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Biomedical subjects

M Misra

Publications and source records attributed to M Misra.

At least 55 records · Page 3Linked to original sources
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

Selection of cerebral aneurysms for treatment using Guglielmi detachable coils: the preliminary University of Illinois at Chicago experience.

OBJECTIVE: We present our initial experience with Guglielmi detachable coils (GDCs). The aim of this study was to determine the criteria for aneurysms, ruptured or unruptured, that are suitable for this technique. The importance of aneurysm geometry and its impact on the final results are discussed. METHODS: A retrospective analysis of 329 patients with 339 cerebral aneurysms that were treated at the University of Illinois Hospital at Chicago from May 1994 to June 1997 was conducted. One hundred eighty-five patients were treated surgically, and 144 were selected for treatment using GDCs. Of the 144 patients selected for GDC treatment, 55 patients with 55 aneurysms were admitted during the acute phase of subarachnoid hemorrhage and 89 patients with 97 aneurysms had nonruptured aneurysms or were treated after clinical recovery of previously ruptured aneurysms. All procedures were performed with the patients under general anesthesia and with systemic heparinization using live simultaneous biplane roadmapping, with the exception of the first four patients. These patients were treated before the installation of the biplane system. The percentage of aneurysm occlusion was determined at the end of each procedure. Follow-up angiography was scheduled to be performed at 6 months, 1 year, and 2 years after treatment. PATIENT SELECTION: For the initial 25 patients (Group 1), selection for coiling was restricted to nonsurgical candidates or patients in whom coiling was thought to be the best treatment choice, based on medical condition and location of the aneurysm. The geometry of the aneurysm was not considered to be an important factor in the selection for coiling. The remaining patients (Group 2) were selected for coiling based on aneurysm geometry, as determined by pretherapeutic angiography. Aneurysms that were considered to be favorable for coiling included those that had a dome-to-neck ratio of at least 2 and an absolute neck diameter less than 5 mm. RESULTS: The initial 25 patients (Group 1) were treated from May 1994 to February 1995. There were high morbidity and mortality rates, with 56% of the treated aneurysms occluded at 6 months. The remaining patients (Group 2) consisted of 119 patients with 123 aneurysms. There was no mortality directly related to the coiling procedure, and permanent morbidity was limited to 1.0%. Three patients (2.5%) developed transient neurological deficits secondary to the procedure, and seven patients (5.8%) experienced periprocedural complications that did not result in neurological sequelae. The morphological results were strongly correlated to the geometry of the aneurysms, with a complete occlusion rate of 72% among the acutely ruptured aneurysms and 80% among the nonacute aneurysms, when patients were selected for treatment based on the geometry of the aneurysms and the dome-to-neck ratio was at least 2. The occlusion rate dropped to 53% when selection was not based on aneurysm geometry and the dome-to-neck ratio was less than 2. A summary of the morphological outcomes for the Group 2 patients shows that 86% of the aneurysms that initially underwent coiling using GDCs were completely occluded (78% by coils alone, 3.0% in conjunction with surgery, and 5.0% with parent artery occlusion). Residual small neck remnants were present in 11% of the Group 2 aneurysms (3.0% were scheduled for surgical treatment of residual neck remnant growths not amenable to further endovascular treatment, and 8% were scheduled for initial 6-mo follow-up examinations). Death resulting from unrelated causes before initial follow-up occurred in 3.0% of the patients. CONCLUSION: These preliminary results suggest that using GDCs is a safe technique resulting in low morbidity and mortality rates for the treatment of intracranial aneurysms in appropriately selected patients. The percentage of complete aneurysm occlusion is related to the density of coil packing, which is strongly dependent on the geometry of the aneurysm. Optim

Acute Disease↗
PubMed1998

Aneurysm geometry: an important criterion in selecting patients for Guglielmi detachable coiling.

The study was aimed determine the criteria for treating cerebral aneurysms, ruptured and unruptured, suitable for endovascular Guglielmi detachable coiling (GDC) with least morbidity and mortality. We will discuss the importance of knowledge of the geometry of cerebral aneurysm and its impact on the results of coiling. We have treated 324 patients with cerebral aneurysms at the University of Illinois Hospital from May 1, 1994 to June 1997. During this period 139 patients were treated with GDC and 185 patients were treated surgically. Of 139 patients treated with coils 54 patients with 54 aneurysms were ruptured and the remaining 85 patients with 90 aneurysms were unruptured. For initial 25 patients, the selection of aneurysms for coiling was random and the geometry of the aneurysm was not considered as an important factor in the selection for coiling, however, in the later series of 114 patients with 119 aneurysms were selected for coiling only when the geometry looked favorable in the angiogram. With time we realized that the dome/neck ratio more than or equal to 2/1 and the diameter of the neck not exceeding 5 mm were most suitable for coiling. The initial series of 25 patients (May 1994 to February 1995) treated without taking geometry of the aneurysms as an important criteria for coiling led to high morbidity and mortality and less than 50% of these aneurysms were angiographically occluded at 6-month follow-up. In the second series of 114 patients (March 1995 to June 1997) with 119 aneurysms we had 0% mortality related to the coiling and only 1.8% permanent morbidity. We found complete aneurysm occlusion in 78% of the subarachnoid hemorrhage and 76% of unruptured group when the dome/neck ratio was more than or equal to 2/1. However, the occlusion rate dropped to 50% when the dome/neck ratio was less than 2/1. This preliminary experience suggests that GDC is a safe technique with low mortality-morbidity for the treatment of intracranial aneurysms in appropriately selected patients. The percentage of complete occlusion of the aneurysm following tight and dense packing is strongly dependent on the geometry of the aneurysm and we conclude that the best results are achieved when the dome/neck ratio is more than or equal to 2/1.

Adult↗
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

Peritoneal dialysis in patients with abdominal vascular prostheses.

Patients with intra-abdominal vascular catastrophes may develop acute and/or chronic renal failure requiring dialysis. To patients with in-situ vascular prostheses the use of peritoneal dialysis (PD) may offer considerable advantages including better hemodynamic control and avoidance of anti-coagulation in a critically ill patient. Institution of PD in such patients, however, often gives rise to concerns relating to peritonitis and subsequent infection of the prosthesis, fluid leaks, and abdominal wound dehiscence. A review of available literature suggests that PD has been utilized in both acute and chronic renal failure following intra-abdominal vascular procedures. PD appears to be an efficient mode of dialysis with a surprisingly small number of complications in these patients.

Abdomen↗
PubMed1998

The rationale for, and role of, heparin in peritoneal dialysis.

The administration of intraperitoneal (i.p.) heparin enjoys time-honored use and is felt to be side-effect free. It is administered whenever fibrin is detected in the dialysate effluent. It is believed that there is no absorption of heparin across the peritoneal cavity. The aim of this article was to review the rationale behind the administration of i.p. heparin, to show that absorption and side effects may occur, and to present recent evidence that questions the routine use of this drug as an additive to dialysate fluid.

Anticoagulants↗
PubMed1998

Mechanism for elevated plasma lipoprotein(a) concentrations in patients on dialysis: turnover studies.

Plasma concentrations of lipoprotein (a) [Lp(a)] are increased in patients on renal replacement therapy. Lipoprotein (a) is increasingly being recognized as an independent cardiovascular risk factor. In an effort to explore the mechanism for elevation of Lp(a) in patients on dialysis we have performed turnover studies of Lp(a) with radioactive iodine. Lp(a) was isolated from 1 patient on hemodialysis (HD) and 1 patient on continuous ambulatory peritoneal dialysis (CAPD); the protein was labeled with 125I and returned to each patient. Lipoprotein (a) was subsequently isolated from the patients over a 15-day period and the decay of the specific radioactivity of Lp(a) was used to determine the fractional catabolic rate (FCR), which was 0.27 (pool/day) for the HD patient and 0.28 (pool/day) for the CAPD patient. These rates are indistinguishable from those measured in 4 patients with hypercholesterolemia (0.29, SEM = 0.01) and in 4 other familial hypercholesterolemic patients (0.29, SEM = 0.02) studied previously using the same method by Knight et al. (7). We found no difference in the FCR of patients on dialysis when compared to patients with hyperlipidemia and normal renal function. Increased plasma concentration of Lp(a) in our patients on renal replacement therapy is not due to decreased catabolism, but is caused by increased synthesis.

Adult↗
PubMed1998

Usefulness of echocardiography in detection of subclinical carditis in acute rheumatic polyarthritis and rheumatic chorea.

Detailed echocardiographic analysis was performed in 10 children with first episode of acute rheumatic fever who presented with acute rheumatic polyarthritis or rheumatic chorea and had no clinically detectable evidence of active carditis. Significant changes were observed in the form of mitral valve prolapse with regurgitation in 3, aortic valve prolapse with regurgitation in 1 and mitral valve billowing without regurgitation in 1 patient each. A significant (p < 0.001) anterior mitral chordal elongation was observed in both the groups--rheumatic polyarthritis and chorea when compared with age and sex matched control subjects. Mitral annular diameter was found to be increased (p < 0.001) in patients presenting with polyarthritis alone. These observations of clinically silent but echocardiographically detectable element of carditis forms the basis of how patients of acute rheumatic fever develop permanent valvular deformities in their latter lives without revealing any cardiac affection earlier.

Adolescent↗
PubMed1998

Cerebral oximetry--techniques.

The use of techniques to measure cerebral oxygen saturation is gradually gaining wide popularity. The main methods available today can mainly be classified as invasive or noninvasive. The invasive technology uses the parenchyma probes, which measure oxygen and biochemical parameters, depending upon the type of probe used. The noninvasive techniques use near infrared spectroscopy for transcranial cerebral oximetry. At present there is no universally accepted indication for the use of either technique but with time and wider use they are expected to become better understood. We discuss our experience and the techniques used in cerebral oximetry.

Brain↗
PubMed1997

Inhibition of nitric oxide synthase enhances peripheral nerve regeneration in mice.

We tested the hypothesis that inhibition of nitric oxide synthase (NOS) following transection of the sciatic nerve in the mouse would adversely influence regeneration of myelinated fibers from the proximal stump. NOS was inhibited by N(omega)-nitro-L-arginine-methyl ester (L-NAME; 10 mg/kg i.p.), a broad spectrum NOS inhibitor given twice daily for the first 10 days following nerve transection in Swiss mice. Controls received the inactive enantiomer N(omega)-nitro-D-arginine methyl ester (D-NAME). Regeneration was assessed by serial recordings of the M potential from interosseous muscles of the foot innervated by sciatic-tibial motor fibers and morphometric analysis of myelinated fibers distal to the injury site. Contrary to expectation, M potentials reappeared earlier in the mice treated with L-NAME and were higher in amplitude (reflecting the number of reinnervating motor fibers) at 10 weeks after the injury. In the L-NAME treated mice, the mean axonal diameter of regenerating tibial myelinated fibers was larger and the fiber size histogram was shifted to larger fibers. Inhibition of NOS in a transected peripheral nerve is associated with enhanced regeneration of myelinated fibers. Local elaboration of NO may be toxic to regenerating axons.

Animals↗
PubMed1997

MRI artifacts following anterior cervical diskectomy.

BACKGROUND: Magnetic resonance imaging (MRI), despite being an excellent imaging technique in neurosurgical practice, is unfortunately susceptible to numerous artifacts. Some of these artifacts are easily identifiable and do not interfere; however, others are more subtle and can be easily mistaken for false pathology. Postoperative MRI can further complicate the imaging interpretation, by producing another group of artifacts. It is imperative for practicing neurosurgeons, as well as neuroradiologists, to have a clear understanding of these postoperative artifacts. METHODS: We discuss four cases who had been operated for anterior cervical decompression with bony fusion. All the patients had a postoperative MRI of the cervical region that showed a "false compression" of the cervical cord. The normal computed tomography (CT) scan in some cases and the discrepancy with the clinical condition of the patients excluded the diagnosis of compression of the cervical cord. RESULTS: The overall appearance of the postoperative MRI can be very difficult to interpret. The artifact seen following anterior cervical diskectomy is an example of such a situation. We have confirmed that the postoperative MRIs showing artifacts do not indicate cord or root compression; a routine postoperative plain X ray or CT scan of the operated area can also confirm the absence of compression. CONCLUSION: These are examples of cases in which the postoperative MRI had an unexpected metallic artifact that not only caused difficulty in the interpretation of the images but at times suggested a clinical problem when actually there was none. Very thin cut CT scans may not show these artifacts that are picked up by the sensitive MRI study. A proper clinical evaluation and selection of the appropriate MRI techniques and the MRIs can eliminate or at least decrease the incidence of the artifacts. Above all, further education of practicing physicians is needed to avoid false alarms caused by these metallic artifacts.

Adult↗
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↗
PubMed1997

Magnetic characteristics of Yaşargil aneurysm clips.

BACKGROUND: Metallic bioimplants are subject to great scrutiny in order to ensure that they are totally harmless to patients. Aneurysm clips are no exception to this rule. Considering the number of aneurysm clips used and their potential for injury, they should be evaluated very meticulously. Determining the magnetic characteristics of these clips is an important part of the evaluation process. In this study, a new method for evaluating magnetism is described and the importance of that information is briefly discussed. METHODS: Twenty Yaşargil aneurysm clips were analyzed using a vibrating sample magnetometer under 1.5 Tesla. This device is highly sensitive, and is capable of measuring the magnetism of small objects. RESULTS: Our measurements showed magnetism of the aneurysm clips ranged from 0.0334-0.1369 electromagnetic units (emu). CONCLUSIONS: Magnetometer measurements and real life tests under magnetic resonance imaging (MRI) have shown that these clips have a very low magnetism and are safe to use in 1.5 Tesla MRI scanners. This study also proves that the vibrating sample magnetometer is a useful device for analyzing the magnetism of aneurysm clips, and their emu values can be used as another industry standard in the production line to increase the safety of these clips.

Aneurysm↗