Apnoea
Summary
- apnoea of prematurity is a diagnosis of exclusion <34 weeks for breathing and heart rate </li/>
- apnoea on day 1 may not be due to idiopathic apnea of prematurity -consider sepsis or impending respiratory failure (esp when there is underlying surfactant deficiency)
- all infants <34 weeks should be initially monitored for breathing and heart rate </li/><34 weeks should be initially monitored for breathing and heart rate</li/><34 weeks should be initially monitored for breathing and heart rate
- a sudden increase in severity/frequency of apnoiec episodes suggests new pathology
- treatment of apnoea requires acute resuscitation followed by diagnosis and treatment of specific causes
- symptomatic control with medication or ventilatory support may be required
- apnoea of prematuiry is not a risk factor for SIDS
Introduction
Apnoea is defined as no effective respiratory effort for 20 seconds or shorter if associated with bradycardia<100bpm), cyanosis or pallor. Apnoea may be classified as </p/> (<100bpm), hypotonia, cyanosis or abrupt pallor. Apnoea may be classified as</p/> <100bpm), hypotonia, cyanosis or abrupt pallor. Apnoea may be classified as
- Central apnoea - a pause of alveolar ventilation due to immaturity of neurological controls. There is a complete cessation of both chest movement and airflow. Central apnoea (10-25% of all apnoea) may be provoked by vagal stimulation e.g. oral or nasal suctioning or the passage of a naso-gastric tube.
- Obstructive apnoea - a pause in alveolar ventilation due to obstruction of the upper airway (usually at the level of the pharynx). There may or may not be respiratory effort but there is no airflow - not detected by motion sensing monitors (10 - 25% of all apnoea)
- Mixed apnoea - a combination of central and obstructive apnoea (50 - 75% of all apnoea)
Apnoea is distinguished from periodic breathing (respiratory pauses > 3 seconds duration with less than 20 seconds of respiration between pauses) which may occur normally.
Apnoea occurs in
- most infants < 30wks
- about 50% of infants at 30-32wks
- about 10% of infants at 34wks
Apnoea usually resolves by the time the infant is 36wks postmenstrual age.
There is good evidence that apnoea of prematurity is not a risk factor for SIDS.
There is no evidence that apnoea of prematurity causes subsequent neurodevelopmental morbidity although recurrent apnoea causes concern because of effects of repeated episodes of tissue hypoxia (especially on the gut and brain).
Recognition
Infants at risk of apnoea should have cardiorespiratory monitoring +/- oxygen saturation monitoring. Alarms should be set appropriately with heart rate 100 beats per minute and apnoea delay at 20 seconds. When alarms are triggered, the infant should be assessed for colour, perfusion, position, rspiratory rate and effort, heart rate, oxygen saturation and state.
Differential Diagnosis
Apnoea occurs with increasing frequency the more immature the infant. Various conditions may cause or aggravate apnoea
Anatomical anomalies of the upper airway - choanal atresia, micrognathia, macroglossia, tracheomalacia
Infection - sepsis, necrotizing enterocolitis
Temperature disturbance - hypothermia, hyperthermia
Metabolic - hypercalcemia, hypoglycemia, hyponatremia, hypocalcemia, hypermagnesemia, hyperammonemia, acid/base disturbances
Haematological - anaemia, polycythemia
Pulmonary - impending respiratory failure
CVS - causes of cardiac failure or impaired oxygenation eg PDA,congenital heart defects, arrhythmias
CNS - intraventricular haemorrhage, intracranial haemorrhage, seizures, asphyxia, increased intracranial pressure, cerebral abnormalities
Drugs - prenatal - narcotics, betablockers,magnesium, maternal smoking
postnatal - sedatives, hypnotics, narcotics, prostaglandin(PGE1)
Apnoea on day 1 is not normal. A sudden increase in severity/frequency of episodes suggests new pathology.
The following lists important potential causes of apnoea according to infant age
- presenting symptom of RSV infection
Investigations
A thorough physical examination is mandatory with emphasis on cardiorespiratory and neurological status.
Usually a septic screen and blood glucose estimation will be required.
Further tests are determined by the need to look for specific conditions (see differential diagnosis) causing or aggravating apnoea.
Management
The acute apnoeic episode
- Stimulate e.g. tickle or flick the feet or stroke the abdomen
- Aspirate airway if no response, briefly suction the oropharynx then repeat stimulation
- Position the neck in a neutral position or slightly extended to minimise airway obstruction
- Bag and mask ventilation if still no response, using the amount of oxygen the infant was receiving prior to the apnoea (not 100%). Only increase the concentration of oxygen (by steps of 5-10%) if the infant's condition fails to improve despite effective bag and mask ventilation
- If still no response ongoing positive pressure ventilation is required
Management of specific causes
Treatments will depend on the specific cause of the apnoea.
Symptomatic management
Various methods can be used to provide symptomatic control of apnoea until the infant 'out grows' this problem.
When is symptomatic treatment useful? There is no 'right' answer to this question. The following suggestions fall within the spectrum accepted at most neonatal units.
Episodes needing brief stimulation for cyanosis + bradycardia: >6 every 12hrs
Episodes needing vigorous stimulation +/- oxygen: >1 every 24hrs
Episodes needing PPV +/- oxygen: >1 episode every 24hrs
- Attention should be given to posturing the infant to avoid obstruction of the upper airway
- Feeds may be given more frequently as smaller boluses to avoid excessive distension of the stomach
- Some infants benefit from maintaining their thermal environment in the lower part of the neutral thermal range
- Low flow oxygen into the incubator (approx 23-24%) may help when levels of oxygenation between apnoeas are borderline satisfactory. If used continuous saturation monitoring is needed to avoid risks of hyperoxia (e.g. retinopathy of prematurity in infants < 30 weeks’ gestation)
- Parmacological mangament
Both caffeine and theophylline are effective in short term reduction of symptoms - caffeine has advantages because of its higher therapeutic ratio, once daily dosing, lack of need to assay blood levels and fewer adverse events. Caffeine has been more rigorously evaluated in clinical trials compared with theophylline/aminophylline. Caffeine improves survival without neurodevelopmental disability in VLBW infants at 18-21 months of age.
| Dosages | Theophylline/Aminophylline | Caffeine |
| Loading dose | 6mg/kg | 20mg/kg |
| Mainenance dose |
2.5-4.0mg/kg/dose 12hourly (2.5mg wk1, 3mg wk2,4mg>wk2) |
5mg/kg 24 hrly Increase up to 10mg/kg 24 hourly if no response |
Side effects of theophylline include
- Irritability
- Vomiting
- Abdominal distension/feeding intolerance
- Seizures
- Hyperglycaemia
- Electrolyte imbalances
In general, the side effects of caffeine predominantly involve the central nervous system (e.g. irritability and seizures).
Medication is usually stopped when the infant is >=34wks gestation and apnoea free for 1 to 2 weeks. Monitoring is continued for a further week after medication is stopped. Since elimination of caffeine is affected by postnatal age, it is suggested that for infants receiving caffeine, that they are observed for 7-10 days after cessation of treatment. In the most premature infants (< 28 weeks gestation) apnoea frequently persists beyond 36 weeks post menstrual age and may persist beyond 40 weeks post menstrual age.
-
Positive distending pressure - treats both obstructive and mixed apnoea
Proposed mechanisms of action: - prevents pharyngeal collapse by splinting the nasopharynx, stabilizes the chest wall musculature, alters various reflexes (Hering-Breuer, Intercostal inspiratory inhibitory) and increases functional residual capacity (FRC).
Nasal CPAP may be given by various techniques - most simply via a cut down endotracheal tube inserted 2cm into one nostril. Initial pressure settings for nasal CPAP are 5 -7 cm H2O which may be adjusted according to clinical response.This should only be used in larger units that can safely provide CPAP. Smaller units may utilise this technique following consultation with NETS pending transfer.
Possible side effects - barotrauma, nasal irritation, abdominal distension and feed intolerance.
- Positive pressure ventilation
When uncontrolled by other means intubation and positive pressure ventilation will be required. Initial ventilator settings will use short inspiratory times and minimal PIP pressures to minimise risk of lung injury.
Areas of Uncertainty in Clinical Practice
- Minimising apnoea after extubation from PPV
Both CPAP and theophylline will reduce post-extubation apnoea. - The place of blood transfusion in treatment of apnoeaPresence and severity of apnoea correlate poorly with the presence of anaemia. Theophylline has been shown superior to blood transfusion in improving symptoms of apnoea in anaemic infants (but in a very small study). The clinical benefits from transfusion appear greater the more severe the level of anaemia (the effects are trivial when the haemoglobin is about 100g/L).
- Doxapram as medication for symptomatic control of apnoea
Doxapram cannot be recommended for the treatment of apnoea because of concerns about its safety. - Caffeine and Prematurity (CAP) Trial
The CAP trial, which contained a number of infants managed in - Use of oxygen by nasal cannulae to control apnoea
High oxygen flows given by nasal cannulae may achieve significant positive distending pressures. Possible side effects include inadequate heating and humidification leading to temperature control problems and increased nasal irritation. Pressures generated are not able to be monitored with this system.
References
Effect of blood transfusion on apnoea, bradycardia and hypoxemia in preterm infants C.F.Poets, U.Pauls, B.Bohnhorst Eur J Pediatr (1997)156: 311-316
Transfusion-induced changes in the breathing pattern of healthy preterm anemic infants P.Sasidharan, R.Heimler Ped. Pulmonlogy (1992)12(3):170-3
Relationship between determinants of oxygen delivery and respiratory abnromalities in preterm infants with anemia E.M.Bifano, F.Smith, J.Borer J.Pediatr 120(2Pt1):292-6, 1992 Feb
High-Flow Nasal Cannulae in the Management of Apnea of Prematurity: A comparison with conventional nasal continuous positive airway pressure C.Sreenan, R.P.Lemke, A. Hudson-Mason, H.Osiovich Pediatrics 2001 107(5) 1081-3
A Primer on Apnea of Prematurity
Current Options in the Management of Apnea of Prematurity J Bhatia Clin Paediatr 2000 39 327-36
Apnoea of Prematurity RJ Martin, JM Abu-Shaweesh, TM Baird Paediatr Respir Rev 2004 5 (Suppl A) S377-82
Other Reading/Web links
Cochrane database contains a number of meta-analyses of aspects of management of apnoea. www.neonatology.org
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