Neonatal anaesthesia: Difference between revisions

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=== Hypoglycaemia and hyperglycaemia ===
=== Hypoglycaemia and hyperglycaemia ===
Persistent, recurrent or severe hypoglycaemia (blood glucose  
Persistent, recurrent or severe hypoglycaemia (blood glucose  
<2.5mmol.l
<2.5mmol.l-1) may lead to irreversible neurological injury in neonates. Preterm infants and those with intrauterine growth retardation (IUGR) are at particular risk of hypoglycaemia. Fasting times should be minimized, blood glucose should be monitored and glucose containing maintenance fluids should be continued if they have been required prior to surgery. Treat hypoglycaemia with a bolus of 2ml.kg-1 of 10% dextrose. Hyperglycaemia (blood glucose >10mmol.l-1) is also detrimental and is associated with increased mortality and sepsis in extremely low birth weight infants, so do not use boluses of 50% glucose.12  
-1
) may lead to irreversible neurological injury in  
neonates. Preterm infants and those with intrauterine growth  
retardation (IUGR) are at particular risk of hypoglycaemia.  
Fasting times should be minimized, blood glucose should be
monitored and glucose containing maintenance fluids should  
be continued if they have been required prior to surgery.
Treat hypoglycaemia with a bolus of 2ml.kg
-1  
of 10%  
dextrose. Hyperglycaemia (blood glucose >10mmol.l
-1
) is also  
detrimental and is associated with increased mortality and  
sepsis in extremely low birth weight infants, so do not use  
boluses of 50% glucose.
12
perioperative fluids
Assessment of the fluid status of the neonate will help to guide
peri-operative fluid replacement. It is helpful to consider
preoperative maintenance fluids, intraoperative fluids and
postoperative maintenance.
preoperative maintenance fluids
A neonate may require preoperative maintenance fluids if
they are unable to take fluids by mouth before surgery. In
the first few days of life, the sodium requirement is not high,
and typically 10% dextrose is recommended. After the post-
natal diuresis has occurred at around day 3 of life, an isotonic
fluid containing 5% dextrose and sodium should be used, and
electrolytes and plasma glucose monitored (Table 2).


intraoperative fluids
=== Perioperative fluids ===
During surgery, isotonic fluids such as Hartmann’s or Ringer’s
Assessment of the fluid status of the neonate will help to guide peri-operative fluid replacement. It is helpful to consider preoperative maintenance fluids, intraoperative fluids and postoperative maintenance.preoperative.
lactate must be used for resuscitation, replacement and
maintenance to maintain intravascular fluid volume, replace
fluid deficits and avoid hyponatraemia. Blood glucose should
be monitored.
The decision whether to order or administer blood or blood
products will depend on the cardiovascular status of the  
neonate, presence of haemorrhage, type of surgery, the most
recent blood results and the normal expected values (Table
3). Once the decision to transfuse has been taken it may
be worth transfusing to higher haemoglobin levels to avoid
exposure to further donors. Ideally, the haematocrit should
be measured during surgery using near-patient testing device
such as a HemoCue
®
or a blood gas machine. The British
Committee for Standards in Haematology (BCSH) has a
suggested transfusion ‘trigger’ for neonatal top-up transfusion
(Transfusion Guidelines for Neonates and Older Children
(http://www.bcshguidelines.com) (see Table 4). Suggested
transfusion doses for blood and blood products are described
in Table 5.
transitional circulation
In utero, the pulmonary vascular resistance is high and there
is very little blood flow to the lungs as the placenta is the
source of gas exchange. After birth as the neonate takes the
first few breaths, a chain of events is set in place that results
in the transition from the foetal circulation to the neonatal
circulation with closure of the foetal shunts (foramen ovale,
ductus venosus and ductus arteriosus). During the first few
weeks of life the pulmonary vasculature is highly reactive; an
increase in pulmonary vascular resistance can lead to reopening
of the foetal shunts, in particular the arterial duct between the
pulmonary artery and the aorta. As a result there is right-to-
left shunting from the pulmonary artery (deoxygenated blood)
to the aorta, causing profound hypoxia. The oxygen saturation
measured in the right hand may be normal (‘pre-ductal’); the
oxygen saturation in the other limbs (‘post-ductal’) will be low.
During the perioperative period it is important to prevent
factors that increase pulmonary vascular resistance such as
sepsis, hypoxia, acidosis, hypercapnoea, pain and hypothermia.
When post-ductal oxygen saturations drop in relation to
preductal oxygen saturations it may indicate a return to a
foetal circulation.


neurodevelopmental effects of anaesthetics in  
=== Maintenance fluids ===
neonates
A neonate may require preoperative maintenance fluids if they are unable to take fluids by mouth before surgery. In the first few days of life, the sodium requirement is not high, and typically 10% dextrose is recommended. After the post- natal diuresis has occurred at around day 3 of life, an isotonic fluid containing 5% dextrose and sodium should be used, and electrolytes and plasma glucose monitored (Table 2).
Inadequate anaesthesia and analgesia have been shown to  
 
be detrimental to neonates, and associated with increased  
=== Intraoperative fluids ===
mortality. However, many animal model studies have been  
During surgery, isotonic fluids such as Hartmann’s or Ringer’s lactate must be used for resuscitation, replacement and maintenance to maintain intravascular fluid volume, replace fluid deficits and avoid hyponatraemia. Blood glucose should be monitored. The decision whether to order or administer blood or blood products will depend on the cardiovascular status of the neonate, presence of haemorrhage, type of surgery, the most recent blood results and the normal expected values (Table 3). Once the decision to transfuse has been taken it may be worth transfusing to higher haemoglobin levels to avoid exposure to further donors. Ideally, the haematocrit should be measured during surgery using near-patient testing device such as a HemoCue
published recently that have demonstrated accelerated  
® or a blood gas machine. The British Committee for Standards in Haematology (BCSH) has a suggested transfusion ‘trigger’ for neonatal top-up transfusion (Transfusion Guidelines for Neonates and Older Children (http://www.bcshguidelines.com) (see Table 4). Suggested transfusion doses for blood and blood products are described in Table 5.
neuronal cell death (‘apoptosis’) and long-term behavioural  
 
changes after animals are exposed to anaesthetic agents in the  
=== Transitional circulation ===
neonatal period. The situation in humans remains unclear.
In utero, the pulmonary vascular resistance is high and there is very little blood flow to the lungs as the placenta is the source of gas exchange. After birth as the neonate takes the first few breaths, a chain of events is set in place that results in the transition from the foetal circulation to the neonatal circulation with closure of the foetal shunts (foramen ovale, ductus venosus and ductus arteriosus). During the first few weeks of life the pulmonary vasculature is highly reactive; an increase in pulmonary vascular resistance can lead to reopening of the foetal shunts, in particular the arterial duct between the pulmonary artery and the aorta. As a result there is right-to- left shunting from the pulmonary artery (deoxygenated blood) to the aorta, causing profound hypoxia. The oxygen saturation measured in the right hand may be normal (‘pre-ductal’); the oxygen saturation in the other limbs (‘post-ductal’) will be low. During the perioperative period it is important to prevent factors that increase pulmonary vascular resistance such as sepsis, hypoxia, acidosis, hypercapnoea, pain and hypothermia. When post-ductal oxygen saturations drop in relation to preductal oxygen saturations it may indicate a return to a foetal circulation.
13  
 
The risks and benefits of surgery in neonates should be  
=== Neurodevelopmental effects of anaesthetics in neonates ===
considered carefully, and non-essential elective surgery should  
Inadequate anaesthesia and analgesia have been shown to be detrimental to neonates, and associated with increased mortality. However, many animal model studies have been published recently that have demonstrated accelerated neuronal cell death (‘apoptosis’) and long-term behavioural changes after animals are exposed to anaesthetic agents in the neonatal period. The situation in humans remains unclear.13 The risks and benefits of surgery in neonates should be considered carefully, and non-essential elective surgery should be avoided in the neonatal period where possible.
be avoided in the neonatal period where possible.
 
transfer of neonates
=== Transfer of neonates ===
Neonatal surgery should ideally be undertaken in an  
Neonatal surgery should ideally be undertaken in an  
environment where the facilities and expertise are available for  
environment where the facilities and expertise are available for  
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