Biotin Deficiency in a Patient with Short Bowel Syndrome during Home Parenteral Nutrition

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141489/1/jpen0311.pd

Duplex Ultrasonography to Predict Internal Carotid Artery Stenoses Exceeding 50% and 70% as Defined by NASCET: The Need for Multiple Criteria

Carotid duplex scanning is being used more frequently as the sole preoperative diagnostic imaging modality for patients considered candidates for carotid endarterectomy. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) has demonstrated the benefit of surgical treatment in patients with carotid stenoses exceeding 70%. The purpose of this study was to determine duplex criteria that accurately predict carotid stenoses exceeding 50% and 70% as defined by NASCET arteriographic criteria. One hundred forty-one patients (264 carotid arteries) considered surgical candidates were prospectively studied over a 2-year period by use of both duplex scanning and digital subtraction cerebral arteriography. Carotid artery stenosis was determined by a single radiologist using NASCET arteriographic criteria. Peak systolic velocity (PSV) and enddiastolic velocity (EDV) were measured in the internal carotid (ICA) and common carotid (CCA) arteries by use of duplex scanning. ICA/CCA velocity ratios were calculated for PSV and EDV. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. PSVICA/CCA provided the highest sensitivity, and EDVICA the highest specificity in this study. Arteriographic stenoses exceeding 50% and 70% were reliably predicted with use of these duplex criteria. It is concluded that duplex criteria can predict carotid stenoses exceeding 50% and 70% as defined by NASCET arteriographic criteria. These criteria should be independently validated by other vascular laboratories.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68440/2/10.1177_153857449903300508.pd

Comparative hemodynamic effects of selective superior mesenteric arterial and peripheral intravenous glucagon infusions

This experiment was designed to determine whether any hemodynamic benefits attend administration of equal pharmacologic doses of glucagon (1 [mu]g/kg/m) by continuous intravenous infusion (Group I, n = 6) versus selective intraarterial infusion (Group II, n = 6) via the superior mesenteric artery (SMA) in dogs. Cardiac output, heart rate, mean arterial pressure, total peripheral resistance, pulmonary vascular resistance, superior mesenteric artery flow (SMAQ), SMA vascular resistance, and portal venous pressure were measured at baseline (BL) and at 5, 15, 30, and 45 min during glucagon infusion. SMAQ virtually doubled at 5 min from a baseline of 570 +/- 60 ml/min to 1158 +/- 146 ml/min in Group I (P P P P < 0.05). Changes in systemic hemodynamic parameters, as well as glucagon and glucose levels were not statistically different between Groups I and II at any time period. Glucagon is a potent mesenteric vasodilator and the resultant profound splanchnic hemodynamic effects are as marked during intravenous administration as during selective SMA infusion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25582/1/0000126.pd

Dissociation of glucagon's central and peripheral hemodynamic effects: Mechanisms of reduction and redistribution of canine hindlimb blood flow

Effects of parenterally administered pharmacologic doses of glucagon on canine hindlimb blood flow were studied. Cardiac output (CO), mean arterial pressure (MAP), total peripheral resistance (TPR), common femoral artery flow (CFAQ), common femoral artery resistance (CFAR), percentage shunt in the hindlimb (AVA%) determined by 99mTc microsphere technique, the volume of hindlimb shunt flow (AVAQ), and the volume of hindlimb nutrient capillary flow (NCQ) were determined at baseline and at 10, 20, and 30 min during continuous intravenous infusion of 1 [mu]g/kg/min glucagon (n = 8). Blood glucagon and glucose levels were measured at all time periods. Glucagon infusion significantly increased CO throughout the infusion, while reducing MAP and TPR. Unexpectedly, CFAQ decreased significantly despite the increase in CO. CFAR increased despite the reduction of TPR during glucagon infusion. The reduction of CFAQ was associated with diminished nonshunt hindlimb NCQ and increased AVA%. Changes in CFAQ, AVA%, AVAQ, and NCQ did not correlate in a linear fashion with the changes in either blood glucose or glucagon levels by linear regression analysis. Glucagon appeared to cause a major redistribution of peripheral blood flow. Hindlimb arteriolar dilatation was not an effect of this hormone in this experimental model. Glucagon appeared to have a salutary central hemodynamic effect, but was detrimental to canine extremity perfusion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24416/1/0000686.pd

Protamine reversal of anticoagulation achieved with a low molecular weight heparin. The effects on eicosanoids, clotting and complement factors

Hemodynamic and hematologic effects of protamine reversal of low molecular weight heparin (LMWH) anticoagulation with and without protamine pretreatment, as well as reversal of anticoagulation with unfractionated standard heparin (SH), were studied in canine subjects. Protamine reversal caused less severe thrombocytopenia in the two LMWH groups compared to SH animals, while neutropenia occurred equally in all groups. Cl-esterase inhibitor levels were minimally increased, whereas C3 levels and leucotriene levels were unaltered. TxB2 and 6-keto-PGF1[alpha] increased during protamine reversal of LMWH anticoagulation. TCT and APTT were affected less with LMWH than SH anticoagulation. Anti-Xa levels increased with anticoagulation in all animals, but protamine did not reverse the elevated anti-Xa levels in LMWH anticoagulated dogs to the same degree as occurred with SH anticoagulation. TCT, APTT and bleeding times were normalized by protamine in all animals. Protamine reversal of LMWH anticoagulation with or without protamine pretreatment did not reveal any clear differences in eicosanoids or complement factors compared to SH anticoagulation, although differences in anti-Xa activity clearly separated these two heparins.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26544/1/0000083.pd

Noninvasive evaluation of hand circulation before radial artery harvest for coronary artery bypass grafting

AbstractObjective: Radial artery harvesting for coronary artery bypass may lead to digit ischemia if collateral hand circulation is inadequate. The modified Allen's test is the most common preoperative screening test used. Unfortunately, this test has high false-positive and false-negative rates. The purpose of this study was to compare the results of a modified Allen's test with digit pressure change during radial artery compression for assessing collateral circulation before radial artery harvest. Methods: One hundred twenty-nine consecutive patients were studied before coronary artery bypass operations. A modified Allen's test was performed with Doppler ultrasound to assess blood flow in the superficial palmar arch before and during radial artery compression. A decreased audible Doppler signal after radial artery compression was considered a positive modified Allen's test. First and second digit pressures were measured before and during radial artery compression. A decrease in digit pressure of 40 mm Hg or more (digit ΔP) with radial artery compression was considered positive. Results: Seven of 14 dominant extremities (50%) and 8 of the 16 nondominant extremities (50%) with a positive modified Allen's test had a digit ΔP of less than 40 mm Hg (false positive). Sixteen of 115 dominant extremities (14%) and 5 of 112 nondominant extremities (4%) with a negative Allen's test had a digit ΔP of 40 mm Hg or more with radial artery compression (false negative). Conclusion: Use of the modified Allen's test for screening before radial artery harvest may unnecessarily exclude some patients from use of this conduit and may also place a number of patients at risk for digit ischemia from such harvest. Direct digit pressure measurement is a simple, objective method that may more precisely select patients for radial artery harvest. Additional studies are needed to define objective digital pressure criteria that will accurately predict patients at risk for hand ischemia after radial harvest. (J Thorac Cardiovasc Surg 1999;117:261-6

Glucagon and canine mesenteric hemodynamics: Effects on superior mesenteric arteriovenous and nutrient capillary blood flow

The objective of this investigation was to define the splanchnic hemodynamic effects of parenterally administered glucagon in a canine model. Measurements in six dogs at baseline and at 10, 20, and 30 min during constant intravenous infusion of glucagon at 1 [mu]g/kg/min included: Cardiac output (CO), mean arterial pressure, total peripheral vascular resistance (TPR), superior mesenteric artery flow (SMAQ), portal venous pressure (PVP), superior mesenteric artery vascular resistance (SMAR), percentage SMA flow through arteriovenous anastomoses (AVA%) determined by 99mTc microsphere technique, as well as volume flow through AVA (AVAQ), and volume flow through the SMA nutrient capillary circulation (NCQ). SMAQ rose significantly and disproportionately compared to the rise in CO. SMAQ more than doubled from a mean of 448 +/- 124 cc at baseline to a mean of 921 +/- 321 cc at 10 min, and remained elevated throughout drug infusion. SMAR and TPR both decreased significantly. Although percentage shunt was low at baseline, 1.79 +/- 0.94%, and did not change, both AVAQ and NCQ increased significantly during drug infusion. The increase in AVAQ was transient, but NCQ remained elevated throughout infusion. PVP increased significantly, and the change in PVP correlated significantly with the change in AVAQ at 30 min, a time when AVAQ was not elevated significantly above baseline levels. Nutrient capillary flow comprised >=98% of total SMAQ during the experiment and, along with total SMAQ, doubled and remained elevated throughout drug infusion. Although glucagon may increase PVP by slightly increasing the absolute volume of mesenteric shunt flow, its primary action is that of a potent mesenteric arterial dilator, increasing NCQ strikingly more than AVAQ.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24413/1/0000683.pd

Early derangements of arteriovenous anastomotic and capillary blood flow in the canine hindlimb induced by supplemental pentobarbital anesthesia

Vasoactive effects of supplemental pentobarbital anesthesia in the canine hindlimb microcirculation were documented in two groups of animals previously anesthetized with 30 mg/kg pentobarbital: Group I with a 5 mg/kg intravenous (iv) bolus of pentobarbital (n = 8) and Group II with a 5 mg/kg 2-min iv infusion of pentobarbital (n = 7). In Group I, measurements at baseline (BL) and 5, 15, 20, and 30 min (min) following pentobarbital administration included cardiac output, mean arterial pressure, total peripheral vascular resistance, common femoral artery flow (CFAQ) and resistance (CFAR), percentage hindlimb arteriovenous anastomotic shunt (AVA%), absolute shunt flow (AVAQ), and hindlimb nutrient capillary flow (NCQ). In Group II these same measurements were made, but the study was continued until all hindlimb hemodynamic parameters returned to control values. CFAQ, AVA%, AVAQ, and NCQ were significantly increased, and CFAR was decreased in both groups. CFAQ and NCQ remained significantly elevated at 30 min in Group I. In Group II CFAR, AVA%, and AVAQ remained elevated at 30 min, but did return to BL by 40 min, as did all other hindlimb hemodynamic parameters measured. Pentobarbital resulted in both AVA and arteriolar dilation, with an increase in the percentage total flow distributed to AVAs. These alterations of microcirculatory flow should be considered during investigations of the distribution of peripheral blood flow, as well as during metabolic studies assessing arteriovenous substrate differences, if interpretative errors are to be avoided.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24920/1/0000347.pd

Protocol for PD SENSORS:Parkinson’s Disease Symptom Evaluation in a Naturalistic Setting producing Outcomes measuRes using SPHERE technology. An observational feasibility study of multi-modal multi-sensor technology to measure symptoms and activities of daily living in Parkinson’s disease

Introduction The impact of disease-modifying agents on disease progression in Parkinson’s disease is largely assessed in clinical trials using clinical rating scales. These scales have drawbacks in terms of their ability to capture the fluctuating nature of symptoms while living in a naturalistic environment. The SPHERE (Sensor Platform for HEalthcare in a Residential Environment) project has designed a multi-sensor platform with multimodal devices designed to allow continuous, relatively inexpensive, unobtrusive sensing of motor, non-motor and activities of daily living metrics in a home or a home-like environment. The aim of this study is to evaluate how the SPHERE technology can measure aspects of Parkinson’s disease.Methods and analysis This is a small-scale feasibility and acceptability study during which 12 pairs of participants (comprising a person with Parkinson’s and a healthy control participant) will stay and live freely for 5 days in a home-like environment embedded with SPHERE technology including environmental, appliance monitoring, wrist-worn accelerometry and camera sensors. These data will be collected alongside clinical rating scales, participant diary entries and expert clinician annotations of colour video images. Machine learning will be used to look for a signal to discriminate between Parkinson’s disease and control, and between Parkinson’s disease symptoms ‘on’ and ‘off’ medications. Additional outcome measures including bradykinesia, activity level, sleep parameters and some activities of daily living will be explored. Acceptability of the technology will be evaluated qualitatively using semi-structured interviews.Ethics and dissemination Ethical approval has been given to commence this study; the results will be disseminated as widely as appropriate

Nuclide imaging of vascular graft-platelet interactions: Comparison of indium excess and technetium subtraction techniques

Indium-111-labeled platelet adherence to ePTFE thoracoabdominal vascular prostheses in a canine model (n = 10) was quantitated by (1) an indium-111 excess technique, contrasting graft radioactivity to that in a reference region, and (2) a technetium-99m subtraction technique, with radioactivity of circulating platelets eliminated by discounting background blood activity. Variation in graft thrombogenicity was provided by seeding six prostheses with enzymatically derived autologous endothelial cells, and implanting four prostheses without seeding. Grafts were imaged at 1, 4, and 6 weeks postimplantation, with platelet labeling using indium-111-oxine and red blood cell labeling using technetium-99m. At 7 weeks grafts were excised and gamma activity was measured in proximal, middle, and distal segments. Luminal generation of TxB2 and 6-keto-PGF1[alpha] from midportions of grafts was assayed. Indium-111 excess ratios at 6 weeks correlated with actual gamma activity of excised grafts (proximal r = 0.80, P r = 0.73, P r = 0.48, ns) but such a correlation did not exist for the technetium-99m subtraction technique (r = -0.05, -0.25, and 0.16, in the three segments, respectively, all ns). The ratio of graft to aortic TxB2 production revealed a positive correlation with graft gamma activity (r = 0.87, P 1[alpha] to TxB2 production also correlated with gamma counts (r = -0.64, P = 0.05). In this experimental setting technetium-99m subtraction analysis was an imprecise method of detecting graft platelet accumulation, whereas indium-111 excess ratios proved to be a more accurate method of quantitating vascular prosthetic thrombogenicity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26220/1/0000300.pd