Systemic injection of AAV9 carrying a periostin promoter targets gene expression to a myofibroblast-like lineage in mouse hearts after reperfused myocardial infarction.

Adeno-associated virus (AAV) has been used to direct gene transfer to a variety of tissues, including heart, liver, skeletal muscle, brain, kidney and lung, but it has not previously been shown to effectively target fibroblasts in vivo, including cardiac fibroblasts. We constructed expression cassettes using a modified periostin promoter to drive gene expression in a cardiac myofibroblast-like lineage, with only occasional spillover into cardiomyocyte-like cells. We compared AAV serotypes 6 and 9 and found robust gene expression when the vectors were delivered by systemic injection after myocardial infarction (MI), with little expression in healthy, non-infarcted mice. AAV9 provided expression in a greater number of cells than AAV6, with reporter gene expression visible in the cardiac infarct and border zones from 5 to 62 days post MI, as assessed by luciferase and Cre-activated green fluorescent protein expression. Although common myofibroblast markers were expressed in low abundance, most of the targeted cells expressed myosin IIb, an embryonic form of smooth muscle myosin heavy chain that has previously been associated with myofibroblasts after reperfused MI. This study is the first to demonstrate AAV-mediated expression in a potentially novel myofibroblast-like lineage in mouse hearts post MI and may open new avenues of gene therapy to treat patients surviving MI.

Intracerebroventricular delivery of self-complementary adeno-associated virus serotype 9 to the adult rat brain.

Gene therapy for the central nervous system is poised to become a powerful treatment for numerous neurological disorders. Adeno-associated viral vectors based on serotype 9 (AAV9) have proven themselves to be strong candidates for delivering gene-based therapies throughout the brain and spinal cord when administered intravenously, intrathecally, intracisternally, and intracerebroventricularly (i.c.v.). Previous studies of i.c.v.-delivered self-complimentary AAV9 have been performed in neonatal mice with delivery of a single dose. However, before clinical trials can be considered, more information is required about the dose-response relationship for transduction efficiency in adult animals. In the current study, three doses of self-complementary AAV9 were administered to adult rats. High levels of transduction were observed in the hippocampus, cerebellum and cerebral cortex, and transduction increased with increasing dosage. Both neurons and astrocytes were transduced. There was no evidence of astrocytosis at the doses tested. Preliminary results from pigs receiving i.c.v. self-complementary AAV9 are also presented. The results of this study will serve to inform dosing studies in large animal models before clinical testing.

Effects of static stretching on leg power during cycling.

AIM: This study investigated the effects of warm-up involving static stretching on leg power. It was expected that the inclusion of static stretching in the warm-up would decrease leg power. METHODS: Twenty-seven healthy volunteers (16 male, 11 female) participated in the study. A prospective, repeated measures design was implemented where volunteers underwent 2 testing sessions at least 24 hours apart. One testing session involved a control warm-up (5 min submaximal cycling) followed by 4 10-s leg power tests at 5, 20, 40 and 60 min postwarm-up. For the other testing session, the subjects performed 5 min of submaximal cycling followed by 15 min of lower body static stretching and then the four leg power tests. Relative peak power, time to peak power and relative total work were measured for each leg power test. RESULTS: Peak power and total work were significantly greater after the static stretching warm-up compared to the control warm-up on all power tests. Peak power was achieved more quickly for the static stretching warm-up compared to the control warm-up on the 5 min test only. CONCLUSIONS: A warm up that includes static stretching has beneficial effects on anaerobic power events in comparison to submaximal cycling alone.

Effects of beta-hydroxy-beta-methylbutyrate and creatine monohydrate supplementation on the aerobic and anaerobic capacity of highly trained athletes.

AIM: The aim of this study was to investigate the effects of 6 wks oral supplementation of beta-hydroxy-beta-methylbutyrate (HMB) and a mixture of HMB and creatine monohydrate (HMBCr) on aerobic and anaerobic capacity in highly trained athletes. It was hypothesised that HMB and HMBCr would have positive effects on aerobic and anaerobic power. METHODS: A prospective study involving a repeated measures design was utilised where subjects underwent testing prior to, and immediately after, a 6 wks supplementation period. Elite, male rugby league players (n=27) were divided into 3 groups, a control group (n=6), a HMB group (3 g/d; n=10) and a HMBCr group (3 g/d HMB + 3 g/d Cr; n=11). Testing involved a multistage fitness test to determine aerobic power and a 60 sec maximal cycle test to determine anaerobic capacity. Peak power, total work and peak lactate levels were measured in the anaerobic cycle test. RESULTS: Two-way repeated measures ANOVA revealed no effect of HMB or HMBCr on any of the measured parameters in comparison to the control group. CONCLUSION: Aerobic and anaerobic ability of highly trained male athletes is unaffected by 6 wks oral supplementation with HMB or a combination of HMB and creatine monohydrate.

Immaturity or starvation? Longitudinal study of leptin levels in premature infants.

OBJECTIVE: Leptin, the protein product of the ob gene, is a potential placental growth factor and is integral to the body's system of energy regulation as shown in animal models. Premature infants are especially vulnerable to changes in energy regulation, and several studies have demonstrated a rapid fall in leptin values at birth. The purpose of the present investigation was to measure leptin levels in premature infants throughout hospitalization. METHODS: Eligible infants were less than 32 weeks' gestation, appropriate for gestational age, and hospitalized at Christiana Hospital Special Care Nursery. Serum samples for leptin analysis were drawn within 24 h of birth and twice a week thereafter until discharge. Concurrent growth measurements were obtained with each leptin sample. Body mass index, ponderal index, and midarm circumference/head circumference ratios were calculated to assess growth. RESULTS: Leptin levels were low and remained low for the duration of the premature infants' hospitalization (mean +/- SD = 1.35 +/- 0.63 ng/ml/ml, range 0-3.06). After controlling for weight, there was a small (r(2) = 0.1, p < 0.00001) but significant correlation between leptin and postnatal age after 4 days of age. Despite an increase in caloric intake during the study period, there was no relationship between leptin and caloric intake. There were significant negative correlations between measurements of growth and both leptin and the leptin/weight ratio. Maternal diabetes and the use of steroids had small but significant effects on the leptin/weight ratio. CONCLUSION: In this population of predominantly female premature infants, leptin levels were very low as compared to term infants, children and adults, and did not change appreciably over the study period. The low leptin levels seen in these premature infants are similar to those levels seen in malnourished adults, anorexics, and in animal models of starvation. We speculate that a critical adipose store needs to be reached before increased amounts of leptin can be adequately produced. Persistently low leptin levels may also reflect an immaturity in the hypothalamic-pituitary-adrenal axis.

Novel effect of leptin on small intestine adaptation.

BACKGROUND: Leptin is a 16-kDa peptide produced by adipocytes that plays an important role in the regulation of body fat and satiety. We have previously shown that leptin is a growth factor for normal rat small intestine. This study was designed to examine the effect of systemic leptin administration on small bowel absorptive function after massive small bowel resection (MSBR). MATERIALS AND METHODS: Twenty-one adult male Sprague-Dawley rats underwent an 80% small bowel resection and end-to-end jejunoileal anastomosis. Seven days following resection, all rats had placement of a jugular venous catheter connected to a subcutaneously placed osmotic minipump and were divided into three groups based on the content of each minipump: Group 1 (n = 7) 0.1% bovine serum albumin; Group 2 (n = 7) leptin 2 microg/kg/day; and Group 3 (n = 7) leptin 4 microg/kg/day. Following a 14-day infusion period, [(14)C]galactose absorption was measured using a closed-recirculation technique. Mucosal DNA content was determined for all groups using a standard DNA purification kit. Mucosal RNA was extracted and RT-PCR was performed using the following primers: sodium/glucose cotransporter (SGLT-1), fructose transporter (GLUT-5), and glyceraldehyde-3-phosphate dehydrogenase, an internal standard. PCR products were separated on a 4% agarose gel and relative band intensities were measured. Statistical analysis was performed using ANOVA and expressed as means +/- SEM. RESULTS: Group 2 showed a 44% increase in galactose absorption (P < 0.01) and a 14% increase in GLUT-5 band intensity (P < 0.05), but no change in DNA content or SGLT band intensity. CONCLUSIONS: This study demonstrates for the first time that leptin enhances small intestine carbohydrate absorption beyond the normal adaptive response following MSBR. Leptin may be clinically useful in patients with inadequate intestinal function.

Managing mature cystic teratomas of the ovary.

Mature cystic teratomas (MCT), commonly called dermoid cysts, are the most common benign germ cell tumors of the ovary in women of reproductive age. Future fertility is of major concern among these women; therefore, the surgical management must focus on preserving ovarian tissue and minimizing adhesion formation. Patients requiring surgery should be appropriately counseled about the risks and benefits of laparoscopy and laparotomy, the risks of intraoperative MCT spillage and adhesion formation. In addition, the risks of recurrence and malignant transformation should be discussed. The parents of children with MCTs have the same concerns as older women and a similar discussion should take place. The goal of this article is to review these issues and provide the physician with the information to counsel their patients preoperatively.

Colposcopy in pregnancy: directed brush cytology compared with cervical biopsy.

OBJECTIVE: To evaluate colposcopically directed brush cytology as a substitute for directed biopsy of acetowhite lesions identified during pregnancy. METHODS: Pregnant patients eligible for the study were referred for colposcopic evaluation for either newly diagnosed abnormal cervical cytology or follow-up of a previously diagnosed squamous intraepithelial lesion (SIL). All patients with acetowhite lesions underwent colposcopically directed brush cytology followed by directed biopsy. RESULTS: Of 81 pregnant patients referred, 50 paired samples of colposcopically directed brush cytology and directed biopsies were evaluated from 49 patients. One patient was sampled in the first and third trimesters and one patient's brush cytology was unsatisfactory for interpretation because of clumping artifact, leaving 49 brush-biopsy pairs that were satisfactory for examination. One patient in the study group had an intrauterine fetal death of uncertain cause, remote from the time of biopsy. Compared with the corresponding biopsy, the directed brush caused significantly less blood loss (P < .001). For all diagnostic categories, directed cytology demonstrated a good degree of correlation with biopsy (kappa = 0.73). The brush technique correctly identified 12 of 14 cases (86%) of biopsy-proved cervical intraepithelial neoplasia II-III as high-grade SIL. If one considers "atypical squamous cells, favor human papillomavirus effect" as a true positive, brush sensitivity was 88 +/- 9% and specificity was 74 +/- 12%, with an accuracy of 80%. CONCLUSION: In the absence of lesions suspicious for carcinoma, colposcopically directed brush cytology is a safe substitute for directed biopsy in pregnant patients.

An analysis of two versus three grades for endometrial carcinoma.

Introduction. The current grading of uterine endometrioid adenocarcinoma utilizes a three-grade system based on the amount of nonsquamous solid histologic architecture. Of these three grades, we questioned the practical clinical utility of the intermediate grade. Methods. We retrospectively reviewed endometrial biopsy and uterine histology specimens, quantifying the percentage amount of nonsquamous solid tumor by intervals of 10. We then compared these percentage values to other histopathologic prognostic variables. Results. Eighty-five Stage I and II endometrioid adenocarcinoma patients had their preoperative endometrial curettings and operative hysterectomy pathology reviewed independently by two gynecologic pathologists for surgical staging and outcome with a mean follow-up of 6 years. Using a two-tiered system for assessing uterine tumor grade with a delineating value of 20% nonsquamous solid tumor, we found less interobserver variation (kappa = 0.966) compared to the current three-tiered grading system (kappa = 0.526). There were no differences between the two- and three-tiered grading systems regarding myometrial invasion, lymph vascular space invasion, and survival. In the diagnosis of endometrial biopsies, the two-tiered system also improved the prediction of uterine histology grade over the three-tiered system, 90 and 63%, respectively. Conclusion. A two-grade architecture system with a delineation value of 20% would be more reliable and less cumbersome and would have the same or better prognostic significance as the currently used three-grade system.

Endometrial stromal sarcoma involving the placenta.

This report presents two cases of endometrial sarcoma tumor detected in decidua submitted with placentas for pathologic evaluation. The first patient had low-grade endometrial stromal sarcoma discovered in the omentum and decidua at the time of a cesarean section for placenta previa. The second patient underwent a cesarean section for breech presentation and was noted to have a mass beneath the placenta that was histologically compatible with low-grade endometrial stromal sarcoma. We believe these to be the first reported cases of endometrial stromal sarcoma involving the decidua. These findings should elevate awareness that endometrial stromal tumors may be detected during placental examination.

Leptin expression in human mammary epithelial cells and breast milk.

Leptin has recently been shown to be produced by the human placenta and potentially plays a role in fetal and neonatal growth. Many functions of the placenta are replaced by the mammary gland in terms of providing critical growth factors for the newborn. In this study, we show that leptin is produced by human mammary epithelial cells as revealed by RT/PCR analysis of total RNA from mammary gland and immunohistochemical staining of breast tissue, cultured mammary epithelial cells, and secretory epithelial cells present in human milk. We also verify that immunoreactive leptin is present in whole milk at 30- to 150-fold higher concentrations than skim milk. We propose that leptin is secreted by mammary epithelial cells in milk fat globules, which partition into the lipid portion of breast milk.

Hydroxyurea, 5-fluorouracil infusion, and cisplatin adjunct to radiation therapy in cervical carcinoma: a phase I-II trial of the Gynecologic Oncology Group.

BACKGROUND: In a previous study, the Gynecologic Oncology Group (GOG) compared hydroxyurea (HDXR) and the combination of cisplatin (C) and 5-fluorouracil (5-FU) infusion as potentiators of radiation therapy. This study was undertaken to determine whether these two regimens could be combined, concurrent with pelvic radiation therapy in patients with locally advanced cervical cancer. METHODS: The GOG entered 75 eligible and evaluable patients on a Phase I-II evaluation of HDXR, C, and 5-FU as adjuncts to radiation therapy for locally advanced carcinoma of the cervix. All patients had histologically verified primary disease and confirmed negative para-aortic lymph nodes. Eligibility was limited to clinical stage IIB through IVA. HDXR was given orally, twice weekly at a dose of 2.5 g/m2; C on Days 1 and 29 at 50 mg/m2; and 5-FU by 96-hr infusion on Days 2-5 and 30-33 at a starting dose of 800 mg/m2. RESULTS: Forty-eight (64%) patients had stage IIB disease, 25 (33%) had stage IIIB, and 2 had stage IVA tumors. Primary tumors 4 cm or less in size were present in 15 patients, between 4 and 6 cm were in 27 patients, and larger than 6-cm were observed in 33 patients. Grade 3/4 acute toxicity was experienced by 41 (54.7%) patients. These acute toxicities caused delays in prescribed radiation therapy of more than 1 week in 14 (18.9%) and low doses of drug in 16 (21.3%), and only 26 (34.7%) patients had the scheduled dose escalation of 5-FU on their second course. Clinical response was excellent with complete and partial response rate of 93.3%. Median time to progression has not been reached. CONCLUSION: Although this dose and schedule could be successfully administered, the delays in therapy should be avoided by a lower starting dose of hydroxyurea. Stomatitis was not a dose-limiting toxicity. These results have formed the basis of a phase III trial comparing this regimen to two other chemoradiation regimens.

Placental leptin: an important new growth factor in intrauterine and neonatal development?

BACKGROUND: Leptin, the protein product of the ob gene, is produced by the adipocyte and seems to function as a link between adiposity, satiety, and activity. Leptin has also been found to be necessary for pubertal development, conception, and pregnancy in mice, and is increased in prepubertal children, independent of adiposity, suggesting a role in childhood growth and development. This study investigated 100 mother/newborn pairs to determine the role of leptin in neonatal development. Placental tissue was assayed for leptin mRNA to evaluate it as a source of leptin production in utero. METHODS: One hundred mother/newborn pairs were enrolled in this study. Radioimmunoassay was performed for leptin on maternal venous and newborn cord blood. Leptin concentrations were measured in 43 children in Tanner stages 1 and 2 as a control group. Placental tissue was obtained from five mothers and assayed for leptin mRNA by reverse transcription/polymerase chain reaction (RT/PCR). Human placental cell lines JAR and JEG-3 were also assayed for leptin mRNA expression. RESULTS: Leptin was present in all newborns studied at a mean concentration of 8.8 ng/mL (+/-9.6 standard deviations). Leptin concentrations in cord blood correlated with newborn weight (r = .51), body mass index (BMI) (r = .48), and arm fat (r = .42). There was no correlation between leptin and insulin. When statistically covarying for adiposity for newborns and Tanner stages 1 and 2 children, newborns had greater concentrations of leptin (mean, 10.57 ng/mL) than children (mean, 3.04 ng/mL). Leptin was present in all mothers at a mean value of 28.8 ng/mL (+/-22.2 standard deviations). Leptin concentration correlated with prepregnancy BMI (r = .56), BMI at time of delivery (r = .74), and arm fat (r = .73). Maternal leptin correlated with serum insulin (r = .49). There was no correlation between maternal and newborn leptin concentrations. Thirteen percent of newborns had higher leptin concentrations than their mothers. Placental tissue from five separate placentas expressed leptin mRNA at comparable or greater levels than adipose tissue. Two human trophoblastic placental cell lines, JAR and JEG-3, also expressed leptin mRNA. CONCLUSIONS: The correlation between leptin and adiposity found in children and adults was also found in newborns. Serum leptin concentrations in newborns were increased more than three-fold compared with children in Tanner stages 1 and 2 when controlling for adiposity, suggesting that leptin concentrations in the newborn are not explained by adiposity alone. Maternal leptin concentrations correlated with measures of adiposity at delivery but did not correlate with newborn adiposity or leptin. Leptin mRNA was expressed both in placental tissue and in two human placental cell lines. These data suggest that leptin has a role in intrauterine and neonatal development and that the placenta provides a source of leptin for the growing fetus.

Apoptosis as a measure of chemosensitivity to cisplatin and taxol therapy in ovarian cancer cell lines.

OBJECTIVE: Cisplatin- and Taxol-induced apoptosis was studied in four human ovarian cancer cell lines to evaluate apoptosis as a measure of chemosensitivity. METHODS: In vitro sensitivities of OVCAR-3, SKOV-3, UL-1, and UL-2 cells to cisplatin or Taxol were determined by the sulforhodamine B assay. Induction of apoptosis was studied by DNA fragmentation following treatment with cisplatin and/or Taxol after 24- and 48-hr exposure. DNA fragmentation was further quantitated by the diphenylamine assay and the proportion of cells in the G1, G2/M, and S phase of the cell cycle was determined by flow cytometry. Presence of the p53 gene product was examined by Western blotting. RESULTS: The four cell lines represent various sensitivities to cisplatin and Taxol (LD50 range for cisplatin, 5-30 microg/ml; Taxol, 30-1000 nM). UL-2 represents a resistant cell line which was 10-30 times resistant to Taxol and 6 times resistant to cisplatin when compared to the others. Demonstration of apoptosis correlated with the sensitivity of the cell lines to both cisplatin and Taxol for OVCAR-3 and UL-2. DNA fragmentation of OVCAR-3 was uniformly present when treated with cisplatin or Taxol, at 24 or 48 hr. UL-2 demonstrated no apoptosis after 24 or 48 hr of treatment with either cisplatin or Taxol. When sequencing experiments were performed with cisplatin and Taxol, DNA fragmentation correlated with the cytotoxicity assays, except in UL-1 cells where no significant difference was observed in different interactions of cisplatin and Taxol. Pretreatment with Taxol generally resulted in enhanced cytotoxicity in a schedule-dependent manner, and increased fragmentation was demonstrated; cisplatin pretreatment consistently resulted in decreased fragmentation. Quantitation of the fragmented DNA correlated with that seen on gel electrophoresis. OVCAR-3 and UL-1 demonstrated the greatest change from baseline at 24 hr (3.8 and 3.7 times baseline, respectively), whereas UL-2 had little change from the baseline following treatment. G1 arrest occurred more readily in OVCAR-3 and SKOV-3 cells. UL-2 cells had very little change in the proportion of cells entering G1 arrest, but had a significant increase in the G2/M proportion. In OVCAR-3, UL-1, and UL-2 cells, we demonstrated the presence of an aberrantly expressed p53 gene product, while no p53 was detected in the SKOV-3 cells. CONCLUSIONS: Our findings indicate that the ability to achieve significant cytotoxicity by cisplatin and Taxol may be directly related to the induction of apoptosis; however, cellular and genetic characteristics determine the eventual outcome of these treatments.

A rare uterine tumor presenting as deep venous thrombosis.

A 63-year-old woman with a rare pelvic tumor is presented as an example of an unusual clinical complaint for this neoplasm. The patient's original complaint was lower leg pain with swelling. Deep venous thrombosis was identified and ancillary studies confirmed the presence of a pelvic mass. Histopathologic diagnosis was a uterine tumor resembling ovarian sex cord tumor. This case illustrates the importance of considering a diagnosis of a pelvic tumor with a complaint of deep venous thrombosis.

Characteristics of gonadotropin response, follicular development, and endometrial growth and maturation across consecutive cycles of clomiphene citrate treatment.

OBJECTIVE: To examine the patterns of gonadotropin response, follicular development, and endometrial growth and maturation across consecutive cycles of clomiphene citrate (CC) treatment. DESIGN: Prospective analysis of cycle characteristics. SETTING: Academic tertiary medical center. PATIENTS: Nineteen consenting anovulatory infertile women receiving standardized, cyclic, incremental treatment with CC (50 to 150 mg/d, cycle days 5 to 9) for ovulation induction. INTERVENTIONS: In each of up to six consecutive treatment cycles, urinary LH was monitored twice daily from cycle day 10 until detection of the LH surge or day 21; blood samples and transvaginal ultrasound (US) examination were obtained on cycle days 3, 10, and every 1 to 3 days thereafter until collapse of the dominant follicle. Endometrial biopsy was performed 11 to 13 days after the LH surge in the first, third, and sixth ovulatory cycle. RESULTS: Follicular phase duration, peak follicular diameter, the number of preovulatory follicles, and peak endometrial thickness and echo pattern remained consistent across consecutive ovulatory (n = 55) and anovulatory (n = 23) treatment cycles. Endometrial dating was > or = 3 days out of phase in 2 of 31 (6%) cycles sampled. Peak serum E2 and P concentrations did not vary with cycle number or correlate with endometrial thickness or echo pattern. Cycle day 10 FSH levels were significantly higher in ovulatory subjects than in anovulatory subjects. CONCLUSIONS: Patterns of gonadotropin response, follicular development, and endometrial growth and maturation remain consistent across consecutive cycles of CC treatment.

Vulvar eccrine porocarcinoma.

A rare case of a slowly growing vulvar tumor in a 75-year-old woman is presented. This vulvar neoplasm was an eccrine porocarcinoma with left inguinal nodal metastases. This is believed to be only the second reported case of a vulvar eccrine porocarcinoma. Treatment included a left hemivulvectomy, bilateral inguinal-femoral lymphadenectomy, and postoperative radiation therapy. A review of the literature regarding this unusual malignancy is included.

Sleep fluoroscopy for localization of upper airway obstruction in children.

The management of children with upper airway obstruction (UAO) in whom previous airway surgeries or concomitant craniofacial or neuromuscular abnormalities exist is complicated by potential obstruction at multiple sites. Sleep fluoroscopy (SF) provides a dynamic representation of relative degrees of obstruction at multiple levels of the pediatric airway. Fifty-five SF studies were performed on 50 infants and children to localize obstructive sites. Correlation was assessed with findings on direct laryngoscopy and bronchoscopy under spontaneous ventilation. In 24 (44%), endoscopic and SF findings correlated exactly. The SF studies identified a site of UAO in 11 patients with normal findings on endoscopic examination and multiple sites of UAO in 16 others. Two thirds of these occurred at the hypopharynx and tongue base. The SF studies failed to detect 5 airway abnormalities in 4 patients. The sensitivity of SF for endoscopically verified laryngotracheal lesions was lowest for glottic (67%) and subglottic (70%) locations and higher for tracheal (92%) and supraglottic (100%) sites. Sleep fluoroscopy altered the course of treatment in 26 (52%) children. It appears to be a valuable adjunct to endoscopy in the identification and management of pediatric UAO when hypopharyngeal collapse or multiple levels of obstruction are suspected.

Selected risk factors in pediatric adenotonsillectomy.

OBJECTIVE: To evaluate the ability of a set of cost-effective criteria to identify before surgery the pediatric patients in whom perioperative respiratory compromise is most likely to develop after adenotonsillectomy. SETTING: A children's hospital medical center. DESIGN: Prospective study using preoperative parental questionnaires and perioperative respiratory status documentation. PATIENTS: All patients scheduled at the outpatient clinic were eligible. MAIN OUTCOME MEASURE: The development of respiratory compromise as defined by at least 1 of the following occurring more than 2 hours after surgery: an oxygen desaturation level of less than 90%, an obstructive breathing pattern, or respiratory distress requiring intervention. RESULTS: The risk of respiratory compromise was significantly increased in patients who were younger than 3 years (P < .001) and in those who had neuromuscular disorders (P < .05), chromosomal abnormalities (P < .005), difficulty in breathing during sleep (P < .005), restless sleep (P < .01), loud snoring with apnea (P < .05), or an upper respiratory tract infection within 4 weeks of surgery (P = .005). Respiratory compromise did not develop in any patients who did not snore (P < .05). CONCLUSIONS: A complete history that includes symptoms suggestive of sleep apnea will assist in the preoperative identification of pediatric patients most at risk for perioperative respiratory compromise after undergoing adenotonsillectomy. Such patients might benefit from overnight observation in a hospital setting. However, when snoring is absent, outpatient surgery is appropriate, as the risk of respiratory compromise is minimal.