John Lof

Effects of psyllium therapy on stool characteristics, colon transit and anorectal function in chronic idiopathic constipation.

Background: Psyllium is widely used in the symptomatic therapy of constipation. Its effects on colonic function and their correlation with symptomatic response have not been defined.

Diagnostic Ultrasound Combined With Glycoprotein IIb/IIIa–Targeted Microbubbles Improves Microvascular Recovery After Acute Coronary Thrombotic Occlusions

Background— The high mechanical index (MI) impulses from a diagnostic ultrasound transducer may be a method of recanalizing acutely thrombosed vessels if the impulses are applied only when microbubbles are channeling through the thrombus. Methods and Results— In 45 pigs with acute left anterior descending thrombotic occlusions, a low-MI pulse sequence scheme (contrast pulse sequencing) was used to image the myocardium and guide the delivery of high-MI (1.9 MI) impulses during infusion of either intravenous platelet-targeted microbubbles or nontargeted microbubbles. A third group received no diagnostic ultrasound and microbubbles. All groups received half-dose recombinant prourokinase, heparin, and aspirin. Contrast pulse sequencing examined replenishment of contrast within the central portion of the risk area and guided the application of high-MI impulses. Angiographic recanalization rates, resolution of ST-segment elevation on ECG, and wall thickening were analyzed. Pigs receiving platelet-targeted microbubbles had more rapid replenishment of the central portion of the risk area (80% versus 40% for nontargeted microbubbles; P=0.03) and higher epicardial recanalization rates (53% versus 7% for prourokinase alone; P=0.01). Replenishment of contrast within the risk area (whether with platelet-targeted microbubbles or nontargeted microbubbles) was associated with both higher recanalization rates and even higher rates of ST-segment resolution (82% versus 21% for prourokinase alone; P=0.006). ST-segment resolution occurred in 6 pigs (40%) treated with microbubbles who did not have epicardial recanalization, of which 5 had recovery of wall thickening. Conclusions— Intravenous platelet-targeted microbubbles combined with brief high-MI diagnostic ultrasound impulses guided by contrast pulse sequencing improve both epicardial recanalization rates and microvascular recovery.

Effects of Transcranial Ultrasound and Intravenous Microbubbles on Blood Brain Barrier Permeability in a Large Animal Model

We sought to determine whether transtemporal-applied 1-MHz ultrasound-induced microbubble destruction may be a safe method of transiently altering blood brain barrier (BBB) permeability for drug delivery in a large animal model. Endothelial cells are an integral component of the BBB but also prevent passage of potentially therapeutic drugs. Ultrasound-mediated destruction (UMD) of microbubbles has been shown to disrupt this barrier in small animals when ultrasound is delivered through bone windows. However, the effects of temporal bone attenuation and scattering in a large animal may limit the clinical application of such a technique. Twenty-four pigs were studied. One-MHz pulsed-wave ultrasound at 2.0 W/cm(2) (20% duty cycle) across the temporal bone was applied for 30 min after intravenous injections of either albumin-coated perfluorocarbon microbubble (PESDA, 8 pigs), lipid-encapsulated perfluorocarbon microbubbles (LEMB, 8 pigs) or ultrasound alone (8 pigs). BBB leak was quantified at 30 and 120 min after insonation using Evans blue. Serial magnetic resonance imaging (MRI) was performed in nine of the pigs (3 for each group) to quantify Gadolinium leak within the parenchyma. Peak negative pressures decreased ten-fold when ultrasound was transmitted across the pig temporal bone. Despite this, spectrophotometric analysis showed that both IV LEMB and PESDA combined with transtemporal ultrasound resulted in a significant increase in Evans blue extravasation across BBB of the treated side at 30 min after insonation (p < 0.001; compared with ultrasound alone) but not at 120 min. There was significant retention of Gadolinium within the insonified parenchyma at 60 and 90 min after insonation, but not at 120 min. Oxygen saturation and arterial pressures were not changed after any microbubble injection. Intravenous microbubbles, combined with transtemporal ultrasound, can transiently increase BBB permeability in a large animal. This induced opening of BBB is reversible and may be a safe noninvasive method of achieving drug or gene delivery across the BBB.

Effectiveness Of Transcranial And Transthoracic Ultrasound And Microbubbles In Dissolving Intravascular Thrombi

To examine the effectiveness of 1 ‐MHz and 40‐kHz ultrasound with and without microbubbles in fragmenting thrombi in attenuated conditions.

Long-term effects of jejunoileal autotransplantation on myoelectrical activity in canine small intestine

We studied the longitudinal effects of autotransplantation on the motor function of the jejunoileum. By performing the autotransplantation procedure in a manner similar to that employed for allotransplantation, we sought to examine the long-term effects of both extrinsic denervation and the operative procedure itself on small intestinal motor function. Although initially disrupted, interdigestive myoelectrical activity demonstrated progressive organization: 88% of migrating myoelectrical complexes in animals studied between 12 and 20 months following autotransplantation demonstrated each phase of the complex in normal sequence. Longitudinal studies of several parameters of myoelectrical activity provided further evidence of progressive organization and entrainment of motor functions within the denervated intestine. Several abnormal myoelectrical patterns were observed within the autotransplanted segment, however, and coordination of either slow wave or phase III activity with the proximal innervated intestine did not recover with time. The major component of the myoelectrical response to feeding was permanently impaired with a delayed onset and shortened duration of the fed response. We conclude that the extrinsically denervated intestine recovers the ability to generate and organize all phases of the MMC but demonstrates permanent impairment of the major motor response to food. However, anoxic and cooling damage to enteric nerves and muscle, incurred during the autotransplantation procedure, may explain the persistence of abnormal motor patterns and impaired myoelectrical conduction and could play an important role, additional to that of extrinsic denervation, in the long-term motor function of the allotransplanted intestine.

Treatment of Acute Intravascular Thrombi With Diagnostic Ultrasound and Intravenous Microbubbles

The purpose of this study was to determine whether high mechanical index (MI) impulses from diagnostic ultrasound (DUS) could dissolve intravascular thrombi using intravenous microbubbles. Using a canine model, DUS was applied during a continuous intravenous infusion of microbubbles. Completely thrombosed grafts were assigned to 2 treatment regimens: low-MI (<0.5-MI) ultrasound alone; or intermittent high-MI impulses (1.9-MI) guided by low-MI ultrasound (contrast pulse sequencing). A 20-MHz cavitation detector was placed confocal to the ultrasound transducer to make intravascular cavitation measurements in 1 dog. Intravascular cavitational activity was detected when an MI of >0.5 was applied. In grafts treated with intermittent high-MI ultrasound, angiographic success was 71% at 30 min and 79% at 45 min, compared with 20% and 30% at these times in the low-MI ultrasound alone group (p < 0.05). We conclude that a commercially available DUS transducer can successfully recanalize acute intravascular thrombi during a continuous microbubble infusion.

Can symptoms predict esophageal motor function or acid exposure in gastroesophageal reflux disease? A comparison of esophageal manometric and twenty-four-hour pH parameters in typical and extraesophageal gastroesophageal reflux disease.

It has been suggested that patterns of esophageal motor function and acid exposure may differ between those patients with gastroesophageal reflux disease (GERD) with classic symptoms and those with extraesophageal manifestations. Our objective was to compare various parameters of esophageal motility and acid exposure between groups of patients who had presented with extraesophageal manifestations of GERD alone, a combination of classic and extraesophageal manifestations, or classic GERD symptoms alone. A retrospective review of consecutive patients undergoing esophageal manometry and 24-hour dual-channel esophageal pH testing was performed. Information on patient demographics, symptoms, and results of various manometric and pH testing parameters was examined. We evaluated 84 patients: 32 with extraesophageal symptoms alone, 24 with both classic and extraesophageal symptoms, and 28 with classic symptoms alone. Apart from a trend toward less supine acid exposure in those with extraesophageal symptoms alone, no significant differences were evident among the three patient groups in any of the other parameters of proximal or distal esophageal acid reflux. With respect to motility parameters, lower esophageal sphincter pressure was lower in those with combined symptoms; otherwise, manometric findings were similar in the three patient groups. Our data do not support the hypothesis that the nature of the clinical presentation of GERD, whether in the form of classic or extraesophageal manifestations, is related to differing patterns of esophageal motor function or esophageal acid exposure.

Effects of Attenuation and Thrombus Age on the Success of Ultrasound and Microbubble-Mediated Thrombus Dissolution

The purpose of this study was to examine the effects of applied mechanical index, incident angle, attenuation and thrombus age on the ability of 2-D vs. 3-D diagnostic ultrasound and microbubbles to dissolve thrombi. A total of 180 occlusive porcine arterial thrombi of varying age (3 or 6 h) were examined in a flow system. A tissue-mimicking phantom of varying thickness (5 to 10 cm) was placed over the thrombosed vessel and the 2-D or 3-D diagnostic transducer aligned with the thrombosed vessel using a positioning system. Diluted lipid-encapsulated microbubbles were infused during ultrasound application. Percent thrombus dissolution (%TD) was calculated by comparison of clot mass before and after treatment. Both 2-D and 3-D-guided ultrasound increased %TD compared with microbubbles alone, but %TD achieved with 6-h-old thrombi was significantly less than 3-h-old thrombi. Thrombus dissolution was achieved at 10 cm tissue-mimicking depths, even without inertial cavitation. In conclusion, diagnostic 2-D or 3-D ultrasound can dissolve thrombi with intravenous nontargeted microbubbles, even at tissue attenuation distances of up to 10 cm. This treatment modality is less effective, however, for older aged thrombi.

Treatment of deeply located acute intravascular thrombi with therapeutic ultrasound guided by diagnostic ultrasound and intravenous microbubbles

Objective. We sought to determine the added value of simultaneous imaging of intravenously infused microbubbles that are being used to dissolve an intravascular thrombus with therapeutic ultrasound (TUS). Methods. In a chronic canine arteriovenous graft occluded by a thrombus, TUS (1 MHz) was applied through a 6‐cm‐thick tissue‐mimicking phantom (measured mean ± SD peak negative pressure through the phantom, 958 ± 104 kPa) during an intravenous infusion of either saline (n = 6 occlusions) or lipid‐encapsulated microbubbles (ImaRx Therapeutics, Inc, Tucson, AZ). Therapeutic ultrasound was intermittently applied during the microbubble infusion either at set time intervals (n = 6 occlusions) or when simultaneous diagnostic ultrasound (DUS) indicated a sustained presence of microbubbles (n = 12 occlusions). Success was defined as return of rapid flow within the graft (grade 3 flow). Results. Diagnostic ultrasound showed microbubbles moving through small channels within the thrombus before angiographic evidence of flow in the graft. This guided the timing of TUS application better than using set time intervals. Angiographic clearance of the thrombus and restoration of grade 3 flow at 45 minutes of treatment were seen in 33% of deeply located thrombosed grafts treated with TUS at set time intervals and 92% of grafts treated with TUS guided by DUS (P < .001 compared with set time intervals). Conclusions. The use of TUS with intravenous microbubbles has a high success rate in recanalizing deeply located thrombosed arteriovenous grafts when performed with DUS guidance.

Improved sonothrombolysis from a modified diagnostic transducer delivering impulses containing a longer pulse duration.

Although guided high-mechanical-index (MI) impulses from a diagnostic ultrasound transducer have been used in preclinical studies to dissolve coronary arterial and microvascular thrombi in the presence of intravenously infused microbubbles, it is possible that pulse durations (PDs) longer than that used for diagnostic imaging may further improve the effectiveness of this approach. By use of an established in vitro model flow system, a total of 90 occlusive porcine arterial thrombi (thrombus age: 3-4 h) within a vascular mimicking system were randomized to 10-min treatments with two different PDs (5 and 20 μs) using a Philips S5-1 transducer (1.6-MHz center frequency) at a range of MIs (from 0.2 to 1.4). All impulses were delivered in an intermittent fashion to permit microbubble replenishment within the thrombosed vessel. Diluted lipid-encapsulated microbubbles (0.5% Definity) were infused during the entire treatment period. A tissue-mimicking phantom 5 cm thick was placed between the transducer and thrombosed vessel to mimic transthoracic attenuation. Two 20-MHz passive cavitation detection systems were placed confocal to the insonified vessel to assess for inertial cavitational activity. Percentage thrombus dissolution was calculated by weighing the thrombi before and after each treatment. Percentage thrombus dissolution was significantly higher with a 20-μs PD already at the 0.2 and 0.4 MI therapeutic impulses (54 ± 12% vs. 33 ± 17% and 54 ± 22% vs. 34 ± 17%, p < 0.05 compared with the 5-μs PD group, respectively), and where passive cavitation detection systems detected only low intensities of inertial cavitation. At higher MI settings and 20-μs PDs, percentage thrombus dissolution decreased most likely from high-intensity cavitation shielding of the thrombus. Slightly prolonging the PD on a diagnostic transducer improves the degree of sonothrombolysis that can be achieved without fibrinolytic agents at a lower mechanical index.