G Model
ARTICLE IN PRESS
RESUS 5932 1
Resuscitation xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
1
Letter to the Editor
2
3
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Reply to letter: “Regional cerebral oxygen saturation monitoring during cardiac arrest”
of cerebral oximetry during cardiac arrest as a novel non-invasive tool to measure the quality of cerebral resuscitation.
Sir,
Conflict of interest statement
We are grateful for Dr Gwinnutt’s comments regarding our study of cerebral oximetry using near infrared spectroscopy (NIRS) during cardiac arrest. We certainly agree that further exploration in this emerging field is necessary. However, we would also like to point out that most of the early studies using cerebral oximetry (including those that have been referenced in the letter) were carried out using a system that is different to what we have utilized (Invos; Somanetics, USA).1,2 It is currently not known whether the results obtained using the Invos system can be extrapolated to other newer systems such as the Equanox (Nonin, USA) which is the system we used in our study. However, we acknowledge that the impact of changes in oxygen and carbon dioxide on cerebral oximetry are complex. Studies have shown that even though, cerebral blood flow is affected little by changes in the PaO2 in the normal range, hypoxemia with SaO2 below 90% leads to an increase in cerebral perfusion as measured by transcranial Doppler.3 Cerebral blood flow and perfusion are also linearly related to PaCO2 ; cerebral vasodilatation occurs during hypercapnia and vasoconstriction during hypocapnia4 and consequently cerebral oximetry values correlate well with changes in CO2 values.5,6 Nonetheless, the Equanox system has been validated during hypoxic episodes.7 As regard to the impact of CO2 on cerebral oximetry readings, it would be expected that changes in CO2 will impact rSO2 readings based upon their impact on vasodilatation or vasoconstriction and consequently cerebral blood flow. While we also agree that it is important to identify ways to accurately measure “what is happening at a tissue level in the brains of patients during a cardiac arrest”, we realize that this may not be practical during cardiac arrest. However we do not feel, the inability to do this due to practical reasons should detract from the use
33 34
35
None declared.
36
References
37
1. Pollard V, Prough DS, DeMelo AE, Deyo DJ, Uchida T, Stoddart HF. Validation in volunteers of a near-infrared spectroscope for monitoring brain oxygenation in vivo. Anesth Analg 1996;82:269–77. 2. Pollard V, Prough DS, DeMelo AE, Deyo DJ, Uchida T, Widman R. The influence of carbon dioxide and body position on near-infrared spectroscopic assessment of cerebral hemoglobin oxygen saturation. Anesth Analg 1996;82:278–87. 3. Gupta AK, Menon DK, Czosnyka M, Smielewski P, Jones JG. Thresholds for hypoxic cerebral vasodilation in volunteers. Anesth Analg 1997;85:817–20. 4. Harper AM, Glass HI. Effect of alterations in the arterial carbon dioxide tension on the blood flow through the cerebral cortex at normal and low arterial pressures. J Neurol Neurosurg Psychiatr 1965;28:449–52. 5. Smielewski P, Kirkpatrick P, Minhas P, Pickard JD, Czosnyka M. Can cerebrovascular reactivity be measured with NIRS? Stroke 1995;26:2285–92. 6. Smielewski P, Czosnyka M, Pickard JD, Kirkpatrick P. Clinical evaluation of nearinfrared spectroscopy for testing cerebrovascular reactivity in patients with carotid artery disease. Stroke 1997;28:331–8. 7. MacLeod DB, Ikeda K, Vacchiano C, Lobbestael A, Wahr JA, Shaw AD. Development and validation of a cerebral oximeter capable of absolute accuracy. J Cardiothorac Vasc Anesth 2012;26:1007–14.
Sam Parnia Q1 Resuscitation Research Group, State University of New York at Stony Brook, Stony Brook University Hospital, T17-040, Health Sciences Center, Stony Brook, NY 11794-8172, USA E-mail address: [email protected] 14 March 2014 Available online xxx
http://dx.doi.org/10.1016/j.resuscitation.2014.03.011 0300-9572/© 2014 Published by Elsevier Ireland Ltd.
Please cite this article in press as: Parnia S. Reply to letter: “Regional cerebral oxygen saturation monitoring during cardiac arrest”. Resuscitation (2014), http://dx.doi.org/10.1016/j.resuscitation.2014.03.011
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56
57 58 59 60 61 62 63
64 65
ARTICLE IN PRESS
RESUS 5932 1
Resuscitation xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
1
Letter to the Editor
2
3
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Reply to letter: “Regional cerebral oxygen saturation monitoring during cardiac arrest”
of cerebral oximetry during cardiac arrest as a novel non-invasive tool to measure the quality of cerebral resuscitation.
Sir,
Conflict of interest statement
We are grateful for Dr Gwinnutt’s comments regarding our study of cerebral oximetry using near infrared spectroscopy (NIRS) during cardiac arrest. We certainly agree that further exploration in this emerging field is necessary. However, we would also like to point out that most of the early studies using cerebral oximetry (including those that have been referenced in the letter) were carried out using a system that is different to what we have utilized (Invos; Somanetics, USA).1,2 It is currently not known whether the results obtained using the Invos system can be extrapolated to other newer systems such as the Equanox (Nonin, USA) which is the system we used in our study. However, we acknowledge that the impact of changes in oxygen and carbon dioxide on cerebral oximetry are complex. Studies have shown that even though, cerebral blood flow is affected little by changes in the PaO2 in the normal range, hypoxemia with SaO2 below 90% leads to an increase in cerebral perfusion as measured by transcranial Doppler.3 Cerebral blood flow and perfusion are also linearly related to PaCO2 ; cerebral vasodilatation occurs during hypercapnia and vasoconstriction during hypocapnia4 and consequently cerebral oximetry values correlate well with changes in CO2 values.5,6 Nonetheless, the Equanox system has been validated during hypoxic episodes.7 As regard to the impact of CO2 on cerebral oximetry readings, it would be expected that changes in CO2 will impact rSO2 readings based upon their impact on vasodilatation or vasoconstriction and consequently cerebral blood flow. While we also agree that it is important to identify ways to accurately measure “what is happening at a tissue level in the brains of patients during a cardiac arrest”, we realize that this may not be practical during cardiac arrest. However we do not feel, the inability to do this due to practical reasons should detract from the use
33 34
35
None declared.
36
References
37
1. Pollard V, Prough DS, DeMelo AE, Deyo DJ, Uchida T, Stoddart HF. Validation in volunteers of a near-infrared spectroscope for monitoring brain oxygenation in vivo. Anesth Analg 1996;82:269–77. 2. Pollard V, Prough DS, DeMelo AE, Deyo DJ, Uchida T, Widman R. The influence of carbon dioxide and body position on near-infrared spectroscopic assessment of cerebral hemoglobin oxygen saturation. Anesth Analg 1996;82:278–87. 3. Gupta AK, Menon DK, Czosnyka M, Smielewski P, Jones JG. Thresholds for hypoxic cerebral vasodilation in volunteers. Anesth Analg 1997;85:817–20. 4. Harper AM, Glass HI. Effect of alterations in the arterial carbon dioxide tension on the blood flow through the cerebral cortex at normal and low arterial pressures. J Neurol Neurosurg Psychiatr 1965;28:449–52. 5. Smielewski P, Kirkpatrick P, Minhas P, Pickard JD, Czosnyka M. Can cerebrovascular reactivity be measured with NIRS? Stroke 1995;26:2285–92. 6. Smielewski P, Czosnyka M, Pickard JD, Kirkpatrick P. Clinical evaluation of nearinfrared spectroscopy for testing cerebrovascular reactivity in patients with carotid artery disease. Stroke 1997;28:331–8. 7. MacLeod DB, Ikeda K, Vacchiano C, Lobbestael A, Wahr JA, Shaw AD. Development and validation of a cerebral oximeter capable of absolute accuracy. J Cardiothorac Vasc Anesth 2012;26:1007–14.
Sam Parnia Q1 Resuscitation Research Group, State University of New York at Stony Brook, Stony Brook University Hospital, T17-040, Health Sciences Center, Stony Brook, NY 11794-8172, USA E-mail address: [email protected] 14 March 2014 Available online xxx
http://dx.doi.org/10.1016/j.resuscitation.2014.03.011 0300-9572/© 2014 Published by Elsevier Ireland Ltd.
Please cite this article in press as: Parnia S. Reply to letter: “Regional cerebral oxygen saturation monitoring during cardiac arrest”. Resuscitation (2014), http://dx.doi.org/10.1016/j.resuscitation.2014.03.011
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56
57 58 59 60 61 62 63
64 65
