DHCC Update




Neonatal resuscitation
– a continuing medical education course

 

Harvard Medical School Dubai Center (HMSDC) Institute for Postgraduate Education and Research recently held a national continuing medical education (CME) course on obstetrics and neonatal care. Dr Mohammad R. Cheikhali highlights key points from the neonatal resuscitation session.

Neonatal resuscitation

The resuscitation of neonates at birth is different to the resuscitation of all other age groups, and knowledge of the relevant physiology and pathophysiology is essential. Birth asphyxia accounts for about 19% of the approximately 5 million neonatal deaths that occur each year worldwide. The majority of babies born will establish normal respiration and circulation at delivery without help, however, approximately 10% of newborns require some assistance to begin breathing at birth with about 1% needing extensive resuscitative measures to survive. Ventilating the baby’s lungs with oxygen is the most important and effective action in cases of asphyxia. Therefore, it is essential that someone trained in complete newborn resuscitation should be present at all deliveries.

After birth, the fluid in the alveoli of the neonate is absorbed into the lung tissue and replaced by air. When the lungs are functioning, the umbilical vessels close and the blood vessels in the lung tissues relax. There are many factors that can potentially go wrong during this transition including, insufficient breathing that fails to force the fluid out of the alveoli, excessive blood loss or bradycardia resulting in systemic hypotension; or lack of oxygen or gaseous distention resulting in persistent pulmonary hypertension. Indeed, insufficient oxygen to various organs is the cause of many conditions in newborns including cyanosis, bradycardia, low blood pressure, depression of respiratory drive and poor muscle tone

The protocol for resuscitation can be memorised as “ABC” – Airways; Breathing and Circulation.

In other words a functional airway has to be secured followed by ventilation to commence spontaneous breathing and finally, circulation must be normalised (e.g. through external cardiac massage).

If asphyxiation continues, the neonate may enter an apnea phase known as primary apnea, which can be followed by a period of irregular gasping respirations, if the asphyxia continues. Continued asphyxia can lead to a period of unremitting apnea known as secondary apnea and will require positivepressure ventilation (PPV).




The Apgar score (Table 1) evaluates a newborn’s physical condition after delivery and conveys information about the newborn’s overall status and response to resuscitation. However, the Apgar score cannot be used to determine the need for resuscitation, resuscitation steps to be taken or when to use these steps.

There is an increased association with congenital abnormalities in babies who are small for gestational age or pre-term. Specific problems include perinatal asphyxia, lack of thermoregulation, increased susceptibility to infection and hemorrhage of the brain vasculature. These infants may particularly require initiation of or complete resuscitation at birth.

There are many factors that can be assessed in the newborn to determine whether it will need resuscitation, including whether the baby is crying or breathing; infant’s muscle tone; if it is born pre-term; and determining meconium in the amniotic fluid. However, these factors must be assessed within a few seconds after birth.

Meconium in the amniotic fluid may result in meconium aspiration i.e. when a neonate inhales a mixture of meconium (its first faeces present in the womb) and amniotic fluid. Meconium, if passed significantly in utero, stains the amniotic fluid dark green or black (Meconium stained amniotic fluid – MSAF). The inhaled meconium can partially or completely block the baby’s airways.

Although anecdotal data concerning the efficacy of intrapartum oropharyngeal and nasopharyngeal suctioning of MSAF are conflicting, the procedure is widely used. The CME course highlighted the fact that routine suctioning of term-gestation infants born through MSAF does not necessarily prevent MAS and consideration should be given to revision of present practice. It is recommended, though, if meconium is present and the newborn is not vigorous, to suction the baby’s trachea before proceeding with any other steps. If the newborn is vigorous, only the mouth and nose should be suctioned, followed by resuscitation as required. “Vigorous” is defined as a newborn that has strong respiratory efforts, good muscle tone and a heart rate greater than 100 beats per minute.

Resuscitation – initial steps


Initial steps to be taken if an infant is not breathing or gasping include drying and covering the baby, positioning its head correctly for ventilation and clearing the airways to initiate stimulation for breathing. Supplemental oxygen is to be provided as necessary to relieve cyanosis.

Free-flow oxygen is indicated for central cyanosis. Acceptable methods for administering freeflow oxygen are

● Oxygen mask held firmly over the baby’s face
● Mask from the flow-inflating bag or T-piece resuscitator held closely over the baby’s mouth and nose
● Oxygen tubing cupped closely over the baby’s mouth and nose

After strictly following the above steps for initial resuscitation, infant should be evaluated quickly for respirations, heart rate and colour.

Positive pressure ventilation (PPV)

PPV is initiated if effective respiration is not established within 10-15 seconds of stimulation. Indications for PPV are apnea or gasping, if heart rate is <100 BPM even if breathing spontaneously and cyanosis is persisting despite 100% oxygen saturation.

PPV can be delivered via self-inflating or anesthesia bags and masks. Although self-inflating bags do not require a gas source to operate, they must be used with an oxygen source and a reservoir to deliver high concentrations of oxygen. The advantages of the anaesthesia bag are that it delivers 100% oxygen to the infant and most are equipped with a pressure-limiting pop-off valve, avoiding excessive pressure. The mask should be of appropriate size. Initial breath delivered should be delivered at a peak pressure that is adequate to produce appropriate chest rise, which may be as high as 30 cm H2O. The pressures for subsequent breaths should also result in adequate chest rises. In infants with normal lungs, this is between 15-20 cm H2O and in infants with diseased or premature lungs it should be between 20-40 cm H2O. A rate of 40-60 BRM should be used and the infant re-assessed in 15-20 seconds. Increased heart rate is the primary sign of effective ventilation during resuscitation. Other signs include improved colour, spontaneous breathing, and improved muscle tone.

If there is not physiologic improvement and no perceptible chest expansion during assisted ventilation re-apply mask to face, reposition the head, check for secretions, suction mouth and nose, ventilate with mouth slightly open, increase pressure of ventilations and recheck or replace the resuscitation bag. In cases where bag-mask ventilation fails, devices such as laryngeal mask airway (LMA) can be used as an alternative for assisted ventilation.

Chest compressions


Once PPV is performed and lungs are adequately inflated, chest compressions may be needed to assist circulation. Indications for chest compression include a heart rate of <60 BPM despite ventilation for 15 to 30 seconds with 100% oxygen. The sternum should be compressed at a regular rate of 90 compressions/ min, while ventilating the infant at 30 BPM.

The 2-thumb, encirclinghands method of chest compression is usually preferred, with a depth of compression one third the anterior- posterior diameter of the chest and sufficient to generate a palpable pulse. Compressions and ventilation must be wellcoordinated so it is advisable that two individuals be performing these.

Intubation





Endotracheal (ET) intubation is indicated in events where there is a prolonged need for PPV or mask-bag ventilation has not been effective. Indications for ET intubation are demonstrated in Table 2. The ET tube size can be estimated using gestational age of the infant (ET tube size in mm = Gestational age in wks/10). Usual clinical methods used for confirming ET position include bilateral breath sound auscultation, chest movement visualisation, clouding of the ET tube, auscultation over the stomach, etc.

Vascular access


Ventilation techniques may further require pharmacological treatment, therefore, a newborn may require vascular access for administration of medication. Methods of vascular access include the umbilical vein or peripheral veins in the extremities or the scalp. Umbilical artery and subclavian veins should be avoided due to potential complications associated with these routes.

Medications


Drugs are rarely indicated in newborn resuscitation. However, if the heart rate remains <60 BPM despite adequate ventilation with 100% oxygen and chest compressions, administration of low-dose epinephrine or volume expansion, or both, may be indicated. Volume expansion is considered when blood loss is suspected and the infant has not responded adequately to other resuscitative measures.

Intravenous sodium bicarbonate, a base, has been used to reverse acidosis during newborn resuscitation for many years. However, it should be given only after establishment of adequate ventilation and circulation only in cases of severe metabolic acidosis.

Some resuscitation situations need special consideration. For example, naloxone is indicated for use in respiratory depression in neonates whose mothers had received opiates in labour. Noninitiation of resuscitation may be considered with confirmed lethal anomalies, such as anencephy, trisomy 13 or trisomy 18, as well as extreme prematurity, with birth weight <400 grammes and gestational age <23 weeks.

Conclusions

This article outlines the steps necessary to resuscitate neonates. It is essential that practitioners in this field complete courses that provide such information to be aware of the process for neonatal resuscitation if required. It is of note though that newborn resuscitation after birth carries a better prognosis than resuscitation of older children and adults.

 Date of upload: 31st March 2009

                                  
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