Transcranial doppler assessment of cerebral perfusion in critically ill septic patients: a pilot study

Charalampos Pierrakos 0 1 Aurlie Antoine 0 1 Dimitrios Velissaris 1 2 Isabelle Michaux 0 1 Pierre Bulpa 0 1 Patrick Evrard 0 1 Michel Ossemann 1 3 Alain Dive 0 1 0 Department of Intensive Care, Universit Catholique de Louvain, Mont- Godinne University Hospital , Avenue Docteur G., Thrasse 1, Yvoir 5530, Belgium 1 VMCA, velocity in middle cerebral artery; CBFi, cerebral blood flow index 2 Department of Internal Medicine, University Hospital of Patras , Patras Rio 26504, Greece 3 Department of Neurology, Universit Catholique de Louvain, Mont-Godinne University Hospital , Avenue Docteur G., Thrasse 1, Yvoir 5530, Belgium Background: The aim of this study is to evaluate the feasibility and efficacy of Transcranial Doppler (TCD) in assessing cerebral perfusion changes in septic patients. Methods: Using TCD, we measured the mean velocity in the middle cerebral artery (VmMCA, cm/sec) and calculated the pulsatility index (PI), resistance index (RI) and cerebral blood flow index (CBFi = 10*MAP/1.47PI) on the first day of patients' admission or on the first day of sepsis development; measurements were repeated on the second day. Sepsis was defined according to standard criteria. Results: Forty-one patients without any known neurologic deficit treated in our 24-bed Critical Care Unit were assessed (Sepsis Group = 20, Control Group = 21). Examination was feasible in 91% of septic and 85% of non-septic patients (p = 0.89). No difference was found between the two groups in mean age, mean arterial pressure (MAP) or APACHE II score. The pCO2 values were higher in septic patients (46 12 vs. 39 4 mmHg p < 0.01). No statistically significant higher values of VmMCA were found in septic patients (110 34 cm/sec vs. 99 28 cm/sec p = 0.17). Higher values of PI and RI were found in septic patients (1.15 0.25 vs. 0.98 0.16 p < 0.01, 0.64 0.08 vs. 0.59 0.06 p < 0.01, respectively). No statistically significant lower values of CBFi were found in septic patients (497 116 vs. 548 110 p = 0.06). Conclusions: Our results suggest cerebral vasoconstriction in septic compared to non-septic patients. TCD is an efficient and feasible exam to evaluate changes in cerebral perfusion during sepsis. - Background Sepsis-associated encephalopathy (SAE) may develop in more than 50% of septic patients [1,2]. It is one of the most common causes of delirium in intensive care units [3], where it is an independent prognostic factor for increased mortality [4]. Additionally, it is suspected of contributing to long-term cognitive impairment [5]. The pathogenesis of SAE remains unclear. Alterations in cerebral perfusion during sepsis possibly play an important role in the development of this clinical entity [6]. Microcirculatory dysfunction and dissociation between cerebral cells needs and perfusion at several cerebral areas was found in an experimental sepsis model [7,8]. However, in humans, microcirculatory dysfunction is not widely assessed, as, to date, no widely applicable method exists to evaluate cerebral perfusion [9]. Existing attempts to evaluate cerebral blood flow and microcirculation in humans during sepsis are limited to a small number of selected patients [10,11]. Transcranial Doppler (TCD) is a readily available and reproducible technique by which cerebral perfusion can be evaluated in everyday clinical practice. Indirect cerebral microcirculation assessment by testing cerebral autoregulation in response to several stimulations with TCD has been previously performed [12-17]. However, these methods are relatively complicated and not easily applicable. The aim of this study is to assess static cerebral perfusion characteristics and changes in septic versus non-septic critically ill patients. Methods This is a prospective observational study that was conducted in our 24-bed intensive care unit during a three-month period (July 2011 to September 2011). The study group consisted of 20 consecutive patients who developed sepsis in a period of 48 hours after their admission (sepsis group). Sepsis was defined according to standard international criteria [18]. We also enrolled 21 patients without any signs of infection on their ICU admission who were expected to stay in the ICU for more than 24 h (Control Group). The Ethics Committee of Mont-Godinne University Hospital approved the study protocol and verbal consent was obtained from all patients or from relatives in cases where the patient was not conscious. Exclusion criteria for both groups were as follows: 1) age < 18 years old, 2) known cerebral lesion (ischemic or haemorrhagic cerebrovascular event, neoplasm), 3) cerebral infection, 4) encephalopathy associated with hyperuremia, hypernatremia or hypoglycaemia, 5) hepatic encephalopathy, 6) patient supported by Intra-Aortic Balloon Pump or Table 1 Demographic and hemodynamic characteristics of the patients GCS, glasgow coma score; MA, mean arterial pressure; Hg, hemoglobin. aMedical patients: patients not operated on before their evaluation;bNumber of measurements under these medications;c >0.06 g/kg/min;d >0.05 g/kg/min, ePropofol or midazolam;fEvaluation out of sedation. Table 2 Pooled data (days 1 and 2) of Transcranial Doppler measurements for the two groups of patients VMCA systolic (cm/sec) VMCA diastolic (cm/sec) VMCA mean (cm/sec) Pulsatility Index (PI) Resistance index (RI) VMCA, velocity in middle cerebral artery; CBFi, cerebral blood flow index. by ECMO, 7) non-sinusal rhythm, 8) known severe carotid stenosis (>70%), or 9) history of extended cervical operation. Demographic data on all patients and diagnosis on ICU admission were recorded. The source of sepsis, relevant microbiological results, and treatments, including administration of adrenergic and sedative agents, were recorded. The neurology status was evaluated from GCS. For the septic patients who were intubated or nonseptic patients who were intubated urgently, the GCS before the administration of sedatives was registered. For the nonseptic patients who were intubated electively, the GCS was evaluated 6 h after the sedation cessation. For the rest of the patients, the GCS on the first day of inclusion in the study was recorded. The severity of critical illness was assessed from the Acute Physiology and Chronic Health Evaluation (APACHE) II score. Mean velocity in the middle cerebral artery (VmMCA) was measured using a 2-MHz TCD probe through the temporal bone window on both sides of the skull, twice within the first 48 h after the confirmation of sepsis diagnosis for the septic group or after ICU admission for patients in the control group. An interval period of more than 20 h between the two measurements was ensured. Each measurement on each side of the brain was repeated three times and the highest value was considered for our analysis. The average of the two values on the two brain sides was registered. A difference in depth of 0.5 cm between the two sides was considered acceptable. At the time of the measurements, (...truncated)