Non-pulsatile blood flow is associated with enhanced cerebrovascular carbon dioxide reactivity and an attenuated relationship between cerebral blood flow and regional brain oxygenation.

BACKGROUND: Systemic blood flow in patients on extracorporeal assist devices is frequently not or only minimally pulsatile. Loss of pulsatile brain perfusion, however, has been implicated in neurological complications. Furthermore, the adverse effects of absent pulsatility on the cerebral microcirculation are modulated similarly as CO2 vasoreactivity in resistance vessels. During support with an extracorporeal assist device swings in arterial carbon dioxide partial pressures (PaCO2) that determine cerebral oxygen delivery are not uncommon-especially when CO2 is eliminated by the respirator as well as via the gas exchanger of an extracorporeal membrane oxygenation machine. We, therefore, investigated whether non-pulsatile flow affects cerebrovascular CO2 reactivity (CVR) and regional brain oxygenation (rSO2). METHODS: In this prospective, single-centre case-control trial, we studied 32 patients undergoing elective cardiac surgery. Blood flow velocity in the middle cerebral artery (MCAv) as well as rSO2 was determined during step changes of PaCO2 between 30, 40, and 50 mmHg. Measurements were conducted on cardiopulmonary bypass during non-pulsatile and postoperatively under pulsatile blood flow at comparable test conditions. Corresponding changes of CVR and concomitant rSO2 alterations were determined for each flow mode. Each patient served as her own control. RESULTS: MCAv was generally lower during hypocapnia than during normocapnia and hypercapnia (p < 0.0001). However, the MCAv/PaCO2 slope during non-pulsatile flow was 14.4 cm/s/mmHg [CI 11.8-16.9] and 10.4 cm/s/mmHg [CI 7.9-13.0] after return of pulsatility (p = 0.03). During hypocapnia, non-pulsatile CVR (4.3 ± 1.7%/mmHg) was higher than pulsatile CVR (3.1 ± 1.3%/mmHg, p = 0.01). Independent of the flow mode, we observed a decline in rSO2 during hypocapnia and a corresponding rise during hypercapnia (p < 0.0001). However, the relationship between ΔrSO2 and ΔMCAv was less pronounced during non-pulsatile flow. CONCLUSIONS: Non-pulsatile perfusion is associated with enhanced cerebrovascular CVR resulting in greater relative decreases of cerebral blood flow during hypocapnia. Heterogenic microvascular perfusion may account for the attenuated ΔrSO2/ΔMCAv slope. Potential hazards related to this altered regulation of cerebral perfusion still need to be assessed. TRIAL REGISTRATION: The study was retrospectively registered on October 30, 2018, with Clinical Trial.gov (NCT03732651).

Earplugs during the first night after cardiothoracic surgery may improve a fast-track protocol.

BACKGROUND: Sleep deprivation after major surgery is common and associated with worse outcome. Noise is one important reason for sleep fragmentation, which contributes to enhanced morbidity. The purpose of this work was to evaluate the impact of earplugs on patients' sleep quality during their first night after cardiothoracic surgery to eventually improve an existing fast-track concept. METHODS: Sixty-three patients undergoing cardiothoracic surgery eligible for a postoperative fast-track regimen on our cardiothoracic post anesthesia care unit (C-PACU) were prospectively included. They were randomized to either sleep with or without earplugs. Quality of sleep was measured using questionnaires for patients and nurses. Required pain medications, pain intensity, and length of hospital stay were secondary outcome variables. RESULTS: Twenty-seven patients were randomized to the intervention group (earplugs) and 36 to the control group. Mean (SD) age was 61 (12) years. Self-reported quality of sleep was better in the intervention group (median, IQR [range]: 3, 2-4 [1-5] vs. 4, 3-5 [1-5]; scale: 1, "excellent," to 5, "very poor"; P=0.025). Patients of the intervention group also experienced less severe pain (P=0.047) despite similar dosages of administered analgesics and expressed improved satisfaction regarding their C-PACU stay (P=0.032). CONCLUSIONS: Implementation of the use of earplugs in a fast-track concept following cardiothoracic surgery is efficient and easy. Earplugs improved the quality of sleep as well as patient satisfaction and attenuated pain intensity. They may thereby contribute to a faster recovery, less morbidity, and reduced costs.

The neuroprotective effect of magnesium sulphate during iatrogenically-induced ventricular fibrillation.

UNLABELLED: We studied the neuroprotective effect of magnesium sulphate (MgSO4) administered before ventricular fibrillation was induced for internal cardioverter defibrillator threshold testing, and continued during reperfusion. METHODS: With the intention of increasing serum magnesium (Mg) to >1.2 mmol/L, 15 patients received 16 mmol of MgSO4, IV, followed by 5 mmol over two hours. Fifteen patients received placebo. Serum neuron-specific enolase (NSE) was assessed, as well as pre- and postoperative neurocognitive function. RESULTS: NSE increased in all patients, reaching a peak at 24 hours. The target Mg level was maintained throughout surgery in only nine of the Mg patients, and mainly in those with low lean body mass (LBM). In these patients, increased Mg levels were related to altered NSE release (P<0.05). NSE increased when serum Mg dropped to <1.2 mmol/L, finally exceeding levels of inadequately or untreated patients. Neurocognitive function after surgery was similar between groups. CONCLUSIONS: Insufficient dosing could account for our results, as NSE release could be inhibited by Mg >1.2 mmol/L. For neuroprotection, the Mg dosage should be adjusted according to LBM and infusion be extended to >2 hours.

Effective compression ratio--a new measurement of the quality of thorax compression during CPR.

PURPOSE: Computer-based feedback systems for assessing the quality of cardiopulmonary resuscitation (CPR) are widely used these days. Recordings usually involve compression and ventilation dependent variables. Thorax compression depth, sufficient decompression and correct hand position are displayed but interpreted independently of one another. We aimed to generate a parameter, which represents all the combined relevant parameters of compression to provide a rapid assessment of the quality of chest compression-the effective compression ratio (ECR). METHODS: The following parameters were used to determine the ECR: compression depth, correct hand position, correct decompression and the proportion of time used for chest compressions compared to the total time spent on CPR. Based on the ERC guidelines, we calculated that guideline compliant CPR (30:2) has a minimum ECR of 0.79. To calculate the ECR, we expanded the previously described software solution. In order to demonstrate the usefulness of the new ECR-parameter, we first performed a PubMed search for studies that included correct compression and no-flow time, after which we calculated the new parameter, the ECR. RESULTS: The PubMed search revealed 9 trials. Calculated ECR values ranged between 0.03 (for basic life support [BLS] study, two helpers, no feedback) and 0.67 (BLS with feedback from the 6th minute). CONCLUSION: ECR enables rapid, meaningful assessment of CPR and simplifies the comparability of studies as well as the individual performance of trainees. The structure of the software solution allows it to be easily adapted to any manikin, CPR feedback devices and different resuscitation guidelines (e.g. ILCOR, ERC).