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Biomedical subjects

M V Merrick

Publications and source records attributed to M V Merrick.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1989

Value of the gamma camera renogram in the differential diagnosis of acute tubular necrosis and rejection in the early post-transplant period. Comparison with biopsy findings.

A group of 128 consecutive patients was identified on whom renal isotope studies had been performed during the first 2 months after renal transplantation and within 7 days of transplant biopsy. The prospective renogram and biopsy reports were reviewed and graded into 4 categories: severe rejection, predominant rejection, predominant acute tubular necrosis (ATN) and pure ATN. Two extreme patterns of renogram were identified: a sharp rise with a fast decline in the first min, attributed to ATN, and a slowly rising curve with no early peak occurring in severe rejection although not specific to this condition. There was a continuous intermediate spectrum. There was no inter-observer variation in gradings at the 2 ends of the spectrum. In the middle part the difference between 2 independent observers never exceeded more than 1 grade. There was good correlation between the biopsy and renogram gradings, with a discrepancy of more than 1 grade in only 5 patients; 2 of these, with severe rejection on the renogram, showed predominant ATN on biopsy, but the final clinical diagnosis was severe rejection (false positive biopsies). Two patients with biopsies showing severe rejection had a sharp initial up-slope in the renograms but a slower down-slope (over 4 min compared with 1 min in true ATN). With better definition of the criteria these renograms would not have been graded as ATN. There was 1 patient in whom no satisfactory explanation for the discrepancy was found (presumed false positive renogram). When properly defined criteria are used to interpret renograms, this simple test is at least as reliable as renal biopsy in differentiating ATN from rejection in the early post-transplant period, especially in the presence of anuria or severe oligurea.

Acute Kidney Injury↗
PubMed1989

Smoking delays gastric emptying of solids.

Oesophageal transit and gastric emptying of liquids and solids was measured in eight normal subjects with a single test meal containing In113 labelled water and an omelette labelled with Tc99m sulphur colloid. Each volunteer was studied, basally, whilst continuously smoking, and while chewing nicotine gum. Neither liquid, nor solid oesophageal transit were affected by smoking, or gum. Liquid gastric emptying occurred exponentially and clearance was not affected by smoking nor gum (mean basal t1/2 17.4 (2.7) (SEM) min, smoking t1/2 16.6 (7.4) min, gum t1/2 12.5 (2.9) min). Gastric emptying of solid had three components. An initial mean lag phase increased from 17.5 (2.7) min, to 27.5 (6.1) min (p less than 0.05) during smoking, but was not prolonged by nicotine gum (17.5 (1.1) min). A subsequent linear emptying phase was also slowed by smoking from a mean of 1.01 (0.15)% min to 0.80 (0.15)% min (p less than 0.05), but was not affected by nicotine gum, 1.06 (0.2)% min. A third complex phase of solid gastric emptying was not analysed. Smoking delays gastric emptying of solids, but not liquids; nicotine is not responsible for this effect. This observation may partly explain the adverse effect of smoking in patients with gastro-oesophageal reflux.

Adult↗
PubMed1989

Cerebral vascular transit time in Alzheimer's disease and Korsakoff's psychosis and its relation to cognitive function.

The cerebral vascular transit time of 17 patients with pre-senile dementia of the Alzheimer type (ATD), nine abstinent patients with alcoholic Korsakoff's psychosis (KOR), and ten age-matched controls was determined by the bolus intravenous injection of pertechnetate. A gamma camera was used to estimate the median transit time (MTT) of the radioactive bolus in a planar (non-tomographic) projection normal to the vertex. The spread of the bolus arriving at the aortic arch was measured independently by a single external detector over the chest, and correction made for the transit time of this input function in calculating the net MTT for the head. Both ATD and KOR groups showed lengthened net MTTs, compatible with reduced cerebral blood flow, and which were correlated with reduced cognitive function. It is concluded that the method employed gives a simple, inexpensive estimate of function-related blood flow to the brain in pre-senile dementia.

Aged↗
PubMed1988

Cardiotoxicity of mitozantrone assessed by stress and resting nuclear ventriculography.

Fourteen patients with advanced breast cancer were treated with a combination of vincristine, mitozantrone and prednisolone. Before, during and after cessation of treatment radionuclide assessment of ventricular performance was obtained at rest, in response to cold pressor-induced stress and on recovery from stress. Six of 14 patients (46%) developed abnormalities of left ventricular ejection fraction (LVEF). One patient developed clinical signs of cardiac failure. Mitozantrone is an active agent in the treatment of advanced breast cancer but it can produce cardiotoxicity. In this particular middle-aged population, changes in LVEF occurred over a wide range of cumulative doses. Further investigation is required to determine the nature and prognosis of this iatrogenic toxicity.

Adult↗