infected. This is of particular relevance when testing newborns for HIV infection, where a positive IgG may just reflect maternal exposure. Instead, direct tests (e.g. viral RNA by PCR) are required (see Chapter 10).

Metabolism

The placenta is metabolically active and produces hormones, including human chorionic gonadotropin (hCG) and human chorionic thyrotropin (hCT). It also detoxifies drugs and metabolites. Oestriol cannot be produced by the placenta alone. This is done by the fetal liver and adrenal glands. The metabolites are then sulphated by the placenta to form oestrogens, one of which is oestriol.

Because of its metabolic activity, the placenta has very high energy demands and consumes over 50% of the total oxygen and glucose transported across it.

Fetal homeostasis

The placenta is an essential organ for maintaining fetal homeostasis, but the fetus is capable of performing a variety of physiological functions:

• The liver produces albumin, coagulation factors and red blood cells.
• The kidney excretes large volumes of dilute urine from 10–11 weeks’ gestation, which contributes to amniotic fluid.
• Fetal endocrine organs produce thyroid hormones, corticosteroids, mineralocorticoids, parathormone and insulin from 12 weeks’ gestation.
• Some immunoglobulins are produced by the fetus from the end of the first trimester.

Fetal circulation

The fetal circulation is quite different from the newborn or adult circulation. The umbilical arteries are branches of the internal iliac arteries. These carry deoxygenated blood from the fetus to the placenta, where it is oxygenated as it comes into close apposition with maternal blood in the intervillous spaces. Oxygenated fetal blood is carried in the single umbilical vein, which bypasses the liver via the ductus venosus to reach the inferior vena cava (IVC). It then passes into the IVC and enters the right atrium as a ‘jet’, which is shunted to the left atrium across the foramen ovale (Fig. 1.2). From here it passes into the left ventricle and is pumped to the coronary arteries and cerebral vessels. In this way the fetal brain receives the most oxygenated blood. Some relatively deoxygenated blood is pumped by the right ventricle into the pulmonary artery, but the majority bypasses the lungs via the ductus arteriosus (DA) to flow into the aorta, where it is carried back to the placenta. Only 7% of the combined ventricular output of blood passes into the lungs. The right ventricle is the dominant ventricle, ejecting 66% of the combined ventricular output.

Figure 1.2 Diagram of the fetal circulation through the heart and lungs, showing the direction of flow through the foramen ovale and ductus arteriosus.

In summary, there are three shunts:

1. The ductus venosus bypasses blood away from the liver to the IVC.
2. The foramen ovale shunts blood from the right atrium to the left atrium.
3. The ductus arteriosus shunts blood from the pulmonary artery to the aorta.

The last two shunts only occur because of the very high fetal pulmonary vascular resistance and the high pulmonary artery pressure that is characteristic of fetal circulation.

Umbilical vessels

There are two umbilical arteries and one umbilical vein, surrounded by protective ‘Wharton’s jelly’. In 1% of babies there is only one umbilical artery, and this may be associated with growth retardation and congenital malformations, especially of the renal tract. Chromosomal anomalies are also slightly more common.

CLINICAL TIP

It used to be common practice to arrange a renal ultrasound if there was only one umbilical artery – this is no longer required as antenatal imaging of the kidneys is sufficiently high quality.

Assessment of fetal well-being

Assessment of fetal well-being is an integral part of antenatal care. It includes diagnosis of fetal abnormality, assessment of the fetoplacental unit and fetal maturity, and the monitoring of growth and well-being in the third trimester and during labour (Fig. 1.3).

Figure 1.3 A timeline for fetal assessment and monitoring during pregnancy.

Assessment of maturity

Ultrasound

Early measurement of fetal size is the most reliable way to estimate gestation, and is considered to be even more reliable than calculation from the date of the last menstrual period (LMP). Ultrasound measurements that correlate well with gestational age include crown–rump length (CRL; until 14 weeks), biparietal diameter (BPD) or head circumference (HC) and femur length. The HC measurement at 14–18 weeks appears to be the best method for assessing the duration of pregnancy. In in-vitro fertilization (IVF) pregnancy the date of fertilization is used to calculate the gestation.

Assessment of fetal growth and well-being

Clinical assessment

Monitoring fundal height is a time-honoured method of 
assessing fetal growth. Unfortunately, up to 50% of small-
for-gestational age fetuses are not detected clinically.

Ultrasound

Serial estimates of BPD, HC, abdominal circumference and femur length are widely used to monitor growth, often on customized fetal growth charts. In fetuses suffering intrauterine growth restriction (IUGR), head growth is usually the last to slow down. Estimating fetal weight by ultrasound has become very accurate and provides critical information for perinatal decision-making about the timing of delivery.

Ultrasound imaging and Doppler blood flow

The location of the placenta can be confidently established using ultrasound. This is important to rule out placenta previa (a cause of antepartum haemorrhage) and to avoid cutting through the placenta at caesarean section. Doppler flow velocity waveforms of the umbilical artery are now used to assess fetal well-being. In near-term IUGR fetuses, abnormal Doppler waveforms are a reliable prognostic feature. As fetal blood flow becomes compromised there is reduced,...

Produkt-Details

• Erscheint lt. Verlag: 3.7.2017
• Reihe/Serie: Essentials
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Pädiatrie
• Schlagworte: Krankenpflege • Medical Science • Medizin • Neonatal Nursing • Neonatologie • Neonatology • nursing • Pädiatrie • Pediatrics • Säuglingspflege
• ISBN-10: 1-119-23575-8 / 1119235758
• ISBN-13: 978-1-119-23575-0 / 9781119235750