Our objective was to evaluate if changes in on-pump cerebral blood flow, relative to the pre-bypass baseline, are associated with the risk for postoperative delirium (POD) following cardiac surgery. In 47 consecutive adult patients, right middle cerebral artery blood flow velocity (MCAV) was assessed using transcranial Doppler sonography. Individual values, measured during cardiopulmonary bypass (CPB), were normalized to the pre-bypass baseline value and termed MCAV_rel. An MCAV_rel > 100% was defined as cerebral hyperperfusion. Prevalence of POD was assessed using the Confusion Assessment Method for the Intensive Care Unit. Overall prevalence of POD was 27%. In the subgroup without POD, 32% of patients had experienced relative cerebral hyperperfusion during CPB, compared to 67% in the subgroup with POD (p < 0.05). The mean averaged MCAV_rel was 90 (±21) % in the no-POD group vs. 112 (±32) % in the POD group (p < 0.05), and patients developing delirium experienced cerebral hyperperfusion during CPB for about 39 (±35) min, compared to 6 (±11) min in the group without POD (p < 0.001). In a subcohort with pre-bypass baseline MCAV (MCAV_bas) below the median MCAV_bas of the whole cohort, prevalence of POD was 17% when MCAV_rel during CPB was kept below 100%, but increased to 53% when these patients actually experienced relative cerebral hyperperfusion. Our results suggest a critical role for cerebral hyperperfusion in the pathogenesis of POD following on-pump open-heart surgery, recommending a more individualized hemodynamic management, especially in the population at risk.

Introduction: Near-infrared spectroscopy is now a popular method in neuromonitoring. Derived parameters like cerebral oxygenation index or Fast Fourier Transform based coherence estimates between blood pressure and cerebral blood flow have their limitations of use for stationary data and low time resolution. Wavelet transfer function analysis can be employed to estimate coherence, gain and phase relationship between two signals without these restrictions.Methods: We aimed to extend the previously described Grinsted wavelet package with rectified bias of power and transfer function gain estimation of cerebral autoregulation assessment. The algorithm was validated in simulated signals and data of five healthy male subjects undergoing a protocol to produce large changes in hemodynamics by using lower body positive pressure (LBNP) with mild hypoxia and lower body negative pressure (LBNP). We intended to compare wavelet-based observations with FFT-based estimates.Results: We found good agreement between wavelet and FFT-based coherence and gain of cerebral tissue oxygenation index, in Bland Altman Plot and linear correlations for repeated measurement especially in the low frequency range (0.04 -0.15 Hz, coherence: r = 0.69, p < 0.001, gain: r = 0.74, p = 0.001), but was less in the very low frequency range (≤0.04 Hz, coherence: r = 0.65, p < 0.001, gain: r = 0.66, p < 0.001) and high frequency range (0.15-0.4 Hz, coherence: r = 0.39, p < 0.001, gain: r = 0.71, p = 0.001). FFT-based coherence was smaller than wavelet estimates for values <0.5.Discussion: We demonstrated good agreement in power, coherence, transfer function gain estimates between FFT-based method and our modified wavelet method. This was confirmed in simulated data and in healthy subjects undergoing LBNP and LBPP with hypoxia. Near-infrared spectroscopy-derived wavelet transform could be useful for exploring cerebral autoregulation dynamics, especially in non-stationary data.

Background: Aortic arch repair for aortic dissection is still associated with a high mortality rate. Providing adequate means of neuromonitoring to guide cerebral hemodynamics is advantageous, especially during selective anterior cerebral perfusion (SACP). Objective: We aimed to investigate an easy multimodal neuromonitoring set-up consisting of processed electroencephalography (EEG), near infrared spectroscopy (NIRS), and transcranial doppler sonography (TCD). Material and methods: We collected intraoperative data from six patients undergoing surgery for aortic dissection. In addition to standard hemodynamic monitoring, patients underwent continuous bilateral NIRS, processed EEG with bispectral index (BIS), and intermittent transcranial doppler sonography of the medial cerebral artery (MCA) with a standard B‑mode ultrasound device. Doppler measurements were taken bilaterally before cardiopulmonary bypass (CPB), during CPB, and during SACP at regular intervals. Results: Of the patients four survived without neurological deficits while two suffered fatal outcomes. Of the survivors two suffered from transient postoperative delirium. Multimodal monitoring led to a change in CPB flow or cannula repositioning in three patients. Left-sided mean flow velocities of the MCA decreased during SACP, as did BIS values. Conclusion: Monitoring consisting of BIS, NIRS, and TCD may have an impact on hemodynamic management in aortic arch operations.

Background: Decreased cerebral oximetry (rSO₂) in cardiac surgery is associated with postoperative delirium (POD). However, interventions optimizing intraoperative rSO₂ are inconclusive. Methods: In this prospective observational cohort study, the relationship between rSO₂, middle cerebral artery blood flow velocity (MCAV), and processed EEG was assessed in cardiac surgery patients with and without POD. MCAV was continuously recorded by transcranial Doppler sonography (TCD), together with continuous rSO₂ and bispectral index (BIS) monitoring. Cardiopulmonary bypass (CPB) flow rate was adjusted according to body surface area. The cohort was divided into the POD and control groups, according to the postoperative results of the confusion assessment method (CAM/CAM-ICU), the 4A’s test (4AT), and the Delirium Observation Scale (DOS). A mixed model analysis was performed for intraoperative raw data. The cerebral autoregulation index was calculated from TCD, rSO₂, and arterial pressure values. Differences in impaired autoregulation were compared using the Mann–Whitney U test. Results: A total of 41 patients were included in this study. A total of 13 patients (36.11%) developed postoperative delirium. There were no significant differences in the baseline characteristics of patients with or without POD. Patients with POD had lower BIS values during CPB (adjusted mean difference −4.449 (95% CI [−7.978, −0.925])). RSO₂ was not significantly reduced in POD, (adjusted mean difference: −5.320, 95% CI [−11.508, 0.874]). In contrast, MCAV was significantly increased in POD (10.655, 95% CI [0.491, 20.819]). The duration of cerebral autoregulation impairment did not differ significantly for TCD and cerebral oximetry-derived indices (p = 0.4528, p = 0.2715, respectively). Conclusions: Our results suggest that disturbed cerebral metabolism reflects a vulnerable brain which may be more susceptible to overperfusion during CPB, which can be seen in increased MCAV values. These phenomena occur irrespectively of cerebral autoregulation.

Background and Objectives: The pupillary pain index (PPI) allows the evaluation of intraoperative nociception by measuring pupillary reaction after a localized electrical stimulus. It was the objective of this observational cohort study to investigate the pupillary pain index (PPI) as a method to evaluate the fascia iliaca block (FIB) or adductor canal block (ACB) sensory areas during general anaesthesia in orthopaedic patients with lower-extremity joint replacement surgery. Materials and Methods: Orthopaedic patients undergoing hip or knee arthroplasty were included. After anaesthesia induction, patients received an ultrasound-guided single-shot FIB or ACB with 30 mL and 20 mL of 0.375% ropivacaine, respectively. Anaesthesia was maintained with isoflurane or propofol/remifentanil. The first PPI measurements were performed after anaesthesia induction and before block insertion, the second at the end of surgery. Pupillometry scores were evaluated in the area of the femoral or saphenous nerve (target) and C3 dermatome (control). Primary outcomes were differences between PPIs before and after peripheral block insertion as well as the relationship between PPIs and postoperative pain scores; secondary outcomes were the relationship between PPIs and opioid requirements after surgery. Results: PPI decreased significantly from the first to the second measurement (4.17 ± 2.7 vs. 1.6 ± 1.2, p < 0.001 for target; 4.46 ± 2.7 vs. 2.17 ± 2.1, p < 0.001 for control). Control and target measurements did not show significant differences. A linear regression analysis showed that early postoperative pain scores could be predicted with intraoperative piritramide with improved prediction after adding PPI scores, PCA opioids and surgery type. Forty-eight-hour pain scores at rest and in movement were correlated with intraoperative piritramide and control PPI after the PNB in movement and with second-postoperative-day opioids and target PPI scores before block insertion, respectively. Conclusions: While the effect of an FIB and ACB could not be shown with PPI postoperative pain scores due to a large effect of opioids, perioperative PPI was shown to be associated with postoperative pain. These results suggest that preoperative PPI may be used to predict postoperative pain.

BACKGROUND: Previous studies have reported an association between the use of neuromuscular blocking (NMB) agents and postoperative pulmonary complications. Postoperative pulmonary function is a key indicator for postoperative pulmonary complications. Several sites can be used to assess depth and recovery from NMB. OBJECTIVES: To investigate postoperative pulmonary function change in relation to train-of-four measurements at the adductor pollicis and corrugator supercilii muscles, and anaesthesia-related variables in orthopaedic patients undergoing hip or knee arthroplasty. DESIGN: Observational study. SETTING: University hospital. PATIENTS: Orthopaedic patients undergoing hip or knee arthroplasty. MAIN OUTCOME MEASURES: Postoperative pulmonary function tests in the postanaesthesia care unit. METHODS: Patients scheduled for elective hip or knee arthroplasty received simultaneous corrugator supercilii and adductor pollicis measurements during anaesthesia conducted according to clinical standards. Forced expiratory volume in 1 s and forced vital capacity (FVC) were measured at the time of inclusion and postoperatively on the postanaesthesia care unit. Linear regression analysis was performed for association between risk factors and pulmonary function change. RESULTS: A total of 35 patients were included. After exclusions, 20 patients remained for final analysis. Corrugator supercilii showed earlier NMB recovery than adductor pollicis. FVC decreased significantly after surgery from 2.9 ± 1.0 to 2.3 ± 1.0 (P < 0.01) and forced expiratory volume in 1 s decreased from 2.3 ± 0.9 to 1.6 ± 0.8 l (P < 0.01). Patient age was the only factor significantly related to FVC decrease after surgery (P = 0.019) with a cut-off value of 65 years. CONCLUSION: Both corrugator supercilii and adductor pollicis failed to indicate recovery of pulmonary function after NMB. Age seems to be a risk factor for postoperative decline in pulmonary function. TRIAL REGISTRATION: German Clinical Trials registry, DRKS-ID: DRKS00014305.