Low Plasma Arginine:Asymmetric Dimethyl Arginine Ratios Predict Mortality After Intracranial Aneurysm Rupture

Background—

Asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthases, predicts mortality in cardiovascular disease and has been linked to cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). In this prospective study, we assessed whether circulating ADMA, arginine:ADMA ratio, and nitrite/nitrate levels were associated with survival and cerebral vasospasm in SAH patients.

Methods—

One hundred and eleven patients were observed day 1 to 15 after SAH, with serial measurements of transcranial Doppler flow velocities (V MCA ) and plasma biomarkers. Clinical status was assessed by the World Federation of Neurosurgical Societies grading scale.

Results—

Overall 30-day mortality was 18%, but differed between patients grouped by low, midrange, and high arginine:ADMA ratio in the first week after SAH. Mortality rates were 14/37, 1/37, and 5/37 in the 3 groups, respectively ( P -logrank=0.0003). Cox regression showed that low versus midrange or high arginine:ADMA was associated with a hazard ratio of 4.1 independent of World Federation of Neurosurgical Societies grade (95% confidence interval, 1.5–10.9; P =0.006). ADMA or arginine:ADMA had no association to V MCA , but there was an inverse relationship between V MCA and nitrite/nitrate levels ( P <0.0001). The NOS3 894G/G genotype was associated with 15% lower V MCA ( P =0.01). ATbG- NOS3 haplotype homozygosity was associated with up to 64% higher nitrite/nitrate levels ( P =0.003).

Conclusions—

This study suggests that plasma arginine:ADMA ratios predict mortality after SAH. Both clinical and physiological measures of changes in cerebral hemodynamics are coupled to the nitric oxide system.

Transcranial Doppler velocimetry in aneurysmal subarachnoid haemorrhage: intra- and interobserver agreement and relation to angiographic vasospasm and mortality

BACKGROUND

Transcranial Doppler measurements of the middle cerebral artery flow velocity are widely used as an indicator of vasospasm after aneurysmal subarachnoid haemorrhage (SAH). We investigated inter- and intraoperator agreement in SAH patients and healthy volunteers using colour-coded transcranial Doppler (TCCD), with the secondary aim of describing prediction of angiographic vasospasm and mortality.

METHODS

Sixty patients and 70 healthy controls were each examined in duplicate by alternating operators. A total of 939 measurements divided on 201 examination sets were conducted by four observers. The Bland-Altman limits of agreement (LoA) were calculated using a variance components analysis. Angiography was performed on clinical indication and survival recorded at 30 days.

RESULTS

Differences between measurements increased with increasing average, and therefore, we analysed log-transformed values. Thus, LoA are given as ratios between measurements. There were no systematic intra- or interobserver differences (bias). The intraobserver LoA was 0.62-1.61 in patients and 0.67-1.50 in controls. However, they were 0.55-1.82 in patients with angiographic vasospasm, whereas in patients without, they were 0.66-1.52. The interobserver LoA was 0.55-1.81 in patients and 0.65-1.55 in controls, while in patients with and without angiographic vasospasm, they were 0.45-2.22 and 0.60-1.67, respectively. Flow velocity measurements day 6-10 were positively associated with 30 day mortality risk (P=0.02, logistic regression).

CONCLUSIONS

TCCD measurement variability is wider in patient measurements than in controls. This discrepancy can largely be explained by a higher degree of error in patients with angiographic vasospasm. Despite the considerable measurement variability in TCCD, values are predictive of outcome in SAH.

Asymmetric dimethylarginine in somatically healthy schizophrenia patients treated with atypical antipsychotics: a case-control study

BACKGROUND

Schizophrenia is associated with increased cardiovascular morbidity and mortality. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of the nitric oxide synthase, and the L-arginine:ADMA ratio are markers of endothelial dysfunction that predict mortality and adverse outcome in a range of cardiovascular disorders. Increased ADMA levels may also lead to increased oxidative stress. We hypothesized that ADMA and the L-arginine:ADMA ratio are increased in somatically healthy schizophrenia patients treated with atypical antipsychotics (AAP), and that the ADMA and the L-arginine: ADMA ratio are positively correlated to measures of oxidative stress.

METHODS

We included 40 schizophrenia patients treated with AAP, but without somatic disease or drug abuse, and 40 healthy controls. Plasma concentrations of ADMA and L-arginine were determined by high-performance liquid chromatography. Data were related to markers of systemic oxidative stress on DNA, RNA and lipids, as well as measures of medication load, duration of disease and current symptomatology.

RESULTS

Plasma ADMA and the L-arginine:ADMA ratio did not differ between schizophrenia patients and controls. Furthermore, ADMA and the L-arginine:ADMA ratio showed no correlations with oxidative stress markers, medication load, or Positive and Negative Syndrome Scale scores.

CONCLUSIONS

Schizophrenia and treatment with AAP was not associated with increased levels of plasma ADMA or the L-arginine:ADMA ratio. Furthermore, plasma levels of ADMA were not associated with levels of systemic oxidative stress in vivo.

Association of the NOS3 intron-4 VNTR polymorphism with aneurysmal subarachnoid hemorrhage

OBJECT

The nitric oxide system has been linked to the pathogenesis of aneurysmal subarachnoid hemorrhage (SAH). The authors performed a case-control study to investigate the association between SAH and common genetic variants within the endothelial nitric oxide synthase gene (NOS3).

METHODS

Three hundred thirty-three Caucasian SAH patients and 498 controls were genotyped for the -922A > G (rs 1800779), -786T > C (rs2070744), and 894G > T (rs1799983) single nucleotide polymorphisms and the intron-4 27-bp variable number of tandem repeats polymorphism (27-bp-VNTR).

RESULTS

The b/b (5 repeats) genotype of the 27-bp-VNTR was overrepresented in cases (77%) versus controls (69%) (p = 0.02). In male patients the b/b genotype was found in 85% compared with 67% in male controls, whereas in women, the frequencies were 73% and 72%, respectively. This corresponds to an odds ratio of 2.8 (95% CI 1.5-5.6, p = 0.0005) for SAH in men with the b/b genotype versus men with a/b or a/a. In women, no such association was found (OR 1.1, 95% CI 0.7-1.6, p = 0.76). Stepwise logistic regression including arterial hypertension, smoking, sex, and age with interactions yielded similar effect estimates of the 27-bp-VNTR. Haplotype analysis revealed that no single haplotype containing the b-allele was responsible for the observed genotype effect.

CONCLUSIONS

The authors' results suggest that the NOS3 27-bp-VNTR b/b genotype independent of other risk factors act in concert with male sex to substantially increase risk of SAH. This effect is not mediated by any single NOS3 haplotype.

ADRB2 gly16gly Genotype, Cardiac Output, and Cerebral Oxygenation in Patients Undergoing Anesthesia for Abdominal Aortic Aneurysm Surgery

BACKGROUND

Gly16arg polymorphism of the adrenergic β2-receptor is associated with the elevated cardiac output (Q) in healthy gly16-homozygotic subjects. We questioned whether this polymorphism also affects Q and regional cerebral oxygen saturation (SCO2) during anesthesia in vascular surgical patients.

METHODS

One hundred sixty-eight patients (age 71 ± 6 years) admitted for elective surgery were included. Cardiovascular variables were determined before and during anesthesia by intravascular pulse contour analysis (Nexfin) and SCO2 by cerebral oximetry (INVOS 5100C). Genotyping was performed with the TaqMan assay.

RESULTS

Before anesthesia, Q and SCO2 were 4.7 ± 1.2 L/min and 66% ± 8%, respectively, and linearly correlated (r = 0.35, P < .0001). In patients with the gly16gly genotype baseline, Q was approximately 0.4 L/min greater than in arg16 carriers (CI95: 0.0-0.8, Pt test = .03), but during anesthesia, the difference was 0.3 L/min (Pmixed-model = .07). Post hoc analysis revealed the change in SCO2 from baseline to the induction of anesthesia to be on average 2% greater in gly16gly homozygotes than in arg16 patients when adjusted for the change in Q (P = .03; CI95: 0.2-4.0%).

CONCLUSIONS

This study suggests that the β2-adrenoceptor gly16gly genotype is associated with the elevated resting Q. An interesting trend to greater frontal lobe oxygenation at induction of anesthesia in patients with gly16gly genotype was found, but because of insufficient sample size and lack of PCO2 control throughout the measurements, the presented data may only serve as the hypothesis generating for future studies. The confidence limits indicate that the magnitude of the effects may range from clinically insignificant to potentially important.