Antithrombotic and thrombolytic therapy for ischemic stroke

Antithrombotic and thrombolytic agents form the cornerstone of stroke prevention and treatment. Large, randomized trials have also highlighted the effectiveness and safety of early and continuous antiplatelet therapy in reducing atherothrombotic stroke recurrence. Aspirin is the antiplatelet treatment standard against which several other antiplatelet agents (ticlopidine, clopidogrel, aspirin-dipyridamole) have been shown to be more effective. The prevention of cardioembolic stroke is best accomplished with oral anticoagulation, barring any contraindications. The thrombolytic agent, rt-PA, improves outcome in ischemic stroke patients treated within 3 hours of onset. The risk-benefit ratio is narrow because of an increased risk for bleeding but studies do not support a higher risk in the geriatric population.

Cushing’s Contributions to Neuroscience, Part 1: Through the Looking Glass

Harvey Cushing (1869-1939) played a pivotal role in the birth of modern neurosurgery. At the turn of the century, when he was completing his surgical residency, medicine was just beginning to embrace scientific investigation as the main tool to diagnose and treat disease. Touring Europe after residency landed him in the laboratory of the great scientist Theodor Kocher, with whom he developed a modern understanding of the effects of increased intracranial pressure. This achievement helped Cushing transform neurosurgery into a viable specialty. An analysis of this early work in neuroscience reveals the ambition, ingenuity, and self-assurance of a budding scientist struggling to achieve recognition. This is the first of two reports on Cushing’s contributions to neuroscience.

The novel beta-blocker, carvedilol, provides neuroprotection in transient focal stroke

Increasing evidence supports a role for oxidative stress, proinflammatory cytokines, and apoptosis in the pathophysiology of focal ischemic stroke. Previous studies have found that the multi-action drug, carvedilol, is a mixed adrenergic antagonist, and that it behaves as an antioxidant and inhibits apoptosis. In the current study, the authors investigated whether carvedilol provides protection in focal cerebral ischemia and whether this protection is associated with reduced apoptosis and the downregulation of the inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin- 1beta (IL-1beta). Male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) by an intraluminal filament technique. Carvedilol (1, 3, and 10 mg/kg) was injected daily subcutaneously 2 or 4 days before the induction of ischemia. Neurologic scores, infarct volumes, TUNEL staining, and mRNA levels of TNF-alpha and IL-1beta were assessed at 24 hours reperfusion. The effect of carvedilol on microvascular cortical perfusion was studied with continuous laser-Doppler flowmetry. Twenty-four hours after MCAO, carvedilol at all three doses reduced infarct volumes by at least 40% and reduced neurologic deficits on average by 40% compared with vehicle-treated controls when given 2 or 4 days before the induction of ischemia. This protection was not mediated by changes in temperature or blood flow. Treatment with all three dose regimens resulted in fewer TUNEL positive cells compared with controls. At 24 hours reperfusion, carvedilol decreased TNF-alpha and IL-1beta expression by 40% to 50% in the ipsilateral ischemic cortex compared with the contralateral controls. The results of the current study indicate that carvedilol is neuroprotective in focal cerebral ischemia and may protect the ischemic brain by inhibiting apoptosis and attenuating the expression of TNF-alpha and IL-1beta.

Leukemia inhibitory factor requires concurrent p75LNTR signaling to induce apoptosis of cultured sympathetic neurons

Apoptosis may result either from positive induction by ligand binding to a plasma membrane receptor or from negative induction attributable to loss of a suppressor signal. For example, apoptosis of developing sympathetic neurons may be induced in culture either by exposure to leukemia inhibitory factor (LIF) or by deprivation of nerve growth factor. This study compared the cell death pathways activated in sympathetic neurons by these two different stimuli. Both types of cell death were developmentally regulated; both were maximal in the immediate postnatal period and disappeared over the next 2 weeks. Both types of cell death were reduced by genetic deletion of Bax or by virally mediated overexpression of Bcl-2. Similarly both were reduced by inhibition of caspase activity or by inhibition of Nedd-2 synthesis with antisense oligonucleotides. Finally, both involved activation of c-Jun N-terminal kinase (JNK) signaling. Nedd-2 expression by sympathetic neurons declined in parallel with the developmental loss of LIF-mediated cell death, suggesting that downregulation of the caspase during development may underlie the loss of cytokine-mediated apoptosis. Treatment of sympathetic neurons with an antibody that blocks the function of the low-affinity neurotrophin receptor (p75(LNTR)) prevented LIF-induced cell death. Similarly genetic deletion of p75(LNTR) prevented apoptosis after LIF treatment. These observations suggest that concurrent p75(LNTR) signaling is necessary for LIF-induced cell death and that cytokine-mediated cell death and growth factor deprivation appear to activate the same intracellular pathways involving JNK signaling.

Topical irrigation with polymyxin and bacitracin for spinal surgery

BACKGROUND

The purpose of the present study was to evaluate constant irrigation with saline containing 50,000 units each of polymyxin and bacitracin in a regimen of antimicrobial prophylaxis for clean spinal surgery at two community hospitals with a zero infection rate.

METHODS

The focus was on the bactericidal effects of prophylactic topical antibiotics by assessing random contamination in neurosurgical wounds from: 1) the flora of the integument and nares of the operating team, 2) the surgical apparel, 3) the patient's skin, 4) air-borne organisms in the operating theater, and 5) the surgeon's gloves.

RESULTS

Based on individual biotyping of bacteria and antimicrobial sensitivity testing, no consistent source or pattern could be uncovered for the organisms recovered from the operative site. Relying on longitudinal data, the incidence of intraoperative bacterial growth with continuous saline lavage was reduced from 64 to 4% when the combination of topical polymyxin and bacitracin was added.

CONCLUSIONS

Although the virtual elimination of bacterial growth in the surgical site was accomplished, the efficacy of topical antibiotics in the prevention of wound infection remains unproven.

Apoptosis in neurological disease

Enormous interest in cell death in the past several years has moved apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development, and immunological functioning. It also occurs in pathological conditions, including cancer and acquired immunodeficiency syndrome, and is implicated in neurodegenerative diseases. Claims of neuronal apoptosis induced by various agents and conditions are published regularly, but in many instances the data are questionable because they are incomplete. This review presents a brief history of apoptosis and describes the evidence required before claims of apoptosis are made. Summaries and critiques of important investigations concerning the genetic and biochemical regulation of neuronal apoptosis are presented, as are other studies describing connections between apoptosis and neuronal cell death in physiological and pathological situations. There is a realization that apoptosis can be programmed and is distinguishable from necrotic cell death. Combining apoptosis with programmed cell death produces misleading terminology and confusion over these two forms of cell degeneration. Further investigations into neuronal apoptosis should focus on all of the criteria that the original investigators outlined 25 years ago, to clarify whether apoptosis and/or another form of cell death mediates neuronal degeneration in physiological settings and in neurological diseases such as Alzheimer's disease, Parkinson's disease, epilepsy, and ischemia/stroke.

Apoptosis in the retina

An enormous interest in cell death over the past several years has catapulted apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development and immunologic function. It also occurs in pathological situations including cancer and AIDS, and is implicated in a variety of ocular diseases. This review presents a brief history of apoptosis and the proper evidence needed in order to claim that apoptosis is taking place. A summary and critique of important investigations concerning the genetic and biochemical regulation of apoptosis is presented, as well as a focus on other studies drawing a connection between apoptosis and cell death in physiological and pathological situations.

Leonard I. Malis and prophylactic antibiotics

Leonard I. Malis introduced important changes in the antimicrobial regimen for neurosurgical procedures at The Mount Sinai Hospital. Among Dr. Malis' innovations, intraoperative administration of a single dose each of vancomycin and gentamicin or tobramicin and constant irrigation of the surgical site with a bactericidal antibiotic (streptomycin) led to the elimination of primary wound infections during a 20-year period. In a study to locate potential sources of microbial contamination in his operating room, this combination of parenteral antibiotics was justified, because 36% of patients were at risk for exposure to methicillin-resistant Staphylococcus aureus and Gram-negative bacteria. Streptomycin as a topical agent was found to be highly efficacious in preventing intraoperative growth of potential pathogens cultured from the surgical wound and the operating room environment.

Investigations of the bacteriologic factors in cervical disk surgery

A study was undertaken to evaluate the potential risk of wound infection in cervical disk disease, the appropriateness of the current prophylactic regimen of intravenous cefazolin at Good Samaritan Hospital, and the increasing resistance of coagulase-negative staphylococci in nosocomial infections. In addition, the methodology used in three prior studies was used to verify that double-gloving is a more effective barrier to bacterial contamination than single-gloving and that topical streptomycin lavage is superior to constant irrigation with plain saline. No wound infections were documented in the 40 patients who underwent cervical disk surgery in a 12-month period. Coagulase-negative Staphylococcus species were the most common bacterial isolate, but only 20% were resistant to cefazolin. Of the 11 S. aureus isolates, 9 were sensitive to cefazolin and 2 were methicillin resistant. A remarkable 95% (114/120) of the intraoperative wound cultures were free of bacteria. In only 2 cases was there a serial increase in colonies of the same organism over the course of the operation. There was one positive glove culture--coagulase-negative Staphylococcus sensitive to cefazolin. The patient's skin was identified as the source of contamination in 3 intraoperative cultures of the wound and 2 cultures of the ambient operating room air. Neither individual biotyping of bacteria nor antimicrobial susceptibility testing uncovered any consistent source or pattern to account for the organisms in the surgical wound or ambient operating room air. Bacteria resistant to cefazolin were found in 36% of the intraoperative environmental cultures but in only 16% of the isolates from patients' skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations of the bacteriological factors in clean neurosurgical wounds

A number of questions remained unanswered by the empirical success of antimicrobial prophylaxis for neurosurgical patients at The Mount Sinai Hospital during a 15-year period. Vancomycin (1 g intravenously) and tobramycin (80 mg intramuscularly) were administered in the induction room. Streptomycin (50 mg) was mixed into each liter of saline used to irrigate the surgical incision. A series of 45 consecutive clean neurosurgical operations were investigated. The potential sources of random contamination of the surgical wound that were studied included the following: 1) the patient's skin; 2) the flora of the skin and nares of the operating team; 3) the surgical apparel; 4) the surgeons' gloves; and 5) the airborne organisms in the operating theater. No wound infections were documented during a 4-month period between June and September of 1991. A remarkable 98% of the intraoperative cultures of the surgical wounds were free of bacteria. Positive cultures of glove imprints were found in 29% of the operations, and the bacterial source was traced to four different surgeons in four operations (9%). The surgeons' gloves were also a source of potential pathogens (Staphylococcus aureus) in two instances, but the bacterial species were also recovered from cultures of the environment. Based on individual biotyping of bacteria and antibiotic susceptibility testing, no consistent source or pattern could be uncovered for the bacteria in the surgical wound or the operating room air.(ABSTRACT TRUNCATED AT 250 WORDS)

The risk of wound infection in lumbar disk surgery

A number of questions were left unanswered by the empirical success of a 15-year regimen of prophylactic antibiotics in preventing postoperative sepsis at three community hospitals. Although intraoperative cephalosporins have eliminated the morbidity of primary wound infection, the susceptibility to these agents of nosocomial flora has fallen considerably. The principles of antimicrobial prophylaxis have been established, but the debate over the importance of meticulous aseptic technique versus prophylactic antibiotics goes on. We investigated the microbiologic factors in lumbar disk surgery at Nyack Hospital over one year to study (a) potential sources of random contamination, (b) the flora of the operating room, and (c) the efficacy of various aspects of antiseptic routine.