Monitoring urinary bladder temperature.
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Body Temperature↗
Biomedical subjects
F G Shellock
Publications and source records attributed to F G Shellock.
Early central venous pressure changes in the rat during two different levels of head-down suspension.
The head-down suspension (i.e. antiorthostatic hypokinesia) rat is used to simulate the circulatory effects of weightlessness. However, little is known about the early cardiovascular adaptive response to simulated weightlessness and the effects of varying degrees of head-down suspension. Therefore, the purpose of this study was to characterize the early central venous pressure changes to two different levels of head-down suspension in the rat. Unanesthetized, unrestrained, female Sprague-Dawley rats (wt: 298 +/- 18 gms, mean +/- S.D.) with chronically implanted central venous pressure catheters were subjected to either a 45 degrees C head-down tilt angle (Group A, N = 8) or a 20 degrees head-down tilt angle (Group B, N = 8) using the tail-traction technique of head-down suspension. Central venous pressure increased significantly (p less than 0.05) in both groups of rats during head-down suspension with the absolute pressure level significantly (p less than 0.05) higher in Group A rats compared to Group B rats during the first 8 h of the study. At 24 h, the rats in Group B appeared to adapt earlier to head-down suspension because central venous pressure decreased to the previous baseline level whereas it remained increased in Group A rats. We conclude that the level of head-down suspension significantly affects the early central venous pressure response and subsequent cardiovascular adaption to simulated weightlessness in rats.
Animals↗
Myocardial metabolic and hemodynamic effects of intravenous MDL-17,043, a new cardiotonic drug, in patients with chronic severe heart failure.
MDL-17,043, a new inotropic drug with vasodilator properties, has been shown to produce salutary hemodynamic effects in severe heart failure, but its effects on myocardial metabolism are unknown. To determine whether such hemodynamic effects are associated with adverse effects on the myocardial oxygen demand and supply relationship, we evaluated the effects of intravenous MDL-17,043 given in incremental doses to a mean maximum dose of 2.1 mg/kg, in nine patients with severe chronic heart failure. Overall cardiac pump performance was significantly improved by MDL-17,043, as reflected by an 88% increase in stroke work index (17 +/- 11 to 32 +/- 19 gm-m/m2; p less than 0.001), a 43% reduction in left ventricular filling pressure (28 +/- 4 to 16 +/- 5 mm Hg; p less than 0.0001), a 49% reduction in systemic vascular resistance (1832 +/- 490 to 937 +/- 296 dynes-sec-cm-5; p less than 0.0001) with a slight (11%) decrease in mean arterial pressure (86 +/- 17 to 76 +/- 19 mm Hg; p = 0.005) and without significant changes in heart rate (88 +/- 14 to 91 +/- 12 bpm; p = NS). These hemodynamic effects were associated with an 18% reduction in myocardial oxygen consumption (17 +/- 5 to 14 +/- 5 ml/min p = 0.01), a 17% reduction in myocardial arteriovenous oxygen difference (13.2 +/- 2.4 to 10.9 +/- 1.8 volumes %; p = 0.01), and a 120% improvement in external myocardial efficiency (stroke work index/oxygen consumption) (1.0 +/- 0.6 to 2.2 +/- 0.9; p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Technical aspects of the thermodilution method for measuring cardiac output.
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Cardiac Catheterization↗
Patients should not be removed from the respirator during any portion of the hemodynamic evaluation.
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Hemodynamics↗
Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee.
The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.
Humans↗
Extrusion of eye socket magnetic implant after MR imaging: potential hazard to patient with eye prosthesis.
Metallic implants or prostheses can be potentially hazardous during magnetic resonance (MR) imaging because of movement or dislodgment of the foreign object. Magnetic eye implants have been reported to exhibit strong movement when placed in water and exposed to a field of 1.5 T. The authors report a case of orbital implant extrusion possibly caused by the movement of a magnetic orbital implant during MR imaging at 0.5 T.
Aged↗
Dynamic study of the upper airway with ultrafast spoiled GRASS MR imaging.
Dynamic magnetic resonance (MR) imaging of the upper airway was not possible previously because of poor temporal resolution. Recently, a rapid technique has been developed that provides the means to obtain multiple images at different section locations with sufficient image quality and temporal resolution to allow a comprehensive, dynamic study of the upper airway. The authors describe an ultrafast spoiled GRASS (gradient-recalled acquisition in the steady state) pulse sequence for dynamic studies of the upper airway. The authors believe that this procedure has potential for identifying and characterizing upper airway abnormalities such as nonfixed occlusions and/or narrowings that may exist in patients with obstructive sleep apnea.
Humans↗
Phantom limb pain induced in amputee by strong magnetic fields.
An amputee (traumatic) experienced increased phantom limb pain when exposed to the magnetic fields of two magnetic resonance imagers. With a visual analog scale used to measure pain, electric stimulation studies demonstrated that the residual limb was unusually sensitive to subthreshold (for muscle twitch) levels of current. The painful symptoms produced mimicked those experienced in the presence of the imagers.
Adult↗
MR imaging and metallic implants for anterior cruciate ligament reconstruction: assessment of ferromagnetism and artifact.
Magnetic resonance (MR) imaging is contraindicated for patients with certain ferromagnetic implants, primarily because of potential risks related to movement or dislodgment of the devices. An additional problem with metallic implants is the potential image distortion that may affect the interpretation of the MR study. Since MR imaging is frequently useful for the evaluation of postoperative anterior cruciate ligament (ACL) reconstruction, the ferromagnetic qualities and artifacts associated with MR imaging were determined for five metallic orthopedic implants commonly used for this surgery. Only the Perfix interference screw displayed a substantial deflection force and caused extensive signal loss. Images of the knee of one patient with two Perfix screws in place were not interpretable because of the image distortion caused by these implants. Therefore, alternative nonferromagnetic implants should be considered for reconstruction of the ACL.
Anterior Cruciate Ligament Injuries↗
Policies, guidelines, and recommendations for MR imaging safety and patient management. SMRI Safety Committee.
The following are policies, guidelines, and recommendations from the Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) concerning various issues related to magnetic resonance (MR) imaging safety and patient management. These policies, guidelines, and recommendations were developed to provide standardized and consistent information for use by health practitioners involved in clinical MR imaging.
Humans↗
MR imaging of temporomandibular joint abnormalities associated with cervical hyperextension/hyperflexion (whiplash) injuries.
Patients often have temporomandibular joint (TMJ) dysfunction-related symptoms after cervical hyperextension/hyperflexion injuries ("whiplash") caused by rear-end motor-vehicle collisions. To determine abnormalities of the TMJ associated with these injuries, 33 consecutive symptomatic patients (66 joints) with no direct trauma to the jaw, mouth, head, or face due to the accident and no prior history of TMJ dysfunction underwent magnetic resonance (MR) imaging, and the images were retrospectively analyzed. Overall, 29 (88%) patients had some type of TMJ abnormality related to whiplash injury. Displacement of the disk was seen in 37 (56%) of the TMJs as follows: 21 (32%) had anterior displacement with reduction, nine (14%) had anterior displacement without reduction, six (9%) had lateral or medial displacement, and one (2%) had posterior displacement. On T2-weighted images, 43 (65%) TMJs had abnormal joint fluid or edema, predominantly affecting the joint capsule and/or lateral pterygoid muscles. The finding that many of the patients had joint fluid and/or soft-tissue edema indicates that T2-weighted images are especially useful for assessment of patients with a history of whiplash injury.
Adult↗
Warming-up and stretching for improved physical performance and prevention of sports-related injuries.
Competitive and recreational athletes typically perform warm-up and stretching activities to prepare for more strenuous exercise. These preliminary activities are used to enhance physical performance and to prevent sports-related injuries. Warm-up techniques are primarily used to increase body temperature and are classified in 3 major categories: (a) passive warm-up - increases temperature by some external means; (b) general warm-up - increases temperature by nonspecific body movements; and (c) specific warm-up - increases temperature using similar body parts that will be used in the subsequent, more strenuous activity. The best of these appears to be specific warm-up because this method provides a rehearsal of the activity or event. The intensity and duration of warm-up must be individualised according to the athlete's physical capabilities and in consideration of environmental factors which may alter the temperature response. The majority of the benefits of warm-up are related to temperature-dependent physiological processes. An elevation in body temperature produces an increase in the dissociation of oxygen from haemoglobin and myoglobin, a lowering of the activation energy rates of metabolic chemical reactions, an increase in muscle blood flow, a reduction in muscle viscosity, an increase in the sensitivity of nerve receptors, and an increase in the speed of nervous impulses. Warm-up also appears to reduce the incidence and likelihood of sports-related musculoskeletal injuries. Improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance. Maintaining good flexibility also aids in the prevention of injuries to the musculoskeletal system. Flexibility is defined as the range of motion possible around a specific joint or a series of articulations and is usually classified as either static or dynamic. Static flexibility refers to the degree to which a joint can be passively moved to the end-points in the range of motion. Dynamic flexibility refers to the degree which a joint can be moved as a result of a muscle contraction and may therefore not be a good indicator of stiffness or looseness of a joint. There are 3 basic categories of stretching techniques: (a) ballistic--which makes use of repetitive bouncing movements; (b) static--which stretches the muscle to the point of slight muscle discomfort and is held for an extended period; and (c) proprioceptive neuromuscular facilitation - which uses alternating contractions and stretching of the muscles. Each of these stretching methods is based on the neurophysiological phenomenon involving the stretch reflex.(ABSTRACT TRUNCATED AT 400 WORDS)
Athletic Injuries↗
Metallic otologic implants: in vitro assessment of ferromagnetism at 1.5 T.
MR imaging is contraindicated for patients with certain ferromagnetic implants because of potential risks related to movement or dislodgement. This is especially true for metallic implants located in sensitive areas of the body, such as those placed in and around the ear. Therefore, the ferromagnetic qualities of 35 different metallic otologic implants were assessed by placing them individually on a millimeter scale in a plastic petri dish that was slowly moved into the center of a 1.5-T MR imaging system. None of the metallic otologic implants moved during this procedure. The results demonstrate that each of these implants are made from nonferromagnetic materials and do not pose a risk to patients undergoing high-field-strength MR imaging. These data effectively expand the list of metallic implants that appear to be safe for MR imaging.
Cochlear Implants↗
Dual-surface-coil MR imaging of bilateral temporomandibular joints: improvements in the imaging protocol.
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Humans↗
Physiologic changes during high field strength MR imaging.
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Body Temperature↗
Temperature changes caused by MR imaging of the brain with a head coil.
Tissue heating caused by exposure to RF radiation is a primary safety concern in MR imaging. Therefore, to determine temperature changes caused by high field strength MR imaging of the brain with a head coil, we measured body and skin temperatures in 35 patients immediately before and after clinical MR imaging. MR imaging was performed with a 1.5 T MR system using a 28-cm, open-bore RF transmit/receive head coil specifically designed for examinations of the brain. The average body temperature was 36.6 +/- 0.2 degrees C before MR imaging and 36.6 +/- 0.2 degrees C immediately afterward (mean +/- SD, p = not significant). The average forehead skin temperature increased from 32.6 +/- 0.6 to 32.8 +/- 0.5 degrees C (p less than .01), and the average outer canthus skin temperature increased from 32.1 +/- 0.6 to 32.7 +/- 0.6 degrees C (p less than .01) after MR imaging. The highest skin temperature recorded was 34.2 degrees C, and the largest temperature change was +2.1 degrees There were no statistically significant changes in the average skin temperatures of the upper arm and hand. We conclude that patients undergoing MR imaging of the brain with a head coil at the RF radiation exposure we studied experience no significant changes in average body temperature and statistically significant increases in local (i.e., areas within the head coil) skin temperatures. The observed elevations in skin temperatures were physiologically inconsequential.
Body Temperature↗