Detrimental effects of intrahospital transport on cerebral metabolism in patients suffering severe aneurysmal subarachnoid hemorrhage

Abstract

OBJECTIVE Intrahospital transport for CT scans is routinely performed for neurosurgical patients. Particularly in the sedated and mechanically ventilated patient, intracranial hypertension and blood pressure fluctuations that might impair cerebral perfusion are frequently observed during these interventions. This study quantifies the impact of intrahospital patient transport on multimodality monitoring measurements, with a particular focus on cerebral metabolism. METHODS Forty intrahospital transports in 20 consecutive patients suffering severe aneurysmal subarachnoid hemorrhage (SAH) under continuous intracranial pressure (ICP), brain tissue oxygen tension (pbtO2), and cerebral microdialysis monitoring were prospectively included. Changes in multimodality neuromonitoring data during intrahospital transport to the CT scanner and the subsequent 10 hours were evaluated using linear mixed models. Furthermore, the impact of risk factors at transportation, such as cerebral vasospasm, cerebral hypoxia (pbtO2 < 15 mm Hg), metabolic crisis (lactate-pyruvate ratio [LPR] > 40), and transport duration on cerebral metabolism, was analyzed. RESULTS During the transport, the mean ICP significantly increased from 7.1 ± 3.9 mm Hg to 13.5 ± 6.0 mm Hg (p < 0.001). The ICP exceeded 20 mm Hg in 92.5% of patients; pbtO2 showed a parallel rise from 23.1 ± 13.3 mm Hg to 28.5 ± 23.6 mm Hg (p = 0.02) due to an increase in the fraction of inspired oxygen during the transport. Both ICP and pbtO2 returned to baseline values thereafter. Cerebral glycerol significantly increased from 71.0 ± 54.9 µmol/L to 75.3 ± 56.0 µmol/L during the transport (p = 0.01) and remained elevated for the following 9 hours. In contrast, cerebral pyruvate and lactate levels were stable during the transport but showed a significant secondary increase 1–8 hours and 2–9 hours, respectively, thereafter (p < 0.05). However, the LPR remained stable over the entire observation period. Patients with extended transport duration (more than 25 minutes) were found to have significantly higher levels of cerebral pyruvate and lactate as well as lower glutamate concentrations in the posttransport period. CONCLUSIONS Intrahospital transport and horizontal positioning during CT scans induce immediate intracranial hypertension and an increase in cerebral glycerol, suggesting neuronal injury. Afterward, sustained impairment of neuronal metabolism for several hours could be observed, which might increase the risk of secondary ischemic events. Therefore, intrahospital transport for neuroradiological imaging should be strongly reconsidered and only indicated if the expected benefit of imaging results outweighs the risks of transportation.

Cerebral multimodality monitoring in adult neurocritical care patients with acute brain injury: A narrative review

“…In other words, the definitions of secondary brain injuries are limited by the number of available modalities. For example, Lindner et al (2021) defined mitochondrial dysfunction (single modality) as: CMD lactate/pyruvate (L/P)-ratio ≥ 40 + CMD-pyruvate ≥ 70 μmol/L, whereas Khellaf et al defined mitochondrial dysfunction (three modalities) as: CMD L/P-ratio>25 for more than 2 h, ICP <20 mmHg; PbtO 2 <15 mmHg; PRx <0.3; brain extracellular glucose >1 mmol/L (Khellaf et al, 2022).…”

“…For example, Hosmann et al (2022) define indications for cerebral ischemia as CMD L/P-ratio >40 CMD-glycerol >100 μmol/L, CMD-lactate >4 mmol/L, whereas Nyholm et al (2017) defined cerebral ischemia as CMD-L/P ratio >40 and CMD-pyruvate <50 mol/L). For brain tissue hypoxia monitored by PbtO 2 there were in general two definitions used: PbtO 2 <15 mmHg ( Burnol et al, 2021 ; Hosmann et al, 2021 ) or <20 mmHg ( Le Roux et al, 2014 ; Gagnon et al, 2020 ; Sekhon et al, 2020 ; Gouvea Bogossian et al, 2021 ).…”

“…In addition, we discussed clinical outcome in intervention studies. We identified 112 MMM studies, including 11 modalities, over the last 7 years (2015)(2016)(2017)(2018)(2019)(2020)(2021)(2022). Fifty-eight studies (52%) applied only two modalities.…”

Invasive Diagnostic and Therapeutic Management of Cerebral VasoSpasm after Aneurysmal Subarachnoid Hemorrhage (IMCVS)—A Phase 2 Randomized Controlled Trial

“…Patients with CVS at the ICU reflect a highly vulnerable subgroup of SAH patients who are at risk for DCI that may develop when cerebral blood supply decreases below demand. An invasive diagnostic and therapeutic management in patients with critically low cerebral blood supply may lead to varying blood pressure and decreased monitoring compared to the treatment at the ICU over a period of time, which may explain why the otherwise effective treatment of angiographic CVS does not translate into better outcomes [ 19 ].…”

Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage: The Results of Induced Hypertension Only after the IMCVS Trial—A Prospective Cohort Study

“…Additionally, to directly attributable complications, any kind of intrahospital transport for diagnostics and intervention bears the risk of transport-related complications, e.g., drop in blood pressure and lowering of blood supply below demand, resulting in ischemia. Furthermore, Hosmann et al [ 10 ] found detrimental effects of intrahospital transports on cerebral metabolism in patients with SAH, leading to sustained impaired neuronal metabolism for several hours. The authors concluded that any kind of intrahospital transport for neuro-imaging should strongly be reconsidered and only indicated if the expected benefits outweigh the risks.…”