Deterioration of Lung Function in a Pig Model of Uncontrolled Cardiac Death

INTRODUCTION

Uncontrolled donors after circulatory determination of death (uDCDD) represent a yet unexplored pool of organs potentially available for transplantation. The aims of this study were to validate a protocol of cardiac death in the pig and to investigate lung function during the process.

MATERIALS AND METHODS

Cardiac death was induced in preanesthetized animals with an injection of 600 mg propofol; once systolic blood pressure was <50 mm Hg (Agonal Phase), a 20 mEq bolus of KCl was given and, after asystolia was documented, cardiopulmonary resuscitation (CPR) started, followed by 5 minutes no touch (end-CPR). Invasive blood pressure (BP) and heart rate (HR) were recorded; blood samples taken at baseline, 15 minutes after CPR, and after the no touch period (end-CPR). Computed tomography (CT) scans were taken at baseline and at end-CPR.

RESULTS

Agonal phase was reached in 6 ± 1 minutes and lasted 3 ± 1 minutes; average HR was 49 ± 16 beats/min, and BP was 41 ± 12 mm Hg. CPR lasted 35 ± 3 minutes; average HR and BP were 113 ± 32 beats/min and 86 ± 63 mm Hg, respectively. PaO2/FiO2 decreased from 442 ± 31 mm Hg at baseline to 63 ± 36 at end-CPR (P < .001). pH decreased from 7.378 ± 0.045 to 6.931 ± 0.042 (P < .001), with a corresponding increase of lactate from 0.9 ± 0.2 to mmol/L to 12.8 ± 2.1 (P < .001). As assessed using CT scan, total lung volume decreased (baseline vs end-CPR 1107 ± 106 mL vs 617 ± 95; P < .001), whereas noninflated tissue (ie, atelectasis) significantly increased (46 ± 10 g vs 131 ± 89; P = .008).

CONCLUSIONS

Lung function greatly deteriorated after cardiac death. The model we set may constitute a reproducible platform for future investigations on lung uDCDD.

Successful Transplantation of Lungs From an Uncontrolled Donor After Circulatory Death Preserved In Situ by Alveolar Recruitment Maneuvers and Assessed by Ex Vivo Lung Perfusion

We developed a protocol to procure lungs from uncontrolled donors after circulatory determination of death (NCT02061462). Subjects with cardiovascular collapse, treated on scene by a resuscitation team and transferred to the emergency room, are considered potential donors once declared dead. Exclusion criteria include unwitnessed collapse, no-flow period of >15 min and low flow >60 min. After death, lung preservation with recruitment maneuvers, continuous positive airway pressure, and protective mechanical ventilation is applied to the donor. After procurement, ex vivo lung perfusion (EVLP) is performed. From November 2014, 10 subjects were considered potential donors; one of these underwent the full process of procurement, EVLP, and transplantation. The donor was a 46-year-old male who died because of thoracic aortic dissection. Lungs were procured 4 h and 48 min after death, and deemed suitable for transplantation after EVLP. Lungs were then offered to a rapidly deteriorating recipient with cystic fibrosis (lung allocation score [LAS] 46) who consented to the transplant in this experimental setting. Six months after transplantation, the recipient is in good condition (forced expiratory volume in 1 s 85%) with no signs of rejection. This protocol allowed procurement of lungs from an uncontrolled donor after circulatory determination of death following an extended period of warm ischemia.

Graft downsizing during ex vivo lung perfusion: case report and technical notes

Among patients with respiratory insufficiency awaiting lung transplantation, small adult patients have a lower opportunity of receiving size-matched pulmonary grafts, because of the shortage of donors, particularly those of small size. Reducing the size of an oversized graft is one of the methods to increase the donor pool; similarly, ex vivo lung perfusion is an emerging technique aimed toward the same purpose. We describe how we combined the 2 techniques (lobar transplantation plus contralateral nonanatomic graft reduction during ex vivo lung perfusion) to overcome graft shortage in a clinical case. For the 1st time, this case report demonstrates that surgical manipulation during ex vivo lung perfusion does not affect the functional improvement in a lung previously judged to be not suitable for transplantation. The 6-month follow-up results are similar to those of standard bilateral lung transplantation.

Early outcome of liver transplantation performed with organs procured from brain death donors with transient or sustained cardio-circulatory collapse

BACKGROUND

Aim of this study was to compare early graft function after transplantation of recipients transplanted with livers procured from donors after brain death who experienced transient or sustained cardio-circulatory collapse.

METHODS

We retrospectively analysed patients who underwent liver transplantation (LTx) at our Institution from January 2010 to May 2012. Recipients were divided into 3 groups: those who received livers from brain death donors who experienced reversible cardio-circulatory arrest before organ procurement (RCA); those who experienced sustained cardio-circulatory collapse, treated with extra-corporeal membrane oxygenation support as rescue therapy of refractory cardiogenic shock (ECMO). Standard donors were considered as reference group (REF). Postoperative graft function, Primary Non-Function (PNF), and complications during the first 30 days were analysed.

RESULTS

102 LTx were analysed (76 REF, 22 RCA and 4 ECMO). The main cause of donor's death was post-anoxic coma in RCA and ECMO, cerebrovascular accident in REF. SGOT in REF, RCA, and ECMO donors were 27 [17-43], 54 [34-92], 716 [190-962] respectively, SGPT 17 [12-34], 46 [27-73], 84 [51-175] UI/L respectively, both P<0.01. All recipients had similar SGOT (P=0.48), SGPT (P=0.75) and Model for End-Stage Liver Disease scores (P=0.98) before LTx; similar graft cold and warm ischemia time and serum lactate levels at the end of surgery. After LTx, Intensive Care Unit stay and the incidence of PNF were similar.

CONCLUSION

The use of livers procured from donors after brain death that experienced transient or sustained cardio-circulatory collapse was associated with early graft function comparable to that of standard donors.

Preoperative changes of forced vital capacity due to body position do not correlate with postoperative respiratory function in obese subjects

BACKGROUND

Obese patients are at risk of developing postoperative pulmonary complications. We hypothesized that preoperative changes in dynamic spirometry due to body posture would correlate with the drop of forced vital capacity (FVC) measured early after surgery.

METHODS

Thirty consecutive morbidly obese patients undergoing gastric banding were investigated. All subjects were studied the day before surgery (T0) and on postoperative day one (T1). Forced Vital Capacity (FVC) was measured, together with heart rate, mean arterial pressure and respiratory rate. At T0 measurements were taken in a random fashion with subjects in upright and in supine position. Subjects were then investigated after surgery in the supine position (T1). Postoperative pain was assessed at T1 using visual analogue scale. Intraoperative variables were also collected.

RESULTS

Body Mass Index (BMI) of the investigated subjects was 43.9 ± 5.7 Kg/m2 (range 33.8-60); their age was 40 ± 8 years. All dynamic spirometric data decreased significantly from upright to supine position (P<0.05) and after surgery from 3.07 L (2.77-3.71) to 1.50 (1.15-2.12) (FVC T0 supine vs. T1, P<0.05). Changes of FVC due to body position did not correlate with changes of FVC occurring after surgery (R2=0.105, P=0.081). When subjects were stratified by the median postoperative drop of FVC (45.74%), preoperative (anthropometric and spirometric data), intraoperative (ventilatory settings and hemodynamics) and postoperative (FVC and pain) parameters were similar between groups. The duration of pneumoperitoneum was correlated with the drop of FVC (R2=0.551, P<0.05).

CONCLUSION

The derangement of FVC that occurs in obese subjects after gastric banding is not predictable before surgery from anthropometric or spirometric data. The duration of pneumoperitoneum significantly contributes to postoperative impairment of respiratory function.

Extracorporeal lung perfusion and ventilation to improve donor lung function and increase the number of organs available for transplantation

INTRODUCTION

Ex vivo lung perfusion (EVLP) has been validated as a valuable technique to increase the pool of organs available for lung transplantation.

MATERIAL AND METHODS

After a preclinical experience, we obtained permission from the Ethics Committee of our institution to transplant lungs after EVLP reconditioning. ABO compatibility, size match, and donor arterial oxygen pressure (PaO(2))/fraction of inspired oxygen (FiO(2)) ≤ 300 mm Hg were considered to be inclusion criteria, whereas the presence of chest trauma and lung contusion, evidence of gastric content aspiration, pneumonia, sepsis, or systemic disease were exclusion criteria. We only considered subjects on an extra corporeal membrane oxygenation (ECMO) bridge to transplantation with rapid functional deterioration. Using Steen solution with packed red blood cells oxygenated with 21% O(2), 5% to 7% CO(2) was delivered, targeted with a blood flow of approximately 40% predicted cardiac output. Once normothermic, the lungs were ventilated with a tidal volume of 7 mL/kg a PEEP of 5 cmH(2)O and a respiratory rate of 7 bpm. Lungs were considered to be suitable for transplantation if well oxygenated [P(v-a) O(2) > 350 mm Hg on FiO(2) 100%], in the absence of deterioration of pulmonary vascular resistance and lung mechanics over the perfusion time.

RESULTS

From March to September 2011, six lung transplantations were performed, including two with EVLP. The functional outcomes were similar between groups: at T72 posttransplantation, the median PaO(2)/FiO(2) were 306 mm Hg (range, 282 to 331 mm Hg) and 323 mm Hg (range, 270 to 396 mm Hg) (P = 1, EVLP versus conventional). Intensive care unit ICU and hospital length of stay were similar (P = .533 and P = .663, respectively) with no mortality at 60 days in both groups. EVLP donors were older (49 ± 6 y versus 21 ± 7 y, P < .05), less well oxygenated (184 ± 6 mm Hg versus 570 ± 30, P < .05), displaying higher Oto scores (9.5 ± 0.7 versus 1.7 ± 1.5, P < .05).

CONCLUSIONS

The first 6 months of the EVLP program allowed us to increase the number of organs available for transplantation with short-term outcomes comparable to conventional transplantations.

Parenchymal and vascular lesions in ageing equine brains: histological and immunohistochemical studies

Many age-related changes are described in the nervous system of different species, but detailed studies of brain lesions in ageing horses are lacking. The aim of the present study was to systematically characterize lesions in the brains of 60 horses aged from 7 to 23 years. No gross changes were present in any brain. Microscopically, spongiform changes, lipofuscin storage, corpora amylacea, gliosis and satellitosis were common, together with axonal and neuronal swellings. The most important findings were the presence of pseudocalcium-calcium (pCa-Ca) deposits and arterial wall degeneration. Scanning electron microscopical examination of two cases with vascular mineralization revealed marked deposition of an amorphous substance in the vessel walls that was probably formed by a polyanionic protein matrix and a mineral component. Immunohistochemically, numerous axonal spheroids were positively labelled for ubiquitin. No PrPsc was detected in sections with neuronal vacuolation. Neuronal swelling, corpora amylacea, hippocampal Tau-positive neurons and methenamine-positive diffuse (preamyloid) plaques were also detected. Congo red staining failed to detect amyloid deposition. The characterization of age-related lesions in the brains of these horses will allow these changes to be discriminated from pathological processes in future studies. Some lesions described here, including some vascular changes, the presence of diffuse plaques and tau accumulation in hippocampal neurons, have not been described previously in the horse.

Immunofluorescence staining for the detection of immunoglobulins and complement (C3) in dogs with renal disease

Renal cortical biopsies from 74 dogs with different degrees of renal failure were studied by immunofluorescence to assess the frequency and extent of the deposition of immunoglobulins G, M and A (IgG, IgM, IgA) and complement C3. The dogs were divided into two groups on the basis of their clinical signs, and standard histological and electron microscopical examinations, according to whether their disease was an immune-mediated nephropathy (IMN) or a non-immune-mediated nephropathy (NIMN). In the dogs with an imn there was strong immunofluorescence due to IgG in the mesangium and the glomerular basement membrane and to IgM in the mesangium. The mechanism of immune complex trapping in the glomerulus also resulted in positive reactions to IgM in the dogs with an NIMN.

Abdomino-thoracic transmission during acs: facts and figures

Elevated intra-abdominal pressure (IAP) exerts effects not only on intra-abdominal organs, but also on organs distant to the abdominal compartment. Abdomino-thoracic interaction during intra-abdominal hypertension (IAH) or abdominal compartment syndrome (ACS) interferes with pulmonary, cardiovascular and cerebral function. In accordance with recent guidelines, IAH is defined as IAP above 12 mmHg and ACS as IAP more than 20 mmHg with one or more new organ failures. In this review we will first discuss the effects of elevated IAP on pulmonary dynamics and the relevance for interpreting airway pressures and adjusting ventilator settings. We will then discuss the interaction between abdomino-thoracic pressure transmission and global haemodynamics, the knowledge of which is necessary for correct assessment of cardiac preload and to optimize fluid therapy in the setting of IAH/ACS. A discussion on the relationship between increased IAP, increased intracranial pressure (ICP) and decreased cerebral perfusion pressure (CPP) will follow. Finally, we will review ventilator-induced thoracic pressure swings and their transmission to the abdominal compartment.

Abdomino-thoracic transmission during ACS: facts and figures

Elevated intra-abdominal pressure (IAP) exerts effects not only on intra-abdominal organs, but also on organs distant to the abdominal compartment. Abdomino-thoracic interaction during intra-abdominal hypertension (IAH) or abdominal compartment syndrome (ACS) interferes with pulmonary, cardiovascular and cerebral function. In accordance with recent guidelines, IAH is defined as IAP above 12 mmHg and ACS as IAP more than 20 mmHg with one or more new organ failures. In this review we will first discuss the effects of elevated IAP on pulmonary dynamics and the relevance for interpreting airway pressures and adjusting ventilator settings. We will then discuss the interaction between abdomino-thoracic pressure transmission and global haemodynamics, the knowledge of which is necessary for correct assessment of cardiac preload and to optimize fluid therapy in the setting of IAH/ACS. A discussion on the relationship between increased IAP, increased intracranial pressure (ICP) and decreased cerebral perfusion pressure (CPP) will follow. Finally, we will review ventilator-induced thoracic pressure swings and their transmission to the abdominal compartment.

Positive end-expiratory pressure applied to the dependent lung during one-lung ventilation improves oxygenation and respiratory mechanics in patients with high FEV1

BACKGROUND AND OBJECTIVE

The aim of this study was to test the efficacy of positive end-expiratory pressure (PEEP) to the dependent lung during one-lung ventilation, taking into consideration underlying lung function in order to select responders to PEEP.

METHODS

Forty-six patients undergoing open-chest thoracic surgical procedures were studied in an operating room of a university hospital. Patients were randomized to receive zero end-expiratory pressure (ZEEP) or 10 cmH2O of PEEP to the dependent lung during one-lung ventilation in lateral decubitus. The patients were stratified according to preoperative forced expiratory volume in 1 s (FEV1) as an indicator of lung function (below or above 72%). Oxygenation was measured in the supine position, in the lateral decubitus with an open chest, and after 20 min of ZEEP or PEEP. The respiratory system pressure-volume curve of the dependent hemithorax was measured in supine and open-chest lateral decubitus positions with a super-syringe.

RESULTS

Application of 10 cmH2O of PEEP resulted in a significant increase in PaO2 (P < 0.05). This did not occur in ZEEP group, considered as a time matched control. PEEP improved oxygenation only in patients with high FEV1 (from 11.6+/-4.8 to 15.3+/-7.1 kPa, P < 0.05). There was no significant change in the low FEV1 group. Dependent hemithorax compliance decreased in lateral decubitus, more in patients with high FEV1 (P < 0.05). PEEP improved compliance to a greater extent in patients with high FEV1 (from 33.6+/-3.6 to 48.4+/-3.9 mLcmH2O(-1), P < 0.05).

CONCLUSIONS

During one-lung ventilation in lateral decubitus, PEEP applied to the dependent lung significantly improves oxygenation and respiratory mechanics in patients with rather normal lungs as assessed by high FEV1.

Physical and biological triggers of ventilator-induced lung injury and its prevention

Ventilator-induced lung injury is a side-effect of mechanical ventilation. Its prevention or attenuation implies knowledge of the sequence of events that lead from mechanical stress to lung inflammation and stress at rupture. A literature review was undertaken which focused on the link between the mechanical forces in the diseased lung and the resulting inflammation/rupture. The distending force of the lung is the transpulmonary pressure. This applied force, in a homogeneous lung, is shared equally by each fibre of the lung's fibrous skeleton. In a nonhomogeneous lung, the collapsed or consolidated regions do not strain, whereas the neighbouring fibres experience excessive strain. Indeed, if the global applied force is excessive, or the fibres near the diseased regions experience excessive stress/strain, biological activation and/or mechanical rupture are observed. Excessive strain activates macrophages and epithelial cells to produce interleukin-8. This cytokine recruits neutrophils, with consequent full-blown inflammation. In order to prevent initiation of ventilator-induced lung injury, transpulmonary pressure must be kept within the physiological range. The prone position may attenuate ventilator-induced lung injury by increasing the homogeneity of transpulmonary pressure distribution. Positive end-expiratory pressure may prevent ventilator-induced lung injury by keeping open the lung, thus reducing the regional stress/strain maldistribution. If the transpulmonary pressure rather than the tidal volume per kilogram of body weight is taken into account, the contradictory results of the randomised trials dealing with different strategies of mechanical ventilation may be better understood.

Histological and immunohistochemical study of a neuroblastoma in a dog

A 13-year-old, male German Shepherd dog was euthanasized for a frontal temporal mass revealed by the MRI. The histological examination showed a proliferation composed of small round undifferentiated cells arranged in sheets or nests and sometimes in pseudorosettes interrupted by hypocellular zones of fibrovascular stroma. Immunohistochemical studies revealed the expression of neuroblastic epitopes. The presented neoplasm has many histological and immunohistochemical features in common with the group of olfactory neuroblastomas reported in man, so it could be classified as primitive neuroectodermal tumor with neuronal differentiation.

An improved in vivo rat model for the study of mechanical ventilatory support effects on organs distal to the lung

OBJECTIVE

To study the influence of different mechanical ventilatory support strategies on organs distal to the lung, we developed an in vivo rat model, in which the effects of different tidal volume values can be studied while maintaining other indexes.

DESIGN

Prospective, randomized animal laboratory investigation.

SETTING

University laboratory of Ospedale Maggiore di Milano-Instituto di Ricovero e Cura a Carattere Scientifico.

SUBJECTS

Anesthetized, paralyzed, and mechanically ventilated male Sprague-Dawley rats.

INTERVENTIONS

Two groups of seven rats each were randomized to receive tidal volumes of either 25% or 75% of inspiratory capacity (IC), calculated from a preliminary estimation of total lung capacity. Ventilation strategies for the two groups were as follows: a) 25% IC, 9.9+/-0.8 mL/kg; frequency, 59+/-4 beats/min; positive end-expiratory pressure, 3.6+/-0.8 cm H2O; and peak inspiratory airway pressure (Paw), 13.2+/-2 cm H20; and b) 75% IC, 29.8+/-2.9; frequency, 23+/-13; positive end-expiratory pressure, 0; peak inspiratory Paw, 29.0+/-3.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure (invasively monitored) remained well above adequate perfusion pressure values throughout, and no significant difference was seen between the two groups. PaO2, pHa, and PaCO2 values were compared after 60 mins of ventilation and again, no significant difference was seen between the two groups (PaO2, 269+/-25 and 260+/-55 torr; pHa, 7.432+/-0.09 and 7.415+/-0.03; PaCO2, 35.4+/-8 and 32.5+/-2 torr, for the 25% IC and 75% IC groups, respectively). Mean Paws were not different (6.4+/-0.8 cm H2O in the 25% IC groups, and 6.1+/-1.2 in the 75% IC groups, respectively). At the end of the experiment, animals were killed and the liver and kidney isolated, fixed in 4% formalin, cut, and stained for optic microscopy. Kidneys from rats ventilated with 75% IC showed increased Bowman's space with collapse of the glomerular capillaries. This occurred in a greater percentage of rats ventilated with 75% IC (0.67+/-0.2 vs. 0.29+/-0.2, 75% IC vs. 25% IC, respectively; p < .05). Perivascular edema was also present in rats ventilated with 75% IC (p < .05). Morphometric determinations of the empty zones (index of edema) demonstrated a trend toward differences between 75% IC livers and 25% IC (0.14+/-0.05 vs. 0.11+/-0.02, respectively).

CONCLUSION

We conclude that it is possible to study the effects of mechanical ventilatory support on organs distal to the lung by means of an in vivo rat model.

Plasma concentrations and anti-L-cytokine effects of alpha-melanocyte stimulating hormone in septic patients

OBJECTIVES

The aim of this research was to investigate endogenous concentrations and anti-cytokine effects of the antiinflammatory peptide alpha-melanocyte stimulating hormone (alpha-MSH) in patients with systemic inflammation. The objectives were to determine the following: changes over time of plasma alpha-MSH and relationship with patient outcome, correlation between plasma alpha-MSH and tumor necrosis factor (TNF)-alpha plasma concentration and production in whole blood samples, and influences of alpha-MSH on production of TNF-alpha and interleukin (IL)-1beta in whole blood samples stimulated with lipopolysaccharide (LPS).

DESIGN

Prospective, nonrandomized, clinical study.

SETTING

Intensive care unit of a university hospital.

PATIENTS

A total of 21 patients with sepsis syndrome/septic shock and an equal number of healthy volunteers.

INTERVENTIONS

Circulating alpha-MSH and TNF-alpha concentrations and TNF-alpha production in supernatants of LPS (1 ng/mL)-stimulated whole blood were measured repeatedly. To determine whether alpha-MSH can modulate production of TNF-alpha and IL-1 beta, these cytokines were measured in whole blood samples stimulated with LPS (1 ng/mL) in the presence or absence of concentrations of the peptide.

MEASUREMENTS AND MAIN RESULTS

Plasma alpha-MSH was low in early samples and gradually increased in patients who recovered but not in those who died. There was a negative correlation between plasma concentrations of alpha-MSH and TNF-alpha. In blood samples taken at early phases of sepsis syndrome, production of TNF-alpha was reduced relative to control values; such production increased in patients who recovered but not in those who died. Addition of alpha-MSH to LPS-stimulated whole blood samples inhibited production of TNF-alpha and IL-1beta in a concentration-dependent manner.

CONCLUSIONS

In patients with systemic inflammation, there are substantial changes over time in plasma concentrations of alpha-MSH that are reduced in early phases of the disease. Reduction of this endogenous modulator of inflammation could be detrimental to the host. Addition of alpha-MSH to LPS-stimulated blood samples reduces production of cytokines involved in development of septic syndrome. This inhibition by alpha-MSH, a peptide that is beneficial in treatment of experimental models of sepsis, might therefore be useful to treat sepsis syndrome in humans.

[Mechanical ventilation during thoracic anesthesia]

Aim of the study was to test individual mechanical and functional responses to open chest lateral decubitus during one lung ventilation. We measured dependent lung pressure volume (P-V) curves of 19 patients during supine and lateral decubitus. We found that patients characterized by high FEV1 developed greater changes in P-V curve shape than those characterized by low FEV1. Based on these results we decided to test a ventilation strategy characterized by the use of ZEEP or PEEP = 10 cm H2O applied to the dependent lung. In a preliminary set of patients stratified by FEV1 we found that PEEP deteriorated PaO2/FiO2 in patients with low FEV1, while there was a trend towards improvement in patients with high FEV1. It is possible that dependent lung PEEP counteracts atelectasias in normal lungs, while it may divert blood flow or create dead space in patients with sick and stiff lungs. We conclude that during one lung ventilation in open chest lateral decubitus, ventilatory setting need to be individually tailored.

Effects of the ionophore antibiotic monensin on hepatic biotransformations and target organ morphology in rats

As a preliminary in vivo approach in order to study the mechanism of toxicity of the veterinary anticoccidial monensin, male Wistar rats were orally administered 0, 2 and 12 mg kg-1 body wt. day-1 of monensin for 7 days. At the end of the experiment, effects of the ionophore on serum creatine kinase, lactic dehydrogenase and selected drug metabolising enzyme activities were investigated. Furthermore, liver, heart and quadriceps femoris muscle samples were submitted to morphological investigations. Clinical signs or increasing levels of enzymic markers of muscle injury attributable to monensin toxicosis have never been observed in treated animals. As a matter of fact all drug metabolising enzymes activities checked have not shown significant changes, except for a significant decrease of ethoxyresorufin O-deethylase (up to 31%) and aminopyrine N-demethylase (17%) activities. Morphologically, mitochondrial cristae fragmentation and initial formation of 'myelinic sheaths-like' structures have been noticed in heart and muscle fibres. As far as rat study is concerned, these results confirm heart and muscle as target organs of monensin toxicity. In addition, these findings suggest that the inhibition of hepatic biotransformation processes following the i.p. administration of the ionophore, as reported previously by other authors, might reflect unspecific cellular toxic effects rather than a specific enzyme damage.

Effects of the prone position on respiratory mechanics and gas exchange during acute lung injury

We studied 16 patients with acute lung injury receiving volume-controlled ventilation to assess the relationships between gas exchange and respiratory mechanics before, during, and after 2 h in the prone position. We measured the end-expiratory lung volume (EELV, helium dilution), the total respiratory system (Cst,rs), the lung (Cst,L) and the thoracoabdominal cage (Cst,w) compliances (end-inspiratory occlusion technique and esophageal balloon), the hemodynamics, and gas exchange. In the prone position, PaO2 increased from 103.2 +/- 23.8 to 129.3 +/- 32.9 mm Hg (p < 0.05) without significant changes of Cst,rs and EELV. However, Cst,w decreased from 204.8 +/- 97.4 to 135.9 +/- 52.5 ml/cm H2O (p < 0.01) and the decrease was correlated with the oxygenation increase (r = 0.62, p < 0.05). Furthermore, the greater the baseline supine Cst,w, the greater its decrease in the prone position (r = 0.82, p < 0.01). Consequently, the oxygenation changes in the prone position were predictable from baseline supine Cst,w (r = 0.80, p < 0.01). Returning to the supine position, Cst,rs increased compared with baseline (42.3 +/- 14.4 versus 38.4 +/- 13.7 ml/cm H2O; p < 0.01), mainly because of the lung component (57.5 +/- 25.1 versus 52.4 +/- 23.3 ml/cm H2O; p < 0.01). Thus, (1) baseline Cst,w and its changes may play a role in determining the oxygenation response in the prone position; (2) the prone position improves Cst,rs and Cst,L when the supine position is resumed.

Inhibition of exhaled nitric oxide production during sepsis does not prevent lung inflammation

OBJECTIVES

Increases in exhaled nitric oxide have been demonstrated to originate from the lungs of rats after septic lung injury. The aim of this study was to investigate whether treatment with the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) would prevent lipopolysaccharide (LPS)-induced increases in exhaled nitric oxide and whether this would have an effect on septic lung inflammation.

DESIGN

Prospective, randomized, placebo-controlled animal laboratory investigation.

SETTING

University laboratory.

SUBJECTS

Male, anesthetized, paralyzed, and mechanically ventilated Sprague-Dawley rats (n = 27).

INTERVENTIONS

Rats were mechanically ventilated with air filtered to remove nitric oxide (expiratory rate 40 breaths/min, tidal volume 3 mL, positive end-expiratory pressure 0, FIO2 0.21). They were then randomized to receive intravenous injections of either L-NAME (25 mg/kg/hr x 4 hrs) (n = 11) or saline (n = 10). Both groups were again randomized to receive either LPS (Salmonella typhosa: 20 mg/kg i.v. x 1 dose) or an equal volume of saline 5 mins later. Thereafter, exhaled gas was collected in polyethylene bags for measurements of nitric oxide concentration. After 4 hrs, the rats were killed and the lungs were preserved and examined histologically. To examine the effect of L-NAME and LPS on mean arterial blood pressure, six additional rats underwent the same ventilation protocol with cannulation of the right internal carotid artery so that systemic arterial pressures could be measured.

MEASUREMENTS AND MAIN RESULTS

Exhaled gas was collected and measurements of NO concentrations were made using chemiluminescence every 20 mins for 240 mins during ventilation. A total lung injury score was calculated by determining the extent of cellular infiltrate, exudate and hemorrhage. Mean arterial pressure was recorded every 5 mins for 20 mins and then at 20-min periods for 120 mins. Exhaled nitric oxide concentrations increased in all the LPS-treated rats that did not receive L-NAME by 120 mins; a plateau was reached by 190 mins that was approximately 4 times greater than control rats not treated with LPS (p < .001). In contrast, rats treated with L-NAME and LPS did not show an increase in exhaled NO. Administration of L-NAME induced a 10-min nonsustained increase in mean arterial pressure in two rats treated with L-NAME followed by LPS. This increase in mean arterial pressure was not seen in two placebo and two LPS-treated rats that did not receive L-NAME. Lung inflammation was significantly worse in the two groups of rats which received LPS compared with the two that did not. L-NAME did not cause lung inflammation in rats that did not receive LPS; however, LPS-treated rats that received L-NAME had more inflammatory interstitial infiltrate (p < .05) and a trend toward worse lung injury than did LPS-treated rats that did not receive L-NAME.

CONCLUSION

We conclude that L-NAME can inhibit the increase in exhaled NO from the lungs of septic rats, but that this inhibition does not reduce lung inflammation, and may worsen it.

Injurious ventilatory strategies increase cytokines and c-fos m-RNA expression in an isolated rat lung model

We examined the effect of ventilation strategy on lung inflammatory mediators in the presence and absence of a preexisting inflammatory stimulus. 55 Sprague-Dawley rats were randomized to either intravenous saline or lipopolysaccharide (LPS). After 50 min of spontaneous respiration, the lungs were excised and randomized to 2 h of ventilation with one of four strategies: (a) control (C), tidal volume (Vt) = 7 cc/kg, positive end expiratory pressure (PEEP) = 3 cm H2O; (b) moderate volume, high PEEP (MVHP), Vt = 15 cc/kg; PEEP = 10 cm H2O; (c) moderate volume, zero PEEP (MVZP), Vt = 15 cc/kg, PEEP = 0; or (d) high volume, zero PEEP (HVZP), Vt = 40 cc/kg, PEEP = 0. Ventilation with zero PEEP (MVZP, HVZP) resulted in significant reductions in lung compliance. Lung lavage levels of TNFalpha, IL-1beta, IL-6, IL-10, MIP-2, and IFNgamma were measured by ELISA. Zero PEEP in combination with high volume ventilation (HVZP) had a synergistic effect on cytokine levels (e.g., 56-fold increase of TNFalpha versus controls). Identical end inspiratory lung distention with PEEP (MVHP) resulted in only a three-fold increase in TNFalpha, whereas MVZP produced a six-fold increase in lavage TNFalpha. Northern blot analysis revealed a similar pattern (C, MVHP < MVZP < HVZP) for induction of c-fos mRNA. These data support the concept that mechanical ventilation can have a significant influence on the inflammatory/anti-inflammatory milieu of the lung, and thus may play a role in initiating or propagating a local, and possibly systemic inflammatory response.

Effects of positive end-expiratory pressure on regional distribution of tidal volume and recruitment in adult respiratory distress syndrome

The distribution of tidal volume (VT) and recruitment was investigated by chest computed tomography (CT) in eight sedated-paralyzed patients with the adult respiratory distress syndrome (ARDS). A CT section was obtained in the supine position at 0, 5, 10, 15, and 20 cm H2O positive end-expiratory pressure (PEEP) and at the corresponding inspiratory plateau pressure (21 +/- 1.8, 26 +/- 1.4, 31 +/- 1.8, 38 +/- 2.1, and 46 +/- 3.2 cm H2O [mean +/- SE]), keeping VT constant. Each CT section was divided along its ventral-dorsal height into 10 equally spaced intervals (levels). Vi(insp) and Vi(exp) were defined as the gas volume for level i (i = 1 to 10) at end-inspiration and at end-expiration, respectively. The following variables were computed at each lung level: (1) distribution of CT section tidal volume (VTct), i.e., the fraction of VT that inflates a given lung level; (2) the plateau-induced and PEEP-induced recruitment, i.e., the amount of lung tissue previously collapsed that inflates at plateau pressure and at PEEP, respectively; (3) the reopening-collapsing tissue, i.e., the amount of lung tissue that regains inflation at plateau pressure and collapses at PEEP. With increasing PEEP from 0 to 20 cm H2O, the VTct distribution decreased significantly (p < 0.01) in the upper levels, did not change in the middle levels, and increased significantly (p < 0.01) in the lower levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the subchronic administration of zinc ethylene-bis-dithiocarbamate (zineb) to rabbits

The effects of subchronic administration (90 d) of zineb were studied in male New Zealand White rabbits. Rabbits were allotted to 3 groups of 8 animals each and offered diets containing 0, 0.3 or 0.6% zineb. A marked decline in weight gain, hemoglobin concentration, hematocrit, and erythrocyte and leucocyte counts occurred at the highest zineb dosage. There was a dose-related depression in circulating thyroid hormones, whereas serum lipid concentration, particularly that of cholesterol and triglycerides, increased. Hepatic lipid concentration was considerably reduced in rabbits exposed to 0.6% zineb. Neither serum testosterone nor the activities of selected testicular enzymes showed changes suggestive of testicular involvement. Pathological changes were in agreement with biochemical findings; there was a marked dose-related enlargement of the thyroid showing histological colloid struma. An increase in relative weight and moderate glycogenosis were detected in liver, whereas no lesions occurred in testes. It was concluded that thyroid and liver are the main targets for zineb toxicity in the rabbit. Unlike the results from previous studies conducted on other food-producing species, repeated exposure of rabbits to zineb failed to cause testicular damage. This might be related to the inability of zineb to significantly accumulate in the testes.

Increased nitric oxide in exhaled gas as an early marker of lung inflammation in a model of sepsis

Nitric Oxide (NO) has been implicated in the pathologic vasodilation of sepsis. Because NO can be measured in the exhaled gas of animals and humans, we hypothesized that increases in exhaled NO would occur in a septic model. Using a blinded design, 10 male Sprague-Dawley rats (300 to 400 g) were anesthetized, paralyzed, tracheotomized, and randomized (5/group) to receive an intravenous injection of either lipopolysaccharide (LPS) (Salmonella typhosa, 20 mg/kg) or placebo (equal volume of saline). Thereafter, exhaled gas was collected and measurements of NO concentration were made using chemiluminescence every 20 min for 300 min during ventilation (RR 40 breaths/min, VT 3 ml; PEEP 0, FIO2 0.21). Another group of 10 animals (5 LPS; 5 control) were treated in the same fashion and then killed at 240 min and an arterial blood sample obtained for blood gas and TNF alpha determinations. Pressure volume (PV) curves were constructed and lungs removed, preserved, and submitted for histologic evaluation. LPS-treated rats had lower mean arterial pressures than the control group, p < 0.0001. No significant differences in static lung compliance and PV curves were found in the two groups. TNF alpha levels were greater in the LPS group (1.40 +/- 0.24 ng/ml) versus control group (0.09 +/- 0.04 ng/ml), p < 0.001. By contrast to the control group, exhaled NO concentration rose in all LPS-treated rats at approximately 100 min and at about 160 min reached a plateau that was 6 times greater than control levels (p < 0.0001). There was greater interstitial, airspace, and total lung injury in the LPS group (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Pathological findings in rabbits and sheep following the subacute administration of triphenyltin acetate

Organotins are used worldwide in agricultural practice as fungicides and herbicides. In this study morphological and ultrastructural investigations related with the subacute administration of the fungicide triphenyltin acetate (TPTA) were carried out in rabbits and lambs. Twenty-eight New Zealand White male rabbits were fed diets containing 0, 15, 75 or 150 ppm TPTA for 70 d; comparable doses (1 or 7.5 mg/kg bw) were administered daily to immature male lambs. After 70 d of treatment dose-dependent decreases in body weight gain and thymus relative weights were seen in both species. In rabbits, the main histological lesions were found in the thymus and mesenteric and retropharyngeal lymph nodes, confirming the immunosuppressive activity reported by TPTA in other rodents. Lambs showed similar, but less severe lesions. However, the involvement of the immune system was noted in both species, but at doses much higher than those reported for rats and guinea pigs. This different immunotoxic activity of TPTA might be related to species differences in the toxicokinetics of the fungicide.

Pathologic changes, tissue distribution, and extent of conversion to ethylenethiourea after subacute administration of zinc ethylene-bis-dithiocarbamate (zineb) to calves with immature rumen function

The toxicity of zinc ethylene-bis-dithiocarbamate (zineb), a widely used fungicide, was studied in four 4-week-old Friesian calves with immature rumen function. Calves were first subjected to liver biopsy, and thereafter, 3 of them were orally administered 200 mg of zineb/kg of body weight daily for 80 days, whereas the fourth calf served as control and remained untreated. Clinical, hematologic, and pathologic (including ultrastructural) findings were recorded. The distribution in body fluids and tissues of the parent compound and one of its main metabolites, ethylenethiourea (ETU), also was examined. Treated calves had unthrifty appearance and reduction in weight gain. They also had remarkable impairment of thyroid function, as reflected by reduction in serum concentrations of triiodothyronine and thyroxine and increase in weight of the thyroid gland associated with epithelial vacuolization and foci of hyperplasia. Moderate increase in liver glycogen content and impairment in maturation of germ cells were recorded consistently. Whereas zineb was widely distributed in body tissues, ETU accumulated mainly in the liver and the thyroid gland, although noticeable concentrations also were attained in muscle. Data were consistent with involvement of ETU mainly in the pathogenesis of thyroid gland lesions, and indicate that unweaned calves given zineb develop a clinicopathologic syndrome that does not differ qualitatively from that already described in adult cattle exposed to zineb.

Glycoconjugate expression in normal hepatoid glands and hepatoid gland adenomas and carcinomas in dogs

Although neoplastic changes in canine hepatoid perianal glands (HPG) are quite common, the biological behaviour is sometimes difficult to assess on the basis of the histopathological examination. In an attempt to detect differences in the glycoconjugate expression between normal and neoplastic HPG, and to verify their relation to the degree of neoplastic progression, normal and neoplastic HPG were studied in 13 dogs, using 11 biotinylated lectins. In HPG adenomas the majority of the cells did not stain or stained weakly after incubation with pokeweed mitogen, LCA and UEA-I. In HPG carcinoma the basal cells lost the specific binding for WGA while heterogeneous distribution of conconavalin-A staining was observed.