Neurosurgical Setting Research Articles

Haemodynamic Changes During Craniotomy Monitored By A Bioimpedance Plethysmographic Noninvasive Cardiac Output Monitor

Profound cardiovascular changes may occur at various stages during a craniotomy. These changes require a detailed haemodynamic analysis including cardiac output. In the present study, we used a monitor based on electrical bioimpedance method for noninvasive cardiac output measurement. In 17 ASA I and II patients undergoing elective craniotomies for supratentorial tumours, the following haemodynamic parameters were measured noninvasively: heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR). Haemodynamic changes in response to the following events were studied: (a) induction of anaesthesia with thiopentone, (b) 15 min of air-O(2)-isoflurane anaesthesia, (c) infiltration of the scalp with lidocaine adrenaline mixture, and (d) change of inspired gas mixture to N(2)O-O(2)-isoflurane. HR increased (P < 0.001) and SV decreased (P < 0.001) while CO remained unchanged, one min after administration of thiopentone. After 15 min of isoflurane anaesthesia, HR increased (P < 0.001) and, SBP (P = 0.02), DBP (P = 0.002) and SV (P = 0.003) decreased significantly without change in CO. Three minutes after infiltration of the scalp with lidocaine-adrenaline mixture, there was an increase in SBP (P = 0.001), DBP (P = 0.007), SV (P = 0.007) and CO (P = 0.001) and a decrease in SVR (P < 0.001). Addition of nitrous oxide (60%) to the inspired gas mixture decreased SBP (P = 0.003) and DBP (P = 0.001) with a trend for decrease in CO (P < 0.1). The changes recorded in the present study conform to those that have been documented earlier by using invasive monitoring. Bioimpedance plethysmography is a useful noninvasive technique for monitoring and detailed analysis of the rapidly changing systemic haemodynamics during a craniotomy. The device could be useful for investigating important haemodynamic changes in specific neurosurgical settings.

Reduction of Surgical-site Infections in Neurosurgery – The Advantage of Antiseptics Combined with a Sterile Surface

Surgical-site infections remain a significant contributor to hospital-acquired infections despite continued efforts to reduce their occurrence. Infection at the operative site is associated with high morbidity, mortality and prolonged hospitalisation. Typically, in neurosurgical cases the infection rate varies between 1 and 4%. The rise in antimicrobial resistance makes pre-operative methods to reduce surgical-site infection even more important. This is essential since hospitalised patients tend to have a higher frequency of resistant organisms, and the rise in methicillin-resistantStaphylococcus aureus(MRSA) infections has made antibiotic prophylaxis of this highly virulent organism more difficult. In this article we consider the role of pre-operative antisepsis, which aims to reduce bacterial density in the operative site, and the development of a sterile surface concept as part of an approach to reduce surgical-site infection in a neurosurgical setting. The risk of surgical-site infection is proportional to residual bacteria at the wound site, so a reduction in skin bacterial density will be associated with a concomitant reduction in surgical-site infection. The cumulativein vitroandin vivoevidence related to wound contamination and extensive clinical experience with implanted neurosurgical devices illustrate the utility of using 3M™Ioban™2 as part of an infection prevention regimen within neurosurgery.

Auditory based neuropsychology in neurosurgery

In this article, an account is given on the author’s experience with auditory based neuropsychology in a clinical, neurosurgical setting. The patients that were included in the studies are patients with traumatic or vascular brain lesions, patients undergoing brain surgery to alleviate symptoms of Parkinson’s disease, or patients harbouring an intracranial arachnoid cyst affecting the temporal or the frontal lobe. The aims of these investigations were to collect information about the location of cognitive processes in the human brain, or to disclose dyscognition in patients with an arachnoid cyst. All the patients were tested with the DL technique. In addition, the cyst patients were subjected to a number of non-auditory, standard neuropsychological tests, such as Benton Visual Retention Test, Street Gestalt Test, Stroop Test and Trails Test A and B. The neuropsychological tests revealed that arachnoid cysts in general cause dyscognition that also includes auditory processes, and more importantly, that these cognition deficits normalise after surgical removal of the cyst. These observations constitute strong evidence in favour of surgical decompression.

COMBINED X-RAY AND MAGNETIC RESONANCE IMAGING FACILITY

To assess the feasibility of a hybrid imaging setup combining x-ray and magnetic resonance imaging (MRI) in the setting of both stereotactic and functional neurosurgery. A combined x-ray and MRI scanning facility with a trolley system for a fast patient transfer between both modalities was installed in a neurosurgical setting. A registration algorithm for fusion of MRI scans and x-ray images was derived for augmentation of fluoroscopic x-ray projection images with MRI scan data, such as anatomic structures and planned probe trajectories. Phantom measurements were obtained between both modalities for estimation of registration accuracy. Practical application of our system in stereotactic and functional neurosurgery was tested in brachytherapy, deep brain stimulation, and motor cortex stimulation. Phantom measurements yielded a mean spatial deviation of 0.7 +/- 0.3 mm with a maximum deviation of 1.1 mm for MRI scans versus x-rays. Augmentation of x-ray images with MRI scan data allowed intraoperative verification of the planned trajectory and target in three types of neurosurgical procedures: positioning iodine seeds in brachytherapy in one case with cerebellar metastasis, placement of electrodes for deep brain stimulation in two cases of advanced Parkinson's disease, and placement of an epidural grid for motor cortex stimulation in two cases of intractable pain. Combined x-ray and MRI-guided stereotactic and functional neurosurgery is feasible. Augmentation of x-ray projection images with MRI scan data, such as planned probe trajectories and MRI scan segmented anatomic structures may be beneficial for probe guidance in stereotactic and functional neurosurgery.

Optimizing therapy of seizures in neurosurgery

The use of antiepileptic drugs (AEDs) in the neurosurgical setting has a number of implications, including their possible role in the prevention of seizures after acute cerebral insults or brain tumors and the potential for toxicity and interactions when these agents are administered in association with radiotherapy or chemotherapy. This review discusses these controversial issues and draws the following conclusions. 1) AEDs should be prescribed on a short-term basis to prevent seizures occurring within the first week after a cerebral insult (trauma, neurosurgical procedure) but are ineffective to avoid true post-traumatic epilepsy or first seizures in patients with primary or secondary cerebral neoplasms. 2) The use of phenytoin and, to a lesser extent, phenobarbital and carbamazepine during cranial irradiation is associated with an increased risk for severe, potentially fatal, mucocutaneous reactions. In this context, new AEDs with a very low potential for allergic cutaneous reactions should be preferred. 3) Enzyme-inducing AEDs, such as phenytoin, phenobarbital, and carbamazepine, may increase the clearance and reduce the clinical efficacy of corticosteroids and anticancer agents that are also metabolized by the cytochrome P450 system. The newly developed AEDs that are devoid of hepatic metabolism, such as levetiracetam and gabapentin, are now recommended because of good results in preliminary studies and because they do not show interactions with anticancer agents.

Management of Coagulopathy in the Setting of Acute Neurosurgical Disease and Injury

Blood coagulation and hemostasis issues are important aspects of patient care in acute neurosurgical patients. Coagulopathy often complicates the already difficult management of cerebrovascular and intracranial hemorrhagic disease and injuries, adding to the already high associated morbidity and mortality. Common causes of coagulopathy, as well as its management in acute neurosurgical settings, are outlined in this review. Awareness of how to promptly evaluate and effectively treat coagulopathic processes is instrumental to the success of the neurosurgeon in managing acute intracranial pathologies.

Intradural cranial congenital dermal sinuses: diagnosis and management

The authors report on their experience with a series of 15 cranial dermal sinus tracts associated with intradural extension that underwent surgical excision. Ten were located in the posterior and five in the anterior cranial fossa. As expected, the anterior locations were associated with an obvious nasal pit, whereas the posterior locations presented with a more variegated clinical pattern (dimple, lump, or sinus tract). Most patients were diagnosed in their early infancy, although in a few cases, the diagnosis was obtained only at a later stage. Also in our experience [1], these lesions were usually diagnosed in early childhood and only exceptionally later than 3 years of age. Likewise, anatomical distribution was quite similar with about 2/3 of the lesions located in the posterior and 1/3 in the anterior cranial fossa. Although rare, these lesions deserve special attention, particularly in a pediatric neurosurgical setting, for the potential adverse effects of infection; actually, also in the authors’ experience, the few negative outcomes were related to sinus infection complicated by leptomeningeal involvement. This risk should prompt the neurosurgeon to remove the sinus tract as soon as the diagnosis is defined. In fact, not only a timely operation eliminates the risk of infection, but also offers the obvious advantage of performing intradural surgical dissection within an intact arachnoid space, before inflammatory scarring has been produced. This is not a minor aspect when considering the need for a radical resection to prevent late recurrences. Actually, dense adhesions of the associated intracranial dermoid to the nervous and vascular structures are a major problem when attempting at a radical cyst removal and can represent the single most important reason for leaving behind some fragments of cyst capsule [2]. The reportedly elevated infectious risk is more important at present in relation to spontaneous infection of the sinus tract (that can occur whenever preoperatively), rather than to an intraoperative contamination that, although still possible, is to be considered far less common as a consequence of the more refined surgical technique and of the antibiotic therapy. One can agree that MRI is fundamental in achieving a correct diagnosis, although, most frequently, it simply confirms what clinical examination has already discovered. These congenital abnormalities probably represent the single field of pediatric neurosurgery where clinical examination still plays as an important role as sophisticated neuroradiological investigation.

Local brain hypothermia for neuroprotection in stroke treatment and aneurysm repair

Hypothermia is well known to provide neuroprotection following various brain insults in experimental animals. Two recently completed clinical trials of whole body hypothermia in outof–hospital cardiac arrest patients' demonstrated significantly improved survival rates and neurologic outcomes. These results provide new excitement and encouragement for clinical application of hypothermia in cerebrovascular disease. However, the intensive care challenges and adverse events (e.g. prolonged times to target temperatures, shivering and sedation, pneumonia) during the management of hypothermia, dampen enthusiasm for widespread application especially in elderly stroke patients. In this manuscript, we review recent hypothermia trials for stroke. We describe an alternate approach, i.e. local brain cooling, and discuss this new technique with reference to the extensive literature on the marked efficacy of hypothermia. We describe a new technology, the ChillerPadTM and ChillerStripTM Systems developed by Seacoast Technologies, Inc. (Portsmouth, NH, USA). The latter device has received FDA approval and will be employed in a trial of local hypothermia for cerebral aneurysm repair. We present our experimental findings that profound local hypothermia does not damage cortical neurons. We also report that local hypothermia protects the blood–brain barrier and markedly reduces vasogenic edema development in an experimental intracerebral hemorrhage model. Lastly, we review potential mechanisms through which hypothermia provides blood–brain barrier protection and reduces edema formation. Clearly, hypothermia has a bright future for cerebrovascular disease treatment if brain cooling can be delivered in a manner that does not compromise the patient or the neurosurgical and intensive care settings. Local brain cooling may be just that new treatment approach.

Cerebral blood flow velocity increases when propofol is changed to desflurane, but not when isoflurane is changed to desflurane in children

Children may exhibit delayed emergence following maintenance of anesthesia with propofol or isoflurane. Desflurane is often used towards the end of procedures to facilitate emergence. This study evaluated the effect on middle cerebral artery blood flow velocity (Vmca) in anesthetized children when propofol or isoflurane was substituted with desflurane. Forty-two healthy children aged 1-6 years were enrolled. A standardized anesthetic induction was used. Anesthesia was maintained with remifentanil (0.5 microg.kg(-1) bolus followed by an infusion of 0.2 microg.kg(-1).min(-1)) and a randomly selected sequence of propofol/desflurane/propofol, desflurane/propofol/desflurane, isoflurane/desflurane/isoflurane or desflurane/isoflurane/desflurane. Propofol was administered to maintain a steady-state serum concentration of 3 microg.ml(-1). Desflurane and isoflurane were administered at age-corrected 1 MAC. Hemodynamic stability was maintained. Transcranial Doppler sonography was used to measure Vmca. Hemodynamic variables as well as Vmca were measured 30 min after skin incision and repeated 30 min after each change in anesthetic maintenance agent. The mean age and weight was 2.3 +/- 1.3 years and 13.0 +/- 3.7 kg, respectively. The Vmca (mean) increased by 35% from 37.7 +/- 10.5 cm s(-1) to 57.8 +/- 14.6 cm s(-1) (P < 0.0001) when propofol was changed to desflurane but was unaffected when desflurane replaced isoflurane. When propofol is changed to desflurane, cerebral blood flow velocity increases significantly in normal children. This cerebral vasodilatory effect may have important implications in the neurosurgical setting.

Experience with the “Off Label” Use of Recombinant Factor VIIa in a University Hospital.

Recombinant factor VIIa (rFVIIa), NovoSeven@ (Denmark), is a bypass agent approved in the United States for patients with hemophilia and inhibitors. The off-label use of this medication (non approved use) is becoming common in large institutions. Its main use seems to be for excessive bleeding due to trauma and surgery. Here we report our 2 year experience with the off-label use of this product and describe a protocol that is followed at our teaching hospital. Administration of rFVIIa was based on the described protocol. The medication is controlled by the hospital pharmacy and authorization for its use has to be given by the hematologists in collaboration with the clinical pharmacist. To be eligible for the use of rFVIIa the patient has to have received at least 10 units of red pack cells and fresh frozen plasma. In addition, the patient should have fibrinogen level greater than 100 mg/dl, platelet count greater than 70,000/mm3 and fibrin split products less than 80 mcg/ml. A total of 25 patients where treated off-label for excessive bleeding and 4 patients where given rFVIIa preoperative for prevention of bleeding. The doses ranged from 35 to 120 micrograms/kg of body weight with an average of 2 doses given per patient. The use of Factor VIIa was more common in the neurosurgical (NS) setting (7), followed by cardiovascular (CV) (6), gastrointestinal (GI) surgery (6), trauma (6) and others (4). Overall 62% of the patients had adequate hemostasis after the administration of rFVIIa. Successful hemostasis with rFVIIa by diagnosis was 100% for preoperative prophylaxis and GI, for NS 57%, for trauma 50% and for CV 17%. All the patients in the CV group where admitted with acute dissecting aortic aneurysms. No evidence of thromboembolic events where described. The “off-label” use of rFVIIa continues to be widely used with variable results. Until further randomized or controlled, double blind, clinical trials are done, no definitive recommendations can be given. Although this report includes a small cohort of patients, we will consider revising our protocol for bleeding following cardiovascular surgery and trauma.

The ethics of prophylactic antibiotics for neurosurgical procedures

The prophylactic use of antibiotics has become a routine procedure in many areas of medicine. In neurosurgery, however, there is considerable debate over their use in the prevention of postoperative...

Validation study of a central venous pressure-based protocol for the management of neurosurgical patients with hyponatremia and natriuresis.

We had previously suggested a protocol for the management of neurosurgical patients with hyponatremia and natriuresis that was based on their volume status as determined by actual blood volume measurements. All patients in that study were found to be hypovolemic or normovolemic and responded, within 72 hours, to salt and fluid replacement. In the present study, the validity of that protocol was tested using central venous pressure as the sole measure of volume status of patients with hyponatremia and natriuresis. Twenty-five consecutive patients (26 cases) who fulfilled the inclusion criteria typically used to diagnose the syndrome of inappropriate secretion of antidiuretic hormone were included in the study. Central venous pressure was used to classify patients as hypovolemic (< 5 cm of water), normovolemic (6-10 cm of water), or hypervolemic (> 11 cm of water). Hypovolemic patients were given fluids (50 ml/kg/d) and salt (12 g/d). Normovolemic patients were given normal fluid with 12 g of salt per day. In addition, patients with anemia (hematocrit, < 27%) were administered whole blood. The end point was a serum sodium of more than or equal to 130 mEq/L measured in two consecutive samples 12 hours apart or 72 hours after entry into the study. If the serum sodium was less than 130 mEq/L at the end of 72 hours, the clinical condition of the patient determined further management. Nineteen of 25 patients (26 cases) were hypovolemic, the rest were normovolemic. No patient was hypervolemic. Nineteen of 25 patients (26 cases) attained normal serum sodium values within 72 hours, and an additional 3 responded within the next 36 hours (108 h after entry into the study). One patient who was discharged on request had normalized her serum sodium a week later. Among the three nonresponders, who were severely hypovolemic, as revealed by blood volume measurement, and responded to increased fluid and salt administration. One was normovolemic and responded to increased salt administration. There were no complications related to the therapy. Hyponatremia with natriuresis in the neurosurgical setting responds to salt and fluid replacement guided by the patients' volume status as determined by the central venous pressure. This study also offers further indirect evidence to suggest that the syndrome of hyponatremia with natriuresis is most often caused by "cerebral salt wasting" rather than by the syndrome of inappropriate secretion of antidiuretic hormone.

Effect of intermittent reperfusion and nitric oxide synthase inhibition on infarct volume during reversible focal cerebral ischemia

The authors examined the effects of both intermittent reperfusion and nitric oxide synthase (NOS) inhibition, caused by NG-nitro-L-arginine methyl ester (L-NAME) during episodes of focal cerebral ischemia induced to simulate the neurosurgical setting. Seventy-eight Wistar rats underwent single (60 minutes of ischemia) or repetitive (four 15-minute periods of ischemia separated by 5 minutes of reperfusion) episodes of middle cerebral artery occlusion while under anesthesia (1.0% halothane). Twenty-four hours after the procedure, the animals were given neurological examinations and then sacrificed for histological preparation and examination. The intermittent reperfusion groups tended to have smaller mean cortical infarctions. There was also a trend showing a decrease in infarction size in groups given L-NAME. The combination of intermittent reperfusion and preischemic administration of L-NAME (10 mg/kg) resulted in a 65% reduction in infarction size (p < 0.05) when compared to that caused by 60 minutes of single occlusion without L-NAME. The use of NOS inhibition combined with intermittent reperfusion may be a technique to provide intraoperative cerebral protection during neurovascular procedures that require temporary vascular occlusion.

Use of Think Aloud Method to Study Nursesʼ Reasoning and Decision Making in Clinical Practice Settings

The purpose of this article was to describe the use of TA method to study nurses' reasoning and decision making in a neurosurgical setting. The feasibility and benefit of the method were explored, and examples were provided from data collected on a neurosurgical unit during the immediate post operative care of craniotomy patients. The authors hope that this report will encourage other investigators to consider using this method to examine nurses' reasoning and decision making. They also hope that future investigators will be encouraged to move TA to clinical practice settings, rather than continuing to rely on simulations, which can never fully replicate the realities of clinical practice.

Phenytoin Monitoring in the Intensive Care Unit

Phenytoin has been used extensively in the neurological and neurosurgical settings since its introduction in 1938. Despite the fact that alternative agents exist, including a whole series of newer agents, phenytoin is still considered one of the most effective, relatively nontoxic anticonvulsant therapies currently available. Unfortunately, however, the pharmacokinetics and pharmacodynamics of this drug are complex and often confuse the pharmacist and physician team, resulting in suboptimal or unacceptably high serum concentrations. This was exactly the case in our institution up until 3 years ago, when a major pharmacy-initiated education and dosing service program was implemented. We review the basic phenytoin monitoring guidelines used in our institution, which are substantiated by the current literature and by personal experience.

Right-angle partially compressible hemostatic clip applier

A modification of a hemostatic clip applier is described that can apply clips at right angles to the plane of the handles. This device may be particularly useful in certain neurosurgical settings where use of the conventional clip applier is difficult. This device also prevents overcompression of clips.

Percutaneous nucleus pulposus denaturation in treatment of lumbar disc protrusions--a prospective study of 50 neurosurgical patients.

In a prospective study on 50 patients, the 1064-nm Nd-YAG laser was used to denaturate protruding lumbar discs. The method of Ascher [1] was modified using a saline pressure infusion system. Early results show a very good decompressive effect with 48 out of 50 patients in the categories very good and good. At follow-up (mean 184 days postoperation) 31 out of 46 were in these categories, indicating a longer lasting retrieval of the protruded mass. A marked reduction of clinical nerve compression signs was noted. No severe complications occurred. Due to the irrigation system less low back pain was reported. The method seems promising in the standard neurosurgical setting.

Hypoxemia in the Acute Stage of Hypertensive Intracerebral Hemorrhage, with Special Reference to Increased Extravascular Lung Water

Respiratory responses to acute brain damage have been well documented. Severe hypoxemia of unknown origin has often been seen in the acute stage of intracerebral and subarachnoid hemorrhage. Neurogenic pulmonary edema is a particular concern in the neurosurgical intensive care setting. In this study, the extravascular lung water volume (EVLW), alveolar-arterial oxygen difference (AaDO2), and intrapulmonary shunt (QS/QT) were measured in 17 patients with hypertensive intracerebral hemorrhage in the acute stage. The mean AaDO2, QS/QT, and EVLW values were 19.1 mmHg, 7.7%, and 5.49 ml/kg, respectively. The mean pulmonary arterial, central venous, and pulmonary capillary wedge pressures were all within the normal ranges. Eight patients with an AaDO2 of 20 mmHg or more manifested abnormal increases in QS/QT and EVLW, the mean values of which were 10.3% and 6.52 ml/kg, respectively. Nine patients with an AaDO2 of less than 20 mmHg exhibited normal QS/QT and EVLW, with mean values of 5.4% and 4.57 ml/kg, respectively. There was a significant, direct correlation between AaDO2 and EVLW. AaDO2 and EVLW in 11 measured cases either stayed normal or normalized within 4 weeks. These results suggest that acute congestive heart failure and/or pulmonary hypertension were not the main causes of the increase in AaDO2 and EVLW; the increase in EVLW might be explained by increased permeability of pulmonary vessels. The results of this study suggest that an increase in EVLW is causally related to hypoxemia. Further studies of lung water are necessary if we are to better understand respiratory abnormalities associated with acute-stage hypertensive intracerebral hemorrhage.

Low-dose Dopamine Treatment of Patients in Nonketotic Hyperosmolar Hyperglycemic Coma

In the acute neurosurgical setting, nonketotic hyperosmolar hyperglycemic coma (NHC) is thought to be caused by cerebral dehydration therapy and administration of steroids, glycerol, or mannitol. The mortality of this complication is reportedly very high, and is due to acute renal and/or cardiac failure. The authors evaluated the effect of low-dose dopamine (LDD; 1 to 5 micrograms/kg/min) administration in 10 patients with this syndrome. LDD was given to five patients. In these cases, hypovolemia was treated under central venous pressure monitoring with an iso-osmolar hyponatremic lactate solution given in a volume greater than the urine output. After the hypovolemia was corrected, the fluid was administered in a volume equal to the urine output until the serum osmolarity was normalized. In the five patients not given LDD, a large quantity of hypotonic solution was rapidly administered. In all patients treated with LDD, the urinary sodium increased and the urinary output stabilized. Consequently, the excess urea-nitrogen and serum sodium were quite easily washed out. The total net intake volume for the normalization of serum osmolarity was small and the duration of treatment was much shorter than that of patients not treated with LDD. The LDD regimen was not associated with complications, such as aggravation of cerebral edema, renal failure, or cardiac failure. On the other hand, three of the five patients not given LDD died of acute renal and/or cardiac failure without normalization of laboratory data. It is emphasized that this therapy, which results in beta-effect of catecholamine, sodium diuresis, and increased renal blood flow, is a practical means of managing acute neurosurgical cases complicated by NHC.

Closed circuit television in the neurosurgical setting.

A purpose built closed circuit television network was designed and installed for recording and reviewing neurosurgical procedures. A detailed account is given of the equipment used and the installation of the system.