Monitoring and Safety Issues for the Pediatric Patient

The complexity of monitoring applied to pediatric patients must be consistent with the severity of the underlying medical condition and the planned surgical procedure. My philosophy is that if I would place an arterial line or central venous line in an adult undergoing a particular operation, the same should be carried out for a child or infant.

Routine Monitoring and Safety Issues

Minimal monitoring during anesthesia should include a precordial or esophageal stethoscope, a blood pressure cuff, an electrocardiogram, a temperature probe, a pulse oximeter, an end-tidal carbon dioxide monitor, and if possible, an anesthetic concentration analyzer. The noninvasive blood pressure (NIBP) cuff is particularly useful because frequent blood pressure readings can be taken even when the anesthesiologist is preoccupied with other tasks. The end-tidal carbon dioxide monitor, NIBP cuff, and pulse oximeter all provide an early warning of impending disaster that may go unobserved until the appearance of late clinical signs such as cyanosis, bradycardia, severe hypotension, or the absence of breath sounds. Simultaneous loss of the pulse oximeter signal and an inability to measure blood pressure usually indicate low or no cardiac output. If the pulse oximeter continues to function but the NIBP cuff has changed from measuring to nonmeasuring, the likelihood of hypovolemia or anesthetic overdose must be immediately addressed.

The pulse oximeter has a frequent occurrence of false alarms from movement artifact, light interference, and electrocautery. The new generation of pulse oximetry software and new devices should minimize these artifacts, but because they continue to function in very low-flow states and because the software is designed to read through motion, we may no longer be able to use the pulse oximeter as a rapid determinant of perfusion.

Capnography is the gold standard for confirmation of successful endotracheal intubation. However, the capnograph is useful in a number of other ways. Changes in the shape or the magnitude of the CO₂ waveform may indicate bronchospasm, endobronchial intubation, a kinked endotracheal tube, or low pulmonary blood flow. One of the main drawbacks of capnography in small children is the inaccuracy of the recording obtained when using nonrebreathing circuits. The best method of avoiding artifact is to sample the expired gases at some point within the endotracheal tube^{[301] [302]} or to use the circle system even in small infants.^[303] In general, the concentration of carbon dioxide in expired gases is within 2 to 3 mm Hg of that in arterial blood. However, severe pulmonary disease or atelectasis may produce a large difference in these two values. In this type of patient, the gradient between arterial and expired carbon dioxide levels may be used to estimate the severity of shunting. When such shunts exist, measurement of expired carbon dioxide levels may be used only to monitor trends. Ultimately, the most important monitors are the eyes, ears, and hands of the anesthesiologist, who must gather all the information provided by the patient and by the monitors applied to the patient, consolidate the information into an accurate picture, and respond accordingly.

Prospective studies have shown that children younger than 6 months have a more frequent occurrence of critical events.^{[80] [304] [305] [306] [307]} The incidence of critical events was several times higher in American Society of Anesthesiologists (ASA) physical status 3 and 4 patients than in ASA physical status 1 and 2 patients. In some studies, these events occurred with greater frequency and severity when oximetry was not available to the anesthesiologist.^{[304] [305]} A number of factors may account for these results: the high metabolic rate of small children, the technical difficulty of caring for infants, the difficulty of estimating actual delivered ventilation when a variety of circuit configurations are available, and unfamiliarity in taking care of small children. The POCA registry, a voluntary reporting system from 63 hospitals, reported cardiac arrests in children 18 years or younger.^[80] The estimated incidence of cardiac arrest was 1.4 ± 0.45 per 10,000 cases. Of the 289 cases collected over a 4-year period, 150 were thought to be related to anesthesia and 83 occurred in children younger than 12 months (55%). Emergency procedures and ASA status of 3 or higher were predictive of mortality. Of the anesthesia-related cardiac arrests, 55 were believed to be related to medications, and halothane alone or in combination with other drugs was associated with 37 of these events. It should be noted that two were associated with sevoflurane and that at the time of data collection, sevoflurane had not been widely used in the United States. The use of high inspired concentrations of halothane (≥3%) accounted for 14 of the arrests, and other associated factors were controlled ventilation (n = 18) and difficult intravenous access (n = 4). The most common preceding events were bradycardia and hypotension (n = 25). Three infants had unrecognized cardiomyopathy and one had congenital heart disease. Airway-related events accounted for only 20% of cases, and most involved airway obstruction and laryngospasm. Several lessons can be taken from these data: (1) children younger than 1 year are particularly vulnerable to adverse events in the perioperative period; (2) although halothane was commonly associated with cardiac arrest, it appears that high inspired concentrations and controlled ventilation contributed further; (3) high inspired concentrations of inhaled drugs should be avoided until intravenous access is established; (4) it is not the drug but the way the drug is used that is most likely the major contributing factor to these arrests; (5) particular attention should be paid to frequent monitoring of blood pressure and heart rate during induction; (6) in contrast to earlier studies, pulse oximetry and capnography monitoring may have reduced the incidence of airway-related events that were avoidable; and (7) children with congenital heart disease are particularly vulnerable to the cardiac depressant effects of potent inhaled drugs. One study that supports these conclusions was a multi-institutional, highly controlled drug trial that compared remifentanil-based anesthesia with halothane-based

2393

Invasive Monitoring

Arterial and central venous catheters should be used in pediatric patients whenever such monitors contribute to the management of safe anesthesia. The anesthesiologist should not alter the decision to place these monitors simply because the patient is small or because the anesthesiologist is uncomfortable applying the technique to a pediatric patient. A variety of manufactured kits are available, most of which use a thin-walled needle and a guidewire for venous access. If these monitors are indicated, the anesthesiologist, surgeon, cardiologist, or neonatologist should insert them. It is critical to pay special attention to the volume of fluid and heparin infused; special care must be taken to avoid the introduction of air bubbles. Pulmonary artery flow-directed catheters are rarely indicated in pediatric patients because right- and left-sided cardiac pressures are almost identical. However, occasionally, the occurrence of pulmonary artery hypertension or severe multisystem failure may require the use of this monitor.

Multilumen catheters are very valuable in the care of critically ill patients. These devices facilitate the simultaneous intravenous administration of a variety of fluids, vasopressors, and antibiotics. However, these catheters can also lead to a false sense of security created by having three intravenous ports. Specifically, if rapid infusion of colloid or even crystalloid were necessary, the long, narrow lumen would severely limit the rate of infusion and might prevent adequate rapid volume replacement.^{[308] [309]} If the need for rapid volume expansion might possibly arise, a separate large-bore intravenous catheter should be inserted. Short-term cannulation of the femoral or brachiocephalic vein is reasonable and may be lifesaving.