the study by zhu and colleagues , of zhejiang university in china , in the previous issue of critical care is of particular interest because they report that in a population of 303 patients with aneurysmal subarachnoid hemorrhage ( sah ) , elevated serum copeptin levels correlated not only with poor outcomes and higher mortality but , more importantly , with vasospasm during the subacute period . a growing understanding of the pathophysiology of aneurysmal sah has prompted efforts to identify serum markers that can predict outcomes in these patients . since the most important treatable determinant of poor outcome after aneurysmal sah is the delayed neurological deterioration observed 4 to 14 days after sah ( previously identified as ' vasospasm '   but now preferentially labeled ' delayed cerebral injury ' or ' delayed cerebral ischemia ' ) , several investigators have attempted to identify serum markers that can predict vasospasm in particular and poor functional outcome in general . for instance , the recognition of the important role of an inflammatory injury after aneurysmal sah   led to an exploration of the predictive value of inflammatory markers . recently , juvela and colleagues , of the university of helsinki in finland , reported that elevated serum levels of c - reactive protein ( an acute - phase inflammatory marker ) are predictive of poor outcome at 3 months after aneurysmal sah but not of delayed cerebral ischemia or infarction ( ' vasospasm ' ) . similarly , the recognition of the adverse changes initiated by the contact of blood with the extravascular matrix , which cause impaired coagulation and fibrinolysis , led to a prior exploration by the same group of the predictive value of elevated serum d - dimer levels . in 2006 , juvela and siironen   reported that elevated serum d - dimer levels are predictive of poor outcome at 3 months after aneurysmal sah but , again , not of delayed cerebral ischemia or infarction ( ' vasospasm ' ) . in the study by zhu and colleagues , elevated serum copeptin levels were predictive of vasospasm as well as poor outcome . under stress , the hypothalamic - pituitary axis produces stress hormones such as corticotropin - releasing homone and the nonapeptide arginine vasospressin ( avp ) . among the many effects of avp are water retention in the kidneys and efforts to measure serum levels of avp in a clinical setting , however , have been limited by the fact that it is unstable at room temperature and is cleared rapidly from plasma . the 164-amino acid precursor peptide of avp , pre - provasopresssin , is broken down into three peptides : avp , neurophysin ii , and copeptin . since the larger copeptin is produced in an equimolar ratio with avp and is easier to measure in serum , it can be a surrogate marker for avp . elevated copeptin levels have been correlated with poor outcomes in ischemic stroke , intraparenchymal hemorrhage , and brain trauma as well as sepsis , pneumonia , and myocardial infarction . in their retrospective study , zhu and colleagues extend this work on copeptin to aneurysmal sah and demonstrate convincingly that elevated serum copeptin levels correlate with vasospasm , inpatient mortality , mortality at 1 year , and poor functional outcome at 1 year . vasospasm was confirmed by computed tomography angiography and catheter angiography in all cases . the epidemiological profile and outcomes of the 303 study patients - 10.6% inpatient mortality , 13.9% 1-year mortality , 29.7% 1-year poor outcomes , and 43.2% incidence of vasospasm - are similar to those of patients in larger series . in this study , world federation of neurological surgeons ( wfns ) grade , modified fisher grade , and copeptin levels ( but not aneurysm size , vasospasm , clot thickness , or ischemia by computed tomography ) were associated with increased mortality and poor outcomes by multivariate analysis . the predictive value of copeptin was similar to that of the wfns score in terms of 1-year mortality but was lower than that of the wfns score in terms of vasospasm . it is somewhat disappointing that , in a combined logistic - regression analysis , copeptin did not improve upon the area under the curve of the wfns score in a statistically significant fashion . nevertheless , the potential role of serum copeptin levels in the management of patients with aneurysmal sah is promising and should be explored further . avp : arginine vasospressin ; sah : subarachnoid hemorrhage ; wfns : world federation of neurological surgeons .
copeptin is a peptide derived from pre - provasospression along with arginine vasospressin . in the setting of aneurysmal subarachnoid hemorrhage ( sah ) , elevated serum copeptin levels 
 correlate with vasospasm , inpatient mortality , mortality at 1 year , and poor functional outcome at 1 year . 
 the potential role of serum copeptin levels in the management of patients with aneurysmal sah is promising and should be explored further .