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Biomedical subjects

Sam R Sharar

Publications and source records attributed to Sam R Sharar.

At least 19 recordsLinked to original sources
PubMed2006

Microbubble-enhanced hemorrhage control using high intensity focused ultrasound.

Our objective was to investigate whether hemorrhage control can be achieved faster when high-intensity focused ultrasound (HIFU) is applied in the presence of ultrasound contrast agents (UCA) as compared to HIFU only application. Incisions (3 cm long and 0.5 cm deep) were produced in the livers of anesthetized rabbits. UCA Optison (0.18 ml/kg) was injected into the mesenteric vein. A HIFU applicator (5.5 MHz, 6800 W/cm2 in situ) was scanned at a rate of 1-2 mm/s in one direction over the incision (with multiple passes if needed), until hemostasis was achieved. Hemostasis times were 59+/-23 s (n=21) in the presence of Optison and 70+/-23 s (n=29) without Optison. The presence of Optison produced on average 37% reduction in hemostasis times normalized to initial bleeding rates (p<0.05), as well as 60% faster formation of the coagulum seal over the incision (p<0.05). Gross and histological observations showed similar appearance of HIFU lesions produced in the presence of Optison and HIFU lesions produced without Optison. Our results suggest potential utility of UCA for increasing efficiency of HIFU-induced hemostasis of solid organ injuries.

Albumins↗
PubMed2006

Virtual reality helmet display quality influences the magnitude of virtual reality analgesia.

UNLABELLED: Immersive Virtual Reality (VR) distraction can be used in addition to traditional opioids to reduce procedural pain. The current study explored whether a High-Tech-VR helmet (ie, a 60-degree field-of-view head-mounted display) reduces pain more effectively than a Low-Tech-VR helmet (a 35-degree field-of-view head-mounted display). Using a double-blind between-groups design, 77 healthy volunteers (no patients) aged 18-23 were randomly assigned to 1 of 3 groups. Each subject received a brief baseline thermal pain stimulus, and the same stimulus again minutes later while in SnowWorld using a Low-Tech-VR helmet (Group 1), using a High-Tech-VR helmet (Group 2), or receiving no distraction (Group 3, control group). Each participant provided subjective 0-10 ratings of cognitive, sensory, and affective components of pain, and amount of fun during the pain stimulus. Compared to the Low-Tech-VR helmet group, subjects in the High-Tech-VR helmet group reported 34% more reduction in worst pain (P < .05), 46% more reduction in pain unpleasantness (P = .001), 29% more reduction in "time spent thinking about pain" (P < .05), and 32% more fun during the pain stimulus in VR (P < .05). Only 29% of participants in the Low-Tech helmet group, as opposed to 65% of participants in the High-Tech-VR helmet group, showed a clinically significant reduction in pain intensity during virtual reality. These results highlight the importance of using an appropriately designed VR helmet to achieve effective VR analgesia (see ). PERSPECTIVE: Pain during medical procedures (eg, burn wound care) is often excessive. Adjunctive virtual reality distraction can substantially reduce procedural pain. The results of the present study show that a higher quality VR helmet was more effective at reducing pain than a lower quality VR helmet.

Adolescent↗
PubMed2006

Using FMRI to study the neural correlates of virtual reality analgesia.

Excessive pain during medical procedures, such as burn wound dressing changes, is a widespread medical problem and is especially challenging for children. This article describes the rationale behind virtual reality (VR) pain distraction, a new non-pharmacologic adjunctive analgesia, and gives a brief summary of empirical studies exploring whether VR reduces clinical procedural pain. Results indicate that patients using VR during painful medical procedures report large reductions in subjective pain. A neuroimaging study measuring the neural correlates of VR analgesia is described in detail. This functional magnetic resonance imaging pain study in healthy volunteers shows that the large drops in subjective pain ratings during VR are accompanied by large drops in pain-related brain activity. Together the clinical and laboratory studies provide converging evidence that VR distraction is a promising new non-pharmacologic pain control technique.

Analgesia↗
PubMed2006

Hypnosis delivered through immersive virtual reality for burn pain: A clinical case series.

This study is the first to use virtual-reality technology on a series of clinical patients to make hypnotic analgesia less effortful for patients and to increase the efficiency of hypnosis by eliminating the need for the presence of a trained clinician. This technologically based hypnotic induction was used to deliver hypnotic analgesia to burn-injury patients undergoing painful wound-care procedures. Pre- and postprocedure measures were collected on 13 patients with burn injuries across 3 days. In an uncontrolled series of cases, there was a decrease in reported pain and anxiety, and the need for opioid medication was cut in half. The results support additional research on the utility and efficacy of hypnotic analgesia provided by virtual reality hypnosis.

Adult↗
PubMed2005

Hospital characteristics associated with the management of pediatric splenic injuries.

CONTEXT: Despite evidence that more than 90% of children with traumatic injuries to the spleen can be successfully managed nonoperatively, there is significant variation in the use of splenectomy. As asplenic children are at increased risk of overwhelming postsplenectomy infection, nonoperative management may be considered a quality of care indicator. OBJECTIVE: To test the hypothesis that children are more likely to undergo splenectomy in general hospitals than in children's hospitals. DESIGN: Retrospective cohort study using data from the Kid's Inpatient Database (KID) for the year 2000. Multivariable regression was used to control for patient and hospital characteristics. SETTING AND PARTICIPANTS: All children aged 0 to 16 years who were hospitalized with a traumatic (noniatrogenic) spleen injury in nonfederal short-stay hospitals in any of the 27 states participating in KID (N = 2851). MAIN OUTCOME MEASURE: Splenectomy performed within 1 day of arrival. RESULTS: A total of 11 children (3%) with splenic injuries receiving care at children's hospitals underwent splenectomy compared with 383 children (15.4%) cared for at general hospitals (P<.001). After adjusting for patient characteristics, injury severity, and hospital characteristics, splenectomy was more likely among children treated at general hospitals (odds ratio, 5.01; 95% confidence interval, 2.21-11.36) than among children treated at children's hospitals. CONCLUSIONS: There is considerable variation in the management of pediatric splenic injuries, with significantly lower rates of splenectomy at designated children's hospitals. Quality improvement interventions, including increased education and training for physicians in general hospitals, may be needed to increase the use of spleen-conserving management practices.

Adolescent↗
PubMed2005

Impairment of specific episodic memory processes by sub-psychotic doses of ketamine: the effects of levels of processing at encoding and of the subsequent retrieval task.

RATIONALE: The precise nature of the impact of the N-methyl-D-aspartate antagonist, ketamine, upon human episodic memory, has yet to be elucidated fully. OBJECTIVES: This study sought to assess the effects of ketamine on the sub-processes facilitating memory encoding and retrieval. METHODS: We evaluated the effects of the drug on a series of memory performance measures depending upon whether it was administered at the encoding or retrieval stage and on the nature of the encoding task used. Twelve healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. Intravenous infusions of placebo, 50 ng/ml ketamine or 100 ng/ml ketamine were administered. We investigated the effects of ketamine on three key aspects of episodic memory: encoding vs retrieval processes, source memory, and depth of processing. Data were analysed using both multinomial modelling and standard measures of item discrimination and response bias. RESULTS: Deleterious effects of ketamine on episodic memory were primarily attributable to its effects on encoding, rather than retrieval processes. Recognition memory was impaired for items encoded at an intermediate level of processing, but preserved for shallowly and deeply encoded items. Increased source guessing bias was also observed when encoding took place under ketamine. CONCLUSIONS: The effects of ketamine upon episodic memory seem, therefore, to predominate at encoding. Furthermore, our results are also consistent with a specific impairment of encoding processes that result in subsequent recollective, as opposed to familiarity-based, retrieval. The observed effects are compatible with memory deficits seen in schizophrenia and thus provide some support for the ketamine model of the disease.

Adolescent↗
PubMed2005

Hemorrhage control in arteries using high-intensity focused ultrasound: a survival study.

High-intensity focused ultrasound (HIFU) has been shown to provide an effective method for hemorrhage control of blood vessels in acute animal studies. The objective of the current study was to investigate the long-term effects of HIFU-induced hemostasis in punctured arteries. The femoral arteries ( approximately 2mm in diameter) of 25 adult anesthetized rabbits were surgically exposed, and either punctured and treated with HIFU (n=15), served as control (no puncture and no HIFU application: n=7), or were punctured and left untreated (n=3). Treated animals were allowed to recover, and examined and/or sacrificed on days 0, 1, 3, 7, 14, 28, and 60 after treatment to obtain ultrasound images and samples of blood and tissue. Hemostasis (arrest of bleeding) was achieved in all 15 of the HIFU-treated arteries. Eleven of the arteries were patent after HIFU treatment, and four arteries were occluded, as determined by Doppler ultrasound. The median HIFU application time to achieve hemostasis was 20s (range 7-55 s) for the patent arteries and 110 s (range 50-134 s) for the occluded arteries. In untreated animals, bleeding had not stopped after 120 s. One of the occluded arteries had reopened by day 14. No immediate or delayed re-bleeding was observed after HIFU treatment. Maximal blood flow velocities were similar in HIFU-treated patent vessels and control vessels. No significant difference in hematocrits was found between HIFU-treated and control groups at different time points after the procedure. Light microscopy observations of the HIFU-treated arteries showed disorganization of adventitia, and coagulation and thinning of the tunica media. The general organization of the adventitia and tunica media recovered to normal appearance within 28 days, with some thinning of the tunica media observed up to day 60. Neointimal hyperplasia was observed on days 14 and 28. The results show that HIFU can produce effective and long-term (up to 60 days) hemostasis of punctured femoral arteries while preserving normal blood flow and vessel wall structure in the majority of vessels.

Animals↗
PubMed2005

Influence of definition and location of hypotension on outcome following severe pediatric traumatic brain injury.

OBJECTIVE: To examine the influence of definition and location (field, emergency department, or pediatric intensive care unit) of hypotension on outcome following severe pediatric traumatic brain injury. DESIGN: Retrospective cohort study. SETTING: Harborview Medical Center (level I pediatric trauma center), Seattle, WA, over a 5-yr period between 1998 and 2003. PATIENTS: Ninety-three children <14 yrs of age with traumatic brain injury following injury, head Abbreviated Injury Score > or = 3, and pediatric intensive care unit admission Glasgow Coma Scale score <9 formed the analytic sample. Data sources included the Harborview Trauma Registry and hospital records. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The relationship between hypotension and outcome was examined comparing two definitions of hypotension: a) systolic blood pressure <5th percentile for age; and b) systolic blood pressure <90 mm Hg. Hospital discharge Glasgow Outcome Score <4 or disposition of either death or discharge to a skilled nursing facility was considered a poor outcome. Pediatric intensive care unit and hospital length of stay were also examined. Systolic blood pressure <5th percentile for age was more highly associated with poor hospital discharge Glasgow Outcome Score (p = .001), poor disposition (p = .02), pediatric intensive care unit length of stay (rate ratio 9.5; 95% confidence interval 6.7-12.3), and hospital length of stay (rate ratio 18.8; 95% confidence interval 14.0-23.5) than systolic blood pressure <90 mm Hg. Hypotension occurring in either the field or emergency department, but not in the pediatric intensive care unit, was associated with poor Glasgow Outcome Score (p = .008), poor disposition (p = .03), and hospital length of stay (rate ratio 18.7; 95% confidence interval 13.1-24.2). CONCLUSIONS: Early hypotension, defined as systolic blood pressure <5th percentile for age in the field and/or emergency department, was a better predictor of poor outcome than delayed hypotension or the use of systolic blood pressure <90 mm Hg.

Abbreviated Injury Scale↗
PubMed2004

Modulation of thermal pain-related brain activity with virtual reality: evidence from fMRI.

This study investigated the neural correlates of virtual reality analgesia. Virtual reality significantly reduced subjective pain ratings (i.e. analgesia). Using fMRI, pain-related brain activity was measured for each participant during conditions of no virtual reality and during virtual reality (order randomized). As predicted, virtual reality significantly reduced pain-related brain activity in all five regions of interest; the anterior cingulate cortex, primary and secondary somatosensory cortex, insula, and thalamus (p<0.002, corrected). Results showed direct modulation of human brain pain responses by virtual reality distraction.

Adolescent↗
PubMed2004

Water-friendly virtual reality pain control during wound care.

Recent research suggests that entering an immersive virtual environment can serve as a powerful nonpharmacologic analgesic for severe burn pain. The present case study describes an attempt to use water-friendly virtual reality (VR) technology with a burn patient undergoing wound care in a hydrotherapy tub. The patient was a 40-year-old male with 19% total body surface area deep flame/flash burns to his legs, neck, back, and buttocks. The virtual reality treatment decreased the patient's sensory and affective pain ratings and decreased the amount of time spent thinking about his pain during wound care. We believe that VR analgesia works by drawing attention away from the wound care, leaving less attention available to process incoming pain signals. The water-friendly VR helmet dramatically increases the number of patients with severe burns that could potentially be treated with VR (see http://www.vrpain.com).

Adult↗
PubMed2004

Blocking of up-regulated ICAM-1 does not prevent macrophage infiltration during Wallerian degeneration of peripheral nerve.

Circulating blood monocytes infiltrate into distal degenerating nerve and differentiate into activated macrophages that remove degenerating axonal and myelin debris and promote axonal regeneration. The cellular and molecular mechanisms responsible for this monocyte-macrophage recruitment remain largely unknown. Cell adhesion molecules which mediate monocyte and endothelial cell interactions, such as the endothelial cell adhesion molecule intercellular adhesion molecule-1 (ICAM-1) interaction with the monocyte adhesion molecules Mac-1 (complement receptor type 3) and LFA-1 (lymphocyte function-associated antigen-1), have been shown to play a critical role in mediating the transendothelial migration of circulating monocytes into nonneural tissues following various types of injury. This study investigated whether these cell adhesion molecules also play a critical role in mediating monocyte-macrophage infiltration during Wallerian degeneration of peripheral nerve. Following sciatic nerve transection, Mac-1- and LFA-1-positive macrophages in distal degenerating nerve increased in number at 2 days and peaked at 14 days before declining. The number of ICAM-1-immunostained blood vessels increased maximally at 1 day before declining to baseline levels by 14 days. Three days following nerve transection, the intensity of ICAM-1 immunostaining on intraneural blood vessels was maximal and then decreased to baseline levels by 14 days. To test the role of ICAM-1 in mediating monocyte-macrophage recruitment, we used two complementary experimental strategies following a sciatic nerve transection: (1) intravenous administration of a rat ICAM-1-blocking monoclonal antibody and (2) ICAM-1 knockout mice. In both cases, the number of infiltrating monocytes-macrophages was above controls, which is opposite to what has been shown to occur in other tissues following injury.

Animals↗
PubMed2004

Manipulating presence influences the magnitude of virtual reality analgesia.

Excessive pain during medical procedures performed in unanesthetized patients is frequently reported, but can be reduced with virtual reality (VR) distraction. Increasing the person's illusion of going into the virtual world may increase how effectively VR distracts pain. Healthy volunteers aged 18-20 years participated in a double-blind between-groups design. Each subject received a brief baseline thermal pain stimulus, and the same stimulus again minutes later with either a Low Tech or a High Tech VR distraction. Each subject provided subjective 0-10 ratings of cognitive, sensory and affective components of pain, and rated their illusion of going inside the virtual world. Subjects in the High Tech VR group reported a stronger illusion of going into the virtual world (VR presence) than subjects in the Low Tech VR group, (4.2 vs. 2.5, respectively, P = 0.009) and more pain reduction (reduction of worst pain is 3.1 for High Tech VR vs. 0.7 for Low Tech VR, P < 0.001). Across groups, the amount of pain reduction was positively and significantly correlated with VR presence levels reported by subjects ( r = 0.48 for 'worst pain', P < 0.005).

Adolescent↗
PubMed2004

Virtual reality hypnosis: a case report.

This preliminary case report explored the use of hypnosis induced through a 3-dimensional, immersive, computer-generated virtual reality (VR) world as a means to control pain and anxiety in a patient with a severe burn injury. On hospitalization Day 40, after reports of uncontrollable pain and anxiety, the patient underwent hypnotic induction while immersed in a virtual world and received posthypnotic suggestions for decreased pain and anxiety during subsequent wound-care sessions. The patient's pain and anxiety each dropped 40% after VR hypnosis on a Graphic Rating Scale for his Day 41 wound care. Pain dropped similar levels on Day 42 with an audio-only version of the intervention and then returned to baseline without intervention on Day 43.

Adult↗
PubMed2004

High-intensity ultrasound treatment of blunt abdominal solid organ injury: an animal model.

BACKGROUND: High-intensity focused ultrasound (HIFU) is effective in producing hemostasis in injuries from organ lacerations and punctures in animals but has not been evaluated in impact injuries. METHOD: High-energy blows were applied to 11 heparinized and anesthetized pigs, resulting in solid organ injury. HIFU was applied to injuries via laparotomy. The animals were closed, administered saline, observed under general anesthesia for 3.6 +/- 0.4 hours, reopened, and inspected, and abdominal free fluid was aspirated. RESULTS: Organ hemostasis was achieved (mean +/- SD) with 15 +/- 6 minutes of HIFU treatment and 54 +/- 3 minutes of operating time, and 18.8 +/- 13.1 mL/kg of blood was recovered from the abdomen. One animal died from an untreated occult injury to a large vein. HIFU-treated sites were hemostatic at relaparotomy, with 8.6 +/- 6.2 mL/kg abdominal serosanguinous fluid recovered. CONCLUSION: HIFU is effective in producing hemostasis by direct treatment of injured parenchyma in blunt trauma.

Abdominal Injuries↗
PubMed2004

Association of hospital trauma designation with admission patterns of injured children.

BACKGROUND: Little is known about the influence of regionalization of trauma care on pediatric trauma care delivery. The purpose of this study was to estimate whether formal adoption of a statewide trauma system was associated with hospital admission patterns of injured children. METHODS: A longitudinal study of children who were residents of Washington State during 1989 to 1999 was conducted. The main outcome measure was hospital admission for trauma. RESULTS: During the 11-year period, there were 24,955 admissions. Admission rates of injured children to pediatric-designated trauma hospitals decreased by 20%, rates at adult-designated hospitals decreased by 60%, and rates at nondesignated hospitals decreased by 66%. Introduction of the trauma system in 1994 was associated with a 12% increase in admission rates to pediatric-designated hospitals, little change (+1%) in admission rates to adult-designated centers, and an 11% decrease in admissions at nondesignated hospitals. CONCLUSION: Trauma designation in Washington was associated with a shift in admissions from nondesignated hospitals to pediatric trauma hospitals.

Adolescent↗
PubMed2003

Subdissociative dose ketamine produces a deficit in manipulation but not maintenance of the contents of working memory.

We investigated the effects of subdissociative dose ketamine on executive processes during a working memory task. A total of 11 healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. They attended on three occasions, receiving intravenous infusions of placebo, a lower ketamine dose, and a higher ketamine dose. On each occasion, they underwent a series of tasks engaging working memory function in verbal and visuo-spatial domains. Further tasks explored aspects of long-term memory, planning, attention, and perceptual processing. With respect to working memory/executive function, a highly specific pattern of impairment was observed. Impairments were seen only at the higher dose of ketamine and restricted to a subgroup of the verbal working memory tasks: While visuo-spatial working memory showed no evidence of impairment, and while simple maintenance processes during verbal working memory were also unimpaired, higher dose ketamine produced a significant impairment in the manipulation of information within working memory. This process-specific effect of ketamine was reflected in a drug-by-task interaction. The specificity of this ketamine effect suggests that the earliest effect of NMDA receptor blockade is in higher order control of executive function rather than in more basic maintenance processes.

Adolescent↗
PubMed2003

The illusion of presence in immersive virtual reality during an fMRI brain scan.

The essence of immersive virtual reality (VR) is the illusion it gives users that they are inside the computer-generated virtual environment. This unusually strong illusion is theorized to contribute to the successful pain reduction observed in burn patients who go into VR during woundcare (www.vrpain.com) and to successful VR exposure therapy for phobias and post-traumatic stress disorder (PTSD). The present study demonstrated for the first time that subjects could experience a strong illusion of presence during an fMRI despite the constraints of the fMRI magnet bore (i.e., immobilized head and loud ambient noise).

Adult↗