Jennifer Foley

Pharmacokinetics of dexmedetomidine in postsurgical pediatric intensive care unit patients: preliminary study.

Objective: To characterize the pharmacokinetics of dexmedetomidine and monitor any dexmedetomidine-related adverse events in postoperative pediatric patients requiring short-term mechanical ventilation, analgesia, and sedation in the pediatric intensive care unit (PICU). Design: Prospective, case series. Setting: Operating room and PICU in a large, urban childrens hospital. Enrollment from February 14 to November 25, 2002. Patients: Ten children (4 months to 7.9 yrs of age) who received postoperative infusions of dexmedetomidine. Interventions: Toward the end of the operation, patients received dexmedetomidine at 1 &mgr;g/kg per hr for 10 mins. The anesthesiologist then titrated the infusion, as clinically indicated, to a rate of 0.2–0.7 &mgr;g/kg per hr. In the PICU, the infusion was titrated by the nursing staff based on assessment with a modified Ramsey Sedation Scale, while maintaining heart rate and blood pressure within normal limits for age. Dexmedetomidine was continued until the intensivist felt the patient no longer benefited, but for no longer than 24 hrs. Measurements and Main Results: At specified times during the infusion and after discontinuation, dexmedetomidine plasma concentrations were determined. Pharmacokinetic parameters were calculated using a two-compartment model. Vital signs, sedation scores, adjunct sedative or analgesic medications, and adverse events were recorded. Average duration of infusion was 18.8 hrs (range, 8–24 hrs). Means (±sd) were calculated for the following: clearance, 0.57 (±0.14) L/hr per kg; volume of distribution at steady state, 1.53 (±0.37) L/kg; and terminal elimination half-life, 2.65 (±0.88 hrs)—all similar to published values in adults. There were no serious adverse events related to dexmedetomidine. Conclusions: Dexmedetomidine, administered as a continuous infusion, produces consistent, predictable concentrations in children and infants. Further evaluations of the safety, efficacy, and pharmacodynamics of dexmedetomidine are warranted.

Loss of consciousness: when to perform computed tomography?

Objective: To determine the diagnostic value of physical examination (including neurologic exam) for positive computed tomography scan findings in children with closed head injury, Glasgow Coma Scale score 13–15 in the emergency department, and loss of consciousness or amnesia. Design: Prospective descriptive study. Setting: A large, tertiary, pediatric trauma center in San Diego County. Patients: Children ages 2–16 with an isolated closed head injury, history of loss of consciousness or amnesia, and Glasgow Coma Scale 13–15 who were referred for pediatric trauma evaluation and received a head computed tomography as part of this evaluation. Interventions: A standardized physical examination including skull/scalp exam, pupils, tympanic membrane, and brief neurologic exam was documented on each patient. Measurements and Main Results: Subjects age 2–16 being evaluated by the pediatric trauma team for closed head injury with loss of consciousness or amnesia and Glasgow Coma Scale 13–15 received a standardized physical exam, noncontrast head computed tomography scan, and follow-up telephone call at 4–6 wks. Outcome variables include intracranial injury visualized on computed tomography scan and need for neurosurgical intervention. Ninety-eight subjects were enrolled in the study over a 1-yr period. Computed tomography scans revealed evidence of intracranial injury in 13 of 98 subjects (13%). Normal examination increased the probability of a normal computed tomography scan from .87 pretest to .90 posttest. Four of 38 subjects with normal examination were noted to have evidence of intracranial injury on computed tomography. These four subjects did not require neurosurgical intervention. Two of 98 subjects underwent neurosurgical procedures. One intracranial pressure monitor was placed for decreasing level of consciousness. One subject underwent surgical elevation of a depressed skull fracture. Conclusions: Detailed clinical examination is of no diagnostic value in detecting intracranial injuries found on head computed tomography scan. Patients with observed loss of consciousness or amnesia and Glasgow Coma Scale 13–15 should have a head computed tomography scan as part of their evaluation to avoid missing an intracranial injury.

B-type Natriuretic Peptide: Perioperative Patterns in Congenital Heart Disease

OBJECTIVE B-type natriuretic peptide (BNP) has diagnostic, prognostic, and therapeutic roles in adults with heart failure. BNP levels in children undergoing surgical repair of congenital heart disease (CHD) were characterized broadly, and distinguishable subgroup patterns delineated. DESIGN Prospective, blinded, observational case series. SETTING Academic, tertiary care, free-standing pediatric hospital. PATIENTS Children with CHD; controls without cardiopulmonary disease. Interventions. None. MEASUREMENTS Preoperative cardiac medications/doses, CHD lesion types, perioperative BNP levels, intraoperative variables (lengths of surgery, bypass, cross-clamp), postoperative outcomes (lengths of ventilation, hospitalization, open chest; averages of inotropic support, central venous pressure, perfusion, urine output; death, low cardiac output syndrome (LCOS), cardiac arrest; readmission; and discharge medications). RESULTS Median BNP levels for 102 neonatal and non-neonatal controls were 27 and 7 pg/mL, respectively. Serial BNP measures from 105 patients undergoing CHD repair demonstrated a median postoperative peak at 12 hours. The median and interquartile postoperative 24-hour average BNP levels for neonates were 1506 (782-3784) pg/mL vs. 286 (169-578) pg/mL for non-neonates (P < 0.001). Postoperative BNP correlated with inotropic requirement, durations of open chest, ventilation, intensive care unit stay, and hospitalization (r = 0.33-0.65, all P < 0.001). Compared with biventricular CHD, Fontan palliations demonstrated lower postoperative BNP (median 150 vs. 306 pg/mL, P < 0.001), a 3-fold higher incidence of LCOS (P < 0.01), and longer length of hospitalization (median 6.0 vs. 4.5 days, P= 0.01). CONCLUSIONS Perioperative BNP correlates to severity of illness and lengths of therapy in the CHD population, overall. Substantial variation in BNP across time as well as within and between CHD lesions limits its practical utility as an isolated point-of-care measure. BNP commonly peaks 6-12 hours postoperatively, but the timing and magnitude of BNP elevation demonstrates notable age-dependency, peaking earlier and rising an order of magnitude higher in neonates. In spite of higher clinical acuity, non-neonatal univentricular CHD paradoxically demonstrates lower BNP levels compared with biventricular physiologies.

Blunt bowel and mesenteric injuries in children: Do nonspecific computed tomography findings reliably identify these injuries?

Objective: Abdominal computed tomography has proven accurate for the detection of pediatric solid organ injuries following blunt abdominal trauma but is less reliable in detecting blunt bowel and mesenteric injuries (BBMI). The purpose of this study was to determine the significance of nonspecific findings on abdominal computed tomography (CT) scan in children at risk for BBMI. Design: Retrospective chart review. Setting: Regional pediatric trauma center. Patients: All patients who received an abdominal CT scan as part of their evaluation following blunt abdominal trauma over a 10-yr period (September 1991 to September 2001). Interventions: None. Measurements and Main Results: Individual records were reviewed by one of the authors and analyzed for age, gender, mechanism of injury, diagnostic studies and procedures, results of initial CT scan, treatment, surgical procedures, complications, and outcome. Patients were excluded if they suffered penetrating trauma, had an abdominal CT scan performed at another institution, had a surgical procedure before CT scan, or had incomplete records. A total of 2,114 patients met inclusion criteria. Sixty-five percent were male and ages ranged from 3 wks to 18 yrs. There were 178 patients who had at least one nonspecific finding on abdominal CT scan suggestive of BBMI; 151 patients had one finding, 24 patients had two findings, and three had three findings. The risk of BBMI increased with the number of nonspecific findings (positive predictive value = 11% with at least one finding and 44% with two or more findings). This increase in positive predictive value, however, was accompanied by a reduction in sensitivity (62% and 37%, respectively). A total of 32 patients had surgically proven BBMI. Of these, eight had a single nonspecific finding on CT scan, ten had two findings, and two had three findings (12 patients had no CT findings suggestive of BBMI). There were complications in four of the 32 patients with BBMI and one death (due to laceration of the superior mesenteric artery). The complications appeared to occur independent of the time to surgical intervention. Conclusions: The presence of multiple nonspecific findings on abdominal CT scan does not reliably predict BBMI in children. Children also appear to suffer complications from BBMI less frequently than adults, regardless of the time to surgery. Therefore, nonspecific findings alone do not warrant surgical exploration. The decision to operate should instead be based on clinical data that include serial physical examinations.