Experimental assessment of oxygen homeostasis during acute hemodilution: the integrated role of hemoglobin concentration and blood pressure

Kei, Tiffanie; Mistry, Nikhil; Tsui, Albert K.Y.; Liu, Elaine; Rogers, Stephen C.; Doctor, Allan; Wilson, David F.; Desjardins, Jean-François; Connelly, Kim A.; Mazer, C. David; Hare, Gregory M. T.

doi:10.1186/s40635-017-0125-6

Cited by 10 publications

(5 citation statements)

References 50 publications

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“…As flow reserves become exhausted, extraction reserves are accessed and symptomatic impairment occurs, as seen in carotid stentosis 49,50 . In more extreme animal models of hemodilution, oxygen extraction and metabolic rate typically remain in the normal range until oxygen content is lowered below 40% 51‐53 . In this current cross‐sectional study, the oxygen content in our anemic subjects was 72 ± 14% of the control cohort, much higher than hemoglobin levels associated with increased OEF in animal studies.…”

Section: Discussionmentioning

confidence: 58%

“…49,50 In more extreme animal models of hemodilution, oxygen extraction and metabolic rate typically remain in the normal range until oxygen content is lowered below 40%. [51][52][53] In this current cross-sectional study, the oxygen content in our anemic subjects was 72 ± 14% of the control cohort, much higher than hemoglobin levels associated with increased OEF in animal studies. More importantly, our subjects have experienced anemia for decades, allowing possible chronic compensation such as vascular remodeling 54,55 and alterations in oxygen diffusional paths 56 to affect oxygen unloading in the microvasculature.…”

Section: Discussionmentioning

confidence: 99%

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Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias

Bush

Choi

et al. 2021

American J Hematol

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Anemia is the most common blood disorder in the world. In patients with chronic anemia, such as sickle cell disease or major thalassemia, cerebral blood flow increases to compensate for decreased oxygen content. However, the effects of chronic anemia on oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO 2 ) are less well understood. In this study, we examined 47 sickle-cell anemia subjects (age 21.7 ± 7.1, female 45%), 27 non-sickle anemic subjects (age 25.0 ± 10.4, female 52%) and 44 healthy controls (age 26.4 ± 10.6, female 71%) using MRI metrics of brain oxygenation and flow. Phase contrast MRI was used to measure resting cerebral blood flow, while T 2 -relaxation-under-spin-tagging (TRUST) MRI with disease appropriate calibrations were used to measure OEF and CMRO 2 . We observed that patients with sickle cell disease and other chronic anemias have decreased OEF and CMRO 2 (respectively 27.4 ± 4.1% and 3.39 ± 0.71 ml O 2 /100 g/ min in sickle cell disease, 30.8 ± 5.2% and 3.53 ± 0.64 ml O 2 /100 g/min in other anemias) compared to controls (36.7 ± 6.0% and 4.00 ± 0.65 ml O 2 /100 g/min). Impaired CMRO 2 was proportional to the degree of anemia severity. We further demonstrate striking concordance of the present work with pooled historical data from patients having broad etiologies for their anemia. The reduced cerebral oxygen extraction and metabolism are consistent with emerging data demonstrating increased non-nutritive flow, or physiological shunting, in sickle cell disease patients.Ms. Vu and Dr. Bush contributed equally and are designated as co-first authors.

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Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias

Bush

Choi

et al. 2021

American J Hematol

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“…Our findings were similar to what has been observed in experimental assessments of brain and muscle oxygen homeostasis during acute hemodilution. 52 With the low-trigger strategy, the cerebral desaturation load increased, whereas the muscle oxygenation was unaffected. This could be explained by the fact that the muscles have a lower oxygen metabolism during anesthesia and surgery, and that muscle oxygenation mostly depends on cardiac output.…”

Section: Discussionmentioning

confidence: 99%

Low vs high hemoglobin trigger for transfusion in vascular surgery: a randomized clinical feasibility trial

Møller

Nielsen²,

Wetterslev

et al. 2019

Blood

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Current guidelines advocate to limit red blood cell (RBC) transfusion during surgery, but the feasibility and safety of such a strategy remain unclear, as the majority of evidence is based on postoperatively stable patients. We assessed the effects of a protocol aiming to restrict RBC transfusion throughout hospitalization for vascular surgery. Fifty-eight patients scheduled for lower limb bypass or open abdominal aortic aneurysm repair were randomly assigned, on hemoglobin drop below 9.7 g/dL, to either a low-trigger (hemoglobin < 8.0 g/dL) or a high-trigger (hemoglobin < 9.7 g/dL) group for RBC transfusion. Near-infrared spectroscopy assessed intraoperative oxygen desaturation in brain and muscle. Explorative outcomes included nationwide registry data on death and major vascular complications. The primary outcome, mean hemoglobin within 15 days of surgery, was significantly lower in the low-trigger group, at 9.46 vs 10.33 g/dL in the high-trigger group (mean difference, −0.87 g/dL; P = .022), as were units of RBCs transfused (median [interquartile range (IQR)], 1 [0-2] vs 3 [2-6]; P = .0015). Although the duration and magnitude of cerebral oxygen desaturation increased in the low-trigger group (median [IQR], 421 [42-888] vs 127 [11-331] minutes × %; P = .0036), muscle oxygenation was unaffected. The low-trigger group associated to a higher rate of death or major vascular complications (19/29 vs 8/29; hazard ratio, 3.20; P = .006) and fewer days alive outside the hospital within 90 days (median [IQR], 76 [67-82] vs 82 [76-84] days; P = .049). In conclusion, a perioperative protocol restricting RBC transfusion successfully separated hemoglobin levels and RBC units transfused. Exploratory outcomes suggested potential harm with the low-trigger group and warrant further trials before such a strategy is universally adopted. This trial was registered at www.clinicaltrials.gov as #NCT02465125.

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“…Mechanisms controlling cerebral blood flow following a decrease in CaO 2 are multifactorial, but increased cerebral perfusion seems to be provoked by deoxygenation of haemoglobin, and haemodilution may reduce the signal transduction originating from the RBCs 22 . Also, anaesthetized rats exposed to acute normotensive haemodilution to a Hb < 7 g/dL demonstrate a decrease in cerebral oxygenation while muscle oxygenation seems unaffected as determined by invasive tissue oximetry 23 . That animal model corroborates the present findings and suggests that haemodiluting Hb below 7‐8 g/dL is too large to maintain cerebral oxygenation although increased arterio‐venous O 2 ‐extraction may secure cerebral oxygen consumption.…”

Section: Discussionmentioning

confidence: 99%

Effect of low vs high haemoglobin transfusion trigger on cardiac output in patients undergoing elective vascular surgery: Post‐hoc analysis of a randomized trial

Møller

Wetterslev

Shahidi

et al. 2020

Acta Anaesthesiol Scand

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Background During vascular surgery, restricted red‐cell transfusion reduces frontal lobe oxygen (ScO2) saturation as determined by near‐infrared spectroscopy. We evaluated whether inadequate increase in cardiac output (CO) following haemodilution explains reduction in ScO2. Methods This is a post‐hoc analysis of data from the Transfusion in Vascular surgery (TV) Trial where patients were randomized on haemoglobin drop below 9.7 g/dL to red‐cell transfusion at haemoglobin below 8.0 (low‐trigger) vs 9.7 g/dL (high‐trigger). Fluid administration was guided by optimizing stroke volume. We compared mean intraoperative levels of CO, haemoglobin, oxygen delivery, and CO at nadir ScO2 with linear regression adjusted for age, operation type and baseline. Data for 46 patients randomized before end of surgery were included for analysis. Results The low‐trigger resulted in a 7.1% lower mean intraoperative haemoglobin level (mean difference, −0.74 g/dL; P < .001) and reduced volume of red‐cell transfused (median [inter‐quartile range], 0 [0‐300] vs 450 mL [300‐675]; P < .001) compared with the high‐trigger group. Mean CO during surgery was numerically 7.3% higher in the low‐trigger compared with the high‐trigger group (mean difference, 0.36 L/min; 95% confidence interval (CI.95), −0.05 to 0.78; P = .092; n = 42). At the nadir ScO2‐level, CO was 11.9% higher in the low‐trigger group (mean difference, 0.58 L/min; CI.95, 0.10‐1.07; P = .024). No difference in oxygen delivery was detected between trial groups (MD, 1.39 dLO2/min; CI.95, −6.16 to 8.93; P = .721). Conclusion Vascular surgical patients exposed to restrictive RBC transfusion elicit the expected increase in CO making it unlikely that their potentially limited cardiac capacity explains the associated ScO2 decrease.

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Experimental assessment of oxygen homeostasis during acute hemodilution: the integrated role of hemoglobin concentration and blood pressure

Cited by 10 publications

References 50 publications

Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias

Reduced global cerebral oxygen metabolic rate in sickle cell disease and chronic anemias

Low vs high hemoglobin trigger for transfusion in vascular surgery: a randomized clinical feasibility trial

Effect of low vs high haemoglobin transfusion trigger on cardiac output in patients undergoing elective vascular surgery: Post‐hoc analysis of a randomized trial

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