Anesthesia for Laparoscopy in the Pediatric Patient

ANESTHESIA FOR MINIMALLY INVASIVE SURGERY LAPAROSCOPY, THORACOSCOPY, HYSTEROSCOPY

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ANESTHESIA FOR LAPAROSCOPY IN THE PEDIATRIC PATIENT John H. Pennant, MA, MB, BS, FRCA

Although laparoscopy has been available since it was first described by Kelling in 1923,3l only in the last decade has it found applications in pediatric surgery. As expertise and equipment have improved, an increasing number of young children now present for laparoscopic intervention. Early pediatric endoscopes, by necessity being smaller than their adult versions, tended to have a reduced viewing angle and produced dim images, but modem optical refinements such as the rod lens telescope, shortened instruments, and video technology allow highquality views. As in adults, laparoscopy permits inspection of the abdominal and pelvic organs, and the retroperitoneal space and the lower portion of the kidneys, without disturbing the anatomic relationships of these structures. Anesthetic management is complicated by the major physiologic effects of the pneumoperitoneum and patient positioning. Modifications in anesthetic technique might be required to allow this novel operation to be performed safely. As more procedures are performed laparoscopically, knowledge of these physiologic changes has become fundamental to safe practice, especially when they are applied to sicker patients. OVERVIEW OF PEDIATRIC LAPAROSCOPIC SURGERY

As in adults, the laparoscopic approach to pediatric surgery has been marketed through claims of reducing hospital costs, allowing ear-

From the Department of Anesthesiology & Pain Management, University of Texas Southwestern Medical School, Dallas, Texas

ANESTHESIOLOGY CLINICS OF NORTH AMERICA

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VOLUME 19 NUMBER 1 MARCH 2001

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lier discharge and a more rapid return to normal diet and full 39, 50 There is a perception it is associated with an improved cosmetic result, reduced postoperative hernias, less wound infections, a lower incidence of postoperative ileus, and less postoperative pain. Fewer laparoscopic operations are performed in children, so one institution does not have extensive experience. There are no published randomized prospective studies of this type of minimally invasive surgery in this young population. Existing reports are mostly anecdotal in nature, so that the precise role of this exciting new technique in pediatric surgery has yet to be defined. More recently, small controlled studies of laparoscopic appendectomy and fundoplication in children have been 47 These have helped to identify the benefits and drawbacks of this surgical technique. Laparoscopy can be a diagnostic procedure in children (e.g., to evaluate the undescended testis,", 46, 48 as part of the evaluation of intersex, in the diagnosis of the acute abdomen,= and in staging pediatric cancer). Once the diagnosis is made, laparoscopic techniques can help to treat the condition (e.g., unwinding adnexal torsion,48appendectomy, adhesiolysis, resection of Meckel's diverticulum, or even removal of a pheochromocytoma9). With the laparoscope, even large, solid intra-abdominal masses such as the kidney or spleen can be removed after the tissue has been morcellated. As experience has increased, a variety of more sophisticated procedures are now possible (e.g., colectomy, "pull-through for Hirschsprung's disease,I7,21, 67 pyeloplasty, and treatments for vesicoureteral reflux, gut malrotation, and choledochal cysts). PHYSIOLOGIC CHANGES DURING LAPAROSCOPY

Although the perioperative management of children undergoing laparoscopy is essentially identical to that for other intra-abdominal procedures, two factors conspire to make anesthesia more challenging, namely the creation of a pneumoperitoneum (with the associated absorption of insufflated carbon dioxide [CO,] and elevation of intra-abdominal pressure), and the extremes of patient positioning that are necessary for optimal exposure of intra-abdominal structures. Creation of the Pneumoperitoneum

The creation of a pneumoperitoneum with insufflated gas permits visualization and manipulation of the abdominal viscera. The volume of insufflating gas necessary for pneumoperitoneum is obviously much lower in children; adults require 2.5 L to 5.0 L, whereas a 10-kg patient needs only about 0.9 L.68 Safety precautions must be taken if one is using the Veress insufflator needle-namely, aspiration, injection, and the hanging-drop tech-

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nique so that the serious consequences of gas embolism can be avoided.24 The risk of injuries to vascular and visceral structures from the Veress needle is higher in infants.= This has led to its replacement by an open approach, which is safer. The ideal gas for insufflation would have the properties listed here: Minimal peritoneal absorption Minimal physiologic effects Rapid excretion of any absorbed gas Inability to support combustion Minimal effects from intravascular embolization High blood solubility Advantages of

CO, for lnsufflation

CO, approaches the ideal insufflating gas, and because other options (e.g., air, oxygen, nitrous oxide) have undesirable qualities, is almost universally used. As laparoscopy frequently involves the use of bipolar diathermy or lasers, the insufflated gas must not support combustion. This effectively excludes air, nitrous oxide (N,O), and oxygen. Residual CO, pneumoperitoneum is cleared more rapidly than that created with other gases, minimizing the duration of postoperative disc0mfort.5~ Disadvantages of

CO, for lnsufflation

The chief drawback of CO, is its significant vascular absorption across the peritoneum. In children, CO, uptake is more efficient owing to the smaller distance between capillaries and peritoneum, and the greater absorptive area of peritoneum in relation to bodyweight. In prolonged procedures (>1 h), hypercapnia can develop. This could mandate increasing minute ventilation by as much as 60% to restore end-tidal CO, (ETcq) to baseline levels. Hypercapnia also can provoke sympathetic nervous system activity, leading to an increase in blood pressure, heart rate, myocardial contractility, and arrhythmias. Hypercapnia also sensitizes the myocardium to catecholamines, particularly when volatile anesthetic agents are used. The additional CO, load can lead to hypercapnia in the postoperative period, because large quantities can be buffered by body tissues. CO, is gradually excreted postoperatively, causing an increased ventilatory requirement when the ability to increase ventilation is impaired by residual anesthetic drugs and diaphragmatic dysfunction. Massive intravascular embolization of any gas results in cardiovascular collapse, and CO, is no exception.8 Detection of embolized gas is difficult unless a precordial Doppler probe or transesophageal echocardiography is in use. The other criteria traditionally used to detect air embolism, such as an increase in end-tidal nitrogen, will not register any change when the embolized gas is CO,, N20, or helium. Following CO,

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embolism, capnography might not reveal any change in ETco, until late in the course of the event. Other Gases for Pneumoperitoneum Studies using helium as the insufflating gas5 show no changes in arterial pH or Pacq, so that, from this point of view, it would appear to be a suitable alternative to CO,. Should intravascular gas embolization occur, however, the relative insolubility of helium compared with CO, could result in more serious cardiovascular sequelae. Helium is also expensive, and its widespread adoption into laparoscopic practice could impact attempts at cost containment in the surgical suite. Nitrous oxide supports combustion and is therefore contraindicated if cautery is used. Pollution of the surgical environment is also a concern with this agent. Gasless Laparoscopy The gasless laparoscopic technique avoids using any gas for insufflation, relying instead on an abdominal wall lift to create an intraabdominal space at atmospheric pressure.34This has further advantages because maintaining a pneumoperitoneum is more difficult in infants because even the smallest gas leak can cause the small working space to collapse. Gasless techniques allow the use of valveless ports and instruments of differing calibers without the inconvenience of a variable pneumoperitoneum, and without the problems attributed to increased intra-abdominal pressure (IAP).

Intra-abdominal Pressure The creation of a pneumoperitoneum necessarily raises IAP,which can have significant cardiovascular, respiratory, and neurologic effects. Cardiovascular Effects The critical determinants of cardiovascular function during laparoscopy are the IAP and patient position.63If the IAP is kept below 15 mm Hg, venous return actually is augmented as blood is "squeezed" out of the splanchnic venous bed, producing an increase in cardiac output. At IAP levels greater than 15 mm Hg, venous return decreases as the inferior vena cava (IVC) is compressed. This results in a reduction in cardiac output and arterial blood pressure. In other types of surgery, in which the N C is cross clamped or ligated, compensatory flow can occur by collateral vessels and restore blood pressure to acceptable levels, but in laparoscopy the high levels of IAP also obstruct these collaterals. In

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this case, the hypotension can be more profound than that following simple IVC occlusion. Early work with newborn piglets confirmed the importance of keeping IAP below 15 mm Hg.35Above this level, a progressive decrease in cardiac index was noticed. For example, at an IAP of 20 mm Hg, the cardiac index fell to 55% of baseline, but when the IAP was increased to 30 mm Hg, the cardiac index decreased to 38% of its resting level. Studies using neonatal lambs demonstrated a 35% reduction in renal, hepatic, and intestinal blood flow at an IAP of 25 mm Hg.38 Sakka et a145used transesophageal echocardiography to study the hemodynamic changes during laparoscopy in eight healthy supine children aged 2 to 6 years. Their results showed that an IAP up to 12 mm Hg had minimal effects on cardiac index, reducing it approximately 13%.At an IAP of 6 mm Hg, no cardiovascular parameters were affected, yet surgical conditions were satisfactory. This lower level of IAP is recommended for patients with serious cardiac disease. Hsing’s= group also confirmed the absence of hemodynamic compromise in the Trendelenburg position in 126 children aged 11 months to 13 years undergoing laparoscopic inguinal exploration, when pneumoperitoneum was limited to 10 mm Hg. Others studied 12 healthy supine boys aged 6 to 30 months using a pneumoperitoneum of 10 mm Hg and discovered a 67% reduction in cardiac performance (aortic blood flow and stroke volume) and a 162% increase in systemic vascular resi~tance.’~ These changes were not associated with any deleterious cardiac events. Tobias et a155 studied 53 children aged 1month to 7 years, and looked at cardiorespiratory measurements during brief ( 4 5 min) diagnostic inguinal laparoscopies, in which IAP was kept below 15 mm Hg. Ventilatory settings were unchanged during the investigation. There were no significant changes in arterial 0, saturation or other cardiovascular parameters. These minimal alterations in vital signs were attributed to the brief surgical times, limiting IAP to 15 mm Hg, and avoiding the Trendelenburg position. The authors caution that more dramatic changes could be seen in longer procedures and when the head-down position is used. These cardiovascular changes are complicated by the patient’s position during surgery. The head-up position favored for upper abdominal procedures (e.g., Nissen fundoplication and cholecystectomy) further reduces venous return and cardiac 0utput.2~This effect is more marked during fundoplication, in which a greater degree of head-up tilt (25-30 degrees) is required than for laparoscopic cholecystectomy (15-20 degrees). In addition, surgical dissection around the esophageal hiatus in a pig model increased mediastinal and pleural pressures, which also can produce a significant reduction in cardiac output and explain the occasional episodes of hypotension and hypoxia seen in this procedure.% Surprisingly, release of the pneumoperitoneum did not restore cardiac output, or central venous, pleural, or mediastinal pressures to baseline levels within an hour, suggesting a prolonged physiologic effect from gastroesophageal junction dissection. Conversely, when the patient is

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positioned head down, as for pelvic laparoscopic examination, venous return is augmented and blood pressure returns to normal or even supranormal values. These cardiovascular changes are similar whether CO, or helium is used for insufflation, suggesting that it is the change in IAP and position, rather than absorption of gas, that is re~ponsible.~ Gannedahl et all6 used transesophageal echocardiography and pulmonary artery catheterization to study cardiovascular changes in eight healthy adults undergoing laparoscopic cholecystectomy. They found that the creation of a 13 mm Hg pneumoperitoneum was a much more significant factor than patient position in explaining the increases seen in left ventricular end-diastolic volume and pulmonary capillary wedge pressure. This study emphasizes the importance of keeping IAP as low as possible to minimize adverse cardiovascular developments. Other cardiovascular phenomena can result simply from insufflating gas into the peritoneum. Children have a high level of resting vagal tone, and occasionally peritoneal stimulation by a blast of insufflated gas or penetration by trocars and laparoscopes can provoke bradycardia or a~ystole.4~ Patients with normal cardiovascular function tolerate these variations in preload and afterload well, but those with cardiovascular disease, anemia, or hypovolemia require meticulous attention to volume loading, positioning, and insufflation pressures. Causes of cardiovascular collapse during laparoscopy in patients without cardiac disease are listed here: Vasovagal reflex response to peritoneal stimulation from trocars or insufflation Myocardial sensitization by halothane Reduced venous return secondary to reverse Trendelenburg position, inferior vena cava compression, or high insufflation pressures Hypovolemia Hypercapnia (particularly in longer procedures) Venous gas embolism Respiratory Effects

Elevated IAP reduces diaphragmatic excursion and shifts the diaphragm cephalad, resulting in early closure of small airways, an increase in peak airway pressure, and a reduction in both thoracic compliance and functional residual capacity (FRC). Upward displacement of the diaphragm leads to preferential ventilation of nondependent parts of the lung. This results in ventilation-perfusion mismatch, which is accentuated during positive pressure ventilation and by the Trendelenburg position. FRC is low in children and quickly falls below closing capacity, producing small airway collapse, atelectasis, intrapulmonary shunting, and hypoxemia. This deterioration in respiratory function is reduced when the patient is in the reverse Trendelenburg position and increased

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when the patient is placed in a steep head-down tilt, when the weight of abdominal viscera causes extra diaphragmatic loading. In Tobias’s study55 of inguinal laparoscopy in 53 children aged 1 month to 7 years, when IAP was limited to 15 mm Hg, peak airway pressures increased by a mean of 3 cm H20 (maximum, 7 cm H20),and ETco, increased from a mean of 32 mm Hg to 35 mm Hg (maximum increase, 11 mm Hg). All values had returned to baseline within 10 minutes of completion of surgery. One study of ten children revealed a 27% reduction in lung compliance and a 32% increase in peak airway pressure following both 20degree head-down tilt and 12 mm Hg pneurn~peritoneum.~~ All values returned to normal when the abdomen was deflated. These changes are about one half as extreme as those seen in adults, perhaps because of the different chest wall configuration and greater thoracic distensibility in children. H s i n g ’ ~study ~ ~ of 126 children reported that whereas there were no significant hemodynamic changes when patients were placed in the Trendelenburg position, as long as IAP was limited to 10 mm Hg, airway pressures and ETco, both increased by approximately 20%. Because most pediatric patients are intubated with uncuffed tracheal tubes and ventilated with pressure-cycled ventilators, this reduction in pulmonary compliance results in a fall in tidal volume (secondary to an increased gas leak around the tracheal tube) unless peak airway pressure and fresh gas flow are raised to keep minute ventilation at adequate levels. Increasing minute ventilation 20% to 30% is usually adequate to maintain normocapnia.60The use of positive end-expiratory pressure (PEEP) can help to alleviate diaphragmatic elevation encroaching on FRC and may improve arterial oxygen saturation. Sfez et a147examined cardiorespiratory function in 25 children aged 1 to 14 years undergoing laparoscopic Nissen fundoplication. All were intubated and ventilated. Several children had preexisting respiratory disease, presumably secondary to chronic aspiration. Hypotension or bradycardia developed in 3 of 4 patients when they were placed in the reverse Trendelenburg position. This responded promptly to volume loading and administration of vagolytic drugs. Subsequently, all patients were operated on in the supine position using LAPS of 6 mm Hg to 10 mm Hg with no significant changes in cardiovascular parameters other than a slight and gradual increase in blood pressure toward the end of the procedure. The authors attributed this elevation in blood pressure to an increased SVR rather than an increase in Paco,. In surgeries that lasted a mean of 116 minutes, only 2 patients required an increased minute volume to correct an elevated ETco,; however, 6 children developed postoperative hypoxemia, defined as an Spoz of less than %YO, within the first 3 postoperative hours. Two patients were receiving supplemental Ozby nasal cannulae. This desaturation is not seen after laparoscopic surgery for inguinal hernia repair, suggesting that it is not the creation of the pneumoperitoneum per se that causes postoperative hypoxemia, but rather interference with diaphragmatic function during fundoplication. The authors suggest that the laparoscopic approach for

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fundoplication confers perioperative stability and postoperative benefits such as reduced ileus, reduced postoperative pain, less respiratory dysfunction, and earlier discharge, compared with open surgery. It is generally believed that the laparoscopic approach is best for older children without neurologic impairment. High IAP levels can permit insufflated gas to gain access to tissue spaces, which explains occasional reports of pneumothorax and pneumomediastinum. This appearance of intrathoracic gas is most often seen following laparoscopic Nissen fundoplication in adults and presumably occurs because dissection of the esophageal hiatus permits passage of insufflated gas across the diaphragm. This complication is increased when a higher IAP is used. A postoperative chest radiograph should be obtained following laparoscopic Nissen fundoplication to detect this development, which can remain clinically silent. Tobias56also studied cardiorespiratory changes in 20 healthy children aged 15 to 80 months undergoing brief (mean, 7 min) diagnostic laparoscopy using a face mask and spontaneous ventilation. Analgesia was provided by caudal epidural block. Slight but significant elevations in tidal volume, ETco,, and respiratory rate were noted in a few patients but were of no clinical significance and had returned to baseline within 10 minutes of completion of the laparoscopy. No significant alterations in heart rate, blood pressure, or arterial 0, saturation were noted. Spontaneous ventilation has the added advantage of lessening ventilationperfusion mismatch because the well-perfused dependent areas of the lung are preferentially ventilated. Avoidance of intubation could have further advantages in patients with airway disease (e.g., asthmatics). Laparoscopy using this technique should be restricted to healthy children having brief procedures in the supine position, where there is no risk of aspiration and insufflation pressures are limited to 15 mm Hg. Neurologic Effects

Another adverse effect of elevated IAP is increased intracranial pressure (ICP). Hypercapnia, increased SVR, and head-down positioning combine to elevate An IAP of 25 mm Hg increased ICP from a mean of 7.6 mm Hg to 21.4 mm Hg and produced a fall in cerebral perfusion pressure from 82 mm Hg to 62 mm Hg. Because of this phenomenon, it is inadvisable to perform laparoscopic surgery on patients with reduced intracranial compliance unless absolutely necessary. Endocrinologic Effects

When laparoscopy was compared with laparotomy for acute abdominal emergencies (e.g., appendectomy, lysis of adhesions) lasting about 1 hour, there was a similar increase in blood levels of "stress" hormones (i.e., insulin, cortisol, prolactin, epinephrine).6 Blood levels of lactate, glucose, and interleukin-6 were also similar in both groups. Despite the minimal degree of tissue damage, the neuroendocrine axis

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appears to be activated to the same extent as in open procedures. The significance of this observation is unclear at present. PERIOPERATIVE MANAGEMENT Preoperative Evaluation

The child presenting for laparoscopy should be managed in exactly the same way as any child presenting for surgery. A thorough preoperative history should be taken, and a complete physical examination should be performed to identify underlying medical conditions that could influence perioperative care. Laparoscopy can be performed as a brief elective procedure on a healthy outpatient, or as an emergency diagnostic procedure in a critically ill patient, so the degree of preoperative evaluation must be tailored to the severity of preexisting disease and the urgency of the procedure. Preoperative Investigations

Healthy children presenting for laparoscopy do not require any preoperative blood tests, a chest radiograph, or an electrocardiogram unless there is preexisting disease that merits evaluation. Although a preoperative hemoglobin value is usually not necessary, major hemorrhage can occur as a complication of the technique and mandate emergency laparotomy, so this type of surgery should be performed only where there is immediate access to a blood bank. Prernedication

The premedication of children is an integral part of pediatric anesthetic practice. It is a matter of personal or institutional preference, although underlying preexisting disease can mandate adjusting premedicants to a more appropriate selection of drugs. Healthy outpatients can be administered oral midazolam, 0.5 to 0.75 mg/kg 15 to 30 minutes preoperati~e1y.l~This can be dissolved in acetaminophen or ibuprofen elixir, 10 mg/kg. Other premedication options include using alternative routes of administration (e.g., nasal,3O intramuscular, transmucosal), or other choices of drugs (e.g., antacids, H, antagonists, gastrokinetic agents [e.g., metoclopramide], opioids, antisialogogues, or ketamineZ0). Some institutions omit premedication entirely, relying instead on parental presence at induction to allay the child's apprehensiveness,28 although recent work, suggests parental presence has no additive anxiolytic effect in addition to oral m i d a z ~ l a m Children .~~ younger than 9 months do not suffer separation anxiety and require either no premedi-

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cation or an anticholinergic (e.g., atropine, 20 kg/kg intramuscularly or 30 to 40 kg/kg orally 30 to 45 minutes preoperatively). The use of atropine is associated with a lower incidence of cardiovascular and airway complications peri~peratively.~~ One further advantage of anticholinergic premedication is to prevent vasovagal reflexes that are occasionally seen when the peritoneum is penetrated. Induction of Anesthesia

Anesthetic techniques available for laparoscopy include local, regional, and general anesthesia. Although local and regional approaches have been described for brief laparoscopic inspections in healthy adults, they are generally unsuitable for pediatric patients and are not discussed further here. Options available for induction of general anesthesia in children include inhalational (using sevoflurane or halothane in nitrous oxide and 0,) or intravenous. The intravenous route is recommended if intravenous access has been secured, which can be performed with minimal discomfort following the use of topical local anesthetic agents, for example, Eutectic Mixture of Local Anesthetics (EMLA) cream, amethocaine gel, or by an iontophoretic technique. Children requiring emergency exploration of the abdomen should receive a rapid-sequence intravenous induction with the use of cricoid pressure until a tracheal tube is securely in place to reduce the risk of pulmonary aspiration of gastric contents. Although tracheal intubation is not mandatory for brief laparoscopic procedures in healthy patients (a f a c e m a ~ kor~LMA5s ~ can be used), good muscle relaxation and intubation provide optimal surgical conditions and a more secure airway and allow controlled ventilation in the face of elevated IAP when a pneumoperitoneum is created. Peripheral intravenous access should be obtained in all patients to allow continued hydration and drug administration, especially in case of accidental vascular injury from endoscopic instruments. Because laparoscopic nephrectomy or splenectomy can result in major hemorrhage, intravenous access must be adequate to permit rapid fluid resuscitation. A venous catheter is preferably inserted above the diaphragm in case the elevated IAP compresses the IVC and impairs access of drugs and fluid to the circulation from venous access sites in the legs.61 A central venous catheter is necessary only if peripheral access is unobtainable or if preexisting medical conditions dictate. Once venous access is obtained, some authors routinely administer a 20-mL/kg fluid bolus to offset the hemodynamic effects when the pneumoperitoneum is created.68 Monitoring

Monitoring the child’s clinical status should follow the American Society of Anesthesiologists’ (ASA) recommendations. These include

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continuous electrocardiography, automated noninvasive blood pressure, pulse oximetry, temperature, and capnography. In some instances, ETco, values do not accurately reflect Paco2, especially when higher IAPs are in use.33Exhaled tidal volume should be measured in case the decrease in pulmonary compliance that follows insufflation leads to underventilation secondary to increased leak around the tracheal tube.61A peripheral nerve stimulator should be used to monitor the degree of neuromuscular blockade and to assess the adequacy of reversal of paralysis at the completion of surgery. Small children have a high body surface area-to-mass ratio and little subcutaneous fat or body hair to retain heat. This, plus surgical exposure of the entire abdomen, tends to provoke rapid heat loss. Continuous insufflation of large volumes of cold, nonhumidified CO, directly into the abdominal cavity also contributes to a major risk of hypothermia. For all but the shortest procedures, core temperature should be measured in the distal one third of the esophagus. An infrared radiant heater, a warming mattress, a heated humidifier for inspired anesthetic gases, and a convective forced air warmer should be used if available. Use of a precordial or esophageal stethoscope allows continuous auscultation of breath and heart sounds and is especially helpful should endobronchial intubation occur. This is a well-recognized complication when the diaphragm and mediastinum are moved cephalad by the pneumoperitoneum, particularly in the Trendelenburg po~ition.'~ Multiorifice central venous catheters are the most effective devices for aspiration of embolized gas, but their routine use is not necessary during laparoscopy because the risk of this complication is so low.62 An oro- or nasogastric tube should be inserted after induction to permit deflation of the stomach. This not only improves visualization of abdominal contents but also reduces the risk of the Veress needle's accidentally perforating the inflated viscus. If continuous cardiovascular monitoring is required, use of transesophageal echocardiography is a satisfactory technique, particularly when extremes of tilt are used. Repositioning of the esophageal probe may be necessary to maintain optimal signal quality throughout all phases of the procedure.12 PerioperativeCare

A balanced anesthetic technique with controlled ventilation using inhalational agents (e.g., sevoflurane, isoflurane, or desflurane), intravenous opioids, nondepolarizing neuromuscular blocking agents (e.g., vecuronium, rocuronium, cis-atracurium, mivacurium, or rapacuronium) is generally preferred.63A total intravenous technique is also an option,13 particularly if there are concern over myocardial depression by volatile anesthetics.26,47 Some anesthesiologists avoid nitrous oxide because of the small risk of venous gas embolism and because its diffusion into the intestinal lumen could distend the bowel and impair the surgeon's visual

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field. Nitrous oxide also can increase the incidence of postoperative nausea and vomiting (POW). Although halothane can be used for inhalational induction, it should be discontinued once the trachea is intubated because hypercapnia secondary to the pneumoperitoneum will sensitize the myocardium to this agent. There are also concerns regarding the reduced hepatic blood flow secondary to the pneumoperitoneum,38which could predispose to halothane hepatotoxicity. The chief difference in anesthetic management between laparoscopy and other abdominal procedures in children relates to the cardiorespiratory changes resulting from pneumoperitoneum and positioning. Ventilation should be controlled, because this facilitates removal of exogenous CO, and minimizes the reduction in FRC caused by a combination of increased IAP, the Trendelenburg position, and the use of volatile anesthetic agents. Minute ventilation might need to be increased by 20% or more to maintain normocapnia. Occasionally, fluid is instilled laparoscopically to improve surgical exposure. This fluid should be isotonic (e.g., lactated Ringer’s solution or Plasmalyte), and allowance must be made for systemic absorption when calculating fluid maintenance regimes. At the completion of surgery, the peritoneum should be deflated completely. Otherwise, any remaining intra-abdominal CO, is absorbed into the circulation during the postoperative phase. Furthermore, any trapped gas will irritate the undersurface of the diaphragm, which presents as referred pain in the shoulder and increases the incidence of POW. Volatile anesthetic agents then should be discontinued, neuromuscular blockade reversed, and the trachea extubated when the patient satisfies accepted criteria. Use of the Laryngeal Mask Airway

The laryngeal mask airway (LMA) has proved a remarkably useful adjunct to anesthesia for patients having minor procedures. It has been used extensively in pediatric practice, although there are concerns about aspiration, gastric distention, and hypercapnia when spontaneous respiration is permitted. It might be expected that laparoscopy would increase the risk of regurgitation and aspiration because of the use of the Trendelenburg position, increased IAP,the surgeon’s pressing on the abdominal wall, and peritoneal stimulation. Furthermore, inflation of the LMA cuff in the hypopharynx has been shown to lower the lower esophageal sphincter pressure by way of a reflex action, predisposing the patient to A few studies have addressed this issue in small groups reg~rgitation.~~ of patients having brief laparoscopic operations. Pelvic laparoscopy has been performed safely in women using the LMA with spontaneous respiration.18,53 No cardiorespiratory complications were noted by the authors, who recommend that procedures be

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kept as brief (<30 min) and LAP kept as low as possible. Although the LMA does not reliably protect the airway and concerns remain regarding aspiration of gastric contents, it appears that the lower esophageal sphincter pressure is increased by the presence of a pneumoperitoneum. Although the incidence of aspiration with the LMA is very low when it is used as recommended, there has not been any reported increase in this complication when it has been used for laparoscopy, even when positive-pressure ventilation was used.3,66 Only one report exists on the use of the LMA in pediatric patients having laparoscopic inspection of the pelvic Fifteen patients breathed spontaneously during these brief operations, which only lasted 3 to 9 minutes. In 4 of these 15 children, ETco, exceeded 60 mm Hg but returned to baseline within a few minutes of the end of surgery. The ETco, increased to a lesser degree in the remaining patients. There were no significant changes in arterial oxygen saturation in any child. Although these preliminary studies suggest the LMA can be safely used in pediatric laparoscopy, it is not recommended for use in longer procedures, or in patients with limited cardiorespiratory It appears to be a safe technique in healthy patients having brief procedures, in whom extremes of head-down tilt and IAP are avoided, and in whom there are genuine concerns about instrumenting the airway (e.g., history of severe asthma). As in all areas of pediatric anesthesia, there is less margin for error than in adults, and slight displacement of the device could lead to underventilation or gastric distention. The anesthesiologist must be vigilant for this complication by regularly auscultating over the stomach to detect gas insufflation. Anesthetic recommendations for laparoscopy in children with severe myocardial disease follow from Tobias and Holcomb’s report on two sick patients undergoing cholecystectomy.60* 61 These include the following: 1. Avoid anesthetic agents that directly depress or sensitize the myocardium, such as halothane. Sevoflurane is a safer alternative. If intravenous induction is considered, etomidate is a better choice than propofol or barbiturates. 2. Preoperative atropine prevents the bradycardia that is occasionally seen as a vagal response to peritoneal insufflation. Patients with noncompliant ventricles have a fixed stroke volume and rely on heart rate to maintain cardiac output, so bradycardia is poorly tolerated. 3. Avoid muscle relaxants and opioids that release histamine (e.g., mivacurium, rapacuronium, morphine). 4. Avoid caudal epidural block for postoperative analgesia because the reduction in preload can lead to a fall in cardiac output. 5. Use local anesthetic infiltration at trocar sites to minimize s p pathetic stimulation. 6. Nonsteroidal anti-inflammatory drugs (NSAIDs) should be used for postoperative analgesia. 7.Consider using transesophageal echocardiography in preference

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to central venous pressure monitoring, because it more accurately demonstrates preload and myocardial contractility. 8. Consider pulmonary artery catheters for children weighing > 15 kg. 9. Insufflate the abdomen slowly, and keep IAP as low as is compatible with good visualization of abdominal contents. Do not permit IAP to exceed 15 mm Hg. 10. Consider replacing gas insufflation with an abdominal wall lift (gasless laparoscopy),34which eliminates problems related to IAP and CO,. 11. Use an arterial catheter to allow blood gas monitoring of Paco,, rather than relying on ETco, values, which might not accurately reflect the true arterial level. 12. Perform surgery in the supine position if possible to minimize changes in venous return and SVR. 13. Quickly convert to an open procedure if severe cardiovascular compromise occurs. Immediate Postoperative Care

Monitoring of vital signs should continue in the postanesthesia care unit (PACU), because an excess of CO, must be cleared from the body. Patients with respiratory disease can have problems excreting this CO, load, resulting in hypercapnia and respiratory failure. A postoperative chest radiograph should be obtained following laparoscopic fundoplication or other upper abdominal laparoscopy to detect pockets of gas that have traversed the diaphragm and produced a pneumothorax or pne~momediastinum.4~ POSTOPERATIVE PAIN MANAGEMENT

Pain following laparoscopy results from a variety of maneuvers, including rapid distention of the peritoneum when the pneumoperitoneum is created. Its severity is related to the degree of distention, and the volume of residual gas after desufflation. Excitation of the phrenic nerve by instrumentation or CO,, and the unusual positions required for some procedures, can stretch nerves and present as postoperative pain. As much gas as possible must be removed from the abdomen at the completion of surgery. Pain can present anywhere in the abdomen but is sometimes reported in the back and in 35% to 63% of adult patients is referred to the shoulders., Shoulder pain is less common in pediatric patients. Postoperative pain is usually mild and transient, requiring little more than NSAIDs for 24 hours. In Sfez’s study of 25 children undergoing laparoscopic Nissen f~ndoplication,4~ no analgesics were needed after the first postoperative day, and even acute postoperative pain was satis-

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factorily controlled by nonopioid analgesics. Occasionally, pain persists for more than 3 days, by which time the patient is probably home and trying to return to normal activity. Pain is best controlled using a multimodal approach of local anesthetics, NSAIDs (e.g., ketorolac, 0.5 mg/kg IV),and opioids. Local anesthetic can be injected at all trocar and endoscope puncture sites or instilled into the peritoneum. The application of topical bupivacaine to the gallbladder bed and subphrenic area after laparoscopic cholecystectomy in adults remains controversial and might not reduce postoperative pain"; it is possible that the number of hypoxic events could increase in the postoperative period, presumably secondary to partial phrenic nerve block. There is evidence that intraperitoneal local anesthetic, especially if given preemptively, reduces postoperative pain from laparoscopic cholecystectomy, however.4°There are no data on this aspect of postoperative pain in children, and further studies are warranted in this population. NSAIDs reduce pain, reduce opioid requirement, and appear to be an excellent choice for control of "late" postoperative pain. They may be given by oral, rectal, intramuscular, or intravenous routes. Oral ibuprofen has been shown to be better at controlling postoperative pain than perioperative fentan~1.4~ Bilateral rectus sheath block gives good pain relief after lower abdominal laparo~copy.~~ Spinal, epidural, and caudal epidural57blocks are also effective. Tobias59compared caudal epidural block with local infiltration and iliohypogastric/ilioinguinalblock in children undergoing laparoscopic inguinal herniorrhaphy. Those receiving caudal blocks were more comfortable; some did not require any further postoperative analgesia. Caudal blocks are best reserved for lower abdominal procedures or when all puncture sites are at or below the umbilicus. It would appear that there are no benefits from a postoperative pain viewpoint when laparoscopy is advocated for a procedure that is normally performed through a minimal incision (e.g., pyloromyotomy or appendectomy). L e j ~ compared s~~ laparoscopic and open appendectomy in 63 children and found a 35% incidence of postoperative shoulder pain in the laparoscopic group versus 10% in the open group. There were no obvious advantages to recommend the laparoscopic approach, which also took longer to perform. In larger children, in whom the incision for open appendectomy tends to be larger and therefore is more likely to produce muscle damage, there can be advantages to the laparoscopic approach. POSTOPERATIVE NAUSEA AND VOMITING

P O W is a common complication following laparoscopy, delaying discharge from the PACU. The incidence can be reduced significantly by prophylactically administering a variety of antiemetic agents.10 f i e author's practice is to use combinations of drugs including a 5-HT3antagonist (e.g., ondansetron, 100 &kg, to a maximal dose of 4 mg,

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dexamethasone, 150 kg/kg, and droperidol, 25 pg/kg, to a maximal dose of 0.625 mg). Other important maneuvers include complete aspiration of the pneumoperitoneum at the conclusion of the procedure.

CLINICAL EXPERIENCE IN PEDIATRIC LAPAROSCOPY

Alain et all described laparoscopic pyloromyotomy for idiopathic hypertrophic pyloric stenosis in ten infants weighing 2.6 to 5.4 kg. They recommend continuous monitoring of inspired and expired C02, and keeping IAP below 8 cm H20. All procedures were unevenful, with operating times shorter than 30 minutes. It is important not to use access points in the periumbilical area in this age group because the umbilical vessels have not involuted and are at risk of puncture. Many pediatric surgeons believe a laparoscopic approach that requires at least three puncture sites in the abdominal wall has little or no advantage over the traditional 10-minute procedure, which is safe, has few complications, and requires only a 3-cm to 4-cm incision that can easily be infiltrated with local anesthetic. To date, studies comparing these two operations for pyloric stenosis have failed to show any dramatic advantages of laparoscopy. One surgical investigation compared laparoscopic versus open appendectomy in a cohort of 63 children3*The laparoscopic approach did not confer any improvement in postoperative pain or recovery but increased hospital costs because the procedure took longer to perform. Many surgeons believe that laparoscopic appendectomy offers little advantage to the child, except when the patient is young, muscular, athletic, or obese. A large retrospective analysis of 1379 laparoscopic appendectomies in children aged 2 to 16 years found that this technique allowed rapid localization of the appendix and the ability to explore and lavage the entire peritoneal cavity,I3 resulting in a lower incidence of postoperative abscesses and adhesions. Hospital stay was shorter, and there was a quicker return to normal activities than with traditional surgery. Varlet65retrospectively compared open and laparoscopic appendectomy in 403 children. Patients who underwent laparoscopy had a 1.5% incidence of complications, whereas the open group had a 10.8% complication rate. Complications included wound abscesses, infections, and bowel obstructions. These two studies suggest that laparoscopic appendectomy can offer significant advantages. Until recently, inguinal hernia repair was routinely performed bilaterally even when a hernia was clinically apparent on only one side, because physical examination often failed to demonstrate contralateral disease. The laparoscope allows inspection of the contralateral side23 to see if bilateral surgery is truly warranted. Children undergoing unilateral inguinal hemiorrhaphy with peritoneal inspection of the contralateral side were more comfortable, required less postoperative analgesia, and were discharged sooner than those having bilateral herni~mhaphy.~~

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COMPLICATIONS

The cardiorespiratory and neurologic problems resulting from hypercapnia and reduced venous return secondary to pneumoperitoneum and extremes of positioning were discussed previously. Elevation of the diaphragm can produce atelectasis and shunting. This cephalad diaphragmatic movement also moves the carina in the same direction and can lead to endobronchial intubation because the tracheal tube is fixed proximally to the lip. In addition, peritoneal stimulation from endoscopic instruments can provoke vagal reflexes and cause bradycardia. Surgical trauma to blood vessels or viscera can result in major hemorrhage, necessitating urgent laparotomy. Insufflated gas can track subcutaneously, or produce a pneumothorax or pneumomediastinum, particularly following fundoplication or surgery for esophageal achalasia. Insufflation of large volumes of cold gas in prolonged procedures has caused hypothermia in small children. Intravascular placement of the Veress needle can result in massive venous gas embolism. Chen et a17 reviewed the records of 574 children who underwent a laparoscopic procedure over a 5-year period and reported a complication rate of 2%. These included hemorrhage (four cases), esophagotomy during fundoplication (one case), hernia at trocar site (two cases), and cellulitis (three patients). Trocar site hernias are more common in pediatric patients because of the thinner abdominal wall. The authors noted a reduction in complication rate as experience increased. FETAL ENDOSCOPY

The technique of fetal endoscopy has been applied in the diagnosis and treatment of fetal disease.*l Fetal endoscopy differs from laparoscopy in that no gas is insufflated to aid visualization and manipulation of fetal tissues. It is possible to view the fetal trachea, esophagus, and bladder. One major advantage is the ability to perform fetal surgery without a hysterotomy and thus avoid risking premature labor. Tracheal plugging to encourage lung development in congenital diaphragmatic hernia can be performed in some centers using video fetoscopic technology. In the future, this development inevitably will find more indications. SUMMARY

Pediatric laparoscopy is a novelty that has yet to be critically assessed in large, randomized controlled trials. Just because an operation can be performed laparoscopically does not mean it must be done that wayu Many procedures can now be performed more quickly and cheaply36through small incisions without the added cardiorespiratory risks seen in laparoscopy. Reports of serious complications are beginning to appear in publicatiom.@It will become important to compare laparo-

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scopic techniques with both open surgery and the minimally invasive approach for the same procedure. Many published studies suggest laparoscopy offers significant advantages for some operations and for sicker patients. Practitioners must have a thorough understanding of the physiologic changes that follow pneumoperitoneum and extremes of positioning. As enthusiasm builds, it is essential to maintain safety standards. Endoscopists must be appropriately trained and peer reviewed. The use of virtual reality models now allows surgeons to develop and perfect their laparoscopic skills. When the laparoscopic approach is difficult, surgeons must be willing to convert to open surgery rather than persevere and risk iatrogenic damage. The role of pediatric laparoscopy has yet to be defined, although current trends suggest that it will assume an important position in pediatric surgery. References 1. Alain JL, Grousseau D, Terrier G: Extramucosal pylorotomy by laparoscopy. J Pediatr Surg 26:1191, 1991 2. Alexander JI: Pain after laparoscopy. Br J Anaesth 79:369, 1997 3. Bapat PP, Verghese C: Laryngeal mask airway and the incidence of regurgitation during gynecological laparoscopies. Anesth Analg 85:139, 1997 4. Bloomfield GL, Ridings PC, Blocher CR, et al: Effects of increased intra-abdominal pressure upon intracranial and cerebral perfusion pressure before and after volume expansion. J Trauma 40:936, 1996 5. Bongard FS, Pianim NA, Leighton TA, et al: Helium insufflation for laparoscopic operations. Surg Gynecol Obstet 177140, 1993 6. Bozkurt P, Kaya G, Altintas Y, et al: Systemic stress response during operations for acute abdominal pain performed via laparoscopy or laparotomy in children. Anaesthesia 55:5, 2000 7. Chen MK, Schropp KP, Lobe TE: Complications of minimal-access surgery in children. J Pediatr Surg 31:1161, 1996 8. Clark CC, Weeks DB, Gusdon JP:Venous carbon dioxide embolism during laparoscopy. Anesth Analg 56650, 1977 9. Clements RH, Goldstein RE, Holcomb GW I11 Laparoscopic left adrenalectomy for pheohomocytoma in a child. J Pediatr Surg 341408,1999 10. Conte ATH Antiemetic therapy for the pediatric ambulatory surgery patient. Am J Anesthesiol23:130, 1996 11. Cortesi N, Ferrari P, Zambarda E, et a1 Diagnosis of bilateral abdominal cryptorchidism by laparoscopy. Endoscopy 8:33, 1976 12. Dickson RE, Robertson EA, Krukowski ZH: Haemodynamic changes during laparoscopic anterior fundoplication measured by trans-oesophageal Doppler ultrasound. Anaesthesia 55260, 2000 13. El Ghoneimi A, Valla JS, Limonne B, et al: Laparoscopic appendectomy in children: Report of 1,379 cases. J Pediatr Surg 29:786, 1994 14. Everett LL, Spottswood SE: Intraoperative desaturation and unilateral breath sounds during Nissen fundoplication. Anesth Analg 9062, 2000 15. Feld LH, Negus JB, White PF Oral midazolam preanesthetic medication in pediatric outpatients. Anesthesiology 73:831,6990 16. Gannedahl P, Odeberg S, Brodin L-A, et a1 Effects of posture and pneumoperitoneum during anaesthesia on the indices of left ventricular filling. Acta Anaesthesiol Scand 40:160, 1996 17. Georgeson KE Minimally invasive pediatric surgery: Current status. Semin Pediatr Surg 7193,1998

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18. Goodwin APL, Rowe WL, Ogg Tw: Day-case laparoscopy: A comparison of two anaesthetic techniques using the laryngeal mask during spontaneous breathing. Anaesthesia 47892, 1992 19. Gueugniaud P-Y, Abisseror M, Moussa M, et a 1 The hemodynamic effects of pneumoperitoneum during laparoscopic surgery in healthy infants: Assessment by continuous esophageal aortic blood flow echo-Doppler. Anesth Analg 86290,1998 20. Gutstein HB, Johnson KL, Heard MB, et a1 Oral ketamine preanesthetic medication in children. Anesthesiology 7628, 1992 21. Harrison MR What's new in pediatric surgery? J Am Coll Surg 182145, 1996 22. Hasegawa T, Miki Y, Yoshioka Y, et a1 Laparoscopic diagnosis of blunt abdominal trauma in children. Pediatr Surg Int 12132, 1997 23. Holcomb GW 111, Morgan WM, Brock JWIII Laparoscopic evaluation for contralateral patent processus vaginalis, Part 11. J Pediatr Surg 31:1170, 1996 24. Holcomb GW 111, Olsen DO, Sharp KW Laparoscopic cholecystectomy in the pediatric patient. J Pediatr Surg 261186, 1991 25. Hsing C-H, Hseu SS, Tsai SK, et a1 The physiological effect of C 0 2 pneumoperitoneum in pediatric laparoscopy. Acta Anaesthesiol Sin 33:1, 1995 26. Ivani G, Vaira M, Mattioli G, et a1 Paediatric laparoscopic surgery: Anaesthetic management. Paediatr Anaesth 4323, 1994 27. Joris JL, Noirot DP, Legrand MJ, et a1 Hemodynamic changes during laparoscopic cholecystectomy. Anesth Analg 76:1067, 1993 28. Kain ZN, Ferns CA, Mayes LC, et al: Parental presence during induction of anaesthesia: Practice differences between the United States and Great Britain. Paediatr Anaesth 6187,1996 29. Kain ZN, Mayes LC, Wang S-M, et al: Parental presence and a sedative premedicant for children undergoing surgery. Anesthesiology 92:939, 2000 30. Karl HW, Keifer AT, Rosenberger JL, et al: Comparison of the safety and efficacy of intranasal midazolam or sufentanil for preinduction of anesthesia in pediatric patients. Anesthesiology 76209, 1992 31. Kelling G: Zur coelioskopie. Arch Klin Chir 126:226,1923 32. Lejus C, Delile L, Plattner V, et a 1 Randomized, single-blinded trial of laparoscopic versus open appendectomy in children. Anesthesiology 84801, 1996 33. Lister DR, Rudston-Brown 8, Warriner B, et al: Carbon dioxide absorption is not linearly related to intraperitoneal carbon dioxide insufflation pressure in pigs. Anesthesiology 80:129, 1994 34. Luks FI, Peers KHE, Deprest JA, et al: Gasless laparoscopy in infants: The rabbit model. J Pediatr Surg 301206, 1995 35. Lynch FP, Ochi T, Scully JM, et al: Cardiovascular effects of increased intra-abdominal pressure in newborn piglets. J Pediatr Surg 9:621, 1974 36. MacIntyre IMC, Miles WFA: Critical appraisal and current position of laparoscopic hernia repair. J R Coll Surg Edinb 40:331, 1995 37. Manner T, Aantaa R, Alanen M Lung compliance during laparoscopic surgery in paediatric patients. Paediatr Anaesth 8:25,1998 38. Masey SA, Koehler RC, Buck JR, et al: Effect of abdominal distention on central and regional hemodynamics in neonatal lambs. Pediatr Res 19:1244,1985 39. Newman KD, Marmon LM, Attorri R, et al: Laparoscopic cholecystectomy in pediatric patients. J Pediatr Surg 26:1184, 1991 40. Pasqualucci A, De Angelis V, Contardo R, et al: Preemptive analgesia: Intraperitoneal local anesthetic in laparoscopic cholecystectomy. Anesthesiology 85:11, 1996 41. Rabey PG, Murphy PJ, Langton JA, et al: Effect of the laryngeal mask airway on lower oesophageal sphincter pressure in patients during general anaesthesia. Br J Anaesth 69:346, 1992 42. Raetzell M, Maier C, Schroder D, et al: Intraperitoneal application of bupivacaine during laparoscopic cholecystectomy-risk or benefit? Anesth Analg 81:967, 1995 43. Rosenblum M, Weller RS,Conard PL, et a 1 Ibuprofen provides longer-lasting analgesia than fentanyl after laparoscopic surgery. Anesth Analg 73255, 1991 44. Sackier JM: Laparoscopy in pediatric surgery. J Pediatr Surg 261145, 1991 45. Sakka SG, Huettemann E, Petrat G, et al: Transoesophageal echocardiographic assessment of haemodynamic changes during laparoscopic hemiorrhaphy in small children. Br J Anaesth 84:330,2000

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46. Scott JES Laparoscopy as an aid in the diagnosis and management of the impalpable testis. J Pediatr Surg 1714, 1982 47. Sfez M, Guerard A, Desruelle P: Cardiorespiratory changes during laparoscopic fundoplication in children. Paediatr Anaesth 5:89, 1995 48. Shalev E, Mann S, Romano S, et al: Laparoscopic detorsion of adnexa in childhood: A case report. J Pediatr Surg 263193, 1991 49. Shaw CA, Kelleher AA, Gill CP, et al: Comparison of the incidence of complications at induction and emergence in infants receiving oral atropine vs no premedication. Br J Anaesth 84:174, 2000 50. Sigman HH, Laberge J-M, Croitoru D, et al: Laparoscopiccholecystectomy: A treatment option for gallbladder disease in children. J Pediatr Surg 26:1181, 1991 51. Smith BE, Suchak M, Siggins D, et al: Rectus sheath block for diagnostic laparoscopy. Anaesthesia 43:947, 1988 52. Spear RM, Yaster M, Berkowitz ID, et a1 Preinduction of anesthesia in children with rectally administered midazolam. Anesthesiology 74:670, 1991 53. Swam DG, Spens H, Edwards SA, et a1 Anaesthesia for gynaecological laparoscopy-a comparison between the laryngeal mask airway and tracheal intubation. Anaesthesia 48:431, 1993 54. Talamini MA, Mendoza-Sagaon M, Gitzelmann CA, et al: Increased mediastinal pressure and decreased cardiac output during laparoscopic Nissen fundoplication.Surgery 122:345, 1997 55. Tobias JD, Holcomb GW 111, Brock JW 111, et al: Cardiorespiratory changes in children during laparoscopy. J Pediatr Surg 30:33,1995 56. Tobias JD, Holcomb GW 111, Brock JW,et al: General anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. J Laparoendosc Surg 4:379,1994 57. Tobias JD, Holcomb GW In, Lowe S, et al: Caudal epidural block for analgesia following hemiorrhaphy with laparoscopy in children. J Laparoendosc Surg 4:117,1994 58. Tobias JD, Holcomb GW 111, Rasmussen E, et al: General anesthesia using the laryngeal mask airway during brief, laparoscopic inspection of the peritoneum in children. J Laparoendosc Surg 6:175, 1996 59. Tobias JD, Holcomb GW, Brock JW, et a1 Analgesia after inguinal hemiorrhaphy with laparoscopic inspection of the peritoneum in children: Caudal block versus ilioinguinal/iliohypogastricblock. Am J Anesthesiol22:193, 1995 60. Tobias JD, Holcomb GW Anesthetic management for laparoscopic cholecystectomy in children with decreased myocardial function: Two case reports. J Pediatr Surg 32:743, 1997 61. Tobias JD: A review of anesthetic management during laparoscopic procedures, emphasizing concerns in the pediatric population. Am J Anesthesiol 25:165, 1998 62. Tobias J D Anesthetic considerations for endoscopic procedures in children. Semin Pediatr Surg 2190,1993 63. Tobias J D Anesthetic considerations for laparoscopy in children. Semin Laparosc Surg 5:60, 1998 64. Treacy PJ, Johnson AG: Is the laparoscopic bubble bursting? Lancet 346(suppl):23,1995 65. Varlet F, Tardieu D, Limonne B, et al: Laparoscopic versus open appendectomy in children: Comparative study of 403 cases. Eur J Pediatr Surg 4:333, 1994 66. Verghese C, Brimacombe JR Survey of laryngeal mask airway usage in 11,910 patients: Safety and efficacy for conventional and nonconventional usage. Anesth Analg 82129,1996 67. Waldschmidt J, Schier F: Laparoscopic surgery in neonates and infants. Eur J Pediatr Surg 1:145, 1991 68. Walsh MT, Vetter TR Anesthesia for pediatric laparoscopic cholecystectomy. J Clin Anesth 4406,1992

Address reprint requests to John H. Pennant, MA, MB, BS, FRCA Department of Anesthesiology & Pain Management University of Texas southwestern Medical School 5323 Harry Hines Blvd Dallas, TX 75390-9068