Effects of hyperventilation on cerebral oxygen saturation estimated using near-infrared spectroscopy: A randomised comparison between propofol and sevoflurane anaesthesia

EXAMINING THE IMPACT OF PERMISSIBILITY HYPERCAPNIA ON POSTOPERATIVE DELIRIUM AMONG ELDERLY PATIENTS UNDERGOING THORACOSCOPIC-LAPAROSCOPIC ESOPHAGECTOMY: A SINGLE-CENTER INVESTIGATIVE STUDY

ABSTRACT

Objective: This study explores how permissive hypercapnia, a key aspect of lung-protective ventilation, impacts postoperative delirium in elderly patients following thoracic surgery. Methods: A single-center trial at The Second Hospital of Anhui Medical University involved 136 elderly patients undergoing thoracoscopic esophageal cancer resection. Randomly assigned to maintain PaCO 2 35-45 mm Hg (group N) or 46-55 mm Hg (group H). Primary outcome: postoperative delirium (POD) incidence 1-3 days post-surgery. Secondary endpoints included monitoring rSO 2 , cardiovascular parameters (MAP, HR), pH, OI, and respiratory parameters (VT, RR, Cdyn, PIP) at specific time points. Perioperative tests assessed CRP/ALB ratio (CAR) and systemic inflammatory index (SII). VAS scores were documented for 3 postoperative days. Results: Postoperatively, group H showed significantly lower POD incidence than group N (7.4% vs. 19.1%, P = 0.043). Group H exhibited higher PaCO 2 and rSO 2 during surgery ( P < 0.05). Patients in group H maintained better cardiovascular stability with higher blood pressure and lower heart rate on T2-4 ( P < 0.05). Respiratory parameters were more stable in group H with lower TV, RR, and PIP, and higher Cdyn during OLV ( P < 0.05). Group H had lower pH and higher OI at T2-4 ( P < 0.05). CRP and CAR levels rose less in group H on the first day and 1 week later ( P < 0.05). Conclusions: Maintaining PaCO 2 at 46-55 mm Hg reduces POD incidence, possibly by enhancing rSO 2 levels and stabilizing intraoperative respiration/circulation.

The effect of hyperventilation versus normoventilation on cerebral oxygenation using near infrared spectroscopy in children undergoing posterior fossa tumor resection: A randomized controlled cross-over trial

BACKGROUND

This study aims to compare the effect of two different ventilation strategies on cerebral oxygenation in children undergoing posterior fossa tumor excision surgeries.

METHODS

Children scheduled for posterior fossa tumor surgeries were enrolled in this randomized, double-blinded, controlled cross-over trial. After induction of general anesthesia and positioning, participants were randomized to have mild hyperventilation for 30 min (phase 1) followed by normal ventilation for another 30 min (phase2) (early hyperventilation group, n = 23), or normal ventilation for 30 min (phase 1) followed by hyperventilation for 30 min (phase 2) (early normoventilation group, n = 19). Our primary outcome was cerebral oxygenation, measured using near-infrared spectroscopy (NIRS). Other outcomes included the intracranial pressure (ICP), brain relaxation score at the end of phase 1, and frequency of nadir NIRS.

RESULTS

Forty-two children were available for final per protocol analysis. The cerebral oxygenation decreased after the hyperventilation phase compared to the baseline values and the corresponding phases of normoventilation. The mean difference [95% confidence intervals (CI)] in cerebral oxygen saturation between the hyperventilation and normal ventilation readings was 13.45 ± 1.14% [11.14-15.76] and 11.47 ± 0.96% [11.14-15.76] in the left and right sides, respectively (p-values <0.0001). Both carryover and period effects were not significant. The ICP at the end of phase 1 did not differ between the two groups: 22.12 ± 3.75 mmHg vs. 23.26 ± 4.33, mean difference [95%CI]: -0.78 [-3.05 to 1.5], p = 0.49. Brain relaxation score was similar in the two groups.

CONCLUSION

In children undergoing posterior fossa craniotomy, moderate hyperventilation reduced cerebral oxygenation without significant improvement of the surgical brain relaxation or the ICP.

Effect of Respiratory Physiological Changes on Optic Nerve Sheath Diameter and Cerebral Oxygen Saturation in Patients With Acute Traumatic Brain Injury

BACKGROUND

Severe traumatic brain injury (TBI) results in raised intracranial pressure (ICP). Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) is a noninvasive method for the assessment of raised ICP. Manipulation of positive end-expiratory pressure (PEEP) and end-tidal carbon dioxide (ETCO2) are often used to optimize ICP and improve oxygenation in TBI patients. This study evaluated the effects of PEEP and ETCO2 on ONSD and regional cerebral oxygen saturation (rScO2) in patients with acute TBI.

METHODS

A total of 14 patients (11 males) aged older than 18 years with acute severe TBI were included in this study. ONSD and rScO2 were assessed before and after changes in PEEP from 5 to 10 cm H2O and in ETCO2 from 40 to 30 mm Hg on both pathologic and nonpathologic sides.

RESULTS

Increasing PEEP and reducing ETCO2 resulted in changes in ONSD and rScO2 on both pathologic and nonpathologic sides. On the pathologic side, ONSD and rScO2 were highest with a PEEP of 10 cm H2O:ETCO2 40 mm Hg combination and lowest with PEEP of 5 cm H2O:ETCO2 30 mm Hg (ONSD 5.24±0.49 vs. 4.27±0.36 mm, P<0.001; rScO2 70.7±9.91% vs. 66.3±9.75%, P<0.001); both PEEP and ETCO2 had significant effects on ONSD and rScO2 (P<0.001). On the nonpathologic side, ONSD and rScO2 were highest and lowest with PEEP of 10 cm H2O:ETCO2 40 mm Hg and PEEP of 5 cm H2O:ETCO2 30 mm Hg combinations, respectively (ONSD: 4.93±0.46 vs. 4.02±0.40 mm, P<0.001; rScO2: 74.77±8.30% vs. 70.69±8.12%, P<0.001). ETCO2 had a significant effect on rScO2 (P<0.001), but the impact of PEEP on rScO2 was not statistically significant (P=0.05).

CONCLUSION

Increasing PEEP resulted in significant increases in ONSD and rScO2, whereas reducing ETCO2 significantly decreased ONSD and rScO2.

Severe low cerebral oximetry in difficult cardiopulmonary bypass weaning of low body-weight infant: a case report and literature review

Background

For infants undergoing complex cardiac surgery, hemodynamic management after cardiopulmonary bypass (CPB) is challenging because of severe myocardial edema, vasomotor dysfunction and weak tolerance to a change in blood volume. More importantly, the lack of availability of equipment for advanced monitoring, such as transesophageal echocardiography or transthoracic echocardiography, restricts the accurate assessment of hemodynamics.

Case presentation

This is a case of severe hypotension and non-detectable pulse oxygen saturation (SpO₂) after CPB in a low-weight infant who had normal blood pressure and oxygen saturation before surgery. Epinephrine and milrinone were administered with cerebral oximetry monitoring rather than blood pressure measurements because cerebral oximetry was more responsive to treatment than blood pressure. Under the guidance of cerebral oximetry, the infant was successfully weaned from CPB and recovered after surgery without adverse neurological events.

Conclusions

For infants who develop refractory hypotension and failure in SpO₂ monitoring during the CPB weaning period, cerebral oximetry provides an index for assessing brain perfusion and valuable guidance for appropriate inotropic treatment.

Effects of spinal anesthesia and sedation with dexmedetomidine or propofol on cerebral regional oxygen saturation and systemic oxygenation a period after spinal injection

PURPOSE

To evaluate changes in cerebral regional oxygen saturation (rSO₂) after spinal anesthesia and compare the changes in rSO₂ and systemic oxygenation between dexmedetomidine sedation and propofol sedation.

METHODS

Thirty-six patients scheduled to undergo transurethral surgery under spinal anesthesia were randomly assigned to the dexmedetomidine (n = 18) and propofol groups (n = 18). We used near-infrared spectroscopy sensors to measure rSO₂, and obtained data from each side were averaged. After oxygen insufflation, baseline measurements of mean arterial blood pressure (MAP), heart rate, rSO₂, pulse oximetry saturation (SpO₂), bispectral index, and body temperature were made. After spinal anesthesia, we measured these parameters every 5 min. Twenty minutes after spinal injection, dexmedetomidine or propofol administration was started. We measured each parameter at 10, 25, and 40 min after the administration of dexmedetomidine or propofol.

RESULTS

The baseline rSO₂ in the dexmedetomidine group was 71.3 ± 7.3%, and that in the propofol group was 71.8 ± 5.6%. After spinal anesthesia, rSO₂ in both groups decreased significantly (dexmedetomidine group: 65.4 ± 6.9%; propofol group: 64.3 ± 7.4%). After administering sedatives, rSO₂ was equivalent after spinal anesthesia. rSO₂ was comparable between the two groups. MAP and SpO₂ were significantly higher in the dexmedetomidine group than in the propofol group.

CONCLUSION

Spinal anesthesia decreased rSO₂; however, the decline was not severe. Dexmedetomidine and propofol did not compromise cerebral oxygenation under spinal anesthesia. Nevertheless, MAP and SpO₂ were more stable in dexmedetomidine sedation than in propofol sedation. Dexmedetomidine may be suitable for spinal anesthesia.

Effect of End-Tidal Carbon Dioxide on Cerebral Dynamics in Infants With Ventricular Septal Defect: A Comparison Between Sevoflurane and Intravenous Anesthetics

OBJECTIVES

The primary aim was to compare the changes in regional cerebral oxygen saturation (rSO₂) and cerebral blood flow velocity (CBFV) during sevoflurane and intravenous anesthesia when the end-tidal carbon dioxide partial pressure (P_ETCO₂) changed in infants undergoing ventricular septal defect (VSD) repair.

DESIGN

Prospective, observational study.

SETTING

Tertiary care hospital.

PARTICIPANTS

Patients younger than 6 months with VSDs.

INTERVENTIONS

End-tidal carbon dioxide was increased by decreasing tidal volume or respiratory rate.

MEASUREMENTS AND MAIN RESULTS

The infants were randomly assigned to receive either sevoflurane (SA group) or midazolam-sufentanil based intravenous anesthesia (IA group). P_ETCO₂ levels of 30 mmHg (T1), 35 mmHg (T2), 40 mmHg (T3), or 45 mmHg (T4) were obtained by adjusting the tidal volume and respiratory rate. There were no significant intergroup differences in rSO_2. In the SA group, as P_ETCO₂ increased from T1 to T4, rSO₂ increased significantly from 68.8% ± 5.9% to 76.4% ± 6.0% (p < 0.001). CBFV increased linearly, whereas the pulsatility index and resistance index decreased linearly from T1 to T4 (p < 0.001). In the IA group, rSO₂ showed a significant increase from 68.6% ± 4.6% to 76.1% ± 6.2% with the change in P_ETCO₂ from T1 to T4 (p < 0.001). CBFV increased linearly, whereas the pulsatility index and resistance index decreased linearly from T1 to T4 (p < 0.001).

CONCLUSION

Cerebrovascular response to different P_ETCO₂ levels was preserved and similar during clinically relevant doses of sevoflurane anesthesia and midazolam-sufentanil based intravenous anesthesia in infants younger than 6 months old undergoing VSD repair.

Changes of cerebral regional oxygen saturation during pneumoperitoneum and Trendelenburg position under propofol anesthesia: a prospective observational study

BACKGROUND

We evaluated the change of cerebral regional tissue oxygen saturation (rSO₂) along with the pneumoperitoneum and the Trendelenburg position. We also assessed the relationship between the change of rSO₂ and the changes of mean arterial blood pressure (MAP), heart rate (HR), arterial carbon dioxide tension (PaCO₂), arterial oxygen tension (PaO₂), or arterial oxygen saturation (SaO₂).

METHODS

Forty-one adult patients who underwent a robotic assisted endoscopic prostatic surgery under propofol and remifentanil anesthesia were involved in this study. During the surgery, a pneumoperitoneum was established using carbon dioxide. Measurements of rSO₂, MAP, HR, PaCO₂, PaO₂, and SaO₂ were performed before the pneumoperitoneum (baseline), every 5 min after the onset of pneumoperitoneum, before the Trendelenburg position. After the onset of the Trendelenburg position, rSO₂, MAP, HR were recorded at 5, 10, 20, 30, 45, and 60 min, and PaCO₂, PaO₂, and SaO₂ were measured at 10, 30, and 60 min.

RESULTS

Before the pneumoperitoneum, left and right rSO₂ were 67.9 ± 6.3% and 68.5 ± 7.0%. Ten minutes after the onset of pneumoperitoneum, significant increase in the rSO₂ was observed (left: 69.6 ± 5.9%, right: 70.6 ± 7.4%). During the Trendelenburg position, the rSO₂ increased initially and peaked at 5 min (left: 72.2 ± 6.5%, right: 73.1 ± 7.6%), then decreased. Multiple regression analysis showed that change of rSO₂ correlated with MAP and PaCO₂.

CONCLUSIONS

Pneumoperitoneum and the Trendelenburg position in robotic-assisted endoscopic prostatic surgery did not worsen cerebral oxygenation. Arterial blood pressure is the critical factor in cerebral oxygenation.

TRIAL REGISTRATION

Japan Primary Registries Network (JPRN); UMIN-CTR ID; UMIN000026227 (retrospectively registered).

Effects of anesthesia on cerebral blood flow, metabolism, and neuroprotection

Administration of anesthetic agents fundamentally shifts the responsibility for maintenance of homeostasis from the patient and their intrinsic physiological regulatory mechanisms to the anesthesiologist. Continuous delivery of oxygen and nutrients to the brain is necessary to prevent irreversible injury and arises from a complex series of regulatory mechanisms that ensure uninterrupted cerebral blood flow. Our understanding of these regulatory mechanisms and the effects of anesthetics on them has been driven by the tireless work of pioneers in the field. It is of paramount importance that the anesthesiologist shares this understanding. Herein, we will review the physiological determinants of cerebral blood flow and how delivery of anesthesia impacts these processes.

Changes in cerebral oxygenation based on intraoperative ventilation strategy

Introduction

Cerebral oxygenation can be monitored clinically by cerebral oximetry (regional oxygen saturation, rSO₂) using near-infrared spectroscopy (NIRS). Changes in rSO₂ have been shown to precede changes in pulse oximetry, providing an early detection of clinical deterioration. Cerebral oximetry values may be affected by various factors, including changes in ventilation. The aim of this study was to evaluate the changes in rSO₂ during intraoperative changes in mechanical ventilation.

Patients and methods

Following the approval of the institutional review board (IRB), tissue and cerebral oxygenation were monitored intraoperatively using NIRS. Prior to anesthetic induction, the NIRS monitor was placed on the forehead and over the deltoid muscle to obtain baseline values. NIRS measurements were recorded each minute over a 5-min period during general anesthesia at four phases of ventilation: 1) normocarbia (35–40 mmHg) with a low fraction of inspired oxygen (FiO₂) of 0.3; 2) hypocarbia (25–30 mmHg) and low FiO₂ of 0.3; 3) hypocarbia and a high FiO₂ of 0.6; and 4) normocarbia and a high FiO₂. NIRS measurements during each phase were compared with sequential phases using paired t-tests.

Results

The study cohort included 30 adolescents. Baseline cerebral and tissue oxygenation were 81% ± 9% and 87% ± 5%, respectively. During phase 1, cerebral rSO₂ was 83% ± 8%, which decreased to 79% ± 8% in phase 2 (hypocarbia and low FiO₂). Cerebral oxygenation partially recovered during phase 3 (81% ± 9%) with the increase in FiO₂ and then returned to baseline during phase 4 (83% ± 8%). Each sequential change (e.g., phase 1 to phase 2) in cerebral oxygenation was statistically significant (p < 0.01). Tissue oxygenation remained at 87%–88% throughout the study.

Conclusion

Cerebral oxygenation declined slightly during general anesthesia with the transition from normocarbia to hypocarbic conditions. The rSO₂ decrease related to hypocarbia was easily reversed with a return to baseline values by the administration of supplemental oxygen (60% vs. 30%).