Variation in Severity-Adjusted Resource use and Outcome for Neurosurgical Emergencies in the Intensive Care Unit

Abstract

Background: The correlation between the standardized resource use ratio (SRUR) and standardized hospital mortality ratio (SMR) for neurosurgical emergencies is not known. We studied SRUR and SMR and the factors affecting these in patients with traumatic brain injury (TBI), nontraumatic intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH).

Methods: We extracted data of patients treated in six university hospitals in three countries (2015-2017). Resource use was measured as SRUR based on purchasing power parity-adjusted direct costs and either intensive care unit (ICU) length of stay (costSRUR_{length of stay}) or daily Therapeutic Intervention Scoring System scores (costSRUR_{Therapeutic Intervention Scoring System}). Five a priori defined variables reflecting differences in structure and organization between the ICUs were used as explanatory variables in bivariable models, separately for the included neurosurgical diseases.

Results: Out of 28,363 emergency patients treated in six ICUs, 6,162 patients (22%) were admitted with a neurosurgical emergency (41% nontraumatic ICH, 23% SAH, 13% multitrauma TBI, and 23% isolated TBI). The mean costs for neurosurgical admissions were higher than for nonneurosurgical admissions, and the neurosurgical admissions corresponded to 23.6-26.0% of all direct costs related to ICU emergency admissions. A higher physician-to-bed ratio was associated with lower SMRs in the nonneurosurgical admissions but not in the neurosurgical admissions. In patients with nontraumatic ICH, lower costSRURs were associated with higher SMRs. In the bivariable models, independent organization of an ICU was associated with lower costSRURs in patients with nontraumatic ICH and isolated/multitrauma TBI but with higher SMRs in patients with nontraumatic ICH. A higher physician-to-bed ratio was associated with higher costSRURs for patients with SAH. Larger units had higher SMRs for patients with nontraumatic ICH and isolated TBI. None of the ICU-related factors were associated with costSRURs in nonneurosurgical emergency admissions.

Conclusions: Neurosurgical emergencies constitute a major proportion of all emergency ICU admissions. A lower SRUR was associated with higher SMR in patients with nontraumatic ICH but not for the other diagnoses. Different organizational and structural factors seemed to affect resource use for the neurosurgical patients compared with nonneurosurgical patients. This emphasizes the importance of case-mix adjustment when benchmarking resource use and outcomes.

Keywords: Costs; Critical care; Intensive care; Intracerebral hemorrhage; Subarachnoid hemorrhage; Traumatic brain injury.

Fig. 1

Flow chart showing study population and exclusions. ICU, intensive care unit, GCS, Glasgow Coma Scale, TISS, Therapeutic Intervention Scoring System

Fig. 2

Differences in standardized mortality ratio (SMR) and standardized resource use ratios (costSRUR_TISS, costSRUR_LOS) between the neurosurgical diagnoses. Box plots show the median, the first and third quartiles, and whiskers defined by 1.5 times the interquartile range. Values are reported in eTable 4. costSRUR_LOS, xxx, costSRUR_TISS, xxx, SAH, subarachnoid hemorrhage, TBI, traumatic brain injury

Fig. 3

Standardized resource use ratios (costSRUR_LOS, costSRUR_TISS) in relation to the standardized mortality ratio (SMR) for all other nonneurosurgical patients and the included neurosurgical diagnoses. Filled circles: an ICU, circle size is proportional to the number of ICU admissions. Solid lines: Gaussian linear regression lines. Dashed lines: their 95% confidence intervals (slope estimates in eTable 7). Dotted horizontal and vertical lines: costSRUR = 1 and SMR = 1. A significant association between SMR and costSRUR_LOS/costSRUR_TISS was found in the combined neurosurgical diagnoses group (bottom right) and in patients with nontraumatic ICH (upper mid). costSRUR_LOS, xxx, costSRUR_TISS, xxx, ICH, intracranial hemorrhage, ICU, intensive care unit, SAH, subarachnoid hemorrhage, TBI, traumatic brain injury

Fig. 4

Bivariable analyses of variables associated with standardized resource utilization ratios (costSRUR_TISS, costSRUR_LOS) and standardized mortality ratio (SMR). Values are reported in eTable 8. costSRUR_LOS, xxx, costSRUR_TISS, xxx, FTE, full-time equivalent, ICH, intracranial hemorrhage, ICU, intensive care unit, SAH, subarachnoid hemorrhage, SAPS-II, Simplified Acute Physiology Score II, TBI, traumatic brain injury