Chronic Administration of Ketamine for Analgesia

Use of the dissociative anesthetic ketamine in subanesthetic doses has demonstrated efficacy in neuropathic pain. This article reviews the scientific and clinical literature on ketamine. Mechanisms of both central and peripheral neuropathic pain are described. Studies of ketamine analgesia in postherpetic neuralgia, phantom pain, complex regional pain syndrome and cancer pain are reviewed. A range of administration methods for ketamine including neuroaxial administration are described.     

Signal processors in duplex sonography: in vitro comparison between analog and digital methods

Using a new flow-test phantom, which respects the acoustic properties of real blood as well as the proximal and distal impedances of body circulation, we assessed the performance of two duplex sonography signal processors on blood-flow measurements. With both the analog and the dynamic signal processor (Fast Fourier Transform), the correlation between duplex sonography and quantitative flow measurements was high (0.96–0.99) for different dynamic conditions (steady or pulsatile blood flow, varying heart rate, blood pressure, and hematocrit) and for different mechanical conditions (silicon tube or animal vessel). The real blood flow was overestimated by duplex sonography the over-estimation was more pronounced with the analog processor (factor 1.87–4.20) than with the digital processor (factor 1.22–1.64,P<0.05). Applied to the study of asymmetric stenoses, the digital processor was not superior to the analog processors described in the literature.     

A high-resolution transrectal ultrasonographic system

The design of a transrectal echographical ultrasound system is described in this paper. This system produces high-quality, gray-scale images of the prostate, seminal vesicles and the bladder. A light, hand-held probe is inserted into the rectum. The probe is covered with a thin latex sheath which is filled with water to obtain excellent acoustic coupling with the wall of the rectum. The transducer, which is placed in the tip, rotates continuously, and this generates an ultrasound beam at 90° to the probe. A balanced arm can be coupled to the probe during this procedure to obtain better position stability and patient comfort. The transducer can be detached. Most of the work has been done for a 5 MHz transducer, but sometimes a 3.5 MHz transducer is used for greater penetration (≈ 9 cm).The transmitting and receiving systems contain unusual circuits. This includes a novel high-voltage pulser that generates the ultrasound pulse, and a simple but flexible variable time-gain control that adjusts the gain in echoes from different depths. A unique gray-scale phantom, that contains a mixture of lossy gel and reflecting objects, has been used routinely to check the performance of the transrectal scanner. This help is achieving excellent images of the prostate and seminal vesicles.     

Quality Assessment of DNA Sequence Data: Autopsy of A Mis-Sequenced mtDNA Population Sample

Published DNA data sets constitute a body of sequencing results resting in silico that are supposed to reflect the variation of (once) living cells. In cases where the DNA variation reported is suspected to be fraught with artefacts, an autopsy of the full body of data is needed to clarify the amount and causes of mis-sequencing. In this paper we elaborate on strategies that allow a clear-cut identification of the problems in severely flawed mtDNA data. This approach is applied, by way of example, to a data set of HVS-I sequences from the Caucasus, published by Nasidze & Stoneking in 2001 . These data bear numerous ambiguous nucleotide positions and suffer from an even higher number of phantom mutations, indicating that severe biochemical problems adversely influenced those sequencing results at the time. Furthermore, systematic omission of sequences with a long C-stretch (incurred by a transition at position 16189) must have severely biased the data set. Since no complete correction of these data has appeared to date, this example of mis-sequencing necessitates circumstantial evidence that is bullet-proof.     

Regional anaesthesia for repeat Caesarean section in a patient with phantom limb pain

The triggering of phantom limb pain by subarachnoid or epidural anaesthesia has been well described leading to the suggestion that neuraxial regional anaesthesia is relatively contraindicated in lower limb amputees. We report our experience of the provision of anaesthesia for repeat Caesarean section on two occasions in such a patient. Intrathecal fentanyl and morphine supplementation of bupivacaine successfully abolished peri-operative phantom limb pain, whereas epidural anaesthesia was associated with recurrence of phantom limb pain upon regression of the block     

Lung corrections in photon beam treatment planning: are we ready?

This paper reviews reasons cited for and against the use of lung corrections. It is suggested that all the reasons cited for not making corrections are no longer viable. A phantom has been designed to simulate the thorax region of a patient at both CT and radiotherapy radiation energies. With this phantom, lung correction factors for the calculation of tumor dose have been measured for a typical lung cancer treatment regimen, and these results are shown to compare favorably with correction factors computed by all the commonly employed correction algorithms. Some algorithms are better than others, and one of the best is the readily hand-calculable generalized power-law TAR method. It is shown that failure to correct for lung transmission can severely limit the integrity of many interinstitutional studies, especially cooperative clinical trials. It is concluded that lung corrections for the calculation of tumor doses in the thorax region should be gradually introduced over the next several years.     

The effects of intrafraction motion on dose homogeneity in a breast phantom with physical wedges, enhanced dynamic wedges, and ssIMRT

PURPOSE: This study attempts to compare how breathing motion affects intact-breast cancer patients between three different treatment techniques and to determine the degree of improvement on dose homogeneity when implementing gating therapy. METHODS AND MATERIALS: A breast phantom and respiratory simulator were designed to simulate respiratory motion to a first-order approximation. Film was used as a dosimeter, and static dosimetry data were used as a control for comparison. Three velocities of the breast phantom were studied, and gating therapy was introduced for each data set. Dose area histograms (DAHs) were calculated for a breast and a "lung" planning target area (PTA), and Normalized Agreement Test (NAT) indices were calculated in reference to the static case. RESULTS: Deviations from the static case were highest if the collimator speed was of the same magnitude as the speed of the target. In general, gating therapy improved dose uniformity to the breast PTA by up to 14% and reduced dose to the "lung" PTA by up to 24%. With step-and-shoot intensity-modulated radiation therapy (ssIMRT), gating the beam may compromise dose coverage of the breast PTA if the timing interval of the gate is too large. Gating the beam decreased NAT indices by 9 for physical wedges, by 16 for enhanced dynamic wedges, and by 6 for ssIMRT. CONCLUSIONS: Both the phantom and respiratory simulator are adequate for showing differences in dose distributions for all three treatment modalities. Gating therapy improves dose homogeneity to the PTAs and decreases the dose delivered to areas below the posterior border of the beams.     

Effects of anesthesia on pain after lower-limb amputation

OBJECTIVE: To evaluate the effects of epidural, spinal, and general anesthesia on pain after lower-limb amputation. DESIGN: Cross-sectional survey. SETTING: Postamputation clinic. PATIENTS: 150 patients who were evaluated one to 24 months after their lower-limb amputation. INTERVENTIONS: Patients received epidural, spinal, or general anesthesia for their amputation. MEASUREMENTS: Standardized questions were used to assess stump pain, phantom sensation, or phantom limb pain preoperatively and postoperatively. Pain intensity was assessed on a verbal rating scale of 0 to 10. After the interview, each patient's medical history and anesthetic record were assessed. RESULTS: Patients who had received epidural anesthesia and those who had received spinal anesthesia recalled significantly less pain in the week after their surgery (P < 0.05). After an average of 14 months, there was no difference in stump pain, phantom limb sensation, or phantom limb pain between patients who received epidural anesthesia, those who received spinal anesthesia, and those who received general anesthesia for their amputation. Phantom limb pain continued to be frequent and severe despite patients' use of opioid analgesics, amitriptyline, and gabapentin. CONCLUSIONS: Patients who received epidural anesthesia and those who received spinal anesthesia recalled better analgesia in the first week after their amputation than did patients who received general anesthesia. Anesthetic technique had no effect on stump pain, phantom limb sensation, or phantom limb pain at 14 months after lower-limb amputation.     

Phantom limb sensation

1. Phantom limb pain and sensations are common in amputees. The present paper defines phantom limb pain, stump pain and phantom limb sensation and then gives an overview of the incidence and characteristics of the phenomena. 2. Theories of phantoms are presented, including peripheral, central and supraspinal theories, with particular attention given to Melzack's neuromatrix. 3. Evidence of cortical reorganization following amputation is given and the extent to which cortical reorganization contributes to phantom limb pain is discussed.