Pulmonary lymphatic flow alterations during intracranial hypertension in sheep

An Unusual Transudative Pleural Effusion Succeeded by Pulmonary and Brain Edema and Death

Here we report a 22-year old woman with massive and bilateral transudative effusion succeeded by pulmonary edema and brain edema and death. Investigations for systemic disorders were negative. Exacerbation of dyspnea after intravenous fluid infusion was a main problem. As effusion was refractory to medical treatment, the patient was referred for surgical pleurodesis and bilateral surgical pleurodesis were done separately. Postsurgically, dyspnea exacerbation occurred after each common cold infection. Vertigo and high intracranial pressure were also a problem postsurgically. CSF pressure was 225 mm/H₂O. Therapeutic lumbar puncture was done in two sequential weeks, and the patient was on acetazolamide 250 mg/trivise a day. Despite the medical treatment, progressive dyspnea, headache, and high intracranial pressure followed by death nine months after pleurodesis. As there is a gradient of pressure between pleura and CSF, after pleurodesis brain edema must be a consequence of inversing this gradient. In conclusion, when there are any abnormalities about fluid volume or pressure in any of these cavities, we have to study other cavities.

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.

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.

Subarachnoid hemorrhage

The medical and surgical management of aneurysmal SAH has changed dramatically in the past few decades. Surgical management emphasizes early triage and repair of the responsible aneurysm. Medical management focuses on maintenance of adequate volume, monitoring cerebral vasospasm, and initiation of medical maneuvers or interventional procedures designed to improve vessel patency and CBF. The results of these techniques have not been studied in randomized controlled trials; however, several large retrospective analyses reveal a significant decrease in mortality and morbidity with the institution of these measures. Future improvements will continue to develop with increased understanding of cerebral vasospasm and in neurologic monitoring.

Pulmonary edema after resection of a fourth ventricle tumor: possible evidence for a medulla-mediated mechanism

A well-recognized fact is that some patients may have development of pulmonary edema in association with disorders of the central nervous system. The origin of this phenomenon, known as neurogenic pulmonary edema, is unclear but may result, in part, from select pulmonary venoconstriction modulated by autonomic outflow from the medulla oblongata. We describe a 21-year-old man who had development of pulmonary edema in association with surgical resection of a brain tumor that was close to the medulla. Other than the possibility of medullary dysfunction, which could have occurred after surgical manipulation, no other risk factor for pulmonary edema was identified. Of note, the patient's blood pressure remained normal throughout the perioperative period, and no fluid overload or primary cardiac dysfunction was evident. This case supports the theory that the medulla is an important anatomic site of origin for neurogenic pulmonary edema and that alterations in medullary function can induce pulmonary edema in humans, independent of systemic hypertension.

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.

Neurologic emergencies

This article considers the rapid assessment and initial management of several neurologic emergencies--altered consciousness, increased intracranial pressure, stroke, status epilepticus, acute neurogenic respiratory failure, acute autonomic instability, the neuroleptic malignant syndrome, and spinal cord compression.

Nucleus tractus solitarius lesions elevate pulmonary arterial pressure and lymph flow

The effects of lesions of the nucleus tractus solitarius (NTS) on pulmonary vascular pressure and pulmonary lymph flow were investigated in 6 halothane-anesthetized sheep. After lesions of the NTS were created using bilateral thermocoagulation, pulmonary artery pressure rose to 150% of baseline and remained elevated for the 3-hour duration of the experiment. Systemic and left atrial pressures did not change. Pulmonary lymph flow doubled within 2 hours; the lymph-plasma protein ratio was unchanged from baseline. Sham NTS lesions and lesions lateral to NTS produced no changes. These experiments demonstrate that lesions of the central nervous system can alter pulmonary vascular pressures and transcapillary fluid flux independently of effects upon the systemic circulation. These findings may have relevance for the understanding of neurogenic pulmonary edema in humans.

Rapid change in pulmonary vascular hemodynamics with pulmonary edema during cardiopulmonary resuscitation

Previous studies have shown that pulmonary edema occurs in half of all pre-hospital cardiac arrest victims who cannot be successfully resuscitated and is a major cause of hypoxemia and poor lung compliance during resuscitation. Pulmonary vascular hypertension and elevation of pulmonary capillary wedge pressure have been observed during cardiac resuscitation in humans. To further define the time course of the pulmonary hemodynamic changes, pulmonary artery diastolic pressure (PAd) was measured on a computerized trend recorder prior to, during, and immediately after arrest in three adult patients. Prior to arrest, PADP was 20.9 +/- 3.1 mm Hg. The PADP rose in all three patients by an average of 30.6% after 5-10 minutes and 71.3% after 10-15 minutes of CPR. Peak PADP reached 35.8 +/- 5.1 mm Hg (difference from pre-arrest level significant, P less than 0.001). In both patients who were resuscitated successfully, the PADP returned to baseline within 5 minutes of effective spontaneous circulation. The finding that such hemodynamic changes occur rapidly during resuscitation and can reverse quickly with resumption of effective spontaneous circulation is consistent with the time course for the early development of pulmonary edema. Development of pulmonary edema many hours following successful resuscitation likely involves other mechanisms.