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Biomedical subjects

F T Charbel

Publications and source records attributed to F T Charbel.

At least 37 records · Page 2Linked to original sources
PubMed1999

Distal internal carotid artery pseudoaneurysms: technique and pitfalls of surgical management: two technical case reports.

OBJECTIVE AND IMPORTANCE: Small, irregular aneurysms of the internal carotid artery (ICA) that are not related to arterial divisions are rare and have characteristics similar to pseudoaneurysms: they do not appear to have well-formed sacs, they are surrounded by clot, and they avulse readily. We report two patients whose treatment demonstrates the surgical technique and important points concerning the management of distal ICA pseudoaneurysms. CLINICAL PRESENTATION: Both patients presented with diffuse subarachnoid hemorrhage. The initial angiographic results were unremarkable in each case. A week after presentation, however, a growing outpouching in the distal ICA was seen. INTERVENTION: At surgery, the aneurysms were found to be on the medial wall of the ICA and were not related to arterial divisions. Quantitative blood flow measurements of the efferent vessels at risk (ICA, M1 and A1 segments) were obtained using a perivascular microflowprobe before and after clipping. In each patient, the aneurysm avulsed entirely during clip application, despite careful placement of the clip parallel to the parent vessel. An encircling clip was then used. Pathological sectioning of the aneurysms revealed loose connective tissue and/or clot with no defined aneurysmal sac. CONCLUSION: Aneurysms of the distal ICA that are not related to arterial divisions are difficult to visualize on angiograms immediately after subarachnoid hemorrhage. They are frail, avulse easily, and may be pseudoaneurysms, necessitating the use of encircling clips. The base of the aneurysm or clot must be trimmed to prevent it from buckling inside the clip sleeve and compromising the ICA lumen. Measuring distal blood flow quantitatively provides valuable information about the patency of the ICA inside the metallic sleeve, since this segment cannot be demonstrated with angiography.

Aneurysm, False↗
PubMed1999

AIM: attentionally based interaction model for the interpretation of vascular angiography.

We propose a model to interpret neurovascular X-ray angiogram (XRA) images interactively. This attentionally based interactive model (AIM) exploits human interaction as part of the solution. AIM posits two channels of interaction: context ("what to look for") and focus-of-attention ("where to look") as the locus of spatial information exchange between the user and the machine. In an AIM system, the user specifies a context (e.g., a carotid vessel) and directs the attentional spotlight to focus machine processing. AIM involves the user with the computer as integral partners and facilitates varying degrees of human intervention in the process. A hierarchy of context abstractions permits the system to function more autonomously (doing high-level tasks like extracting an arterial vessel) in routine interpretation and to require more user intervention (e.g., locating arterial wall boundaries) as the image complexity increases. This is especially important in medical imaging where the medical professional must have ultimate control and confidence in the system. Such technology can have a significant impact on the design of radiological systems.

Angiography↗
PubMed1999

Quantitative assessment of vessel flow integrity for aneurysm surgery. Technical note.

Quantitative measurement of blood flow in cerebral vessels during aneurysm surgery can help prevent ischemic injury and improve patient outcome. The authors report a case of a superior cerebellar artery (SCA) aneurysm in which perivascular microflow probes were used to measure blood flow quantitatively in both the SCA and the posterior cerebral artery before and after aneurysm clipping. Following aneurysm clipping, blood flow in the SCA was reduced to less than 25% of its initial baseline value. Prompt detection of compromised blood flow gave the surgeon the opportunity to adjust the clip and restore SCA flow to its preclipping value within 5 minutes of initial clip placement. Quantitative vessel-flow measurements were integral to the safe progression of the operation and may have prevented an adverse neurological outcome in this patient. The recommended surgical technique and the principle of operation are described.

Aged↗
PubMed1998

Comparison of brain tissue metabolic changes during ischemia at 35 degrees and 18 degrees C.

BACKGROUND: We evaluated brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2) and pH during ischemia with brain temperature at 35 degrees and 18 degrees C in the same patient. METHODS: Surgery was performed in a 60-year-old woman to clip a large aneurysm in the left internal carotid artery (ICA). A Paratrend 7 probe measuring PO2, PCO2, and pH was inserted into tissue at risk for ischemia during ICA occlusion and brain protection was provided with 9% desflurane. One week later, hypothermic circulatory arrest with brain temperature at 18 degrees C was performed for aneurysm clipping and tissue measurements were obtained during ischemia and rewarming. RESULTS: At 35 degrees C, ICA occlusion for 16 minutes produced tissue hypoxia (PO2 = 0) and acidosis (pH = 6.70). The rate of increase of hydrogen ion (H+) reached 50 nEq.L(-1).min(-1) during ICA occlusion and there was a slow recovery of acidosis at the end of the ischemic period. During hypothermic circulatory arrest, tissue PO2 was sensitive to decreases in blood pressure and decreased rapidly during exsanguination. Although tissue pH decreased to 6.5 with 30 min of no pump flow, the rate of H+ increase during hypothermic arrest was one-third of that seen during ischemia at 35 degrees C. During rewarming from profound hypothermia, two phases of recovery from acidosis were observed, one during CO2 clearance and one after tissue reoxygenation. Recovery of acidosis occurred sooner at 18 degrees C than at 35 degrees C. CONCLUSIONS: These results show that tissue acidosis develops more slowly and recovers more rapidly with hypothermic ischemia. This may be an important mechanism of reduced ischemic injury during hypothermia.

Brain↗
PubMed1998

Stereolithography for posterior fossa cranioplasty.

Posterior fossa cranioplasty has been suggested for improvement of neurological symptoms following craniectomy. However, there is no particular recommendation in the literature about techniques for prosthesis manufacture and implantation. We report our experience using rapid prototyping technology and stereolithography for pre-surgical implant design and production of cranioplasties.

Case Reports↗
PubMed1998

Head registration techniques for image-guided surgery.

Localization of the pathological structures in relation to the surrounding anatomy and understanding of the surgical anatomy are probably the most important keys to successful neurosurgery. Image-guided surgery is an important tool for understanding an individual's anatomy and for precisely locating the lesion. Head registration is the most important step in image-guided surgery, required by every system in use today, although these systems show great differences. In this study, head registration techniques and user algorithms in 83 image-guided surgery cases were analyzed. Several types of fiducials including skin markers, bone fiducials, and the stereotactic frame were used for registration. Clinical applications, ease of use, and computer-calculated accuracy values for each type were compared. The average accuracy was 1.50 mm. X-spot skin markers are the fiducials most commonly used with CT scan. The stereotactic frame was the most accurate method, with an accuracy of 0.69 mm. Disc-shaped fiducials were used when MRI was the imaging modality; they provided an average accuracy of 2.62 mm. Head registration is an important part of image-guided surgery; the procedure used for registration should be based on the requirements of each individual case. Our results indicated that the stereotactic frame is the most accurate method of registration; however, skin markers provide reasonable accuracy with significant ease of use and patient comfort.

Adult↗
PubMed1998

Ultrasonic perivascular flow probe: technique and application in neurosurgery.

Documentation and measurement of intraoperative cerebral blood flow during various neurosurgical procedures is not only valuable but also very informative. There are various methods by which qualitative and quantitative measurement of blood flow have been developed over the years. The use of perivascular ultrasonic flow more recently is fast gaining popularity. We describe the technique, principle and application of ultrasonic perivascular micro-flow probe quantitative measurement of selective vessel flow in neurosurgery.

Blood Flow Velocity↗
PubMed1998

Comparison of the effect of etomidate and desflurane on brain tissue gases and pH during prolonged middle cerebral artery occlusion.

BACKGROUND: The authors compared the effects of etomidate and desflurane on brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in patients who had middle cerebral artery occlusion for > 15 min. METHODS: After a craniotomy, a probe that measures PO2, PCO2, and pH was inserted into cortical tissue at risk for ischemia during middle cerebral artery occlusion. A burst suppression pattern of the electroencephalogram was induced with etomidate (n = 6) or 9% end-tidal desflurane (n = 6) started before middle cerebral artery occlusion. Mean blood pressure was supported with phenylephrine to 90-95 mmHg. RESULTS: During baseline conditions, tissue PO2, PCO2, and pH were similar between the two groups (PO2 = 15 mmHg, PCO2 = 60 mmHg, pH = 7.1). During administration of etomidate before middle cerebral artery occlusion, tissue PO2 decreased in five of six patients without a change in PCO2 or pH. During administration of 9% desflurane, tissue PO2 and pH increased before middle cerebral artery clipping. Middle cerebral artery occlusion for an average of 33 min with etomidate and 37 min with desflurane produced a decrease in pH with etomidate (7.09 to 6.63, P < 0.05) but not with desflurane (7.12 to 7.15). CONCLUSION: These results suggest that tissue hypoxia and acidosis are often observed during etomidate treatment and middle cerebral artery occlusion. Treatment with desflurane significantly increases tissue PO2 alone and attenuates acidotic changes to prolonged middle cerebral artery occlusion.

Adult↗
PubMed1998

Thiopental and desflurane treatment for brain protection.

OBJECTIVE: Thiopental produces cerebral metabolic depression and cerebral vasoconstriction. However, the effect of thiopental on brain tissue oxygen pressure (PO2), carbon dioxide pressure, and pH is not known. In a prospective study, we measured brain tissue gases and pH during thiopental or desflurane treatment that was administered for brain protection during brain artery occlusion. METHODS: After institutional review board approval, 20 patients undergoing craniotomies for cerebrovascular surgery were tested; 10 were randomized to receive thiopental and 10 to receive desflurane. After each craniotomy, a Neurotrend probe (Diametrics Medical, Minneapolis, MN) was inserted to measure tissue PO2, carbon dioxide pressure, and pH in a tissue region at risk to develop ischemia during temporary brain artery occlusion. Thiopental or desflurane was administered to produce burst suppression of electroencephalography, and then temporary artery occlusion was performed during aneurysm or extracerebral-to-intracerebral bypass surgery. RESULTS: Thiopental produced no change in tissue gases or pH, but temporary artery clipping in thiopental-treated patients decreased PO2 30% (P < 0.05). Desflurane increased PO2 70% (P < 0.05), and tissue oxygenation remained elevated during temporary artery occlusion. Tissue pH did not decrease in either group during temporary brain artery occlusion. CONCLUSION: Thiopental has a metabolically neutral effect on brain tissue gases and pH, even though it is known to decrease cerebral oxygen consumption. The metabolic depressant and vasodilator effects of desflurane enhance tissue oxygenation and attenuate tissue PO2 reductions produced by artery occlusion. Both thiopental and desflurane inhibit ischemic lactic acidosis and decreases in pH.

Acid-Base Equilibrium↗
PubMed1998

Increased brain tissue oxygenation during arteriovenous malformation resection.

The purpose of this study was to determine if baseline oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in brain tissue adjacent to an arteriovenous malformation (AVM) is different from measures in control patients. In addition, PO2, PCO2, and pH changes were measured during the course of AVM resection. Two groups were studied. Group 1 (n = 8) were non-ischemic patients scheduled for cerebral aneurysm clipping. Group 2 (n = 13) were patients undergoing neurosurgery for AVM resection. Following craniotomy, the dura was retracted and a PO2, PCO2, pH sensor inserted into non-ischemic brain tissue in Group 1. In Group 2, the sensor was inserted into tissue adjacent to the AVM. Following equilibration, tissue gases and pH were measured during steady state anesthetic conditions in Group 1 and during AVM resection in Group 2. The results show that under baseline conditions before the start of surgery, tissue PO2 was decreased in AVM compared to control patients but PCO2 and pH were not changed. During AVM resection, PO2 increased, PCO2 decreased, and pH increased compared to baseline measures. These parameters did not change in control patients over a similar time period. The results suggest that chronic cerebrovascular adaptation occur in AVM patients with decreased tissue perfusion pressure as an adjustment for decreased oxygen delivery. During AVM resection, this adaptation produces a hyperemic environment with relative tissue hyperoxia, hypocapnia, and alkalosis which is not corrected by the end of surgery.

Arteriovenous Malformations↗
PubMed1998

Management of pericentral arteriovenous malformations.

Pericentral arteriovenous malformations (AVMs) have more often been deemed inoperable lesions because of their complexity, owing to their critical locations and dismal outcome. This study discusses the management of this group of patients with a variety of treatments which includes surgery, nidus embolization, and radiosurgery. Out of 89 patients treated for AVMs in our institute over a period of 30 months (1992 through May 1995), we present a case series of 34 patients who had AVMs located in the pericentral region. All the treated AVMs were Spetzler and Martin grade III (6 patients), grade IV (13 patients), and grade V (15 patients). The neurological outcome remained, normal or improved from baseline in 68% of patients following treatments; of the remaining 32%, 19% remained in the same condition (with continuing preoperative deficits) and 10% showed some deterioration from their pretreatment condition. Thus 87% were unchanged or improved after the treatment regime. There was a 3% mortality (one patient who died as result of initial hemorrhage) in the series. Our multimodality treatment for this group of AVMs confirms the efficacy of the practiced strategies for their management. The results derived from the experience with this selected group of patients with AVMs lead us to recommend treating these patients with multimodality regimen rather than awaiting the natural history of the disease in the best interest of the patients.

Adolescent↗
PubMed1998

Role of a perivascular ultrasonic micro-flow probe in aneurysm surgery.

There are various intraoperative monitoring devices available today for helping the neurosurgeons the progress of the intracranial aneurysm surgery. Till now the intraoperative ultrasonic blood flow probes has been used only in vascular, cardiac, and transplant surgery. In the University of Illinois at Chicago we have been able to use the same technology in various neurovascular surgeries. We describe the use of the ultrasonic perivascular blood flow probes in patients operated for clipping of intracranial aneurysm. The use of this perivascular micro-flow probe and its importance in cerebral aneurysm will be discussed.

Brain↗
PubMed1998

Regional tissue pO2, pCO2, pH and temperature measurement.

We compared the difference in brain tissue oxygen pressure (pO2), carbon dioxide pressure (pCO2), pH and temperature with 2 probes inserted 1 cm apart, in 7 patients. Following a craniotomy for cerebrovascular surgery, two Neurotrend probes which measure pO2, pCO2, pH and temperature were inserted into the brain 1 cm apart. Measures were compared between the probes under baseline anesthetic conditions and during the course of surgery. Under baseline conditions, tissue pO2, pCO2, pH and temperature were not different between the 2 probes. A significant correlation was seen between the probes in pH and temperature. During the course of surgery, variation in tissue gases and pH occurred with changes in ventilation and blood pressure but the difference between the probes remained stable. Ischemic changes in pO2, pCO2 and pH were seen in one of the 2 probes during brain artery occlusion or retractor placement. These results show that tissue pO2, pCO2 and pH are consistent in local brain regions during steady state conditions. The relationship between local measures is disrupted by regional ischemia.

Body Temperature↗
PubMed1998

Nonsyndromal craniosynostosis: longitudinal outcome following cranio-orbital reconstruction in infancy.

This paper presents a prospective longitudinal outcome study on patients with nonsyndromal craniosynostosis who were treated with the contemporary craniofacial surgical techniques of suture release, cranial decompression, and cranial and orbital reconstruction and reshaping in infancy. Diagnosis, surgical treatment, and long-term results and complications are reviewed. Preoperative and long-term postoperative intracranial volumes in these patients were evaluated and compared with age and gender match controls throughout the period of the study. From July 1, 1990, to July 1, 1994, 25 patients with isolated nonsyndromal craniosynostosis underwent surgery of the deformity. Eight patients were excluded from the study based on incomplete postoperative computed tomography (CT) records. Of the 17 patients with long-term computerized records, 11 were boys and 6 were girls. The nonsyndromal craniosynostosis patients in this study include six with bilateral coronal craniosynostosis, six with unilateral coronal craniosynostosis, four with sagittal craniosynostosis, and one with metopic craniosynostosis. The average age at the time of surgery for all patients was 9 months, and the average age at the time of the latest follow-up CT scan for all patients in the study was 3.5 years. There were no perioperative complications in this series of patients including no bleeding, no infection, no wound healing complications, and no mortality. Bony fixation included a combination of wire osteosynthesis and rigid microfixation. All patients had only one surgical procedure for the correction of their deformity. Evaluation of both preoperative and long-term postoperative intracranial volume measurements in this series of patients revealed that these volume measurements were comparable with the gender match control groups at all ages throughout the study. The significance of these findings for this longitudinal outcome study is discussed.

Cephalometry↗
PubMed1997

Brain tissue acid-base changes during ischemia.

It is likely that brain tissue acidosis during ischemia is associated with neuronal injury. The authors measured brain extracellular H+, PCO2 and HCO3- concentrations during an ischemic event produced by temporary occlusion of the middle or anterior cerebral arterial distributions, with a 10-minute recovery period. Patients who were to undergo craniotomy for cerebrovascular surgery were recruited for the study. A probe that measures PCO2, pH, and temperature was inserted into tissue at risk for ischemia during temporary arterial occlusion. As a control for this treatment, PaCO2 was increased 10 mm Hg in five patients over a 10-minute period. Under baseline conditions, there was no difference in arterial blood pressure, blood gas levels, or brain temperature between patients who underwent temporary arterial occlusion or those in whom hypercapnia was induced. In patients in whom hypercapnia was induced, H+, PCO2, and HCO3- concentrations increased and all values returned to baseline levels within 10 minutes. In 10 patients who underwent a median 9-minute arterial occlusion, transient ischemia was seen with an increase in tissue H+ and PCO2 levels of 100% and 60%, respectively, and a 20% decrease in HCO3- levels. After a 10-minute postischemic recovery, only PCO2 had returned to baseline levels. These results are consistent with a rapid equilibration of lactic acidosis across the cell membrane during ischemia which decreases HCO3- concentration. After ischemia, extracellular acidosis may be prolonged because of the extrusion of H+ from the cell by membrane ion exchange.

Journal Article↗
PubMed1997

Cranioplasty: cosmetic or therapeutic?

Cranioplasty is among the oldest surgical procedures. Trauma, infections, tumors and compression caused by brain edema are some of the reasons for the removal of bone. The indications for cranioplasty after resolution of the primary process that led to the bone defect were never well defined, and many were the "cosmetic" indications for cranioplasty. However, there are many theories suggesting that an underlying physiological alteration may occur which may require the correction of the bone defect; many patients improve after surgery. We discuss the physiopathological basis of the "syndrome of the trephined" and try to achieve a better understanding of the present status of cranioplasty and its possible therapeutic role.

Brain Injuries↗
PubMed1997

Cerebral interstitial tissue oxygen tension, pH, HCO3, CO2.

BACKGROUND: There are many techniques for monitoring the injured brain following trauma, subarachnoid hemorrhage, or surgery. It is thought that the major determinants for recovery of injured cerebral tissue are oxygen, glucose delivery, and the clearance of metabolites. These factors, at optimal levels, are probably responsible for the regaining of neuronal functions. These parameters are in turn dependent on the tissue's blood flow and metabolism. METHODS: We have been using a single, compact, polyethylene sensor, the Paratrend 7 for the measurement of cerebral oxygen tension, CO2, pH, and temperature. This sensor is designed for continuous blood gas analysis to aid in monitoring neurosurgical patients, both during surgery and in the intensive care unit. RESULTS: Using the Paratrend 7 sensor, we found the normal range of values to be: PO2 33 +/- 11 mm Hg; PCO2 48 +/- 7 mm Hg; pH 7.19 +/- 0.11. Critical measurements are considered to be tissue PO2 < 10 mm Hg; PCO2 > 60 mm Hg, and pH < 6.8. We have had no complications with this device; the risks are similar to those of placing a parenchymal intracranial pressure monitor. CONCLUSIONS: We believe that assessment of interstitial cerebral oxygen saturation can be of great value both intraoperatively and postoperatively. In our experience, the Paratrend 7 system is an effective method of measuring tissue cerebral oxygen tension, along with carbon dioxide levels, pH, and temperature.

Bicarbonates↗