The use of a mobile computed tomography scanner in the pediatric intensive care unit to evaluate airway stenting and lung volumes with varying levels of positive end-expiratory pressure

OBJECTIVE

Presentation of a case report describing the use of a mobile computed tomography (CT) scanner in the pediatric intensive care unit (PICU) to radiographically evaluate tracheobronchial stenting and lung volumes while using different levels of positive end-expiratory pressure (PEEP) and positioning in a critically ill infant.

DESIGN

Case report of a single patient.

SETTING

Pediatric intensive care unit in a University Hospital.

PATIENT

A 6-month-old premature infant with bronchopulmonary dysplasia, tracheobronchomalacia, and progressive respiratory failure.

INTERVENTIONS

CT scans of the chest were performed by using a mobile CT scanner in the PICU. Serial CT scans were performed at PEEP levels of 5, 10, 15, and 20 cm H(2)O in both the supine and prone position. Scheduled medical care and standard monitoring were continued during the course of the CT scans.

MEASUREMENTS AND MAIN RESULTS

Identical anatomic levels demonstrating the trachea, bronchi, and lung parenchyma were compared while different levels of PEEP and supine or prone positioning were used. From these comparisons, the level of PEEP in which lung volumes were optimized was radiographically determined. No significant changes in large airway caliber were observed. There was no difference noted between prone and supine positioning. CT scans were completed with minimal disruption to the patient's care.

CONCLUSIONS

Mobile CT scanners can be used in the PICU for the diagnostic evaluation of critically ill children. This option allows for the continuation of medical therapies and monitoring in the intensive care setting while avoiding the potential complications of transporting a critically ill child to the radiology department. The use of mobile CT scanners may disrupt PICU routine and is more expensive than use of fixed CT scanners. Mobile CT scanners may be useful in radiographically determining the optimal level of PEEP in infants with tracheobronchomalacia and bronchopulmonary dysplasia.

Use of acetazolamide to decrease cerebrospinal fluid production in chronically ventilated patients with ventriculopleural shunts

Acetazolamide (ACTZ), a carbonic anhydrase inhibitor, has been shown to decrease cerebrospinal fluid (CSF) production in both in vivo and in vitro animal models. We report two children with hydrocephalus who experienced multiple shunt failures, and who had externalised ventriculostomy drains (EVD) prior to ventriculopleural shunt placement. The effects of increasing doses of ACTZ on CSF production and subsequent tolerance to ventriculopleural shunts were evaluated. The patients had a 48% and a 39% decrease in their EVD CSF output when compared to baseline with maximum ACTZ dose of 75 mg/kg/day and 50 mg/kg/day, respectively (p < 0.05). This is the first report of change in CSF volume in children after extended treatment with ACTZ. ACTZ treatment in mechanically ventilated paediatric patients with hydrocephalus may improve tolerance of ventriculopleural shunts and minimise respiratory compromise. Potassium and bicarbonate supplements are required to correct metabolic disturbances.

Prospective evaluation of propofol anesthesia in the pediatric intensive care unit for elective oncology procedures in ambulatory and hospitalized children

OBJECTIVES

To evaluate our experience with propofol anesthesia delivered by pediatric intensivists in the pediatric intensive care unit (PICU) to facilitate elective oncology procedures in children performed by pediatric oncologists.

METHODS

Elective oncology procedures performed with propofol anesthesia in our multidisciplinary, university-affiliated PICU were prospectively evaluated over a 7-month period. Ambulatory and hospitalized children were prescheduled for their procedure, underwent a medical evaluation, and met fasting requirements before the start of anesthesia. Continuous cardiorespiratory and neurologic monitoring was performed by a pediatric intensivist and a PICU nurse, while the procedure was performed by a pediatric oncologist. Propofol was delivered in intermittent boluses to achieve the desired level of anesthesia. Information studied included patient demographics, procedures performed, induction and total doses of propofol used, the duration of the different phases of the patient's PICU stay, the occurrence of side effects, the need for therapeutic interventions, and the incidence of recall of the procedure.

RESULTS

Fifty procedures in 28 children (mean age: 7.5 +/- 4.3 years) were evaluated. Sixty-one percent of patients had established diagnoses. Fifty-four percent of procedures were lumbar puncture with intrathecal chemotherapy administration and 26% of procedures were bone marrow aspirations with biopsy. Induction propofol doses were 2. 0 +/-.8 mg/kg for ambulatory and hospitalized patients, while total propofol doses were 6.6 +/- 2.3 mg/kg and 7.9 +/- 2.4 mg/kg for ambulatory and hospitalized patients, respectively. Induction time was 1.5 +/-.7 minutes, recovery time was 23.4 +/- 11.5 minutes, and total PICU time was 88.8 +/- 27.7 minutes. Transient decreases in systolic blood pressure less than the fifth percentile for age occurred in 64% of procedures, with a mean decrease of 25% +/- 10%. Intravenous fluids were administered in 31% of these cases. Hypotension was more common in ambulatory patients but was not predicted by propofol dose, anesthesia time, or age. Partial airway obstruction was noted in 12% of procedures while apnea requiring bag-valve-mask ventilation occurred in 2% of procedures. Neither was associated with age, propofol dose, or the duration of anesthesia. All procedures were successfully completed and there were no incidences of recall of the procedure.

CONCLUSIONS

Propofol anesthesia is effective in achieving patient comfort and amnesia, while optimizing conditions for elective oncology procedures in children. Although transient hypotension and respiratory depression may occur, propofol anesthesia seems to be safe to use for these procedures in the PICU setting. Recovery from anesthesia was rapid and total stay was brief. Under the proper conditions, propofol anesthesia delivered by pediatric intensivists in the PICU is a reasonable option available to facilitate invasive oncology procedures in children.

Noninvasive positive-pressure ventilation facilitates tracheal extubation after laryngotracheal reconstruction in children

Tracheal extubation after laryngotracheal reconstruction in children may be complicated by postoperative tracheal edema and pulmonary dysfunction. The replacement of a tracheal tube in this situation may exacerbate the existing injury to the tracheal mucosa, complicating subsequent attempts at tracheal extubation. We present two cases where noninvasive positive-pressure ventilation was employed to treat partial airway obstruction and respiratory failure in two children following laryngotracheal reconstruction. Noninvasive positive-pressure ventilation served as a bridge between mechanical ventilation via a tracheal tube and spontaneous breathing, providing airway stenting and ventilatory support while tracheal edema and pulmonary dysfunction were resolved. Under appropriate conditions, noninvasive positive-pressure ventilation may be useful in the management of these patients.

Propofol anesthesia for invasive procedures in ambulatory and hospitalized children: experience in the pediatric intensive care unit

OBJECTIVES

To describe our experience with propofol anesthesia to facilitate invasive procedures for ambulatory and hospitalized children in the pediatric intensive care unit (PICU) setting.

METHODS

We retrospectively reviewed the hospital records of 115 children who underwent 251 invasive procedures with propofol anesthesia in our multidisciplinary, university-affiliated PICU during a 20-month period. All patients underwent a medical evaluation and were required to fast before anesthesia. Continuous monitoring of the patient's cardiorespiratory and neurologic status was performed by a pediatric intensivist, who also administered propofol in intermittent boluses to obtain the desired level of anesthesia, and by a PICU nurse, who provided written documentation. Data on patient demographics, procedures performed, doses of propofol used, the occurrence of side effects, induction time, recovery time, and length of stay in the PICU were obtained.

RESULTS

Propofol anesthesia was performed successfully in all children (mean age, 6.4 years; range, 10 days to 20.8 years) who had a variety of underlying medical conditions, including oncologic, infectious, neurologic, cardiac, and gastrointestinal disorders. Procedures performed included lumbar puncture with intrathecal chemotherapy administration, bone marrow aspiration and biopsy, central venous catheter placement, endoscopy, and transesophageal echocardiogram. The mean dose of propofol used for induction of anesthesia was 1.8 mg/kg, and the total mean dose of propofol used was 8.8 mg/kg. In 13% of cases, midazolam also was administered but did not affect the doses of propofol used. The mean anesthesia induction time was 3.9 minutes, and the mean recovery time from anesthesia was 28.8 minutes for all patients. The mean PICU stay for ambulatory and ward patients was 140 minutes. Hypotension occurred in 50% of cases, with a mean decrease in systolic blood pressure of 25%. The development of hypotension was not associated with propofol doses, the concomitant use of midazolam, or the duration of anesthesia, but was associated with older patient age. Hypotension was transient and not associated with altered perfusion. Intravenous fluid was administered in 61% of the cases in which hypotension was present. Respiratory depression requiring transient bag-valve-mask ventilation occurred in 6% of cases and was not associated with patient age, propofol doses, concomitant use of midazolam, or the duration of anesthesia. Transient myoclonus was observed in 3.6% of cases. Ninety-eight percent of procedures were completed successfully, and no procedure failures were considered secondary to the anesthesia. Patients, parents, and health care providers were satisfied with the results of propofol anesthesia.

CONCLUSIONS

Propofol anesthesia can safely facilitate a variety of invasive procedures in ambulatory and hospitalized children when performed in the PICU and is associated with short induction and recovery times and PICU length of stay. Hypotension, although usually transient, is common, and respiratory depression necessitating assisted ventilation may occur. Therefore, appropriate monitoring and cardiorespiratory support capabilities are essential. Propofol anesthesia in the PICU setting is a reasonable therapeutic option available to pediatric intensivists to help facilitate invasive procedures in ambulatory and hospitalized children.

Interleukin-6 levels in serum and lung lavage fluid of children undergoing open heart surgery correlate with postoperative morbidity

OBJECTIVE

To evaluate the relationship of perioperative levels of interleukin 6 (IL-6) in serum and bronchoalveolar fluid with morbidity and mortality in children undergoing cardiopulmonary bypass (CPB).

DESIGN

Prospective, noninterventional study.

SETTING

Operating room and pediatric intensive care unit (PICU) of a university hospital.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

IL-6 levels were measured in serum and lung lavage fluid obtained before, during, and after CPB using the B9.9 bioassay. Alveolar epithelial lining fluid (AELF) volume was calculated using the urea correction method. Mean intraoperative AELF IL-6 levels increased fourfold compared to preoperative levels, and mean serum IL-6 levels increased fivefold after CPB. Mean intraoperative AELF IL-6 levels correlated with intraoperative blood transfusion (r2 = 0.18; p = 0.049) and duration of inotropic support (r2 = 0.29; p = 0.009), mechanical ventilation (r2 = 0.24; p = 0.019), and PICU stay (r2 = 0.29; p = 0.008). Mean serum IL-6 levels 2 h after CPB correlated with intraoperative blood transfusion (r2 = 0.3;p = 0.007), and with Pediatric Risk of Mortality score on postoperative day 3 (r2 = 0.24; p = 0.022), and were higher in patients with massive fluid retention (p = 0.014) and in nonsurvivors (p = 0.003).

CONCLUSIONS

Serum and alveolar IL-6 levels increase after CPB, and correlate with postoperative morbidity. Serum IL-6 levels also correlate with mortality. They may be useful in assessing the severity of the systemic inflammatory response after CPB.

Maturation alters the pulmonary arterial response to hypoxia and inhaled nitric oxide in the presence of endothelial dysfunction

Surgical intervention in ever younger patients has led to a new appreciation of the unique physiology of the neonate. Specifically, newborn patients may respond very differently to hypoxic episodes and subsequent treatment with inhaled nitric oxide than older infants. In the current study, we examined differences in the pulmonary arterial response to hypoxia and inhaled nitric oxide in 48-hour-old (n = 8) and 14-day-old (n = 8) Yorkshire pigs in a model of nitric oxide synthase inhibition, as might be seen with endothelial dysfunction. Data were acquired after treatment with the nitric oxide synthase inhibitor N omega-nitro-L-arginine during hypoxia (inspired oxygen fraction = 0.10) and during inhalation of nitric oxide (100 ppm). Input mean impedance, reflecting distal arteriolar vasoconstriction, and characteristic impedance, reflecting proximal arterial geometry and distensibility, were calculated. The modulus of elasticity, a measure of the "stiffness" of the proximal vessels, was also calculated. Hypoxia caused a large increase in input mean impedance in both 48-hour-old and 14-day-old pigs (4826 +/- 272 versus 8744 +/- 488 dyne.cm.sec-5 and 3129 +/- 73 versus 6000 +/- 134 dyne.cm.sec-5, respectively; p = 0.0078). Characteristic impedance was not altered in the younger animals (1171 +/- 76 dyne.cm.sec-5) but increased in the older animals (419 +/- 15 versus 797 +/- 20 dyne.cm.sec-5. p = 0.0078). Older animals also experienced an increase in the modulus elasticity (1.92E06 +/- 3.2E05 versus 1.05E07 +/- 3.9E05 dyne/cm2, p = 0.0078). These data show that inhibited nitric oxide production, as might be seen in endothelial dysfunction, potentiates the profound hypoxic vasoconstriction observed at the level of the distal pulmonary arterioles in both neonatal and infant animals. In contrast, only older animals had a stiffening of the larger, more proximal vessels with hypoxia. In both age groups, inhaled nitric oxide effectively reduced the increases in impedance.

Initial postoperative serum lactate levels predict survival in children after open heart surgery

OBJECTIVE

To evaluate the relationship between postoperative serum lactate levels and outcome in children undergoing open heart surgery.

DESIGN

Prospective, noninterventional study.

SETTING

Pediatric intensive care unit (PICU) of a university hospital.

PATIENTS

41 nonconsecutive children who had had cardiopulmonary bypass for repair of congenital heart disease.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Serum lactate levels were measured on admission to the PICU immediately after open heart surgery. Lactate levels were correlated with bypass and cross clamp times, estimated intraoperative blood loss, lowest temperature on bypass, admission Pediatric Risk of Mortality score, anion gap, and measures of postoperative morbidity. Mean lactate levels on admission to the PICU were 6.86 +/- 0.79 mmol/l for nonsurvivors (n = 7) and 2.38 +/- 0.13 mmol/l for survivors (n = 34) (p < 0.0001), and 4.87 +/- 0.7 mmol/l and 2.35 +/- 0.19 mmol/l, for patients with (n = 11) and without (n = 30) multiple organ system failure, respectively (p < 0.0001). Admission lactate levels correlated with all measurements of postoperative morbidity. A serum lactate level of greater than 4.2 mmol/l had a positive predictive value of 100% and a negative predictive value of 97% for postoperative death.

CONCLUSIONS

Initial postoperative serum lactate levels after pediatric open heart surgery may be predictive of outcome. Lactate levels are also higher in patients who go on to develop multiple organ system failure. Elevated postoperative lactate levels may reflect intraoperative tissue hypoperfusion, and measures aimed at increasing oxygen delivery, with normalization of lactate, may improve patient outcome.

Pulmonary arterial endothelial dysfunction potentiates hypercapnic vasoconstriction and alters the response to inhaled nitric oxide

BACKGROUND

Pulmonary hypertensive crisis can be initiated by episodes of hypercapnic acidosis. Hypercapnic vasoconstriction in the newborn pulmonary arterial circulation may be modulated by endogenous production of nitric oxide (NO) by the endothelial cell and effectively treated with inhalation of NO.

METHODS

Sixteen 48-hour-old piglets were randomized to receive a hypercapnic challenge after administration of either saline vehicle or the NO synthase inhibitor N-omega-nitro-L-arginine (L-NA). Pulmonary arterial pressure, flow, and radius measurements were taken at baseline, after infusion of vehicle or L-NA, during hypercapnia (inspired fraction of carbon dioxide, 0.15), and during inhalation of NO (100 ppm). Fourier analysis was used to calculate input mean impedance, reflecting distal arteriolar vasoconstriction, and characteristic impedance, reflecting proximal arterial geometry and distensibility.

RESULTS

Input mean impedance was increased with L-NA administration. Animals pretreated with L-NA also underwent a much larger increase in input mean impedance with exposure to hypercapnia than untreated animals. Characteristic impedance increased in the treated animals, but not in the controls.

CONCLUSIONS

In the newborn pulmonary arterial circulation, endogenous NO production by the endothelial cell modulates resting tone distally, but not proximally. In addition, lack of a functional endothelium markedly potentiates the distal vasoconstrictor response to hypercapnia and produces proximal vasoconstriction. Despite impaired endothelial function, inhaled NO remains an effective vasodilator in hypercapnic pulmonary vasoconstriction.

Extracorporeal membrane oxygenation for cardiac rescue in children with severe myocardial dysfunction

OBJECTIVE

To assess the experience and efficacy of extracorporeal membrane oxygenation (ECMO) for cardiac rescue in patients with presumptively lethal cardiac dysfunction at the Children's Hospital of Pittsburgh.

DESIGN

Retrospective analysis of patient records from a 9-yr period.

SETTING

A 22-bed tertiary care pediatric intensive care unit (ICU) with an average of 1,400 admissions per year. An average of 150 open cardiotomy surgeries are performed per year, and all postoperative and severely ill cardiac patients are cared for in the ICU.

PATIENTS

A total of 29 pediatric ICU patients with myocardial failure received ECMO throughout the 9-yr study period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic information, underlying cardiac defect, intraoperative and postoperative data, postoperative course, details of ECMO treatment, and outcome were collected. Comparison of survivors with nonsurvivors was performed using the Mann-Whitney U test for continuous variables. Twenty-three (79%) of 29 patients recovered myocardial function while undergoing ECMO, 18 (62%) of 29 patients were successfully decannulated, and 13 (45%) of 29 patients survived to hospital discharge. Long-term survival rate was 11 (38%) of 29 patients. Three (60%) of five bridge-to-heart transplant patients survived. Eleven (65%) of 17 patients who suffered cardiac arrest before ECMO, survived to discharge and nine (53%) of these 17 patients remain long-term survivors. Survival rate in patients who required cardiac massage for > 15 mins before cannulation was six (55%) of 11 patients.

CONCLUSIONS

Patients with severe myocardial dysfunction who fail conventional therapy can be successfully supported with ECMO during the period of myocardial recovery. ECMO can also provide a viable circulatory support system in patients with prolonged cardiac arrest who fail conventional resuscitation techniques. ECMO is also an effective means of support as a mechanical bridge to heart transplantation.

Extracorporeal membrane oxygenator rescue in children during cardiac arrest after cardiac surgery

BACKGROUND

Conventional cardiopulmonary resuscitation (CPR) for cardiac arrest after open-heart surgery in children is often unsuccessful despite the ability to perform open-chest massage. The purpose of this study was to review our results with mechanical support as rescue therapy in children with sudden circulatory arrest after cardiac surgery.

METHODS AND RESULTS

From 1981 through 1991, we have used mechanical support with an extracorporeal membrane oxygenator (ECMO) circuit for cardiac support in 33 children. Eleven of the 33 patients (age, 15 +/- 7 months) suffered cardiac arrest intractable to conventional open-chest massage 39 +/- 15 hours after an open-heart procedure. The mean duration of CPR was 65 +/- 9 minutes until ECMO flow was started. ECMO support was continued for 112 +/- 8 hours. One patient had ECMO discontinued due to bleeding (survived); three were discontinued from ECMO and died from neurological complications; and one died of cardiac dysfunction. Sepsis on ECMO was seen in one patient (survived). Overall early survival was seven of 11 (64%) with one patient requiring heart transplantation due to irreversible cardiac dysfunction. One child died late (1 month) after ECMO support. There were no long-term sequelae in the survivors.

CONCLUSIONS

We conclude that ECMO rescue in children with postcardiotomy cardiac arrest is a feasible option in selected patients even after prolonged CPR (as long as 60 minutes).

Progress in pediatric extracorporeal membrane oxygenation

Prolonged complete support of the circulation and of gas exchange can be achieved by extracorporeal membrane oxygenation (ECMO) in infants and children with potentially reversible, albeit life-threatening, disease. This allows lung rest or cardiac rest at times when dependence in those organs would be physiologically expensive. Although ECMO has no intrinsic healing powers, pediatric hearts and lungs exhibit tremendous recuperative power once the cycle of injury, inefficient performance, abuse, and secondary injury can be broken. Recent advances in technology, although impressive, do not explain the rapid growth of clinical interest in ECMO. Most recent progress in ECMO derives from refinement of clinical practices and the application of this technology to new patient populations. ECMO is not itself an experiment. It is the application of ECMO that is experimental.

Undiagnosed abuse in children younger than 3 years with femoral fracture

We retrospectively evaluated 138 children younger than 3 years with femoral fractures who presented to the emergency departments of three major Michigan hospitals between 1979 and 1983. Patients were classified into one of the following four subgroups based on presenting history: accident (22%), bone pathology (8%), abuse (10%), and uncertain origin (60%). Distribution of common fracture types among the four subgroups was similar. Of the uncertain group, 22 cases of abuse were identified during admission and 7 additional cases were found at a later date. The total number of femoral fractures secondary to abuse was 43 (31%) of 138. Children younger than 3 years presenting with a femoral fracture should evoke a high suspicion for abuse.