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Biomedical subjects

O D Saether

Publications and source records attributed to O D Saether.

33 records · Page 2Linked to original sources
PubMed1995

Alterations in intracranial volume following cross-clamping of the descending thoracic aorta in pigs--an experimental study using MRI.

OBJECTIVES: To determine whether alterations in intracranial volume occurred following cross-clamping of the descending thoracic aorta in pigs. DESIGN AND SETTING: Laboratory animal study. MATERIALS: Eight pigs undergoing cross-clamping of the descending thoracic aorta for 30 min. CHIEF OUTCOME MEASURES: A Philips Gyroscan T5-II Release 3 (0.5 T) was used to obtain intracranial images before cross-clamping, during cross-clamping and after declamping. The ventricular volume was measured on Spin Echo T1-weighted images. The signal intensity of the cerebral tissue was measured on Spin Echo T2-weighted images. Increased signal intensity of the cerebral tissue relative to an external reference was used as an indicator of cerebral oedema. MAIN RESULTS: The ventricular volume decreased to 89% (p < 0.01) of the baseline value after 5 min of cross-clamping. At 5 min after declamping the ventricular volume decreased further to 71% (p < 0.01). At 25 min after declamping the ventricular volume had returned to the baseline value. The signal intensity of the cerebral tissue did not differ from baseline values following aortic cross-clamping. CONCLUSIONS: In this study, ventricular volume decreased following cross-clamping of the descending thoracic aorta. Since no cerebral oedema was observed, the decrease of ventricular volume was most likely due to increased intracranial blood volume.

Animals↗
PubMed1995

Haemodynamic effects of thoracic epidural anaesthesia during proximal aortic cross-clamping in pigs.

Cross-clamping (XC) of the thoracic aorta induces a hyperdynamic circulation proximal to the aortic clamp. In this investigation, the effects of thoracic epidural anaesthesia (TEA) on the haemodynamic response to XC were studied in pigs. Seventeen pigs were anaesthetized with ketamine, and the thoracic aorta was cross-clamped for 30 minutes. In eight of the animals (TEA-group) a thoracic epidural block (3 ml 0.5% bupivacaine) was added to the general anaesthesia. Prior to XC there was a lower heart rate (HR), cardiac output (CO) and mixed venous oxygen saturation (SvO2) in the TEA-group compared to the nine animals with general anasthesia only (control-group). During XC there was an increase in HR, CO, SvO2 and proximal aortic blood pressure (PPROX) in both groups, without differences between groups. Following aortic declamping central venous pressure (CVP), pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCWP) increased in both groups. Fifteen minutes after declamping, one animal in each group died. It was concluded that in this experimental model, TEA combined with general anaesthesia did not modify the haemodynamic response to XC of the thoracic aorta.

Anesthesia, Epidural↗
PubMed1995

Effect of sodium nitroprusside on cardiac output during cross-clamping of the descending thoracic aorta in pigs.

Sodium nitroprusside (SNP) is used to control proximal hypertension during cross-clamping of the descending thoracic aorta (XC). To assess the haemodynamic effects of SNP on cardiac output (CO) during XC, 21 pigs were anaesthetized with ketamine and fentanyl. In the control group (n = 11), no vasodilating therapy was given. In the investigation group (SNP group), 2 animals died during the surgical preparation and were excluded, leaving 8 animals in the group (n = 8). In these animals, SNP was infused in order to keep the mean arterial pressure (MAP) at about 100 mm Hg during cross-clamping. In both groups, aorta was cross-clamped for 30 min, and cardiac output (CO) was measured by the thermodilution technique. Following cross-clamping, CO increased 107% in the control group and 96% in the SNP group. There was an increase in heart rate (HR) of 77% in the control group and of 110% in the SNP group, and a reduction in systemic vascular resistance of 41% in the SNP group. Stroke volume (SV) was unchanged in both groups. MAP increased 83% in the control-group. No differences were observed between the two groups regarding central venous pressure or pulmonary artery pressure. Four animals in the SNP group died 5-10 min after release of the aortic clamp. In conclusion, we found equal increase in CO in both groups. The increase in CO was related predominantly to increased HR, whereas SV was largely unaltered. Vasodilation with SNP increased the mortality following clamp removal in this experimental model.

Animals↗
PubMed1994

Cerebrospinal fluid production during proximal aortic cross-clamping.

During cross-clamping (XC) of the thoracic aorta, the cerebrospinal fluid pressure (CSFP) increases. The mechanism of the increased CSFP is unknown but increased cerebrospinal fluid (CSF) production has been suggested as one explanation. The aim of this study was to investigate whether the CSF production rate was influenced by proximal XC of the thoracic aorta in an experimental model. Using the ventriculocisternal perfusion method including [14C] inulin, the rate of CSF production was measured before, during and after XC of the thoracic aorta in seven pigs. The CSFP was measured via a catheter in the lateral ventricle and the thoracic aorta was cross-clamped just distal to the left subclavian artery for 30 minutes. Following cross-clamping the CSFP increased from 5 mmHg to 11 mmHg (p < 0.001) and remained elevated during XC. In contrast the CSF production rate was 0.09 ml/min prior to XC and was not significantly altered following XC. In conclusion this experimental study indicates that increased CSF production is not responsible for the increase in CSFP during XC.

Animals↗
PubMed1992

The use of MRI in the investigation of leg oedema.

Magnetic resonance imaging (MRI) was used in the diagnosis of various conditions giving rise to leg oedema, with special attention to the oedema after femoro-distal vascular reconstruction for obliterative atherosclerosis (n = 14). Patients with deep venous thrombosis (n = 6), chronic lymphoedema (n = 6) and closed muscular compartment syndrome (n = 2) were also investigated. Leg volume increase was measured according to the formula of a truncated cone. Interstitial fluid hydrostatic pressure (Pif) was recorded with the wick-in-needle technique. Spin echo series with 10 mm transverse slices were obtained with MRI. Following vascular reconstructions, leg volume increased 26% on the operated side. In the operated leg, no gradient in Pif was found between the posterior muscular compartment and the subcutaneous tissue. However, there was a significantly higher Pif in the subcutaneous tissue compared to the anterior muscular compartment (p less than 0.05). In the operated group, MRI revealed oedema around the entire circumference of the leg, mainly restricted to the subcutaneous tissue. In contrast, oedema of the leg muscles, particularly in the posterior compartments, was typical for patients having deep venous thrombosis. The group with chronic lymphoedema showed circumferential subcutaneous oedema alone or in combination with a fibrotic honeycomb pattern. Oedema of the affected muscular compartment was easily observed in patients who had a closed compartment syndrome. In conclusion, the use of MRI is promising in the investigation of conditions giving rise to leg oedema. It is likely that the formation of post-reconstructive oedema is taking place in the subcutaneous tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Cerebral haemodynamics during proximal aortic cross-clamping.

This study was carried out to examine cerebral blood flow, including the microcirculation and intracranial pressure during cross-clamping (XC) of the thoracic aorta in pigs. Blood flow in the internal carotid artery was measured by electromagnetic flowmetry. Cerebral microcirculation was studied by the laser Doppler technique, and intracranial pressure measured by applying a fibre optic pressure monitoring catheter in the same craniotomy. Maximal and mean blood flow velocity of the middle cerebral artery was recorded using a transcranial Doppler and cardiac output measured by thermodilution. The thoracic aorta was cross-clamped distal to the left subclavian artery for 30 min. During aortic XC the internal carotid artery blood flow increased 191% (p less than 0.05). Simultaneously mean and maximal blood flow velocity of the middle cerebral artery both increased 125% (p less than 0.01). Intracranial pressure increased 163% (p less than 0.05), and there was an increase in cerebral flux of 23% (p less than 0.05). Within the first minutes following the release of XC, all values decreased to preocclusive values. In conclusion, we observed a significant increase in cerebral blood flow during XC of the thoracic aorta. This is in accordance with the finding of a simultaneous increase in cardiac output. These haemodynamic changes support the theory that an increased blood flow via the proximal feeding system to the anterior spinal artery might be important in avoiding neurological sequelae following proximal aortic XC.

Animals↗
PubMed1990

Winner of the ESVS prize 1989. Microcirculation of the spinal cord during proximal aortic cross-clamping.

The relationship between the cerebrospinal fluid pressure (CSFP) and the microcirculation of the spinal cord was studied during cross-clamping (XC) of the thoracic aorta in pigs. CSFP was recorded via an intrathecal catheter. The microcirculation was measured by the laser Doppler technique using a needle probe inserted percutaneously into the spinal cord. A left thoracotomy was performed, and the thoracic aorta was cross-clamped for 30 minutes distal to the left subclavian artery. Prior to XC a pulsatile flux recording from the spinal cord (SCF) was observed. Following cross-clamping of the aorta SCF was dramatically reduced (P less than 0.001), then stabilised at 40% of base-line values. During XC, variations in CSFP were observed but these changes were not statistically significant. CSFP gradually increased to pre cross-clamp levels following release of XC (P less than 0.05). SCF increased 51% following removal of 1 ml of cerebrospinal fluid (P less than 0.05). By injection of 0.9% saline at body temperature SCF was totally inhibited at CSFP above 15 mmHg. Occlusion of the azygos vein increased CSFP 1.3 mmHg (P less than 0.05) whereby SCF decreased 58% (P less than 0.01). Following release of XC of a hyperaemic period of the SCF was demonstrated in ten out of 13 animals. In conclusion, SCF was significantly influenced by changes in CSFP during XC of the thoracic aorta. The findings support the theory that removal of spinal fluid during XC of the thoracic aorta may increase the perfusion pressure to the spinal cord, thereby improving its blood supply.

Animals↗
PubMed1989

[Vascular surgery in Norway in 1986].

A questionnaire on vascular surgical activity in 1986 was sent to all Norwegian surgical departments (80). 78 units responded. Vascular surgery is not performed in the two hospitals who did not respond. Altogether 3,509 vascular operations were performed in 1986 (844 operations per million inhabitants). By comparison, 2,529 operations were performed in 1981, 2,039 in 1978 and 1,100 in 1975. The largest increase was recorded in operations for abdominal aortic aneurysm, carotid artery stenosis, arterial emboli and angio-access surgery. Elective vascular operations were performed in 41 departments, whereas an additional 16 did emergency vascular surgery only. 34% of the operations were performed by members of the junior staff. Differences between the five health regions have decreased since the investigation in 1981. The highest activity was observed in Health Region V, where 986 operations were performed per million inhabitants. Vascular surgical activity is increasing in Norway. This must be taken into account when estimating the number of residencies and staff positions for vascular surgery. The increasing need for vascular surgery should also influence priorities in our national health system.

Humans↗
PubMed1987

Problems related to previous thrombendarterectomy of the aorto-ilio-femoral arterial segment.

Early postoperative problems following aorto-ilio-femoral thrombendarterectomy include occlusion, bleeding and emboli. Technical details important for the prevention of these complications are discussed. Late problems include reobstruction, sexual dysfunction and aneurysm formation, the last complication being unusual following thrombendarterectomy. Late reobstruction is usually caused by progression of atherosclerosis and technical failures. Bypass grafting using synthetic material is usually the preferred method in redo aorto-ilio-femoral reconstruction since extensive dissection of the arteries is then avoided. We prefer a regular laparotomy for these operations. It might be an advantage to introduce ureteral stents making it easier to identify the ureter which may be surrounded by scar tissue following previous dissection. The creation of sufficient run-off is important. In several cases the procedure must therefore be supplemented with a profunda artery reconstruction. In case of localized and moderate obstruction PTA may be indicated for the relief of recurrent arterial obstruction following thrombendarterectomy.

Aorta, Abdominal↗
PubMedDate not supplied

Ultrasound screening for hip dysplasia in newborns.

We evaluated risk factors for neonatal hip instability (NHI) at birth using ultrasonography and assessed the reliability of our ultrasound method by means of an interobserver study. The hips of 4,459 newborns were examined by ultrasound from 1988 to 1990. The ultrasound evaluation was based mainly on measurement of femoral head coverage (FHC) by the bony acetabular roof. The mean FHC was 56% in boys and 54% in girls (a significant difference). Fifty-five newborns with unstable hips had a mean FHC of 37%, which was significantly lower than that of the normal hips. Known risk factors for NHI were confirmed (breech position, family history of hip dysplasia, increased birth weight), but no new risk factors were detected. The interobserver study included 200 hips. The 95% confidence limit for interobserver variation in FHC (+/- 2 SD) was +/- 8%. Because of this moderate interobserver variation, and because the incidence of late-detected hip dysplasia was low (0.2 per 1,000), we conclude that our method for ultrasound examination is sufficiently reliable for screening of hips in newborns.

Female↗
PubMedDate not supplied

Changes in hemodynamics and acid-base balance during cross-clamping of the descending thoracic aorta. A study in patients operated on for thoracic and thoracoabdominal aortic aneurysm.

AIM OF THE STUDY: In the clinical situation there is discrepancy between various investigations regarding the cardiac response of thoracic aortic cross-clamping. The aim was therefore to investigate the hemodynamic response and blood gases during proximal aortic cross-clamping (XC) in patients operated for descending thoracic and thoracoabdominal aortic aneurysm without circulatory support. PATIENTS AND METHODS: Altogether 51 patients operated on for thoracoabdominal (n=31) or descending thoracic aortic aneurysm (n=20) were included in the investigation. All patients were operated with aortic XC, but no circulatory support was applied. Hemodynamic variables and blood gases were recorded before and during XC. RESULTS: A significant increase in cardiac output during XC from 4.7 to 6.0 liters/min was observed (p<0.01). There was a similar percentual increase in heart rate and also the proximal systolic blood pressure increased. A metabolic acidosis occurred during XC. CONCLUSION: Cardiac output was significantly increased during XC in patients operated on for thoracoabdominal or descending thoracic aneurysm using direct aortic XC without circulatory support. Simultaneously, the heart rate was increased and there was a hyperdynamic circulatory state proximal to the aortic clamp. Redistribution of the blood volume in addition to catecholamine release may be responsible for the observed changes. These observations may influence the selection of operative strategy for some of these patients.

Acid-Base Equilibrium↗
PubMedDate not supplied

Intra-arterial ultrasound: a potential tool for the vascular surgeon. Clinical review.

Intra-arterial ultrasound is a new real-time imaging technique using a miniaturized transducer in a catheter to image diseased arteries. The small size and close proximity to the structures being imaged allow the use of frequencies from 20-40 MHz, resulting in high resolution images. In addition to the stenotic lumen, it is possible to examine the composition and eccentricity of the plaque, as well as structures outside of the vessel. Such information can be used for planning and evaluating vascular interventions. The addition of Doppler measurements allows the evaluation of function as well as anatomy. Research applications include studies of lesion progression, measurement of arterial elasticity, quantitative blood flow velocities and study of intra-arterial flow patterns. Although this technique is in its infancy, it is highly probable that it will prove to be a useful aid to the vascular surgeon.

Arteries↗