Effect of central venous pressure on spinal cord oxygenation.

To analyze the effect of central venous pressure on cerebrospinal fluid oxygen tension and intrathecal pressure, multiparameter sensors were introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid Po(2), Pco(2), and intrathecal pressure in 15 pigs. After 20 min of aortic clamping, hypervolemia was established for 20 min, followed by normovolemia. The animals were divided into 3 groups: in group 1, cerebrospinal fluid Po(2) = 0% at some time during crossclamping; in group 2, cerebrospinal fluid Po(2) was <50%; and in group 3, cerebrospinal fluid Po(2) remained > or = 50%. Mean decreases in cerebrospinal fluid Po(2) during the initial 20 min of crossclamping were 82%, 57%, and 15% in groups 1, 2, and 3, respectively. Following induction of hypervolemia, central venous and cerebrospinal fluid pressures increased simultaneously; this caused a significant decrease in cerebrospinal fluid Po(2) in group 2 only. In this model, aortic clamping did not increase cerebrospinal fluid pressure if central venous pressure was not elevated. The detrimental effect of elevated intrathecal pressure on cerebrospinal fluid oxygenation was seen only in animals with an intermediate degree of spinal cord ischemia. This might have important implications for the prevention of paraplegia during thoracoabdominal aortic replacement.

Alterations in cerebrospinal fluid PO(2), PCO(2), and pH measurements during and after experimental thoracic aortic cross-clamping.

In a model of aortic cross-clamping, we studied the use of a multiparameter sensor for measurement of cerebrospinal fluid (CSF) PO(2), PCO(2), and pH during and after aortic cross-clamping. The present study addressed the above-mentioned alterations and their relation according to time intervals. In 31 pigs, a sensor was introduced into the intrathecal space and epidural laser Doppler was used to measure spinal cord blood flow (SCF). By placing the aortic clamp at different levels, three different spinal cord ischemia groups were obtained (mild, moderate, and severe). CSF variables with SCF were studied for 25%, 50%, and 100% changes according to baseline level. In the clamping period, SCF decreased 71.5%, 40.0%, and 33.3% in groups 1, 2, and 3, respectively. CSF O(2) tension reached 0 in group 1, decreased 74.8% in group 2, and was 12.7% in group 3. CSF CO(2) tension increased 247.2% and 202.0% in groups 1 and 2, respectively, but slightly increased in group 3. The maximum reaction time of CSF O(2) tension was about 16.7-26.9min, although this range was 34.5-49.8min in CSF CO(2) tension. We recognized that O(2) tension reacts faster than PCO(2) and pH. It is possible for O(2) tension to be used faster than produced CO(2) in the ischemic medium, although it is known that the diffusion rate of CO(2) is much higher. Spinal cord O(2) tension monitoring is an important method to detect ischemic changes.

Repeat surgery without preoperative angiography in limbs with patent infrainguinal bypass grafts.

The aim of this study was to assess the feasibility and results of repeat surgery without preoperative angiography in limbs with patent infrainguinal bypass grafts. Between January 1995 and December 1999, 73 surgical interventions were performed for correction of inflow, graft, or runoff-related lesions in limbs with patent infrainguinal bypass grafts. Fifty-six of the 73 cases were operated on based on the findings obtained from duplex scanning alone. There were 53 vein and 3 prosthetic grafts in the series. The indications for intervention without angiography were stenotic or occlusive lesions in 35, graft aneurysm in 7, and arteriovenous fistulae in 14. There were no deviations from the preoperatively planned surgical strategy in patients undergoing surgery without preoperative angiography. Cumulative life table primary, (stenosis free) and primary-assisted patency rates, at 12 months following graft revisions (excluding arteriovenous fistulae ligatures) without preoperative angiography, were 64% and 85%, respectively. The corresponding figures for revisions performed with preoperative angiography were 58% and 84%, respectively. There were no significant differences between patients undergoing surgery with or without preoperative diagnostic angiography with regard to patency rates. Surgical interventions for correction of infrainguinal graft-related stenotic or aneurysmal lesions can be safely performed based on findings obtained from duplex scanning.

The impact of different spectral Doppler criteria on the proportion of high-grade internal carotid artery stenosis in patients undergoing duplex scanning.

AIM: To investigate the impact of different spectral Doppler criteria on the proportion of high-grade ICA stenosis in patients undergoing carotid artery duplex scanning. MATERIAL AND METHODS: Duplex scans of 4,548 internal carotid arteries (ICA) in 2,349 patients were retrospectively analyzed. The following different criteria were applied for each scan for definition of ICA stenosis > or = 70%: Criteria I=ICA peak systolic velocity (PSV) > 130 cm/sec and ICA end-diastolic (EDV) > 100 cm/sec, Criteria II=PSV ICA/common carotid artery (CCA) ratio > 4, Criteria III=ICA PSV > or = 230 cm/sec, Criteria IV=ICA PSV > 230 cm/sec and/or ICA EDV > or = 100 cm/sec and/or PSV ICA/CCA ratio > or = 3.2. RESULTS: The frequency of detecting a > or = 70% ICA stenosis with criteria I, II, III, and IV were 5.5%, 6.8%, 8.4%, and 9.6%, respectively (p < 0.05). CONCLUSION: The use of various duplex criteria significantly affected the number of scans receiving a diagnosis of ICA stenosis of > or = 70%.

Surgical reconstruction without preoperative angiography in patients with aortoiliac occlusive disease.

The objective of this study was to evaluate the feasibility of performing surgical reconstructions in patients with aortoiliac occlusive disease with findings obtained solely from duplex scanning. Between January 1995 through December 1999, among 112 patients who underwent surgical intervention due to aortoiliac occlusive disease, 44 were operated on with findings obtained solely from preoperative duplex scanning. Deviations from preoperatively planned surgical interventions according to duplex scan findings and the outcome were analyzed. Our results showed that surgical reconstructions for treatment of aortoiliac occlusive disease can be safely performed by using duplex scanning as the sole preoperative diagnostic modality in patients with conclusive duplex scan findings.

Incidence of deep venous thrombosis in patients undergoing obesity surgery.

The aim of this study was to investigate prospectively the incidence of deep venous thrombosis (DVT) after surgery for morbid obesity. The series comprised 116 consecutive patients undergoing Roux-en-Y gastric bypass. The median age and body mass index were 35 years (range 19-59 years) and 42 kg/m2 (range 32-68 kg/m2), respectively. The patients were examined with duplex ultrasonography pre- and postoperatively. No patient had any symptoms or signs of DVT postoperatively, and ultrasonography showed no signs of thrombosis in iliac, femoral, and popliteal veins in any of the patients. Two patients (1.7%) had a thrombus in the peroneal vein of one leg. Repeated ultrasonographic investigation after 1 week showed complete resolution of both. One patient with a previously unknown activated protein C resistance had an angiographically confirmed minor pulmonary embolus. The incidence of venous thromboembolism after obesity surgery seems to be low, and obesity as a risk factor for thromboembolic disease might have been overestimated in the past.

Carotid artery endarterectomy solely based on duplex scan findings.

The purpose of this study was to review experience with carotid artery surgery based on findings obtained solely from duplex scanning with special regard to unexpected findings during surgery and the early outcome. From January 1993 through December 1999, 271 consecutive patients underwent 287 carotid endarterectomies (CEAs), 229 (80%) of which were performed solely based on duplex scan findings. During the study period 5,932 carotid artery duplex scans were performed in 4,466 patients. Of 589 patients with internal carotid artery (ICA) stenosis 70%, 246 underwent CEA compared to 25 of 156 with 50-69% ICA stenosis. The indications for CEA were transient ischemic attack (TIA) in 88 (30.7%), amaurosis fugax in 60 (20.9%), previous stroke in 91 (31.7%) and asymptomatic disease in 48 (16.7%) cases. There were no statistically significant differences between the groups operated on with and without preoperative angiography with respect to the indications for surgery, associated risk factors, or the degree of stenosis on the contralateral side. In patients undergoing surgery without angiography, there were no unexpected findings that influenced the performance of surgery, in all except 1. There were no significant differences in perioperative morbidity and mortality in patients undergoing surgery with and without conventional angiography. The combined mortality and major stroke rates were 3.4% and 2.2%, respectively. It is concluded that CEA can safely be performed without preoperative angiography in cases with conclusive duplex scan findings.