Lung vascular responses and VA/Q matching after chronic hypoxia in neonatal piglets

We hypothesized that exposure of neonatal swine to chronic alveolar hypoxia (CH) would cause increased PVR, blunt acute hypoxic vasoconstriction, and increase VA/Q mismatch. After exposure to either normobaric alveolar hypoxia (FIO2 = 0.10) or room air for 2 weeks, animals were anesthetized and ventilated first with room air and then with hypoxic gas (FIO2 = 0.12). PVR, and pressure-flow (P/Q) relations were measured between 15-100% of baseline cardiac output. VA/Q matching was measured by the multiple inert gas elimination technique. During room air breathing, the mean PVR and P/Q slope in the CH animals was significantly greater than in the control (C) animals. P/Q intercepts were similar and near the origin for both groups. The absolute PVR and P/Q slope were greater for CH compared to C animals during acute alveolar hypoxia. The fractional increase in PVR and P/Q slope in the response to acute hypoxia was similar for both groups. PaO2, intrapulmonary shunt, and SDQp (an index of VA/Q heterogeneity) were similar for both groups. We conclude that CH in neonatal swine causes pulmonary hypertension, but does not attenuate acute hypoxic pulmonary vasoconstriction, nor VA/Q matching.

Group B streptococci invade endothelial cells: type III capsular polysaccharide attenuates invasion

Group B streptococci (GBS) are the most common cause of neonatal sepsis and pneumonia. The pathogenesis of GBS disease is not completely defined. GBS-induced endothelial cell injury is suggested by histological findings at autopsy and in animal studies. We hypothesized that (i) type III GBS (COH-1) invade and injure human umbilical vein endothelial (HUVE) cells and (ii) isogenic mutations in GBS capsule synthesis would influence HUVE invasion. Confluent HUVE monolayers were infected for 0.5, 2, or 6 h. Media with penicillin plus gentamicin were added and incubated for 2 h to kill extracellular bacteria. Cells were washed and lysed, and the number of live intracellular bacteria was determined by plate counting. COH-1 invaded HUVE cells in a time-dependent manner at levels 1,000-fold higher than those of the noninvasive Escherichia coli strain but significantly lower than those of Staphylococcus aureus. There was no evidence for net intracellular replication of GBS within HUVE cells. COH-1 infection of HUVE cells caused the release of lactate dehydrogenase activity. GBS invasion was inhibited by cytochalasin D in a dose-dependent manner; GBS-induced lactate dehydrogenase release was attenuated by cytochalasin D. The isogenic strains COH 1-11, devoid of capsular sialic acid, and COH 1-13, devoid of all type III capsule, invaded HUVE cells three- to fivefold more than the parent COH-1 strain. The type III capsular polysaccharide and particularly the capsular sialic acid attenuate GBS invasion of HUVE cells. Electron micrographs of lung tissue from a GBS-infected newborn Macaca nemestrina also showed GBS within capillary endothelial cells. We conclude that endothelial cell invasion and injury are potential mechanisms in the pathogenesis of GBS disease.

Effect of group B streptococcal sepsis on diaphragmatic function in young piglets

Recent studies indicate that diaphragmatic pressure generation (Pdi) is impaired by bacterial infection. However, group B streptococcus (GBS) had no effect on Pdi when infused into 4-wk-old piglets. As responsiveness to GBS is age-dependent, we therefore studied the acute effect of GBS infusion on Pdi, using a younger, 2-wk-old piglet model. Using trans-Pdi with phrenic nerve stimulation, we studied the effect of continuous GBS infusion in seven anesthetized, spontaneously breathing 2-wk-old piglets. Pdi was measured under baseline conditions (50% O2/50% N2) and at 1, 2, and 4 h of GBS infusion. GBS was infused at a rate which caused a doubling of the pulmonary artery pressure but which avoided hypotension or acidosis--both of which can decrease Pdi. In addition, the piglets were kept hyperoxic [PaO2 > 13.3 kPa (100 torr)], and no piglet with hypercapnia [PaCO2 > 8.7 kPa (65 torr)] was included, as hypoxia and hypercapnia can also cause respiratory muscle dysfunction. For the GBS group, diaphragmatic contractility declined significantly by 1 h at 30-, 50-, and 100-Hz stimulation frequency and, by 2 h, was significantly decreased at all frequencies. We conclude that 2-wk-old piglets, in contrast to 4-wk-old piglets, demonstrate a decline in Pdi during GBS infusion. These data demonstrate an age-related response to GBS in the piglet.(ABSTRACT TRUNCATED AT 250 WORDS)

Group B streptococcal sepsis in piglets: effect of combined pentoxifylline and indomethacin pretreatment

Group B streptococcus (GBS), a common neonatal gram-positive pathogen, causes similar pathophysiology in human newborns and neonatal animal models of sepsis. Animal models of GBS sepsis demonstrate a two-phase response: 1) an acute phase (less than 1 h) of increased pulmonary artery pressure (Ppa) and reduced arterial oxygen pressure (PaO2) that is associated with increased serum thromboxane B2 (TxB2) and 2) a late phase (2-4 h) of persistently increased Ppa and reduced PaO2, reduced systemic arterial pressure, and progressive fall in cardiac output that is associated with increased serum TxB2, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and tumor necrosis factor-alpha (TNF alpha). We hypothesized that pretreatment of piglets with both pentoxifylline (PTF), an inhibitor of TNF alpha production and activity, and indomethacin (INDO) would 1) inhibit GBS-induced TxB2, 6-keto-PGF1 alpha, and TNF alpha and 2) prevent both the acute- and late-phase physiologic responses of GBS sepsis. Combined PTF and INDO pretreatment of anesthetized, mechanically ventilated piglets infused with GBS (1.25 x 10(9) colony forming units/kg/h) for 4 h prevented GBS-induced increases in Ppa at 1 h (GBS + PTF + INDO: 1.8 +/- 0.07 kPa versus GBS alone: 4.7 +/- 0.1 kPa) and markedly attenuated increases in Ppa at 4 h (GBS + PTF + INDO: 2.1 +/- 0.1 kPa versus GBS alone: 4.4 +/- 0.1 kPa).(ABSTRACT TRUNCATED AT 250 WORDS)

Group B streptococcus has no effect on piglet diaphragmatic force generation

Recent studies indicate that diaphragmatic contractility is adversely affected by bacterial infection. Using transdiaphragmatic pressure (Pdi) with phrenic nerve stimulation, the effect of continuous Group B Streptococcus (GBS) infusion on diaphragmatic force output was studied in seven anesthetized, spontaneously breathing 1-month old piglets. Pdi was measured under baseline condition (50% O2/50% N2) and at 1, 2, and 4 h of GBS infusion. The GBS was infused at a level that caused a doubling of the pulmonary artery pressure and a 32% decrease in cardiac output but which avoided hypotension or acidosis--both of which can decrease diaphragmatic contractility. In addition, the piglets were kept hyperoxic (PaO2 greater than 100) and no piglet with hypercapnia (PaCO2 greater than 65) was studied, as hypoxia and hypercapnia also can cause respiratory muscle dysfunction. Pdi in response to phrenic nerve stimulation did not change during GBS infusion. We conclude that GBS infusion, in the absence of hypotension, hypercapnia, hypoxia, or acidosis, has no effect on diaphragmatic force generation in the piglet.

Effect of pentoxifylline on cytokine- and eicosanoid-induced acute pulmonary hypertension in piglets

The methylxanthine derivative pentoxifylline (PTF) demonstrates vasodilatory properties in vivo. We tested the hypothesis that PTF infusion would blunt or inhibit tumor necrosis factor-alpha (TNF alpha)-induced and U46,619-induced increases in mean pulmonary artery pressure and pulmonary vascular resistance (PVR) in the neonatal piglet and would do so by altering production of eicosanoid vasoactive mediators. Anesthetized, paralyzed piglets (age 10-29 d) were randomized and treated with a 30-min infusion of TNF alpha alone (n = 13 animals), with a combination of TNF alpha plus pretreatment and continuous infusion with PTF (n = 6), or with a combination of U46,619 for 30 min plus pretreatment and continuous infusion of PTF (n = 5). There was no difference in pulmonary or systemic hemodynamic indices between the three groups at baseline. PVR was significantly elevated at 15 min and at 2 h in the TNF alpha-only group. The TNF alpha-induced rise in mean pulmonary artery pressure and PVR was inhibited by the PTF until 2 h, by which time PVR was elevated above baseline and was comparable to the value found in animals treated with only TNF alpha. PTF produced no inhibition in the U46,619-induced elevation of PVR during the 30-min simultaneous treatment. In the PTF + TNF alpha group, mean systemic blood pressure declined to 50% of baseline value (p less than 0.02) by 2 h of age. No significant decline was noted in mean systemic arterial pressure of the TNF alpha-only or the U46,619-treated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Group B streptococcus induces tumor necrosis factor in neonatal piglets. Effect of the tumor necrosis factor inhibitor pentoxifylline on hemodynamics and gas exchange

Group B streptococcus (GBS), a common neonatal gram-positive pathogen, causes similar pathophysiologic features in human newborns and neonatal animal models of sepsis. Previous reports suggest that mediators in addition to TxA2 and PGI2 contribute to the late effects of GBS infusion (2 to 4 h), which include persistent increases in Ppa, hypoxemia, systemic hypotension, and a progressive fall in CO. Tumor necrosis factor (TNF) infusion in animals produces several of the late GBS effects. We hypothesized that GBS causes increased serum TNF levels 2 to 4 h into infusion in neonatal piglets. We also postulated that the TNF inhibitor, pentoxifylline (PTF), would attenuate both GBS-induced TNF production and late GBS effects. In piglets infused with 1.25 x 10(9) cfu/kg/h of GBS, serum TNF levels (pg/ml, ELISA assay) significantly increased at 2 h (231 +/- 41) and at 4 h (1,047 +/- 290, n = 9). In piglets infused with concomitant GBS + PTF, serum TNF levels at 4 h (208 +/- 39, n = 8) were reduced compared to GBS alone piglets (p less than 0.02). Control piglets infused with 0.9% saline or PTF alone for 4 h had no detectable serum TNF (less than 35). GBS alone and GBS + PTF infusion caused similar increases in serum TxB2 levels at 1, 2, and 4 h. Serum 6-keto-PGF1 alpha levels (pg/0.1 ml) significantly increased at 4 h (85 +/- 18) with GBS alone, and were more elevated at 4 h (306 +/- 75) with GBS + PTF infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory mechanics of the piglet during the first month of life

Piglets at 3, 14, and 30 days of age were studied to assess the postnatal changes in lung, chestwall, and total respiratory system compliance associated with normal growth. Static deflation compliance of the lung and total respiratory system increased significantly with age; there was no change in chestwall compliance. When normalized for body weight or lung volume, all measures of compliance tended to decrease with postnatal age. Measures of lung and chestwall compliance obtained with an end-inspiratory occlusion technique were less than the static compliance measures, but demonstrated the same relative changes with postnatal maturation. Chestwall compliance at 3 days of age was only 1.3 times greater than lung compliance and there was no significant change in this ratio with postnatal age. In contrast to the trend for the human infant, the piglet's chestwall at 3 days of age is stiff relative to the lung and does not become stiffer with age over the first 4 weeks of life.

Lung function in children following empyema

Spirometry was performed and response to exercise was measured in 15 children following recovery from empyema to evaluate the impact of pleural infection on subsequent lung function. Seven children underwent chest tube drainage; eight did not. The two groups were similar in age (mean +/- SD, 6 +/- 5 years), sex distribution, bacterial pathogen-producing empyema, and age at follow-up evaluation (12 +/- 5 years). Only one child reported recurrent respiratory symptoms. No child had restrictive spirometric changes (total lung capacity, less than 80%; vital capacity, less than 80% predicted) but seven of 15 had a reduced forced expiratory volume in 1 second (less than 80% predicted) or forced expiratory flow during the middle half of the vital capacity (less than 75% predicted), suggesting mild airway obstruction. No child demonstrated reduced exercise tolerance due to restrictive ventilatory limitations. Mild obstructive abnormalities in lung function were identified with equal frequency in children treated with and without chest tube drainage.

Tumor necrosis factor-induced neonatal pulmonary hypertension: effects of dazmegrel pretreatment

The endogenously produced cytokine, tumor necrosis factor-alpha (TNF-alpha), has been shown in adult animal models to be associated with many of the pathophysiologic effects of sepsis, including systemic hypotension and hemorrhagic necrosis. TNF-alpha can induce the release of various vasoactive arachidonic acid metabolites, suggesting that TNF-alpha may act either directly or via intermediary substances in producing its effects. The pathophysiologic role of TNF-alpha in neonatal sepsis, especially its potential effect on pulmonary vascular tone, is presently unknown. To assess the role of TNF-alpha in neonatal sepsis, 19 piglets (19 +/- 5 d old) were anesthetized, intubated, paralyzed, mechanically ventilated, and catheterized to assess pulmonary and systemic vascular hemodynamics and pulmonary gas exchange. The multiple inert gas elimination technique was used to assess ventilation perfusion matching. A 30-min infusion of human recombinant TNF-alpha (250 micrograms/kg total dose) was administered to animals pretreated with either 10 mg/kg dazmegrel, a thromboxane synthase inhibitor (n = 9) or placebo (n = 10). TNF-alpha alone induced a prompt and sustained rise in pulmonary arterial pressure and pulmonary vascular resistance that continued at least for 2 h after onset of the infusion. In contrast, the animals pretreated with dazmegrel demonstrated no rise in pulmonary vascular resistance until 2 h after the onset of the infusion. Neither group of animals demonstrated a significant decline in arterial PO2 or evidence from inert gas analysis of VA/Q mismatching or increase in intrapulmonary shunt.(ABSTRACT TRUNCATED AT 250 WORDS)

Varicella outbreaks in Army recruits from Puerto Rico. Varicella susceptibility in a population from the tropics

Two outbreaks of varicella consisting of a total of 105 cases occurred in a highly varicella-susceptible population of young adult Army recruits from Puerto Rico enrolled in the Defense Language Institute in San Antonio, Tex, between October 1986 and November 1987. Epidemiologic investigation found a significantly higher risk for enlisted recruits housed in open barracks than for officers housed in private rooms. The attack rate in the first outbreak was 30%, with an estimated attack rate of 71% among susceptible persons. Serologic testing of 810 adult recruits from Puerto Rico for varicella-zoster antibody by means of an enzyme-linked immunosorbent assay procedure found 42% to be seronegative, with no significant difference by sex. The enzyme-linked immunosorbent assay test had a positive predictive value for absence of disease development of 95% in the second outbreak. Serologic test results were successfully used as part of the outbreak control strategy, with a resultant decrease in attack rates to 19% overall and 30% among susceptible persons in the second outbreak. Uniquely susceptible adult populations placed in conditions with high likelihood of infection on exposure are potential candidates for the varicella vaccine after its licensure.

Regional pulmonary blood flow in piglets during group B streptococcal bacteremia

Shunt fraction (QS/QT) and perfusion to hypoxic lung regions increase when pulmonary vascular driving pressure (PVDP) is raised by increasing pulmonary blood flow or enlarging the size of the hypoxic region. We hypothesized that perfusion to collapsed areas would similarly increase when PVDP was increased by a circulating pulmonary vasoconstrictor. Group B streptococci (GBS) were infused into 10 young piglets with left lung atelectasis to produce pulmonary vasoconstriction and determine if perfusion to collapsed regions (QL/QT) and intrapulmonary QS/QT increased as pulmonary vascular resistance (PVR) increased. Left lung collapse alone increased PVR from 11 +/- 3 to 18 +/- 10 mm Hg/L/min and QS/QT from 1.9 +/- 1.4% to 8.3 +/- 6.4%; QL/QT decreased from 44 +/- 1% to 10 +/- 7% of total pulmonary blood flow (p less than 0.02). Intravenous GBS increased PVDP from 11 +/- 3 to 27 +/- 4 mm Hg and further increased PVR from 18 +/- 10 to 33 +/- 12 mm Hg/L/min (p less than 0.02) but did not change cardiac output, QS/QT, or QL/QT. Changes in QL/QT and QS/QT are not predicted by changes in PVDP alone but also depend upon the site and nature of pulmonary vasoconstriction in infants with regional lung disease.

Isogenic group B streptococci devoid of capsular polysaccharide or beta-hemolysin: pulmonary hemodynamic and gas exchange effects during bacteremia in piglets

Group B beta-hemolytic streptococcus (GBS) causes thromboxane (Tx)-associated pulmonary hypertension and hypoxemia in neonatal animals and human infants. The components of GBS that induce these features of sepsis are incompletely characterized. The capsular polysaccharide has been implicated based on the effects of GBS extracts. We used isogenic mutants of a parent GBS strain (COH 31 r/s) devoid of capsular polysaccharide or beta-hemolysin to determine if these components caused the acute features of GBS bacteremia. In neonatal piglets, we observed a similar increase in pulmonary vascular resistance (PVR, mm Hg/L/min) during a 1 h infusion at 5 x 10(8) colony-forming unit/kg/h of COH 31 r/s (n = 5, 11.6 +/- 1.4 to 67.1 +/- 17.9), an isogenic GBS mutant devoid of type III CP (n = 5, 12.5 +/- 1.4 to 56.9 +/- 5.0), and an isogenic GBS mutant devoid of beta-hemolysin (n = 4, 11.0 +/- 1.9 to 51.9 +/- 7.9). All three GBS strains caused increases in blood TxB2 levels, mild arterial hypoxemia, mild reduction in mixed venous PO2, and a 30-40% reduction in cardiac output after a 1 h infusion. The Tx-synthase inhibitor, dazmegrel, completely reversed pulmonary hypertension, and partially reversed arterial hypoxemia and TxB2 levels to baseline values for all GBS strains. In six additional piglets, infusion of polystyrene beads of similar size to GBS at a dose of 5 x 10(8) beads/kg/h caused no changes in gas exchange or blood TxB2 levels, but a mild increase in PVR (13.3 +/- 2.0 to 17.7 +/- 3.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of respiratory alkalosis on thromboxane-induced pulmonary hypertension in piglets

Acute hypoxic pulmonary vasoconstriction is attenuated by respiratory alkalosis. It is unknown if alkalosis similarly reduces pulmonary vasoconstriction produced by thromboxane A2. Respiratory alkalosis does not always attenuate persistent pulmonary hypertension in newborns, some of whom have elevated serum thromboxane B2 levels. We hypothesized that alkalosis attenuates thromboxane-induced pulmonary vasoconstriction less than it does hypoxic pulmonary vasoconstriction in infants. Hemodynamic responses to respiratory alkalosis during pulmonary vasoconstriction produced in random order by breathing 12% inspired oxygen and by infusing 0.1 micrograms/kg/min of the thromboxane-mimetic U46,619 were compared in eight 2-wk-old piglets. Hypoxia increased mean pulmonary artery pressure from 12 +/- 3 to 29 +/- 2 mm Hg and pulmonary vascular resistance (PVR) from 11 +/- 4 to 25 +/- 8 mmHg/L/min; U46,619 increased pulmonary artery pressure from 16 +/- 5 to 37 +/- 6 mm Hg and PVR from 14 +/- 5 to 51 +/- 17 mm Hg/liter/min. U46,619 also decreased cardiac output accounting in part for the greater increase in PVR compared to hypoxia-induced vasoconstriction. Respiratory alkalosis decreased PVR to 14 +/- 6 mm Hg/liter/min during exposure to hypoxia and to 28 +/- 9 mm Hg/liter/min during infusion of U46,619. In six additional piglets with U46,619-induced pulmonary vasoconstriction, the effects of lung stretch and hypocapnic alkalosis were separated by doubling tidal volume and then adding inspired CO2 to return PaCO2 to prehyperventilation levels. Respiratory alkalosis decreased PVR from 52 +/- 36 to 35 +/- 21 mm Hg/liter/min. Despite the increased tidal volume, PVR increased to 53 +/- 35 Hg/liter/min when PaCO2 returned to 44 +/- 5 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Occupational medicine in the eighties: decade of change

This chapter focuses on current medical practices in the petroleum industry as they reflect the social, managerial, technological and regulatory changes of the present decade. Modern health policies and medical organizations are reviewed, with emphasis on health evaluation programs, health information distribution and clinical services. The author concludes with commentary about apparent future trends.

Bronchopulmonary dysplasia. Survival after prolonged mechanical ventilation

We reviewed the records of 4778 infants who were admitted to the affiliated intensive care nurseries at the University of Washington in Seattle from Jan 1, 1980, through Dec 31, 1983. We evaluated the outcome for patients with bronchopulmonary dysplasia who required mechanical ventilation and supplemental oxygen for at least six months. Eight (53%) of 15 study patients were alive at 3 years of age. Preselected indexes measured during the first six months of life that were not associated with death before 3 years of age included growth measurements, fraction of inspired oxygen at 6 months of age, mean airway pressure, arterial partial pressure of carbon dioxide, and right ventricular hypertrophy. In contrast, recurrent cyanotic episodes requiring intermittent muscle paralysis or long-term sedation therapy to maintain gas exchange occurred in six of seven nonsurvivors and only one of eight survivors. The survivors have reactive airway disease and recurrent lower respiratory tract infections.

Thromboxane-associated pulmonary hypertension during three types of gram-positive bacteremia in piglets

Thromboxane-associated pulmonary hypertension occurs in animals during intravenous infusion of group B streptococcus (GBS), a gram-positive neonatal pathogen. We postulated that other gram-positive neonatal pathogens, such as Streptococcus fecalis (ENT) and Staphylococcus epidermidis (S. epi) would also induce increased thromboxane synthesis and pulmonary hypertension when infused into piglets. We observed similar hemodynamic and gas exchange abnormalities during stepwise increases in the dose of GBS, Ent, and S. epi (n = 3, 4, and 4 piglets receiving each bacteria, respectively). Pulmonary vascular resistance increased significantly in the absence of acidosis or reduced arterial or mixed venous pO2 at a dose of 2.5 x 10(8) cfu/kg/h for Ent and S. epi. In 14 additional piglets, pulmonary vascular resistance increased markedly after 60 min of intravenous infusion of 4 +/- 1 x 10(8) cfu/kg/h for each organism (p less than 0.05, GBS: 11.7 +/- 1.8 to 75.6 +/- 18.4 mm Hg/liter/min, Ent: 12.7 +/- 1.7 to 64.9 +/- 10.6 mm Hg/liter/min, S. epi: 10.5 +/- 0.8 to 56.9 +/- 6.0 mm Hg/liter/min), and blood thromboxane B2 levels increased (p less than 0.05, GBS: 30 +/- 10 to 1830 +/- 330 pg/ml, Ent: 20 +/- 7 to 1110 +/- 300 pg/ml, S. epi: 31 +/- 9 to 1260 +/- 350 pg/ml). This dose of each bacteria caused a similar degree of mild arterial hypoxemia (57-66 mm Hg). The thromboxane synthetase inhibitor, dazmegrel, completely reversed pulmonary hypertension, reduced TxB2 levels to near baseline values, and partially reversed arterial hypoxemia despite ongoing bacterial infusion. We conclude that thromboxane-associated pulmonary hypertension occurs in piglets during infusion of different gram-positive neonatal pathogens.

Neonatal group B streptococcal sepsis: effects of late treatment with dazmegrel

Neonatal group B streptococcal (GBS) sepsis produces pulmonary arterial hypertension and hypoxemia that are preventable by pretreatment with the selective thromboxane A2 synthase inhibitor, dazmegrel. In the present experiment we administered dazmegrel (8 mg/kg) 2 h after the initiation of a 2 1/2 h infusion of 5 X 10(8) GBS/kg/h in ten 2- to 3-wk-old piglets. The multiple inert gas elimination technique was used to measure intrapulmonary shunt and alveolar ventilation to pulmonary perfusion mismatching. Thromboxane B2, the stable metabolite of thromboxane A2, and 6-keto-prostaglandin F1 alpha, the stable metabolite of prostacyclin, were assayed in arterial blood. Pulmonary arterial pressure increased immediately after initiation of the GBS infusion, rising from 12 +/- 2 to 34 +/- 4 torr (p less than 0.02); pulmonary vascular resistance increased by 400% (p less than 0.01). Arterial hypoxemia developed (p less than 0.02) in association with an increase in the low ventilation-perfusion ratio index but without a significant increase in intrapulmonary shunt. Thromboxane B2 levels increased 10-fold. Infusion of the carrier substance for dazmegrel after 2 h of GBS infusion produced no change in any variables. In contrast, infusion of the drug resulted in the return to pre-GBS infusion baseline values for both pulmonary arterial pressure and pulmonary vascular resistance. However, no improvement in arterial pO2 or in the low ventilation-perfusion ratio index occurred. Both pulmonary vascular resistance and pulmonary arterial pressure remained normal for 0.5 h after dazmegrel administration despite continued GBS infusion. Thromboxane B2 levels were decreased 30 min after dazmegrel (p less than 0.02), but remained greater than pre-GBS levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypoxic pulmonary vasoconstriction during and after infusion of group B Streptococcus in neonatal piglets. Vascular pressure-flow analysis

Hypoxic pulmonary vasoconstriction (HPV) is attenuated after endotoxin infusion into adult dogs and sheep. High dose infusions of Group B Streptococcus (GBS), a neonatal pathogen, into newborn animals produce pulmonary hypertension, hypoxemia, and reduced cardiac output similar to high dose endotoxin infusions in adult animals. To avoid the compounding effects of reduced arterial and mixed venous PO2, HPV was studied after low dose endotoxin in adult animals. We hypothesized that HPV would be attenuated in piglets after a low dose GBS infusion. Both PVR and pressure-flow (P/Q) relationships were measured in piglets to characterize the neonatal pulmonary vascular response to alveolar hypoxia before and after GBS infusion. Hemodynamic measurements were made under Zone 3 conditions in 5 piglets breathing room air and 13% FIO2: (1) prior to GBS, (2) 20 min into a 1-h infusion of 3 +/- 1 x 10(8) cfu/kg/h live GBS, (3) 1 h, and (4) 3 h after completion of the GBS infusion. Prior to GBS, alveolar hypoxia increased PVR (14 +/- 1.3 to 33 +/- 3.6 mm Hg/L/min) and P/Q slope (12 +/- 2.3 to 41 +/- 6.8 mm Hg/L/min). During all subsequent exposures to 13% FIO2, the PVR and P/Q slopes were similar to pre-GBS values. When animals breathed room air, the PVR and P/Q slopes were greater than pre-GBS values during but not after the GBS infusion. We conclude that HPV is not altered 1 and 3 h after a 1-h low dose GBS infusion in neonatal piglets. Infusion of GBS and alveolar hypoxia independently increase pulmonary vascular resistance.

Psoas abscess in chronic dialysis patients

We report 4 cases of nontuberculous psoas abscess occurring in patients with end stage renal disease. Fever and pain were the presenting symptoms but diagnosis was delayed. A computerized tomography scan of the abdomen was the critical test that led to the correct diagnosis. Therapy involved drainage and antibiotics, and was successful in 3 of the 4 patients.

Long-term mortality study of oil refinery workers: V. Comparison of workers hired before, during, and after World War II (1940-1945) with a discussion of the impact of study designs on cohort results

The mortality experience of a large refinery cohort (1937-1978) was examined by dividing it into three subcohorts according to hire dates: those hired before 1940, those hired during the period 1940-1945, and those hired after 1945. These three periods are approximately equivalent to before, during, and after World War II and span a total hiring period of more than 75 years. The results showed that a substantial portion of the cohort (3,330 or 27%) had been recruited during 1940-1945, and they contributed 980 or 28% of the total deaths. However, their mortality experience was quite different from the rest. A series of significant increases were seen among the external causes for accidents, suicide, and homicide. In terms of overall mortality and in contrast to the rest of the cohort, no "healthy worker effect" was seen (SMR = 1.00). They also showed increases in several types of cancer including cancers of the pancreas and prostate and leukemia. These unusual experiences cannot be explained either on the basis of their war-related deaths or on their period of employment (one-half were terminated within 1 year from date of hire), and data is insufficient to separate the role of hiring practices or their socioeconomic status. However, their life-styles were probably quite different judged from the fact that alcoholism-related deaths were increased as much as fivefold. Almost two-thirds of the total deaths occurred among 4,080 workers in the before 1940 subcohort. Further, the 5,117 workers of the after-1945 subcohort contributed only 5% of the total deaths. Thus, the results of the original refinery cohort (1937-1978) primarily reflect the experience of those employees hired before 1940. Given the same cohort method (historical prospective), cohort results vary widely according to different study designs, and this has implications for "generalizable" risk assessment or risk projections. A prospective study of new hires with 30 years of follow-up is rather inefficient because it would yield only a small number of deaths, with a strong healthy worker effect. The same is true for studies based on active workers with a short period of follow-up. Studies based on time of hire, however, provide a means for controlling time-related occupational exposures.

Long-term mortality study of oil refinery workers. IV. Exposure to the lubricating-dewaxing process

A retrospective cohort mortality study of 1,008 male oil refinery workers who ever worked on the lubricating-dewaxing process of the lube oil department and who have been followed for a period of 43 years is presented. These workers were exposed to a number of solvents, primarily methyl ethyl ketone [(MEK) CAS: 78-93-3] and toluene (CAS: 108-88-3), but at levels far below the current Occupational Safety and Health Administration's standard. The standardized mortality ratio (SMR) for all causes (0.70) and the SMR for cancer (0.86) are much lower than unity when they are compared to the mortality experience of the U.S. population. Also observed in this study were 8 prostate cancer deaths (4.4 expected) with an SMR of 1.82, which was not statistically significant (P = .16). Seven of these 8 prostate cancer deaths occurred among nonwhite males, who showed an SMR of 2.47 (P = 0.53). However, only 1 prostate cancer death was seen among workers specifically assigned to the MEK units. The remaining deaths occurred among maintenance workers who had lube oil department-wide assignments. This cancer risk increased with increasing duration of employment in the lube oil department. A latency of 20 years or more was also observed for these prostate cancer deaths. In this study the processing of lubricating oils was found to be at least as important as the MEK solvents, and department-wide maintenance workers were as much at risk as the MEK unit workers. In view of this finding and findings obtained by others, it seems prudent to continue to study lubricating-dewaxing process workers, including the medical monitoring of all such workers for prostate cancer.

A result-oriented medical information system. An alternative to the conventional approach

A result-oriented medical information system at the Gulf Oil Corporation is described. Mortality data acquired mostly from routine company operations have been used to calculate standardized mortality ratios (SMRs) and life expectancy. Results show that male employees at the age of 20 have a life expectancy of 74.8 years. Compared with the U.S. general population at age 20 with a life expectancy of 71.8 years, Gulf employees have an advantage of exactly three years. Such an advantage may seem small, but it is equivalent to the gain that could be achieved if all deaths from cancer were eliminated in the United States, a hypothetical and impossible situation. These life expectancy data have the potential for use by the company to influence insurance premiums traditionally set by life insurance companies as well as to aid in the management of the company's pension fund. The SMR for all causes for the male employees is 0.82, significantly decreased in comparison with that of the U.S. general population. This favorable experience has been referred to as "the healthy worker effect." Cause-specific SMRs show a generalized pattern of deficits, some of which are statistically significant. None showed a significant increase. Seventy-six percent of the male deaths occurred among employees aged 65 years or older. If these annuitants (those alive at the beginning of the study) were not included and only the active workers were studied, an SMR of only 0.54 would be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term mortality of oil refinery workers. II. Comparison of the experience of active, terminated and retired workers

In occupational epidemiology a retrospective cohort study normally includes active, terminated, and retired employees and the mortality results may vary considerably if any of the three groups is excluded from the study. From a large refinery cohort of 12,526 white male workers followed between January, 1937 and January, 1978, the mortality experience of three groups (the active, terminated and retired) has been examined; detailed results, along with the merits and problems of studying these groups separately, are presented. The standardized mortality ratios (SMRs) for all causes are 0.68, 1.04 and 0.89 for the active, the terminated and the retired, respectively, and for all cancer, 0.85, 0.98 and 1.05. Significantly decreased SMRs are seen for most of the causes among the active and may be attributed to the "healthy worker effect." Exclusive study of active workers, although it may yield certain useful information, particularly on diseases of the young and those with short latency periods, is primarily a study of the healthy worker effect. Many favorable effects of the active worker will be encountered. The retirees as a whole experienced no significant excess mortality for any causes, although examination of a subgroup, the early retirees, did reveal a significant excess of deaths from diseases of the nervous system and sense organs. The retired may appear to be an ideal group for study because they usually have worked for an extended period of time, they may have experienced long-term occupational exposure and they have lived long enough to develop diseases with long latency periods; however, serious problems arise from studying only the retirees and these are discussed. The terminated group contributed 41% of the person-years, 49% of the total number of individuals and 38% of the deaths and is far too important to be omitted. Contrary to previous reports, the terminated did not demonstrate a significantly adverse mortality experience when compared with the general population, although they did not show the healthy worker effect that was seen among the active.