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Biomedical subjects

M V Merrick

Publications and source records attributed to M V Merrick.

At least 37 records · Page 2Linked to original sources
PubMed1993

99mTc-MDP scintigraphy in ankylosing spondylitis.

99mTechnetium-MDP bone scintigrams in 11 patients with ankylosing spondylitis were reviewed. Increased activity in sacroiliac joints was present in five of 11 cases, all of whom had symptoms of less than 5 years duration. Patients with longstanding disease had normal or low sacroiliac joint activity. In the spine, appearances included diffuse symmetrical, unifocal or multifocal asymmetrical increased uptake involving the costovertebral, costotransverse and facet joints as well as the spinous processes. In advanced disease with extensive ankylosis, the lumbar spine was featureless on scintigraphy, except for focal increased activity at the site of previous fracture in one patient. Of six available views of the sternum, increased uptake was present in five at the manubriosternal joint and five at the sternoclavicular joints. Increased peripheral uptake was mainly in the hips and knees in advanced cases. Plain radiographic changes correlated poorly with scintigraphic changes, scintigraphy detecting considerably more lesions than radiography. Awareness of the scintigraphic appearances of ankylosing spondylitis may lead to diagnosis before the development of radiographic changes and avoid confusion with other pathology. Clinical indications for bone scintigraphy in ankylosing spondylitis are suggested.

Adult↗
PubMed1993

Immediate effects of carotid clamp release on middle cerebral artery blood flow velocity during carotid endarterectomy.

Transcranial Doppler ultrasound was employed in 44 patients undergoing carotid endarterectomy in order to identify factors associated with the greatest increases in middle cerebral artery blood flow velocity (MCAV) immediately after carotid clamp release and restoration of flow. Previous reports have suggested that such increases might reflect post-ischemic hyperaemia. Overall, the median increase in MCAV on restoration of flow [58 cm/s (95% Cl 44-68)] was greater than the median decrease in MCAV after initial carotid clamping [36 cm/s (95% Cl 26-43), p < 0.0001]. However, the immediate increase in MCAV tended to be transient and, in one patient, may have represented a hyperaemic response to a haemodynamically induced intraoperative neurological deficit. There was no association between the magnitude of MCAV increase and clinical presentation, degree of carotid stenosis, computed tomography scan findings, type of anaesthesia, nor the presence or absence of impaired cerebral vascular reserve, nor the occurrence of intraoperative air embolisation. The greatest increases in MCAV on clamp release were observed in patients with the greatest decreases in MCAV at clamping and those with the lowest internal carotid artery stump pressures. The most likely explanation for the findings is that they represent a transient hyperaemic response to carotid occlusion. It remains unclear whether this phenomenon is mediated by some degree of ischaemic injury or simply by the effect of a sudden surge of blood through low resistance arterioles that have dilated in order to maintain the collateral circulation during carotid clamping.

Blood Flow Velocity↗
PubMed1993

Patterns of bone metastasis and their prognostic significance in patients with carcinoma of the prostate.

The different patterns of bone metastasis, metastatic load and their prognostic significance were examined in a consecutive series of 169 men with prostatic cancer and bone metastasis at presentation. Patients with an isolated metastasis in the pelvis or dorsal vertebrae had a better prognosis than those whose metastases were either diffuse or involved more distal sites such as the skull or the sternum, although all of these patients were classified as having M1 disease. Bone metastasis involving an area equivalent to 1 vertebral body equalled a metastatic load of 2. Based on their total metastatic load, 3 prognostic groups were identified with significant differences in case-specific survival despite receiving the same hormonal treatment. When comparing the potential efficacy of various treatments one must stratify the metastatic load, which is a powerful prognostic indicator of the outcome in patients with metastatic carcinoma of the prostate.

Bone Neoplasms↗
PubMed1992

Investigation of joint disease.

The role of nuclear medicine in the diagnosis and management of the major arthropathies is critically reviewed, with particular reference to osteoarthritis, rheumatoid and similar forms of arthritis, ankylosing spondylitis, non-specific back pain, gout, the neuropathic joint, avascular necrosis, infection and the consequences of prosthetic joint insertion. Attention is drawn both to practical applications and deficiencies in current techniques and knowledge.

Adult↗
PubMed1992

A method of computerised isotope dynamic proctography.

Patients with long-standing constipation were examined by radioisotope proctography. A radiolabelled synthetic potato mash was inserted intrarectally and the dynamic changes during simulated defaecation recorded using a gamma-camera. Computer images from the stored data illustrate changes in the anorectal angle and pelvic floor. The median (and 95% confidence intervals) of the anorectal angles were: at rest 105 degrees (101 degrees, 116 degrees), on voluntary contraction of the pelvic floor by 'squeezing' 91 degrees (81 degrees, 98 degrees), on straining 120 degrees (107 degrees, 137 degrees) and during evacuation 126 degrees (116 degrees, 153 degrees). The pelvic floor movements were: pelvic floor ascent on voluntary contraction 28 mm (9, 34 mm), pelvic floor descent on straining -8 mm (-14, -4 mm) and descent during evacuation -27 mm (-34, -11 mm). Useful additions to previous methods are measurement of the completeness of rectal evacuation 58% (42, 77%), the defaecation time 64 s (50, 138 s) and the defaecation rate 0.9%/s (0.4, 1.4%/s).

Anal Canal↗
PubMed1992

In vivo effect of calcitonin gene related peptide on middle cerebral artery blood flow velocity in humans.

A double blind, placebo controlled, escalating dose study was undertaken in five healthy, conscious volunteers to investigate the effects of human synthetic alpha calcitonin gene-related peptide (CGRP) on middle cerebral artery (MCA) blood flow velocity using transcranial Doppler sonography. During placebo infusion, there was no significant change in any of the parameters studied. During CGRP infusion, all subjects showed flushing of the face and neck. Infusion of CGRP caused a significant increase in arterial pulse pressure and heart rate and a fall in diastolic and mean arterial blood pressure when compared to baseline. Peak and mean MCA velocity did not change significantly. There was a significant increase in pulsatility index though interpretation of this was confounded by the central systemic effects of CGRP. The observed haemodynamic changes may be explained by a prompt sympathetic nervous system response in order to maintain mean arterial blood pressure. Our data suggest that if cerebral vasodilatation had occurred, it was not associated with increased blood flow as an increase in MCA velocity might have been expected. An alternative explanation is that, at the doses employed, CGRP did not cause dilatation of normal cerebral vessels in healthy subjects. This does not however exclude the fact that CGRP may cause dilatation of a spastic artery as seen in cerebral vasospasm following subarachnoid haemorrhage.

Journal Article↗
PubMed1991

Parametric imaging of cerebral vascular reserve. 2. Reproducibility, response to CO2 and correlation with middle cerebral artery velocities.

We report the reproducibility and response to change in end-tidal CO2 of a new method of quantifying regional mean cerebral transit time (MCTT) compared with the reproducibility and CO2 reactivity of middle cerebral artery (MCA) blood flow velocities measured using transcranial Doppler ultrasound. Within the range of end-tidal CO2 which could be achieved in conscious subjects breathing spontaneously, hemispheric MCTT, peak MCA velocity and mean MCA velocity showed a linear relationship with end-tidal CO2. After correction to a standardised end-tidal CO2, the coefficients of variation were 5.7% for hemispheric MCTT, 6.3% for peak MCA velocity and 6.8% for mean MCA velocity. Under the conditions of this study, MCA blood flow velocity was proportional to the reciprocal of MCTT, which in turn represents the ratio of blood flow to blood volume. Although the two methods appear to provide similar information, measurement of MCTT is quicker to perform, is less observer-dependent, provides regional information, uses conventional equipment present in most nuclear medicine departments and is less subject to problems associated with patient movement.

Adult↗
PubMed1991

Parametric imaging of cerebral vascular reserves. 1. Theory, validation and normal values.

We describe the theoretical basis and practical details of a method for creating parametric images of the ratio of regional cerebral blood flow (rCBF) to volume (rCBV) from planar gamma-camera images following intravenous injection of any intravascular tracer and after correction for dispersion of the bolus before it arrives at the head. This ratio, which is the most sensitive index of the extent to which perfusion is being maintained by vasodilatation in patients with cerebro-vascular disease, indicates whether the limits of compensation have been, or are in danger of being, exceeded and identifies any ischaemic penumbra. Evidence is provided of the validity of the correction and the accuracy of calculation of the ratio. The range of normal values established is not significantly different from that previously reported using positron emission tomography. This technique has proved sufficiently sensitive to be clinically useful in patients with abnormalities of cerebral perfusion.

Brain↗
PubMed1991

Risk factors for intra-operative neurological deficit during carotid endarterectomy.

Although embolism is considered to be the major cause of intra-operative neurological deficit (IOND) during carotid endarterectomy, the possibility that patients may vary in susceptibility to ischaemic damage following minor embolisation or falls in cerebral perfusion pressure is rarely considered. A prospective study was undertaken in 60 consecutive patients undergoing carotid endarterectomy to identify risk factors for IOND. The hypothesis was that patients with impaired cerebral vascular reserve (CVR) may be more vulnerable to intra-operative emboli or falls in cerebral perfusion pressure than normal subjects. Recent work using Positron Emission Tomography has indicated that the best index of CVR is the ratio of cerebral blood flow to cerebral blood volume, which is another expression for the reciprocal of mean cerebral transit time (MCTT). In this study, a new isotopic method of quantifying MCTT was used to identify patients with impaired CVR. Six patients (10%) recovered from anaesthesia with an IOND, only one of which was disabling. Significant risk factors for IOND were: (i) age over 65 years (Odds Ratio 13.0 (95%CI 1.4-121), p = 0.013); (ii) a residual neurological deficit prior to operation (Odds Ratio 7.0 (95%CE 1.1-43), p = 0.038); (iii) complex plaque morphology (Odds Ratio 6.4 (95%CI 1.06-34), p = 0.046); and (iv) the combination of impaired CVR and a CT scan infarct in the symptomatic hemisphere (Odds Ratio 9.8 (95%CI 1.5-62), p = 0.026). These observations suggest that certain risk factors for IOND can be identified preoperatively and this may enable a more discriminating approach to patient selection for operation and a more critical evaluation of operative technique and methods for intra-operative protection and monitoring in the future.

Age Factors↗
PubMed1991

The effects of renzapride, a novel prokinetic agent, in diabetic gastroparesis.

Gastric emptying was measured in 9 diabetic patients with autonomic neuropathy (Group 1) and 8 normal controls (Group 2) on 4 occasions after swallowing placebo, 0.5, 1.0 or 2.0 mg of the newly developed prokinetic drug renzapride given double-blind and in random order. The liquid component of the test meal was labelled with In113m and the solid with Tc99m. Liquid emptying was uni-exponential. Solid emptying comprised an initial lag phase, followed by a linear component. Following placebo, the mean lag phase of solid emptying was 40 +/- 7 (S.E.M.) min in Group 1 and 16 +/- 2 min in Group 2 (P less than 0.01). In Group 1 subjects renzapride reduced the mean lag phase by 20-26 min at all doses (P less than 0.01). No effect was seen in Group 2. The linear rate of solid emptying was similar in both groups (0.9 +/- 0.1 and 1.0 +/- 0.2%/min) and was not altered by renzapride. Mean liquid t1/2 was similar in Groups 1 and 2 after placebo (30 +/- 6 and 29 +/- 4 min, respectively) and was decreased with increasing doses of renzapride in both groups. No adverse effects were encountered in any subjects. Renzapride may be useful in the treatment of diabetic gastroparesis.

Adult↗
PubMed1991

Idiopathic bile acid malabsorption--a review of clinical presentation, diagnosis, and response to treatment.

Between 1982 and 1989, the seven day retention of 75SeHCAT was measured in 181 patients with chronic diarrhoea that remained unexplained after full investigation. Altogether 121 of the 181 had a seven day 75SeHCAT retention greater than or equal to 15% and thus had no evidence of abnormal bile acid turnover. Twenty one had a seven day 75SeHCAT retention greater than or equal to 10% but less than 15%. Their clinical features were typical of the irritable bowel syndrome, and none of eight treated with cholestyramine showed symptomatic improvement. Sixteen patients had a seven day retention greater than or equal to 5% and less than 10%, six of whom had improved symptoms after treatment with bile acid chelating agents. The remaining 23 patients had a 75SeHCAT retention of less than 5% at seven days and responded to bile acid chelators. This group had a characteristic illness with intermittent watery diarrhoea, but no constitutional upset. It was not possible to distinguish the patients with bile acid malabsorption exclusively on the basis of the clinical symptoms and investigations, other than 75SeHCAT retention. We conclude that the measurement of 75SeHCAT retention is useful, appropriate, and necessary in patients with unexplained chronic diarrhoea.

Adolescent↗
PubMed1989

Fluid balance, vasopressin and withdrawal symptoms during detoxification from alcohol.

Nineteen patients were studied during the first 4 days after withdrawal from alcohol. Plasma vasopressin was raised (P less than 0.05) and fluid retention occurred (P less than 0.05), with falls in haematocrit (P less than 0.01) and calculated plasma osmolality (P less than 0.02), which were consistent with expansion of plasma volume. Despite these changes mean total body water was within normal limits although there were substantial inter-individual variations. There was no correlation between any measure of fluid balance and the severity of withdrawal symptoms.

Adult↗