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Bergen i fokus
- 2002
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Christiansson, Lennart, et al.
(författare)
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A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs
- 2000
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Ingår i: Surgery. - : Elsevier BV. - 0039-6060 .- 1532-7361. ; 127:5, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Impaired spinal cord circulation during thoracic aortic clamping may result in paraplegia. Reliable and fast responding methods for intraoperative monitoring are needed to facilitate the evaluation of protective measures and efficiency of revascularization.METHODS: In 11 pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during thoracic aortic cross-clamping (AXC) distal to the left subclavian artery. A laser-Doppler probe was inserted into the epidural space for simultaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and 60 minutes after declamping. The same measuring points were used for systemic hemodynamic and metabolic data acquisition.RESULTS: The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decreased within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both methods indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH.CONCLUSIONS: In this experimental model of spinal ischemia by AXC, online monitoring of intrathecal PO2, PCO2, and pH showed significant changes and correlated well with epidural laser-Doppler flowmetry (P < .01).
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| 4. |
- Christiansson, Lennart, et al.
(författare)
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Aspects of the spinal cord circulation as assessed by intrathecal oxygen tension monitoring during various arterial interruptions in the pig
- 2001
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Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 121:4, s. 762-772
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: We sought to study the effect of various modes of interruption of the spinal cord blood supply on intrathecal oxygenation.METHODS: In 24 pigs intrathecal PO (2), PCO (2), and pH were continuously monitored with a multiparameter catheter (Paratrend 7, Biomedical Sensors; Diametrics Medical, Inc, St Paul, Minn) during and after aortic crossclamping or selective interruption of segmental arteries and proximal collateral circulation.RESULTS: Proximal aortic clamping (n = 6) produced complete ischemia, whereas a second clamp close to the celiac trunk (n = 4) partly protected against spinal cord ischemia. This is explained by prevention of the steal phenomenon in the excluded part of the aorta. Adding clamps to the subclavian arteries (n = 6) created complete spinal ischemia as the collateral circulation was interrupted. In another group (n = 4) all segmental arteries below T5 were occluded with no reaction in the intrathecal variables. Additional selective clamping of supreme intercostal arteries (n = 4) showed the relative importance of the subclavian and vertebral collateral pathways.CONCLUSIONS: Continuous intrathecal PO (2) was monitored during various modes of interruption of the spinal cord blood supply. This provided insight into the ischemia mechanisms and relative importance of the segmental contribution and proximal collateral pathways of the spinal cord circulation in pigs. A short literature review is given, and aspects of comparative anatomy are discussed.
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| 6. |
- Christiansson, Lennart, et al.
(författare)
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Increased FiO2 improves intrathecal oxygenation during thoracic aortic cross-clamping in pigs
- 2001
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Ingår i: Scandinavian Cardiovascular Journal. - 1401-7431 .- 1651-2006. ; 35:2, s. 147-150
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate the effect of 100% oxygen ventilation on cerebrospinal fluid (CSF) oxygenation in 11 pigs during thoracic aortic cross-clamping.DESIGN: An aorto-aortic shunt was used for control of central hemodynamics and study of hypoperfusion by exsanguination. CSF PO2, PCO2 and pH were continuously monitored before and during clamping. The changes in hemodynamic parameters and intrathecal gas tensions in response to variations in proximal mean aortic pressure and fraction of inspired oxygen (FiO2) were recorded.RESULTS: Baseline CSF PO2 decreased from 4.8 +/- 1.9 to 2.6 +/- 2.2 kPa following aortic occlusion. Increasing FiO2 to 1.0 resulted in a significant increase in CSF PO2 to 4.1 +/- 3.0 with a return to 2.7 +/- 2.1 kPa after reducing FiO2 to 0.4 again. The same variations in FiO2 did not induce any significant changes in CSF PO2 during hypotension.CONCLUSION: Increased FiO2 during experimental thoracic aortic cross-clamping with stable proximal arterial pressure helps to maintain CSF PO2, whereas severe hypotension could not be compensated for by hyperoxemia.
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| 7. |
- Christiansson, Lennart, et al.
(författare)
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Relationship between intrathecal oxygen tension and ultrastructural changes in the spinal cord during experimental aortic clamping
- 2000
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 19:4, s. 413-420
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To investigate spinal cord ultrastructure related to cerebrospinal fluid (CSF) oxygenation.DESIGN: experimental aortic occlusion model with intrathecal oxygen tension monitoring.MATERIALS AND METHODS: Two groups of pigs underwent proximal (P) or double (D) aortic occlusion for 30 min followed by 1 h of reperfusion. In a third group (I) segmental arteries distal to T3 were clamped for 90 min. A thin pO(2), pCO(2) and pH sensor was placed intrathecally for continuous monitoring of CSF. Spinal cord segments were studied by electron microscopy (EM).RESULTS: In group P, CSF-pO(2)rapidly decreased during clamping and major changes in pH and pCO(2)were seen. EM demonstrated neuronal degeneration with loss of cellular integrity and severe affection of organelles. In the group D, CSF oxygenation decreased to about half, but with only moderate changes in the metabolic parameters. Group I showed no significant changes in CSF measurements. The latter groups were similar at EM, showing only mild mitochondrial changes.CONCLUSIONS: The level of CSF oxygenation during aortic cross-clamping or segmental artery interruption seems to correlate with ultrastructural changes in the spinal cord. This online intrathecal monitoring technique may provide valuable information on spinal cord circulation during thoracoabdominal aortic surgery.
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| 8. |
- Christiansson, Lennart
(författare)
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Spinal cord ischemia : An experimental study of the spinal cord blood supply and peroperative ischemia detection by a new method of intrathecal monitoring
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spinal cord ischemia associated with thoracoabdominal aortic surgery may lead to devastating neurological complications. Improvement in bypass techniques and various adjunctive measures has reduced its incidence, but still 5-10 % of the patients develop postoperative paraplegia. There is no universally accepted method for the detection of spinal cord ischemia. Intraoperative monitoring methods are important for the prediction of ischemia and guidance in aorticreplacement strategy. This thesis presents a new technique for continuous peroperative monitoring of intrathecal oxygenation.A multiparameter sensor was used to measure cerebrospinal fluid (CSF) PO2, PCO2 and pH during thoracic aortic cross-clamping in pigs. The findings were experimentally validated by comparisons with epidural laser-Doppler flowmetry and with morphological outcome, as assessed by electron microscopy of immersion fixated spinal cord specimens. The CSF monitoring was used to study functional aspects of segmental and collateral spinal cord blood supply. An experimental model was developed for the study of selective spinal cord ischemia. For this purpose a passive aortic shunt was used.The new monitoring method correlated in the experimental situation with measurements of microcirculation and changes in spinal cord ultrastructure associated with aortic cross-clamping. It proved to be sensitive for detecting ischemia and responded rapidly to alterations in spinal cord circulation. The confounding hemodynamic effects of cross-clamping and systemic reperfusion injuries to the spinal cord could be avoided in the selective ischemia model. The shunt model was also used to study the beneficial effects of hyperoxemia during spinal cord hypoperfusion. In conclusion, this thesis presents a new monitoring method for spinal cord oxygenation during experimental aortic occlusion. The thin flexible sensor can be used percutaneously in humans and comparative studies are needed to correlate the findings with neurophysiological evaluations and clinical outcome.
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| 10. |
- Christiansson, Lennart
(författare)
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Update on adjuvants in regional anaesthesia
- 2009
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Ingår i: Periodicum biologorum. - 0031-5362. ; 111:2, s. 161-170
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Forskningsöversikt (refereegranskat)abstract
- This is a review article on adjuvants to neuroaxial anaesthesia and peripheral nerve blocks used in clinical practice: opioids, vasoconstrictors, clonidine, NMDA antagonists, midazolam, glucocorticoids, nonsteroidal anti-inflammatory drugs and neostigmine. Mechanisam and site of action of each of them is described. It is followed by discussion of experimental and clinical data published in the last five years.
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| 11. |
- Hellberg, Anders, et al.
(författare)
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A prolonged spinal cord ischaemia model in pigs. Passive shunting offers stable central haemodynamics during aortic occlusion
- 2000
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 19:3, s. 318-323
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: to evaluate the effect of a modified aortic shunt on central haemodynamic variables during experimental thoracic aortic occlusion in a prolonged spinal cord ischaemia model.MATERIAL AND METHODS: central haemodynamic variables were evaluated during aortic cross-clamping. In the shunt group (n=11), after the placement of proximal and distal aortic clamps, distal aortic perfusion was restored through an aortoiliac shunt via the left subclavian artery. In the no-shunt group (n=11), spinal cord ischaemia was achieved with only proximal aortic cross-clamping. The clamping time was 60 minutes in the shunt group and 30 minutes in the no-shunt group.RESULTS: in the no-shunt group, all animals needed inotropic support, vasodilators and buffers during the experiment. None of these drugs were needed in the shunt group. In the no-shunt group, cross-clamping caused a significant increase in mean arterial pressure and heart rate compared to baseline values. These variables were stable in the shunt group during aortic occlusion. In the reperfusion period cardiac output, heart rate and arterial pCO(2)were significantly higher in the no-shunt than in the shunt group.CONCLUSION: the present experimental spinal cord ischaemia model, using double aortic cross-clamping with shunt, offers improved central haemodynamics. This enables the study of prolonged selective spinal cord ischaemia without interaction from vasoactive drugs or systemic reperfusion.
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| 12. |
- Hellberg, Anders, et al.
(författare)
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Influence of low proximal aortic pressure on spinal cord oxygenation in experimental thoracic aortic occlusion
- 2001
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Ingår i: Journal of Cardiovascular Surgery. - 0021-9509 .- 1827-191X. ; 42:2, s. 227-231
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: To evaluate the effect of low proximal aortic pressure on cerebrospinal fluid (CSF) oxygenation in an experimental thoracic occlusion model. METHODS: In nine pigs, continuous intrathecal pO(2), pCO(2) and pH monitoring was used during double descending thoracic aortic clamping following insertion of an aorto-aortic shunt. In five pigs, the shunt was connected to a citrated bag adjusted at approximately 40-45 cm above the heart for partial exsanguination in order to decrease mean proximal aortic pressure (MPAP) to below 50 mmHg. In four animals, sodium nitroprusside infusion was used for this purpose. RESULTS: Intrathecal pO(2) demonstrated a significant decrease from 4.9+/-2.1 to 2.9+/-2.4 kPa after 10 minutes of aortic cross-clamping. Lowering proximal aortic pressure caused a further significant decrease to 1.2+/-1.7 kPa (p<0.05). In seven pigs (5 in the exsanguination and 2 in the vasodilator group), restoration of mean proximal aortic pressure to 94.0+/-27.7 caused a recovery of CSF pO(2) from 1.2+/-1.9 to 2.8+/-3.0 (p<0.05). CONCLUSIONS: The results of this study demonstrate that MPAP which provides spinal cord perfusion through subclavian-vertebral arteries are crucial for maintenance of spinal cord oxygenation during thoracic aortic occlusion in this pig model.
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| 13. |
- Hellberg, Anders, et al.
(författare)
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Influence of segmental spinal cord perfusion on intrathecal oxygen tension during experimental thoracic aortic crossclamping
- 2000
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Ingår i: Journal of Vascular Surgery. - 0741-5214. ; 31:1 Pt 1, s. 164-170
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The purpose of this study was to evaluate the possibility of identifying alterations in blood supply to the spinal cord during thoracic aortic crossclamping.METHODS: In 17 pigs, a multiparameter PO(2), PCO(2,) and pH sensor was introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenation during aortic crossclamping. An epidural laser Doppler probe was used to measure spinal cord flux. After insertion of an aortic shunt from the left subclavian to the left iliac artery and interruption of the right subclavian and lumbar arteries (L2-L5), the thoracic aorta just distal to the left subclavian artery was clamped for 60 minutes. By placement of the distal aortic crossclamping below the level of L1 in group A (n = 9 animals), perfusion of only the abdominal visceral arteries was maintained. In group B (n = 8 animals), the distal aortic crossclamping was above the level of T12, and thus some spinal cord perfusion was maintained through the aortic shunt.RESULTS: The significant decrease in CSF PO(2) was observed within 3 minutes after the placement of the proximal aortic crossclamping and was normalized in all animals after establishment of the shunt flow. In group A, distal aortic crossclamping caused a decrease in CSF PO(2) with at least 50% of the preclamping values within 3 minutes. The mean CSF PO(2) of 2.99 +/- 0.70 kPa at 60 minutes of distal aortic crossclamping in group B was significantly higher than in group A (0.11 +/- 0.11 kPa; P <. 001). In group A, PCO(2) measurements showed no significant changes in 3 minutes after distal aortic crossclamping but revealed significantly higher values at 30 and 60 minutes compared with group B. Spinal cord flux values showed similar changes as CSF PO(2) during the whole experiment in both groups.CONCLUSION: In this experimental model of aortic crossclamping, continuous CSF oxygen tension monitoring allows rapid detection of alterations in spinal cord circulation.
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| 14. |
- Hellberg, Anders, et al.
(författare)
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Monitoring of intrathecal oxygen tension during experimental aortic occlusion predicts ultrastructural changes in the spinal cord
- 2001
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Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 121:2, s. 316-323
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study the correlation between intrathecal PO2 and ultrastructural changes in the spinal cord during thoracic aortic occlusion in pigs. MATERIAL AND METHODS: In 18 pigs, online intrathecal oxygenation was monitored by a multiparameter Paratrend catheter (Biomedical Sensors, High Wycombe, United Kingdom) during 60 minutes' clamping of the proximal and distal descending thoracic aorta. The animals were randomly divided into 2 groups (A and B) depending on the level of distal aortic clamping. Distal aortic perfusion was restored through an aorto-iliac shunt, which also maintained low thoracic segmental perfusion of the spinal cord in group B. Perfusion-fixation technique was used before harvesting the spinal cord specimens, which later were evaluated with light and electron microscopy by an independent observer. Intrathecal parameters were interpreted as normal if PO2 was more than 0.8 kPa and PCO2 was less than 12 kPa, as intermediate ischemia if PO2 was 0.8 or less or PCO (2) was more than 12 kPa, and as absolute ischemia if PO2 was 0.8 or less and PCO2 was more than 12 kPa. RESULTS: Among 6 animals with ultrastructural changes of absolute spinal cord ischemia-reperfusion injury, 5 also had absolute ischemia according to variables derived by the Paratrend catheter. The 2 methods were in agreement in 3 of 5 animals with intermediate ischemia-reperfusion changes and in 5 of 6 animals with normal findings. The accuracy of cerebrospinal fluid PO2 and PCO2 to predict electron microscopy-verified intermediate or absolute ischemia-reperfusion injury was 94%. CONCLUSIONS: Monitoring of intrathecal PO2 after clamping of the descending aorta correlated with ultrastructural changes in the spinal cord in this pig model.
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| 20. |
- Koga, Itaru, 1965-
(författare)
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Monitoring of Splanchnic Regional Perfusion : An Experimental Study of New Application and Validation
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Systemic infection, major surgery, trauma and many other causes can lead to impaired organ function. Compensated shock is not detected by global hemodynamic and oxygen measurements, as they take no account for regional variations. Focus has therefore gradually turned from looking at systemic changes to selective investigations of regional blood flow and ischemia. This thesis presents a series of experiments evaluating new application and validation of various monitoring techniques.An experimental porcine model with anesthetized and invasively monitored animals was used. The circulatory interventions included endotoxin infusion (septic shock), aortic constriction and selective clamping of splanchnic arteries. The aim was to compare air with saline tonometry, to validate the intraperitoneal use of tonometry and to reexamine the use of endoluminal reflectance pulse oxymetry. To investigate the relative contributions of regional blood flow and detection of ischemia, measurements of hepatic venous oxygen saturation (ShvO2), lactate concentrations and PCO2 gap were used.Our findings support the use of air instead of saline as the preferred technique for tonometric measurements. With the intraperitoneal application of tonometry we gain more information on regional aspects of the splanchnic circulation, and it appears to be a reliable monitoring option for early detection of ischemia in the small intestine. Measurements of ShvO2 will give an overall reflection of the intestinal circulation. The sigmoid colonic pulse oximetry showed a non-linear response in relation to regional blood flow, and will therefore not be able to detect gradual changes in oxygen saturation. Determination of the regional to endtidal PCO2 gap might prove valuable for monitoring of the intestinal circulation.Because of sophisticated interactions between portal and hepatic arterial blood flow and hepatic compensation for regional ischemia, a combination of monitoring techniques might be needed. The results of this study will hopefully encourage clinical evaluation of intraperitoneal tonometry and endtidal PCO2 gap recordings for non-invasive, semi-continuous, trend monitoring of the splanchnic circulation.
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