Mechanisms of neurogenic pulmonary edema

Just Say NO: Inhaled Nitric Oxide Effect on Respiratory Parameters Following Traumatic Brain Injury in Humans and a Porcine Model

INTRODUCTION

The mechanism of post-traumatic brain injury (TBI) hypoxemia involves ventilation/perfusion mismatch and loss of pulmonary hypoxic vasoconstriction. Inhaled nitric oxide (iNO) has been studied as an adjunct treatment to avoid the use of high positive end-expiratory pressure and inspired oxygen in treatment-refractory hypoxia. We hypothesized that iNO treatment following TBI would improve systemic and cerebral oxygenation via improved matching of pulmonary perfusion and ventilation.

METHODS

Thirteen human patients with isolated TBI were enrolled and randomized to receive either placebo or iNO with measured outcomes including pulmonary parameters, blood gas data, and intracranial pressure (ICP) /perfusion. To complement this study, a porcine model of TBI (including 10 swine) was utilized with measured outcomes of brain tissue blood flow and oxygenation, ventilator parameters, and blood gas data both after administration and following drug removal and clearance.

RESULTS

There were no clinically significant changes in pulmonary parameters in either the human or porcine arm following administration of iNO when compared to either the placebo group (human arm) or the internal control (porcine arm). Analysis of pooled human data demonstrated the preservation of alveolar recruitment in TBI patients. There were no clinically significant changes in human ICP or cerebral perfusion pressure following iNO administration compared to controls.

CONCLUSIONS

iNO had no significant effect on clinically relevant pulmonary parameters or ICPs following TBI in both human patients and a porcine model. The pressure-based recruitment of the human lungs following TBI was preserved. Further investigation will be needed to determine the degree of utility of iNO in the setting of hypoxia after polytrauma.

Trajectory of PaO2/FiO2 Ratio in Shock After Angiotensin II

INTRODUCTION

High-dose catecholamines can impair hypoxic pulmonary vasoconstriction and increase shunt fraction. We aimed to determine if Angiotensin II (Ang-2) is associated with improved PaO2/FiO2 and SpO2/FiO2 in patients in shock.

METHODS

Adult patients at four tertiary care centers and one community hospital in the United States who received Ang-2 from July 2018-September 2020 were included in this retrospective, observational cohort study. PaO2, SpO2, and FiO2 were measured at 13 timepoints during the 48-h before and after Ang-2 initiation. Piecewise linear mixed models of PaO2/FiO2 and SpO2/FiO2 were created to evaluate hourly changes in oxygenation after Ang-2 initiation. The difference in the proportion of patients with PaO2/FiO2 ≤ 300 mm Hg at the time of Ang-2 initiation and 48 h after was also examined.

RESULTS

The study included 254 patients. In the 48 h prior to Ang-2 initiation, oxygenation was significantly declining (hourly PaO2/FiO2 change -4.7 mm Hg/hr, 95% CI - 6.0 to -3.5, p < .001; hourly SpO2/FiO2 change -3.1/hr, 95% CI-3.7 to -2.4, p < .001). Ang-2 treatment was associated with significant improvements in PaO2/FiO2 and SpO2/FiO2 in the 48-h after initiation (hourly PaO2/FiO2 change +1.5 mm Hg/hr, 95% CI 0.5-2.5, p  =  .003; hourly SpO2/FiO2 change +0.9/hr, 95% CI 0.5-1.2, p < .001). The difference in the hourly change in oxygenation before and after Ang-2 initiation was also significant (pinteraction < 0.001 for both PaO2/FiO2 and SpO2/FiO2). This improvement was associated with significantly fewer patients having a PaO2/FiO2 ≤ 300 mm Hg at 48 h compared to baseline (mean difference -14.9%, 95% CI -25.3% to -4.6%, p  =  .011). Subgroup analysis found that patients with either a baseline PaO2/FiO2 ≤ 300 mm Hg or a norepinephrine-equivalent dose requirement >0.2 µg/kg/min had the greatest associations with oxygenation improvement.

CONCLUSIONS

Ang-2 is associated with improved PaO2/FiO2 and SpO2/FiO2. The mechanisms for this improvement are not entirely clear but may be due to catecholamine-sparing effect or may also be related to improved ventilation-perfusion matching, intrapulmonary shunt, or oxygen delivery.

Exploring the Modulatory Effect of High-Fat Nutrition on Lipopolysaccharide-Induced Acute Lung Injury in Vagotomized Rats and the Role of the Vagus Nerve

During esophagectomy, the vagus nerve is transected, which may add to the development of postoperative complications. The vagus nerve has been shown to attenuate inflammation and can be activated by a high-fat nutrition via the release of acetylcholine. This binds to α7 nicotinic acetylcholine receptors (α7nAChR) and inhibits α7nAChR-expressing inflammatory cells. This study investigates the role of the vagus nerve and the effect of high-fat nutrition on lipopolysaccharide (LPS)-induced lung injury in rats. Firstly, 48 rats were randomized in 4 groups as follows: sham (sparing vagus nerve), abdominal (selective) vagotomy, cervical vagotomy and cervical vagotomy with an α7nAChR-agonist. Secondly, 24 rats were randomized in 3 groups as follows: sham, sham with an α7nAChR-antagonist and cervical vagotomy with an α7nAChR-antagonist. Finally, 24 rats were randomized in 3 groups as follows: fasting, high-fat nutrition before sham and high-fat nutrition before selective vagotomy. Abdominal (selective) vagotomy did not impact histopathological lung injury (LIS) compared with the control (sham) group (p > 0.999). There was a trend in aggravation of LIS after cervical vagotomy (p = 0.051), even after an α7nAChR-agonist (p = 0.090). Cervical vagotomy with an α7nAChR-antagonist aggravated lung injury (p = 0.004). Furthermore, cervical vagotomy increased macrophages in bronchoalveolar lavage (BAL) fluid and negatively impacted pulmonary function. Other inflammatory cells, TNF-α and IL-6, in the BALF and serum were unaffected. High-fat nutrition reduced LIS after sham (p = 0.012) and selective vagotomy (p = 0.002) compared to fasting. vagotomy. This study underlines the role of the vagus nerve in lung injury and shows that vagus nerve stimulation using high-fat nutrition is effective in reducing lung injury, even after selective vagotomy.

A Focused Review on Primary Graft Dysfunction after Clinical Lung Transplantation: A Multilevel Syndrome

Primary graft dysfunction (PGD) is the clinical syndrome of acute lung injury after lung transplantation (LTx). However, PGD is an umbrella term that encompasses the ongoing pathophysiological and -biological mechanisms occurring in the lung grafts. Therefore, we aim to provide a focused review on the clinical, physiological, radiological, histological and cellular level of PGD. PGD is graded based on hypoxemia and chest X-ray (CXR) infiltrates. High-grade PGD is associated with inferior outcome after LTx. Lung edema is the main characteristic of PGD and alters pulmonary compliance, gas exchange and circulation. A conventional CXR provides a rough estimate of lung edema, while a chest computed tomography (CT) results in a more in-depth analysis. Macroscopically, interstitial and alveolar edema can be distinguished below the visceral lung surface. On the histological level, PGD correlates to a pattern of diffuse alveolar damage (DAD). At the cellular level, ischemia-reperfusion injury (IRI) is the main trigger for the disruption of the endothelial-epithelial alveolar barrier and inflammatory cascade. The multilevel approach integrating all PGD-related aspects results in a better understanding of acute lung failure after LTx, providing novel insights for future therapies.

Noninvasive and invasive mechanical ventilation for neurologic disorders

Patients with acute neurologic injuries frequently require mechanical ventilation due to diminished airway protective reflexes, cardiopulmonary failure secondary to neurologic insults, or to facilitate gas exchange to precise targets. Mechanical ventilation enables tight control of oxygenation and carbon dioxide levels, enabling clinicians to modulate cerebral hemodynamics and intracranial pressure with the goal of minimizing secondary brain injury. In patients with acute spinal cord injuries, neuromuscular conditions, or diseases of the peripheral nerve, mechanical ventilation enables respiratory support under conditions of impending or established respiratory failure. Noninvasive ventilatory approaches may be carefully considered for certain disease conditions, including myasthenia gravis and amyotrophic lateral sclerosis, but may be inappropriate in patients with Guillain-Barré syndrome or when relevant contra-indications exist. With regard to discontinuing mechanical ventilation, considerable uncertainty persists about the best approach to wean patients, how to identify patients ready for extubation, and when to consider primary tracheostomy. Recent consensus guidelines highlight these and other knowledge gaps that are the focus of active research efforts. This chapter outlines important general principles to consider when initiating, titrating, and discontinuing mechanical ventilation in patients with acute neurologic injuries. Important disease-specific considerations are also reviewed where appropriate.

Pulmonary Edema: A Pictorial Review of Imaging Manifestations and Current Understanding of Mechanisms of Disease

Pulmonary edema is a common clinical entity caused by the extravascular movement of fluid into the pulmonary interstitium and alveoli. The four physiologic categories of edema include hydrostatic pressure edema, permeability edema with and without diffuse alveolar damage (DAD), and mixed edema where there is both an increase in hydrostatic pressure and membrane permeability. As radiographic manifestations and etiologies are varied, an appreciation for both the common and uncommon manifestations and causes of pulmonary edema is essential for accurate diagnosis.

Endothelial cell Piezo1 mediates pressure-induced lung vascular hyperpermeability via disruption of adherens junctions

Increased hydrostatic pressure in lung capillaries experienced during high altitude, head trauma, and left heart failure can lead to disruption of lung endothelial barrier and edema formation. We identified Piezo1 as a mechanical sensor responsible for endothelial barrier breakdown (barotrauma) secondary to reduced expression of the endothelial adherens junction proteins VE-cadherin, β-catenin, and p120-catenin. Endothelial-specific deletion or pharmacological inhibition of Piezo1 prevented lung capillary leakage, suggesting a therapeutic approach for preventing edema and associated lung failure.

Increased pulmonary microvessel pressure experienced in left heart failure, head trauma, or high altitude can lead to endothelial barrier disruption referred to as capillary “stress failure” that causes leakage of protein-rich plasma and pulmonary edema. However, little is known about vascular endothelial sensing and transduction of mechanical stimuli inducing endothelial barrier disruption. Piezo1, a mechanosensing ion channel expressed in endothelial cells (ECs), is activated by elevated pressure and other mechanical stimuli. Here, we demonstrate the involvement of Piezo1 in sensing increased lung microvessel pressure and mediating endothelial barrier disruption. Studies were made in mice in which Piezo1 was deleted conditionally in ECs (Piezo1^iΔEC), and lung microvessel pressure was increased either by raising left atrial pressure or by aortic constriction. We observed that lung endothelial barrier leakiness and edema induced by raising pulmonary microvessel pressure were abrogated in Piezo1^iΔEC mice. Piezo1 signaled lung vascular hyperpermeability by promoting the internalization and degradation of the endothelial adherens junction (AJ) protein VE-cadherin. Breakdown of AJs was the result of activation of the calcium-dependent protease calpain and degradation of the AJ proteins VE-cadherin, β-catenin, and p120-catenin. Deletion of Piezo1 in ECs or inhibition of calpain similarly prevented reduction in the AJ proteins. Thus, Piezo1 activation in ECs induced by elevated lung microvessel pressure mediates capillary stress failure and edema formation secondary to calpain-induced disruption of VE-cadherin adhesion. Inhibiting Piezo1 signaling may be a useful strategy to limit lung capillary stress failure injury in response to elevated vascular pressures.

Chinese guidelines for the diagnosis and treatment of hand, foot and mouth disease (2018 edition)

BACKGROUND

Hand, foot, and mouth disease (HFMD) is a common infectious disease in childhood caused by an enterovirus (EV), and which is principally seen in children under 5 years of age. To promote diagnostic awareness and effective treatments, to further standardize and strengthen the clinical management and to reduce the mortality of HFMD, the guidelines for diagnosis and treatment have been developed.

METHODS

National Health Commission of China assembled an expert committee for a revision of the guidelines. The committee included 33 members who are specialized in diagnosis and treatment of HFMD.

RESULTS

Early recognition of severe cases is utmost important in diagnosis and treatment of patients with HFMD. The key to diagnosis and treatment of severe cases lies in the timely and accurate recognition of stages 2 and 3 of HFMD, in order to stop progression to stage 4. Clinicians should particularly pay attention to those EV-A71 cases in children aged less than 3 years, and those with disease duration less than 3 days. The following indicators should alert the clinician of possible deterioration and impending critical disease: (1) persistent hyperthermia; (2) involvement of nervous system; (3) worsening respiratory rate and rhythm; (4) circulatory dysfunction; (5) elevated peripheral WBC count; (6) elevated blood glucose and (7) elevated blood lactic acid. For treatment, most mild cases can be treated as outpatients. Patients should be isolated to avoid cross-infection. Intense treatment modalities should be given for those severe cases.

CONCLUSION

The guidelines can provide systematic guidance on the diagnosis and management of HFMD.

Recurrent Acute Neurogenic Pulmonary Edema after Uncontrolled Seizures

Acute pulmonary edema following significant injury to the central nervous system is known as neurogenic pulmonary edema (NPE). Commonly seen after significant neurological trauma, NPE has also been described after seizure. While many pathogenic theories have been proposed, the exact mechanism remains unclear. We present a 31-year-old man who developed recurrent acute NPE on two consecutive admissions after experiencing witnessed generalized tonic-clonic (GTC) seizures. Chest radiographs obtained after seizure during both admissions showed bilateral infiltrates which rapidly resolved within 24 hours. He required intubation on each occasion, was placed on lung protective ventilation, and was successfully extubated within 72 hours. There was no identified source of infection, and no cardiac pathology was thought to be contributory.

An assessment of a pediatric early warning system score in severe hand-foot-and-mouth disease children: To detect clinical deterioration in hospitalized children

Identification of deteriorating severe hand, foot, and mouth disease (HFMD) children for referral to intensive care remains problematic.The medical records of 2382 hospitalized children with severe HFMD from May 2013 to September 2015 were retrospectively reviewed. A Pediatric Early Warning System (PEWS) score was designed based on study parameters on admission, evaluated in a logistic regression model, and subsequently validated with different cut-off scores, to predict the risk for clinical deterioration.After admission, 191 cases were transferred to the pediatric intensive care unit (PICU) and 2191 were admitted to the infectious disease department. Of which, 116 cases were subsequently transferred to PICU, with younger age, consciousness levels of sluggishness, lethargy or drowsiness, rashes with vesicles on the hands or feet, moderate or high fever, increased or disordered lung marking or pulmonary infiltration, abnormal heart rate, fasting plasma glucose, blood platelet, and C-reactive protein. A corresponding 10-component PEWS score >7 was significantly associated with subsequent transfer to PICU.A 10-component PEWS score >7 has good specificity but poor sensitivity for identifying severe HFMD children vulnerable to clinical deterioration.

Neuropulmonology

Neuropulmonology refers to the complex interconnection between the central nervous system and the respiratory system. Neurologic injury includes traumatic brain injury, hemorrhage, stroke, and seizures, and in each there are far-reaching effects that can result in pulmonary dysfunction. Systemic changes can induce impairment of pulmonary function due to changes in the core structure and function of the lung. The conditions and disorders that often occur in these patients include aspiration pneumonia, neurogenic pulmonary edema, and acute respiratory distress syndrome, but also several abnormal respiratory patterns and sleep-disordered breathing. Lung infections, pulmonary edema - neurogenic or cardiogenic - and pulmonary embolus all are a serious barrier to recovery and can have significant effects on outcomes such as hospital course, prognosis, and mortality. This review presents the spectrum of pulmonary abnormalities seen in neurocritical care.

Neurogenic Pulmonary Edema Following Catastrophic Subarachnoid Hemorrhage: A Case Report and Pathophysiologic Review

Neurogenic pulmonary edema (NPE) is an increase in interstitial and alveolar lung fluid that occurs as a direct consequence of acute or subacute central nervous system (CNS) injury. In this review we describe a patient who developed hypoxemic respiratory failure as a result of NPE following catastrophic subarachnoid hemorrhage (SAH). The patient displayed many of the characteristic symptoms, signs, and physiologic aberrations associated with NPE, including an altered level of consciousness, dyspnea, cyanosis, crackles, hypoxemia, and diffuse pulmonary infiltrates. These clinical features can be mistaken for other causes of pulmonary edema and may lead to confusion in the diagnosis and therapeutic approach of hypoxemic respiratory failure in the setting of CNS injury. Although NPE is thought to be due to a combination of pulmonary capillary leakage and elevated intravascular pressures, many questions about its pathophysiology remain unanswered. Data from animal models using therapeutic trials of antiadrenergic agents suggest a significant role for sympathetic nervous system activation and massive catecholamine release in the pathogenesis of this disorder. The most common causes of NPE include head trauma, seizures, cerebral hemorrhages, subarachnoid bleeds, and increased intracranial pressure of any etiology. As is generally observed with this disorder, conservative and supportive management of our patient's respiratory failure led to complete resolution of the NPE within 96 hours. Although NPE is an infrequent phenomenon, it should be considered in the differential diagnosis of all patients who develop respiratory complications soon after CNS injury.

Neurogenic pulmonary oedema complicating traumatic posterior fossa extradural haematoma: Case report and review

INTRODUCTION

Pulmonary oedema is accumulation of fluid in the lung air spaces and interstitia. Neurogenic pulmonary oedema (NPE) is a potentially life-threatening condition which has been noted in head injury, subarachnoid haemorrhage (SAH), intracerebral haemorrhage (ICH) and others. Timely management is crucial to achieve good outcome; however, no specific guidelines have been defined.

METHODS

A 33-year female involved in a motor vehicular accident had a GCS of 14/15 and CT scan showed a moderate-sized unilateral posterior fossa extradural haematoma (PFEDH). She had sudden deterioration in her haemodynamic status with drop in sensorium 2 hours after admission. There was a copious amount of frothy secretions noted on intubation and she was diagnosed as having NPE.

RESULTS

Sub-occiptial craneictomy (SOC) with haematoma evacuation was performed and was managed with PEEP mechanical ventilation post-operatively. Excellent outcome was obtained and was discharged with a GOS of 5.

CONCLUSIONS

NPE is a poorly understood and uncommon complication of acute CNS injury and should be considered in any patient with acute respiratory distress in the setting of CNS injury. Reduction in ICP and supportive mechanical ventilation form the mainstay of management. Diagnosis of NPE remains challenging and more reliable diagnostic criteria need to be defined to identify such cases with greater frequency.

Oxygenator in short-term LVAD circuit: a rescue in post-LVAD pulmonary complications

Pulmonary complications after left ventricular assist device (LVAD) implantation, though infrequent, can be potentially catastrophic. A 62-year-old female with cardiogenic shock, supported on short-term LVAD, developed pulmonary oedema. An oxygenator was introduced into the LVAD circuit, which improved the gas exchange and, eventually, after weaning off the oxygenator, the patient received long-term LVAD. The introduction of an oxygenator into the short-term LAVD circuit is a lifesaving manoeuvre in such a situation. It offers freedom of introducing and removing the oxygenator into the LVAD circuit without opening the chest and competing for LVAD flow.

Neurologic Causes of Acute Respiratory Dysfunction

Many neurologic diseases can cause acute respiratory decompensation, therefore a familiarity with these diseases is critical for any clinician managing patients with respiratory dysfunction. In this article, we review the anatomy of the respiratory system, focusing on the neurologic control of respiration. We discuss general mechanisms by which diseases of the peripheral and central nervous systems can cause acute respiratory dysfunction, and review the neurologic diseases which can adversely affect respiration. Lastly, we discuss the diagnosis and general management of acute respiratory impairment due to neurologic disease.

Transpulmonary Thermodilution-Based Management of Neurogenic Pulmonary Edema After Subarachnoid Hemorrhage

Neurogenic pulmonary edema (NPE) is a potentially catastrophic but treatable systemic event after subarachnoid hemorrhage (SAH). The development of NPE most frequently occurs immediately after SAH, and the severity is usually self-limiting. Despite extensive research efforts and a breadth of collective clinical experience, accurate diagnosis of NPE can be difficult, and effective hemodynamic treatment options are limited. Recently, a bedside transpulmonary thermodilution device has been introduced that traces physiological patterns consistent with current theories regarding the mechanism (hydrostatic or permeability PE) of NPE. This article provides an overview of the clinical usefulness of the advanced technique for use in the neurointensive care unit for the diagnosis and management of post-SAH NPE.

Pathogenetic Mechanisms of Neurogenic Pulmonary Edema

Neurogenic pulmonary edema (NPE) is a life-threatening complication of central nervous system (CNS) injuries. This review summarizes current knowledge about NPE etiology and pathophysiology with an emphasis on its experimental models, including our spinal cord compression model. NPE may develop as a result of activation of specific CNS trigger zones located in the brainstem, leading to a rapid sympathetic discharge, rise in systemic blood pressure, baroreflex-induced bradycardia, and enhanced venous return resulting in pulmonary vascular congestion characterized by interstitial edema, intra-alveolar accumulation of transudate, and intra-alveolar hemorrhages. The potential etiological role of neurotransmitter changes in NPE trigger zones leading to enhanced sympathetic nerve activity is discussed. Degree of anesthesia is a crucial determinant for the extent of NPE development in experimental models because of its influence on sympathetic nervous system activity. Sympathetic hyperactivity is based on the major activation of either ascending spinal pathways by spinal cord injury or NPE trigger zones by increased intracranial pressure. Attenuation of sympathetic nerve activity or abolition of reflex bradycardia completely prevent NPE development in our experimental model. Suggestions for future research into NPE pathogenesis as well as therapeutic potential of particular drugs and interventions are discussed.

Elevated cerebrospinal fluid endothelin 1 associated with neurogenic pulmonary edema in children with enterovirus 71 encephalitis

OBJECTIVES

Neurogenic pulmonary edema (NPE) is a fatal complication in children with enterovirus 71 (EV71) encephalitis. Endothelin 1 (ET-1), a potent vasoconstrictor, can induce pulmonary edema in rats via intrathecal injections. Thus, it was hypothesized that ET-1 in the central nervous system may correlate with NPE in children with EV71 encephalitis.

METHODS

Clinical data and ET-1 in the cerebrospinal fluid (CSF) were compared between three groups: (1) EV71 encephalitis with NPE; (2) EV71 encephalitis without NPE; and (3) non-EV71 aseptic meningitis. ET-1 immunostaining was performed on the brainstem of autopsy patients.

RESULTS

The EV71 with NPE group showed significantly increased CSF levels of ET-1 compared to the EV71 without NPE and the non-EV71 aseptic meningitis groups (both p<0.01). The optimum cut-off point of ET-1 to predict NPE in EV71 patients, based on the receiver operating characteristic curve, was 0.5 pg/ml (sensitivity 83%, specificity 100%). Immunostaining in the brainstem showed increased ET-1 expression, mainly in the oligodendrocytes, in EV71 with NPE patients compared with control patients.

CONCLUSION

ET-1 in the central nervous system may play a role in the development of NPE in children with EV71 infection and could be used as a biomarker or therapeutic target for NPE in EV71 encephalitis.

Oxy-RVAD: rescue in pulmonary complications after LVAD implantation

Pulmonary complications after left ventricular assist device (LVAD) implantation seldom occur; however, if present, they may prove catastrophic. An Oxy-RVAD (oxygenator in right VAD circuit) is a lifesaving technique in such cases and allows freedom of introducing and removing an oxygenator into the RVAD circuit without opening the chest and competing with LVAD flow.

Stimulants and the lung : review of literature

Illicit stimulants, such as cocaine, amphetamine, and their derivatives (e.g., "ecstasy"), continue to exact heavy toll on health care in both developed and developing countries. The US Department of Health and Human Service reported over one million illicit drug-related emergency department visits in 2010, which was higher than any of the six previous years. Both inhaled and intravenous forms of these substances of abuse can result in a variety of acute and chronic injuries to practically every part of the respiratory tract, leading potentially to permanent morbidities as well as fatal consequences--including but not limited to nasal septum perforation, pulmonary hypertension, pneumothorax, pneumomediastinum, interstitial lung disease, alveolar hemorrhage, reactive airway disease, pulmonary edema, pulmonary granulomatosis, infections, foreign body aspiration, infections, bronchoconstriction, and thermal injuries. Stimulants are all rapidly absorbed substances that can also significantly alter the patient's systemic acid-base balance and central nervous system, thereby leading to further respiratory compromise. Mounting evidence in the past decade has demonstrated that adulterants coinhaled with these substances (e.g., levamisole) and the metabolites of these substances (e.g., cocaethylene) are associated with specific forms of systemic and respiratory complications as well. Recent studies have also demonstrated the effects of stimulants on autoimmune-mediated injuries of the respiratory tract, such as cocaine-induced midline destructive lesions. A persistent challenge to studies involving stimulant-associated respiratory toxidromes is the high prevalence of concomitant usage of various substances by drug abusers, including tobacco smoking. Now more than ever, health care providers must be familiar with the multitude of respiratory toxidromes as well as the diverse pathophysiology related to commonly abused stimulants to provide timely diagnosis and effective treatment.

Neurogenic pulmonary edema caused by spontaneous cerebellar hemorrhage: A fatal case report

Background:

Neurogenic pulmonary edema (NPE) is a clinical syndrome characterized by an acute increase of pulmonary interstitial and alveolar fluid. It could result from a significant central nervous system (CNS) insult such as intracranial hemorrhage. However, NPE as a major presenting manifestation of cerebellar hemorrhage was seldom reported.

Case Description:

We introduce a rare case of a 34-year-old woman suffering from a fulminant NPE in parallel with a spontaneous cerebellar hemorrhage. Although appropriate supportive measures were taken in the neuroscience care unit, the patient failed to survive hypoxemia within 28 h after hospital admission.

Conclusion:

Pathological lesions of the cerebellum may initiate a cascade of reactions including massive sympathetic discharge and catecholamine storm, leading to a dysfunction of both cardiovascular and respiratory systems. By far, no effective therapeutic strategies have been utilized to treat such a situation. Our present report would shed light on the underlying mechanism of NPE.

Impact of aneurysm location on cardiopulmonary dysfunction after subarachnoid hemorrhage

BACKGROUND

Cardiopulmonary dysfunction may occur after aneurysmal subarachnoid hemorrhage (SAH), but its characteristics have not been fully clarified. We investigated the impact of aneurysm location on systemic hemodynamics after SAH.

METHODS

This multicenter prospective cohort study measured hemodynamic parameters in relation to aneurysm location in patients with SAH using a single-indicator transpulmonary thermodilution system (PiCCO) on days 1-14.

RESULTS

Of 204 subjects enrolled, 58 had aneurysms of the anterior communicating artery (ACA), 61 of the middle cerebral artery (MCA), 57 of the internal carotid artery (ICA), and 28 of the vertebrobasilar artery (VA/BA). Patient characteristics were similar except for predominance of coiling in the VA/BA. Patients with ACA aneurysm had a lower systemic vascular resistance index (SVRI) in the acute phase and afterload mismatch (lower cardiac index [CI] and higher SVRI) in the spasm phase. Those with ICA aneurysm had a lower CI in the acute phase, and those with VA/BA aneurysm had a warm shock-like condition (higher CI and lower SVRI) in the spasm phase. Patients with MCA aneurysm showed no specific characteristics in CI and SVRI with a significant improvement in B-type natriuretic peptide. Extravascular lung water index was high independent of left cardiac dysfunction. In multivariate analysis, age and ACA were independently related to poor global ejection fraction after SAH.

CONCLUSIONS

Aneurysm location affects cardiac output, vascular resistance, and pulmonary edema in biphasic fashion. Patient age and location of aneurysm in the ACA may be risk factors for cardiac failure after SAH.

Autonomic neural control of intrathoracic airways

Autonomic neural control of the intrathoracic airways aids in optimizing air flow and gas exchange. In addition, and perhaps more importantly, the autonomic nervous system contributes to host defense of the respiratory tract. These functions are accomplished by tightly regulating airway caliber, blood flow, and secretions. Although both the sympathetic and parasympathetic branches of the autonomic nervous system innervate the airways, it is the later that dominates, especially with respect to control of airway smooth muscle and secretions. Parasympathetic tone in the airways is regulated by reflex activity often initiated by activation of airway stretch receptors and polymodal nociceptors. This review discusses the preganglionic, ganglionic, and postganglionic mechanisms of airway autonomic innervation. Additionally, it provides a brief overview of how dysregulation of the airway autonomic nervous system may contribute to respiratory diseases.

Acute respiratory distress syndrome after spontaneous intracerebral hemorrhage*

OBJECTIVES

Acute respiratory distress syndrome develops commonly in critically ill patients in response to an injurious stimulus. The prevalence and risk factors for development of acute respiratory distress syndrome after spontaneous intracerebral hemorrhage have not been reported. We sought to determine the prevalence of acute respiratory distress syndrome after intracerebral hemorrhage, characterize risk factors for its development, and assess its impact on patient outcomes.

DESIGN

Retrospective cohort study at two academic centers.

PATIENTS

We included consecutive patients presenting from June 1, 2000, to November 1, 2010, with intracerebral hemorrhage requiring mechanical ventilation. We excluded patients with age less than 18 years, intracerebral hemorrhage secondary to trauma, tumor, ischemic stroke, or structural lesion; if they required intubation only during surgery; if they were admitted for comfort measures; or for a history of immunodeficiency.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data were collected both prospectively as part of an ongoing cohort study and by retrospective chart review. Of 1,665 patients identified by database query, 697 met inclusion criteria. The prevalence of acute respiratory distress syndrome was 27%. In unadjusted analysis, high tidal volume ventilation was associated with an increased risk of acute respiratory distress syndrome (hazard ratio, 1.79 [95% CI, 1.13-2.83]), as were male sex, RBC and plasma transfusion, higher fluid balance, obesity, hypoxemia, acidosis, tobacco use, emergent hematoma evacuation, and vasopressor dependence. In multivariable modeling, high tidal volume ventilation was the strongest risk factor for acute respiratory distress syndrome development (hazard ratio, 1.74 [95% CI, 1.08-2.81]) and for inhospital mortality (hazard ratio, 2.52 [95% CI, 1.46-4.34]).

CONCLUSIONS

Development of acute respiratory distress syndrome is common after intubation for intracerebral hemorrhage. Modifiable risk factors, including high tidal volume ventilation, are associated with its development and in-patient mortality.

Diagnosis, prevention and management of postoperative pulmonary edema

Postoperative pulmonary edema is a well-known postoperative complication caused as a result of numerous etiological factors which can be easily detected by a careful surveillance during postoperative period. However, there are no preoperative and intraoperative criteria which can successfully establish the possibilities for development of postoperative pulmonary edema. The aims were to review the possible etiologic and diagnostic challenges in timely detection of postoperative pulmonary edema and to discuss the various management strategies for prevention of this postoperative complication so as to decrease morbidity and mortality. The various search engines for preparation of this manuscript were used which included Entrez (including Pubmed and Pubmed Central), NIH.gov, Medknow.com, Medscape.com, WebMD.com, Scopus, Science Direct, MedHelp.org, yahoo.com and google.com. Manual search was carried out and various text books and journals of anesthesia and critical care medicine were also searched. From the information gathered, it was observed that postoperative cardiogenic pulmonary edema in patients with serious cardiovascular diseases is most common followed by noncardiogenic pulmonary edema which can be due to fluid overload in the postoperative period or it can be negative pressure pulmonary edema (NPPE). NPPE is an important clinical entity in immediate post-extubation period and occurs due to acute upper airway obstruction and creation of acute negative intrathoracic pressure. NPPE carries a good prognosis if promptly diagnosed and appropriately treated with or without mechanical ventilation.

Diffuse alveolar damage of the lungs in forensic autopsies: assessment of histopathological stages and causes of death

Introduction. Diffuse alveolar damage (DAD) is a morphological prototype of acute interstitial pneumonia. Hospital autopsies or open-lung biopsies are used to monitor common alveolar damage and hyaline membrane (HM) development histopathologically. The aim of this study was to detect histopathological profiles and frequency of DAD and HM in adult forensic autopsies. Materials and Methods. In total, 6813 reports with histopathological samples in 12,504 cases on which an autopsy was performed between 2006 and 2008 were investigated. Sixty-six individuals >18 years of age who were diagnosed with DAD were included. Hematoxylin- and eosin-stained lung preparations were reexamined in line with the 2002 American Thoracic Society/European Respiratory Society idiopathic interstitial pneumonia consensus criteria. Results. Histopathological examination revealed that 50 cases (75.7%) were in the exudative phase and 16 (24.2%) were in the proliferative phase. Only the rate of alveolar exudate/oedema in exudative phase cases (P = 0.003); those of alveolar histiocytic desquamation (P = 0.037), alveolar fibrosis (P = 0.017), chronic inflammation (P = 0.02), and alveolar fibrin (P = 0.001) in proliferative cases were significantly higher. The presence of alveolar fibrin was the only independent variable in favour of proliferative cases (P = 0.016). Conclusion. The detection of all DAD morphological criteria with the same intensity is not always possible in each case. Forensic autopsies may provide a favourable means for expanding our knowledge about acute lung damage, DAD, and interstitial lung disease.

Acute lung injury and acute respiratory distress syndrome: experimental and clinical investigations

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can be associated with various disorders. Recent investigation has involved clinical studies in collaboration with clinical investigators and pathologists on the pathogenetic mechanisms of ALI or ARDS caused by various disorders. This literature review includes a brief historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the long-term experimental studies and clinical investigations from our laboratory, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Neurophysiologic monitoring of the spinal accessory nerve, hypoglossal nerve, and the spinomedullary region

This review of hypoglossal nerve, spinal accessory nerve, and spinomedullary region intraoperative monitoring details pertinent central and extramedullary anatomy, an updated understanding of proper free-run EMG recording methods and recent developments in stimulation technique and instrumentation. Mapping and monitoring the floor of the fourth ventricle, especially the vagal/hypoglossal trigone region, are emphasized. Although cranial nerve transcranial electrical motor evoked potential recordings can afford appreciation of corticobulbar/corticospinal tract function and secure a more dependable measure of proximate extramedullary somatoefferents, the sometimes difficult implementation and the, as yet, unresolved alert criteria of these recordings demand critical appraisal. Nearby and intimately associated cardiochronotropic and barocontrol neural networks are described; their better understanding is recommended as an important adjunct to "routine" neural monitoring. Finally, an Illustrative case is presented to highlight the many strengths and weaknesses of "state of the art" lower cranial nerve/spinomedullary region monitoring.

Acute respiratory distress syndrome and lung injury: Pathogenetic mechanism and therapeutic implication

To review possible mechanisms and therapeutics for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). ALI/ARDS causes high mortality. The risk factors include head injury, intracranial disorders, sepsis, infections and others. Investigations have indicated the detrimental role of nitric oxide (NO) through the inducible NO synthase (iNOS). The possible therapeutic regimen includes extracorporeal membrane oxygenation, prone position, fluid and hemodynamic management and permissive hypercapnic acidosis etc. Other pharmacological treatments are anti-inflammatory and/or antimicrobial agents, inhalation of NO, glucocorticoids, surfactant therapy and agents facilitating lung water resolution and ion transports. β-adrenergic agonists are able to accelerate lung fluid and ion removal and to stimulate surfactant secretion. In conscious rats, regular exercise training alleviates the endotoxin-induced ALI. Propofol and N-acetylcysteine exert protective effect on the ALI induced by endotoxin. Insulin possesses anti-inflammatory effect. Pentobarbital is capable of reducing the endotoxin-induced ALI. In addition, nicotinamide or niacinamide abrogates the ALI caused by ischemia/reperfusion or endotoxemia. This review includes historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Contribution of α - and β -Adrenergic Mechanisms to the Development of Pulmonary Edema

Endogenous or exogenous catecholamines can induce pulmonary edema (PE). This may occur in human pathologic conditions such as in pheochromocytoma or in neurogenic pulmonary edema (NPE) but can also be provoked after experimental administration of adrenergic agonists. PE can result from stimulation with different types of adrenergic stimulation. With α-adrenergic treatment, it develops more rapidly, is more severe with abundant protein-rich fluid in the alveolar space, and is accompanied by strong generalized inflammation in the lung. Similar detrimental effects of α-adrenergic stimulation have repeatedly been described and are considered to play a pivotal role in NPE or in PE in patients with pheochromocytoma. Although β-adrenergic agonists have often been reported to prevent or attenuate PE by enhancing alveolar fluid clearance, PE may also be induced by β-adrenergic treatment as can be observed in tocolysis. In experimental models, infusion of β-adrenergic agonists induces less severe PE than α-adrenergic stimulation. The present paper addresses the current understanding of the possible contribution of α- and β-adrenergic pathways to the development of PE.

Involvement of nitric oxide pathways in neurogenic pulmonary edema induced by vagotomy

OBJECTIVE

The objective of this study was to evaluate the involvement of peripheral nitric oxide (NO) in vagotomy-induced pulmonary edema by verifying whether the nitric oxide synthases (NOS), constitutive (cNOS) and inducible (iNOS), participate in this mechanism.

INTRODUCTION

It has been proposed that vagotomy induces neurogenic pulmonary edema or intensifies the edema of other etiologies.

METHODS

Control and vagotomized rats were pretreated with 0.3 mg/kg, 3.0 mg/kg or 39.0 mg/kg of L-NAME, or with 5.0 mg/kg, 10.0 mg/kg or 20.0 mg/kg of aminoguanidine. All animals were observed for 120 minutes. After the animals' death, the trachea was catheterized in order to observe tracheal fluid and to classify the severity of pulmonary edema. The lungs were removed and weighed to evaluate pulmonary weight gain and edema index.

RESULTS

Vagotomy promoted pulmonary edema as edema was significantly higher than in the control. This effect was modified by treatment with L-NAME. The highest dose, 39.0 mg/kg, reduced the edema and prolonged the survival of the animals, while at the lowest dose, 0.3 mg/kg, the edema and reduced survival rates were maintained. Aminoguanidine, regardless of the dose inhibited the development of the edema. Its effect was similar to that observed when the highest dose of L-NAME was administered. It may be that the non-selective blockade of cNOS by the highest dose of L-NAME also inhibited the iNOS pathway.

CONCLUSION

Our data suggest that iNOS could be directly involved in pulmonary edema induced by vagotomy and cNOS appears to participate as a protector mechanism.

Neurogenic stunned myocardium after acute hydrocephalus

Neurogenic stunned myocardium (NSM) is a syndrome of cardiac stunning after a neurological insult. It is commonly observed after aneurysmal subarachnoid hemorrhage but is increasingly being reported after other neurological events. The underlying mechanism of NSM is believed to be a hypothalamic-mediated sympathetic surge causing weakened cardiac contractility and even direct cardiac myocyte damage. The authors report 2 cases of NSM in pediatric patients after acute hydrocephalus. Both patients experienced severe cardiac dysfunction in the acute phase but ultimately had a good neurological outcome and a full cardiac recovery. The identification, treatment, and outcome in 2 rare pediatric cases of NSM are discussed, and the history of the brain-cardiac connection is reviewed.

The role of nitric oxide in the development of neurogenic pulmonary edema in spinal cord-injured rats: the effect of preventive interventions

Neurogenic pulmonary edema (NPE) is an acute life-threatening complication following an injury of the spinal cord or brain, which is associated with sympathetic hyperactivity. The role of nitric oxide (NO) in NPE development in rats subjected to balloon compression of the spinal cord has not yet been examined. We, therefore, pretreated Wistar rats with the NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME) either acutely (just before the injury) or chronically (for 4 wk prior to the injury). Acute (but not chronic) l-NAME administration enhanced NPE severity in rats anesthetized with 1.5% isoflurane, leading to the death of 83% of the animals within 10 min after injury. Pretreatment with either the ganglionic blocker pentolinium (to reduce blood pressure rise) or the muscarinic receptor blocker atropine (to lessen heart rate decrease) prevented or attenuated NPE development in these rats. We did not observe any therapeutic effects of atropine administered 2 min after spinal cord compression. Our data indicate that NPE development is dependent upon a marked decrease of heart rate under the conditions of high blood pressure elicited by the activation of the sympathetic nervous system. These hemodynamic alterations are especially pronounced in rats subjected to acute NO synthase inhibition. In conclusion, nitric oxide has a partial protective effect on NPE development because it attenuates sympathetic vasoconstriction and consequent baroreflex-induced bradycardia following spinal cord injury.

Pulmonary edema after electroconvulsive therapy

A 42-year-old right-handed man with major depression, posttraumatic stress disorder, gastroesophageal reflux disease, and hypertension received 7 treatments of right unilateral electroconvulsive therapy, with the only complications being elevated blood pressure up to 180/120 mm Hg and agitation upon awakening. During eighth treatment, he experienced blood pressures as high as 210/130 mm Hg with severe agitation upon awakening from anesthesia followed by pulmonary edema. Pulmonary edema is rarely seen as a complication in electroconvulsive therapy, but if the airway becomes obstructed or there is excessive sympathetic discharge during the procedure, pulmonary edema may be more likely to occur.

Neurogenic pulmonary edema in patients with subarachnoid hemorrhage

Neurogenic pulmonary edema (NPE), leading to cardiopulmonary dysfunction, is a potentially life-threatening complication in patients with aneurysmal subarachnoid hemorrhage (SAH). We sought to assess the clinical presentation and risk factors for the development of NPE after SAH. The database contained prospectively collected information on 477 patients with SAH. Baseline characteristics, clinical and radiologic severity of the bleeding, localization of the ruptured aneurysm, and clinical outcome of patients with NPE were compared with those of patients without NPE. Further, in patients with NPE, intracranial pressure, serum cardiac biomarkers, and hemodynamic parameters during the acute phase were evaluated retrospectively. The incidence of NPE was 8% (39 of 477 patients). Most patients with NPE were severely impaired and all of them presented with radiologically severe hemorrhage. The incidence of NPE was significantly higher in patients with ruptured aneurysm in the posterior circulation. Elevated intracranial pressure was found in 67%, pathologically high cardiac biomarkers in up to 83% of patients with NPE. However, no patient suffered from persistent cardiac dysfunction. Compared with patients without NPE, patients with NPE showed poor neurologic outcome (Glasgow outcome scale 1 to 3 in 25% vs.77% of patients). In conclusion, patients with NPE have a high mortality rate more likely due to their severity grade of the bleeding. Morbidity and mortality due to cardiopulmonary failure might be reduced by appropriate recognition and treatment. The awareness of and knowledge about occurrence, clinical presentation, and treatment of NPE, are essential for all those potentially confronted with patients with SAH in the acute phase.

Neurogenic pulmonary edema in a fatal case of subarachnoid hemorrhage

Neurogenic pulmonary edema (NPE) is caused by a variety of central nervous system lesions and may appear as a subclinical complication. The fulminant form of NPE is always life-threatening. Many pathophysiologic mechanisms have been implicated in the development of NPE, but the exact interaction remains unknown. We report a case of a fulminant NPE with fatal consequences associated with a subarachnoid hemorrhage. Treatment focuses on ventilatory support and measures to reduce intracranial pressure.

Brain cell volume regulation in hyponatremia: role of sex, age, vasopressin, and hypoxia

Hyponatremia is the most common electrolyte abnormality in hospitalized patients. When symptomatic (hyponatremic encephalopathy), the overall morbidity is 34%. Individuals most susceptible to death or permanent brain damage are prepubescent children and menstruant women. Failure of the brain to adapt to the hyponatremia leads to brain damage. Major factors that can impair brain adaptation include hypoxia and peptide hormones. In children, physical factors--discrepancy between skull size and brain size--are important in the genesis of brain damage. In adults, certain hormones--estrogen and vasopressin (usually elevated in cases of hyponatremia)--have been shown to impair brain adaptation, decreasing both cerebral blood flow and oxygen utilization. Initially, hyponatremia leads to an influx of water into the brain, primarily through glial cells and largely via the water channel aquaporin (AQP)4. Water is thus shunted into astrocytes, which swell, largely preserving neuronal cell volume. The initial brain response to swelling is adaptation, utilizing the Na(+)-K(+)-ATPase system to extrude cellular Na(+). In menstruant women, estrogen + vasopressin inhibits the Na(+)-K(+)-ATPase system and decreases cerebral oxygen utilization, impairing brain adaptation. Cerebral edema compresses the respiratory centers and also forces blood out of the brain, both lowering arterial Po(2) and decreasing oxygen utilization. The hypoxemia further impairs brain adaptation. Hyponatremic encephalopathy leads to brain damage when brain adaptation is impaired and is a consequence of both cerebral hypoxia and peptide hormones.

Respiratory care

PURPOSE OF THE REVIEW

Neurosurgical patients frequently develop respiratory complications, adversely affecting neurologic outcome and survival. The review summarizes current literature and management of respiratory complications associated with brain injury.

MAJOR FINDINGS

Respiratory complications are commonly associated with traumatic brain injury and subarachnoid haemorrhage. Lung-protective ventilation with reduced tidal volumes improves outcome in acute lung injury, and should be applied to neurosurgical patients in the absence of increased intracranial pressure. Weaning from the mechanical ventilation should be initiated as soon as possible, although the role of neurological status in the weaning process is not clear. Prevention of pneumonia and aspiration improves survival. In patients with difficult weaning, early bedside percutaneous tracheostomy should be considered.

FURTHER INVESTIGATIONS

Further studies are warranted to elucidate an optimal oxygenation and ventilation in brain-injured patients, weaning strategies, predictors of the failed weaning and extubation, respiratory support in patients with difficulties to wean, and early tracheostomy.

Bench-to-bedside review: brain-lung interaction in the critically ill--a pending issue revisited

Brain and/or lung injury is the most frequent cause of admission to critical care units and patients in this setting frequently develop multiple organ dysfunction with high rates of morbidity and mortality. Mechanical ventilation is commonly used in the management of these critically ill patients and the consequent inflammatory response, together with other physiological factors, is also thought to be involved in distal organ dysfunction. This peripheral imbalance is based on a multiple-pathway cross-talk between the lungs and other organs, including the brain. Interestingly, acute respiratory distress syndrome survivors frequently present some cognitive deterioration at discharge. Such neurological dysfunction might be a secondary marker of injury and the neuroanatomical substrate for downstream impairment of other organs. Brain-lung interactions have received little attention in the literature, but recent evidence suggests that both the lungs and brain are promoters of inflammation through common mediators. This review addresses the current status of evidence regarding brain-lung interactions, their pathways and current interventions in critically ill patients receiving mechanical ventilation.

Neurogenic pulmonary edema

Neurogenic pulmonary edema (NPE) is usually defined as an acute pulmonary edema occurring shortly after a central neurologic insult. It has been reported regularly for a long time in numerous and various injuries of the central nervous system in both adults and children, but remains poorly understood because of the complexity of its pathophysiologic mechanisms involving hemodynamic and inflammatory aspects. NPE seems to be under-diagnosed in acute neurologic injuries, partly because the prevention and detection of non-neurologic complications of acute cerebral insults are not at the forefront of the strategy of physicians. The presence of NPE should be high on the list of diagnoses when patients with central neurologic injury suddenly become dyspneic or present with a decreased P(a)o(2)/F(i)o(2) ratio. The associated mortality rate is high, but recovery is usually rapid with early and appropriate management. The treatment of NPE should aim to meet the oxygenation needs without impairing cerebral hemodynamics, to avoid pulmonary worsening and to treat possible associated myocardial dysfunction. During brain death, NPE may worsen myocardial dysfunction, preventing heart harvesting.

Cardiopulmonary complications of brain injury

Cardiac and pulmonary complications following acute neurologic injury are common and may be a cause of morbidity and mortality in this population. Examples include hypertension, arrhythmias, ventricular dysfunction, pulmonary edema, shock, and sudden death. Primary neurologic events are represented by stroke, subarachnoid hemorrhage, traumatic brain injury, epilepsy, and encephalitis and have been frequently reported. Given the high frequency of these conditions, it is important for physicians to become familiar with their pathophysiology, allowing for more prompt and appropriate treatment.