Experimental neurogenic pulmonary edema Part 2: The role of cardiopulmonary pressure change

Neurogenic pulmonary edema and Takotsubo cardiomyopathy in aneurysmal subarachnoid hemorrhage

PURPOSE

Neurogenic pulmonary edema (NPE) combined with Takotsubo cardiomyopathy (TCM) is a rare condition associated with aneurysmal subarachnoid hemorrhage (aSAH). Although several mechanisms have been proposed, the pathophysiology and management strategies are not yet fully established. We aimed to determine the radiological and clinical outcomes of patients with NPE and with TCM after aSAH to propose management strategies.

METHODS

We analyzed the data of 564 patients with aSAH recorded at a single medical center from February 2015 to July 2022. This study retrospectively investigated the incidence and demographics of SAH combined with both NPE and TCM and the clinical outcomes of the patients. Correlating factors, independently associated with NPE-TCM, were also investigated.

RESULTS

During the 7 years, 11 (2.0%) of 564 patients had NPE complicated with TCM after aSAH. Seven of 11 (63.6%) patients had poor-grade SAH (Hunt-Hess Grade 4 to 5). Three of 11 patients had a posterior circulation in the NPE-TCM group. The most prevalent treatment option was endovascular coil embolization, except for one case of clip. Long-term outcomes were favorable in 6 of 11 patients, and there was one case of mortality. Age, troponin I level, and alveolar-arterial oxygen gradient were correlating factors of NPE-TCM.

CONCLUSION

Although NPE-TCM represents a rare complication associated with aSAH, achieving active resolution of underlying neurological causes through early and appropriate treatment may contribute to a favorable prognosis. Considering the limited incidence of SAH complicated with NPE-TCM, a multi-center study may be needed.

Non-cardiogenic pulmonary edema complicating electroconvulsive therapy: short review of the pathophysiology and diagnostic approach

Acute pulmonary edema complicating electroconvulsive therapy is an extremely uncommon event that has rarely been described in the literature. Different theories, including one suggesting a cardiogenic component, have been proposed to explain its genesis. The present report describes a classic presentation of this condition with review of its potential mechanisms and diagnostic approach. After successful completion of a session of electroconvulsive therapy, a 42-year-old woman with major depressive disorder developed acute systemic high blood pressure, shortness of breath, and hemoptysis. A chest radiograph demonstrated diffuse bilateral pulmonary infiltrates. Initially cardiogenic pulmonary edema was presumed, but an extensive diagnostic work-up demonstrated normal systolic and diastolic left ventricular function, and with only supportive measures, a complete clinical and radiographic recovery was achieved within 48 hours. The present case does not support any cardiogenic mechanism in the genesis of this condition.

Histopathological features of the brain, liver, kidney and spleen following an innovative polytrauma model of the mouse

OBJECT

Among the various introduced experimental traumatic brain injury models, there is a clear paucity of proper experimental polytrauma models. To overcome this experimental gap we introduced such a polytrauma model in the mouse including traumatic brain injury. Here, we report on the histopathological features of the brain, lung, kidney, spleen and liver.

MATERIALS AND METHODS

20 male C57BL mice with a mean weight of 23 g were anesthetized with ketamine and xylazine. The anaesthetized animals were subjected to a controlled cortical impact (CCI) over the left parieto-temporal cortex using rounded-tip impounder for application of a standardized brain injury. Following fracture of the right femur using a guillotine, a volume-controlled hemorrhagic shock was induced. The control groups included animals with CCI only (n=20) and animals with femur fracture plus hemorrhagic shock without CCI (n=20). Subjects were sacrified at 96 h following trauma. Brain, lung, kidney, spleen and liver of the animals underwent histopathological examinations.

RESULTS

The mortality rate at 96 h was 25% in the polytrauma group versus 10% in the control groups. Within the histopathological investigations, polytraumatized animals differ from those with a single trauma (traumatic brain injury or femur fracture with hemorrhagic shock) with various severity.

CONCLUSION

The findings of this study show that such a polytrauma model can be standardized resulting in a reproducible damage. This model fulfills the requirements of a standardized animal model. It allows adequate analogies and inferences to the clinical situation of a polytrauma in humans.

The presence of the adult respiratory distress syndrome does not worsen mortality or discharge disability in blunt trauma patients with severe traumatic brain injury

PURPOSE

To evaluate the prevalence of the acute respiratory distress syndrome (ARDS) among blunt trauma patients with severe traumatic brain injury (TBI) and to determine if ARDS is associated with higher mortality, morbidity and worse discharge outcome.

METHODS

Blunt trauma patients with TBI (head abbreviated injury score (AIS)> or =4) who developed predefined ARDS criteria between January 2000 and December 2004 were prospectively collected as part of an ongoing ARDS database. Each patient in the TBI+ARDS group was matched with two control TBI patients based on age, injury severity score (ISS) and head AIS. Outcomes including complications, mortality and discharge disability were compared between the two groups.

RESULTS

Among 362 TBI patients, 28 (7.7%) developed ARDS. There were no differences between the two groups with respect to age, sex, ISS, Glasgow coma score (GCS), head, abdomen and extremity AIS. The TBI+ARDS group had significantly more patients with chest AIS> or =3 (57.1% versus 32.1%, p=0.03). There was no difference with respect to overall mortality between the TBI+ARDS group (50.0%) and the TBI group (51.8%) (OR 0.79: 95% CI 0.31-2.03, p=0.63). There was no significant difference with respect to discharge functional capacity between the two groups. There were significantly more overall complications in the TBI+ARDS group (42.9%) compared to the TBI group (16.1%) (OR 3.66: 95% CI 1.19-11.24, p=0.02). The TBI+ARDS group had an overall mean intensive care unit (ICU) length of stay of 15.6 days, versus 8.4 days in the TBI group (p<0.01). The TBI+ARDS group had significantly higher hospital charges than the TBI group ($210,097 versus $115,342, p<0.01).

CONCLUSION

The presence of ARDS was not associated with higher mortality or worse discharge disability. It was, however, associated with higher hospital morbidity, longer ICU and hospital length of stay.

Mechanism of cerebral fat embolism in subarachnoid hemorrhage: An experimental study

Subarachnoid hemorrhage (SAH) may cause neurogenic pulmonary edema (NPE), and chylomicron metabolism may be destroyed in injured lungs. We aimed to investigate the effect of neurogenic pulmonary edema (NPE), if present, on the development of cerebral fat embolism. This study has been conducted on 20 rabbits. Experimental SAH has been applied to half of the animals by injecting homologous blood into the cisterna magna, and the remaining half was applied only isotonic saline solution in the same manner under general anesthesia. After 20 days, all animals were killed. Their lungs and brains were examined histopathologically. Six animals died of SAH between 16 and 20 days, and foamy hemorrhagic parenchymal lesions and intra-alveolar hemorrhage were observed in their lungs. Fat globules were abundantly found in cerebral arteries of six of all the non-surviving animals. But, minimal histopathological changes were found in the lungs and brains of the surviving animals. Cerebral fat embolism was detected in only one animal that was given isotonic solution. SAH may cause NPE and result in lung tissue destruction. Chylomicron metabolism may be disordered in the destructed lungs and leakage of chylomicrons into systemic circulation may be facilitated via destroyed lung barrier. These pathologic processes may lead to cerebral fat embolism.

High-Frequency Percussive Ventilation: An Alternative Mode of Ventilation for Head-Injured Patients With Adult Respiratory Distress Syndrome

BACKGROUND

Adult respiratory distress syndrome develops in up to 20% of patients with severe head injury. This complicates the treatment of head-injured patients because lung-protective strategies such as high positive end-expiratory pressure (PEEP) and permissive hypercapnia may increase intracranial pressure (ICP) and reduce cerebral perfusion pressure. The use of high-frequency percussive ventilation (HFPV) is an alternate mode of ventilation that may improve oxygenation for head-injured patients while also lowering ICP.

METHODS

Clinical data were collected retrospectively over a 1-year period. Patients were included if they had a severe traumatic brain injury with a Glasgow Coma Score (GCS) of 8 or lower, a ventriculostomy drain for ICP measurement and cerebral spinal fluid drainage, and adult respiratory distress syndrome. Patients were switched from conventional mechanical ventilation to HFPV at the discretion of the attending trauma surgeon. Data for partial pressure of oxygen to fraction of inspired oxygen (PF) ratio, peak inspiratory pressure (PIP), ICP, partial pressure of carbon dioxide level (PCO2), PEEP, and mean airway pressure were compared before and then 4 and 16 hours after institution of HFPV therapy.

RESULTS

A total of 10 patients met study criteria. Data were expressed as mean +/- standard error. There was an increase in PF ratio (91.8 +/- 13.2 vs. 269.7 +/- 34.6; p < 0.01), PEEP (14 +/- 2.5 vs. 16 +/- 3.5), and mean airway pressure (20.4 +/- 4.8 vs. 23.6 +/- 6.8) 16 hours after institution of HFPV. There was a decrease in ICP (30.9 +/- 3.4 vs. 17.4 +/- 1.7; p < 0.01), PC02 (37.7 +/- 4.1 vs. 32.7 +/- 1.1; p < 0.05), and PIP (49.4 +/- 10 vs. 41 +/- 7.9; p < 0.05) at 16 hours. Overall mortality was 10%.

CONCLUSIONS

Therapy with HFPV produced a significant improvement in oxygenation with a concomitant reduction in ICP during the first 16 hours. This therapy may represent an important new method for the management of adult respiratory distress syndrome among head-injured trauma patients, although the long-term outcome of HFPV still needs evaluation.

Pulmonary transplantation: the role of brain death in donor lung injury

The paucity of suitable lung donors and the high early mortality as the result of primary graft failure remain major challenges in pulmonary transplantation. There is evidence that the lung is injured in the donor by the process of brain death and often is made unusable or fails posttransplantation after amplification of the injury by the process of ischemia-reperfusion. An understanding of the mechanism of donor lung injury could lead to the development of new treatment strategies for the donor to reduce lung injury, increase the number of donors with acceptable lungs, and improve the results of transplantation. The pathophysiology of brain death is complex and involves sympathetic, hemodynamic, and inflammatory mechanisms that can injure the lung. The literature is reviewed, and these mechanisms are discussed together with their possible interrelations.

Adult respiratory distress syndrome: a complication of induced hypertension after severe head injury

OBJECT

The factors involved in the development of adult respiratory distress syndrome (ARDS) after severe head injury were studied. The presence of ARDS complicates the treatment of patients with severe head injury, both because hypoxia causes additional injury to the brain and because therapies that are used to protect the lungs and improve oxygenation in patients with ARDS can reduce cerebral blood flow (CBF) and increase intracranial pressure (ICP). In a recent randomized trial of two head-injury management strategies (ICP-targeted and CBF-targeted), a fivefold increase in the incidence of ARDS was observed in the CBF-targeted group.

METHODS

Injury severity, physiological data, and treatment data in 18 patients in whom ARDS had developed were compared with the remaining 171 patients in the randomized trial in whom it had not developed. Logistic regression analysis was used to study the interaction of the factors that were related to the development of ARDS. In the final exact logistic regression model, several factors were found to be significantly associated with an increased risk of ARDS: administration of epinephrine (5.7-fold increased risk), administration of dopamine in a larger than median dose (10.8-fold increased risk), and a history of drug abuse (3.1-fold increased risk).

CONCLUSIONS

Although this clinical trial was not designed to study the association of management strategy and the occurrence of ARDS, the data strongly indicated that induced hypertension in this high-risk group of patients is associated with the development of symptomatic ARDS.

Neurogenic pulmonary oedema

Neurogenic pulmonary oedema is a relatively rare but significant complication of head injury. A case is described and the presentation, pathophysiology, and management are discussed.

Alterations in plasma concentrations of natriuretic peptides and antidiuretic hormone after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Hyponatremia is a common complication after subarachnoid hemorrhage. In this study we investigated the relations among hyponatremia, plasma natriuretic peptides, and antidiuretic hormone concentrations after subarachnoid hemorrhage.

METHODS

Blood samples for radioimmunoassay measurement of plasma brain natriuretic peptide-like immunoreactivity, atrial natriuretic peptide-like immunoreactivity, and antidiuretic hormone were obtained every 2 to 4 days until day 14 after subarachnoid hemorrhage.

RESULTS

Eleven of 20 patients with verified subarachnoid hemorrhage demonstrated mild hyponatremia (126 mEq/L < serum sodium < 135 mEq/L) during their clinical course. Atrial natriuretic peptide and antidiuretic hormone concentrations were significantly elevated on days 0 to 2 after onset of subarachnoid hemorrhage. Atrial natriuretic peptide concentrations remained high in patients who developed mild hyponatremia on days 6 to 14 after onset of subarachnoid hemorrhage. In contrast, antidiuretic hormone concentrations became significantly lower during the second week in these patients.

CONCLUSIONS

Mild hyponatremia after subarachnoid hemorrhage may be attributable not to the syndrome of inappropriate secretion of antidiuretic hormone but to cerebral salt-wasting syndrome. Atrial natriuretic peptide may be a causal natriuretic factor in cerebral salt-wasting syndrome.

Effect of neonatal capsaicin treatment on neurogenic pulmonary edema from fluid-percussion brain injury in the adult rat

The frequent occurrence of acute death from pulmonary failure in experimental head injury studies on Sprague-Dawley rats prompted an investigation into the manner in which acute neurogenic pulmonary edema develops in these animals as a result of an applied fluid pressure pulse to the cerebral hemispheres. Studies were performed in adult animals using histamine H1 and H2 blocking agents, or in adult animals treated as neonates with capsaicin to destroy unmyelinated C-fibers. Recordings were made of either the pulmonary arterial or the right ventricular pressure, and the left atrial and femoral arterial pressures before, during, and after injury to provide a record of the hemodynamic response throughout the development of neurogenic pulmonary edema. Head injury triggered the almost immediate development of pressure transients with and without neurogenic pulmonary edema. All rats, regardless of treatment, reacted with nearly identical systemic arterial pressure responses; however, the pulmonary responses followed a time course that was independent of systemic arterial pressure changes. Acute neurogenic pulmonary edema was always associated with a substantial increase in pulmonary arterial and left atrial pressures; conversely, pressure increases of similar magnitude were not always associated with edema. Histamine H1 and H2 blockers significantly reduced the pulmonary pressure surges only in rats free of neurogenic pulmonary edema. All capsaicin-treated rats showed suppressed pulmonary pressure responses, normal lung water content, elevated lung surface tension, and significantly reduced levels of immunoreactive substance P in the spinal cord and vagus nerve. While the pressures cannot clarify how edema influences the observed hemodynamics, they do not support the view that edema is the direct consequence of pulmonary hypertension. It is proposed that neurogenic pulmonary edema is a functional disturbance provoked by adverse stimuli from outside the lungs and that in the rat the primary afferent fiber is essential to the production of this entity.

Early changes of intracranial pressure, perfusion pressure, and blood flow after acute head injury. Part 1: An experimental study of the underlying pathophysiology

The present study examines intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebral circulation immediately after experimental head injury in an animal model. The underlying systemic hemodynamic changes were also observed. To produce a standardized head injury, a fluid-percussion device was applied to the dura at the midline of 10 piglets. Seven other nontraumatized animals served as a control group. Hemodynamic parameters as well as ICP and CPP were recorded on-line, one value every 1.4 seconds. Cerebral blood flow (CBF) and cerebral vascular resistance (CVR) were measured three times using a microsphere technique. Immediately after head injury, the traumatized animals showed a sudden increase in ICP, with a maximum of 40 torr at 3 to 5 minutes, while there was a pronounced decrease in CPP from 85 to 40 torr. The CBF in the various brain areas fell from 55 to 22 ml/min/100 gm within 5 minutes after the impact, and CVR increased to 300% of control values within 90 minutes. The findings of this study demonstrated that cerebral circulation is critically jeopardized within a few minutes after trauma. This, in combination with a subsequent increase in CVR, makes the early development of ischemic brain damage very likely. In traumatized patients, treatment prior to hospital admission must therefore be directed at prevention of this fatal course.

Pathophysiology of pulmonary edema following experimental brain death in the chacma baboon

Systemic and pulmonary hemodynamics have been studied during the induction of brain death in the chacma baboon. In 11 animals brain death was induced by acute intracranial hypertension. Continuous recording of blood flow through both the pulmonary artery and the aorta was obtained by electromagnetic flow meters placed around these vessels. Mean arterial, central venous, pulmonary arterial, and left atrial pressures were recorded continuously. Systemic and pulmonary vascular resistances were calculated. During the agonal period marked sympathetic activity occurred, with significant increases in circulating catecholamines and systemic vascular resistance. The great increase in systemic resistance resulted in acute left ventricular failure. Mean left atrial or pulmonary capillary wedge pressure rose above the mean pulmonary arterial pressure in 9 animals. As the systemic vascular resistance rose, a significant difference between pulmonary artery and aortic blood flows occurred, leading to blood pooling within the lungs. A mean of 72% of the total blood volume of the animal accumulated within these organs. The increase of left atrial pressure to levels higher than pulmonary artery pressure indicated a state of pulmonary capillary blood flow arrest. This, associated with the blood pooling within the lungs, almost certainly resulted in disruption of the anatomic integrity of the pulmonary capillaries (blast injury); 4 animals developed pulmonary edema, with alveolar septal interstitial hemorrhage.

Pulmonary lymphatic flow alterations during intracranial hypertension in sheep

The role of intracranial hypertension in the genesis of neurogenic pulmonary edema was studied in 25 sheep; cardiopulmonary hemodynamics (aortic, pulmonary arterial, and left atrial pressures and cardiac output) and fluid and protein movement across the pulmonary capillary bed (efferent pulmonary lymph flow and lymph/plasma protein ratio) were monitored. Only when intracranial pressure was raised to equal the baseline mean systemic pressure (75 to 120 Torr) did we observe the expected Cushing response of increased aortic pressure, or any alteration in pulmonary hemodynamics or fluid movement. When pulmonary changes did occur, they included an increase in pulmonary arterial pressure of between 5 and 15 Torr without any notable rise in left atrial pressure, and a sustained doubling of the pulmonary lymph flow with no dilution of the lymph/plasma protein ratio. In 3 additional animals cerebral ischemia alone produced an elevation in systemic pressure (74 Torr over baseline) without change in pulmonary arterial pressure, left atrial pressure, or pulmonary lymph flow. Thus, intracranial hypertension and ischemia both affect systemic pressure, but only the elevated intracranial pressure is followed by changes in the pulmonary circuit. We suggest that these changes in pulmonary vascular pressure, independent of changes in left atrial pressure, produce increased pulmonary transcapillary fluid flux that may result in neurogenic pulmonary edema.

Neurogenic pulmonary edema associated with autonomic dysreflexia

Neurogenic pulmonary edema is associated with a variety of central nervous system injuries and results from a massive centrally mediated sympathetic discharge. Another syndrome characterized by sympathetic overactivity is autonomic dysreflexia, which occurs in patients with spinal cord injury above T4 to T6. We describe a patient with a cervical spinal cord injury who had intense, prolonged autonomic dysreflexia following external sphincterotomy, which culminated in pulmonary edema. Traction on an over-inflated Foley catheter balloon was the stimulus for autonomic dysreflexia and deflation of the balloon resulted in prompt resolution of autonomic dysreflexia and pulmonary edema. The pathophysiology of neurogenic pulmonary edema and autonomic dysreflexia is discussed.