Transient decrease in PaCO(2) and asymmetric chest wall dynamics in early progressing pneumothorax

PURPOSE

Diagnosis of pneumothorax (PTX) in newborn infants has been reported as late. To explore diagnostic indices for early detection of progressing PTX, and offer explanations for delayed diagnoses.

METHODS

Progressing PTX was created in rabbits (2.3 ± 0.5 kg, n = 7) by injecting 1 ml/min of air into the pleural space. Hemodynamic parameters, tidal volume, EtCO(2), SpO(2), blood gas analyses and chest wall tidal displacements (TDi) on both sides of the chest were recorded.

RESULTS

(Mean ± SD): A decrease in SpO(2) below 90 % was detected only after 46.6 ± 11.3 min in six experiments. In contrary to the expected gradual increase of CO(2), there was a prolonged transient decrease of 14.2 ± 4.5 % in EtCO(2) (p < 0.01), and a similar decrease in PaCO(2) (p < 0.025). EtCO(2) returned back to baseline only after 55.2 ± 24.7 min, and continued to rise thereafter. The decrease in CO(2) was a mirror image of the 14.6 ± 5.3 % increase in tidal volume. The analysis of endotracheal flow and pressure dynamics revealed a paradoxical transient increase in the apparent compliance. Significant decrease in mean arterial blood pressure was observed after 46.2 ± 40.1 min. TDi provided the most sensitive and earliest sign of PTX, decreasing on the PTX side after 16.1 ± 7.2 min. The TDi progressively decreased faster and lower on the PTX side, thus enabling detection of asymmetric ventilation.

CONCLUSIONS

The counterintuitive transient prolonged decrease in CO(2) without changes in SpO(2) may explain the delay in diagnosis of PTX encountered in the clinical environment. An earlier indication of asymmetrically decreased ventilation on the affected side was achieved by monitoring the TDi.

A new method for continuous monitoring of chest wall movement to characterize hypoxemic episodes during HFOV

INTRODUCTION

Monitoring ventilated infants is difficult during high-frequency oscillatory ventilation (HFOV). This study tested the possible causes of hypoxemic episodes using a new method for monitoring chest wall movement during HFOV in newborn infants.

METHODS

Three miniature motion sensors were attached to both sides of the chest and to the epigastrium to measure the local tidal displacement (TDi) at each site. A >20% change in TDi was defined as deviation from baseline.

RESULTS

Eight premature infants (postmenstrual age 30.6 ± 2.6 weeks) were monitored during 10 sessions (32.6 h) that included 21 hypoxemic events. Three types of such events were recognized: decrease in TDi that preceded hypoxemia (n = 11), simultaneous decrease in TDi and SpO2 (n = 6), and decrease in SpO(2) without changes in TDi (n = 4). In the first group, decreases in TDi were detected 22.4 ± 18.7 min before hypoxemia, and were due to airway obstruction by secretions or decline in lung compliance. The second group resulted from apnea or severe abdominal contractions. In the third group, hypoxia appeared following a decrease in FiO2.

CONCLUSIONS

Monitoring TDi may enable early recognition of deteriorating ventilation during HFOV that eventually leads to hypoxemia. In about half of cases, hypoxemia is not due to slowly deteriorating ventilation.

Benefits of high frequency oscillatory ventilation for premature infants

BACKGROUND

High frequency oscillatoryventilation based on optimal lung volume strategy is one of the accepted modes of ventilatory support for respiratory distress syndrome in very low birth weight infants. In 1999 itwas introduced in our unit as the primary ventilation modality for RDS.

OBJECTIVES

To evaluate if the shift to HFOV influenced the outcome of ventilated VLBW infants in the neonatal intensive care unit of Carmel Medical Center.

METHODS

Data were obtained from the medical charts of VLBW infants born at Carmel Medical Center, and late mortality data from the Israel Ministry of Internal Affairs records. A retrospective analysis and a comparison with a historical control group ventilated by the conventional method were performed.

RESULTS

A total of 232 VLBW infants with RDS were mechanically ventilated during the period 1995 to 2003: 120 were ventilated using HFOV during 1999-2003 and 102 infants using CV during 1995-1999. The mean gestational age of survivors was 27.4 +/- 2 weeks in the HFOV group and 28.4 +/- 2 in the conventional ventilation group (P = 0.03). The sub-sample of infants with birth weight < 1000 g ventilated with HFOV showed higher survival rates than the infants in the conventional ventilation group, 53 vs. 25 (64.6% vs. 44.6%) respectively (P < 0.05). A trend for lower incidence of pulmonary interstitial emphysema was observed in the HFOV group.

CONCLUSIONS

The introduction of HFOV based on optimal lung volume strategy proved to be an efficient and safe method of ventilation support for VLBW infants in our unit.

Subpleural microvascular flow velocities and shear rates in normal and septic mechanically ventilated rats

Changes in pulmonary microhemodynamics are important variables in a large variety of pathological processes. We used in vivo fluorescent videomicroscopy of the subpleural microvasculature in mechanically ventilated rats to directly monitor microvascular flow velocity (FV) and shear rate in pulmonary arterioles, capillaries, and venules in healthy rats and in septic rats 20 h after cecal ligation and puncture (CLP). Observations were made through a small thoracotomy after injection of fluorescent microspheres (D = 1 microm) into the systemic circulation. The FVs were calculated off-line by frame-by-frame measurements of the distance covered by individual microspheres per unit of time. In healthy rats, inspiratory FV were 1322 +/- 142 microm/s in subpleural arterioles and 599 +/- 25 microm/s in capillaries. The highest FV was found in venules (1552 +/- 132 microm/s). The calculated shear rates were 547 +/- 62/s in arterioles and 619 +/- 19/s in capillaries. The highest shear rates were detected in venules (677 +/- 59/s). No significant changes in FV and shear rates were observed throughout the 1-h observation period in any of the microvascular compartments. Pulmonary microvascular FV and shear rates found in sham-operated rats in the CLP experiments were not significantly different from values of healthy rats. The CLP caused a significant increase in leukocyte sequestration in the lungs and a mean of 27% to 34% decrease in FV in all sections of the pulmonary microvasculature (P < 0.001 in capillaries and P < 0.05 in venules). Also, CLP caused a 23% decrease in capillary shear rate that reached only borderline statistical significance (P < 0.06) and a significant 35% decrease in mean shear rate in venules (P < 0.05). Fluorescent videomicroscopy is offered as a stable and reproducible method for in vivo determinations of pulmonary microhemodynamics in clinically relevant models of sepsis.

The anuric preterm newborn infant with a normal renal ultrasound: a diagnostic and ethical challenge

Diagnosis and treatment of an anuric premature infant with severe respiratory compromise and a normal renal ultrasound (US), is a difficult task that requires a multidisciplinary approach. A 29-week gestation premature male infant, born after 5 weeks of worsening oligohydramnios, was ventilated for respiratory distress and remained anuric. Intensive clinical investigations and pediatric nephrology consultation that predicted very poor prognosis were followed by progressive renal failure, electrolyte imbalance, respiratory failure, ventricular arrhythmia, and finally cardiac arrest and death on day 5. In view of the predicted poor outcome, and after discussion with the parents, a decision was made not to start peritoneal dialysis (PD), and to offer only palliative therapy, with comfort care alone. Pre and postnatal diagnosis lead, in this case, to an ethical challenge that focuses on the question of futility.

A model for second-trimester Down syndrome sonographic screening based on facial landmarks and digit length measurement

OBJECTIVE

To determine whether Down syndrome can be detected by combining measurements of fetal nasal bone (NB) length, prenasal thickness (PT) and digits 2 and 3 of the hand.

METHODS

Two hundred and fifty-four normal and 25 Down-syndrome fetuses were scanned between 15 and 33 weeks' gestation. Physicians performing the scans were not blinded to the fetal karyotype. Both PT and NB were measured in a mid-sagittal plane. For PT measurement calipers were placed between the frontonasal angle and the outer skin edge. Digits 2 and 3 of one hand were also measured. The results (except for PT/NB ratio) were expressed in multiples of the normal gestation-specific median (MoM). A logistic regression model was used to estimate the odds of the fetus having Down syndrome given different combinations of NB, PT, PT/NB ratio, and digits 2 and 3 measurements. The odds were used to calculate the risk of Down syndrome for each pregnant woman from her age and measurements.

RESULTS

The median PT MoM for unaffected fetuses and Down-syndrome fetuses was 1.12 vs. 1.35 (P < 0.0001). The median NB MoM for unaffected and Down-syndrome fetuses was 1.03 vs. 0.81 (P < 0.001) and the PT/NB ratio MoM for unaffected and Down-syndrome fetuses was 0.63 vs. 0.96 (P < 0.001). The respective median MoM values for digits 2 and 3 of the Down-syndrome fetuses were significantly smaller (0.81 vs. 0.93 and 0.89 vs. 0.95, respectively, P = 0.003). Only the PT/NB ratio and digit 2 were finally included in the logistic regression equation. Using a 1 in 200 risk cut-off, the observed sensitivity and false-positive rate were 76% and 6.7%, respectively.

CONCLUSION

Combining the PT/NB ratio and digit 2 measurements yielded a promising screening detection rate. Confirmation of our findings in a prospective study is needed before the method can be used clinically.

[Trends of electronic publishing in medicine and life sciences]

Scientific publication in the electronic media is gaining popularity in academic libraries, research institutions and commercial organizations. The electronic journal may shorten the processes of writing and publication, decrease publication and distribution costs, and enable access from any location in the world. Electronic publications have unique advantages: it is possible to search them, to create hyperlinks to references and footnotes, as well as to information on the web and to include graphics and photographs at a very low cost. Audio, video and tri-dimensional images may also be included. Electronic publishing may also speed up review and publication processes and enable the writer to receive immediate feedback through the web. However, in spite of the advantages, there are certain points that must be considered: accessibility to previously published material is not guaranteed as databases are not always stable and coverage may change without notice. In addition, the price that commercial publishers charge for their services may be very high or be subject to the purchase of a packaged deal that may include unwanted databases. Many issues of copyright and the use of published material are not yet finalized. In this review we discuss the advantages and disadvantages of the electronic scientific publication, the feasibility of keeping appropriate quality and peer-review process, the stability and accessibility of databases managed by the publishers and the acceptance of the electronic format by scientists and clinicians.

An automated method for analysis of flow characteristics of circulating particles from in vivo video microscopy

The behavior of white and red blood cells, platelets, and circulating injected particles is one of the most studied areas of physiology. Most methods used to analyze the circulatory patterns of cells are time consuming. We describe a system named CellTrack, designed for fully automated tracking of circulating cells and micro-particles and retrieval of their behavioral characteristics. The task of automated blood cell tracking in vessels from in vivo video is particularly challenging because of the blood cells' nonrigid shapes, the instability inherent in in vivo videos, the abundance of moving objects and their frequent superposition. To tackle this, the CellTrack system operates on two levels: first, a global processing module extracts vessel borders and center lines based on color and temporal patterns. This enables the computation of the approximate direction of the blood flow in each vessel. Second, a local processing module extracts the locations and velocities of circulating cells. This is performed by artificial neural network classifiers that are designed to detect specific types of blood cells and micro-particles. The motion correspondence problem is then resolved by a novel algorithm that incorporates both the local and the global information. The system has been tested on a series of in vivo color video recordings of rat mesentery. Our results show that the synergy between the global and local information enables CellTrack to overcome many of the difficulties inherent in tracking methods that rely solely on local information. A comparison was made between manual measurements and the automatically extracted measurements of leukocytes and fluorescent microspheres circulatory velocities. This comparison revealed an accuracy of 97%. CellTrack also enabled a much larger volume of sampling in a fraction of time compared to the manual measurements. All these results suggest that our method can in fact constitute a reliable replacement for manual extraction of blood flow characteristics from in vivo videos.

Effects of inhaled nitric oxide on lung injury after intestinal ischemia-reperfusion in rats

Splanchnic ischemia/reperfusion (I/R) induces a systemic inflammatory response with acute lung injury. Impaired production of endothelial nitric oxide (NO) plays a key role in this process. We evaluated the effects of early treatment with inhaled NO (iNO) on lung microcirculatory inflammatory changes during splanchnic I/R. I/R was induced in rats by occlusion of the superior mesenteric artery (SMA; 40 min) and reperfusion (90 min). Four groups were studied: Control, anesthesia only; Sham, all surgical procedures without I/R, ventilated with air; Air, SMA I/R, ventilation with air; and NO, SMA I/R, ventilation with NO (20 ppm) starting 10 min before reperfusion. Intravital video microscopy was used to monitor pulmonary macromolecular flux and capillary flow velocity (CFV). Leukocyte infiltration was determined by morphometry. SMA I/R decreased mean arterial blood pressure, capillary CFV (P < 0.01), and shear rate (P < 0.01), and increased pulmonary macromolecular leak by 138% +/- 8% (P < 0.001). iNO markedly attenuated the increase in macromolecular leak (P < 0.01), blunted the decrease in capillary CFV (P < 0.05) and shear rate (P < 0.05), and prevented the increase in leukocyte infiltration of the lungs after SMA I/R (P < 0.05). The direct, real-time, in vivo data suggest that early institution of low-dose iNO therapy effectively ameliorates the acute remote pulmonary inflammatory response after splanchnic I/R.

Effects of hyperoxia on local and remote microcirculatory inflammatory response after splanchnic ischemia and reperfusion

Splanchnic ischemia-reperfusion (I/R) causes tissue hypoxia that triggers local and systemic microcirculatory inflammatory responses. We evaluated the effects of hyperoxia in I/R induced by 40-min superior mesenteric artery (SMA) occlusion and 120-min reperfusion in four groups of rats: 1) control (anesthesia only), 2) sham operated (all surgical procedures without vascular occlusion; air ventilation), 3) SMA I/R and air, 4) SMA I/R and 100% oxygen ventilation started 10 min before reperfusion. Leukocyte rolling and adhesion in mesenteric microvessels, pulmonary microvascular blood flow velocity (BFV), and macromolecular (FITC-albumin) flux into lungs were monitored by intravital videomicroscopy. We also determined pulmonary leukocyte infiltration. SMA I/R caused marked decreases in mean arterial blood pressure (MABP) and blood flow to the splanchnic and hindquarters vascular beds and pulmonary BFV and shear rates, followed by extensive increase in leukocyte rolling and adhesion and plugging of >50% of the mesenteric microvasculature. SMA I/R also caused marked increase in pulmonary sequestration of leukocytes and macromolecular leak with concomitant decrease in circulating leukocytes. Inhalation of 100% oxygen maintained MABP at significantly higher values (P < 0.001) but did not change regional blood flows. Oxygen therapy attenuated the increase in mesenteric leukocyte rolling and adherence (P < 0.0001) and maintained microvascular patency at values not significantly different from sham-operated animals. Hyperoxia also attenuated the decrease in pulmonary capillary BFV and shear rates, reduced leukocyte infiltration in the lungs (P < 0.001), and prevented the increase in pulmonary macromolecular leak (P < 0.001), maintaining it at values not different from sham-operated animals. The data suggest that beneficial effects of normobaric hyperoxia in splanchnic I/R are mediated by attenuation of both local and remote inflammatory microvascular responses.

Effect of maternal tocolysis on the incidence of severe periventricular/intraventricular haemorrhage in very low birthweight infants

AIM

To examine the relation between grade III-IV periventricular/intraventricular haemorrhage (PVH/IVH) and antenatal exposure to tocolytic treatment in very low birthweight (VLBW) premature infants.

STUDY DESIGN

The study population consisted of 2794 infants from the Israel National VLBW Infant Database, of gestational age 24-32 weeks, who had a cranial ultrasound examination during the first 28 days of life. Infants of mothers with pregnancy induced hypertension or those exposed to more than one tocolytic drug were excluded. Of the 2794 infants, 2013 (72%) had not been exposed to tocolysis and 781 (28%) had been exposed to a single tocolytic agent. To evaluate the effect of tocolysis and confounding variables on grade III-IV PVH/IVH, the chi(2) test, univariate analysis, and a logistic regression model were used.

RESULTS

Of the 781 infants (28%) exposed to tocolysis, 341 (12.2%) were exposed to magnesium sulphate, 263 (9.4%) to ritodrine, and 177 (6.3%) to indomethacin. The overall incidence of grade III-IV PVH/IVH was 13.4%. In the multivariate logistic regression analysis, the following factors were related significantly and independently to grade III-IV PVH/IVH: no prenatal steroid treatment, low gestational age, one minute Apgar score 0-3, respiratory distress syndrome, patent ductus arteriosus, mechanical ventilation, and pneumothorax. Infants exposed to ritodrine tocolysis (but not to the other tocolytic drugs) were at significantly lower risk of grade III-IV PVH/IVH after adjustment for other variables (odds ratio = 0.3; 95% confidence interval 0.2 to 0.6).

CONCLUSION

This study suggests that antenatal exposure of VLBW infants to ritodrine tocolysis, in contrast with tocolysis induced by magnesium sulphate or indomethacin, was associated with a lower incidence of grade III-IV PVH/IVH.

The effect of glucocorticoids on the expression of L-selectin on polymorphonuclear leukocyte

When active bone marrow release is induced by inflammatory stimuli, it is associated with an increase in L-selectin expression on circulating polymorphonuclear leukocyte (PMN). This contrasts sharply with glucocorticoid-induced granulocytosis that is associated with decreased L-selectin expression on PMN. The present study was designed to determine if the reduced L-selectin expression observed after glucocorticoid treatment is the result of suppression of L-selectin synthesis in the bone marrow. New Zealand white rabbits treated with dexamethasone (2.0 mg/kg, a single dose intravenously) were shown to have decreased L-selectin expression on circulating PMN 12 to 24 hours after treatment (P <.01) with a return to baseline levels by 48 hours. When dexamethasone was administered 48 hours after the bone marrow PMN were pulse labeled with the thymidine analogue, 5'-bromo-2'-deoxyuridine (BrdU), L-selectin expression on BrdU-labeled PMN released from the bone marrow was decreased (P <.01). Dexamethasone decreased L-selectin expression on segmented PMN in the bone marrow (P <.05) but not on PMN already in the circulation. We conclude that glucocorticoids decrease L-selectin expression on circulating PMN by downregulating L-selectin expression in the maturation pool of bone marrow and speculate that this is an important glucocorticoid effect that influences the recruitment of PMN into inflammatory sites.

Effect of vitamin K1 on glucose-6-phosphate dehydrogenase deficient neonatal erythrocytes in vitro

AIM

To determine whether vitamin K1, which is routinely administered to neonates, could act as an exogenous oxidising agent and be partly responsible for haemolysis in glucose-6-phosphat-dehydrogenase (G-6-PD).

METHODS

G-6-PD deficient (n = 7) and control (n = 10) umbilical cord blood red blood cells were incubated in vitro with a vitamin K1 preparation (Konakion). Two concentrations of Vitamin K1 were used, both higher than that of expected serum concentrations, following routine injection of 1 mg vitamin K1. Concentrations of reduced glutathione (GSH) and methaemoglobin, indicators of oxidative red blood cell damage, were determined before and after incubation, and the mean percentage change from baseline calculated.

RESULTS

Values (mean (SD)) for GSH, at baseline, and after incubation with vitamin K1 at concentrations of 44 and 444 microM, respectively, and percentage change from baseline (mean (SD)) were 1.97 + 0.31 mumol/g haemoglobin, 1.89 +/- 0.44 mumol/g (-4.3 +/- 13.1%), and 1.69 +/- 0.41 mumol/g (-14.5 +/- 9.3%) for the G-6-PD deficient red blood cells, and 2.27 +/- 0.31 mumol/g haemoglobin, 2.09 +/- 0.56 mumol/g (-7.2 +/- 23.2%), and 2.12 +/- 0.38 mumol/g (-6.0 + 14.1%) for the control cells. For methaemoglobin (percentage of total haemoglobin), the corresponding values were 2.01 +/- 0.53%, 1.93 +/- 0.37% (-0.6 +/- 17.4%) and 2.06 +/- 0.43% (5.7 +/- 14.2%) for the G-6-PD deficient red blood cells, and 1.56 +/- 0.74%, 1.70 +/- 0.78% (12.7 +/- 21.9%), and 1.78 +/- 0.71% (20.6 +/- 26.8%) for the control red blood cells. None of the corresponding percentage changes from baseline was significantly different when G-6-PD deficient and control red blood cells were compared.

CONCLUSIONS

These findings suggest that G-6-PD deficient red blood cells are not at increased risk of oxidative damage from vitamin K1.

Hyperbaric oxygen therapy in the pediatric patient: the experience of the Israel Naval Medical Institute

The pediatric patient is to be found in hyperbaric facilities throughout the world, receiving hyperbaric oxygen (HBO) therapy for both life-threatening and chronic diseases.

OBJECTIVE

To review the experience accumulated at the Israel Naval Medical Institute in the treatment of pediatric patients.

DESIGN

A retrospective analysis and review of all records of patients younger than age 18 years.

RESULTS

Between 1980 and 1997, 139 pediatric patients age 2 months to 18 years (mean, 7.7 years) received HBO treatment at the Israel Naval Medical Institute. Of the children, 111 (79%) suffered from acute carbon monoxide (CO) poisoning; 13 (9.2%) were treated after crush injury, traumatic ischemia, or compartment syndrome; 4 (2.8%) had clostridial myonecrosis; 1 (0.7%) had necrotizing fasciitis; 5 (3.6%) had refractory osteomyelitis; 2 (1.4%) had suffered massive air embolism; 2 (1.4%) had purpura fulminans; and 1 (0.7%) suffered from decompression sickness. Outcome, judged by neurologic sequelae, mortality, and extent of soft tissue loss and limb amputation, was favorable in 129 patients (93%). Two patients (1.4%) died, 1 as a result of CO poisoning and the other, gas gangrene; 2 of the patients in the CO group (1.4%) remained with neurologic sequelae, and 6 patients in the acute traumatic ischemia group (4.3%) underwent limb amputation.

CONCLUSIONS

We had a favorable experience with 129 of a total 139 pediatric patients treated at our facility for the indications listed. A basic knowledge of HBO therapy is needed to refer the pediatric patient for treatment when indicated. The needs of the pediatric patient, especially the critically ill, require specific skills and equipment inside the hyperbaric chamber. Close collaboration between the pediatrician and the hyperbaric medicine physician is essential to ensure adequate care for infants and children.

L-selectin expression on polymorphonuclear leukocytes and monocytes in premature infants: reduced expression after dexamethasone treatment for bronchopulmonary dysplasia

We examined the effect of dexamethasone on the expression of the adhesion molecule L-selectin on circulating polymorphonuclear leukocytes (PMLs) and monocytes from premature infants with bronchopulmonary dysplasia (BPD). Nineteen infants who received dexamethasone (Dex group) and 28 who did not receive dexamethasone (no Dex group) were studied. L-selectin expression, measured as mean fluorescence intensity, was lower on circulating PMLs (5.7 +/- 0.6 vs 10.6 +/- 0.7, p < 0.001) and monocytes (7.9 +/- 0.9 vs 12.5 +/- 0.9, p < 0.02) isolated from those who had received dexamethasone. Because L-selectin is important for the recruitment of PMLs to inflammatory foci in the lungs, we speculate that one of the mechanisms by which dexamethasone reduces inflammation in BPD is by impairing the ability of leukocytes to migrate into the BPD lesions.

Bone marrow infusion in adults

OBJECTIVE

To asses the feasibility and success rate of vascular access through intraosseous infusions in adults, in elective and emergency situations using a novel, automatic device, the bone injection gun.

DESIGN

A prospective, nonrandomized trial.

MATERIALS AND METHODS

Two groups of patients were prospectively selected over an 11-month period. Group 1: Adult patients with recent closed long bone fractures, who underwent orthopedic surgery to upper and lower limbs and needed regional anesthesia. Group 2: Adult patients who required emergency or semiemergency vascular access, in whom intravenous central or peripheral cannulation could not be established within a reasonable period of time.

MAIN RESULTS

Fifty adult patients, aged 27 through 78 years, underwent the procedure, which was universally successful. In group 1, n = 31 patients; in group 2 (n = 19), 12 patients had multiple injuries, and seven underwent emergency resuscitation. In 76% of the cases, the needle was inserted into the area of the tibial tuberosity; in the reminder of the cases, the needle was inserted at the distal end of the radial bone and into the lateral or the medial malleolus. The success rate for an adequate insertion was 100% in this group of patients. No complications from the procedure were observed in this series.

CONCLUSIONS

This study emphasizes the importance and feasibility of the intraosseous route for infusion of fluids and medications in emergency situations in adults. The use of an impact, high speed automatic needle insertion device provides a higher success rate of vascular access via the intraosseal route in adult patients.