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Biomedical subjects

M Adkins

Publications and source records attributed to M Adkins.

7 recordsLinked to original sources
PubMed1998

Effects of indirect light and propranolol on melatonin levels in normal human subjects.

An indirect lighting protocol was developed to measure nocturnal melatonin suppression by light in normal human subjects. Goals were to minimize both discomfort due to staring intensely at a bright light source, and behavioral variation due to wandering gaze. Subjects sat with a bank of five full-spectrum light sources placed behind them. Lights reflecting off the surfaces before each subject produced a hemisphere of light that measured 500 lx +/- 5%. Subjects retired to bed in darkness by midnight and then sat in the hemisphere of light from 02.00 h to 04.00 h. Blood for melatonin was drawn at 20-30-min intervals from midnight to 06.00 h. Plasma melatonin was measured by radioimmunoassay. The indirect lighting protocol was used to compare the effects of 500 lx light to dark (21 subjects) and to study varying light intensities from 300 to 2000 lx (7 subjects). We studied the effects of the sitting posture in very dim light of 20-30 lx (6 subjects). We also studied the effects of propranolol plus dark and propranolol plus 500 lx light on melatonin levels. Subjects received placebo, 10 mg propranolol or 40 mg propranolol orally at 23.00 h, and were then exposed to either the dark or light condition. Melatonin levels obtained with the indirect lighting protocol were consistent with studies using direct lighting; light of 500 lx significantly suppressed nocturnal melatonin and suppression was dose related between 300 and 2000 lx. Sitting in dim light had no significant effect on melatonin suppression when compared with the supine posture in the dark in six subjects. Propranolol caused a dose-dependent decrease in melatonin levels in both the dark and the light. There was no relationship between suppression of melatonin by propranolol and suppression by light.

Adolescent↗
PubMed1993

Factors that influence radioimmunoassay of human plasma melatonin: a modified column procedure to eliminate interference.

We describe here the effect of various agents and conditions that can influence the assay of plasma melatonin and report a modified column method which minimizes these interferences. Melatonin was measured by a sensitive radioimmunoassay which can detect melatonin from 5 to 500 pg/ml; the assay was linear about 0-60 pg/ml range. The hemolysis of samples increases the apparent level of melatonin in plasma. When the hemolyzed samples were passed through the SEP-cartridge and washed with methanol, the normal basal level was restored. Elution from the column was highest at 100% methanol and proportionate with the "spiked" value of melatonin. The addition of hemoglobin standard and serum albumin decreases the assayed value of melatonin while the addition of red blood cells and heparin increases the level. EDTA, oxalate, and citrate do not influence the basal level of melatonin. Samples that have been affected by these various agents and conditions can be normalized by passing samples through the column. Up to three cycles of freezing and quick thawing of plasma had no effect on the assay of melatonin; however, beyond three cycles levels were reduced. Long-term storage (up to 4 years) has no influence on the assay.

Animals↗
PubMed1991

Percutaneous transluminal subclavian angioplasty in a patient with postoperative angina.

Subclavian artery stenosis is a rare cause of angina in patients who have undergone coronary revascularization using the internal mammary artery. The traditional approach to this problem is surgical revascularization of the subclavian artery with a bypass graft. We report the successful treatment of a patient with this condition using percutaneous transluminal subclavian artery angioplasty, obviating an additional surgical procedure.

Aged↗
PubMed1991

Permanent transfemoral pacemaker insertion after repair of congenital heart disease.

In certain patients with anomalies of systemic venous connection, traditional transvenous pacemaker lead insertion may not be technically feasible. We report the use of the femoral venous approach to insert a permanent pacemaker in a patient with congenital heart disease who had undergone two previous cardiac operations and had persistent anomalies of the superior systemic venous circulation. We recommend that the femoral venous approach be considered in select patients requiring permanent pacing.

Adult↗
PubMed1991

Phrenic nerve injury. A prospective study.

In cardiac surgery, topical iced saline solution slush has become an important adjunct in maintaining myocardial hypothermia during cardioplegic arrest. One complication of this technique is phrenic nerve injury (PNI). In an attempt to reduce the incidence of PNI, a prospective study was undertaken to evaluate the impact of phrenic nerve insulation on PNI during cardiac surgery. Seventy-six consecutive patients who underwent coronary revascularization constituted the control group (CG) and were compared with 76 patients who underwent a similar procedure with the addition of phrenic nerve insulation. In the intervention group (IG), a foam insulation pad was placed between the heart and the pericardium in an effort to reduce exposure of the phrenic nerve to iced saline solution slush. There was no difference in major demographic descriptors or operative variables between the CG and the IG, except that the internal mammary artery was used more frequently in the IG (64 percent vs 36 percent, p = 0.0006). The in-hospital mortality was similar between the groups (CG, 0.0 percent; IG, 1.3 percent; p = 1.0); however, the incidence of roentgenographically diagnosed PNI was much greater in the CG (14/76 patients [18 percent] vs 0/76 patients [0 percent]; p = 0.0006). Patients with and without PNI were similar with regard to age, gender, aortic cross clamp time, cardiopulmonary bypass time, and number of grafts (p greater than 0.05). All unilateral PNI occurred on the left. Three patients with bilateral PNI required tracheostomy and prolonged mechanical ventilation. In-hospital mortality was similar for patients with and without PNI (0 percent vs 0.7 percent), but mean postoperative hospital stay for patients with clinically diagnosed PNI was longer than for those without PNI (32 vs 11 days, p = 0.04). This prospective study demonstrates that the incidence of PNI can be significantly reduced by the routine use of phrenic nerve insulation.

Adult↗
PubMed1991

Novel system for percutaneous cardiopulmonary bypass.

Percutaneous cardiopulmonary bypass (PCPB) has recently come to the forefront of medicine as a technique for resuscitating and supporting patients in various clinical situations. Current systems utilize small-diameter cannulas to aspirate blood under high suction into the cardiopulmonary bypass circuit. Aspiration-based systems have several disadvantages including risk of air embolism, blood hemolysis, and cavitation. Additionally, they are suboptimal for use during open-heart surgical procedures. A system with a venous cannula that employs gravity drainage has been evaluated. Once advanced into position over a guide-wire, the stylet is removed, causing the basket near the end of the cannula to expand. Blood flows into the cannula from side holes and the basket region, which prevents the vessel wall or atrium from collapsing around the catheter and impeding venous drainage. Hemodynamic, hematologic, and histologic examinations were performed on eight anesthetized mongrel dogs during 2 h of PCPB. All animals exhibited adequate tissue perfusion and right and left heart decompression. All animals were successfully weaned from PCPB and after 30 min exhibited normal myocardial function. No ischemic changes were observed in the heart, lung, kidney, or liver by light and electron microscopy. We conclude that full PCPB can be satisfactorily achieved by using a novel percutaneous venous cannula and gravity drainage.

Animals↗