Higher serum lactate dehydrogenase level predicts poor outcome of aneurysmal subarachnoid hemorrhage after microsurgery

We explored the clinical signicance of serum LDH level in aSAH patients after microsurgical clipping in our single institution, to test the hypothesis that higher serum LDH level predicts the outcome of aSAH patients at 3 months. A total of 2054 aSAH patients were collected, and 874 patients treated by microsurgical clipping were enrolled. And the serum LDH level within 24 hours after aSAH were recorded. The median serum LDH level (U/L) in the good outcome group (180.096±50.237) was obviously lower than that in the poor outcome group (227.554±83.002)(p=0.000). The area under the receiver operating characteristic (ROC) curve was 0.702(95% condence interval [CI], 0.650 -0.754; p=0.000). The optimal cutoff value for serum LDH level as a predictor for 3-month poor outcome (mRS>2) was determined as 201.5U/L in the ROC curve. Our nding showed that that higher serum LDH level correlated with Hunt & Hess grade, Fisher grade and neurological functional outcome, and predicted the outcome of aSAH at 3 months, which was involved in the related mechanisms of early brain injury and showed its great clinical signicance in aSAH patients. clinical condition of aSAH patients and their Hunt& Hess grade 22 . Similarly, the amount of RBC in cerebra cisterna, sulcus and/or ventricle correlated to Fisher grade. Frontera JA found that early brain ischaemia injury associated with worse Hunt-Hess grade, which is related to poor acute neurological status and correlated with worse functional outcomes after SAH 23 . Claassen J’s study showed that SAH completely lling cistern or ssure and intraventricular hemorrhage (IVH) on CT were risk factors for delayed ischemic neurological decit (DIND) 24 , which correlated with the poor outcomes after SAH. However, few reports have explored the relation between serum LDH level and the extent of cerebral tissue injury in aSAH patients. Here, we explored the clinical signicance of serum LDH in aSAH patients treated by microsurgical clipping in our single institution, to test the hypothesis that higher serum LDH level, which could correlate with Hunt & Hess grade and Fisher grade, and predicted the outcome of aSAH patients at 3 months.

Higher serum lactate dehydrogenase level predicts poor outcome of aneurysmal subarachnoid hemorrhage after microsurgery Shu contributed to the poor prognosis for aSAH [19][20][21] . However, few reports have explored the clinical signi cance of serum LDH level in patients with aneurysmal subaracrhnoid hemorrhage(aSAH), and the role of LDH in aSAH were not fully established. It was conceivable that there were at least the following two factors contributed to higher serum LDH level in aSAH patients: (1)LDH originated from apoptotic/necrotic/damaged neuron or glial cells.
(2) LDH from lytic red blood cells(RBC) after being released into cerebrospinal uid(CSF). As Lu Y reported, the amount of apoptotic/necrotic/damaged cells positively correlated to clinical condition of aSAH patients and their Hunt& Hess grade 22 . Similarly, the amount of RBC in cerebra cisterna, sulcus and/or ventricle correlated to Fisher grade. Frontera JA found that early brain ischaemia injury associated with worse Hunt-Hess grade, which is related to poor acute neurological status and correlated with worse functional outcomes after SAH 23 . Claassen J's study showed that SAH completely lling cistern or ssure and intraventricular hemorrhage (IVH) on CT were risk factors for delayed ischemic neurological de cit (DIND) 24 , which correlated with the poor outcomes after SAH. However, few reports have explored the relation between serum LDH level and the extent of cerebral tissue injury in aSAH patients. Here, we explored the clinical signi cance of serum LDH in aSAH patients treated by microsurgical clipping in our single institution, to test the hypothesis that higher serum LDH level, which could correlate with Hunt & Hess grade and Fisher grade, and predicted the outcome of aSAH patients at 3 months.

Methods
Inclusion and exclusion criteria.Patients were enrolled in the study based on the following criteria: 1) Diagnosis of subarachnoid hemorrhage was con rmed by Computed Tomography (CT). Computerized tomography angiography (CTA) or digital subtraction angiography (DSA) was used to con rm the presence of the intracranial aneurysm. 2) All aneurysms treated by microsurgical clipping, and CTA and/or DSA were performed postoperatively. The exclusion criteria were: 1) aSAH was detected over 1 day; 2) The patients with the other cerebrovascular diseases (such as cerebral arteriovenous malformations, intracranial arteriovenous stula, and moyamoya syndrome/disease) and intracranial tumors.
3) The patients with myocardial infarction, hepatitis, malignant tumor, pulmonary infarction, leukemia, hemolytic anemia, kidney disease or progressive muscular atrophy, etc. The aSAH patients in our institution between 2010 and 2018 were collected. Age, sex, history of smoking, drinking, medical history(hypertension diabetes coronary heart disease cerebral stroke), Hunt-Hess and Fisher grade, aneurysm location, delayed ischemic neurological de cit (DIND), intracranial infection, hydrocephalus, pneumonia and the serum LDH level within 24 hours after aSAH were recorded.
Treatment de nition.After being con rmed, ruptured intracranial aneurysms were treated with microsurgical clipping. After surgical management, the patients were treated according to the current guidelines for aneurismal subarachnoid hemorrhage 25 , including prevention or re-versal of the cerebral arterial narrowing, improving cerebral blood ow, neurotrophic treatment, stress ulcer prevention and nutritional support.
Follow-up visit and de nition of outcome. Postoperative complications were evaluated with CT scanning within 24 hours after surgical treatment. The neurological outcome was assessed at the 3-month follow-up and classi ed according to the modi ed Rankin Scale (mRS) score: a good clinical outcome was de ned as mRS 0-2, a poor outcome as mRS 3-6. We divided the functional outcome into four levels according to mRS namely no symptoms (mRS 0), no signi cant to slight disability (mRS 1-2), moderate to serious disability (mRS 3-4) and severe disability to death (mRS 5-6). To de ne the relation between serum LDH level and clinical outcome of aSAH patients, we investigated the whether the serum LDH level was associated with Hunt-Hess grade, Fisher grade and the upper four functional outcome.
Standard protocol approvals and patient consents.All procedures performed in this retrospective study involving human participants were on the basis of the 1964 Helsinki declaration and approved by the ethics committee of First A liated Hospital of Fujian Medical University. Informed consent was obtained from all individual participants enrolled in the study.
Statistical analysis.All the statistical analyses were performed utilizing SPSS for windows version 25.0 (IBM Corp., Armonk, NY, USA). One-way analysis of variance (ANOVA) or Student's t test was used to determine the signi cance of differences in continuous data. Chi-squared test (χ2 test) or Fisher's exact test was used to determined the signi cance of differences in qualitative data. Multivariable analysis logistic regression model included all variables whose p value was less than 0.10 in univariate analysis. For inclusion in the multivariable analysis model, age was divided into "less than 65 years" and "more than 65 years" 26 , Hunt-Hess grade divided into "low grade (Grade -)" and "high grade (Grade -V)", Fisher grade divided into "low grade (Grade 1,2,3)" and "high grade (Grade 4)" , serum LDH level as "≤ optimal cutoff value " and " optimal cutoff value ". P<0.05 was deemed statistically signi cant. Receiver operating curve (ROC) (MedCalc for windows version 15.2.2 , Mariakerke, Belgium)was generated to analyze the speci city, sensitivity of serum LDH level for mRS. Propensity-score matching (PSM) analysis was performed to remove imbalances in basic clinical characteristics between good outcome and poor outcome groups, which was also performed between pneumonia and non-pneumonia groups. Conditional probability was estimated with the logistic regression model. The good outcome and poor outcome groups were matched at a ratio of 1:1 using the nearest neighboring matching algorithm.

Results
A total of 2054 aSAH patients in our institution between 2010 and 2018 were collected, and 874 patients treated by microsurgical clipping were enrolled based on the upper criteria ( gure 1). Incidence of poor outcome following aSAH was 13.8%( 121/874). Basic clinical characteristics of patients with aneurysmsal subarachnoid hemorrhage were shown on table 1 and 2. The median serum LDH level(U/L) in the good outcome group (180.096±50.237) was obviously lower than that in the poor outcome group (227.554±83.002)(p=0.000). The receiver operating characteristic (ROC) curve of serum LDH level for poor outcome of aSAH patients at the 3-month follow-up is shown in Figure 2. The area under the ROC curve (AUC) was 0.702(95% con dence interval [CI], 0.650 -0.754; p=0.000). The optimal cutoff value for serum LDH level as a predictor for 3-month poor outcome (mRS>2) was determined as 201.5U/L in the ROC curve. On this level, the sensitivity was 59.5%, the speci city was 76.4%.
In order to analyze the predictors for poor outcome of aSAH patients, the variables signi cance level at p < 0.10 including age hypertension diabetes Hunt-Hess Fisher anterior communicating artery aneurysm, basilar artery aneurysm, delay ischemic neurological de cit(DIND), hydrocephalus, pneumonia, serum LDH(>201.5U/L) were included in the univariate analysis.

Discussion
Our ndings showed that there was obvious trend that serum LDH level will increase concomitantly with increasing Hunt & Hess and Fisher grade. And it was indicated that Hunt-Hess grade Fisher grade, delay ischemic neurological de cit, pneumonia, higher serum LDH level could predicted and contributed to the poor outcome of aSAH patients at 3 months. The optimal cutoff value for serum LDH level as a predictor for the 3-month poor outcome (mRS>2) was determined as 201.5U/L. It was also shown that serum LDH level correlated with neurological functional outcome. There was obvious trend that serum LDH level would increase with deterioration of neurological function. After PSM, Serum LDH(>201.5U/L) was still considered as an independent risk factor of poor outcome.
It was demonstrated that subarachnoid clots in sulci/ ssures would induce spreading depolarizations and acute cerebral infarction of adjacent cortex 27 , which were major players in the mechanism of early brain injury after SAH 28 and contributed to the clinical condition of aSAH patients. Frontera JA's study 23 indicated that the early ischemic brain injury was elated to worse Hunt-Hess grade, Glasgow Coma Scale(GCS) score, higher rates of death, severe disability/death (mRS 4-6) at the 3-month follow-up. And the increase in ischemic lesion volume was associated with the increase on the Hunt-Hess grade and the 3-month mRS 29 . In other words, Hunt-Hess grade correlates with the degree of early ischemic brain injury to some extent.
It was known that neuronal apoptosis and necrosis was present 24 h after SAH 27,30 , which could result in cytolysis and cell membrane destruction. Then LDH will be released into the blood from damaged or dead cells and resulting in serum LDH increase 4 . Therefore, serum LDH level re ects the severity of brain tissue injury. Yu W's study 14 demonstrated that serum LDH activities were associated with the infarct volume and degree of middle cerebral artery occlusion in a dose-dependent manner. Study showed that LDH quanti cation were used to predict the neuronal damage 15,16 , and inhibition of LDH release might reduce neuronal apoptosis 14 . Rao CJ's report showed that a signi cant rise of serum LDH level was a predictor of severe brain damage and the poor prognosis of traumatic brain injury 17 . In addition, Engelke S's study indicated that LDH was also signi cantly correlated with subsequent seizures, hydrocephalus and the adverse long-term outcome of neonatal intracranial hemorrhage 18 .
It was suggested that serum LDH level were correlated with the prognosis of adult T-cell leukemia-lymphoma 6 , prostate cancer 7 , acute myeloid leukemia 8 , melanoma 9 , neuroblastoma 10 , glioblastoma multiforme 11 , acute encephalopathy 12 and mycoplasma pneumoniae pneumonia 13 .To our best knowledge, there were few reports investigating the relationship between LDH and aSAH. It was demonstrated that regional cerebral blood ow and arteriovenous difference of oxygen would be reduced due to the primary injury of aSAH 31 , and cerebral ischemia would caused an anaerobic shift of metabolism with lactic acidosis and upregulation of serum LDH level 32 . It was reported that there was signi cant correlation between serum LDH and lactic acid levels, and both of them re ected the degree of tissue damage 31,33 . Shimoda M's report 34 indicated that World Federation of Neurosurgical Societies (WFNS) Grade III-V showed signi cantly higher lactic acidosis than Grade I-II.
Therefore, we deduced that Hunt & Hess grade IV-V also showed higher serum LDH level than I-III. There was an obvious trend that serum LDH level will increase concomitantly with increasing Hunt & Hess grade in our study. Thus, we deduced that serum LDH level exactly did correlate with Hunt & Hess grade, which re ects the degree of early brain injury and clinical condition of aSAH patients.
The greater the amount of blood within subarachnoid space, the higher Fisher grade, which correlated with poor outcome of aSAH 35,36 . After cerebral aneurysm rupture, destruction of blood brain barrier occurred and RBC was released into the subarachnoid space from artery as a consequence of cerebral aneurysm rupture, the RBC in cerebrospinal uid(CSF) would broke down 36 , LDH from lytic RBC was absorbed into blood after being released into CSF 17 . The levels of serum LDH would increase. Our ndings showed that there was also an obvious trend that serum LDH level will increase concomitantly with increasing Fisher grade. Thus, higher serum LDH level was associated with higher Fisher grade, which was closely related to poor outcome of aSAH consistent with the previous reports 35,37,38 .
Our study has some limitations. First, LDH exists in all important human organs, and it lacks speci city to central nervous system. The LDH from CSF in our patients was not measured and collected, the serum LDH level does not re ect the true level in the brain tissue directly. Second, the imaging data were not available to con rm the relationship between serum LDH level and degree brain tissue damage, which can not be clari ed intuitively. Third, the serum LDH level(>201.5U/L) in a proportion of patients was within normal range, and it can not be fully explained why these patients suffered from poor prognosis, the detailed mechanism needs further exploration.

Conclusions
Our nding showed that that higher serum LDH level correlated with Hunt & Hess grade, Fisher grade and neurological functional outcome, and predicted the outcome of aSAH patients at 3 months, which was involved in the related mechanisms of early brain injury and showed its great clinical signi cance in aSAH patients.

Declarations
Data availability