Biomedical subjects
Publications and source records attributed to J A Michaels.
The current status of new techniques for percutaneous arterial recanalization, including laser, thermal and mechanical angioplasty techniques, is described. The reported results, potential advantages and possible future developments are discussed.
Autogenous saphenous vein is generally considered to be the best material for arterial bypass grafts below the inguinal ligament. Recent results have suggested that the advantage of vein over prosthesis is more pronounced in a distal situation, but it is not immediately apparent whether the difference is sufficient to justify a policy of using prosthesis for the initial above-knee graft to preserve the vein in case later surgery is required. An attempt has been made to answer this question. The literature has been reviewed to obtain estimates of the patency rates for grafts in different situations and a mathematical model has been set up using these figures to predict the outcome of different treatment policies. The model can be used to predict the result of alteration or inaccuracy in the data or to make use of the results of newly reported studies. The model predicts that the use of prosthesis for an initial graft will reduce the overall patency and substantially increase the requirement for reoperation, even if the present data give a substantial overestimate of the advantages of vein above the knee.
Since December 1986, 40 laser angioplasty procedures have been performed using the energy from a pulsed NdYAG laser, delivering near infrared light (1064 nm) in 100-microseconds pulses of approximately 300 mJ per pulse, directly through a transparent sapphire tipped device. All patients had total occlusion of the superficial femoral artery and symptoms severe enough to warrant surgery, with ulceration or gangrene in eight, rest pain in 14 and severe claudication interfering with life-style in the others. The device was introduced through an antegrade puncture of the superficial or common femoral artery and laser recanalization was followed by attempted balloon angioplasty in all cases. Occlusions were a median length of 15 cm (range 2-35 cm); ten patients had previously undergone failed attempts at conventional balloon angioplasty and four had occluded femoropopliteal grafts. Thirty-seven legs of 34 patients were treated with an average of 60 J (range 10-235 J) with successful recanalization in 27 and immediate reocclusion in seven. The 20 successful recanalizations have been followed up for up to 24 months (median 7 months) with only one late occlusion at 5 months. Failed recanalization was due to poor transmission by the delivery device in the early part of the series (five cases), repeated passage of the device down a collateral branch (four cases), dissection at the site of previous surgery (two cases) or no apparent reason (two cases). Immediate reocclusion was due to very poor run off in patients with severely ischaemic limbs (three cases) or technical difficulties with balloon dilatation (two cases). Complete symptomatic relief was obtained in all the cases of radiologically successful laser angioplasty. Early surgery was required in one case following reocclusion of the artery when an angioplasty balloon failed to deflate, and one patient suffered a skin reaction thought to be due to inadequate removal of the sterilizing solution. A different sterilizing procedure is now followed. Laser angioplasty can reduce the number of patients requiring bypass surgery and improvements in the device and access methods may reduce the number of untreatable cases.
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Experimental work has shown that a transparent laser device delivering pulsed energy to an artery results in a smaller area of surrounding damage than does an opaque device with a continuous wave laser. The combination of a transparent ball-tipped device with a pulsed Nd-YAG laser has been investigated. The system delivers pulses of 100 microseconds at a rate of 10 Hz and average energy of 0.5 J per pulse with an energy loss of 5-10% between the output at the laser rail and the fibre tip. The dose/response was measured and showed that on normal aorta under saline the device produces craters with a depth of 5 microns/J and 1.5 mm radius. There is a 100% increase in dose response with diseased aorta and a 50% increase when exposure is carried out under blood. The effect of a varying angle of incidence upon the arterial wall has been measured. Angulation of the device at 10 degrees from the perpendicular reduces the crater depth to 50%, as compared with a 50% reduction at 60 degrees using a bare fibre. As estimated with a thermal camera in air, the device heats up to a maximum of 50 degrees C during a 50 J exposure, compared to 110 degrees C after 5 J for the sapphire device. Artificial circulation experiments were carried out using diseased femoral vessels occluded by a ligature. The new system recanalised 100% of occlusion in straight vessels, and 40% of occlusions in curved vessels at a radius of 2.5 cm.(ABSTRACT TRUNCATED AT 250 WORDS)
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The plasma sodium concentration, [Na]P, falls following major surgery and this fall is exacerbated by the administration of sodium-free or sodium-low intravenous fluids in the postoperative period. As a prelude to prospective, but controlled, studies we observed the range of [Na]P on admission for surgery in 477 patients. In 309 patients the extent of the change in [Na]P by the first postoperative day (delta [Na]) was related to the severity of the operation undergone (minor, moderate or major) and the volume of potentially hypo-osmolar intravenous fluid given. The mean admission [Na]P was significantly lower with increasing severity of proposed operation. A highly significant fall occurred in [Na]P following surgery of every grade; such falls in [Na]P were seen even when no potentially hypo-osmolar fluids were administered. A significant inverse relationship between admission [Na]P and delta [Na] was demonstrated. We conclude that [Na]P falls following surgery of any severity and that such falls occur even when exogenous dilution cannot be implicated as a cause.
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Seven premature infants contracted asymptomatic hepatitis A while hospitalized in an intensive care nursery (nursery A) from May through August 1981. Fifteen secondary cases occurred between Aug 13 and Oct 14 and included six family members of nursery A infants, five nursery A nurses, and three nurses and a physician at two other nurseries--B and C. Nurseries B and C had each received an infected infant transferred from nursery A in July. An epidemiologic investigation was conducted to determine the mode of transmission of hepatitis A in infants. A common vehicle was not identified. Review of dates of onset of illness in adults suggested that hepatitis A was transmitted in at least two generations of illness in infants at nursery A. Evaluation of infant handling in nursery A, using a case-control study, suggested that hepatitis A was transmitted among infants by nurses. Asymptomatic infected premature infants can be a source of hepatitis A in nursery infants and personnel and in the community.
A retrospective review of autopsy records was performed to evaluate a clustering of patients shown to have invasive pulmonary aspergillosis during the period July 1, 1978 through October 31, 1980 at Milwaukee County Medical Center, Milwaukee, Wisconsin. During this period, ten patients, all of whom were immunosuppressed by either hematologic malignancy (two), advanced age (one), or iatrogenically to prevent rejection of renal allografts (seven) were found to have invasive pulmonary aspergillosis. Prospective and retrospective evaluations of the hospital environment correlated the clustering of cases to recent road construction, and recovery of Aspergillus fumigatus and A. flavus from window air conditioners used in the renal transplantation ward suggested that some of the patients had acquired the infection nosocomially. A review of autopsy records during a seven-year period following the initiation of the renal transplant program but antedating road construction of any major consequence revealed no invasive aspergillosis among any patient autopsied.
Children visiting parents in the ICU is still controversial. Here are six different opinions about children visiting from ICU nurses, an infection control practitioner, and even a parent. All view points are important to consider in providing access of children to their critically ill parents. Interestingly, even nurses who do not generally support child visitation have allowed children's visits in special circumstances and found the experience positive.