Nurses' assessments and management of pain in children having orthopedic surgery.

The specific aims of this research project were to (a) describe selected verbal, nonverbal, and physiological arousal indicators of the child's pain; (b) describe which pain indicators were most influential to nurses in decision-making about interventions for managing the child's pain; (c) describe pain interventions used by nurses; (d) compare postoperative analgesic orders to recommended dosages for the children; and (e) explore relationships between the child's self-report of pain and medication dosages administered. Subjects included 19 children aged 5-17 years who experienced 20 orthopedic surgical procedures (one child had two surgeries one week apart). Data were collected by staff nurses for the first five days after surgery. Pain levels were reported using the Oucher Scale. Postoperative pain was reported at moderate levels and showed only a gradual decrease throughout the hospital stay. Nonverbal pain indicators included crying and tense face. The child's complaint of pain and reported Oucher scores were most influential in influencing nurses to intervene in the child's pain. Nonpharmacological comfort measures included positioning and reassurance. All children received medications for pain; 49% of the orders were within the recommended therapeutic dosage range. A small but significant correlation was found between the child's reported pain level and the morphine equivalents of pain medication received. Recommendations included development of nursing flow charts that provide space to record pain levels and nursing interventions, in-service education for nurses on nonpharmacological interventions, and further research with a larger sample and a single pain rating scale.

Magnetization transfer contrast imaging of the human leg at 0.1 T: a preliminary study.

Magnetization transfer contrast imaging is an MR technique that capitalizes on interactions between the protons of mobile and macromolecularly bound water molecules. Studies to date, conducted primarily on 4.7 T and 1.5 T MR systems, have yielded results unique from conventional T1- and T2-weighted imaging studies. In this study, performed on a 0.1 T device, a section of lower leg was imaged in 20 normal human subjects and one patient with muscular dystrophy, using both a standard 500/22 gradient-echo sequence and a 500/22 gradient-echo sequence combined with off-resonance radio frequency irradiation designed to elicit magnetization transfer contrast. Results of the two techniques were compared. Our findings suggest that magnetization transfer contrast imaging is feasible at 0.1 T, and that this technique allows reproducible tissue characterization and improves contrast between certain tissues.

Nuclear magnetic resonance and transcutaneous electromagnetic blood flow measurement.

Static and alternating magnetic fields are employed in blood flowmeters using nuclear magnetic resonance (NMR) principles and electromagnetic induction by a moving conductor (TEM). Both techniques require high steady magnetic fields, obtained either from permanent magnets or from electromagnets. A relatively homogeneous magnetic field is needed for NMR, but, though important for calibration, homogeneity is not critical for TEM. NMR is more complex than TEM since it requires radio-frequency and audio-frequency magnetic fields. However, the TEM method requires surface electrodes in contact with the skin, or needle electrodes placed subcutaneously, whereas NMR is contactless. The NMR flowmeter can be calibrated directly, but appropriate and approximate models must be assumed and then solved by computer to quantify blood flow by the TEM flowmeter. Flow in individual vessels is measured a priori in the TEM flowmeter by virtue of the assumed models. To measure flow in individual vessels by NMR, a scanning or ranging method is required, which logically leads to blood flow imaging. The levels of steady, radio-frequency, and audio-frequency magnetic fields used in the two types of flowmeters are low enough so as not to cause any apparent stimulus to human volunteers and patients tested.

In vivo evaluation of nuclear magnetic resonance flowmetry: blood flow through the normal forearm.

A cylindrical crossed-coil nuclear magnetic resonance flowmeter has been developed to measure arterial blood flow through the human forearm. This paper describes the in vivo studies to evaluate the performance of the instrument. Flow rates were comparable to values reported in the literature. The NMR flowmeter is a noninvasive, contactless-type flowmeter and has the advantage of accurate measurement unimpaired by clothing, bandages, or casts. One measurement can be taken in less than 2 min.

The NMR blood flowmeter--design.

Two types of crossed-coil nuclear magnetic resonance (NMR) blood flowmeter detectors have been developed for the noninvasive measurement of blood flow. The first is a cylindrical coil configuration suitable for limb blood measurement. A cylindrical flowmeter (12.5 cm internal diam) operating at a nuclear resonance frequency of 3.2 MHz has been applied to measurement of flow in the forearm. The second type is the flat crossed-coil detector, which retains many of the operational advantages of the cylindrical detector, but is suitable for blood flow measurement of almost any surface of the body. Three flat crossed-coil detectors are described, operating at NMR frequencies of 9, 21.4, and 75 MHz. Two types of intermediate frequency signal processors have been used in the NMR receivers, a simple diode type, and a synchronous detector. The synchronous detector is preferred for its ease of operation and superior stability. Modular detection systems containing transmitter, receiver, post-detector signal conditioning, and power supply have been designed for all of the flat crossed-coil detectors. A self-contained synchronous detector module is included in the 21.4 and 75 MHz systems.

The NMR blood flowmeter--applications.

Nuclear Magnetic Resonance (NMR) permits the noninvasive measurement of blood flow signals unimpaired by clothes, bandages, casts, etc. The cylindrical crossed-coil NMR blood flowmeter was used to measure blood flow through a cross-section of the human forearm. Two calibration procedures are described: one for pulsatile flows and the other for flows with a high non-pulsatile component. Flow measurements from normal arms, from limbs with arterial obstruction, arteriovenous hemodialysis fistulas or other conditions are reported. An application of the flow scanning technique for separation of flow signals from individual arteries (e.g., ulnar and radial) is described. The flat crossed-coil NMR flowmeter was applied to detect blood flow from individual arteries (e.g., brachial, popliteal, etc.). Applications of a ranging technique developed to detect signals at predetermined depths are described.

Exposure of rhesus monkeys to 20 000 G steady magnetic field: effect on blood parameters.

Sixteen monkeys were used in a study to determine the effects, or noneffects, of exposure to a steady magnetic field of 2 T (20 000 G). Arterial and venous blood samples were taken before, immediately after, and several weeks following the test. Blood gas analyses were made of arterial samples, and hemotologic cell data and Technicon SMAC analyses were made of venous samples. Differential and absolute white blood cell counts of segmented neutrophils and lymphocytes were considerably changed during the test, even for monkeys which were not exposed to the magnetic field. These changes have also been observed in monkeys whose environment and daily routine are modified appreciably. Eight of the 16 monkeys were tested twice: first, in the magnet with the magnet turned on, and second, two months later, in the magnet, but with the magnet turned off. A large superconducting magnet (0.63 m i. d. and 1.85 m long warm-air bore) was used, which accommodated two monkeys at one time. Paired-t tests of 45 blood parameters showed no significant differences between the two tests. Exposure to a gradient field compared with exposure to a uniform magnetic field showed no significant differences.

Cancellation of coherent line-frequency noise in evoked potential recordings.

A stimulator for evoked potential recording can become synchronized with the fundamental or harmonics of the line frequency, thus introducing interference which cannot be removed by averaging. Synchronizing the stimulus alternately to the positive-going and negative-going zero-crossing of the line will reduce 60 Hz and odd harmonics, but will not reduce higher even-harmonics. This communication describes a circuit that synchronizes the stimulus to the alternate phases of the line, but also introduces a random delay between zero and one-half the line period, thus reducing the fundamental and higher harmonics as well.