Anaesth Intens Care (1990), 18, 348-357
The Melbourne Chart Neonatal Resuscitation
A Logical Guide to
R. N. ROY·, AND F. R. BETHERASt
Division of Paediatrics, Royal Women's Hospital, Carlton, Victoria SUMMARY
Resuscitation ofthe asphyxiated infant is one ofthe great emergencies in medical practice. Properly done, it can save many lives and greatly reduce the morbidity resultingfrom hypoxic-ischaemic encephalopathy, but if it is ineptly performed, the effects of hypoxic-ischaemic encephalopathy may be accentuated, with resultant increased morbidity and even mortality. Other than paediatricians, few practitioners have regular experience in neonatal resuscitation: indeed many, including obstetricians, anaesthetists, general practitioners and midwives may only rarely face the problem of severe asphyxia. It is therefore essential for the occasional practitioner to have ready reference to a logical guide to resuscitation. We have designed such a guide which is widely distributed in delivery suites and operating theatres in Victoria. Its basic form has been in use for over a decade and it has recently been revised. Use of the chart assists the resuscitator to judge the level ofresuscitation required. It is our experience that much unnecessary intervention occurs at resuscitation, and we believe the methods outlined in this schematic chart represent a more conservative but logical approach to neonatal resuscitation. The chart is based on the pathophysiological changes that occur in perinatal asphyxia, directing the user to the appropriate manoeuvres required to correct those changes, depending on the degree ofasphyxia which is determined by clinical signs and by use of the Apgar score.
Key Words:
OBSTETRICS; NEONATAL RESUSCITATION:
Melbourne Chart, neonatal asphyxia
PATHOPHYSIOLOGY OF ASPHYXIA
TABLE 1
The strict definition of neonatal asphyxia is the failure to initiate breathing within 60 seconds of delivery with up to 5.7% of all deliveries falling into this category, I and 13.6% of all infants requiring some resuscitation. 2 Although cerebral hypoxic-ischaemic insult is the usual cause of neonatal asphyxia, there is a wide differential diagnosis for infants who either fail to breathe at birth or who remain hypoxic despite respiratory efforts. These are listed in Table 1. To understand the requirements for resuscitation of infants with asphyxia caused by intra partum hypoxia, it is important to understand the pathophysiological changes occurring. Obviously there is no human experimental model
Differential diagnosis of the asphyxiated newborn infant
'M.B., B.S., F.R.A.C.P. Director Newborn Emergency Transpon Service, Senior Paediatrician, Royal Women's Hospital, Melbourne. tM.B., B.S., F.R.C.O.G., F.R.A.C.O.G. Director of Paediatrics, Royal Women's Hospital, Melbourne. Address for Reprints: Or R. N. Roy, Senior Paediatrician, Royal Women's Hospital, Grattan Street, Carlton, Victoria 3053, Australia. Accepted for publication March 26, 1990
1. Hypoxia/ischaemia.
2. 3. 4. 5. 6. 7. 8. 9.
Drug depression. Perinatal trauma. Anaemia. Intrauterine infection. Congenital malformation. Extreme prematurity. Neuromuscular disorder. Inborn error of metabolism.
to study the effects of perinatal hypoxia: however there is a primate model which is based on acutely asphyxiating Rhesus monkeys at birth and studying their vital signs and blood gases. 3 Although the causation of hypoxia is different from that in the human neonate, nevertheless the findings seem to extrapolate well to the signs observed in humans (Figure 1). Immediately after the onset of asphyxia in the animal model, there is a brief series of respiratory efforts lasting up to a minute. During this phase the heart rate and blood pressure rise, the P a02 falls Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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TABLE 2 Features of primary and secondary apnoea
Sign
Normal
Primary apnoea
Secondary apnoea
Colour Heart rate Muscle tone Resuscitation required Response to resuscitation
Pink > IOO/min Good Nil
Blue 40-100/min May be some Simple Gasps before pink
Pale/grey < 40/min Absent Vigorous/urgent Pink before gasps
and the P aco2 rises. This is followed by a phase of apnoea - 'primary apnoea' - lasting from one to five minutes: the heart rate falls, the blood pressure rises further then steadily falls, the P a02 and pH fall further and the P aco2 rises more. There may still be some muscle tone; the infant is cyanosed, but the circulation is still adequate (this phase was previously recognised as 'asphyxia livida'). If the asphyxial insult is withdrawn, the infant would soon gasp spontaneously and slowly recover. This type of infant responds quickly to relatively simple measures of resuscitation. The next two phases are those of a gasping phase and secondary or terminal apnoea. In the gasping phase the infant takes irregular gasps of steadily decreasing frequency and amplitude until literally the 'last gasp' is taken. Beyond this is secondary apnoea, in which phase the infant will not spontaneously gasp, even if the asphyxial insult is removed. This infant requires urgent and vigorous resuscitation. During these last two phases, the heart rate and blood pressure have been falling further so that the circulation is now collapsed, the infant appears shocked and pale or grey (,asphyxia pallida') and is generally totally limp. The P ao 2 is close to zero, the PaC02 is well in excess of 100
mmHg and the pH often well below 7.0 as a result of combined respiratory and metabolic acidosis. The distinguishing features of the phases of 'primary apnoea' and 'secondary apnoea' are summarised in Table 2. Although there may be overlap, it is usually possible to distinguish the degree of asphyxia by noting these clinical features and thus to determine the degree of intervention required. THE APGAR SCORE
The Apgar score proposed in 1953 by the American anaesthesiologist, Virginia Apgar,4 is now widely used to assess the neonate's condition at birth. It grades five clinical features with scores of O-~ (Figure 2) at 1 and 5 minutes of age (and every five minutes thereafter until a normal score is obtained). The Apgar score reflects the stage of asphyxia as described above - the further advanced the asphyxial process, the lower the Apgar score. The one-minute Apgar score is a good measure of the degree of respiratory failure and thus the need for resuscitation, but is a relatively poor indicator APGAR SCORE SIGN
0
HEART RATE
ABSENT
RESPIRATION
ABSENT
TONE
FLACCID
1 min Smin 1
2
100
REGULAR
FAIR
GOOD
REFLEX NO POOR GOOD CRY IRRITABILITY RESPONSE RESPONSE COLOUR Tune From Onset of Asphyxia (min)
FIGURE
1. -
Neonatal response to asphyxia.
Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
FIGURE
CYANOSIS PERIPHERAL PALE CYANOSIS
2.-The Apgar Score Chart.
PINK
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R. N. ROY AND F. R. BETHERAS
NEONATAL RESUSCIT ATION*' • MINIMAL'INTEr:lFERENCE "~~~
• r:I~.Ht LA TE~AL POSTURE'2 .' ,DRY,;IMMEDIATELY oOA :.i/,:::PER RESPIRAIORYTRACT
• POSTURE 5min
• CUTANEOUS
STI~,U,lATION SIGN
",0
• TEMPERATURE CONTROL
2
0
• INTRA::'NASAL02 1':'2'lIniin ' RATE
100 Cl)
• FROG BREATHING*4
IRREGULAR GASPS TONE
FLACCID
FAIR
NO
POOR
RESPONSE RESPONSE
W
REGULAR
a..
• VENTILA TlON/ OXYGENATION
z
• CARDIAC OUTPUT
...J
(3 GOOD
GOOD CRY
a:a..
• NARCOTIC ANTAGONIST • BIOCHEMICAL CORRECTION • FOLLOW-UP CARE & OBSERVATION
IF NO RESPONSE BY 20 MINUTES*~ DISCONTINUE ·NOTES· '*1. USE OF THE CHART: ThIs chart uses the Apgar score to gUide the user to the appropriate level of resuscitation. The coloured sections approximately correspond to the infant's colour and also reflect the underlying pathophysiology: ii.
NORMAL infants (1 min. Apgar 8-10) are Quickly PINK MILDLY/MODERATELY DEPRESSED infants (1 min. Apgar 4-7) approximately correspond to those with primary apnoea, with intact circulation. and are BLUE SEVERELY DEPRESSED infants (1 min. Apgar 0-3) approximately correspond to those with secondary apnoea, with depressed circulation, and are GREY or WHITE
·2. POSTURE: For NORMAL and MILDLY DEPRESSED infants the RIGHT LATERAL posture creates a spontaneously clear airway and minimises the need for suction. The SUPINE posture is indicated once IPPV with bag and mask is required.
*3. WRAPS: The wrap used to "catch" the infant should be used for the initial drying, then immediately discarded and replaced by a 2nd warm wrap. *4. "FROG BREATHING": With intranasal O 2 at '-2 I/min. (dependmg on the infant's size), the nares and mouth are simultaneously closed for '-2 sec., thus forcing O 2 into the upper airway and stimulating Head's reflex. This causes a gasp in the majority of infants, sometimes followed by brief apnoea. The process may be repeated every few seconds until respiration IS established. Failure to eliCit a gasp within 30 seconds should lead to bag and mask ventilation. *5. RESPONSE: "NO RESPONSE" is defined as no assessable improvement m heart rate. pertusion. colour or spontanpous respiration. In practice If there has been no gasp by 20 min - provided there is no respiratory depression from narcotics or hyperventilation - then the outlook is universally bad, either from death or severe morbidity, and discontinuation of resuscitative efforts should be considered
PRODUCED BY THE DIVISION OF NEONATAL PAEDIATRICS AND THE DEPARTMENT OF AUDIO &VISUAL SERVICES. ROYAL WOMEN'S HOSPITAL MELBOURNE
FIGURE
3. -
The Melbourne Chart. Anaesthesia and Intensive Care. Vo!. 18. No. 3. August. 1990
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for the actual degree of the hypoxic-ischaemic insult and has poor correlation with eventual outcome. The score at five minutes is better correlated with the severity of hypoxic-ischaemic insult and thus with the long-term outcome. Note that one does not wait for one minute to take the Apgar score before commencing resuscitation; immediate assessment and appropriate action is required. THE MELBOURNE CHART
The design of the Melbourne Chart draws on the pathophysiology of asphyxia and the Apgar score for its design. The Apgar table is central to our chart and from it radiate three sections - 'NORMAL'. 'MILD TO MODERATE ASPHYXIA' and 'SEVERE ASPHYXIA'. These three sections are designated by Apgar scores at one minute of 8-10, 4-7 and 0-3 respectively; the second and third sections also loosely correspond to the phases of primary and secondary apnoea in the pathophysiological process of asphyxia, and are hence colour-coded BLUE for primary apnoea ('asphyxia livida') and GREY for secondary apnoea ('asphyxia pallida'); the NORMAL section is colour-coded PINK. The characteristics of infants in the three TABLE 3
Resuscitation equipment required
• • • • • • • • •
Resuscitation bed with radiant heater. Clock with second hand. Warm absorbent wraps x 2. Stethoscope. Oxygen supply. Suction apparatus with pressure gauge. Suction "Y" catheters sizes 6, 8, 10 Fr. Neonatai intra-nasal oxygen catheter 6 Fr. end-hole. Self-inflating bag (LaerdallPenlonlAmbu) or other bag and circuit with pressure gauge. • Face masks (Laerdal 0/0, 011 size). • Endotracheal tubes and connectors size 2.5, 3.0, 3.5 mm (Cole and Murphy). Tapes for securing tubes. • Laryngoscope and blades - Miller 0 - Seward 1 • Magill's forceps. • Umbilical venous catheter tray inc. U-V catheter. • Needles 19,21,23,25 gauge. • Drugs: - Sodium bicarbonate 8.4%. - Dextrose 10%. - Water for injection. - Sodium chloride 0.9%. - SPPS. - Narcan Neonatal. - Adrenaline 1: 10,000. - Vitamin K I . Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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sections have been summarised in Table 2. Note that while these descriptions are usually straightforward, there can be overlap between sections, and an indidual infant's response to initial resuscitation may change the categorization. The advantage of this chart over others is that the initial assessment of the infant quickly leads the resuscitator to the manoeuvres that may be required. This simplifies a process that is often presented as a maze of arrows and boxes and also reminds the resuscitator of the pathophysiology that requires correction.
Sections of the Chart 1. Principles This list is to remind the resuscitator of the steps to be considered. i. Equipment Check: The equipment we recommend is listed in Table 4. Choice of resuscitation bags and masks is discussed under the description of bag-and-mask ventilation. Additional drugs that some resuscitators recommend include calcium gluconate, atropine, isoprenaline or dopamine, frusemide, digoxin and THAM. It is essential that all doctors and midwives working in a delivery room are familiar with the whereabouts and use of the equipment and drugs and that both equipment and drugs are checked regularly. 11. Assessment: This is by assessment of clinical signs and Apgar score as previously described. iii. Posture and Airway are discussed under the care of the normal infant. IV. Temperature Control: A full discussion of the temperature control needs of the TABLE
4
Complications of asphyxia 1. 2. 3. 4.
5. 6. 7. 8. 9.
Respiratory failure. Cardiovascular failure. Temperature instability. Metabolic derangements: - hypoglycaemia - lactic acidosis - hypocalcaemia, hyponatraemia, hyperkalaemia - cerebral oedema/infarction/haemorrhage Convulsions. Inappropriate ADH secretion. Haematological derangements. Renal failure. Gastrointestinal complications.
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newly born infant is beyond the scope of this article. Suffice it to say that the newborn's skin temperature may drop rapidly if proper attention is not paid to temperature control. A warm, still environment is required and is best provided by a radiant heater over the resuscitation area. It helps to have the whole room warmed to over 30'C, but this is not acceptable in delivery suites. The ideal resuscitation room for high-risk infants is one next door to the delivery room with a temperature of over 30'C. Drying and covering the infant are discussed under the care of the normal infant. v. Ventilation, Oxygenation, Cardiac Output and Drug Therapy are discussed in later sections. VI. Follow-up Care: Infants who have started out with severe asphyxial depression (i.e. in the GREY section) are at very high risk of developing complications of asphyxia (Table 4), especially if they have not returned to normality by 5-10 minutes of age. They should thus be managed in at least a level 2 (Special Care) nursery for at least 48 hours. Infants requiring intubation and ventilation for more than five minutes should have the endotracheal tube left in situ and arrangements made for transfer of the infant to an intensive care unit. 5 2. Normal Infants (Chart Section PINK) These infants do not require any active intervention. Routine care includes the following manoeuvres i. Posture. The infant is placed in the lateral posture. This can be on the mother's abdomen, on the bed beside her, or on a resuscitation table. There is no need for head-down position which may even make breathing more difficult. The lateral posture allows a spontaneously clear airway, and is the best of the horizontal postures for allowing free diaphragmatic movement. 11. Airway. Routine aspiration of the upper airway is not required as it is normal for lung fluid to come bubbling out of the mouth and the lateral posture allows this to happen without airway obstruction (in contrast to the supine posture). Upper airway aspiration is indicated if(a) there is obviously excess secretion contributing to laboured respiration,
lll.
IV.
(b) the infant is apnoeic (see next two sections), (c) one is about to embark on Intermittent Positive Pressure Ventilation (see next two sections), (d) there is meconium or blood present. The presence of meconium or blood is a special case6 requiring that the delivery be stopped once the head is delivered, whether it be by the vaginal or abdominal route. The pharynx is then quickly but thoroughly sucked out before delivery of the remainder of the body ensuring that when the first breath is taken there is minimal meconium in the upper airway. Once delivery is complete there should be further clearing of the upper airway by mouth and nose aspiration. If meconium staining has been particularly heavy, direct laryngoscopy should be performed, and provided a skilled resuscitator is present, intubation and suction from the trachea should also be performed. Only then should ventilation be initiated. Finally the stomach should be aspirated to remove meconium that might be regurgitated. (Otherwise stomach aspiration is not a part of routine care.) Apart from the removal of meconium or blood, the nose should rarely, if ever, be sucked out in the normal infant as nasal suction traumatises the mucosa and may lead to reactive oedema and nasal obstruction over the next 48 hours. Drying and covering. The infant should be dried immediately with an absorbent cloth (we use flannel nappies). This wet cloth should be discarded to prevent loss of heat by evaporation, and the infant covered with another pre-warmed cloth to prevent heat loss by radiation, convection and evaporation. These same principles of drying and covering must be applied to all infants after birth, those requiring resuscitation having exposed only those parts that are required for the resuscitation. Mother-infant attachment. This is best achieved by having the baby lying on the mother's abdomen and/or chest. Some mothers request skin to skin contact. This is advantageous to the infant in that the mother is a good source of warmth: however, all other exposed parts of the infant must be dried and covered as above. Anaesthesia and Intensive Care, Vo!. 18, No. 3, August, 1990
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3. Mild to moderate depression (Chart Section BLUE) The infants are generally in primary apnoea, have intact circulation, perhaps some muscle tone, and usually respond to simple measures. The initial manoeuvres in this sequence are carried out with the infant in the right lateral posture as previously described. Steps in increasing order of complexity include ... 1. Superficial tactile stimulation. The act of drying the infant often provides enough tactile stimulation to initiate respiration. This may be augmented by flicking of the soles of the feet or giving the Vitamin K by injection. ii. Aspiration of the upper airway. This should be brief(five seconds is generally sufficient), and oropharyngeal suction is all that is required. iii. Administration of oxygen via an intranasal catheter. A 6 Fr. neonatal single end-hole intranasal catheter is inserted up to 2 cm, with an oxygen flow rate up to 1 l/min. This may initiate or improve breathing in infants who are apnoeic or hypoventilating, and also increases the inspired oxygen concentration. IV. 'Frog-Breathing (also called the 'Melbourne Method' of breathing: not to be confused with the frog-breathing used by some adults with partial respiratory paralysis). With the intranasal catheter in situ (inserted no further than 2 cm) and oxygen flowing at 1 l/min (infant still in the right lateral posture), the nares and mouth are closed simultaneously (Figure 4) for one to two seconds, thus forcing the oxygen to flow into the upper airways. This distends the upper airways and
FIGURE 4. -
'Frog' breathing.
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353
stimulates Head's paradoxical reflex 7.8 a gasp followed by brief apnoea. This gasp reflex can be repeatedly initiated until regular respiration is established. N.B. The aim of frog-breathing is to initiate Head's reflex, NOT to achieve effective aveolar ventilation. Many moderately depressed infants respond to this technique, which is simple for the occasional resuscitator. The 'frog-breathing' cycle should be tried every four to five seconds. If there is no reflex gasp within 20 seconds, the method should be abandoned in favour of bag and mask or bag and endotracheal tube ventilation. The inspiratory phase of 'frog-breathing' must NOT be held beyond two seconds (one second in a small premature infant) since with prolonged inspiration alveolar distension with the risk of pneumothorax may occur, as may gastric distension. Since many neonatal resuscitation circuits do not have pressure-limiting devices, the use of flow rates in excess of 1 lIminute intranasally may lead to transmission of excessive pressures to the lungs. Bag and Mask Ventilation (a) Equipment. All medical practitioners attending deliveries should be skilled in this technique and be familiar with the bags and masks available in the different suites they attend, since there are different points of technique with different circuits. Anaesthetists would be most familiar with the circuits and anaesthetic bags that require gas flow for distension. For neonatal resuscitation these bags should be 250-500 ml and must have a safety blow-off pressure value in the circuit and preferably also have a visible pressure gauge. Note that the tidal volume of the neonate is approximately 6 ml/kg (i.e. 20 ml for an average term infant). However, most other practitioners and midwives are more familiar with self-inflating bags such as the Penlon, Laerdal or Ambu. For a variety of reasons we believe the Laerdal· is superior, and is the most long-lasting, being made of silicon. These bags have in-built pressure safety valves,
R. N. ROY AND
354
and do not require gas for their operation, but the infant is best served by having an oxygen flow supplied. These bags are particularly useful when using mask ventilation. Note that self-inflating bags do not deliver any oxygen if there is oxygen attached but the bag is not being squeezed (the exception is the Laerdal bag if the reservoir is attached). There is a variety of masks available, e.g. Rendell-Baker, Bennett and Laerdal - again the Laerdal is superior. 9 (b) Technique. For effective bag and mask ventilation the infant should be in the supine posture with moderate neck extension. The oropharynx and nasopharynx are briefly aspirated, avoiding trauma by using Y-suction catheters of appropriate sizes (10 Fr. for mouth, 6 or 8 Fr. for nasal passages). In normal infants an oropharyngeal airway is generally not required. Oropharyngeal airways can present problems by being of the wrong size so that the distal end may be on the back of the tongue or behind the larynx in the oesophagus. The mask is applied to the face with only sufficient pressure to achieve an air tight fit, thus avoiding pressure trauma. If leaking around the mask occurs, the position should be shifted until the leak is minimised. If a small leak persists, it may be overcome by increasing the oxygen flow rate.
FIGURE
5. -
Correct position for bag and mask ventilation.
F. R. BETHERAS Ventilation is via the nasal passages with the mouth shut and the jaw pulled upwards and forwards (Figure 5). The ventilation rate should be 40-60/min. Oxygen flow rate to this circuit should be 5-10 l/min. The proof of adequate ventilation includes chest and upper abdominal movement, air entry, rising heart rate and improving colour. VI. Administration of naloxone. This may be indicated for the reversal of maternally administered opioid, usually pethidine. It is particularly pertinent if the opioid has been given within four hours of delivery or if there have been multiple doses, even if the last dose was more than four hours before delivery, as there may still be a high level of opioid attached to neonatal intracerebral lipid even after mother has excreted most of her opioid. Preterm infants are particularly susceptible to the effects of opioid depression. Intravenous naloxone should reach effective levels in two minutes, but intramuscular may take ten to twenty minutes depending on the state of the circulation. Naloxone given through the umbilical vein should be diluted in normal saline in sufficient volume to allow adequate entry into the general circulation. Other opioid antagonists such as nalorphine have been superseded by naloxone. There is no indication for the use of respiratory stimulants such as lobeline, nikethimide or vandid. 4. Severe Depression (Chart Section GREY) These infants are generally in secondary apnoea, are in shock, are flaccid and require immediate vigorous expert resuscitation. For optimal results, the resuscitation of the severely depressed infant requires a team effort together with electronic monitoring. If a lone resuscitator is present, the primary action required is establishment of ventilation while calling for assistance. i. Ventilation THE INSTITUTION OF ADEQUATE VENTILATION IS OF PARAMOUNT IMPORTANCE, AND TAKES PRECEDENCE OVER ALL OTHER MANOEUVRES. These infants are best ventilated via an endotracheal tube (ETT). However, if the resuscitator is not skilled in inserting AlIllI!SIhesia and Intensive Care, Vol. /8, No. 3, August, /990
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5
tubes are designed to prevent passage of the shoulders beyond the vocal cords, this is still all too easily achieved with intubation of the right mainstem bronchus. The ventilation rate, oxygen flow rate and assessment of adequacy of ventilation are as described above under bag and mask ventilation. The length of insertion of an ETT is given in Table 5. The position should always be confirmed by checking air entry and, if possible visualising the markings of the ETT at the vocal cords.
Endotracheal tube size and length Baby weight (kg)
< 1.0 1.0 2.0 3.0 3.5 4.0
Tube size (mm)
Oral at lip (cm)
Nasal at nose (cm)
Suction tube (Fr.)
2.5 2.5-3.0 3.0 3.0 3.0-3.5 3.5
5.5 6.0 7.0 8.5 9.0 9.0
7.0 7.5 9.0 10.5 11.0 11.0
6 6 6-7 6-7 8 8
ETTs in neonates, it is wiser to use bag and mask ventilation preferably with 100% oxygen, since unsuccessful intubation attempts may cause serious deterioration. Recommended ETT sizes are shown in Table 5. We find that for rapid resuscitation the oro-tracheal shouldered Cole tube is most effective; the proper insertion of Murphy naso-tracheal tubes calls for more experience. All neonatal ETTs have universal anaesthetic fittings allowing connection to all neonatal selfinflating bag systems. Although the shoulders of the Cole
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11.
Cardiovascular Support (a) External cardiac massage. The second urgent requirement for these infants is external cardiac massage (ECM) if the heart rate is less than 40 or inaudible. The two techniques recommended are described. 1. The fingers of both hands are placed on either side around the infant's back, while the thumbs are placed one on top of the other or one above the other in the midline on the lower sternum at the level of the nipples (Figure 6).
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R. N. ROY AND F.
2. The second and third fingers are placed one above the other over the lower sternum at the level of the nipples (Figure 6). With this technique great care must be taken that the fingers do not slip off the midline and cause costal fractures. The sternum should be vigorously depressed 1-1.5 cm at a rate of 120/minute. (b) Correction ofacidosis. 10,11 This is the next most important manoeuvre. (See under 'Biochemical Correction' .) (c) Volume expansion. To further support the shocked circulation, if adequate perfusion does not q';ric~y return, plasma volume expanSIOn IS required. Because of the ~olu~es required, it is unlikely that mf~s!on through a needle in the umbIlIcal vein will be successful, so an umbilical venous catheter will be necessary. Some important tech~ical points in this procedure are hsted below. 1. The umbilical vein turns sharply immediately inside the umbilicus, and travels subcutaneously in a cephalad direction and the catheter must be manipulated to allow for this. 2. The catheter may well not slip into the ductus venosus but pass into a hepatic vein. If this occ.urs, the catheter will stop at 8-10 cm. It must then be withdrawn to about 4 cm (especially if also infusing bicarbonate) to avoid infusion of concentrated solutions directly into a liver lobe. 3. The chances of entering the ductus venosus are greatly enhanced by fashioning a curve on the tip of the catheter and inserting the catheter with the tip curved anteriorly, since the ductus venosus takes off the anterior wall of the umbilical vein. 4. The catheter should be filled with a solution before insertion, preferably with a 3-way tap attached and turned off towards the patient to prevent air embolism.
R. BETHERAS 5. A purse-string silk suture around the base of the cord is recommended to prevent subsequent haemorrhage. The most appropriate plasma volume expander is colloid such as SPPS in a volume of 10 mlIkg, to be repeated once or twice depending on the response. Other solutions include the artificial plasma volume expande.rs, uncrossmatched O-negatlve blood or heparinised placental blood if blood loss is suspected. The vital signs should be monitored together with blood pressure and central ven.ous pressure, if the appropnate apparatus is available. lll.
Biochemical Correction (a) Sodium bicarbonate. In this group of severely depressed infants, if there is no quick response to adequa~e ventilation it is likely there IS associated severe metabolic acidosis. Administration of sodium bicarbonate must always follow the establishment of adequate ventilation to provide for adequate excretion of C02. Because of the high osmolality of molar bicarbonate, the solution should be diluted 1: 1 with either sterile water or glucose 10%; it should be given slowly over 10 minutes through the umbilical venous catheter or possibly through a needle in the vein. The initial dose is 3 mEq/kg of NaHC03 (6 mllkg of diluted solution), which may need to be repeated once or twice on the basis of subsequent blood gases. (b) Glucose. The need for glucose at resuscitation is controversial. The cord glucose level is usually normal or elevated, except in infants with poor glycogen stores such as small premature and growth-retarded infants. Glucose infusion is thus not required in mature well-nourished infants until an hour or two after resuscitation when hypoglycaemia may occur. (c) Calcium. Although we do not ourselves use it, some authors recommend the use of calcium (gluconate or chloride) to increase cardiac contractility. A1UU!SthesiIJ and Intensive Care. Vol. 18, No. 3, August. 1990
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(d) Adrenaline. For cardiac arrest or a heart rate less than 40/minute not responding to adequate ventilation and cardiac massage, I: 10,000 adrenaline at a dose of 0.1-0.3 mllkg may be given. The route may be via the ETT, the umbilical vein, or, as a last resort, by intracardiac injection (4th left intercostal space at the lower left sternal edge). 5. Discontinuation of resuscitation At the bottom of our chart is the advice 'IF NO RESPONSE AFTER 20 MINUTES DISCONTINUE'. Certainly if an infant with poor peripheral circulation has no spontaneous respiration after twenty minutes despite adequate resuscitation, then resuscitation should be discontinued due to the inevitable consequences of cerebral hypoxic-ischaemic damage. The more difficult problem is the infant whose circulation picks up but who fails to initiate respiration after twenty minutes of adequate resuscitation. If this is due to severe hypoxic-ischaemic insult then our experience is that the outcome is universally poor - either neonatal death or occasionally a severely handicapped survivor. There are isolated reports of infants who have taken longer to take the first breath and survived intact 12 but these are extremely rare and in some cases at least, the resuscitation may have been less than optimal. Before discontinuation of resuscitation one must be absolutely certain that respiratory depression is not due to sedation from maternal narcotics, overventilation from the resuscitation or rarely from an inherited neurological disorder. If this is certain, after discussion with the parents, resuscitation may be discontinued, allowing the parents to be with their infant if they so desire. Where the reason for the depression is uncertain and the response is incomplete, further assessment and management should be undertaken in a neonatal intensive care unit. In these last two situations, telephone consultation with a neonatal specialist is often helpful in deciding whether or not to continue treatment.
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CONCLUSION
The aim of the Melbourne Chart is to provide a framework for all birth attendants to be able quickly to assess the condition of newborn infants, to recognise the asphyxiated infant and the degree of asphyxia, and to provide a logical sequence of measures within their own competence for the care of all infants from the vigorous normal infant to the most severely depressed infant. Such a simple plan minimizes the tendency to panic and to take inappropriate actions, thus leading to the best possible outcomes for these at-risk infants.
REFERENCES
1. Gupta JM, Tizzard JPM. The sequence of events in neonatal apnoea. Lancet 1967; ii:55-59. 2. Russell G, Lydon Y, Tunstall M. Antenatal prediction of neonatal asphyxia. Anaesthesia 1975; 30:118. 3. Dawes GS, Jacobson HN, Mott JC, Shelley H. Some observations of foetal and new-born rhesus monkeys. J Physiol1960; 152:271-98. 4. Apgar V. A proposal for a new method of evaluation of the newborn infant. Anesth Analg 1953; 32:260. 5. Fletcher J, Shann F, Duncan A. The dangers of premature extubation after severe birth asphyxia. Aust Paediatr J 1987; 23, 1:27-29. 6. Ting P, Brady JP. Tracheal suction in meconium aspiration. Am J Obstet Gyneco11975; 122:767-771. 7. Head H. On the regulation of respiration. J Physiol 1889; 10:1-70. 8. Cross KW, Klaus M, Tooley WH, Weisser K. The response of the new-born baby to inflation of the lungs. J Physiol 1960; 151:551-65. 9. Palme C, Nystrbm B, Tunell R. An evaluation of the efficiency of face masks in the resuscitation of newborn infants. Lancet 1985; i:207-210. 10. Dawes GS, Jacobson HN, Mott JC, Shelley H, Stafford A. The treatment of asphyxiated mature foetal lambs and Rhesus monkeys with intravenous glucose and sodium bicarbonate. J Physiol 1963; 169: 167-84. 11. Adamsons K, Behrman R, Dawes GS, James LS, Koford C. Resuscitation by positive pressure ventilation and tris-hydroxymethylaminomethane of Rhesus monkeys asphyxiated at birth. J Pediat 1964; 65:801-806. 12. Bullough J. Protracted foetal and neonatal asphyxia. Lancet 1958; i:999.
The Melbourne Chart Neonatal Resuscitation
A Logical Guide to
R. N. ROY·, AND F. R. BETHERASt
Division of Paediatrics, Royal Women's Hospital, Carlton, Victoria SUMMARY
Resuscitation ofthe asphyxiated infant is one ofthe great emergencies in medical practice. Properly done, it can save many lives and greatly reduce the morbidity resultingfrom hypoxic-ischaemic encephalopathy, but if it is ineptly performed, the effects of hypoxic-ischaemic encephalopathy may be accentuated, with resultant increased morbidity and even mortality. Other than paediatricians, few practitioners have regular experience in neonatal resuscitation: indeed many, including obstetricians, anaesthetists, general practitioners and midwives may only rarely face the problem of severe asphyxia. It is therefore essential for the occasional practitioner to have ready reference to a logical guide to resuscitation. We have designed such a guide which is widely distributed in delivery suites and operating theatres in Victoria. Its basic form has been in use for over a decade and it has recently been revised. Use of the chart assists the resuscitator to judge the level ofresuscitation required. It is our experience that much unnecessary intervention occurs at resuscitation, and we believe the methods outlined in this schematic chart represent a more conservative but logical approach to neonatal resuscitation. The chart is based on the pathophysiological changes that occur in perinatal asphyxia, directing the user to the appropriate manoeuvres required to correct those changes, depending on the degree ofasphyxia which is determined by clinical signs and by use of the Apgar score.
Key Words:
OBSTETRICS; NEONATAL RESUSCITATION:
Melbourne Chart, neonatal asphyxia
PATHOPHYSIOLOGY OF ASPHYXIA
TABLE 1
The strict definition of neonatal asphyxia is the failure to initiate breathing within 60 seconds of delivery with up to 5.7% of all deliveries falling into this category, I and 13.6% of all infants requiring some resuscitation. 2 Although cerebral hypoxic-ischaemic insult is the usual cause of neonatal asphyxia, there is a wide differential diagnosis for infants who either fail to breathe at birth or who remain hypoxic despite respiratory efforts. These are listed in Table 1. To understand the requirements for resuscitation of infants with asphyxia caused by intra partum hypoxia, it is important to understand the pathophysiological changes occurring. Obviously there is no human experimental model
Differential diagnosis of the asphyxiated newborn infant
'M.B., B.S., F.R.A.C.P. Director Newborn Emergency Transpon Service, Senior Paediatrician, Royal Women's Hospital, Melbourne. tM.B., B.S., F.R.C.O.G., F.R.A.C.O.G. Director of Paediatrics, Royal Women's Hospital, Melbourne. Address for Reprints: Or R. N. Roy, Senior Paediatrician, Royal Women's Hospital, Grattan Street, Carlton, Victoria 3053, Australia. Accepted for publication March 26, 1990
1. Hypoxia/ischaemia.
2. 3. 4. 5. 6. 7. 8. 9.
Drug depression. Perinatal trauma. Anaemia. Intrauterine infection. Congenital malformation. Extreme prematurity. Neuromuscular disorder. Inborn error of metabolism.
to study the effects of perinatal hypoxia: however there is a primate model which is based on acutely asphyxiating Rhesus monkeys at birth and studying their vital signs and blood gases. 3 Although the causation of hypoxia is different from that in the human neonate, nevertheless the findings seem to extrapolate well to the signs observed in humans (Figure 1). Immediately after the onset of asphyxia in the animal model, there is a brief series of respiratory efforts lasting up to a minute. During this phase the heart rate and blood pressure rise, the P a02 falls Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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TABLE 2 Features of primary and secondary apnoea
Sign
Normal
Primary apnoea
Secondary apnoea
Colour Heart rate Muscle tone Resuscitation required Response to resuscitation
Pink > IOO/min Good Nil
Blue 40-100/min May be some Simple Gasps before pink
Pale/grey < 40/min Absent Vigorous/urgent Pink before gasps
and the P aco2 rises. This is followed by a phase of apnoea - 'primary apnoea' - lasting from one to five minutes: the heart rate falls, the blood pressure rises further then steadily falls, the P a02 and pH fall further and the P aco2 rises more. There may still be some muscle tone; the infant is cyanosed, but the circulation is still adequate (this phase was previously recognised as 'asphyxia livida'). If the asphyxial insult is withdrawn, the infant would soon gasp spontaneously and slowly recover. This type of infant responds quickly to relatively simple measures of resuscitation. The next two phases are those of a gasping phase and secondary or terminal apnoea. In the gasping phase the infant takes irregular gasps of steadily decreasing frequency and amplitude until literally the 'last gasp' is taken. Beyond this is secondary apnoea, in which phase the infant will not spontaneously gasp, even if the asphyxial insult is removed. This infant requires urgent and vigorous resuscitation. During these last two phases, the heart rate and blood pressure have been falling further so that the circulation is now collapsed, the infant appears shocked and pale or grey (,asphyxia pallida') and is generally totally limp. The P ao 2 is close to zero, the PaC02 is well in excess of 100
mmHg and the pH often well below 7.0 as a result of combined respiratory and metabolic acidosis. The distinguishing features of the phases of 'primary apnoea' and 'secondary apnoea' are summarised in Table 2. Although there may be overlap, it is usually possible to distinguish the degree of asphyxia by noting these clinical features and thus to determine the degree of intervention required. THE APGAR SCORE
The Apgar score proposed in 1953 by the American anaesthesiologist, Virginia Apgar,4 is now widely used to assess the neonate's condition at birth. It grades five clinical features with scores of O-~ (Figure 2) at 1 and 5 minutes of age (and every five minutes thereafter until a normal score is obtained). The Apgar score reflects the stage of asphyxia as described above - the further advanced the asphyxial process, the lower the Apgar score. The one-minute Apgar score is a good measure of the degree of respiratory failure and thus the need for resuscitation, but is a relatively poor indicator APGAR SCORE SIGN
0
HEART RATE
ABSENT
RESPIRATION
ABSENT
TONE
FLACCID
1 min Smin 1
2
100
REGULAR
FAIR
GOOD
REFLEX NO POOR GOOD CRY IRRITABILITY RESPONSE RESPONSE COLOUR Tune From Onset of Asphyxia (min)
FIGURE
1. -
Neonatal response to asphyxia.
Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
FIGURE
CYANOSIS PERIPHERAL PALE CYANOSIS
2.-The Apgar Score Chart.
PINK
350
R. N. ROY AND F. R. BETHERAS
NEONATAL RESUSCIT ATION*' • MINIMAL'INTEr:lFERENCE "~~~
• r:I~.Ht LA TE~AL POSTURE'2 .' ,DRY,;IMMEDIATELY oOA :.i/,:::PER RESPIRAIORYTRACT
• POSTURE 5min
• CUTANEOUS
STI~,U,lATION SIGN
",0
• TEMPERATURE CONTROL
2
0
• INTRA::'NASAL02 1':'2'lIniin ' RATE
100 Cl)
• FROG BREATHING*4
IRREGULAR GASPS TONE
FLACCID
FAIR
NO
POOR
RESPONSE RESPONSE
W
REGULAR
a..
• VENTILA TlON/ OXYGENATION
z
• CARDIAC OUTPUT
...J
(3 GOOD
GOOD CRY
a:a..
• NARCOTIC ANTAGONIST • BIOCHEMICAL CORRECTION • FOLLOW-UP CARE & OBSERVATION
IF NO RESPONSE BY 20 MINUTES*~ DISCONTINUE ·NOTES· '*1. USE OF THE CHART: ThIs chart uses the Apgar score to gUide the user to the appropriate level of resuscitation. The coloured sections approximately correspond to the infant's colour and also reflect the underlying pathophysiology: ii.
NORMAL infants (1 min. Apgar 8-10) are Quickly PINK MILDLY/MODERATELY DEPRESSED infants (1 min. Apgar 4-7) approximately correspond to those with primary apnoea, with intact circulation. and are BLUE SEVERELY DEPRESSED infants (1 min. Apgar 0-3) approximately correspond to those with secondary apnoea, with depressed circulation, and are GREY or WHITE
·2. POSTURE: For NORMAL and MILDLY DEPRESSED infants the RIGHT LATERAL posture creates a spontaneously clear airway and minimises the need for suction. The SUPINE posture is indicated once IPPV with bag and mask is required.
*3. WRAPS: The wrap used to "catch" the infant should be used for the initial drying, then immediately discarded and replaced by a 2nd warm wrap. *4. "FROG BREATHING": With intranasal O 2 at '-2 I/min. (dependmg on the infant's size), the nares and mouth are simultaneously closed for '-2 sec., thus forcing O 2 into the upper airway and stimulating Head's reflex. This causes a gasp in the majority of infants, sometimes followed by brief apnoea. The process may be repeated every few seconds until respiration IS established. Failure to eliCit a gasp within 30 seconds should lead to bag and mask ventilation. *5. RESPONSE: "NO RESPONSE" is defined as no assessable improvement m heart rate. pertusion. colour or spontanpous respiration. In practice If there has been no gasp by 20 min - provided there is no respiratory depression from narcotics or hyperventilation - then the outlook is universally bad, either from death or severe morbidity, and discontinuation of resuscitative efforts should be considered
PRODUCED BY THE DIVISION OF NEONATAL PAEDIATRICS AND THE DEPARTMENT OF AUDIO &VISUAL SERVICES. ROYAL WOMEN'S HOSPITAL MELBOURNE
FIGURE
3. -
The Melbourne Chart. Anaesthesia and Intensive Care. Vo!. 18. No. 3. August. 1990
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for the actual degree of the hypoxic-ischaemic insult and has poor correlation with eventual outcome. The score at five minutes is better correlated with the severity of hypoxic-ischaemic insult and thus with the long-term outcome. Note that one does not wait for one minute to take the Apgar score before commencing resuscitation; immediate assessment and appropriate action is required. THE MELBOURNE CHART
The design of the Melbourne Chart draws on the pathophysiology of asphyxia and the Apgar score for its design. The Apgar table is central to our chart and from it radiate three sections - 'NORMAL'. 'MILD TO MODERATE ASPHYXIA' and 'SEVERE ASPHYXIA'. These three sections are designated by Apgar scores at one minute of 8-10, 4-7 and 0-3 respectively; the second and third sections also loosely correspond to the phases of primary and secondary apnoea in the pathophysiological process of asphyxia, and are hence colour-coded BLUE for primary apnoea ('asphyxia livida') and GREY for secondary apnoea ('asphyxia pallida'); the NORMAL section is colour-coded PINK. The characteristics of infants in the three TABLE 3
Resuscitation equipment required
• • • • • • • • •
Resuscitation bed with radiant heater. Clock with second hand. Warm absorbent wraps x 2. Stethoscope. Oxygen supply. Suction apparatus with pressure gauge. Suction "Y" catheters sizes 6, 8, 10 Fr. Neonatai intra-nasal oxygen catheter 6 Fr. end-hole. Self-inflating bag (LaerdallPenlonlAmbu) or other bag and circuit with pressure gauge. • Face masks (Laerdal 0/0, 011 size). • Endotracheal tubes and connectors size 2.5, 3.0, 3.5 mm (Cole and Murphy). Tapes for securing tubes. • Laryngoscope and blades - Miller 0 - Seward 1 • Magill's forceps. • Umbilical venous catheter tray inc. U-V catheter. • Needles 19,21,23,25 gauge. • Drugs: - Sodium bicarbonate 8.4%. - Dextrose 10%. - Water for injection. - Sodium chloride 0.9%. - SPPS. - Narcan Neonatal. - Adrenaline 1: 10,000. - Vitamin K I . Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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sections have been summarised in Table 2. Note that while these descriptions are usually straightforward, there can be overlap between sections, and an indidual infant's response to initial resuscitation may change the categorization. The advantage of this chart over others is that the initial assessment of the infant quickly leads the resuscitator to the manoeuvres that may be required. This simplifies a process that is often presented as a maze of arrows and boxes and also reminds the resuscitator of the pathophysiology that requires correction.
Sections of the Chart 1. Principles This list is to remind the resuscitator of the steps to be considered. i. Equipment Check: The equipment we recommend is listed in Table 4. Choice of resuscitation bags and masks is discussed under the description of bag-and-mask ventilation. Additional drugs that some resuscitators recommend include calcium gluconate, atropine, isoprenaline or dopamine, frusemide, digoxin and THAM. It is essential that all doctors and midwives working in a delivery room are familiar with the whereabouts and use of the equipment and drugs and that both equipment and drugs are checked regularly. 11. Assessment: This is by assessment of clinical signs and Apgar score as previously described. iii. Posture and Airway are discussed under the care of the normal infant. IV. Temperature Control: A full discussion of the temperature control needs of the TABLE
4
Complications of asphyxia 1. 2. 3. 4.
5. 6. 7. 8. 9.
Respiratory failure. Cardiovascular failure. Temperature instability. Metabolic derangements: - hypoglycaemia - lactic acidosis - hypocalcaemia, hyponatraemia, hyperkalaemia - cerebral oedema/infarction/haemorrhage Convulsions. Inappropriate ADH secretion. Haematological derangements. Renal failure. Gastrointestinal complications.
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newly born infant is beyond the scope of this article. Suffice it to say that the newborn's skin temperature may drop rapidly if proper attention is not paid to temperature control. A warm, still environment is required and is best provided by a radiant heater over the resuscitation area. It helps to have the whole room warmed to over 30'C, but this is not acceptable in delivery suites. The ideal resuscitation room for high-risk infants is one next door to the delivery room with a temperature of over 30'C. Drying and covering the infant are discussed under the care of the normal infant. v. Ventilation, Oxygenation, Cardiac Output and Drug Therapy are discussed in later sections. VI. Follow-up Care: Infants who have started out with severe asphyxial depression (i.e. in the GREY section) are at very high risk of developing complications of asphyxia (Table 4), especially if they have not returned to normality by 5-10 minutes of age. They should thus be managed in at least a level 2 (Special Care) nursery for at least 48 hours. Infants requiring intubation and ventilation for more than five minutes should have the endotracheal tube left in situ and arrangements made for transfer of the infant to an intensive care unit. 5 2. Normal Infants (Chart Section PINK) These infants do not require any active intervention. Routine care includes the following manoeuvres i. Posture. The infant is placed in the lateral posture. This can be on the mother's abdomen, on the bed beside her, or on a resuscitation table. There is no need for head-down position which may even make breathing more difficult. The lateral posture allows a spontaneously clear airway, and is the best of the horizontal postures for allowing free diaphragmatic movement. 11. Airway. Routine aspiration of the upper airway is not required as it is normal for lung fluid to come bubbling out of the mouth and the lateral posture allows this to happen without airway obstruction (in contrast to the supine posture). Upper airway aspiration is indicated if(a) there is obviously excess secretion contributing to laboured respiration,
lll.
IV.
(b) the infant is apnoeic (see next two sections), (c) one is about to embark on Intermittent Positive Pressure Ventilation (see next two sections), (d) there is meconium or blood present. The presence of meconium or blood is a special case6 requiring that the delivery be stopped once the head is delivered, whether it be by the vaginal or abdominal route. The pharynx is then quickly but thoroughly sucked out before delivery of the remainder of the body ensuring that when the first breath is taken there is minimal meconium in the upper airway. Once delivery is complete there should be further clearing of the upper airway by mouth and nose aspiration. If meconium staining has been particularly heavy, direct laryngoscopy should be performed, and provided a skilled resuscitator is present, intubation and suction from the trachea should also be performed. Only then should ventilation be initiated. Finally the stomach should be aspirated to remove meconium that might be regurgitated. (Otherwise stomach aspiration is not a part of routine care.) Apart from the removal of meconium or blood, the nose should rarely, if ever, be sucked out in the normal infant as nasal suction traumatises the mucosa and may lead to reactive oedema and nasal obstruction over the next 48 hours. Drying and covering. The infant should be dried immediately with an absorbent cloth (we use flannel nappies). This wet cloth should be discarded to prevent loss of heat by evaporation, and the infant covered with another pre-warmed cloth to prevent heat loss by radiation, convection and evaporation. These same principles of drying and covering must be applied to all infants after birth, those requiring resuscitation having exposed only those parts that are required for the resuscitation. Mother-infant attachment. This is best achieved by having the baby lying on the mother's abdomen and/or chest. Some mothers request skin to skin contact. This is advantageous to the infant in that the mother is a good source of warmth: however, all other exposed parts of the infant must be dried and covered as above. Anaesthesia and Intensive Care, Vo!. 18, No. 3, August, 1990
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3. Mild to moderate depression (Chart Section BLUE) The infants are generally in primary apnoea, have intact circulation, perhaps some muscle tone, and usually respond to simple measures. The initial manoeuvres in this sequence are carried out with the infant in the right lateral posture as previously described. Steps in increasing order of complexity include ... 1. Superficial tactile stimulation. The act of drying the infant often provides enough tactile stimulation to initiate respiration. This may be augmented by flicking of the soles of the feet or giving the Vitamin K by injection. ii. Aspiration of the upper airway. This should be brief(five seconds is generally sufficient), and oropharyngeal suction is all that is required. iii. Administration of oxygen via an intranasal catheter. A 6 Fr. neonatal single end-hole intranasal catheter is inserted up to 2 cm, with an oxygen flow rate up to 1 l/min. This may initiate or improve breathing in infants who are apnoeic or hypoventilating, and also increases the inspired oxygen concentration. IV. 'Frog-Breathing (also called the 'Melbourne Method' of breathing: not to be confused with the frog-breathing used by some adults with partial respiratory paralysis). With the intranasal catheter in situ (inserted no further than 2 cm) and oxygen flowing at 1 l/min (infant still in the right lateral posture), the nares and mouth are closed simultaneously (Figure 4) for one to two seconds, thus forcing the oxygen to flow into the upper airways. This distends the upper airways and
FIGURE 4. -
'Frog' breathing.
A1UU!Sthesia and Intensive Care. Vol. 18, No. 3. August. 1990
v.
353
stimulates Head's paradoxical reflex 7.8 a gasp followed by brief apnoea. This gasp reflex can be repeatedly initiated until regular respiration is established. N.B. The aim of frog-breathing is to initiate Head's reflex, NOT to achieve effective aveolar ventilation. Many moderately depressed infants respond to this technique, which is simple for the occasional resuscitator. The 'frog-breathing' cycle should be tried every four to five seconds. If there is no reflex gasp within 20 seconds, the method should be abandoned in favour of bag and mask or bag and endotracheal tube ventilation. The inspiratory phase of 'frog-breathing' must NOT be held beyond two seconds (one second in a small premature infant) since with prolonged inspiration alveolar distension with the risk of pneumothorax may occur, as may gastric distension. Since many neonatal resuscitation circuits do not have pressure-limiting devices, the use of flow rates in excess of 1 lIminute intranasally may lead to transmission of excessive pressures to the lungs. Bag and Mask Ventilation (a) Equipment. All medical practitioners attending deliveries should be skilled in this technique and be familiar with the bags and masks available in the different suites they attend, since there are different points of technique with different circuits. Anaesthetists would be most familiar with the circuits and anaesthetic bags that require gas flow for distension. For neonatal resuscitation these bags should be 250-500 ml and must have a safety blow-off pressure value in the circuit and preferably also have a visible pressure gauge. Note that the tidal volume of the neonate is approximately 6 ml/kg (i.e. 20 ml for an average term infant). However, most other practitioners and midwives are more familiar with self-inflating bags such as the Penlon, Laerdal or Ambu. For a variety of reasons we believe the Laerdal· is superior, and is the most long-lasting, being made of silicon. These bags have in-built pressure safety valves,
R. N. ROY AND
354
and do not require gas for their operation, but the infant is best served by having an oxygen flow supplied. These bags are particularly useful when using mask ventilation. Note that self-inflating bags do not deliver any oxygen if there is oxygen attached but the bag is not being squeezed (the exception is the Laerdal bag if the reservoir is attached). There is a variety of masks available, e.g. Rendell-Baker, Bennett and Laerdal - again the Laerdal is superior. 9 (b) Technique. For effective bag and mask ventilation the infant should be in the supine posture with moderate neck extension. The oropharynx and nasopharynx are briefly aspirated, avoiding trauma by using Y-suction catheters of appropriate sizes (10 Fr. for mouth, 6 or 8 Fr. for nasal passages). In normal infants an oropharyngeal airway is generally not required. Oropharyngeal airways can present problems by being of the wrong size so that the distal end may be on the back of the tongue or behind the larynx in the oesophagus. The mask is applied to the face with only sufficient pressure to achieve an air tight fit, thus avoiding pressure trauma. If leaking around the mask occurs, the position should be shifted until the leak is minimised. If a small leak persists, it may be overcome by increasing the oxygen flow rate.
FIGURE
5. -
Correct position for bag and mask ventilation.
F. R. BETHERAS Ventilation is via the nasal passages with the mouth shut and the jaw pulled upwards and forwards (Figure 5). The ventilation rate should be 40-60/min. Oxygen flow rate to this circuit should be 5-10 l/min. The proof of adequate ventilation includes chest and upper abdominal movement, air entry, rising heart rate and improving colour. VI. Administration of naloxone. This may be indicated for the reversal of maternally administered opioid, usually pethidine. It is particularly pertinent if the opioid has been given within four hours of delivery or if there have been multiple doses, even if the last dose was more than four hours before delivery, as there may still be a high level of opioid attached to neonatal intracerebral lipid even after mother has excreted most of her opioid. Preterm infants are particularly susceptible to the effects of opioid depression. Intravenous naloxone should reach effective levels in two minutes, but intramuscular may take ten to twenty minutes depending on the state of the circulation. Naloxone given through the umbilical vein should be diluted in normal saline in sufficient volume to allow adequate entry into the general circulation. Other opioid antagonists such as nalorphine have been superseded by naloxone. There is no indication for the use of respiratory stimulants such as lobeline, nikethimide or vandid. 4. Severe Depression (Chart Section GREY) These infants are generally in secondary apnoea, are in shock, are flaccid and require immediate vigorous expert resuscitation. For optimal results, the resuscitation of the severely depressed infant requires a team effort together with electronic monitoring. If a lone resuscitator is present, the primary action required is establishment of ventilation while calling for assistance. i. Ventilation THE INSTITUTION OF ADEQUATE VENTILATION IS OF PARAMOUNT IMPORTANCE, AND TAKES PRECEDENCE OVER ALL OTHER MANOEUVRES. These infants are best ventilated via an endotracheal tube (ETT). However, if the resuscitator is not skilled in inserting AlIllI!SIhesia and Intensive Care, Vol. /8, No. 3, August, /990
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5
tubes are designed to prevent passage of the shoulders beyond the vocal cords, this is still all too easily achieved with intubation of the right mainstem bronchus. The ventilation rate, oxygen flow rate and assessment of adequacy of ventilation are as described above under bag and mask ventilation. The length of insertion of an ETT is given in Table 5. The position should always be confirmed by checking air entry and, if possible visualising the markings of the ETT at the vocal cords.
Endotracheal tube size and length Baby weight (kg)
< 1.0 1.0 2.0 3.0 3.5 4.0
Tube size (mm)
Oral at lip (cm)
Nasal at nose (cm)
Suction tube (Fr.)
2.5 2.5-3.0 3.0 3.0 3.0-3.5 3.5
5.5 6.0 7.0 8.5 9.0 9.0
7.0 7.5 9.0 10.5 11.0 11.0
6 6 6-7 6-7 8 8
ETTs in neonates, it is wiser to use bag and mask ventilation preferably with 100% oxygen, since unsuccessful intubation attempts may cause serious deterioration. Recommended ETT sizes are shown in Table 5. We find that for rapid resuscitation the oro-tracheal shouldered Cole tube is most effective; the proper insertion of Murphy naso-tracheal tubes calls for more experience. All neonatal ETTs have universal anaesthetic fittings allowing connection to all neonatal selfinflating bag systems. Although the shoulders of the Cole
ATllUSthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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11.
Cardiovascular Support (a) External cardiac massage. The second urgent requirement for these infants is external cardiac massage (ECM) if the heart rate is less than 40 or inaudible. The two techniques recommended are described. 1. The fingers of both hands are placed on either side around the infant's back, while the thumbs are placed one on top of the other or one above the other in the midline on the lower sternum at the level of the nipples (Figure 6).
356
R. N. ROY AND F.
2. The second and third fingers are placed one above the other over the lower sternum at the level of the nipples (Figure 6). With this technique great care must be taken that the fingers do not slip off the midline and cause costal fractures. The sternum should be vigorously depressed 1-1.5 cm at a rate of 120/minute. (b) Correction ofacidosis. 10,11 This is the next most important manoeuvre. (See under 'Biochemical Correction' .) (c) Volume expansion. To further support the shocked circulation, if adequate perfusion does not q';ric~y return, plasma volume expanSIOn IS required. Because of the ~olu~es required, it is unlikely that mf~s!on through a needle in the umbIlIcal vein will be successful, so an umbilical venous catheter will be necessary. Some important tech~ical points in this procedure are hsted below. 1. The umbilical vein turns sharply immediately inside the umbilicus, and travels subcutaneously in a cephalad direction and the catheter must be manipulated to allow for this. 2. The catheter may well not slip into the ductus venosus but pass into a hepatic vein. If this occ.urs, the catheter will stop at 8-10 cm. It must then be withdrawn to about 4 cm (especially if also infusing bicarbonate) to avoid infusion of concentrated solutions directly into a liver lobe. 3. The chances of entering the ductus venosus are greatly enhanced by fashioning a curve on the tip of the catheter and inserting the catheter with the tip curved anteriorly, since the ductus venosus takes off the anterior wall of the umbilical vein. 4. The catheter should be filled with a solution before insertion, preferably with a 3-way tap attached and turned off towards the patient to prevent air embolism.
R. BETHERAS 5. A purse-string silk suture around the base of the cord is recommended to prevent subsequent haemorrhage. The most appropriate plasma volume expander is colloid such as SPPS in a volume of 10 mlIkg, to be repeated once or twice depending on the response. Other solutions include the artificial plasma volume expande.rs, uncrossmatched O-negatlve blood or heparinised placental blood if blood loss is suspected. The vital signs should be monitored together with blood pressure and central ven.ous pressure, if the appropnate apparatus is available. lll.
Biochemical Correction (a) Sodium bicarbonate. In this group of severely depressed infants, if there is no quick response to adequa~e ventilation it is likely there IS associated severe metabolic acidosis. Administration of sodium bicarbonate must always follow the establishment of adequate ventilation to provide for adequate excretion of C02. Because of the high osmolality of molar bicarbonate, the solution should be diluted 1: 1 with either sterile water or glucose 10%; it should be given slowly over 10 minutes through the umbilical venous catheter or possibly through a needle in the vein. The initial dose is 3 mEq/kg of NaHC03 (6 mllkg of diluted solution), which may need to be repeated once or twice on the basis of subsequent blood gases. (b) Glucose. The need for glucose at resuscitation is controversial. The cord glucose level is usually normal or elevated, except in infants with poor glycogen stores such as small premature and growth-retarded infants. Glucose infusion is thus not required in mature well-nourished infants until an hour or two after resuscitation when hypoglycaemia may occur. (c) Calcium. Although we do not ourselves use it, some authors recommend the use of calcium (gluconate or chloride) to increase cardiac contractility. A1UU!SthesiIJ and Intensive Care. Vol. 18, No. 3, August. 1990
SYMPOSIUM -
OBSTETRIC ANAESTHESIA
(d) Adrenaline. For cardiac arrest or a heart rate less than 40/minute not responding to adequate ventilation and cardiac massage, I: 10,000 adrenaline at a dose of 0.1-0.3 mllkg may be given. The route may be via the ETT, the umbilical vein, or, as a last resort, by intracardiac injection (4th left intercostal space at the lower left sternal edge). 5. Discontinuation of resuscitation At the bottom of our chart is the advice 'IF NO RESPONSE AFTER 20 MINUTES DISCONTINUE'. Certainly if an infant with poor peripheral circulation has no spontaneous respiration after twenty minutes despite adequate resuscitation, then resuscitation should be discontinued due to the inevitable consequences of cerebral hypoxic-ischaemic damage. The more difficult problem is the infant whose circulation picks up but who fails to initiate respiration after twenty minutes of adequate resuscitation. If this is due to severe hypoxic-ischaemic insult then our experience is that the outcome is universally poor - either neonatal death or occasionally a severely handicapped survivor. There are isolated reports of infants who have taken longer to take the first breath and survived intact 12 but these are extremely rare and in some cases at least, the resuscitation may have been less than optimal. Before discontinuation of resuscitation one must be absolutely certain that respiratory depression is not due to sedation from maternal narcotics, overventilation from the resuscitation or rarely from an inherited neurological disorder. If this is certain, after discussion with the parents, resuscitation may be discontinued, allowing the parents to be with their infant if they so desire. Where the reason for the depression is uncertain and the response is incomplete, further assessment and management should be undertaken in a neonatal intensive care unit. In these last two situations, telephone consultation with a neonatal specialist is often helpful in deciding whether or not to continue treatment.
Anaesthesia and Intensive Care. Vol. 18. No. 3. August. 1990
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CONCLUSION
The aim of the Melbourne Chart is to provide a framework for all birth attendants to be able quickly to assess the condition of newborn infants, to recognise the asphyxiated infant and the degree of asphyxia, and to provide a logical sequence of measures within their own competence for the care of all infants from the vigorous normal infant to the most severely depressed infant. Such a simple plan minimizes the tendency to panic and to take inappropriate actions, thus leading to the best possible outcomes for these at-risk infants.
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