PubMed Health⌕ Search

Biomedical subjects

David J Blacker

Publications and source records attributed to David J Blacker.

15 recordsLinked to original sources
PubMed2005

Pulmonary function tests and blood gases in worsening myasthenia gravis.

The aim of this study was to determine whether pulmonary function tests have a role in predicting the need for ventilation support in myasthenia gravis. Medical records were reviewed for 42 patients with severe myasthenia gravis who required 55 admissions to the intensive care unit. Patients with a vital capacity of more than 20 ml/kg, a maximal expiratory pressure more than 40 cm H(2)O, or a maximal inspiratory pressure more negative than -40 cm H(2)O are unlikely to require mechanical ventilation. A decline of 30% or more in maximal inspiratory pressure predicted a group at higher risk of requiring mechanical or noninvasive ventilation. Hypercapnia was frequent and was more common in patients who required mechanical ventilation. Worsening of these pulmonary function and blood gas values in patients with myasthenia gravis may guide decisions about intubation and ventilatory support.

Blood Gas Analysis↗
PubMed2004

More than a pain in the neck: vertebral artery dissection and subarachnoid hemorrhage.

Intracranial vertebral artery dissection is an uncommon but important cause of subarachnoid hemorrhage. These patients have a predilection for early rebleeding that makes early diagnosis and intervention imperative. The arterial dissection and associated dissecting aneurysm are often located close to the origin of the posterior-inferior cerebellar artery. Endovascular treatment techniques have been increasingly employed. An illustrative case that was treated successfully with coils but complicated by a posterior-inferior cerebellar artery territory infarction is presented. The objectives are to highlight the clinical features of this condition and to describe the problems associated with treatment, particularly those related to the posterior-inferior cerebellar artery origin.

Embolization, Therapeutic↗
PubMed2004

The preoperative cerebrovascular consultation: common cerebrovascular questions before general or cardiac surgery.

All types of health care providers may be called on to evaluate the risk of ischemic stroke related to an upcoming surgical procedure, particularly in patients with established cerebrovascular disease. We outline possible mechanisms contributing to perioperative stroke, summarize available data on the stroke risk associated with selected surgeries, and highlight recognized risk factors. We then provide recommended answers to some of the questions commonly encountered at the preoperative cerebrovascular consultation: What is the appropriate time interval between a stroke and elective surgery? What is the perioperative stroke risk for patients with established carotid or vertebrobasilar large artery stenosis, and what are the cardiac implications of detecting a cerebrovascular large artery stenosis? Should patients with a large artery stenosis undergo prophylactic revascularization procedures before undergoing general surgery? What treatment is appropriate for patients with both coronary artery and carotid or vertebrobasilar large artery stenosis? What is the appropriate perioperative management of antiplatelet and anticoagulant medications with respect to stroke risk?

Anticoagulants↗
PubMed2004

Clinical characteristics and mechanisms of stroke after polytrauma.

OBJECTIVES: To describe the clinical characteristics of acute stroke attributable to trauma and to analyze the mechanisms and effect of stroke on outcome in patients with polytrauma. PATIENTS AND METHODS: We retrospectively reviewed the medical records of patients with polytrauma complicated by stroke at the Mayo Clinic in Rochester, Minn. The diagnosis of stroke was matched with trauma for the period between January 1, 1985, and December 31, 2001. Polytrauma was defined as at least 2 injuries that involve at least 1 vital organ (eg, lung or liver) and necessitate patient admission to a trauma intensive care unit. RESULTS: We identified 14 patients with polytrauma who had experienced a stroke (13 ischemic and 1 hemorrhagic). Craniocervical artery dissection was the most common mechanism (7 patients), and skull or facial fractures were a possible marker for this (5 of 7 patients). There were frequent delays in identifying stroke, with limb fracture on the side of the paresis (5 of 6 patients) being a possible factor. Four patients died of postischemic brain swelling, and 5 had major neurologic impairment. CONCLUSIONS: Stroke after polytrauma is due to various mechanisms, is frequently difficult to recognize early, and profoundly affects patient outcome.

Adult↗
PubMed2003

Stroke risk in anticoagulated patients with atrial fibrillation undergoing endoscopy.

OBJECTIVE: To determine the risk of stroke in anticoagulated patients with atrial fibrillation (AF) when anticoagulation is adjusted for bronchoscopy, gastroscopy, or colonoscopy, and to identify factors that could modify this risk. METHODS: The authors reviewed patients with AF undergoing endoscopies between 1995 and 2001, with specific analysis of patients with AF in whom anticoagulation was adjusted for the procedures. The authors calculated the stroke rate within 30 days of the procedures. RESULTS: Twelve strokes occurred in 987 patients undergoing 1,137 procedures (1.06%/procedure). The risk ranged from 0.31% for patients with nonvalvular AF undergoing routine procedures to 2.93% for complex patients undergoing endoscopies combined with other procedures or with comorbid illnesses. Patients with stroke were more likely to be complex (7/12 vs 219/975, p = 0.04); to be older than 80 years (6/12 vs 187/975, p = 0.017); to have a history of stroke (7/12 vs 194/975, p = 0.004), hypertension (10/12 vs 508/975, p = 0.04), or hyperlipidemia (9/12 vs 334/975, p = 0.005); or to have a family history of vascular disease (10/12 vs 502/975, p = 0.039). CONCLUSIONS: The risk of stroke in patients with AF whose anticoagulation is adjusted for endoscopies is low, but almost tenfold higher in patients with complex clinical situations. Age, history of stroke, hypertension, hyperlipidemia, and family history of vascular disease may increase the risk of stroke.

Age Factors↗
PubMed2003

Risk of ischemic stroke in patients with symptomatic vertebrobasilar stenosis undergoing surgical procedures.

BACKGROUND AND PURPOSE: There is little information to provide an estimate for stroke risk in patients with established stenosis or occlusion in the basilar or intracranial vertebral arteries undergoing surgical procedures. The objective of this study was to determine the ischemic stroke risk in this specific patient population. METHODS: A medical records linkage system retrospectively identified patients with a diagnosis of symptomatic vertebrobasilar stenosis or occlusion matched with surgical procedures. Patients were selected if they had stenosis or occlusion of the basilar or intracranial vertebral arteries identified on vascular imaging before undergoing surgical procedures under general anesthesia. Clinical and radiographic features were reviewed, along with the nature of the surgeries and details of the perioperative management. Records were reviewed for the diagnosis of stroke occurring within 1 month of surgery. RESULTS: Thirty-eight patients with a history of symptomatic vertebrobasilar ischemia underwent 50 operations under general anesthesia, and 3 had ischemic strokes in the vertebrobasilar territory immediately after surgery, a per-procedure rate of 6.0% (95% confidence interval, 1.2 to 16.6) All 3 had episodes of prolonged hypotension (systolic blood pressure <100 mm Hg for >10 minutes) during surgery. CONCLUSIONS: The risk of perioperative stroke in patients with vertebrobasilar stenosis undergoing surgery under general anesthesia is 6.0%, which is notably higher than the risk for patients with other patterns of cerebrovascular disease.

Adult↗
PubMed2003

A functional MRI protocol for localizing language comprehension in the human brain.

We describe a functional magnetic resonance imaging (fMRI) protocol to separate activation of areas in the brain associated with language comprehension from sensory areas activated as a result of the presentation of the language stimulus, by comparing cortical activation patterns during the presentation of similar or the same language stimulus via two different sensory modalities (auditory and visual), and identifying the regions of activation that are common to both modalities. The protocol can be implemented on any MR scanner capable of functional imaging, and has proven valuable for the reliable identification of the lateralization and location of language centres in patients being considered for neurosurgical procedures. As well, the method has potential for the study of cortical processing of auditory speech and written language in healthy subjects and in subjects suffering from language disorders.

Acoustic Stimulation↗
PubMed2003

In-hospital stroke.

Between 6.5% and 15.0% of all strokes occur in patients already in hospital, many of whom are there for surgical procedures or cardiac disorders. This important group of patients could potentially be assessed more rapidly than others and could be candidates for interventional therapies. However, delays in recognition and assessment are common, possibly related to comorbidities and the complexities of hospital practice. Risk factors for in-hospital stroke include specific operations and procedures (eg, cardiac surgery), previous medical disorders (especially a history of stroke), and certain physiological characteristics (including fever and dehydration). The stroke subtype is embolic in a large proportion, and there are various possible precipitating mechanisms. Outcome can be poor, with high mortality. Interventional therapies, particularly thrombolysis, are possible options. In the postoperative setting, intra-arterial thrombolysis is feasible and reasonably safe in carefully selected patients. Experimental agents and the manipulation of physiological variables are other treatment possibilities that could be applied early in this group of patients. Increasing the awareness by hospital physicians of such interventions may be an important factor that reduces delays in assessment of patients who have stokes while in hospital.

Humans↗
PubMed2003

Delayed complete bilateral ptosis associated with massive infarction of the right hemisphere.

OBJECTIVE: To characterize the phenomenon of complete bilateral ptosis associated with massive infarction of the right cerebral hemisphere, particularly with respect to its time course and relationship to herniation syndromes. PATIENTS AND METHODS: In May through July 2002, consecutive patients admitted to the neurology/neurosurgery intensive care unit at the Mayo Clinic in Rochester, Minn, with massive infarction of the right cerebral hemisphere, and later, complete bilateral ptosis, underwent serial neurologic examinations and neuroimaging. RESULTS: Six patients with massive infarction of the right cerebral hemisphere developed complete bilateral ptosis. All had normal eyelid opening at initial examination and later developed ptosis, which clearly preceded signs of herniation. Three patients died after herniation syndromes developed. In the 3 survivors, improvement in ptosis closely followed resolution of midbrain distortion seen on computed tomographic scans. CONCLUSION: The precise anatomical explanation for complete bilateral ptosis is unclear, but upper brainstem involvement seems most likely. Complete bilateral ptosis is a valuable clinical sign in patients with a massive hemispheric infarction that precedes herniation and could provide an opportunity for early intervention.

Adult↗