Functional MRI and its applications to the clinical neurosciences.

Functional magnetic resonance imaging (fMRI) is an emerging methodology for studying regional brain function in vivo at relatively high spatial and temporal resolution. Because MRI methods are comparatively inexpensive and entirely noninvasive, fMRI has rapidly become one of the most popular approaches for brain mapping in cognitive and systems neuroscience. There has also been great interest in using fMRI to assist in clinical diagnosis and management, with promising demonstrations of feasibility in a number of applications. Both resting and task-specific regional brain activity can be measured, primarily utilizing alterations in regional cerebral blood flow (CBF) as a surrogate marker for neural function. This article reviews the biophysical and physiological bases of fMRI and its applications to the clinical neurosciences, with particular attention to potential challenges of fMRI under pathophysiological conditions. Carefully controlled prospective evaluation of clinical fMRI in its various potential applications will be required for fMRI to be validated as a clinically useful tool. Because the technology for fMRI is widely available, its impact could be substantial.

Postoperative neurologic assessment and management of the cardiac surgical patient.

The neurologic evaluation of patients in the immediate postoperative period and postanesthetic state is unique and challenging. Neurologic assessment is complicated by the lingering residual effects of anesthetics as well as by the effects of narcotic analgesics, anxiolytics, and muscle relaxants, especially in ventilated patients. In this review we examine the suspected causes, clinical manifestations, diagnostic options, and intervention schemes for the common neurologic syndromes seen after cardiac operations.

Intestinal ischemia: treatment by peritoneal lavage with oxygenated perfluorochemical.

Though the delivery of elemental oxygen to tissues ravaged by anaerobic infection may be useful, little data exists that suggests that such therapy may benefit ischemic tissue. We report the development of a model to test the question that peritoneal lavage with an oxygen containing solution may favorably influence occlusive intestinal ischemia. Adult Sprague-Dawley rats with Nembutal (sodium pentobarbital) anesthesia underwent midline laparotomy; a microvascular clamp was applied to the superior mesenteric artery (SMA); and an inflow and outflow lavage catheter was placed. Treatment groups included control rats undergoing SMA occlusion only without lavage, rats lavaged with albumin during SMA occlusion (medium control), and rats lavaged during SMA occlusion with oxygenated perfluorochemical FC-47 emulsified in albumin (O2-FC-47). The increase in serum L-lactate following occlusion was used as an index of intestinal injury whether the perfusate was maintained at room temperature (28 degrees C) or body temperature (37 degrees C). Beginning with time O, which corresponded to the time of unclamping, subsequent samples were collected at 15, 30, and 60 minutes after a 30-minute SMA occlusion. Sequential lactates in 13 control rats were 4.18, 4.10, 3.88, and 4.52 mmol/L. Albumin lavaged animals had values at 28 degrees C of 2.23, 1.35, 1.8, and 2.44 mmol/L and values at 37 degrees C of 2.22, 1.40, 2.07, and 3.21 mmol/L, respectively. With O2-FC-47 lavage the respective lactates were 1.89, 1.09, 1.32, and 1.44 mmol/L at 28 degrees C and 2.14, 2.19, 2.50, and 2.1 mmol/L at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen-sensitive 19F NMR imaging of the vascular system in vivo.

The fluorine nuclear magnetic resonance spin-lattice relaxation rate (1/T1) of the perfluorochemical blood substitute perfluorotripropylamine (FTPA) is very sensitive to oxygen tension. This presents the possibility of measuring blood oxygen tension by 19F MR imaging. We obtained oxygen-sensitive 19F NMR images of the circulatory system of rats infused with emulsified FTPA. Blood oxygenation was assessed under conditions of both air- and 100% O2-breathing. T1 relaxation times were derived from MR images using a partial saturation pulse sequence. The T1 times were compared with a phantom calibration curve to calculate average blood pO2 values in the lung, liver, and spleen. The results showed marked, organ-specific increases in blood oxygen tension when the rat breathed 100% O2 instead of air.

Morbidity and mortality of short-bowel syndrome acquired in infancy: an update.

The advent of total parenteral nutrition (TPN) has made survival beyond infancy possible for large numbers of patients who have sustained massive small intestinal loss due to a variety of intraabdominal catastrophes. However, the quantity and quality of life have been limited by the development of late sequelae due both to the protracted use of TPN and the long-term complications of foreshortening of the gut. To determine to what extent the morbidity and mortality of short-bowel syndrome (SBS) may have improved over the last 10 years, we reviewed our experience since 1973 with patients losing more than 50% of total small intestinal mass in infancy. The etiologies of SBS in the 16 study patients were necrotizing enterocolitis (6), midgut volvulus (5), multiple atresias (3), gastroschisis (1), and congenital SBS (1). Overall survival was 81%; total small intestinal length (SIL) at the time of diagnosis was 44.2 +/- 7.9 cm in survivors and 30.3 +/- 7.8 cm in nonsurvivors, probability values not significant. Although no patient survived without an ileocecal valve whose total SIL was greater than 20 cm, the three deaths in this series were not related directly to the SIL, but to end-stage liver disease resulting from TPN-associated cholestasis. Among the survivors, adaptation to enteral feedings required 13.8 +/- 2.5 mo, during which time weaning from TPN occurred; weight at adaptation was 6.87 +/- 1.32 kg.(ABSTRACT TRUNCATED AT 250 WORDS)