Hypertonic saline: a clinical review.

Literature suggest that hypertonic saline (HTS) solution with sodium chloride concentration greater than the physiologic 0.9% can be useful in controlling elevated intracranial pressure (ICP) and as a resuscitative agent in multiple settings including traumatic brain injury (TBI). In this review, we discuss HTS mechanisms of action, adverse effects, and current clinical studies. Studies show that HTS administered during the resuscitation of patients with a TBI improves neurological outcome. HTS also has positive effects on elevated ICP from multiple etiologies, and for shock resuscitation. However, a prospective randomized Australian study using an aggressive resuscitation protocol in trauma patients showed no difference in amount of fluids administered during prehospital resuscitation, and no differences in ICP control or neurological outcome. The role of HTS in prehospital resuscitation is yet to be determined. The most important factor in improving outcomes may be prevention of hypotension and preservation of cerebral blood flow. In regards to control of elevated ICP during the inpatient course, HTS appears safe and effective. Although clinicians currently use HTS with some success, significant questions remain as to the dose and manner of HTS infusion. Direct protocol comparisons should be performed to improve and standardize patient care.

Method to perform IV injections on mice using the facial vein.

A novel technique for gaining IV access in a mouse model is presented. Using a cut-down approach, the facial vein is identified through an incision from anterior to the external auditory meatus to posterior to the lateral ispilateral canthus. A small gage needle (30gauge) may be inserted to inject medications. A high success rate (93%) as determined by direct visualization is achieved. The technique would prove especially useful for animals slated for kinematic testing as the incision does not interfere with the animal's ventral surface.

History of carotid surgery.

The history of carotid surgery begins not with the detailing of the various surgical procedures, as might be imagined, but with a history of the understanding of the nature of carotid occlusive disease. It was only through an understanding of the basis of this disease that a rational surgical treatment could be formulated. Following a well-characterized disease process, surgical strategies were developed and refined during the first half of the twentieth century. After these surgical techniques had been refined, a number of national and international trials were performed to better determine which patients were candidates for surgical intervention. Currently, endovascular treatment stands on the horizon as a new therapeutic modality with which carotid occlusive disease may be treated.

Neuroprotective effect of postischemic administration of progesterone in spontaneously hypertensive rats with focal cerebral ischemia.

OBJECT: Exogenous progesterone has been shown to reduce brain edema and ischemia-induced cell damage and to improve physiological and neurological function during the early stage of focal cerebral ischemia. In the present study, the authors assessed the neuroprotective potential of progesterone during the late stage of ischemia in a transient middle cerebral artery (MCA) occlusion model in the rat. METHODS: Forty-eight male spontaneously hypertensive rats were randomly assigned to six groups. Progesterone was dissolved in dimethyl sulfoxide (DMSO). In four groups of rats, the dissolved progesterone (4 mg/kg or 8 mg/kg) was administered for 2 or 7 days after ischemia. In two control groups DMSO was administered for 2 or 7 days after ischemia. Occlusion of the MCA was induced by insertion of an intraluminal suture, and reperfusion was accomplished by withdrawal of the suture. Treatment was initiated on reperfusion, which followed 2 hours of MCA occlusion, and continued once a day. Lesion volume, neurological deficit, and body weight loss were measured 2 or 7 days after ischemia, depending on the animal group. Treatment with a high dose of progesterone (8 mg/kg) resulted in reductions in lesion size, neurological deficits, and body weight, compared with control rats. CONCLUSIONS: Administration of progesterone to male rats 2 hours after MCA occlusion reduces ischemic brain damage and improves neurological deficit even 7 days after ischemia.

Carotid endarterectomy: general principles and surgical technique.

In this article, the authors describe their standard technique for carotid endarterectomy and discuss the various surgical options and different variations of the procedure. Although there are numerous ways to perform carotid endarterectomy, several basic principles of carotid reconstruction must be adhered to. The surgeon must have complete preoperative knowledge of the patient's vascular anatomy, must maintain complete vascular control at all times, must have sufficient working anatomic knowledge to prevent harm to adjacent structures, and must assure the patient a patent repair that is free of technical errors. The most important factor in assuring a technically acceptable carotid surgery is the availability of a skilled cerebrovascular surgeon who has demonstrable morbidity and mortality rates below 3% and a proper understanding of both vascular principles and cerebral physiology.

Mild hypothermia as a protective therapy during intracranial aneurysm surgery: a randomized prospective pilot trial.

OBJECTIVE: To conduct a pilot trial of mild intraoperative hypothermia during cerebral aneurysm surgery. METHODS: One hundred fourteen patients undergoing cerebral aneurysm clipping with (n = 52) (World Federation of Neurological Surgeons score < or =III) and without (n = 62) acute aneurysmal subarachnoid hemorrhage (SAH) were randomized to normothermic (target esophageal temperature at clip application of 36.5 degrees C) and hypothermic (target temperature of 33.5 degrees C) groups. Neurological status was prospectively evaluated before surgery, 24 and 72 hours postoperatively (National Institutes of Health Stroke Scale), and 3 to 6 months after surgery (Glasgow Outcome Scale). Secondary outcomes included postoperative critical care requirements, respiratory and cardiovascular complications, duration of hospitalization, and discharge disposition. RESULTS: Seven hypothermic patients (12%) could not be cooled to within 1 degrees C of target temperature; three of the seven were obese. Patients randomized to the hypothermic group more frequently required intubation and rewarming for the first 2 hours after surgery. Although not achieving statistical significance, patients with SAH randomized to the hypothermic group, when compared with patients in the normothermic group, had the following: 1) a lower frequency of neurological deterioration at 24 and 72 hours after surgery (21 versus 37-41%), 2) a greater frequency of discharge to home (75 versus 57%), and 3) a greater incidence of good long-term outcomes (71 versus 57%). For patients without acute SAH, there were no outcome differences between the temperature groups. There was no suggestion that hypothermia was associated with excess morbidity or mortality. CONCLUSION: Mild hypothermia during cerebral aneurysm surgery is feasible in nonobese patients and is well tolerated. Our results indicate that a multicenter trial enrolling 300 to 900 patients with acute aneurysmal SAH will be required to demonstrate a statistically significant benefit with mild intraoperative hypothermia.

The differences in electroencephalographic changes in patients undergoing carotid endarterectomies while under local versus general anesthesia.

OBJECTIVE: This study compared the electroencephalographic (EEG) changes occurring during carotid occlusion in 225 consecutive patients undergoing carotid endarterectomies performed by two surgeons, one using local and the other using general anesthesia. METHODS: A retrospective review of patients undergoing carotid endarterectomies for carotid occlusive disease was conducted. EEG changes associated with intraoperative ischemia (decreased amplitude, generalized slowing, and loss of fast activity) resulting in the need for an indwelling arterial shunt were recorded for the two anesthesia groups. To determine the similarities or differences between the two groups, the groups were compared regarding age, risk factors, and indications for surgery. RESULTS: Significant EEG changes were noted in 6 of 96 patients (6.3%) in the local anesthesia group versus 19 of 121 patients (15.7%) in the general anesthesia group. EEG changes consisted solely of generalized slowing in the local anesthesia group, whereas a more varied spectrum was observed in the general anesthesia group. The two groups were similar regarding age and risk factors. Although the local anesthesia group had more asymptomatic patients, symptomatic patients did not have a greater incidence of EEG changes. CONCLUSION: There is a large difference in EEG changes potentially requiring shunt placement in patients undergoing surgery while under local (6.3%) versus general (15.7%) anesthesia. This could not be explained based on age, risk factors, interpretation of EEG findings, or indications between the two groups. We conclude that EEG monitoring may be insensitive and may fail to detect ischemia in patients who are under regional anesthesia. Alternately, the presence of general anesthetics may alter the character of the EEG findings and increase the sensitivity of EEG monitoring to ischemic events.

Effects of etomidate administration on cerebral collateral flow.

OBJECTIVE: Augmentation of blood flow to collateral-dependent tissue (CDT) as a result of selective vasodilation of collateral vessels has been shown to occur with various stimuli after middle cerebral artery occlusion. Etomidate, a carboxylated imidazole derivative, is a nonbarbiturate anesthetic that is used clinically both as an anesthetic and as a neuroprotective agent. The effect etomidate has on collateral cerebral vessels is unknown. The purpose of our studies was to test whether etomidate selectively augmented cerebral blood flow (CBF) to CDT during ischemia as an additional mechanism of neuroprotection. METHODS: A left craniotomy was performed in each of 14 dogs, with the animals under halothane anesthesia. A branch of the middle cerebral artery was occluded and cannulated distally for determination of CDT using a "shadow flow" technique. CBF and vascular pressures were measured and used to calculate vascular resistance. An etomidate infusion (0.1 mg/kg of body weight/min administered intravenously) was started, and CBF and vascular pressures were measured at 10 and 40 minutes. Hypotension was then induced, and CBF and pressures were again measured. RESULTS: CBF was significantly reduced in all regions of the brain, including CDT, when etomidate was infused. CDT showed a 53.7% reduction in flow, whereas normal CBF was reduced by at least 63.4%. During hypotension, blood flow to CDT was reduced by an additional 42.7%, whereas normal cerebrum was reduced by at least 22.7%. Vascular resistance was increased in all vessels during etomidate infusion. CONCLUSION: The neuroprotective effects of etomidate do not seem to be through the augmentation of collateral or global CBF.

Posterior ventricular catheter burr-hole localizer. Technical note.

Proper ventricular catheter placements are associated with improved shunt performance. When placing ventricular catheters via the posterior approach, the surgeon must determine an optimum trajectory and then pass a catheter along that trajectory. The incidence of optimal posterior catheter placements is increased by using a posterior catheter guide (PCG); however, errors may still occur because of poor selection of a posterior burr-hole site. In this report an easy-to-use posterior burr-hole localizer (Localizer) is described that defines the optimum burr-hole location based on geometric relationships involving the ear and supraorbital rims. The basic design principle of the Localizer was formulated and tested by using neuronavigational imaging tools to examine normal adult ventricular anatomy in relation to surface landmarks and by reviewing imaging studies obtained in 50 adult patients with hydrocephalus. Subsequently, the Localizer was used in 28 consecutive patients scheduled to undergo shunt surgery performed by using the PCG. In all cases the catheter entered the ventricle on the first pass and postoperative imaging studies demonstrated successful placement in the ipsilateral anterior horn. There were no catheter-related complications. These early results indicate that the Localizer and PCG devices may be safe and effective when used in combination for placement of posterior ventricular catheters.

A combined surgical-endovascular device concept for giant aneurysm neck occlusion.

PURPOSE: In this report, we describe a new multimodality device concept for occluding giant aneurysms. The device is designed to exploit the advantages, and avoid the disadvantages, of conventional microneurosurgery and interventional neuroradiology methods. CONCEPT: Our device concept involves surgically placing small permanent magnets, incorporated into a partially occluded magnetic clip, about the extraluminal neck without mechanically compromising the perforating vessels. These magnets serve as optimally positioned anchor points for ferromagnetic materials subsequently introduced via the endovascular route. RATIONALE: Currently, neurosurgical extraluminal obliteration of giant aneurysms is achieved by mechanically closing the aneurysm neck with metal clip blades, which is a technique that risks inadvertent occlusion of critical perforating vessels. Perforating vessel strokes can largely be avoided using endovascular aneurysm occlusion methods. However, in the setting of the giant aneurysm, these endovascular techniques are associated with high rates of incomplete occlusion. DISCUSSION: Preliminary feasibility tests of this concept were conducted using a simple prototype constructed in our laboratories.

Bilateral (mirror-image) aneurysms at the origin of the posteroinferior cerebellar artery: case report.

OBJECTIVE AND IMPORTANCE: This case demonstrates mirror-image aneurysms at the origin of the posteroinferior cerebellar arteries. To the best of our knowledge, this location has not been previously described. Identification of this entity is important for surgical planning. CLINICAL PRESENTATION: The patient presented with a history of a sentinel headache 1 week before his Grade I subarachnoid hemorrhage occurred. Before operative intervention, the patient developed acute deterioration of his mental status from hydrocephalus. After appropriate treatment for the hydrocephalus, he maintained a stable neurological course throughout evaluation and therapy. INTERVENTION: The patient underwent bilateral clipping of his aneurysms in a prone position without consequence. CONCLUSION: This case demonstrates a highly unusual mirror-image aneurysm of the proximal posteroinferior cerebellar arteries. Although multiple aneurysms are commonplace, to the best of our knowledge, this is the first reported case of bilateral posteroinferior cerebellar artery aneurysms at their origin. Also, the surgical approach is unique and allows bilateral clipping at the same operative setting.

Effect of N-methyl-D-aspartate and inhibition of neuronal nitric oxide on collateral cerebral blood flow after middle cerebral artery occlusion.

OBJECTIVE: To study the role of N-methyl-D-aspartate (NMDA) receptor activation and selective inhibition of neuronal nitric oxide synthase with 7-nitroindazole (7-NI) on blood flow to collateral-dependent tissue (CDT) after middle cerebral artery (MCA) occlusion. METHODS: A left craniotomy was performed in each of 11 dogs with the animals under halothane anesthesia. A branch of the MCA was occluded and cannulated distally for determination of CDT, using a "shadow flow" technique. Cerebral blood flow (CBF) and vascular pressures were measured and used to calculate vascular resistance. TECHNIQUE: Our shadow flow model has the ability to identify an area of CDT, with minimal contamination from overlap flow within a morphologically identified "risk area" for MCA branch occlusion. RESULTS: NMDA increased blood flow to CDT by 56.2%, while normal ipsilateral and contralateral cerebrum increased by at least 35% from baseline. 7-NI caused a significant drop in regional CBF, with the greatest drop of 41.7% occurring in the CDT. Normal ipsilateral and contralateral CBF was reduced by 31.7 and 23.9%, respectively. The dilator response to NMDA was significantly attenuated after 7-NI administration, except in CDT where flow increased ("inverse steal"). Cerebral vascular resistance decreased in response to NMDA and increased with 7-NI. CONCLUSION: Neuronal nitric oxide production seems to play an important role in regulating vascular tone and CBF to CDT after MCA occlusion. Selective preservation of blood flow to CDT seems to be mediated by NMDA receptor activation but independent of neuronal nitric oxide production.

Current indications for carotid endarterectomy.

Four randomized cooperative trials for asymptomatic carotid artery disease and three randomized cooperative trials of symptomatic carotid artery disease have been completed and published. There are now firm and proven indications for carotid artery reconstruction. Asymptomatic carotid artery disease with 60% or greater linear stenosis on angiography has been shown to be better treated with surgery than with medical therapy alone. For symptomatic patients, linear stenoses of 50% of greater have been shown to have a significant benefit with surgical treatment. All surgical recommendations are based on a morbidity/mortality of 3% or less for the individual surgeon.

Carotid endarterectomy: current indications for surgery.

The study of carotid artery occlusive disease interventions can be divided clinically into the treatment of asymptomatic and symptomatic diseases. Clinical trials that have studied or are currently studying asymptomatic disease include: the Carotid Artery Stenosis with Asymptomatic Narrowing Operation Versus Aspirin study; the Mayo Asymptomatic Carotid Endarterectomy trial; Veterans Administration Cooperative Trial on Asymptomatic Carotid Stenosis; and the Asymptomatic Carotid Atherosclerosis Study. Trials for the treatment of symptomatic disease include: the North American Symptomatic Carotid Endarterectomy Trial; the European Carotid Surgery Trial; and the Veterans Administration Cooperative Study. In the earliest trials conducted to study asymptomatic disease medical therapy was slightly favored; on close scrutiny these studies were flawed and the findings appeared to be equivocal. The more scientific and appropriate trial, which was ended due to ethical concerns, revealed a clear advantage in patients who underwent surgery for greater than 60% stenosis and when the surgical center demonstrated less than 3% surgical risks. All trials studying symptomatic disease found a significant decrease in subsequent stroke when surgical intervention was performed. It is now judged that patients with greater than 50% stenosis receive significant benefit. In this paper the authors review the data from all of these studies. They also review data for special circumstances, such as critical stenosis and patients with symptomatic and asymptomatic Hollenhorst plaques. It is their opinion that these data have allowed surgeons to make much more educated decisions when considering the treatment of patients with carotid artery occlusive disease.