Page 20 - 59peadiatric-surgery-speciality8-14_opt

Anaesthesia and Perioperative Care 59

may exist, however, in the presence of reduced cardiac output, so the to preserve what little respiratory reserve they have (e.g., children with
ECG should be interpreted in the context of other information obtained cystic fibrosis, severe asthma, or neuromuscular disorders).
from monitors of the patient’s circulation. The two classes of local anaesthetics, esters and amides, exhibit
The patient’s circulation may be monitored by observation of the differences in distribution and metabolism in paediatric patients (especially
peripheral perfusion, peripheral pulse, blood pressure, urine output, neonates) when compared to adults. Awareness of these pharmacokinetic
and arterial oxygen saturation. Observation of the patient’s extremities differences leads to safer use in this vulnerable patient population.
yields information about the state of the patient’s circulation. When the Ester local anaesthetics are metabolised by plasma cholinesterase,
skin is warm and dry all the way to the fingers and toes, one can infer which has lower activity levels in neonates and infants up to the age
that tissue perfusion and therefore cardiac output is adequate. Cool of 6 months. This may theoretically lead to prolonged effects, but in
extremities thus indicate hypovolaemia and reduced cardiac output. practice, the effects of 2-chloroprocaine given for continuous caudal
Palpation of peripheral pulses is another way of obtaining the same anaesthesia have been shown not to be prolonged, even when using
information. As intravascular volume decreases, the pulse volume relatively high infusion rates. In fact, in spite of the low plasma
decreases, especially in the wrists and feet. Adequate production of cholinesterase activity, plasma chloroprocaine levels remained low.
urine implies adequate renal perfusion and probably adequate perfusion Amides are bound by plasma proteins and metabolised by the
of other vital organs. Measurement of urine output is particularly liver. Neonates have reduced plasma protein concentrations as well as
indicated in critically ill or shocked patients or when massive fluid reduced liver blood flow and immature liver enzymes. This all points
shifts are expected. A urine output of 0.75–1 ml/kg per hour is to increased free drug in the plasma and potential toxicity, although the
desirable. Blood pressure provides another indirect means of measuring larger volume of distribution in neonates tends to offset these changes.
circulating blood volume and cardiac output due to the relationship. It is thus important to follow guidelines on maximum recommended
doses when doing regional blocks.
Blood Pressure = Cardiac Output × Peripheral Resistance. Essentially all RA blocks that are useful in the adult population
can be used in the paediatric population, with special attention to
Methods of measuring blood pressure range from palpation and the toxic drug doses and the anatomical landmarks. Many obstacles
auscultation to direct intraarterial manometry. in performing RA in the paediatric population may be related to the
A pulse oximeter measures oxygen saturation continuously and thus availability of the appropriate sizes of needles for the patient, especially
provides another indirect assessment of the function of the circulatory the neonate. Close post-block monitoring needs to be available.
system. Estimation of blood loss is a useful monitor in maintaining the Especially if narcotics are to be used, the nursing staff needs to be
overall integrity of the cardiovascular system. carefully educated regarding the signs of toxicity and side effects of
Apart from monitoring the patient’s colour, respiratory rate, and these drugs in the paediatric population. Table 10.2 gives the maximum
breathing pattern, auscultation of both lungs should be performed frequently. recommended doses for commonly used local anaesthetic agents.
Airway pressure monitors and disconnection alarms are desirable in Commonly performed regional procedures include caudals, epidurals,
ventilated patients. A capnograph, when available, can be used to confirm spinals, ilio-inguinal blocks, and penile blocks.
correct placement of an endotracheal tube and to continuously assess the Table 10.2: Maximum recommended doses of local anaesthetics.
adequacy of ventilation.
It is important to remember that monitors only provide information. Local anaesthetic Maximum dose (mg/kg)
It is the duty of the anaesthetist to interpret this information and then act 2-Chloroprocaine 20
appropriately. The postoperative paediatric patient needs close monitoring
in the recovery room and wards when narcotics are used for surgical pain Lidocaine 7
management. The vigilance of the nursing staff and anaesthesia care Mepivacaine 7
provider will decrease much of the morbidity and mortality associated
with many paediatric, and especially neonatal, surgical patients. Bupivacaine 2.5
Narcotics 3.5
Ropivacaine
Opioids can be titrated for intraoperative and postoperative analgesia, and
to provide a smooth awakening from anaesthesia. All the commonly used
Tetracaine 1.5
opioids are used in paediatric practice and, just as in adults, in high doses
they all carry the risk of respiratory depression. Fear of this respiratory
depression is not a reason to deny children the benefits of opioid pain
relief. Careful titration to effect will often eliminate this complication. Postoperative Care
Following the end of the anaesthetic is a period of physiologic stabili-
Regional Anaesthesia sation that typically takes place in a postanaesthetic care unit (PACU),
Regional anaesthesia (RA) is particularly suited to patients undergoing recovery room, or an intensive care unit (ICU). Emergence and recov-
outpatient procedures and peripheral surgery. It has also been suggested ery describe the transition from the anaesthetic state ultimately to the
that RA may improve pulmonary function in patients who have had patient’s baseline state. During this period, the patient typically awak-
thoracic or upper abdominal surgery. Advantages include the reduced ens from general anaesthesia and regains protective reflexes.
need for deeper planes of general anaesthesia in patients who have had The immediate postoperative period is a period of maximal
a nerve block to supplement their general anaesthesia (GA). RA also hazard that calls for continuous patient monitoring. The commonest
allows a pain-free awakening while minimising or avoiding the use complications are airway obstruction, hypoventilation, and hypoxia.
of opioids altogether. In addition, there is often early ambulation and For children who are intubated, the tube should remain in situ until
excellent postoperative analgesia. they are fully awake. Laryngospasm is common at extubation, especially
The use of RA, however, has certain limitations in paediatric practice. in patients who are neither very deeply anaesthetised nor fully awake.
Except in the older child and adolescent, blocks are rarely performed in The pharynx should be carefully suctioned before extubation. Oxygen
the awake child and usually need to be part of a combined technique. should be administered immediately after extubation, and the patient
Regional anaesthetic techniques are particularly useful in children observed for adequate depth of respiration, oxygen saturation, activity,
at risk for malignant hyperthermia or in those for whom it is necessary and colour. These children should be cared for by trained staff in the