Incongruous effect of phenylephrine on changes in cerebral blood volume measured by near-infrared spectroscopy (NIRS) indicating extracranial contamination.

We assessed extracranial contamination of the near-infrared spectroscopy (NIRS) signal during administration of phenylephrine. The study was performed with NIRO 200NX which employs both the Modified Beer-Lambert (MBL) method to measure total hemoglobin (tHb, expressed in µM), and Spatially Resolved Spectroscopy (SRS) to measure total hemoglobin content (nTHI, expressed in arbitrary units (a.u.)). SRS tends to not be affected by extracranial blood flow. As vasoconstriction with phenylephrine mainly occurs in the extracranial area, we hypothesized that if NIRS measurements are indeed prone to extracranial contamination, tHb will be more affected by the administration of phenylephrine than nTHI. After ethical committee approval, 20 consenting cardiac surgery patients were included. Phenylephrine was administered whenever clinically indicated and its effect on nTHI and tHb was evaluated. To adjust for the difference in raw scale units, Z-scores were calculated. Data were analyzed with Wilcoxon Signed Ranks Test and the Hodges-Lehmann method. A total of 191 data sets were obtained in 20 patients (10 male, 65 ± 15 years, 77 ± 16 kg, 166 ± 11 cm). The median difference before and after administration of phenylephrine was - 0.006 a.u. [95%CI - 0.010 to - 0.002] (p < 0.001) and - 0.415 µM [95%CI - 0.665 to - 0.205] (p < 0.001) for nTHI and tHb, respectively. The median difference between the Z-scores of nTHI and tHb was - 0.02 [95%CI - 0.04 to - 0.003] (p = 0.03), with a higher variability in the Z-scores of tHb. Phenylephrine induced significant larger changes in MBL values compared to SRS values, indicating that the MBL method might be more prone to extracranial contamination. Trial and clinical registry: Trial registration number: B670201939459, ethical committee number: 2019/0265, date of approval: March 19, 2019.

Microvascular reactivity monitored with near-infrared spectroscopy is impaired after induction of anaesthesia in cardiac surgery patients: An observational study.

BACKGROUND: Induction of anaesthesia causes significant macrohaemodynamic changes, but little is known about its effects on the microcirculation. However, alterations in microvascular perfusion are known to be associated with impaired tissue oxygenation and organ dysfunction. Microvascular reactivity can be assessed with vascular occlusion testing, which evaluates the response of tissue oxygen saturation to transient ischaemia and reperfusion. OBJECTIVE: The aim of the current study was to evaluate the effects of an opioid-based anaesthesia induction on microvascular reactivity. We hypothesised that despite minimal blood pressure changes, microvascular function would be impaired. DESIGN: Prospective, observational study. SETTING: Single-centre, tertiary university teaching hospital, Belgium. PATIENTS: Thirty-five adult patients scheduled for elective coronary artery bypass grafting surgery. INTERVENTION: Microvascular reactivity was assessed before and 30 min after anaesthesia induction by means of vascular occlusion testing and near-infrared spectroscopy. MAIN OUTCOME MEASURES: Tissue oxygen saturations, desaturation rate, recovery time (time from release of cuff to the maximum value) and rate of recovery were determined. RESULTS: Data are expressed as median (minimum to maximum). Tissue oxygen saturation was higher after induction of anaesthesia [70 (54 to 78) vs. 73 (55 to 94)%, P = 0.015]. Oxygen consumption decreased after induction, appreciable by the higher minimum tissue oxygen saturation [45 (29 to 69) vs. 53 (28 to 81)%, P < 0.001] and the slower desaturation rate [11 (4 to 18) vs. 9 (5 to 16)% min, P < 0.001]. After induction of anaesthesia, recovery times were longer [40 (20 to 120) vs. 48 (24 to 356) s, P = 0.004] and the rate of recovery was lower [114 (12 to 497) vs. 80 (3 to 271)% min, P < 0.001]. CONCLUSION: After induction of anaesthesia, oxygen consumption was decreased. The longer recovery times and slower rates of recovery indicate impaired microvascular reactivity after induction of anaesthesia. TRIAL REGISTRATION: The research project was registered at ClinicalTrials.gov (NCT02034682).

Assessment of Cerebral Autoregulation Patterns with Near-infrared Spectroscopy during Pharmacological-induced Pressure Changes.

BACKGROUND: Previous work has demonstrated paradoxical increases in cerebral oxygen saturation (ScO2) as blood pressure decreases and paradoxical decreases in ScO2 as blood pressure increases. It has been suggested that these paradoxical responses indicate a functional cerebral autoregulation mechanism. Accordingly, the authors hypothesized that if this suggestion is correct, paradoxical responses will occur exclusively in patients with intact cerebral autoregulation. METHODS: Thirty-four patients undergoing elective cardiac surgery were included. Cerebral autoregulation was assessed with the near-infrared spectroscopy-derived cerebral oximetry index (COx), computed by calculating the Spearman correlation coefficient between mean arterial pressure and ScO2. COx less than 0.30 was previously defined as functional autoregulation. During cardiopulmonary bypass, 20% change in blood pressure was accomplished with the use of nitroprusside for decreasing pressure and phenylephrine for increasing pressure. Effects on COx were assessed. Data were analyzed using two-way ANOVA, Kruskal-Wallis test, and Wilcoxon and Mann-Whitney U test. RESULTS: Sixty-five percent of patients had a baseline COx less than 0.30, indicating functional baseline autoregulation. In 50% of these patients (n = 10), COx became highly negative after vasoactive drug administration (from -0.04 [-0.25 to 0.16] to -0.63 [-0.83 to -0.26] after administration of phenylephrine, and from -0.05 [-0.19 to 0.17] to -0.55 [-0.94 to -0.35] after administration of nitroprusside). A negative COx implies a decrease in ScO2 with increase in pressure and, conversely, an increase in ScO2 with decrease in pressure. CONCLUSIONS: In this study, paradoxical changes in ScO2 after pharmacological-induced pressure changes occurred exclusively in patients with intact cerebral autoregulation, corroborating the hypothesis that these paradoxical responses might be attributable to a functional cerebral autoregulation.

Implementation of a structured information transfer checklist improves postoperative data transfer after congenital cardiac surgery.

BACKGROUND: During one hospital stay, a patient can be cared for by five different units. With patient transfer from one unit to another, it is of prime importance to convey a complete picture of the patient's situation to minimise the risk of medical errors and to provide optimal patient care. OBJECTIVE(S): This study was designed to test the hypothesis that the implementation of a standardised checklist used during verbal patient handover could improve postoperative data transfer after congenital cardiac surgery. DESIGN: Prospective, pre/postinterventional clinical study. SETTING: Cardiac centre of a university hospital. PATIENTS: Forty-eight patients younger than 16 years undergoing heart surgery. INTERVENTIONS: A standardised checklist was developed containing all data that, according to the investigators, should be communicated during the handover of a paediatric cardiac surgery patient from the operating room to the ICU. MAIN OUTCOME MEASURES: Data transfer during the postoperative handover before and after implementation of the checklist was evaluated. Duration of handover, number of interruptions, number of irrelevant data and number of confusing pieces of information were noted. Assessment of the handover process by ICU medical and nursing staff was quantified. RESULTS: After implementation of the information transfer checklist, the overall data transfer increased from 48 to 73% (P < 0.001). The duration of data transfer decreased from a median (range) of 6 (2 to 16) to 4 min (2 to 19) (P = 0.04). The overall handover assessment by the intensive care nursing staff improved significantly after implementation of the checklist. CONCLUSION: Implementation of an information transfer checklist in postoperative paediatric cardiac surgery patients resulted in a more complete transfer of information, with a decrease in the handover duration.

The effect of retrograde autologous priming volume on haemodilution and transfusion requirements during cardiac surgery.

OBJECTIVES: Many cardiac procedures using cardiopulmonary bypass (CPB) still require intraoperative transfusion. Retrograde autologous priming (RAP) has been introduced to decrease haemodilution and the blood transfusion rate. This study is designed to determine the influence or RAP on intraoperative haematocrit, transfusion and its clinical consequences. METHODS: The RAP effect was retrospectively studied in 753 patients during contemporary cardiac surgery, targeting a haematocrit of 25%. Multivariate linear regression analysis was performed to identify the independent factors influencing intraoperative haematocrit, transfusion rate and transfusion quantity. RESULTS: RAP was used in 498 patients and compared with 255 controls. RAP decreased the haemodilution level (nadir haematocrit 26.8 standard deviation [SD] 4.0% in RAP vs 25.8 SD 3.6% in controls; P = 0.001) and transfusion frequency (26.1 vs 33.3%, P = 0.04), despite smaller patients (body surface area [BSA] 1.86 SD 0.20 m(2) vs 1.91 SD 0.21 m(2) in RAP vs controls; P = 0.002) with lower preoperative haematocrit (38.9 SD 4.4% vs 40.5 SD 4.6%; P < 0.001). Optimal RAP volume was overall 475 ml (ROC area 0.55; 95% confidence interval [CI] 0.50-0.60; P = 0.04) and 375 ml in patients with BSA <1.7 m(2) (ROC area 0.63; 95% CI 0.54-0.73; P = 0.008) to decrease the transfusion incidence. Multivariate analysis revealed RAP volume as a significant determinant of nadir haematocrit (ß = 0.003, 95% CI 0.002-0.004, P < 0.001) and transfusion rate (odds ratio (OR) = 0.997, 95% CI 0.996-0.999, P < 0.001), independent of BSA, gender and preoperative haematocrit. CONCLUSIONS: Retrograde autologous priming is an effective adjunct to decrease the blood transfusion rate, coping with the CPB-related haemodilution and its adverse clinical effects. A RAP volume individualized to each patient offers most benefit as part of a multidisciplinary blood conservation approach.

Cerebral oxygen desaturation during beach chair position.

CONTEXT: Cases of ischaemic brain damage have been reported in relatively healthy patients undergoing shoulder surgery in the beach chair position. Unrecognised cerebral hypoperfusion may have contributed to these catastrophic events, indicating that routine anaesthesia monitoring may not suffice. Near-infrared spectroscopy (NIRS) provides a non-invasive, continuous method to measure regional cerebral oxygen saturation (rScO2). OBJECTIVES: The aim of this clinical investigation was to evaluate the prevalence of regional cerebral oxygen desaturation in patients undergoing shoulder surgery in the upright position during routine anaesthesia management. We also aimed to identify some causal factors for cerebral desaturation. DESIGN: Prospective, observational, blinded study. SETTING: University hospital. Observation period from 19 05 2008 to 26 08 2008. PATIENTS: Twenty consecutive adult patients presenting for elective shoulder surgery under general anaesthesia in the beach chair position were enrolled. Patients with clinically apparent neurological or cognitive dysfunction were excluded. INTERVENTIONS: Routine anaesthesia management and standard monitoring were used. The responsible anaesthesiologist was blinded to the rScO2 data and was not informed about the purpose of the study. MAIN OUTCOME MEASURES: The prevalence of cerebral oxygen desaturation was measured. RESULTS: With beach chair positioning, rScO2 decreased significantly from 79± to 57±9% on the left side and from 77±10 to 59±10% on the right side (P<0.001). A relative decrease in rScO2 of more than 20% occurred in 80% of patients when the beach chair position was adopted. Postural decreases in cerebral oxygenation were related to blood pressure (r=0.60, P=0.007) and end-tidal carbon dioxide concentration (r=0.47, P=0.035). CONCLUSION: The high prevalence of significant cerebral oxygen desaturation during shoulder surgery in the upright position underlines the need for close monitoring. NIRS might constitute a valuable technique to detect cerebral hypoperfusion in this high-risk group of patients.

Manual versus target-controlled infusion remifentanil administration in spontaneously breathing patients.

BACKGROUND: The combination of propofol-remifentanil for procedural deep sedation in spontaneously breathing patients is characterized by the frequent incidence of side effects, especially respiratory depression. These side effects may be due to either the drug combination or the drug delivery technique. Target-controlled infusion (TCI) might optimize drug delivery. In this prospective, randomized, double-blind study in patients undergoing elective colonoscopy, we thus tried to answer two questions: first, if adding remifentanil to propofol surpasses the disadvantages of the combination of these two products, and second, if administration of remifentanil via TCI decreases the incidence of side effects, compared to manually controlled administration. METHODS: Patients undergoing elective colonoscopy were randomly assigned to receive remifentanil via manually controlled continuous infusion (MCI) (0.125 microg x kg(-1) x min(-1) for 2 min followed by a continuous infusion of 0.05 microg x kg(-1) x min(-1)), TCI remifentanil (1 ng/mL), or placebo (normal saline either as TCI or manual infusion of equivalent rate). All patients received TCI propofol, adjusted to a target concentration level that provided deep sedation in which patients were not responsive to verbal commands, but maintained spontaneous ventilation without assistance. RESULTS: Significantly more patients in the placebo group showed movement, cough and hiccup, which transiently interfered with the examination. There were no clinically significant differences in hemodynamic or recovery variables among all groups. Remifentanil administered via TCI resulted in a decrease in propofol requirements. The incidence of hypopnea and apnea was less frequent when remifentanil was administered via TCI compared to MCI (TCI n = 7, MCI n = 16, P < 0.05). CONCLUSION: The combination of remifentanil and propofol for deep sedation in spontaneously breathing patients, offered better conditions for colonoscopy than propofol used as a single drug. Remifentanil administered via TCI resulted in a decrease in propofol dosing and in a lower incidence in apnea and respiratory depression (TCI n = 7, MCI n = 16, P < 0.05), compared to manually controlled administration of remifentanil.

Remifentanil used to supplement propofol does not improve quality of sedation during spontaneous respiration.

STUDY OBJECTIVE: To evaluate whether the use of remifentanil to supplement propofol during spontaneous respiration confers any benefits in terms of quality of sedation and recovery, or in terms of reduction in propofol requirements. DESIGN: Prospective, randomized, double-blind study. SETTING: University hospital. PATIENTS: 50 ambulatory adult ASA physical status I and II patients scheduled for total colonoscopy. INTERVENTIONS: Patients were randomized to receive either propofol alone or propofol plus remifentanil 0.1 microg/kg/min, while independently maintaining spontaneous respiration. MEASUREMENTS: Cardiovascular and respiratory variables were measured before induction and at 1-minute intervals thereafter. Recovery from anesthesia was assessed using simple verbal commands and the Steward Post Recovery Score. Patient satisfaction was measured with a visual analog scale. Computer simulation was used to calculate the effect-site concentrations of propofol and remifentanil. MAIN RESULTS: The depressant effects on blood pressure and respiratory function were significantly higher when propofol and remifentanil were combined. Although the addition of remifentanil resulted in a decrease of propofol usage, recovery of anesthesia was faster and patient satisfaction was higher when using propofol alone. CONCLUSIONS: The addition of remifentanil to propofol during spontaneous ventilation offered no benefits compared with the use of propofol alone.