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We investigate the recent history and stock identity of beluga whales (Delphinapterus leucas) in Kotzebue Sound in the Chukchi Sea, a region long frequented by large numbers of belugas in summer until their near disappearance in the 1980s. Wide variation in numbers since then suggests a complex recent history that hinders recovery efforts. Analysis of teeth sampled during the historical (pre-decline) era using ancient DNA (aDNA) methods found that the original Kotzebue Sound whales were differentiated for mitochondrial DNA (mtDNA) from other summering concentrations across the Pacific Arctic revealing a demographically distinct subpopulation where long-established migratory culture likely facilitated population divergence. Analysis of microsatellite (nDNA) and mtDNA markers in belugas from the contemporary (post-decline) era revealed that whales from other stocks likely visited Kotzebue Sound, including during two low ice years when relatively large numbers of whales were present. Some mtDNA lineages were found only in Kotzebue Sound, with one recorded in both the historical and contemporary eras. Exclusion tests found a number of whales in Kotzebue Sound during the contemporary era that had nDNA genotypes unlikely to arise in other contemporary stocks in the Pacific Arctic. Our findings indicate that the Kotzebue Sound belugas comprised a unique stock of which a few remnants likely still co-occur with belugas from other larger stocks. We recommend that the US government work through the co-management process to greatly reduce or eliminate the taking of belugas, especially adult females, likely to belong to the Kotzebue Sound stock, until they recover.

We investigate the recent history and stock identity of beluga whales (Delphinapterus leucas) in Kotzebue Sound in the Chukchi Sea, a region long frequented by large numbers of belugas in summer until their near disappearance in the 1980s. Wide variation in numbers since then suggests a complex recent history that hinders recovery efforts. Analysis of teeth sampled during the historical (pre-decline) era using ancient DNA (aDNA) methods found that the original Kotzebue Sound whales were differentiated for mitochondrial DNA (mtDNA) from other summering concentrations across the Pacific Arctic revealing a demographically distinct subpopulation where long-established migratory culture likely facilitated population divergence. Analysis of microsatellite (nDNA) and mtDNA markers in belugas from the contemporary (post-decline) era revealed that whales from other stocks likely visited Kotzebue Sound, including during two low ice years when relatively large numbers of whales were present. Some mtDNA lineages were found only in Kotzebue Sound, with one recorded in both the historical and contemporary eras. Exclusion tests found a number of whales in Kotzebue Sound during the contemporary era that had nDNA genotypes unlikely to arise in other contemporary stocks in the Pacific Arctic. Our findings indicate that the Kotzebue Sound belugas comprised a unique stock of which a few remnants likely still co-occur with belugas from other larger stocks. We recommend that the US government work through the co-management process to greatly reduce or eliminate the taking of belugas, especially adult females, likely to belong to the Kotzebue Sound stock, until they recover. [ABSTRACT FROM AUTHOR]

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives' performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs.

Background: Polysubstance use is a common, problematic behavior that increases risk of harm to self and others. Research suggests that rates may vary based on gender, sex and sexuality. Understanding the current state of this literature may inform prevention and treatment of polysubstance use, leading to reduced public health burden., Objectives: This review aimed to synthesize research on gender, sex and sexuality differences in polysubstance use in adults and adolescents., Methods: A scoping review was conducted using all EBSCO databases, PubMed and Google Scholar to identify articles examining the effects of gender, sex and sexuality on polysubstance use. Polysubstance use was defined broadly as the use of any combination of substances over any time period and included licit (alcohol, tobacco) and illicit substances, concurrent and simultaneous use, from lifetime to daily use and use at any frequency. Studies were considered if they were published in peer-reviewed journals between January 1990 and October 2020 and were written in English. Publicly available data sources were also utilized to fully capture prevalence data that has not been published elsewhere., Results: Findings were mostly inconsistent and often conflicting. Only two findings were generally consistent: adult men were overall more likely to report polysubstance use than adult women, and sexual and gender minorities report more frequent polysubstance use than non-minorities., Conclusions: Research has been unable to clearly elucidate differences in polysubstance use prevalence and patterns according to gender, sex and sexuality. Several recommendations are offered to advance future research and address limitations of current research., (© The Author(s) 2022. Medical Council on Alcohol and Oxford University Press. All rights reserved.)

Objective: Panic disorder is a debilitating psychiatric disorder that often co-occurs with substance use disorders. Given the current opioid epidemic, the high reported rates of comorbid panic disorder and opioid use disorder are particularly concerning. In this narrative review, we describe the literature on panic disorder and opioid use disorder co-occurrence., Methods: 86 studies, 26 reviews, 2 commentaries, and 5 guidelines pertaining to opioid use disorder, panic disorder, and their comorbidity were identified using all EBSCO databases, PubMed, and Google Scholar., Results: First, we review epidemiological literature on the prevalence of the comorbid condition above and beyond each disorder on its own. Additionally, we discuss the challenges that complicate the differential diagnosis of panic disorder and opioid use disorder and contribute to difficulties establishing rates of comorbidity. Second, we review three theoretical models that have been proposed to explain high rates of co-occurring panic disorder and opioid use disorder: the precipitation hypothesis, the self-medication hypothesis, and the shared vulnerability hypothesis. Third, we outline how co-occurring panic and opioid use disorder may impact treatment for each condition., Conclusion: Based on findings in the field, we provide recommendations for future research as well as treatment considerations for co-occurring panic and opioid use disorders.

This report builds on a previous study that describes the collaboration between an urban academic medical center and a rural drug treatment center, the goal of which is to provide medication-based treatment to individuals with OUD via videoconferencing. We describe results of a retrospective chart review of 472 patients treated in the program between August 2015 and April 2019. We examined several demographic and substance use variables for individuals who consented to telemedicine treatment, retention in treatment over time, and opioid use over time to understand further the impact of prescribing buprenorphine and naltrexone via telemedicine to patients in a rural OUD treatment setting. Our findings support the effectiveness of prescribing medications via telemedicine. The inclusion of more than three times as many patients as in our prior report revealed retention rates and toxicology results that are comparable to face-to-face treatment. These findings have implications for policymakers and clinicians considering implementation of similar programs., Competing Interests: Conflict of interest All authors have no conflict of interest.

The nitrogen stable isotope ratio of NOx (δ(15)N-NOx) has been proposed as a regional indicator for NOx source partitioning; however, knowledge of δ(15)N values from various NOx emission sources is limited. This study presents a detailed analysis of δ(15)N-NOx emitted from vehicle exhaust, the largest source of anthropogenic NOx. To accomplish this, NOx was collected from 26 different vehicles, including gasoline and diesel-powered engines, using a modification of a NOx collection method used by the United States Environmental Protection Agency, and δ(15)N-NOx was analyzed. The vehicles sampled in this study emitted δ(15)N-NOx values ranging from -19.1 to 9.8‰ that negatively correlated with the emitted NOx concentrations (8.5 to 286 ppm) and vehicle run time because of kinetic isotope fractionation effects associated with the catalytic reduction of NOx. A model for determining the mass-weighted δ(15)N-NOx from vehicle exhaust was constructed on the basis of average commute times, and the model estimates an average value of -2.5 ± 1.5‰, with slight regional variations. As technology improvements in catalytic converters reduce cold-start emissions in the future, it is likely to increase current δ(15)N-NOx values emitted from vehicles.

Context: People infected with HIV have a higher risk for developing insulin resistance, diabetes, and cardiovascular disease than the general population. Dipeptidyl peptidase IV (DPP4) inhibitors are glucose-lowering medications with pleiotropic actions that may particularly benefit people with HIV, but the immune and virological safety of DPP4 inhibition in HIV is unknown., Objective: DPP4 inhibition will not reduce CD4+ T lymphocyte number or increase HIV viremia in HIV-positive adults., Design: This was a randomized, placebo-controlled, double-blind safety trial of sitagliptin in HIV-positive adults., Setting: The study was conducted at an academic medical center., Participants: Twenty nondiabetic HIV-positive men and women (9.8 ± 5.5 years of known HIV) taking antiretroviral therapy and with stable immune (625 ± 134 CD4+ T cells per microliter) and virological (<48 copies HIV RNA per milliliter) status., Intervention: The intervention included sitagliptin (100 mg/d) vs matching placebo for up to 24 weeks., Main Outcome Measures: CD4+ T cell number and plasma HIV RNA were measured every 4 weeks; fasting serum regulated upon activation normal T-cell expressed and secreted (RANTES), stromal derived factor (SDF)-1α, Soluble TNF receptor II, and oral glucose tolerance were measured at baseline, week 8, and the end of study. ANOVA was used for between-group comparisons; P < .05 was considered significant., Results: Compared with placebo, sitagliptin did not reduce CD4+ T cell count, plasma HIV RNA remained less than 48 copies/mL, RANTES and soluble TNF receptor II concentrations did not increase. SDF1α concentrations declined (P < .0002) in the sitagliptin group. The oral glucose tolerance levels improved in the sitagliptin group at week 8., Conclusions: Despite lowering SDF1α levels, sitagliptin did not adversely affect immune or virological status, or increase immune activation, but did improve glycemia in healthy, nondiabetic HIV-positive adults. These safety data allow future efficacy studies of sitagliptin in HIV-positive people with cardiometabolic complications.

Background: Children with sickle cell disease frequently undergo surgical procedures that are associated with acute exacerbations of the disease. Current perioperative management practices are unclear., Objectives: We aimed at describing the current management., Methods: We conducted an electronic survey of North American members of the Society for Pediatric Anesthesia, in which we asked about their perioperative management of sickle cell disease., Results: The response rate to valid addresses was 25% (n=510/2006). In four scenarios, (a patient with mild disease undergoing a minor procedure; a patient with mild disease undergoing a more invasive procedure; a patient with severe disease undergoing a minor procedure; and a patient with severe disease undergoing a more invasive procedure) 80%, 38%, 27%, and 16% of respondents, respectively, would rely on oral fluids to hydrate patients during the preoperative fast, while 13%, 34%, 44%, and 59%, respectively, would use intravenous fluid. For the same four scenarios, 64%, 28%, 33%, and 10%, respectively, would not transfuse patients in an attempt to prevent sickle cell exacerbations, while 17%, 49%, 36%, and 51%, respectively, would transfuse to a hemoglobin concentration of 10 g·dl(-1). The tendencies to administer preoperative intravenous fluid and to transfuse blood increased with disease severity and procedure invasiveness (P<0.001). Although 89% felt comfortable managing patients with sickle cell disease, 73% thought an advisory statement on optimal perioperative management was needed., Conclusions: There is a wide variation in the management of children with sickle cell disease. Clinicians differentiate management based on disease severity and procedure type., (© 2010 Blackwell Publishing Ltd.)

Background: In this prospective, randomized, double-blind, controlled trial, our primary objective was to assess the effect of a 3 : 1 mixture of propofol and thiopental in reducing pain on injection in children. Our hypothesis was that a 3 : 1 mixture of propofol and thiopental (treatment) would reduce the incidence of pain on injection to 20% compared to the expected incidence of 40% in the control group of an 11 : 1 mixture of propofol and 2% lidocaine., Methods: Study subjects were patients 12-17 years old who were scheduled to undergo surgery and general anesthesia. Pain was assessed by a single-blinded observer present in the operating room. The major statistical method used in the analysis was multiple logistic regression., Results: Among the 164 children analyzed, 96 patients (58.5%) were male. The average age was 14.3 (sd = 1.65). The incidence of pain in the control group was 32.1% (26/81), compared to 25.3% (21/83) in the treatment group. The logistic regression analysis showed that there was not sufficient evidence that the treatment group was better than control group in reducing pain (P = 0.24). There were no significant differences in postoperative recovery time, nausea, vomiting, or blood pressure between the two groups (all P values >0.10)., Conclusion: There was not sufficient evidence to show that a 3 : 1 mixture of propofol and thiopental was better than an 11 : 1 volume admixture of propofol and lidocaine in reducing the incidence of pain on injection to 20%.

Among the most challenging patients cared for in critical care medicine are the recipients of hematopoietic stem cell transplantation (HSCT). HSCT is now widely used as a definitive therapy for the treatment of pediatric malignancies and inborn errors of metabolism. Critical care services are required for treatment of complications of HSCT. Formerly thought to have an essentially futile prognosis, outcomes from critical care of HSCT patients have demonstrated steady improvement in many areas during the past two decades. Improvements in the management of respiratory failure, sepsis, and multiple organ system failure have resulted from improvement in oncology and critical care practices. Herein, we review the methods available for outcomes prediction, recent advances in critical care of HSCT patients, and possible directions for future investigation.

Objectives: To report a case of acute chest syndrome (ACS) of sickle cell disease treated successfully with nitric oxide and to review the physiologic effects of nitric oxide and its potential ability to improve outcome in ACS., Design: Descriptive case report., Setting: Eighteen-bed pediatric intensive care unit in a university children's hospital., Patient: A 15-yr-old black male with sickle cell disease, bilateral pulmonary infiltrates, refractory hypoxemia, and unstable hemodynamics., Intervention: In addition to exchange transfusion, invasive hemodynamic monitoring, and aggressive ventilatory support, inhaled nitric oxide was administered in the gas mixture in a concentration of 20 ppm for 72 hrs., Measurements and Main Results: Cardiac output, pulmonary arterial pressure, pulmonary artery occlusion pressure, systemic vascular resistance, pulmonary vascular resistance, shunt fraction, and alveolar-arterial oxygen gradient were compared with and without inhaled nitric oxide. Marked reductions in pulmonary arterial pressure and pulmonary vascular resistance were noted. Cardiac output improved, and shunt fraction and alveolar-arterial oxygen gradient were markedly reduced. The patient required decreased ventilator and hemodynamic support and rapidly made a complete recovery., Conclusions: Nitric oxide may be beneficial for patients with ACS because of its ability to ameliorate pulmonary hypertension and ventilation/perfusion mismatch. Nitric oxide may confer some protection against polymerization of sickle hemoglobin and exert a reversible antiplatelet effect that may be beneficial in ACS. Further study is necessary to determine the safety and efficacy of inhaled nitric oxide as a treatment for ACS.

Acute severe carbon monoxide poisoning is usually easy to recognize and diagnose. However, chronic or less severe exposure may produce more subtle symptoms. We report on a 31/2-year-old girl who was admitted to the hospital several times with acute, life-threatening events, acidosis, and flu-like symptoms. The diagnosis was elusive, but after careful questioning of family members and a home visit, chronic carbon monoxide poisoning was diagnosed.

During surgical procedures, "ownership" of the patient's airway is often controversial. Communication between the anesthesiologist and the surgeon is critical. The author discusses several medical scenarios in which the anesthesiologist and surgeon must share the patient's airway. Strategies are outlined that can be used by both surgeon and anesthesiologist to ensure optimal outcome for patients.

In children undergoing inhaled induction of anesthesia with halothane who suffer bradycardia, submental glossal injection of atropine may result in more rapid onset of vagolysis than traditional intramuscular sites. We compared the intervals between injection and onset of heart rate acceleration (tHR increases) after intramuscular injection of atropine into the deltoid, vastus lateralis, and glossa in children between 1 mo and 10 yr of age scheduled for elective surgery. The tHR increases was determined by measuring the interval between atropine injection and the time point at which the slope of the heart rate curve initially became positive. To ensure that the drug had taken effect before surgical stimulation, heart rate observation was continued until it increased at least 5% above baseline with evidence of continuing acceleration. Anesthesia was induced in all subjects by mask with nitrous oxide and halothane. After tracheal intubation, constant inspired concentrations of the anesthetics were administered for 3 min. While heart rate was monitored, atropine (0.02 mg/kg) was injected into one of the three sites. Each patient's end-tidal anesthetic concentrations were recorded, and minimum alveolar anesthetic concentrations (MAC) were subsequently calculated and adjusted for age. The tHR increases was recorded and averaged for each group. The study groups did not differ by age, weight, end-tidal anesthetic concentrations, age-adjusted MAC, or heart rate at the time atropine was administered. After submental glossal injection (n = 11), tHR increases increase was fastest (3.0 +/- 1.1 min) and was significantly faster than that found with deltoid injection (n = 16; 4.4 +/- 1.1 min) or vastus lateralis injection (n = 8; 6.4 +/- 2.4 min) (P < 0.05 compared with both). The tHR increases also differed significantly between the deltoid and the vastus lateralis (P < 0.05). We conclude that submental glossal injection of atropine results in a more rapid onset of vagolysis than injection at traditional intramuscular sites.

Objective: To document the effect of administering artificial surfactant into the trachea, either by instillation or aerosolization, on acute lung injury experimentally induced with kerosene in sheep., Design: Randomized, prospective, controlled study., Setting: Research laboratory., Subjects: Sheep (n = 24), weighing 8.5 to 25.2 kg (average 16.6)., Interventions: In anesthetized, tracheally intubated sheep with pulmonary and femoral artery catheters inserted, lung injury was induced by instilling kerosene (0.3 mL/kg) into the trachea. After 15 mins of spontaneous breathing, mechanical ventilation was instituted with a uniform F10(2) and a tidal volume of 10 mL/kg. Sheep were then assigned randomly to one of four regimens as follows: exogenous surfactant or saline (5 mL/kg each) was administered as a bolus intratracheally or by aerosolization for 6 hrs., Measurements and Main Results: Arterial and mixed venous blood gases, pH, airway pressure, and static respiratory system compliance were measured and compared between aerosol saline and aerosol surfactant and between bolus saline and bolus surfactant. For all variables except static respiratory system compliance, the hourly rate of change from 15 mins, 1 hr, and 6 hrs after kerosene instillation was determined for each animal, and group rank sums of hourly rates of change were compared. For static respiratory system compliance, the slope of the pressure-volume curve with volumes of 100, 200, 300, 400, and 500 mL was computed for each animal at baseline and at 3 and 6 hrs after kerosene instillation. Group rank sums for static respiratory system compliance at 3 and 6 hrs were compared. Also, the 3- and 6-hr static respiratory system compliance values at each of the volumes were compared. With saline, six of eight sheep died; with surfactant, no sheep died (p = .001). When compared with saline at 15 mins, 1 hr, and 6 hrs after kerosene instillation, surfactant, regardless of whether administered by aerosol or bolus, significantly increased rate of change of arterial oxygen saturation, mixed venous oxygen saturation, and PO2., Conclusions: In the present animal study, artificial surfactant was an effective treatment for hydrocarbon aspiration. Aerosolized surfactant achieved results similar to instilled surfactant but at a lower total dose.

Objective: To assess the applicability of a new technology in neonates. Transtracheal Doppler and extravascular Doppler determinations of stroke volume and cardiac output were compared with thermodilution measurements at various states of volume loading in an animal model., Design: Prospective, descriptive study., Setting: Animal research laboratory at a university medical center., Subjects: Fourteen newly weaned piglets, weighing 2.8 to 6.5 kg., Interventions: Doppler probes were placed on the endotracheal tube tip (transtracheal Doppler) and directly on the aortic adventitia (extravascular Doppler). A 4-Fr thermodilution catheter was inserted in the pulmonary artery. Stroke volume and cardiac output determinations were recorded at baseline, after a 15-mL/kg volume load and after successive 15-mL/kg blood withdrawals to exsanguination or a systolic blood pressure of < 20 mm Hg., Measurements and Main Results: Transtracheal and extravascular Doppler measurements of cardiac output were not significantly different from thermodilution at any physiologic state. These techniques were able to measure stroke volumes and cardiac outputs at the low levels seen in severe hemorrhagic shock., Conclusions: Transtracheal Doppler and extravascular Doppler measurements of cardiac output compare favorably with thermodilution. These methods effectively followed trends from alterations in intravascular volume, even at very high heart rates and small stroke volumes. Transtracheal Doppler and extravascular Doppler should yield useful information in critically ill neonatal patients, where data regarding stroke volume and cardiac output may be useful in clinical management.

The authors set up a study to investigate the levels of stress experienced by dental students and the students' perceptions of the sources of stress. Levels of stress among students were found to be high, particularly during the first 2 years of dental school. Sources of stress included the practice of conservative dental surgery, dealing with administration and dealing with clinical demonstrators.

Topical formulations of tetracaine in vehicles of propylene glycol and saline are tested on human volunteers with standard occlusive, adhesive, transdermal patches. The effects of formulation composition, dose, and onset time are investigated. Dose-response studies indicate that the optimum formulation for the diffusion of tetracaine in vivo is 60% free base and 40% acid salt (w/w) in 40% propylene glycol and 60% saline (v/v). A concentration of 0.3 M [8.3% (w/v)] tetracaine is sufficient to reach the dose plateau. Time-response studies indicate that high concentrations of tetracaine in the optimum formulation [1.1 and 1.8 M, 30 and 50% (w/v), respectively] can produce statistically significant analgesia relative to a placebo after 45 min. Comparison of these in vivo data with earlier in vitro data indicate that the optimum formulation with regard to clinical studies is identical to that for in vitro diffusion through hairless mouse skin [60% free base and 40% acid salt (w/w) in 40% propylene glycol and 60% saline].

To evaluate decision-making factors of pediatric surgeons when faced with ethical dilemmas in a clinical setting, questionnaires were mailed to members of the Canadian Association of Paediatric Surgeons. The surgeons were asked to respond to scenarios regarding ethical dilemmas in the treatment of children. Fifty-one responses (57%) were computer analyzed based on chosen responses to the clinical dilemma and demographic factors such as age, sex, marital status, country of citizenship, religion, and "religiousness," a determination of religious conviction as viewed by the respondent. In addition, ethical convictions were sought regarding abortion, fetal research, AIDS, HIV testing, denial of medical care due to religious beliefs (Jehovah's Witness), and limitations in health care access for indigents. In general, respondents found it difficult to separate ethical guidelines for determining aggressive treatment--absolute value of life; best interests of the child; parental authority; and ability of the child to engage in social, intellectual, or emotional attachments (quality of life)--in the face of actual patient care issues. In fact, results of this survey indicate that the operating surgeon applies his/her medical knowledge and surgical "experience" to each individual case, incorporating his or her own ethical beliefs (in a respondent's words: "In the operating room, the surgeon must satisfy his own conscience in making decisions") while cognizant of legal guidelines for "standard care" ("Decisions would be based on personal experience, and what the local society believes to be right").(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: To determine the value of multimodality-evoked potential recordings in predicting outcome in comatose children., Design: Prospective series and literature review., Setting: Pediatric ICU in a university hospital., Patients: Forty-one children with a Glasgow Coma Scale score of less than 8, who were admitted to the pediatric ICU between 1984 and 1989., Interventions: Forty-one patients underwent brainstem auditory-evoked potential testing within 72 hrs of admission. Of these patients, 37 also had somatosensory-evoked potential testing at the same time. Four patients did not receive somatosensory-evoked potential testing for various nonmedical reasons., Measurements and Main Results: Multimodality-evoked potential recordings were used to predict outcome in these comatose children. Outcomes were categorized as bad (death or chronic vegetative state) or good (all other outcomes). Survivor outcomes were determined at discharge and on subsequent follow-up visits from 1 to 3 yrs later. There were no false pessimistic predictions, and two false optimistic predictions in this series. A comprehensive literature review of coma outcome prediction, using multimodality-evoked potential recordings, revealed 20 series with 982 additional patients in whom the predictive errors of false optimism and false pessimism could be determined. Five cases of false pessimism and 99 cases of false optimism were identified in the 982 additional patients. If neonates are excluded, the false pessimism number is reduced to three., Conclusions: A bad outcome can be reliably predicted using multimodality-evoked potential recordings with little chance of a false pessimistic prediction. The acceptable error of false optimism occurs frequently, since patients often die of progressive neurologic and nonneurologic problems that may or may not be present at the time of the evoked potential recordings. Thus, in comatose children, multimodality-evoked potential recordings are a useful adjunct to clinical examination and other diagnostic aids in predicting outcome and in making decisions regarding the degree of intervention to offer.

Acute cardiovascular collapse occurred in a 15-year-old girl during peritoneoscopic placement of a Tenckhoff catheter. The case demonstrates a potential complication of this procedure: air embolism. A review of the management and prevention of this problem is provided.

A recent study has shown a 77% incidence of tracheal aspiration in children (mean age 13.4 months) who are intubated with uncuffed endotracheal tubes. To determine both the incidence of such aspiration among premature infants and whether continuous positive airway pressure (CPAP) has any preventive effect, 20 tracheally intubated neonates were evaluated for the presence of tracheal aspiration of orally placed Evan's blue dye. The overall incidence of aspiration was 80%. Eighteen of these infants were tested during both 4 cm and 6 cm H2O continuous positive airway pressure, and the incidences of aspiration were 72% and 50%, respectively, which is not a statistically significant difference (P less than .17). Ten of these 18 patients were also studied when 2 cm H2O was applied and 60% aspirated. Among all infants who aspirated, compared with those who did not, there was a small but statistically significant decrease in transcutaneous PO2 (P less than .05) as well as an increase in respiratory (P less than .001) and pulse (P less than .01) rates. It is concluded that tracheally intubated neonates frequently aspirate and that clinically useful levels of continuous positive airway pressure are not likely to prevent aspiration.

Hydrocarbon aspiration is responsible for substantial morbidity and mortality in both children and domestic animals. To better understand the pathogenesis of hydrocarbon poisoning, we evaluated the effects of aspiration of 0.5 ml/kg of kerosene on various pulmonary and cardiovascular variables over a 4-hr period in a canine model. Heart rate and blood pressure decreased immediately after kerosene aspiration but returned to control values within 60 min. Respiratory rate and intrapulmonary shunting were increased and PaO2 was decreased for up to 4 hr after kerosene aspiration. PaCO2 increased and pH decreased immediately after aspiration but returned to baseline within 45 and 90 min, respectively. Intrapleural pressure became more negative after kerosene was aspirated, which suggests that total lung compliance was diminished. Kerosene aspiration resulted in severe and persistent intrapulmonary physiologic shunting, hypoxemia, bradycardia, and hypotension.

The natural frequencies, damping coefficients, and accuracies of umbilical artery catheters were determined. The damping coefficients for the 3.5, 5.0, and 8.0 French catheters were 0.40 +/- 0.04 (mean +/- SD), 0.42 +/- 0.05, and 0.19 +/- 0.02, respectively. The natural frequencies were 24.2 +/- 3.2 Hz (mean +/- SD), 18.4 +/- 3.5 Hz, and 26.8 +/- 2.9 Hz, respectively. Measurements obtained with 3.5 and 8.0 French catheters were within 6% of the reference pressure at all pressures and rates tested. With the 5.0 French catheter, however, error greater than 10% from the reference pressure occurred when the rate was 200 pulses per minute or greater and the applied maximum pressure was 100 mm Hg or more.