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A high blood level in the air trap reduces microemboli during hemodialysis
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
Umeå University, Faculty of Science and Technology, Umeå Institute of Technology.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Medicine.
2012 (English)In: Artificial Organs, ISSN 0160-564X, E-ISSN 1525-1594, Vol. 36, no 6, 525-529 p.Article in journal (Refereed) Published
Abstract [en]

Previous studies have demonstrated the presence of air microemboli in the dialysis circuit and in the venous circulation of the patients during hemodialysis. In vitro studies indicate that a high blood level in the venous air trap reduces the extent of microbubble formation. The purpose of this study was to examine whether air microbubbles can be detected in the patient's access and if so, whether the degree of microbubble formation can be altered by changing the blood level in the venous air trap. This was a randomized, double-blinded, interventional study of 20 chronic hemodialysis patients. The patients were assigned to hemodialysis with either an elevated or a low blood level in the air trap. The investigator and the patient were blinded to the settings. The numbers of microbubbles were measured at the site of the arteriovenous (AV) access for 2 min with the aid of an ultrasonic Doppler device. The blood level in the air trap was then altered to the opposite setting and a new measurement was carried out after an equilibration period of 30 min. Median (range) for the number of microbubbles measured with the high air trap level and the low air trap level in AV access was 2.5 (0-80) compared with 17.5 (0-77), respectively (P = 0.044). The degree of microbubble formation in hemodialysis patients with AV access was reduced significantly if the blood level in the air trap was kept high. The exposure of potentially harmful air microbubbles was thereby significantly reduced. This measure can be performed with no additional healthcare cost.

Place, publisher, year, edition, pages
2012. Vol. 36, no 6, 525-529 p.
National Category
Hematology
Identifiers
URN: urn:nbn:se:umu:diva-56979DOI: 10.1111/j.1525-1594.2011.01415.xISI: 000304751000007OAI: oai:DiVA.org:umu-56979DiVA: diva2:539298
Available from: 2012-07-03 Created: 2012-07-02 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Presence of microemboli during haemodialysis and methods to reduce the exposure to microbubbles
Open this publication in new window or tab >>Presence of microemboli during haemodialysis and methods to reduce the exposure to microbubbles
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite chronic dialysis treatment, patients with end stage renal disease undergoing maintenance haemodialysis (HD) remain at a substantially increased risk of morbidity. Previous reports using Doppler ultrasound (DU) during HD have revealed microembolic signals (ME) in the venous circulation.

In vitro studies confirm the emergence of microbubbles of air that may pass the security system of the HD circuit without triggering the alarm. The aim of this thesis was to elucidate the presence of ME during HD and examine methods that might reduce exposure to ME in vivo.

The first study utilized DU to verify the presence of ME in 40 patients during standard HD. Investigation within 30 minutes after the start of HD and just before the end of session revealed the presence of ME in the venous blood line during both phases. The air trap did not alert for the presence of ME. This indicated that ME may pass into the patient during the entire HD run.

Study 2 analyzed the presence of ME prior to start and during HD when measured at the AV-access and also carotid artery. A total of 54 patients were examined using DU as the investigative technique. ME increased significantly after start of HD in the AV-access, but also at the carotid artery site. These data indicated that ME can enter the body and even pass the lung barrier. The question arose if microbubbles of air are resorbed or may cause ischemic lesions in organs such as the brain.

Study 3 examined whether the amount of ME detected in the AV-access would change by using either a high or a low blood level in the venous air trap/chamber. This was a prospective, randomized and double-blind study of 20 HD patients who were their own controls. After 30 min of standard HD, measurement of ME with DU was performed for two minutes. The chamber setting was changed and after another 30 minutes a new recording was carried out for two minutes. Data showed that setting a high blood level significantly reduced the extent of ME that entered the patient. The results also indicated that ME consisted mainly of microbubbles.

In study 4, twenty patients were randomized in a cross-over setting of HD. Three options were used: a wet-stored dialyzer with high blood level (WH) and a dry-stored dialyzer using either a high (DH) or a low (DL) blood level in the venous chamber. The exposure of ME, detected by DU, was least when using mode WF, more with mode DH, and most with mode DL. There was a correlation between higher blood flow and more extensive exposure to ME.

Study 5 was an autopsy study of a chronic HD patient with the aim of searching for microbubbles deposited in organs. Microbubbles of gas were verified in the vessels of the lungs, brain and heart. By using a fluorescent stain of anti-fibrinogen it was verified that the microbubbles were covered by clots that had to be preformed before death occurred. This indicated that air microbubbles are not completely absorbed and could result in embolic deposition in the organs of HD patients.

In conclusion, these in vivo studies showed that ME pass the air trap without inducing an alarm and enter the venous blood line of the patient. The data confirmed the presence of ME in the AV-access and also in the carotid artery. Autopsy data of a deceased HD patient demonstrated the presence of microbubbles in the capillaries of the lungs, but also in the systemic circulation such as in the brain and the heart. A high blood level in the venous chamber and wet-stored dialyzer can reduce, but not eliminate the exposure to microbubbles for patients undergoing HD.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2013. 106 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1564
Keyword
Haemodialysis, in vivo, microemboli, microbubbles, dialyzer, air trap, venous chamber
National Category
Other Clinical Medicine Urology and Nephrology
Identifiers
urn:nbn:se:umu:diva-68674 (URN)978-91-7459-591-8 (ISBN)
Public defence
2013-05-16, Sal E04, Norrlands universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2013-04-25 Created: 2013-04-22 Last updated: 2013-04-25Bibliographically approved

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Forsberg, UlfJonsson, PerStegmayr, Bernd

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