Hgh Oxygen Concentration Helps Anemic Patients

[BLADEMDA]

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Anesthesiology:
September 2011 - Volume 115 - Issue 3 - p 492–498
doi: 10.1097/ALN.0b013e31822a22be
Perioperative Medicine

High Oxygen Partial Pressure Decreases Anemia-induced Heart Rate Increase Equivalent to Transfusion

Feiner, John R. M.D.*; Finlay-Morreale, Heather E. M.D.†; Toy, Pearl M.D.‡; Lieberman, Jeremy A. M.D.*; Viele, Maurene K. M.D.§; Hopf, Harriet W. M.D.‖; Weiskopf, Richard B. M.D.#



Background: Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. The authors sought to directly compare the effect of high inspired oxygen fraction versus transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia.
Methods: The authors combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by the group. HR changes associated with breathing 100% oxygen by nonrebreathing facemask versus transfusion of erythrocytes at their nadir hemoglobin concentration of 5 g/dl were examined. Data were analyzed using a mixed-effects model.
Results: HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per min per gram of hemoglobin (beats/min/g hemoglobin) decrease (95% CI, 3.7&#8211;4.1 beats/min/g hemoglobin), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g hemoglobin (95% CI, 3.8&#8211;6.8 beats/min/g hemoglobin) increase, P < 0.0001. HR at nadir hemoglobin of 5.6 g/dl (95% CI, 5.5&#8211;5.7 g/dl) when breathing air (91.4 beats/min; 95% CI, 87.6&#8211;95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0&#8211;87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dl when breathing oxygen was equivalent to the HR at hemoglobin 8.9 g/dl when breathing air.
Conclusions: High arterial oxygen partial pressure reverses the heart rate response to anemia, probably because of its usability rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials.

 

[BLADEMDA]

It seems reasonable to use as much as 80% FiO2 in this subgroup of severely anemic patients or those with anemia and tachycardia.

I would personally avoid 100% as that causes atelectasis. While the study was very interesting severe anemia and tachycardia should still be treated with transfusion most of the time.

Trauma patients or SHTF cases should get 100% FIO2.

 

[nap$ter]

interesting. not sure how useful though.

HR is only one value in a myriad of indicators and endpoints.

how does a HR change in an anemic healthy young volunteer correlate with oxygen delivery and perfusion in a bleeding typical patient, who is only sometimes young or healthy?

if sats are >98 and SHTF i'll do what i've always done - keep fio2 at 80. i'm not gonna depend on solubilized O2 - as blade points out atelectasis would likely outweigh any benefit from going from 80 to 100%.

also, it's pretty tough to give an actual 100% fio2 even with a non-rebreather - they were likely at 80-90%.

 

[Bertelman]

If your goal was to lower HR, you could also just give BB.

 

[DrN2O]

If your goal was to lower HR, you could also just give BB.

I believe the point is to maximize oxygen delivery = CO x O2 content. BB would lower the HR and drop the CO without doing much for the O2 content.

Of course, the studies used isovolemic hemodilution and replaced the blood with either albumin or plasma. So it would not be straight forward applicable to trauma patients. High FiO2 also causes rapid atelectasis in patients under GA and will not give you PaO2 of 400 or 500 for very long. So I find it hard to believe that FiO2 of 1 can give you 3 g of hgb in a real clinical situation.

 

[epidural man]

Anesthesiology:
September 2011 - Volume 115 - Issue 3 - p 492–498
doi: 10.1097/ALN.0b013e31822a22be
Perioperative Medicine

High Oxygen Partial Pressure Decreases Anemia-induced Heart Rate Increase Equivalent to Transfusion

Feiner, John R. M.D.*; Finlay-Morreale, Heather E. M.D.†; Toy, Pearl M.D.‡; Lieberman, Jeremy A. M.D.*; Viele, Maurene K. M.D.§; Hopf, Harriet W. M.D.&#8214;; Weiskopf, Richard B. M.D.#



Background: Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. The authors sought to directly compare the effect of high inspired oxygen fraction versus transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia.
Methods: The authors combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by the group. HR changes associated with breathing 100% oxygen by nonrebreathing facemask versus transfusion of erythrocytes at their nadir hemoglobin concentration of 5 g/dl were examined. Data were analyzed using a mixed-effects model.
Results: HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per min per gram of hemoglobin (beats/min/g hemoglobin) decrease (95% CI, 3.7–4.1 beats/min/g hemoglobin), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g hemoglobin (95% CI, 3.8–6.8 beats/min/g hemoglobin) increase, P < 0.0001. HR at nadir hemoglobin of 5.6 g/dl (95% CI, 5.5–5.7 g/dl) when breathing air (91.4 beats/min; 95% CI, 87.6–95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0–87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dl when breathing oxygen was equivalent to the HR at hemoglobin 8.9 g/dl when breathing air.
Conclusions: High arterial oxygen partial pressure reverses the heart rate response to anemia, probably because of its usability rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials.

why not do both?

 

[sevoflurane]

Just to add to the topic at hand:

It is now more than a decade since CT studies first demonstrated that preoxygenation leads to greater areas of atelectasis after induction.5 For example, if FIO2 before induction is 0.3, 0.6, 0.8, or 1.0, the mean percentage of atelectasis seen on CT scans post-induction is 0.2%, 0.2%, 1.3%, and 5.6% respectively

The presence of more than 8% atelectasis immediately after operation is clinically very significant as re-expansion of this collapsed lung after major surgery may take some days........

However, despite the lack of statistical difference between the groups in this small study, only four of 14 patients with an intraoperative FIO2 of 0.3 had more than 2% atelectasis after operation compared with 10 of 14 in the FIO2 of 0.8 group. These results also provide some reassurance that the atelectasis seen so commonly during anaesthesia may be partially resolved 24 h after the anaesthetic.
Collectively, these studies offer good evidence that the amount of atelectasis during anaesthesia increases significantly with increasing FIO2 and that the use of oxygen 100% at any stage of an anaesthetic is associated with significant pulmonary collapse. Reducing FIO2, even by a small amount to 0.8, seems to be substantially better than using oxygen alone.

http://forums.studentdoctor.net/showthread.php?t=703705&highlight=absorption+atelectasis




If your patient doesn't need an fio2 of .8, then why give it to them?

It drives me nuts to see a healthy 25 y/o on an Fio2 of .8-1.0 for a 4 hour case. Maybe I'm just picky.

 

[Bertelman]

Much of this has been touched on by others in this thread, but here's my opinion:

As mentioned, this is a controlled study of completely healthy volunteers, no significant cardiac or respiratory disease, who were driven down to a Hb of 5.6 while maintaining isovolemia. The endpoint was HR, nothing more. Increasing the PaO2 to 400 changed the HR by a grand total of 12 points, from 92 to 80.

What this tells me is that if I have an isovolemic young healthy adult with a Hb <7, I can buy 10 or so points of HR if I jack their FiO2 up to 1. Of course, I'm never really worried about the HR in that patient population, though, right? I certainly can't think of too many clinical scenarios outside of scoli repairs where an otherwise young, healthy adult is isovolemic and profoundly anemic in the OR.

Furthermore, the suggestion is that decreasing HR may decrease myocardial O2 demand, and thus decrease the risk of ischmeia. But again, you're not really worried about that in this population. You're worried about that with the elderly patient with CAD, PVD, DM, HTN. In other words, the exact population that was NOT tested in this study. So, if you are hoping to decrease the HR of your next anemic dialysis pt. who shows up for surgery, I wouldn't count on standing on this paper to support your decision.

The authors then provide reference to data which shows that HR may not even increase at all in the face of anemia while patients are receiving opioids and GA. Any changes in HR are also difficult to interpret in the setting of surgical stimulation.

Most importantly, they admit that the mechanism for the change in HR related to Hb is unknown. So really, we don't know what we're treating to drop the HR, and we don't know if it has any meaningful clinical correlation or impact on outcome.