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Biomedical subjects

A Timothy Lovell

Publications and source records attributed to A Timothy Lovell.

5 recordsLinked to original sources
PubMed2006

Splanchnic organ injury during coronary surgery with or without cardiopulmonary bypass: a randomized, controlled trial.

BACKGROUND: We investigated the efficacy of coronary surgery with or without cardiopulmonary bypass in protecting the function of the small intestine, liver, and pancreas. METHODS: Patients were randomized to off-pump coronary artery bypass grafting (OPCAB) or coronary artery bypass grafting with cardiopulmonary bypass (CABG-CPB). Small intestine function was assessed by differential four sugars (O = methyl-D-glucose, D-xylose, L-rhamnose, and lactulose) permeability and absorption tests. Liver function was assessed by monoethylglycinexylidide/lidocaine ratios and by serial measurements of transaminases (aspartate transaminase and alanine-amino transferase), bilirubin, and alkaline phosphatase. Pancreatic function was assessed by serial measurements of insulin/glucagon ratio, amylase, and glucose. Forty patients were recruited (20 per group). RESULTS: Permeability and absorption were more impaired in the OPCAB group immediately after surgery, but returned to baseline levels in both groups by postoperative day 5 (interaction of surgery type and time; p = 0.05 and p = 0.02, respectively). Monoethylglycinexylidide/lidocaine ratios were not different in the two groups. Aspartate transaminase and alanine-amino transferase levels were higher in the CABG-CPB group for the first postoperative day, but levels converged by day 3 (interaction of surgery type and time; p < 0.0001 and p = 0.04, respectively). The bilirubin level for the OPCAB group overshot the CABG-CPB group at 36 hours before returning to a similar level 60 hours postoperatively. Amylase levels were higher in the CABG-CPB group than in the OPCAB group (1.17 times; p = 0.03); other markers of pancreatic function showed no differences between the groups. CONCLUSIONS: Early small intestine function is worse with OPCAB; all functions recover to similar levels in both groups by day 5. Conversely, pancreatic function is worse with the CABG-CPB group than with the OPCAB group. Hepatic metabolic function does not differ by type of surgery to the end of the operation. Postoperative hepatocellular injury was worse with the CABG-CPB group.

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PubMed2005

Use of the Rydel-Seiffer graduated tuning fork in the assessment of vibration threshold in postherpetic neuralgia patients and healthy controls.

BACKGROUND AND AIMS: Afferent large fibre impairment has been reported as a useful predictor of postherpetic neuralgia (PHN) in patients with acute herpes zoster infection, using an electromechanical device to provide quantitative vibrametry. We aimed to demonstrate a clinically significant increase in vibration threshold in individuals with PHN compared to age-matched controls, using the portable and affordable Rydel-Seiffer graduated tuning fork. METHODS: We studied 45 PHN subjects aged over 55 years, and 45 age-matched controls with no history of herpes zoster infection. We excluded subjects with a history of disorders associated with neuropathy or immunocompromise. Measurements were performed at the ulnar styloid process and the head of the first metatarsal on the right side, in a warm room with the subject seated. Readings were taken in triplicate and the data analysed by a repeated measures design. RESULTS: We observed a significant difference in vibration threshold at both wrist and toe between the PHN and control groups (p < 0.001). Age-stratification of subjects produced an increased and clinically useful difference between the two groups at both sites in subjects between 55 and 70 years (p < 0.0001). CONCLUSIONS: We have shown a statistically significant decrease in vibration sensitivity in individuals with PHN aged 55-70 years compared to age-matched healthy controls, using the Rydel-Seiffer graduated tuning fork. A prospective study of patients with acute zoster infection is needed to determine the sensitivity and specificity of the graduated tuning fork in predicting PHN in patients with acute zoster infection.

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PubMed2004

Effect of cardiopulmonary bypass on cortical cerebral oxygenation during coronary artery bypass grafting.

OBJECTIVE: To investigate the changes in cerebral oxygenation during coronary artery bypass grafting (CABG) with normothermic cardiopulmonary bypass (CPB) using near infrared spectroscopy. METHODS: Measurement of cerebral cortical oxygenation changes included concentration of deoxygenated haemoglobin [HHb], oxygenated haemoglobin [O(2)Hb], changes in the redox status of the cytochrome c oxidase [Cyt-Ox], cerebral saturation as expressed by the tissue oxygenation index (TOI), and cerebral blood volume (CBV) as expressed by tissue haemoglobin index (THI). Measurements were performed in 19 consecutive patients undergoing normothermic (34-36 degrees C) CPB. Data were recorded at 0.5s intervals and averaged into 30 s epochs. Data analysis was carried at baseline, 1, 20, and 40 min after start of CPB, at rewarming, on weaning from CPB, and at closing of chest. RESULTS: There were no in-hospital death, neurological deficits, or myocardial infarcts. Compared to baseline, during the entire CPB duration, there was a marked reduction in [O(2)Hb] and CBV which reached their worst level 40 min after initiation of CPB (from -3.03+/-5.1 to -9.25+/-7.20 micromol/l for [O(2)Hb], and a 24% reduction for CBV (both P<0.0001). The deterioration in [O(2)Hb] was recovered by the end of surgery, while the changes in CBV persisted. No significant changes occurred with respect to [HHb], [Cyt-Ox], and TOI. CONCLUSIONS: Conventional CABG is responsible for deterioration in [O(2)Hb], and CBV, which peak at 40-60 min following initiation of CPB. The changes in [O(2)Hb] are reversible whereas the reduction of CBV persists to the end of the surgery. This suggests a transient impairment in the autoregulatory mechanisms controlling cerebral blood flow following discontinuation of cardiopulmonary bypass.

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PubMed2003

Cerebral cortical oxygenation changes during OPCAB surgery.

BACKGROUND: We investigated the changes occurring in cerebral cortical oxygenation during off-pump coronary artery bypass (OPCAB) surgery using near infrared spectroscopy (NIRS). METHODS: Measurement of cerebral cortical oxygenation changes included concentration of deoxygenated hemoglobin [HHb], oxygenated hemoglobin [O(2)Hb], changes in the redox status of the cytochrome c oxidase [Cyt-Ox], cerebral saturation as expressed by the tissue oxygenation index (TOI), and cerebral blood volume (CBV) as expressed by tissue hemoglobin index (THI). Measurements were performed in 23 consecutive patients during grafting of: left anterior descending (LAD setup 1; n = 23), posterior descending (PDA setup 2; n = 17), and Circumflex (Cx setup 3; n = 19) coronary arteries. Measurements were performed before any surgical manipulation (baseline), following positioning of the pressure stabilizer during construction of the distal anastomosis and 2 minutes after the completion of each distal anastomosis with the heart returned to its natural position. RESULTS: There were no in-hospital deaths, neurologic deficits, or myocardial infarcts. Compared to baseline, during LAD grafting there was a marked reduction in [O(2)Hb] [-1.08 (-1.77 to -0.39), mean difference (95% CI) (p < 0.0008)], without a significant change in [HHb]. There was also a 4% reduction in cerebral saturation and a 3% fall in CBV (both p < 0.05). Setup 2 (PDA) was associated with a marked decrease of [O(2)Hb] [-1.92 (-2.95 to -0.88) mean difference (95% CI) (p < 0.0025)], which was accompanied by an increase in [HHb] [1.89 (1.00 to 2.77) mean difference (95% CI) (p < 0.0025)], and a 4% reduction in cerebral saturation (p < 0.0008). Grafting of the Cx was associated with a marked increase in [HHb] [2.85 (1.46 to 4.2) mean difference (95% CI) (p < 0.0025)], with no changes in [O(2)Hb], a 6% reduction in cerebral saturation, and a 12% increase in CBV (both p < 0.05). In all 3 settings, however, the changes were not associated with a modification in the redox state of [Cyt-Ox]. On returning to baseline condition, the changes in [O(2)Hb] and TOI observed in setup 1 persisted, and a significant reduction was observed in the redox state of the [Cyt-Ox] when compared with baseline [-0.08 (-0.14 to -0.02) mean difference (95% CI) (p < 0.002)]. For setups 2 and 3 there was recovery of the cerebral cortical oxygenation. CONCLUSIONS: Grafting of the LAD on the beating heart is responsible for changes in cerebral cortical oxygenation which persist early after returning the heart to its natural position. Grafting of the Cx and PDA result in transient reversible changes. Trendelenburg positioning and right lateral tilting of the operating table during grafting of lateral and posterior walls might have a protective role in preventing cerebral cortical ischemia. Further studies are needed to assess the clinical importance of these observations.

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