Differing effects of vasopressin on regional cerebral blood flow of dogs following intracisternal vs. intra-arterial administration

Therapeutic potential of vasopressin in the treatment of neurological disorders

Vasopressin (VP) is a nonapeptide made of nine amino acids synthesized by the hypothalamus and released by the pituitary gland. VP acts as a neurohormone, neuropeptide and neuromodulator and plays an important role in the regulation of water balance, osmolarity, blood pressure, body temperature, stress response, emotional challenges, etc. Traditionally VP is known to regulate the osmolarity and tonicity. VP and its receptors are widely expressed in the various region of the brain including cortex, hippocampus, basal forebrain, amygdala, etc. VP has been shown to modulate the behavior, stress response, circadian rhythm, cerebral blood flow, learning and memory, etc. The potential role of VP in the regulation of these neurological functions have suggested the therapeutic importance of VP and its analogues in the management of neurological disorders. Further, different VP analogues have been developed across the world with different pharmacotherapeutic potential. In the present work authors highlighted the therapeutic potential of VP and its analogues in the treatment and management of various neurological disorders.

Reversible splenial lesion syndrome associated with lobar pneumonia: Case report and review of literature

BACKGROUND

Reversible splenial lesion syndrome (RESLES) is a rare clinico-radiological disorder with unclear pathophysiology. Clinically, RESLES is defined as reversible isolated splenial lesions in the corpus callosum, which can be readily identified by magnetic resonance imaging (MRI) and usually resolve completely over a period of time. RESLES could be typically triggered by infection, antiepileptic drugs (AEDs), poisoning, etc. More factors are increasingly recognized.

METHODS AND RESULTS

We reported herein an 18-year-old female patient with lobar pneumonia who developed mental abnormalities during hospitalization. An isolated splenial lesion in the corpus callosum was found by head MRI and the lesion disappeared 15 days later. Based on her clinical manifestations and radiological findings, she was diagnosed with lobar pneumonia associated RESLES. We further summarize the up-to-date knowledge about the etiology, possible pathogenesis, clinical manifestations, radiological features, treatment, and prognosis of RESLES.

CONCLUSION

This report contributes to the clinical understanding of RESLES which may present with mental abnormalities after infection. The characteristic imaging of reversible isolated splenial lesions in the corpus callosum was confirmed in this report. The clinical manifestations and lesions on MRI could disappear naturally after 1 month without special treatment.

Multiplicity of cerebrospinal fluid functions: New challenges in health and disease

This review integrates eight aspects of cerebrospinal fluid (CSF) circulatory dynamics: formation rate, pressure, flow, volume, turnover rate, composition, recycling and reabsorption. Novel ways to modulate CSF formation emanate from recent analyses of choroid plexus transcription factors (E2F5), ion transporters (NaHCO3 cotransport), transport enzymes (isoforms of carbonic anhydrase), aquaporin 1 regulation, and plasticity of receptors for fluid-regulating neuropeptides. A greater appreciation of CSF pressure (CSFP) is being generated by fresh insights on peptidergic regulatory servomechanisms, the role of dysfunctional ependyma and circumventricular organs in causing congenital hydrocephalus, and the clinical use of algorithms to delineate CSFP waveforms for diagnostic and prognostic utility. Increasing attention focuses on CSF flow: how it impacts cerebral metabolism and hemodynamics, neural stem cell progression in the subventricular zone, and catabolite/peptide clearance from the CNS. The pathophysiological significance of changes in CSF volume is assessed from the respective viewpoints of hemodynamics (choroid plexus blood flow and pulsatility), hydrodynamics (choroidal hypo- and hypersecretion) and neuroendocrine factors (i.e., coordinated regulation by atrial natriuretic peptide, arginine vasopressin and basic fibroblast growth factor). In aging, normal pressure hydrocephalus and Alzheimer's disease, the expanding CSF space reduces the CSF turnover rate, thus compromising the CSF sink action to clear harmful metabolites (e.g., amyloid) from the CNS. Dwindling CSF dynamics greatly harms the interstitial environment of neurons. Accordingly the altered CSF composition in neurodegenerative diseases and senescence, because of adverse effects on neural processes and cognition, needs more effective clinical management. CSF recycling between subarachnoid space, brain and ventricles promotes interstitial fluid (ISF) convection with both trophic and excretory benefits. Finally, CSF reabsorption via multiple pathways (olfactory and spinal arachnoidal bulk flow) is likely complemented by fluid clearance across capillary walls (aquaporin 4) and arachnoid villi when CSFP and fluid retention are markedly elevated. A model is presented that links CSF and ISF homeostasis to coordinated fluxes of water and solutes at both the blood-CSF and blood-brain transport interfaces.

OUTLINE

1 Overview2 CSF formation2.1 Transcription factors2.2 Ion transporters2.3 Enzymes that modulate transport2.4 Aquaporins or water channels2.5 Receptors for neuropeptides3 CSF pressure3.1 Servomechanism regulatory hypothesis3.2 Ontogeny of CSF pressure generation3.3 Congenital hydrocephalus and periventricular regions3.4 Brain response to elevated CSF pressure3.5 Advances in measuring CSF waveforms4 CSF flow4.1 CSF flow and brain metabolism4.2 Flow effects on fetal germinal matrix4.3 Decreasing CSF flow in aging CNS4.4 Refinement of non-invasive flow measurements5 CSF volume5.1 Hemodynamic factors5.2 Hydrodynamic factors5.3 Neuroendocrine factors6 CSF turnover rate6.1 Adverse effect of ventriculomegaly6.2 Attenuated CSF sink action7 CSF composition7.1 Kidney-like action of CP-CSF system7.2 Altered CSF biochemistry in aging and disease7.3 Importance of clearance transport7.4 Therapeutic manipulation of composition8 CSF recycling in relation to ISF dynamics8.1 CSF exchange with brain interstitium8.2 Components of ISF movement in brain8.3 Compromised ISF/CSF dynamics and amyloid retention9 CSF reabsorption9.1 Arachnoidal outflow resistance9.2 Arachnoid villi vs. olfactory drainage routes9.3 Fluid reabsorption along spinal nerves9.4 Reabsorption across capillary aquaporin channels10 Developing translationally effective models for restoring CSF balance11 Conclusion.

Cerebral metabolism assessed with microdialysis in uncontrolled hemorrhagic shock after penetrating liver trauma

In a porcine model of uncontrolled hemorrhagic shock, we evaluated the effects of fluid resuscitation versus arginine vasopressin (AVP) combined with hypertonic-hyperoncotic hydroxyethyl starch solution (HHS) on cerebral perfusion pressure (CPP) and on cerebral metabolism using intracerebral microdialysis. Sixteen anesthetized pigs were subjected to uncontrolled liver bleeding until hemodynamic decompensation, followed by resuscitation using either fluid (n = 8) or AVP/HHS (n = 8). Thirty minutes after drug administration, bleeding was controlled by manual compression, and colloid and crystalloid solutions were administered in both groups. All surviving animals were observed for one hour. After hemodynamic decompensation, fluid resuscitation resulted in a smaller increase of CPP than did AVP/HHS (mean +/- sem; 24 +/- 5 vs 45 +/- 7 mm Hg; P < 0.01). Mean (+/- sem) cerebral venous partial pressure of oxygen was significantly decreased (P < 0.01) 5 min after fluid compared with 5 min after AVP/HHS administration (36 +/- 3 vs 64 +/- 4 torr). Cerebral metabolism was comparable in both groups. In conclusion, AVP/HHS proved to be superior to fluid in the initial phase of therapy with respect to CPP and cerebral oxygenation, but was comparable to fluid regarding cerebral metabolism and secondary cell damage in surviving animals.

Arginine vasopressin reduces cerebral oxygenation and cerebral blood volume during intact circulation in swine---a near infrared spectroscopy study

BACKGROUND AND OBJECTIVE

The aim of the present study was to investigate the impact of arginine vasopressin (AVP), a drug currently under investigation for use during cardiopulmonary resuscitation, on cerebral oxygenation and cerebral blood volume (CBV) in pigs with intact systemic circulation using near infrared spectroscopy.

METHODS

Nine healthy pigs were anaesthetized and subjected to invasive haemodynamic monitoring as well as to non-invasive determination (with near infrared spectroscopy) of changes in the Tissue Oxygenation Index (TOI is the ratio of oxygenated to total tissue haemoglobin), Tissue Haemoglobin Index (THI, representing CBV) and cytochrome oxidase (deltaCytOx, representing the balance of intracellular oxygen supply).

RESULTS

At both 3 and 5 min after AVP administration, TOI, THI and deltaCytOx were significantly (P < 0.001) reduced compared to baseline, while cerebral perfusion pressure increased significantly (P < 0.001). The effects of AVP on TOI and THI lasted longer than on deltaCytOx. There were no significant changes with respect to the intracranial pressure throughout the study period.

CONCLUSIONS

No improvement of cerebral oxygenation was detected after AVP administration in swine with an intact systemic circulation. In contrast to recently published investigations, AVP provoked a sustained drop in indices of cerebral oxygenation and CBV.

Improved cerebral blood supply and oxygenation by aortic balloon occlusion combined with intra-aortic vasopressin administration during experimental cardiopulmonary resuscitation

BACKGROUND

Intravenous administration of vasopressin during cardiopulmonary resuscitation (CPR) has been shown to improve myocardial and cerebral blood flow. Aortic balloon occlusion during CPR may also augment myocardial and cerebral blood flow and can be used as a central route for the administration of resuscitative drugs. We hypothesized that, as compared with intravenously administered vasopressin, the administration of this drug above the site of an aortic balloon occlusion would result in a greater increase in cerebral perfusion and oxygenation during CPR and after restoration of spontaneous circulation (ROSC).

METHODS

Twenty piglets were subjected to 5 min of ventricular fibrillation followed by 8 min of closed-chest CPR and were treated with 0.4 U kg(-1) boluses of vasopressin intravenously (the IV-vasopressin group with sham aortic balloon) or above the site for an aortic balloon occlusion (the balloon-vasopressin group). The aortic balloon catheter was inflated in the latter group 1 min after commencement of CPR and was deflated within 1 min after ROSC. Systemic blood pressures, cerebral cortical blood flow, cerebral tissue pH and PCO2 were monitored continuously and the cerebral oxygen extraction ratio was calculated.

RESULTS

During CPR, arterial blood pressure and cerebral perfusion pressure were greater in the balloon-vasopressin group, as compared with the IV-vasopressin group. These pressures did not differ between the groups after ROSC. Cerebral cortical blood flow was not significantly greater in the balloon-vasopressin group during CPR, whereas significantly higher cortical blood flow levels were recorded after ROSC. Cerebral tissue pH decreased in the IV-vasopressin group during the post-resuscitation hypoperfusion period. In contrast, decreasing pressures during the hypoperfusion period did not result in increasing tissue acidosis in the balloon-vasopressin group.

CONCLUSIONS

During CPR, intra-aortic vasopressin combined with aortic balloon occlusion resulted in significantly greater perfusion pressures but not in greater cerebral cortical blood flow. After ROSC, however, a greater increase in cortical blood flow was recorded in the balloon-vasopressin group, even though the aortic balloon was deflated and perfusion pressures did not differ between the groups. This suggests that vasopressin predominantly gives vasoconstrictive effects on cerebral cortical vessels during CPR, but results in cerebral cortical vasodilatation after ROSC.