Moyamoya disease - a review of clinical experience and anaesthetic management

Moyamoya disease is a rare neurovascular condition that affects both children and adults. Increasingly these patients present for surgical management to improve the cerebral circulation since medical therapy is essentially ineffective. Because of the precarious cerebral circulation, these patients represent an anaesthetic challenge. In this report we review the pathophysiology of moyamoya disease, summarize our experience with seven patients and discuss the anaesthetic management.     

Middle Cerebral Artery Stenosis: Endovascular and Surgical Options

Atherosclerotic middle cerebral artery stenosis is a rare but potentially devastating cause of cerebral ischemia and stroke. While medical management remains the mainstay for stroke prevention, surgical and/or endovascular intervention is indicated in selected patients. This article reviews the role of surgery and endovascular techniques in the treatment of middle cerebral artery stenosis based on its natural history, pathophysiology, and prognosis when treated medically.     

Cognitive dysfunction after cardiac surgery: revisiting etiology

Cognitive dysfunction remains a frequent complication of cardiac surgery. Despite many years of research, few preventive strategies and no definitive therapeutic options exist for the management of this troublesome clinical problem. This shortcoming may be secondary to an incomplete understanding of the pathophysiology and etiology of cognitive loss after cardiac surgery; a better understanding of the etiology is essential to finding new therapies. The etiology of cognitive dysfunction after cardiac surgery is multifactorial and includes cerebral microembolization, global cerebral hypoperfusion, systemic and cerebral inflammation, cerebral temperature perturbations, cerebral edema, and possible blood-brain barrier dysfunction, all superimposed on genetic differences in patients that may make them more susceptible to injury or unable to repair from injury once it has occurred. This review expands on these potential etiologies in detailing the evidence for their existence.     

Perioperative stroke: the noncardiac surgery patient

This chapter reviewed the mechanisms and manifestations of transient and irreversible cerebral ischemia and the current experimental approaches to attenuate ischemic neuronal injury. Patients with signs or symptoms of cerebral ischemia are likely to have abnormal cerebrovascular dynamics, with areas of cerebrum at risk, and may be at an increased risk of stroke after general or vascular surgery. Such patients also have a very high frequency of associated cardiac disease. In this chapter, guidelines for anesthetic management of patients with symptomatic CVD undergoing noncardiac surgery were based on current understanding of the pathophysiology of cerebral ischemia. Nonetheless, the available data indicate that most perioperative strokes occur in the postoperative period and appear to be thromboembolic in nature. The existence of neither asymptomatic carotid bruits nor intraoperative hypotension appears to be associated with the occurrence of perioperative stroke.     

Management of subarachnoid haemorrhage

Subarachnoid haemorrhage is an acute life-threatening neurosurgical emergency affecting all ages and causing high mortality and morbidity. The rupture of an aneurysm of an intracranial artery at a point of turbulent blood flow within the circle of Willis usually causes it. Diagnosis begins with a non-contrast CT of the head, followed by more definitive angiography. The focus after diagnosis is to minimize further neurological injury called secondary injury. Initial stabilization with an ABCDEF approach should focus on maintaining adequate cerebral oxygenation and cerebral perfusion pressure (CPP). In emergent cases, this may require intubation and mechanical ventilation. Transfer to a specialist neuroscience centre for ongoing management is the next priority. Culprit aneurysms should be secured promptly by endovascular coiling or surgical clipping. Anaesthesia for either clipping or coiling must be neuroprotective. Recognition and management of complications are best undertaken in a centre managing high volumes of these patients. Vasospasm and delayed cerebral ischaemia are common and feared complications of subarachnoid haemorrhage. All patients should be given nimodipine for prophylaxis and management of these complications. Future research into the pathophysiology of the injured brain in SAH can guide us to novel therapies.     

Management of anesthesia for the multiply-injured patient with associated craniocerebral injuries

Adequate anaesthesiological care of polytraumatized patients with associated craniocerebral trauma has the primary objective of preventing secondary cerebral damage. To this end, it is absolutely necessary to be aware of the physiology and pathophysiology of intracranial pressure, cerebral perfusion pressure and cerebral blood flow. The effects on these parameters of physiological feedback parameters, as well as anaesthesiological measures and the drugs used, are discussed.     

Perioperative ischemic stroke in non-cardiovascular surgery patients

Perioperative ischemic stroke occurs in approximately 0.08–0.7% of patients after non-cardiovascular surgery and confers a significant risk of morbidity and mortality. The mortality rate of this major complication is similar in non-cardiovascular and cardiovascular surgery. Its incidence appears to be similar in Japan, Europe, and the United States. Perioperative physicians should be aware of the pathophysiology and predictors of ischemic stroke, and the anti-thrombotic strategies to prevent it. The main causes of perioperative ischemic stroke include cerebral atherothrombosis; lacuna stroke; cardiac thrombi due to atrial fibrillation; dehydration; hypotension; and perioperative systemic hypercoagulability. Perioperative management includes detailed informed consent regarding potential stroke risks, counseling, careful surgical treatment decisions, and identification of the high-risk patient for perioperative antithrombotic strategies. The 2009 Japanese guidelines for the management of stroke recommend using the appropriate intravenous infusions to avoid dehydration and consideration of anticoagulation in the patients who are at high risk for thrombosis and embolism while antithrombotic agents are discontinued. Understanding how to prevent perioperative ischemic stroke remains a challenge. In this article, we review the incidence, timing of the occurrence, mortality, risk factors, and pathophysiology of perioperative ischemic stroke in the non-cardiovascular surgery patient.     

Spontaneous intracerebral hemorrhage: epidemiology,pathophysiology, and medical management

This article introduces the basic epidemiology of intracerebral hemorrhage (ICH) and discusses the current available literature on the pathophysiology of primary ICH, hematoma enlargement, and cerebral edema. The article also includes a brief presentation of the basic steps regarding initial ICH management is presented as a framework for patient care.     

Imaging after brain injury

Head injury remains an important cause of death and disabilityin young adults. This review will discuss the role of structuralimaging using computed tomography (CT) and magnetic resonanceimaging (MRI) and physiological imaging using CT perfusion,¹³¹Xe CT, MRI and spectroscopy (MRS), single photon emissioncomputed tomography, and positron emission tomography (PET)in the assessment, management, and prediction of outcome afterhead injury. CT allows rapid assessment of brain pathology whichensures patients who require urgent surgical intervention receiveappropriate care. Although MRI provides greater spatial resolution,particularly within the posterior fossa and deep white matter,a complete assessment of the burden of injury requires imagingof cerebral physiology. Physiological imaging techniques canonly provide ‘snap shots’ of physiology within theinjured brain, but they can be repeated, and such data can beused to assess the impact of therapeutic interventions. Perfusionimaging based on CT techniques (xenon CT and CT perfusion) canbe implemented easily in most hospital centres, and providequantitative perfusion data in addition to structural images.PET imaging provides unparalleled insights into cerebral physiologyand pathophysiology, but is not widely available and is primarilya research tool. MR technology continues to develop and is becominggenerally available. Using a complex variety of sequences, MRcan provide data concerning both structural and physiologicalderangements. Future developments with such imaging techniquesshould improve understanding of the pathophysiology of braininjury and provide data that should improve management and predictionof functional outcome.     

From the macroscopic lesion to cellular ischemia

Traumatic brain injury (TBI) constitutes a major health and economic problem for developed countries, being one of the main causes of mortality and morbidity in children and young adults. Because of the immense importance and future consequences of TBI, the physician who sees a patient soon after brain injury must have a complete understanding of the pathophysiology and develop a practical knowledge of initial management of such patients. TBI may have intracranial and systemic effects that combine to give overall cerebral ischaemia. Injury to the nervous system is characterised by a stereotypic pattern, irrespective of the primary injury. The primary injury initiates a multitude of inflammatory cascades resulting in secondary brain injury, the effect of which is as important as the primary injury. This period of brain inflammation can last up to three weeks and renders the brain more susceptible to the effects of systemic insults such as hypotension, hypoxia and/or pyrexia. It has been shown in postmortem examination of patients dying from severe TBI that more than 90% had evidence of secondary ischaemic damage. The concept of 'cerebral protection' has been extended to encompass pretreatment of secondary injury. Preventing and treating cerebral ischaemia is the main goal of initial management of head-injured patients. Initial care focuses on achieving oxygenation, airway control and treatment of arterial hypotension.     

Repair of a cerebral artery aneurysm in a patient with persistent truncus arteriosus

We describe the anesthetic management of a 19-year-old woman with persistent truncus arteriosus who presented for cerebral artery aneurysm clipping. The anatomy and pathophysiology of persistent truncus arteriosus are reviewed to provide a basis for the choice of anesthetic agents and monitoring devices in this patient. The hazards of induced hypotension in the patient with truncus arteriosus are also discussed.     

Severe falciparum malaria in five soldiers from East Timor: a case series and literature review

Despite chemoprophylaxis, malaria remains a serious threat for large numbers of non-immune soldiers deployed in endemic areas. Five adult cases of severe falciparum malaria are reported. Three cases were complicated by multiorgan failure and one of these patients died from cerebral malaria. These cases serve to highlight issues, in an Australian intensive care unit, associated with the management of severe malaria, an uncommon disease in our country. The need for rapid diagnosis and commencement of appropriate treatment is paramount in preventing further morbidity and mortality. Understanding and management of malaria continues to evolve rapidly. The pathophysiology of acute lung injury, shock and brain injury associated with malaria are examined in light of recent research. This article discusses the current controversies of exchange blood transfusion and the use of the new artemisinin derivatives.     

Rare complications of pediatric diabetic ketoacidosis

The incidence of type 1 diabetes(T1D) among youth is steadily increasing across the world. Up to a third of pediatric patients with T1 D present with diabetic ketoacidosis, a diagnosis that continues to be the leading cause of death in this population. Cerebral edema is the most common rare complication of diabetic ketoacidosis in children. Accordingly, treatment and outcome measures of cerebral edema are vastly researched and the pathophysiology is recently the subject of much debate. Nevertheless, cerebral edema is not the onlysequela of diabetic ketoacidosis that warrants close monitoring. The medical literature details various other complications in children with diabetic ketoacidosis, including hypercoagulability leading to stroke and deep vein thrombosis, rhabdomyolysis, pulmonary and gastrointestinal complications, and long-term memory dysfunction. We review the pathophysiology, reported cases, management, and outcomes of each of these rare complications in children. As the incidence of T1 D continues to rise, practitioners will care for an increasing number of pediatric patients with diabetic ketoacidosis and should be aware of the various systems that may be affected in both the acute and chronic setting.     

Sodium abnormalities in the neurosurgical patient

The most frequently seen electrolyte disturbance in patients with central nervous system lesions involves sodium. This usually results from disturbed water regulation. Hyponatraemia and hypo-osmolality is found commonly in the neurosurgical population, particularly following subarachnoid haemorrhage. If inadequately managed, it can produce significant morbidity and mortality. Assessment of the clinical presentation and subsequent management requires a thorough understanding of the underlying pathophysiology. A diuretic and naturetic state develops with profound loss of both salt and water. Cerebral salt wasting is a clinical entity found in the neurosurgical intensive care unit. Its pathophysiology is still unclear, however, atrial natriuretic factor is probably involved. It is important that it is differentiated from the less-common syndrome of inappropriate antidiuretic hormone because fluid restriction in cerebral salt wasting can result in extracellular volume depletion and subsequent cerebral hypoperfusion, predisposing to ischaemic deficit with vasospasm. Avoidance of hypovolaemia is essential, and initially, the treatment is to replace the urine output with isotonic saline. However, if the urinary sodium concentration exceeds 150 mmol/l, then hypertonic (3%) saline becomes necessary. Symptomatic hyponatraemia is a medical emergency and should be managed aggressively in the intensive care unit. Rapid correction of hyponatraemia is safe provided the increase in serum sodium is not greater than 25 mmol/l in 48 h.Diabetes insipidus should be suspected in any neurosurgical patient who is polyuric. The findings are increased serum sodium and osmolality, and high volume, dilute urine. Careful fluid management is required, replacing urine output, and considering the hormone analogue DDAVP when urinary losses exceed 250 ml/h.     

Critical care management of severe head injury

Severe traumatic brain injury (TBI) is a significant cause of morbidity and mortality. The intensive care management of TBI requires a coordinated and comprehensive approach to treatment, including strategies to prevent secondary brain injury by avoidance of systemic physiological disturbances, such as hypotension, hypoxaemia, hypoglycaemia, hyperglycaemia and hyperthermia, and maintenance of adequate cerebral perfusion and oxygenation. There have been marked improvements in the management of patients with severe TBI over the last two decades, and treatment advances in the pre-hospital setting and emergency department have recently extended into the intensive care unit. The management of head injury has undergone extensive revision as evidence accumulates that established practices are not as effective or innocuous as previously believed. Management protocols have evolved with international consensus, providing guidelines that assist clinicians in delivering optimal care. Improved diagnostic and monitoring modalities are improving the understanding of the pathophysiology of head injury and allowing the delivery of individualised therapy.     

Neurologic complications of subarachnoid hemorrhage due to intracranial aneurysm rupture

The high rates of morbidity and mortality after subarachnoid hemorrhage due to spontaneous rupture of an intracranial aneurysm are mainly the result of neurologic complications. Sixty years after cerebral vasospasm was first described, this problem remains unsolved in spite of its highly adverse effect on prognosis after aneurysmatic rupture. Treatment is somewhat empirical, given that uncertainties remain in our understanding of the pathophysiology of this vascular complication, which involves structural and biochemical changes in the endothelium and smooth muscle of vessels. Vasospasm that is refractory to treatment leads to cerebral infarction. Prophylaxis, early diagnosis, and adequate treatment of neurologic complications are key elements in the management of vasospasm if neurologic damage, lengthy hospital stays, and increased use of health care resources are to be avoided. New approaches to early treatment of cerebral lesions and cortical ischemia in cases of subarachnoid hemorrhage due to aneurysm rupture should lead to more effective, specific management.     

Lessons learned from moyamoya disease: outcome of direct/indirect revascularization surgery for 150 affected hemispheres

Moyamoya disease is a chronic, occlusive cerebrovascular disease with unknown etiology characterized by bilateral steno-occlusive changes at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Recent advances in molecular biology and genetic research have provided better understanding of the pathophysiology of moyamoya disease, but surgical revascularization still remains the preferred treatment for this entity. The present study investigated the clinical course of 106 consecutive patients with moyamoya disease who underwent superficial temporal artery-middle cerebral artery anastomosis with indirect pial synangiosis in 150 hemispheres. The outcomes of surgery on the operated hemisphere were favorable, with no cerebrovascular event during the outpatient follow-up period (mean 58.4 months) in 89.3% (134/150). Two patients suffered hemorrhagic events on the operated hemisphere during the follow-up period (2/150, 1.33%), one of whom suffered deteriorated neurological status after hemorrhage. Despite the favorable long-term outcome, the incidence of temporary neurological deterioration due to cerebral hyperperfusion was 18.0% (27/150), but no patients suffered permanent neurological deterioration directly caused by hyperperfusion. In conclusion, direct/indirect revascularization surgery is a safe and effective treatment for moyamoya disease, although the issue of bleeding/re-bleeding remains to be solved. Postoperative cerebral hyperperfusion and peri-operative infarction are potential complications of this procedure, so we recommend intensive postoperative care and cerebral blood flow measurement in the acute stage, because the management of hyperperfusion is contradictory to that of ischemia.     

Physiological considerations important for the management of vasospasm.

The physiological mechanisms of known importance in the control of cerebral blood flow (CBF) and smooth muscle contraction and relaxation are reviewed. The pathophysiology of vasospasm following subarachnoid hemorrhage (SAH) is correlated with an alteration of these mechanisms. It is emphasized that smooth muscle relaxation is an energy-dependent process and that vasodilators require a functional smooth muscle membrane that may be severely impaired in ischemia or subarachnoid hemorrhage. The temporal profile of ischemia from spasm is correlated with the pathophysiology of altered metabolism of smooth muscle. The relevance of this complication to the timing of aneurysm surgery in 337 cases operated by one surgeon is considered along with various drug regimens suggested for its management.     

Pharmacological and pathological modulation of cerebral physiology

Anaesthesia for neurosurgery aims to provide optimal surgical conditions whilst maintaining adequate cerebral blood flow in order to supply the brain with appropriate amounts of oxygen and glucose. Most anaesthetic drugs influence the normal cerebral physiology either directly or indirectly. They can cause changes in cerebral blood flow by influencing cerebral blood vessel calibre, by interfering with autoregulatory processes and by modifying cerebral metabolism. The brain's limited ability to store oxygen and glucose means that its supply must be continuous if neuronal damage is to be avoided. Ischaemic cerebral damage is the most important pathological mechanism in patients with stroke, subarachnoid haemorrhage and traumatic brain injury. Significant traumatic brain injury causes widespread derangement of cerebral physiology, including changes in cerebral blood flow, autoregulation and cerebral energy dynamics. This article outlines the effect of anaesthesia on cerebral physiology and reviews the pathophysiology of traumatic brain injury and subarachnoid haemorrhage.     

Pharmacological and pathological modulation of cerebral physiology

Anaesthesia for neurosurgery aims to provide optimal operating conditions whilst at the same time maintaining adequate cerebral blood flow to supply the brain with appropriate supplies of oxygen and glucose. Many anaesthetic drugs can influence normal cerebral physiology either directly or indirectly. They can cause changes in cerebral blood flow by influencing cerebral blood vessel calibre, by interfering with autoregulatory processes and by modifying cerebral metabolism. The brain’s limited ability to store oxygen and glucose means that its supply must be continuous if neuronal damage is to be avoided. Ischaemic cerebral damage is the most important pathological mechanism in patients with stroke, subarachnoid haemorrhage and traumatic brain injury. Significant traumatic brain injury causes widespread derangement of cerebral physiology, including changes in cerebral blood flow, autoregulation and cerebral energy dynamics. This article outlines the effect of anaesthesia on cerebral physiology and reviews the pathophysiology of traumatic brain injury and subarachnoid haemorrhage.