Table 3.

Clinical studies utilizing the Transient Hyperemic Response Test (THRT) in subarachnoid hemorrhage patients.

References	Citation	Study size	SAH grade	Critical observations
Smielewski et al., 1995	(126)	52	WFNS 1-5	Negative THRT result (<1.09) correlated with worse WFNS grade and GOS.
Lam et al., 2000	(127)	20	WFNS 1-4	6/20 patients displayed a negative THRT result (<1.09) 1 day after surgery: 5 developed DIDs.6/14 remaining patients had a negative THRT result 3–7 days post-surgery: none developed DIDs.
Rätsep and Asser, 2001	(128)	55	WFNS 1-5	A negative THRT result (<1.10) was found in 22–35% of assessments over 0–19 days post-SAH ictus.Negative THRT results peaked at 0–3 and 7–14 days. Negative THRT associated with unfavorable GOS (1-2).
Rätsep et al., 2002	(129)	50	WFNS 1-5	Negative THRT results (<1.10) were found in 33% of assessments over 0–18 days post-SAH ictus. Negative THRT results peaked at 0–3 and 7–14 days post-SAH. Negative THRT result associated with poor initial
				WFNS grade (>2), vasospasm and impaired consciousness.
Al-Jehani et al., 2018	(130)	15	Hunt-Hess 1-5	7/15 patients had a negative THRT result (<1.09). A negative THRT result predicts the development of symptomatic vasospasm (5/6).
Rynkowski et al., 2019	(131)	40	Not Defined	19/40 patients had a negative THRT result (<1.09). Negative THRT result correlated with Hunt-Hess score ≥4, higher APACHE II scores (12 vs. 3.5) and unfavorable outcome (mRS ≥4 at 6 months).

These studies included SAH patients only. In Rynkowski et al., Hunt-Hess scores were obtained for 11/40 patients. APACHE II, Acute Physiology And Chronic Health Evaluation II; DIDs, Delayed ischemic deficits; GOS, Glasgow outcome score; mRS, Modified Rankin score; SAH, Subarachnoid hemorrhage; THRT, Transient hyperemic response test; WFNS, World Federation of Neurosurgical Societies scale.