David Zelt

Selective management of abdominal aortic aneurysms in a prospective measurement program

PURPOSEnThe purpose of this study was to clarify the treatment of patients with small abdominal aortic aneurysms (AAAs) less than 5 cm in diameter and those believed to be unfit for operation with AAAs 5 cm diameter or greater.nnnMETHODSnFour hundred ninety two patients with AAAs less than 5 cm when first seen were entered in a prospective measurement program by ultrasonography or computed tomography scan (exclusively after 1998) every 6 months. A decision regarding operative fitness was made when the AAA was 5 cm. Patients then underwent operation if fit or continued follow-up if their AAA was larger than 5 cm but they were unfit. A further group of 91 patients with aneurysms 5 cm or greater when first seen but unfit for repair were entered in the prospective measurement program.nnnRESULTSnIn the group with AAAs less then 5 cm at entry, operation was performed in 201 patients as a result of increase in AAA size to 5 cm or greater (157), AAA expansion of more than 0.5 cm in 6 months (24), or for other reasons (20). Of those with AAAs smaller than 5 cm at entry, 291 have not undergone operation at a mean follow-up of 42 months. Expansion was significantly related to aneurysm size at entry and was highest in the 4.5 to 4.9 cm group at 0.7 cm/year. In the group of patients deemed unfit for operation with 5 cm AAAs [as a graduate of the less than 5 cm group at entry (85 patients) or first seen with AAA greater than 5 cm (91 patients)], 10 ruptures have occurred. Of these patients with ruptured AAAs, six had AAAs between 5.0 and 5.6 cm.nnnCONCLUSIONSnBecause of the risk of rupture demonstrated in our series in AAAs 5 cm or slightly greater and the progressive increase in expansion to a mean of 0.7 cm/year in those AAAs between 4.5 and 4.9 cm at entry, recommendation for elective operation in patients with AAAs between 4.5 and 4.9 cm at entry, recommendation for elective operation in patients with AAAs between 4.5 and 5.0 cm should be strongly considered in a fit patient.

The impact of selective use of dipyridamole-thallium scans and surgical factors on the current morbidity of aortic surgery.

Preoperative cardiac testing in patients undergoing vascular surgery remains controversial. We have advocated selective use of dipyridamole-thallium scans based on clinical markers of coronary artery disease before aortic surgery. The present study assessed both the efficacy of this policy and the role of surgical factors in the current morbidity of aortic reconstruction. Two hundred two elective aortic reconstructions (151 abdominal aortic aneurysms, 51 aortoiliac occlusive disease) performed in the period from January 1989 to June 1990 were reviewed. Preoperative dipyridamole-thallium scanning was performed in 29% of all patients, prompting coronary angiograms in 11% and coronary artery bypass grafting/percutaneous transluminal coronary angioplasty in 9% of patients before aortic reconstruction. The overall operative mortality rate was 2%, with one cardiac-related death. Major cardiac (nonfatal myocardial infarction, unstable angina) and pulmonary complications occurred in an additional 4% and 6%, respectively, of patients. Coronary artery disease clinical markers and surgical factors were analyzed with stepwise logistic regression for the prediction of operative mortality rates and major cardiopulmonary complications. Variables retaining significance in predicting postoperative death or cardiopulmonary complications included prolonged (more than 5-hour) operative time (p less than 0.004), operation for aortoiliac occlusive disease (p less than 0.010), and a history of ventricular ectopy (p less than 0.002). Prolonged operative time (p less than 0.006) and the detection of intraoperative myocardial ischemia (p less than 0.030) were predictive of major cardiac complications after univariate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective management of abdominal aortic aneurysms smaller than 5.0 cm in a prospective sizing program with gender-specific analysis.

PURPOSEnWe present extended follow-up findings of the Kingston prospective sizing program for patients with abdominal aortic aneurysm (AAA) smaller than 5.0 cm in diameter, with gender-specific analysis.nnnMETHODSnFrom 1976 to 2001, 895 patients (688 men, 207 women) with AAA smaller than 5.0 cm were entered, regardless of fitness, in a prospective sizing program in which computed tomography scans were obtained every 6 months. Operations were performed in fit patients with an increase in AAA size to 5 cm (n = 190), AAA expansion greater than 0.5 cm in 6 months (n = 27), or for other reasons (n = 33). Follow-up continued until AAA rupture, surgery, death, or removal from the program.nnnRESULTSnNo AAA smaller than 5.0 cm ruptured during prospective follow-up. There was a statistically significant increase in expansion rate relative to size at entry, with the highest mean expansion rate of 0.52 cm/y for AAA 4.5 to 4.9 cm in diameter. There was no significant difference in AAA expansion rate between men and women. The frequency of surgery was inversely related to age at entry, but was positively related to AAA size at entry, with patients with AAA 4.5 to 4.9 cm at entry 6.8 times more likely (95% confidence interval, 4.3-10.7) to undergo surgery than those with AAA 3.0 to 3.4 cm at entry. Women were older than men at entry, and age at entry in those undergoing surgery was significantly greater in women.nnnCONCLUSIONSnThe study confirms the results of the United Kingdom Small Aneurysm Trial and the Aneurysm Detection and Management Study, that is, that risk for rupture is extremely unlikely with AAA smaller than 5.0 cm, which enables safe follow-up surveillance programs in both men and women with AAA smaller than 5.0 cm.

Second derivative-high-performance liquid chromatographic-fluorometric detection of porphyrins in chick embryo liver cell culture medium

A high-performance liquid chromatographic system is described which is suitable for the separation and quantitative determination of a mixture of porphyrin esters in nanogram quantities from the culture medium used for maintenance of a monolayer culture of chick embryo liver cells. The desired sensitivity was obtained by coupling a high-performance liquid chromatograph with a second derivative-fluorometric detection system. The most effective method for preparation of the porphyrin methyl esters prior to chromatography was found to be lyophilization of the culture medium prior to esterification with 5% sulphuric acid in methanol.

Patterns of porphyrin accumulation in response to xenobiotics. Parallels between results in chick embryo and rodents.

Our objective was to determine whether patterns of porphyrin accumulation produced by chemicals in chick embryo hepatocyte culture would indicate which enzyme of heme biosynthesis was inhibited. The ferrochelatase-inhibitory potency and porphyrin patterns produced by DDC, TTMS, and their analogues were studied. The protoporphyrin:coproporphyrin ratio observed was found to correlate with ferrochelatase-inhibitory activity. The results obtained in chick embryo with TTMS and DDC parallel those found in rodents. Griseofulvin has been shown to lower ferrochelatase activity and to cause the accumulation of protoporphyrin in rodent liver. In chick embryo liver cell culture, however, coproporphyrin, uroporphyrin, and heptacarboxylic acid porphyrin accumulate and ferrochelatase activity is not lowered. Uroporphyrin, heptacarboxylic acid porphyrin, and coproporphyrin are the major porphyrins to accumulate in response to PAHs (for example, 3,3,4,4-TCBP in chick embryo liver cell culture). This may be explained by inhibition of UROD, which has been observed in chick embryo and rodent liver. Some chemicals, such as phenobarbital and nifedipine, cause the accumulation of these porphyrins in chick embryo liver cell culture, and this is explained by inhibition of UROD. These chemicals have not been reported to interfere with heme biosynthesis in the intact chick embryo or rodents; possibly protective mechanisms that are not available in the cell culture system are operative in the intact animal. It was concluded that porphyrin patterns may serve as a guide to which enzyme of heme biosynthesis is inhibited in chick embryo liver cell culture. The results obtained in the culture system with certain chemicals, such as DDC and TTMS analogues and PAHs, correspond with results in rodents. In other cases, such as with griseofulvin, the results do not correspond.

Arterial laser welding with a 1.9 micrometer Raman-shifted laser * **

A new 1.9 micron Raman-shifted neodymium:yttrium aluminum garnet (Nd:YAG) laser was used for small vessel welding. Bursting pressures and stresses of sutured and laser-welded arteriotomies created in the rat femoral artery and aorta were measured. Sutured arteriotomies had a significantly higher burst stress than laser-welded arteriotomies. Although there were no significant differences in burst stress at the various laser powers tested, an optimal power was identified. The laser was also used to weld transected rat aortas. The average power delivered was 200 mW for 30 seconds per anastomosis. The average time for completing an anastomosis was 6 minutes compared with 18 minutes when sutures were used. In relation to proximal aortic diameter, there was a 7.9% decrease at the anastomosis immediately (n = 4), and a 6.6% and 4.9% increase occurred at 24 hours (n = 4) and 10 weeks (n = 5), respectively. Acute anastomotic compliance, and compliance at 24 hours and 10 weeks were decreased by 47.2%, 39.5%, and 47.8%, respectively, and were similar to sutured anastomoses. Histology showed little thermal denaturation of the aorta within 0.6 mm of the anastomosis, approximately 1 mm of medial cell death, and nearly normal elastic fiber alignment. One focal false aneurysm was noted at 10 weeks. Although the sutured and laser-welded anastomoses share similar compliance changes, the laser-welded anastomoses are more isodiametric. This preliminary experience with the 1.9 micron laser shows the distinct advantages of a handheld fiber, no requirement for cooling irrigation, speed, and no difference in compliance from sutured anastomoses.

Modeling and Analysis of Multistate Access to Elective Surgery

In this paper, we attempt to determine whether delays in scheduling operation affect waiting time in a queue for elective surgery. We analyze the waiting-list management system in a Canadian hospital. We estimate the impact of scheduling delays by modeling access to treatment as a multistate process. We found that patients with any delay in scheduling surgery had longer waiting times than patients without delays. For certain sources of delays, the admission rate was 50–60% lower compared with the rate for admissions without a delay independent of urgency of surgical intervention. Our findings support a concern that waiting time for elective surgery is not simply determined by how many patients are on the waiting list, or by how urgently they need treatment, but also by the waiting list management practice.

Potential for bias in waiting time studies: events between enrolment and admission.

STUDY OBJECTIVE To demonstrate the effect of exclusion of data on delays in scheduling operations in calculating difference in admission rates between two enrolment periods. DESIGN A prospective cohort study; outcome measure—waiting time for elective admission; study variables—enrolment periods, before 31 March 1997 and after that date; the time of scheduling delay; gender; age; urgency, and type of surgery. SETTING An acute care hospital in Ontario, Canada. PARTICIPANTS 1173 consecutive cases accepted for elective vascular surgery between 1 July 1994 and 31 March 1999. MAIN RESULTS Before adjustment for scheduling delays, a 20% lower admission rate was associated with period 2, rate ratio (RR) = 0.8 (95% confidence intervals (CI)= 0.7, 0.9). The difference between the periods became only marginally significant after the adjustment, RR = 0.9 (95% CI=0.8, 1.0). No difference between the periods was found when admission rates were compared before a delay occurred, RR = 0.9 (95% CI=0.8, 1.1). In delayed patients, those enrolled in period 1 and 2 had, respectively, a 40% and a 60% lower admission rate than the period 1 patients admitted without scheduling delays, RR = 0.6 (95% CI=0.4, 0.8) for period 1 and RR = 0.4 (95%CI=0.3, 0.5) for period 2. CONCLUSIONS The results provide evidence that patients experiencing a delay in scheduling operation have a lower admission rate after the event. Thus, potential for bias exists when between group comparison of waiting time is done without adjustment for an intermediate event that may occur before elective admission.

Management of Major Vascular Injuries: Neck, Extremities, and Other Things that Bleed

Vascular injuries represent a significant burden of mortality and disability. Blunt injuries to the neck vessels can present with signs of stroke either immediately or in a delayed fashion. Most injuries are detected with computed tomography angiography and managed with either antiplatelet medications or anticoagulation. In contrast, patients with penetrating injuries to the neck vessels require airway management, hemorrhage control, and damage control resuscitation before surgical repair. The keys to diagnosis and management of peripheral vascular injury include early recognition of the injury; hemorrhage control with direct pressure, packing, or tourniquets; and urgent surgical consultation.

Vascular anastomosis using a 1.9-μm laser

A 1.9 micrometers laser is used to weld small diameter vessels. The absorption characteristic of tissues at this wavelength renders this laser suitable for welding of vessels with diameters in the 1 to 3 mm range. The appropriate laser power range for welding is 120 to 200 mW with a fluence on target of approximately 100 J/cm2. For vessel wall thicknesses matching the optical absorption depth, measured burst pressure was approximately 400 mmHg. In this case the acute weld strength is greater than 3 X 106 dynes/cm2. Anastomotic compliance of the welded zone was a factor of two lower than native vessel tissue both immediately following welding and after 10 weeks of healing. The advantages offered by this laser wavelength are convenient energy delivery via fiber optics, no irrigation needed for tissue cooling, and applicability to small vessel anastomoses.