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PART II

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Neonatal Emergencies

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CHAPTER4

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Respiratory Distressinthe Newborn

CASE 1

Antenatal ultrasonography has revealed a large solid lesion occupying most of the right chest. At birth respiratory distress develops rapidly: a chest x-ray shows a partly cystic and solid lesion in the right lower zone.

Q 1.1 What is the differential diagnosis?

What treatment is needed?

Q 1.2

When a newborn baby breathes more rapidly than normal, respiratory distress is present. The degree of distress may be slight initially, but progressive deterioration may culminate in irreversible respiratory failure.

Neonatal respiratory distress is not normally the province of the paediatric surgeon, but it may occur in a specific group of neonatal patients in whom the causes are amenable to surgical correction. Respiratory failure may have developed already when the baby presents, and prompt action may save the neonate’s life and regain the opportunity for corrective surgery. Those caring for newborns must be able to recognise respiratory distress and the paediatric surgeon must be familiar with its causes and the principles of management.

In only a few cases may a conclusive diagnosis be made clinically, and x-rays of the thorax and abdomen should be obtained as soon as possible.

Recognition of respiratory distress

The key clinical feature is a raised respiratory rate. Tachypnoea is present in the neonate if the respiratory rate exceeds 60 breaths per minute. In addition, tachycardia is almost invariably present, and if the pulse rate

CASE 2

After a breech delivery, acute cyanosis and respiratory distress develop in a term neonate. Breath sounds are diminished over the left chest.

Q 2.1 What is the likely problem?

What emergency treatment may be needed?

Q 2.2

exceeds 200 beats per minute, the situation is serious. Bradycardia is also a dangerous sign and often portends imminent respiratory failure.

Other cardiovascular signs, such as apparent ‘dextrocardia’, and the nature of the peripheral pulses, will provide further clues as to the underlying cause. The abdomen may be scaphoid in babies with a congenital diaphragmatic hernia, but may be distended when there is a pulmonary cause for the respiratory distress. Intestinal obstruction and neonatal peritonitis may cause abdominal distension, thus leading to respiratory embarrassment. Respiration may be laboured or associated with chest wall deformity, or there may be inspiratory (sternal) retraction, indicative of obstruction of the airways.

A surgical cause is present in a minority of babies with respiratory distress, and the surgeon must be familiar with the differential diagnosis, for example, hyaline membrane disease, meconium aspiration and cerebral birth injuries [Table4.1]. Antenatal ultrasonography, obstetrical details and any abnormal physical signs will help determine the cause of tachypnoea. A baby who is pale and cyanosed but improves with oxygen may have a congenital diaphragmatic hernia (Chapter5). Ascaphoid abdomen and barrel chest, with the heart sounds best heard on the right, are supportive

Jones’ Clinical Paediatric Surgery, Seventh Edition. Edited by John M. Hutson, Michael O’Brien, Spencer W. Beasley, Warwick J. Teague and Sebastian K. King. © 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.

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Table 4.1 Causes of neonatal respiratory distress

Type of obstruction Examples

Upper respiratory tract

obstruction Nasal Pharyngeal Laryngeal Tracheal

Lower respiratory tract

obstruction

Alveolar disease Hyaline membrane disease

Pulmonary compression Pneumothorax

Neurological disease Birth asphyxia

Choanal atresia Pierre-Robin syndrome Hamartoma of tongue ‘Infantile larynx’ Vocal cord palsy Subglottic vascular anomaly Laryngeal web or cyst Tracheomalacia Massive lymphangioma (cystic

hygroma) Vascular ring Meconium aspiration Aspiration of gastric contents Lobar emphysema (congenital)

Pneumonia Congenital heart disease Pulmonary oedema Congenital diaphragmatic hernia

Congenital diaphragmatic hernia Repairedexomphalos or gastroschisis Congenital lobar emphysema Congenital lung cysts Bronchogenic cysts Duplication cysts Abdominal distension

Apnoea of prematurity Intracranial haemorrhage Convulsions

physical signs of a left congenital diaphragmatic hernia, and a chest x-ray will confirm the diagnosis. By contrast, a baby with cyanosis and respiratory distress which is relieved by crying may have choanal atresia (Chapter14).

The principles of management

When respiratory failure is present already, urgent treatment is required, regardless of the underlying cause. Accurate diagnosis is based upon the clinical history and signs, and subsequent imaging. The degree of respiratory or metabolic acidosis must be determined to guide the resuscitation required. Where applicable, an

operation is undertaken to correct the cause, usually after correction of the physiological disturbances.

Specific conditions

An important aspect of neonatal respiratory distress is that many of the causes have a wide clinical spectrum, for example, a congenital diaphragmatic hernia may produce a direct threat to life within minutes of birth, yet on other occasions may cause no symptoms until well beyond the neonatal period (Chapter 5). Congenital pulmonary airway malformations and pulmonary sequestration are typically diagnosed on antenatal ultrasound, but only infrequently cause respiratory embarrassment in the neonatal period. Choanal atresia is discussed in Chapter14 and oesophageal atresia in Chapter6.

Malformations that involve one lung and cause neonatal respiratory distress include congenital lobar emphysema and congenital cystic disease of the lung. The physical signs are not diagnostic and imaging is required to make the diagnosis. There are considerable variations in the clinical picture, and when there is persisting respiratory distress, an operation may be indicated. Resection of the affected lung segment not only removes functionless pulmonary tissue with little or no gaseous exchange but also allows expansion of the normal pulmonary segments that have been compressed by the over-distended segment, lobe or lobes.

Congenital lobar emphysema

The aetiologies of congenital lobar emphysema are variable and include congenital deficiency of the bronchial cartilage and extrinsic compression from an intrathoracic cyst. The end result is expiratory obstruction and air trapping in the affected lobe, leading to massive distension of a pulmonary lobe.

The cardinal symptom is tachypnoea that is most noticeable when the baby feeds. Not infrequently there is a dry cough and stridor. Cyanosis may be an indication for urgent treatment. The mediastinum is displaced and the chest wall over the affected area is prominent and has relatively reduced respiratory excursion; breath sounds are diminished and the percussion note typically is hyper-resonant.

X-rays show an area of increased radiolucency in which there are some bronchovascular markings. There may be downward displacement of the dia phragm on

Chapter4: Respiratory Distressinthe Newborn 21

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Figure 4.1 Congenital lobar emphysema of the right upper

lobe that is overdistended and herniating across the midline.

the affected side, and the over- distended lung may herniate across the midline [Fig. 4.1]. The lobes most commonly affected are theleft upper lobe or the right middle lobe. An increasing number of patients are now managed non-operatively, but when required, operative management is lobectomy.

Congenital cystic lung

The clinical features are similar to those of congenital lobar emphysema, in that respiratory distress often occurs early, but usually it is more urgent and severe.

X-rays show a large cyst with a sharply defined border [Fig. 4.2] or an extensive multicystic area. There is typically compression and collapse of unaffected areas of the lungs and displacement of the mediastinum.

The operative aim is to remove the portion of the lung that is functionless and interfering with the function of the surrounding normal lung. Depending on the

Figure 4.2 Congenital cystic lung. A giant cyst has replaced the

right lower lobe, compressing the remaining right lung and herniating across the midline to displace the heart and compress the left lung.

distribution of disease, resection of the affected lobe or even pneumonectomy may be required.

Pulmonary sequestration

Pulmonary sequestration is an uncommon malformation in which there is non-functioning lung tissue which has no connection with the normal bronchial tree, and a blood supply which arises from an anomalous systemic artery, often directly from the aorta [Fig.4.3] (Chapter49). It usually occurs on the left side and may be either intralobar or extralobar, depending on whether it shares visceral pleura with the normal lung. It may be diagnosed on antenatal ultrasonography, may present as a pulmonary infection, because of its space-occupying effect, or be found incidentally on chest x-ray. The sequestration is resected by thoracoscopy or by open thoracotomy.

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Figure 4.3 Anomalous blood supply from the aorta to a left

pulmonary sequestration.

Congenital pulmonary airway malformation

Congenital pulmonary airway malformations (CPAMs) include a range of localised abnormalities in which the bronchiolar tissue is abnormal, with communicating cysts and a relative paucity of cartilage. Previously, these lesions were termed ‘congenital cystic adenomatoid malformation’ .They may be diagnosed on antenatal ultrasonography as a cystic or solid mass in one part of the lung. Maternal polyhydramnios and mediastinal shift may occur. Many CPAMS observed on antenatal ultrasonography regress and have resolved by term.

The majority of patients born with a CPAM are asymptomatic. However, those CPAMs that present postnatally may do so in three ways:

1 Respiratory distress (60%), 2 Infectious complications, e.g. recurrent pneumonia

(20%) and

3 Incidental finding on chest x-ray (20%).

Symptomatic or complicated CPAMs are definitively managed by surgical resection. The management of antenatally diagnosed CPAMs which remain asymp-

Figure 4.4 Severe pulmonary interstitial emphysema.

tomatic is more controversial, but non-operative management with follow-up is a valid alternative to elective resection in some of these cases.

Mediastinal conditions

Very rarely, large cystic teratomas and duplication cysts cause respiratory distress and should be removed. In the neonate, oesophageal duplication cysts may present with increasing respiratory distress because of their spaceoccupying effect compressing the normal airways.

Pulmonary interstitial emphysema

This is an acquired condition of extreme prematurity seen in infants where assisted ventilation is required for severe hyaline membrane disease. High ventilatory pressures force air into the lung interstitium, which tracks along peribronchial spaces, producing interstitial cysts which have a characteristic appearance on x-ray [Fig. 4.4]. Treatment is directed at reducing the ventilatory pressures. In severe and progressive cases, thoracotomy may be required to deflate the cysts. Refinements in neonatology have resulted in a significant decrease inthe incidence of this condition, such that it is now seen rarely.

Neonatal Pneumothorax

Pneumothorax may occur as a complication of diffuse pulmonary disease such as meconium aspiration, or of a localised abnormality, for example, subpleural

Chapter4: Respiratory Distressinthe Newborn 23

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emphysematous bleb. The pneumothorax may be suspected on clinical grounds by sudden

deterioration in condition, displacement of the trachea or apex beat, or a hyper-resonant percussion note, but x-rays are typically required to confirm the diagnosis.

In neonates, the severity of the symptoms frequently is out of proportion to the size of the pneumothorax. Even a small pneumothorax may be associated with severe respiratory distress when there is pre-existing parenchyal lung disease and little respiratory reserve. Intercostal drainage is urgent.

Haemothorax

Haemothorax is an infrequent complication of haemorrhagic disease of the newborn and may produce an alarming clinical picture. This is due to mechanical factors which interfere with respiration and to the reduction of the circulating blood volume. Intercostal drainage and blood transfusion are required.

Acute respiratory failure in the neonate

Acute respiratory failure occurs when oxygenation and/ or ventilation are impaired sufficiently to be an immediate threat to life. It is usually the result of asphyxia due to:

1 Birth asphyxia 2 Other injuries sustained during birth 3 Developmental anomalies, including congenital heart

disease

4 Hyaline membrane disease in the premature neonate 5 Increased susceptibility to infection

The factors in neonates which predispose to respiratory failure are summarised in Table 4.2. With limited respiratory reserve, respiratory failure may occur rapidly.

Signs of respiratory failure

In the neonate, especially if premature, acute hypoxia causes pallor, apnoea, bradycardia, hypotension and lethargy. The clinical signs of hypercapnia – sweating, tachycardia and hypertension – are seen rarely, but pulmonary haemorrhage, cerebral haemorrhage, severe hyperkalaemia and hypoglycaemia all may occur as the result of hypoxia.

Table 4.2 Factors predisposing neonates to respiratory failure

Factors Comments

Metabolic rate Metabolism per kilogram is twice that of

adults

Respiratory rate Lung surface area per kilogram is similar

to adult; so neonate has much less respiratory reserve

Compliance Neonate’s chest wall is less able to adjust

to reduced lung compliance or increased airway resistance

Airway calibre Relatively larger total airway resistance

than in older children or adults

Airway obstruction Narrow airways are more prone to

obstruction by oedema and secretions

Temperature

control

Relatively poor temperature regulation,

especially in the premature. In a cold environment, oxygen consumption may increase two- or threefold

General management

A neonate with incipient respiratory failure requires close observation at all times. Neonates should be nursed in an isolette or under a radiant heater so that the temperature is controlled and observation unimpeded. Handling should be kept to a minimum, as it may increase oxygen consumption dramatically. Monitoring of heart rate and oxygen saturation is mandatory. Transcutaneous pO

and pCO2 monitoring

and BP monitoring are also preferable.

Oxygen

The method of delivery of oxygen depends upon the neonate’s age, oxygen concentration required and the underlying condition. All patients having prolonged oxygen therapy must have continuous oximetry and serial arterial blood gas estimations with adjustment of inspired oxygen concentration to ensure adequate arterial saturation. Premature neonates receiving supplementary oxygen therapy are at risk of retinopathy of prematurity, for which frequent blood gas measurements are required to maintain the arterial pO

in the range of 6.6–10.6 kPa (50–80 mmHg).

In the newborn, gentle suction is performed at intervals to remove pooled secretions and to stimulate coughing. However, pharyngeal and endotracheal suction may cause a sudden fall in arterial pO

that necessitates an increase in

the concentration of oxygen in theinspired gases.

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Fluids and feeding

Oral feeding should be suspended in children with severe dyspnoea, but enteral nutrition may be continued via nasogastric tube. If abdominal distension occurs, feeding must be discontinued to avoid regurgitation and aspiration, and to prevent splinting of the diaphragm, as these may cause additional respiratory embarrassment. Intravenous infusion may supply fluids and parenteral nutrition, but total fluid intake may need to be restricted in some patients with pulmonary disease.

Sodium bicarbonate may be required to correct metabolic acidosis (Chapter2). Fluid management requires regular biochemical monitoring and an accurate record of fluid balance.

Temperature control

Seriously ill neonates are particularly vulnerable to cold stress, and consequently maintenance of body temperature is of vital importance (Chapter 2). The preterm neonate has a narrow ‘thermoneutral’ range in which oxygen consumption is minimised and optimal: abdominal wall skin temperature is optimal between 36 and

36.5 °C. Exposure to an environmental temperature of

°C increases oxygen consumption threefold and

20–25 may precipitate cardiorespiratory failure. Critically ill neonates should be nursed in open cots with servocontrolled radiant heat so that access to them is not compromised. Insensible water loss may be increased, particularly in neonates of very low birthweight, but this may be taken into account when planning fluid replacements.

Monitoring

Respiratory and cardiovascular signs should be monitored, along with the oxygen concentration in the inspired air. Blood for gas analysis is obtained by percutaneous puncture or, more accurately, in samples from an indwelling catheter in a peripheral artery, which also may be used for a continuous record of the arterial pressure. Continuous transcutaneous oximetry is routine.

Ventilatory support

In neonates, endotracheal intubation is the preferred type of artificial airway [Table4.3]. Tracheal tubes of appropriate size and composition may be left in situ for long periods with minimal adverse effects or complications.

Humidification of dry inspired gases is necessary to reduce the risk of viscid and retained sputum, atelectasis,

Table 4.3 Use of nasotracheal tube in neonates

Advantages Disadvantages

Provides patent

airway

Overcomes airway

obstruction

Allows tracheo-

bronchial toilet and suction

Facilitates

continuous positive airway pressure

Enables mechanical

ventilation

Narrows the upper airways

Bypasses natural humidification, heating

and filtering of inspired gases

Prevents coughing and expectoration of

secretions

May cause subglottic irritation and

stenosis (which may be minimised by a correct-sized tube, allowing a small air leak during positive-pressure ventilation)

blockage of the endotracheal tube with inspissated secretions and to preserve mucociliary function.

Inspired gases should be delivered to the trachea at 37 °C, fully saturated with water vapour, using a safe, servocontrolled humidifier to help maintain body temperature and reduce insensible fluid losses from the airways.

Regular suctioning of the trachea is necessary to stimulate coughing and to remove accumulated secretions. Suctioning may cause hypoxia and atelectasis and may introduce infection, and techniques are used to avoid these risks. Gentle ‘bagging’ with an oxygen-rich mixture is used before and after suction to reduce hypoxia and re-expand the lung. In neonates at risk of retinopathy of prematurity, the oxygen concentration in the ‘bag’ should not be more than 10% higher than the mixture used for ventilation. In older children 100% oxygen may be used.

Continuous positive airways pressure

Continuous positive airways pressure (CPAP) is a technique that employs a distending pressure (5–10 cm H

O) applied to the airways of a patient who is breathing spontaneously. It is used in pulmonary conditions causing hypoxaemia due to atelectasis, alveolar instability and intrapulmonary shunting. Continuous positive airways pressure increases functional residual capacity and compliance, re-expands areas of atelectasis, decreases intrapulmonary shunting and increases arterial pO

. In premature

neonates, CPAP will often improve the regularity of respiratory movements and decrease apnoeic episodes. The technique requires careful control to avoid reduced cardiac output, retention of fluids, rupture of alveoli and

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pneumothorax. Non-invasive CPAP, for example nasal CPAP, should also be used with caution in the neonate with bowel obstruction due to the potential for exacerbation of abdominal distension caused by aerophagia.

Intermittent positive-pressure ventilation

Intermittent positive-pressure ventilation (IPPV) is used to correct hypoventilation and, in some situations (e.g. raised intracranial pressure and pulmonary hypertension), to produce hyperventilation and to lower arterial

. Mechanical ventilators have been designed specifi-

pCO

cally for neonatal use. IPPV is often combined with positive end-expiratory pressure (PEEP). PEEP is used for the same reasons as CPAP, that is as a means of improving oxygenation. The hazards of IPPV are greater than those of CPAP and relate directly to the pressure applied. Barotrauma to immature lungs may result in a chronic lung disease in neonates known as bronchopulmonary dysplasia.

Intermittent mandatory ventilation is a technique of mechanical ventilation in which a predetermined minute volume is guaranteed, even when the patient breathes independently from the ventilator. With neonatal ventilators, a constant flow is provided during the expiratory phase from which the neonate may breathe. It is a technique useful for weaning from mechanical ventilation and as a means of minimising barotrauma.

Controlled ventilation involves the use of relaxants and sedatives which paralyse respiratory movements, to completely abolish the work of breathing and improve gas exchange. The technique is useful in critically ill neonates and those with difficult ventilatory problems, but it should only be employed where expert surveillance and sophisticated monitoring are available. Inappropriate pressure settings may cause a pneumothorax with sudden deterioration, and inadvertent disconnection rapidly results in potentially fatal hypoxia.

KEY POINTS

• Neonatal respiratory distress should be diagnosed by tachypnoea, before cyanosis appears.

• A surgical cause is present in the minority but may be identied by physical examination and chest x-ray.