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Biomedical subjects

B E Keogh

Publications and source records attributed to B E Keogh.

9 recordsLinked to original sources
PubMed1991

Angioscopic evaluation of intravascular morphology after coronary endarterectomy.

Coronary endarterectomy in diffuse coronary disease is attended by an increased incidence of perioperative myocardial infarction and vein graft occlusion, which have been partially attributed to the presence of occlusive or thrombogenic intraluminal flaps in the main vessel or its smaller branches. To define the nature and incidence of these features we studied 15 endarterectomized right coronary arteries in 15 patients (12 men, 3 women; age, 55 +/- 7 years [mean +/- standard deviation]) undergoing a coronary operation for multivessel disease. After endarterectomy and distal graft anastomosis, angioscopy was performed using a 1.8-mm Olympus angioscope during graft perfusion with crystalloid solution. The endarterectomy cores were 66 +/- 30 mm in length with 11 major bifurcations and two trifurcations providing 30 major endpoints. At 22 of 30 major endpoints the distal end of the core was smooth and tapered. There were 17 minor side-branch endpoints. Angioscopy revealed the presence of wispish intraluminal fronds and medial bruising in all (100%) arteries. Twenty-nine of the 30 intraluminal endpoints could be visualized. Major intraluminal flaps were seen at the eight nontapered endpoints and six of the 21 smooth tapered endpoints that were visualized. Fifteen minor side branches could be identified angioscopically: a flap was seen at only one side-branch origin. The average examination time was 3.2 +/- 1.1 minutes (7.7% +/- 2.7% of cross-clamp time), and examination required 200 to 250 mL of perfusate. This technique enables immediate and accurate postinterventional assessment of intravascular morphology with minimal prolongation of ischemic time and has shown that small side branches are not compromised by endarterectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1989

Intravascular delivery of laser energy with metal-capped optical fibers: the potential hazard of distal embolism.

To assess the risk of embolism resulting from plaque fragmentation during laser angioplasty with metal-capped optical fibers, laser energy of 4, 8, and 12 W for 10 or 20 seconds was delivered through these fibers to 60 coronary endarterectomy segments fitted in a silicone tube filled with saline solution. Twenty specimens manipulated in the same way but without delivering laser energy were used as controls. The effluent was filtered through in-line filters of 225, 70, and 25 microns. Treatment with laser energy resulted in weight loss and shortening of the specimens compared to control specimens (23 +/- 4 mg versus 5.4 +/- 0.8 mg; p less than 0.001 and 0.2 +/- 0.02 mm versus 2.5 +/- 0.5 mm; p less than 0.001). However, this also produced significant debris formation for all combinations of power and time (up to 275 +/- 38 micrograms versus 155 +/- 21 micrograms in controls). Results of scanning electron microscopy showed the presence of fragments up to 300 microns in diameter. Another potential hazard of laser angioplasty with metal-capped optical fibers in thromboembolism. This was studied by delivering laser energy through metal-capped fibers during perfusion with aliquots of blood at 5 or 40 ml/min. At each flow rate nine aliquots were treated with either 4, 8, or 12 W for 3, 6, or 9 seconds and a tenth was used as a control aliquot. The effluent was filtered with five filters between 225 microns and 25 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriosclerosis↗
PubMed1989

Microprocessor-controlled hemodynamics: a step towards improved efficiency and safety.

Manual titration of sodium nitroprusside (SNP) is widely used for treatment of hypertension following cardiac surgery. This study compared conventional manual control with control by a research prototype of an automatic infusion module based on a proportional plus integral plus derivative (PID) negative feedback loop. Two groups of coronary artery bypass patients requiring SNP for postoperative hypertension were studied prospectively. In the first group, hypertension was controlled by manual adjustment of the SNP infusion rate, and in the second, the infusion rate was controlled automatically. The actual and desired mean arterial pressures (MAP) over consecutive ten-second epochs were recorded during the period of infusion. The MAP was maintained within 10% of the desired MAP 45.8% of the time in the manual group, compared with 90.0% in the automatic group, and the mean percent error in the automatic group was significantly less than in the manual group (P less than 0.01). It is concluded that adoption of such systems will result in improved patient safety and may facilitate more effective distribution of nursing staff within intensive care units.

Analog-Digital Conversion↗
PubMed1989

Endothelin-1 is a potent long-lasting vasoconstrictor in dog peripheral vasculature in vivo.

Endothelin-1 (ET-1), a 21 amino acid peptide, has recently been identified and shown to produce a potent and prolonged constriction of mammalian blood vessels in vitro. We have studied the effect of local infusion of this peptide on resistance vessels in the hindlimb of the anesthetized greyhound dog. Incremental doses of ET-1 (3-200 pmol/min) were infused into the left femoral artery. Doses above 10 pmol/min produced a slowly progressive reduction in hindlimb blood flow in a dose dependent fashion, maximally reducing flow by 79.5% +/- 3.2 from 152.3 +/- 29.1 ml/min to 27.8 +/- 5.8 ml/min (+/- SEM, p less than 0.015), with a concomitant rise in vascular resistance. In the control vessel (right femoral artery) there were no statistically significant changes in blood flow observed. Onset time of the response to ET-1 was 3 min, whereas spontaneous recovery of the flow occurred at 30 min following cessation of the infusion. We demonstrated transient reversal of constriction in this arterial model during coinfusion with endothelin-1 (100 pmol/min) of dihydropyridine calcium channel blocking agent nicardipine (0.5-20 nmol/min), substance P (0.5-50 fmol/min), adenosine (10-10,000 pmol/min), and isosorbide dinitrate (0.001-0.1 mg/min).

Animals↗