Introduction: Anemia is common in patients with aneurysmal subarachnoid hemorrhage (SAH) and is associated with compromised cerebral oxygen delivery and metabolism. Despite historical liberal transfusion targets, there is no established evidence that transfusion improves outcome in anemic patients with SAH. Furthermore, conservative transfusion thresholds have been shown to be equivalent to more aggressive regimens. Transfusion has been proposed to worsen cerebral vasospasm after SAH by disrupting the nitric oxide signalling pathway. This hypothesis has not yet been tested clinically.
Methods: Fifty-five patients between 19 and 70 years with aneurysmal SAH diagnosed by CT angiography and/or digital subtraction angiography were enrolled. Patients with the following were excluded: moribund prognosis, prior severe neurologic injury (severe TBI, prior stroke), non-aneurysmal source of hemorrhage, and shock or cardiac failure requiring ionotropic support. Patients were transfused based on clinical grounds by the treating neurosurgeon. Transcranial Doppler ultrasonography was performed and mean flow velocities were obtained both immediately prior to transfusion and two hours after transfusion.
Results: Mean age was 59 years (range 44-72) and 88% of patients were women. Eight patients were transfused between days 4 and 22 post-hemorrhage (average 13.6 ± 7.7). Vasospasm worsened in six arteries in four patients receiving transfusion. Average pre-transfusion mean flow velocity (MFV) and from 14 MCAs was 88.8 (± 39.6) cm/sec. Average post-transfusion MFV from 15 MCAs was 109.2 (±67.2) cm/sec. Paired t-test revealed no significant difference (p=0.113). Average pre-transfusion MFV from eight BAs was 58.5 (±31.05) cm/sec. Average post-transfusion MFV in eight BAs was 60.24 (±18.22) cm/sec. This difference was not statistically significant (p=0.88).
Conclusions: Packed red blood cell transfusion did not appear to have a significant effect on cerebral vasospasm as assessed by TCD in patients with aneurysmal SAH. Liberal transfusion protocols may not exacerbate cerebral vasospasm as has been suggested by some authors.
Patient Care: Understanding the risks and benefits of blood transfusion, with particular reference to vasospasm after aneurysmal subarachnoid hemorrhage will improve decision-making for critically ill patients and promote further study into the relationship between blood transfusion and vasospasm.
Learning Objectives: By the conclusion of this session, participants should be able to 1) describe the effects of transfusion on cerebral oxygen delivery, 2) explain how transfusion may exacerbate cerebral vasospasm by altering nitric oxide signalling, and 3) understand that more liberal transfusion may not exacerbate vasospasm and may improve cerebral oxygen delivery.