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Intensive buffering can keep pH above 7.2 for over 4 h during apnea: an experimental porcine study
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Anaesthesiology and Intensive Care.
2013 (English)In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 57, no 1, 63-70 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND:

Ventilation with low tidal volumes reduces mortality in acute respiratory distress syndrome. A further reduction of tidal volumes might be beneficial, and it is known that apneic oxygenation (no tidal volumes) with arteriovenous CO(2) removal can keep acid-base balance and oxygenation normal for at least 7 h in an acute lung injury model. We hypothesized that adequate buffering might be another approach and tested whether tris-hydroxymethyl aminomethane (THAM) alone could keep pH at a physiological level during apneic oxygenation for 4 h.

METHODS:

Six pigs were anesthetized, muscle relaxed, and normoventilated. The lungs were recruited, and apneic oxygenation as well as administration of THAM, 20 mmol/kg/h, was initiated. The experiment ended after 270 min, except one that was studied for 6 h.

RESULTS:

Two animals died before the end of the experiment. Arterial pH and arterial carbon dioxide tension (PaCO(2) ) changed from 7.5 (7.5, 7.5) to 7.3 (7.2, 7.3) kPa, P < 0.001 at 270 min, and from 4.5 (4.3, 4.7) to 25 (22, 28) kPa, P < 0.001, respectively. Base excess increased from 5 (3, 6) to 54 (51, 57) mM, P < 0.001. Cardiac output and arterial pressure were well maintained. The pig, which was studied for 6 h, had pH 7.27 and PaCO(2) 27 kPa at that time.

CONCLUSION:

With intensive buffering using THAM, pH can be kept in a physiologically acceptable range for 4 h during apnea.

Place, publisher, year, edition, pages
2013. Vol. 57, no 1, 63-70 p.
National Category
Medical and Health Sciences
Research subject
Clinical Physiology
Identifiers
URN: urn:nbn:se:uu:diva-188729DOI: 10.1111/aas.12012ISI: 000312271800009PubMedID: 23167283OAI: oai:DiVA.org:uu-188729DiVA: diva2:578812
Available from: 2012-12-19 Created: 2012-12-19 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Minimal volume ventilation in lung injury: With special reference to apnea and buffer treatment
Open this publication in new window or tab >>Minimal volume ventilation in lung injury: With special reference to apnea and buffer treatment
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A fairly large portion of patients receiving surgical or intensive care will need mechanical ventilation at some point. The potential ventilator-induced lung injury (VILI) is thus of interest. One of the main causal factors in VILI is the cyclic energy shifts, i.e. tidal volumes, in the lung during mechanical ventilation. The problem can be approached in two ways. Firstly, one can utilize apneic oxygenation and thus not cause any tidal injuries at all. Secondly, and more traditionally, one can simply lower the tidal volumes and respiratory rates used. The following describes a series of animal experiments exploring these options.

In the first two papers, I explored and improved upon the methodology of apneic oxygenation. There is a generally held belief that it is only possible to perform apneic oxygenation by prior denitrogenation and by using 100% oxygen during the apnea. As 100% oxygen is toxic, this has prevented apneic oxygenation from more widespread use. The first paper proves that it is indeed possible to perform apneic oxygenation with less than 100% oxygen. I also calculated the alveolar nitrogen concentration which would conversely give the alveolar oxygen concentration. The second paper addresses the second large limitation of apneic oxygenation, i.e. hypercapnia. Using a high dose infusion of tris(hydroxymethyl)aminomethane (THAM) buffer, a pH > 7.2 could be maintained during apneic oxygenation for more than 4.5 hours.

In the last two papers, THAM’s properties as a proton acceptor are explored during respiratory acidosis caused by very low volume ventilation. In paper III, I found that THAM does not, in the long term, affect pH in respiratory acidosis after stopping the THAM infusion. It does, however, lower PVR, even though the PaCO2 of THAM-treated animals had rebounded to levels higher than that of the controls. In the last experiment, I used volumetric capnography to confirm our hypothesis that carbon dioxide elimination through the lungs was lower during the THAM infusion. Again, the PaCO2 rebounded after the THAM infusion had stopped and I concluded that renal elimination of protonated THAM was not sufficient.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1267
Keyword
VILI, THAM, buffers, apneic oxygenation, respiratory acidosis, hypercapnia, low volume ventilation, mechanical ventilation, ultra-protective ventilation
National Category
Anesthesiology and Intensive Care
Research subject
Anaesthesiology and Intensive Care
Identifiers
urn:nbn:se:uu:diva-305369 (URN)978-91-554-9727-9 (ISBN)
Public defence
2016-12-02, Grönwallsalen, Ing 70, Akademiska Sjukhuset, Uppsala, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2016-11-10 Created: 2016-10-16 Last updated: 2016-11-16

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Höstman, StaffanEngström, JoakimHedenstierna, GöranLarsson, Anders

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