If you wish to respond to a paper or other item already published in the BJA, please go to the abstract/full text version of that item and click on the link "E-Letters: Submit a response to the article".
Electronic Letters to:
|
|
E-letters: Electronic letters published:
-
![[Read E-letter]](/icons/misc/sectionDOWN.gif)
Author response to "Is a decrease in capillary density dangerous?"
- Jean-Louis Vincent, Daniel de Backer, Marc Koch (3 January 2009)
-
Is a Decrease in Capillary Density Dangerous
- Simon Gelman (16 November 2008)
|
|
|||
|
Jean-Louis Vincent , Daniel de Backer, Marc Koch
Send letter to journal:
|
We agree with Dr Gelman that it is not possible to determine whether the propofol-induced decrease in small vessel density we observed (1) was a detrimental effect of the propofol or an adaptative response, as we did not measure local metabolism or local indices of tissue hypoxia. However, a decrease in capillary density is not a typical finding in the microvascular adjustment to decreased local metabolism, which is rather characterized by a decrease in microvascular flow velocity (2,3). In addition, using near infrared spectroscopy, De Blasi et al. (4) recently reported that propofol anaesthesia did not alter muscle oxygen consumption (VO2). In agreement with our findings, these authors also reported that the post-ischaemic haemoglobin reoxygenation slope was decreased after propofol anaesthesia, which indirectly suggests that microvascular recruitment was altered. Altogether, these data suggest that propofol decreases microvascular perfusion by a non-homeostatic mechanism. This may have detrimental consequences in a diseased microcirculation. Daniel De Backer,1 Marc Koch,2 and Jean-Louis Vincent1 Departments of Intensive Care1 and Anaesthesiology2, Erasme Hospital, Université Libre de Bruxelles, Belgium References 1 Koch M, De Backer D, Vincent JL, Barvais L, Hennart D, Schmartz D. Effects of propofol on human microcirculation. Br J Anaesth 2008; 101: 473 -8. 2 Berg BR, Cohen KD, Sarelius IH. Direct coupling between blood flow and metabolism at the capillary level in striated muscle. Am J Physiol 1997; 272: H2693-H2700. 3 Ferreira LF, Padilla DJ, Musch TI, Poole DC. Temporal profile of rat skeletal muscle capillary haemodynamics during recovery from contractions. J Physiol 2006; 573: 787-97. 4 De Blasi RA, Palmisani S, Boezi M et al. Effects of remifentanil- based general anaesthesia with propofol or sevoflurane on muscle microcirculation as assessed by near-infrared spectroscopy. Br J Anaesth 2008; 101: 171-7. Conflict of Interest:None declared |
|||
|
|
|||
|
Simon Gelman, Anesthesiologist Brigham & Women's Hospital, Boston, MA
Send letter to journal:
|
Editor: I would agree with the authors’ interpretation of the interesting observations (1) that not only propofol by itself but associated hyperoxia and increases in sympathetic discharge may affect the microcirculation. What are the clinical implications of the observations? Could it be potentially dangerous deterioration of microcirculation induced by propofol, or could an observed decrease in capillary density simply reflect a decrease in oxygen demand within the tissues (due to slight decrease in temperature, hyperoxia, propofol induced decrease in metabolic requirements) and metabolically mediated autoregulation of nutritive flow? In other words, could tissues require less oxygen and decrease capillary density in order to meet this decreased requirement? The authors correctly speculate that as reported in the literature no change in capillary filtration coefficient during propofol anesthesia probably reflects absence of increase in microvascular permeability and, one can speculate further, may reflect also an absence of oxygen deprivation. Thus, the question is whether these observations reflect any real homeostatic disturbance or an adjustment to a decrease in metabolic/oxygen requirements? Simon Gelman, MD, PhD, Department of Anesthesiology, Perioperative and Pain Medicine Brigham and Women’s Hospital Boston, MA Reference: 1. Koch M, De Backer D, Vincent JL, Barvain S, Hennart D, Schmartz D. Effects of propofol on human microcirculation. Brit J Anest. 2008; 101:473 -8. Conflict of Interest:None declared |
|||