Biomedical subjects
G R Harrison
Publications and source records attributed to G R Harrison.
Real-time breath monitoring of propofol and its volatile metabolites during surgery using a novel mass spectrometric technique: a feasibility study.
BACKGROUND: At present, there is no rapid method for determining the plasma concentration of i.v. anaesthetics. A solution might be the measurement of the anaesthetic concentration in expired breath and its relation to the plasma concentration. We used chemical ionization methods to determine whether an i.v. anaesthetic can be detected in the low concentrations (parts per billion by volume) in the expired breath of an anaesthetized patient. METHOD: Chemical ionization mass spectrometry can measure trace gases in air with high sensitivity without interference from major gases. We carried out a feasibility trial with a proton transfer reaction mass spectrometer (PTR-MS) to monitor the i.v. anaesthetic agent propofol and two of its metabolites in exhaled gas from an anaesthetic circuit. Exhaled gas was sampled via a 4 m long, unheated tube connected to the PTR-MS. RESULTS: Propofol and its metabolites were monitored in real time in the expired breath of patients undergoing surgery. CONCLUSION: Routine measurement of i.v. agents, analogous to that for volatile anaesthetic agents, may be possible.
The effect of posture on cerebral oxygenation during abdominal surgery.
Performing surgery with a patient in the head-down position for several hours may cause marked facial and conjunctival oedema. It is not known whether oedema might also be occurring within the cranial cavity. This study, using near-infrared regional cerebral oximetry, was performed to see if there was any evidence of cerebral anoxia during operations performed with patients in the head-down position compared with those performed on patients who were flat. Patients managed in the head-down position did not demonstrate any reduction in regional cerebral oxygenation, but those who were managed flat did. An explanation of these paradoxical findings is elusive.
The contamination of volatile anaesthetics in an in-circle vaporizer with water during prolonged closed-circle anaesthesia.
The amount of water present in sevoflurane in an in-circle vaporizer after long procedures was measured. This demonstrated that the sevoflurane residue was contaminated with a small amount of water.
Tunnelled epidurals.
Explore the source record for details and available documents.
The use of epidural ropivacaine in high doses for the management of pain from invasive carcinoma of the cervix.
A case is presented of a young woman with advanced cervical cancer invading the rectum and sacral nerves giving rise to an intractable pain state. The management of her symptoms using a domicillary infusion of diamorphine with high doses of ropivacaine is described. It is believed that this is the first presentation of ropivacaine being used in daily doses approaching 2 g, and the associated problems are discussed.
Topographical anatomy of the lumbar epidural region: an in vivo study using computerized axial tomography.
The lumbar epidural region was studied using computerized tomography. This technique allows examination of the region in vivo. It confirmed that the spinal canal is oval in the upper lumbar region, becoming triangular lower down, and that the ligamenta flava form a posterior recess to the vertebral canal. Epidural fat is confined to this region between the ligamenta flava and the intervertebral foramina, and the dura mater lies apposed to the walls of the vertebral canal except where there is epidural fat. The absence of a posterior midline fold of dura mater was noted, and discussed in the light of other studies.
Chiropractic biophysics technique: a linear algebra approach to posture in chiropractic.
OBJECTIVE: This paper discusses linear algebra as applied to human posture in chiropractic, specifically chiropractic biophysics technique (CBP). MATHEMATICAL ANALYSIS: Rotations, reflections and translations are geometric functions studied in vector spaces in linear algebra. These mathematical functions are termed rigid body transformations and are applied to segmental spinal movement in the literature. Review of the literature indicates that these linear algebra concepts have been used to describe vertebral motion. However, these rigid body movers are presented here as applying to the global postural movements of the head, thoracic cage and pelvis. CONCLUSION: The unique inverse functions of rotations, reflections and translations provide a theoretical basis for making postural corrections in neutral static resting posture. Chiropractic biophysics technique (CBP) uses these concepts in examination procedures, manual spinal manipulation, instrument assisted spinal manipulation, postural exercises, extension traction and clinical outcome measures.
Inhaled opiates.
Explore the source record for details and available documents.
Epidural pressure.
Explore the source record for details and available documents.
A model of the extradural space and a reappraisal of the extradural space pressure.
A model is described which was used to study the genesis of the pressure in the extradural space. It consists of a Perspex outer tube, with perforations covered with rubber septa to allow the insertion of needles, and Paul's tubing on the inside, representing the dura mater. The Paul's tubing is filled with water through a constant head of pressure apparatus. The response of the model to the insertion of an extradural needle and the reproduction of various clinical phenomena are described. The pressure in the extradural space is discussed in relation to the performance of the model.
Paradoxical air embolus.
Explore the source record for details and available documents.
Resin injection studies of the lumbar extradural space.
Two resin injection studies of the lumbar extradural space were performed to elucidate its size and shape. To counteract the lack of cerebrospinal fluid pressure in the cadaver, the subarachnoid space was filled with water. In group 1, the extradural injection of resin caused an immediate increase in subarachnoid pressure. The casts produced varied in thickness, but were situated predominantly in the dorsomedial and dorsolateral regions of the spinal canal. Thin anterior spread occurred in 40% of cases. In group 2, resin was injected to the subarachnoid space before the extradural injection of dyed resin. The resulting extradural casts were thinner than in group 1, but the distribution of resin was similar. The problems of interpreting resin casts are discussed in relation to the results obtained, with reasons for suggesting that the extradural space is only potential.
The depth of the lumbar epidural space from the skin.
The depth of the epidural space at different intervertebral interspaces was measured in 1000 parturients. Overall the median distance from the skin to the epidural space was 4.7 cm, but this varied with the lumbar interspace at which it was measured, being greatest at the third (L3-4) interspace (4.93 cm) and least at the first (L1-2) interspace (4.23 cm). The clinical significance of these findings is discussed.
Phaeochromocytoma in a child.
Explore the source record for details and available documents.
The topographical anatomy of the lumbar epidural space.
Although clinically important, the lumbar epidural space is inconsistently described in textbooks of both anatomy and anaesthetics. This anatomical study of twelve cadavers was performed in an attempt to clarify the description of this region. The dura mater, which possesses a midline fold in a very few cases, is apposed to the walls of the vertebral canal, and attached to them by connective tissue, which is sufficient to allow for displacement of the dural sac during movement of the spine and venous engorgement. Between the dura mater and the vertebral canal is a thin layer of areolar tissue. This contains the internal vertebral venous plexus and a posterior deposit of fat which lies in a recess between the ligamenta flava. These findings are discussed in relation to previous studies in an attempt to arrive at a cohesive description of the epidural region.
Adverse reaction to methohexitone and gallamine.
A case is presented in which a patient developed an acute anaphylactoid reaction after receiving methohexitone and gallamine for the induction of anaesthesia. The problem of eliciting the responsible agent is discussed, which comments on the method of treatment and preventative measures.