Predicting Outcomes During Cerebral Aneurysm Coiling
Identification of modifiable risk factors associated with complications as well as the development of predictive models for outcomes are significant milestones in the path to accountable care. Especially in patients amenable to both clipping and coiling, individualized complication prediction can tailor decision, making for the appropriate intervention. The NIS provides diverse data representative of the national experience, and is not restricted by the rigorous inclusion criteria of RCTs for SAH, allowing the generalization of its conclusions. In addition, in the area of unruptured aneurysms, where RCTs are lacking, it can assist in the decision making for individual patients. Previous studies of the NIS have focused on comparing the morbidity and mortality of the two interventions, or the effect of volume on outcomes, avoiding any analysis of modifiable patient level risk factors.
History of stroke, CRF, and CHF was associated with higher mortality in all patients. Coagulopathy and increasing age were, as expected, preferentially associated with worse outcomes in SAH. The paradoxically protective effect of obesity and CAD might be associated with the potentially beneficial role of statins in the survival of patients with SAH. Alternatively, it might be attributed to the potential random effect of multiple comparisons. The observed inpatient mortality (0.3% for unruptured aneurysms and 13.8% for SAH) is slightly less than what is observed in the literature. Several prior studies on NIS have focused on the effect of increasing age on higher mortality.
Morbidity immediately related to the surgical intervention (postoperative stroke and treated hydrocephalus) was also investigated. Patients with SAH had a higher incidence of periprocedural stroke. It was most commonly seen in patients with a prior history of ischemic stroke, probably due to their higher atherosclerotic burden. Treated hydrocephalus was, as expected, much higher in patients with SAH, given the high ventriculostomy rate. Patients with a heavier atherosclerotic burden (with prior ischemic stroke or cardiac disease) or limited reserve because of older age, appeared to have an increased rate of severe hydrocephalus. A potential explanation is that these patients have a higher Hunt and Hess grade at presentation and more complex operations, increasing the risk of hydrocephalus. The observed protective effect of hypercholesterolemia could again be associated with a beneficial effect of the use of statins on this outcome.
The observed incidence of general medical morbidity measures was similar in all patients undergoing CACo, except for the higher rate of DVT and ARF in patients with SAH. The lack of anticoagulation and prolonged immobilization in this group of patients can explain the higher incidence of DVT. Increasing age and previous heart disease were associated with cardiac complications whereas heavier atherosclerotic burden (heart disease, PVD) and coagulopathy were common factors associated with ARF. Patients who underwent longer immobilization (obesity, prior stroke) had a higher incidence of DVT and PE. These rates are in accordance with what has been previously reported.
Finally, we investigated length of hospitalization and disposition, which have a central role in the developing model of accountable care. Length of stay of more than 14 days in SAH patients, or more than 2 days in patients with unruptured aneurysms, was associated with increasing age, patient immobility (obesity and prior stroke), general medical comorbidities (CHF, CAD, and diabetes), and coagulopathy. Unfavorable discharge was, as expected, more commonly seen in SAH patients and was associated with increasing age, general medical comorbidities, and other factors (prior stroke, coagulopathy) that also contributed to prolonged hospitalizations. The effect of increasing age in unfavorable discharge has also been encountered in prior studies. Although the rate of unfavorable discharge in patients with unruptured aneurysms might appear high (5.7%), it can be placed in context if the rates of neurologic and other complications, which can result in extended post-acute care, are added.
The proposed predictive model for all outcomes was validated and demonstrated moderate accuracy and discrimination. It may provide a useful tool for patient counseling and informed decision making in the preoperative evaluation of patients undergoing CACo, especially in patients suitable for both interventions. This model can be further refined and validated in prospective studies of the US population. If the risk of morbidity and mortality is predicted to be unacceptably high for coiling, after optimizing any modifiable risk factors, alternative options should be sought after more aggressively (clipping, observation), if appropriate.
The present study has some limitations common to administrative databases. Indication bias and residual confounding could account for some of the observed associations. In addition, several coding inaccuracies can affect our estimates, as in other studies involving the NIS. However, coding for SAH has shown nearly perfect association with medical record review. The NIS during the years studied did not include hospitals from all states. However, the hospitals included were still diverse with respect to size, region, and academic status, supporting the generalizability of our findings. The NIS does not provide any clinical information on the structure, size, or location of the aneurysms, which are important factors to be considered in cerebrovascular neurosurgery. Additionally, we were lacking post-hospitalization and long term data on these patients, as well as disease severity in patients presenting with SAH.
There is also a potential bias in the patient level risk factors selected to be investigated. Further, there is a bias in the assignment of the length of prolonged hospitalization (more than 14 and 2 days for rupture and unruptured aneurysms, respectively). However, these time limits were decided based on the most common values presented in the literature, and are only serving the purpose of creating a predictive model. Finally, the retrospective nature of the study introduces a selection bias that can affect the outcomes of coiling.
Discussion
Identification of modifiable risk factors associated with complications as well as the development of predictive models for outcomes are significant milestones in the path to accountable care. Especially in patients amenable to both clipping and coiling, individualized complication prediction can tailor decision, making for the appropriate intervention. The NIS provides diverse data representative of the national experience, and is not restricted by the rigorous inclusion criteria of RCTs for SAH, allowing the generalization of its conclusions. In addition, in the area of unruptured aneurysms, where RCTs are lacking, it can assist in the decision making for individual patients. Previous studies of the NIS have focused on comparing the morbidity and mortality of the two interventions, or the effect of volume on outcomes, avoiding any analysis of modifiable patient level risk factors.
History of stroke, CRF, and CHF was associated with higher mortality in all patients. Coagulopathy and increasing age were, as expected, preferentially associated with worse outcomes in SAH. The paradoxically protective effect of obesity and CAD might be associated with the potentially beneficial role of statins in the survival of patients with SAH. Alternatively, it might be attributed to the potential random effect of multiple comparisons. The observed inpatient mortality (0.3% for unruptured aneurysms and 13.8% for SAH) is slightly less than what is observed in the literature. Several prior studies on NIS have focused on the effect of increasing age on higher mortality.
Morbidity immediately related to the surgical intervention (postoperative stroke and treated hydrocephalus) was also investigated. Patients with SAH had a higher incidence of periprocedural stroke. It was most commonly seen in patients with a prior history of ischemic stroke, probably due to their higher atherosclerotic burden. Treated hydrocephalus was, as expected, much higher in patients with SAH, given the high ventriculostomy rate. Patients with a heavier atherosclerotic burden (with prior ischemic stroke or cardiac disease) or limited reserve because of older age, appeared to have an increased rate of severe hydrocephalus. A potential explanation is that these patients have a higher Hunt and Hess grade at presentation and more complex operations, increasing the risk of hydrocephalus. The observed protective effect of hypercholesterolemia could again be associated with a beneficial effect of the use of statins on this outcome.
The observed incidence of general medical morbidity measures was similar in all patients undergoing CACo, except for the higher rate of DVT and ARF in patients with SAH. The lack of anticoagulation and prolonged immobilization in this group of patients can explain the higher incidence of DVT. Increasing age and previous heart disease were associated with cardiac complications whereas heavier atherosclerotic burden (heart disease, PVD) and coagulopathy were common factors associated with ARF. Patients who underwent longer immobilization (obesity, prior stroke) had a higher incidence of DVT and PE. These rates are in accordance with what has been previously reported.
Finally, we investigated length of hospitalization and disposition, which have a central role in the developing model of accountable care. Length of stay of more than 14 days in SAH patients, or more than 2 days in patients with unruptured aneurysms, was associated with increasing age, patient immobility (obesity and prior stroke), general medical comorbidities (CHF, CAD, and diabetes), and coagulopathy. Unfavorable discharge was, as expected, more commonly seen in SAH patients and was associated with increasing age, general medical comorbidities, and other factors (prior stroke, coagulopathy) that also contributed to prolonged hospitalizations. The effect of increasing age in unfavorable discharge has also been encountered in prior studies. Although the rate of unfavorable discharge in patients with unruptured aneurysms might appear high (5.7%), it can be placed in context if the rates of neurologic and other complications, which can result in extended post-acute care, are added.
The proposed predictive model for all outcomes was validated and demonstrated moderate accuracy and discrimination. It may provide a useful tool for patient counseling and informed decision making in the preoperative evaluation of patients undergoing CACo, especially in patients suitable for both interventions. This model can be further refined and validated in prospective studies of the US population. If the risk of morbidity and mortality is predicted to be unacceptably high for coiling, after optimizing any modifiable risk factors, alternative options should be sought after more aggressively (clipping, observation), if appropriate.
The present study has some limitations common to administrative databases. Indication bias and residual confounding could account for some of the observed associations. In addition, several coding inaccuracies can affect our estimates, as in other studies involving the NIS. However, coding for SAH has shown nearly perfect association with medical record review. The NIS during the years studied did not include hospitals from all states. However, the hospitals included were still diverse with respect to size, region, and academic status, supporting the generalizability of our findings. The NIS does not provide any clinical information on the structure, size, or location of the aneurysms, which are important factors to be considered in cerebrovascular neurosurgery. Additionally, we were lacking post-hospitalization and long term data on these patients, as well as disease severity in patients presenting with SAH.
There is also a potential bias in the patient level risk factors selected to be investigated. Further, there is a bias in the assignment of the length of prolonged hospitalization (more than 14 and 2 days for rupture and unruptured aneurysms, respectively). However, these time limits were decided based on the most common values presented in the literature, and are only serving the purpose of creating a predictive model. Finally, the retrospective nature of the study introduces a selection bias that can affect the outcomes of coiling.