Case Report of Hyponatremic Seizures in a Term Neonate Attributed to Excessive Maternal Coconut Water Ingestion During Labor.

We report the case of a term neonate who was somnolent at birth with ventilatory distress and experienced 2 seizures shortly after delivery. Laboratory tests revealed the neonate had a serum sodium of 113 mmol/L. The seizures stopped after treatment with midazolam, and the sodium was corrected slowly with 3% hypertonic saline without further sequelae. The severe neonatal hyponatremia and seizures were attributed to maternal consumption of excessive amounts of coconut water during labor. This case demonstrates the importance of careful consideration of both fluid volume and fluid electrolyte composition during labor to prevent adverse maternal and neonatal outcomes.

EMS Non-Transport of Low-Risk COVID-19 Patients.

Objectives: COVID-19 infections in the community have the potential to overwhelm both prehospital and in-hospital resources. Transport of well-appearing patients, in the absence of available emergency department treatment capacity, increases strain on the hospital and EMS system. In May of 2020, the Connecticut Office of EMS issued a voluntary, EMS-initiated, non-transport protocol for selected low-risk patients with symptoms consistent with COVID-19. We evaluated the implementation of this non-transport protocol in a mixed urban/suburban EMS system.Methods: We conducted a retrospective review of contemporaneously recorded quality improvement documentation for uses of the Connecticut COVID-19 non-transport protocol by EMS clinicians within our EMS system during two implementations: from 12/14/2020 to 5/1/21, and again from 1/3/22 to 2/18/22, which coincided with large COVID-19 case surges in our region.Results: The vast majority of patients treated under the non-transport protocol were not reevaluated by EMS or in our emergency departments in the subsequent 24 hours. There was reasonable adherence to the protocol, with 83% of cases appropriate for the non-transport protocol. The most common reasons for protocol violations were age outside of protocol scope (pediatric patients), failure of documentation, or vital signs outside of the established protocol parameters. We did not find an increased 24-hour ED visit rate in patients who were inappropriately triaged to the protocol. Of patients who had ED visits within 24 hours, only two were admitted, none to higher levels of care.Conclusion: Within this small study, EMS clinicians in our system were able to safely and accurately apply a non-transport protocol for patients presenting with symptoms consistent with COVID-19. This is consistent with previous literature suggesting that EMS-initiated non-transport is a viable strategy to reduce the burden on health systems.

An Evaluation of Prehospital Adenosine Use.

BACKGROUND: Adenosine has been safely used by paramedics for the treatment of stable supraventricular tachycardia since the mid-1990s. However, there continues to be variability in paramedics' ability to identify appropriate indications for adenosine administration. As the first of a planned series of studies aimed at improving the accuracy of SVT diagnosis and successful administration of adenosine by paramedics, this study details the current usage patterns of adenosine by paramedics. METHODS: This cross-sectional retrospective study investigated adenosine use within a large northeast EMS region from January 1, 2019, through September 30, 2021. Excluding pediatric and duplicate case reports, we created a dataset containing patient age, sex, and vital signs before, during, and after adenosine administration; intravenous line location; and coded medical history from paramedic narrative documentation, including a history of atrial fibrillation, suspected arrhythmia diagnosis, and effect of adenosine. In cases with available prehospital electrocardiograms (EKGs) for review, two physicians independently coded the arrhythmia diagnosis and outcome of adenosine administration. Statistical analysis included interrater reliability with Cohen's kappa statistic. RESULTS: One hundred eighty-three cases were included for final analysis, 84 did not have a documented EKG for review. Categorization of presenting rhythms in these cases occurred by a physician reviewing EMS narrative and documentation. Forty of these 84 cases (48%) were adjudicated as SVT likely, 32 (38%) as SVT unlikely and 12 (14%) as uncategorized due to lack of supporting documentation. Of the 99 cases with EKGs available to review, there was substantial agreement of arrhythmia diagnosis interpretation between physician reviewers (Cohen's kappa 0.77-1.0); 54 cases were adjudicated as SVT by two physician reviewers. Other identified cardiac rhythms included atrial fibrillation (16), sinus tachycardia (11), and ventricular tachycardia (2). Adenosine cardioversion occurred in 47 of the 99 cases with EKGs available for physician review (47.5%). Adenosine cardioversion was also deemed to occur in 87% (47/54) of cases when the EKG rhythm was physician adjudicated SVT. CONCLUSIONS: This study supports the use of adenosine as a prehospital treatment for SVT while highlighting the need for continued efforts to improve paramedics' identification and management of tachyarrhythmias.

Beyond the epidural: Alternatives to neuraxial labor analgesia.

Labor creates an intense pain experienced by women across the world. Although neuraxial analgesia is the most effective treatment of labor pain, in many cases, it may not be undesired, not available, or have contraindications. In addition, satisfaction with labor analgesia is not only determined by the efficacy of analgesia but a woman's sense of agency and involvement in the childbirth experience are also key contributors. Providing safe choices for labor analgesia and support is central to creating a tailored, safe, and effective analgesic treatment plan with high maternal satisfaction. Healthcare provider knowledge of various nonneuraxial analgesic options, including efficacy, contraindications, safe clinical implementation, and side effects of various techniques is needed for optimal patient care and satisfaction. Future rigorous scientific studies addressing all of these labor analgesia options are needed to improve our understanding. This review summarizes the current published literature for commonly available non-neuraxial labor analgesic options.

Care Levels for Fetal Therapy Centers.

Fetal therapies undertaken to improve fetal outcome or to optimize transition to neonate life often entail some level of maternal, fetal, or neonatal risk. A fetal therapy center needs access to resources to carry out such therapies and to manage maternal, fetal, and neonatal complications that might arise, either related to the therapy per se or as part of the underlying fetal or maternal condition. Accordingly, a fetal therapy center requires a dedicated operational infrastructure and necessary resources to allow for appropriate oversight and monitoring of clinical performance and to facilitate multidisciplinary collaboration between the relevant specialties. Three care levels for fetal therapy centers are proposed to match the anticipated care complexity, with appropriate resources to achieve an optimal outcome at an institutional and regional level. A level I fetal therapy center should be capable of offering fetal interventions that may be associated with obstetric risks of preterm birth or membrane rupture but that would be very unlikely to require maternal medical subspecialty or intensive care, with neonatal risks not exceeding those of moderate prematurity. A level II center should have the incremental capacity to provide maternal intensive care and to manage extreme neonatal prematurity. A level III therapy center should offer the full range of fetal interventions (including open fetal surgery) and be able manage any of the associated maternal complications and comorbidities, as well as have access to neonatal and pediatric surgical intervention including indicated surgery for neonates with congenital anomalies.

Early Changes in Patient Access Interval during the COVID-19 Pandemic.

Background: COVID-19 was first reported in the United States in January 2020. Its spread throughout the country required EMS systems to rapidly adapt to patient needs while protecting EMS personnel. EMS agencies developed protocols requiring personnel to don enhanced personal protective equipment prior to patient contact. We hypothesized that the Patient Access Interval (PAI), defined as the time from wheels stopped on scene to initial patient contact, had increased during the COVID pandemic. This had the potential to affect patient outcomes, particularly in time-sensitive emergencies such as cardiac arrest or respiratory distress. Methods: This retrospective cohort study used commercial ambulance data from the four largest cities in Connecticut at two different time points: (Pre-COVID) March-May 2019, and (COVID) March-May 2020. PAI was calculated from contemporaneously reported scene times. Total cases were analyzed, and sub-analyses performed for calls located at extended care facilities (ECFs), for all emergent (Echo/Delta) calls, and for medical cardiac arrest calls. Results: 92,846 total cases were evaluated: 50,083 from 2019, and 42,763 from 2020. Cases that did not include necessary time data for PAI were removed, yielding 75,796 total cases (41,852 from 2019, 33,944 from 2020). The average PAI increased from 1 minute 55 seconds (1 m:55s) Pre-COVID to 2 m:18s COVID. ECF PAI increased from 2 m:39s to 3 m:42s. Echo/Delta PAI increased from 1 m:42s to 2 m:07s. Medical cardiac arrest PAI increased from 1 m:27s to 2 m:04s, and ECF cardiac arrest PAI increased from 2 m:18s to 4 m:35s (all comparisons p < 0.01). Conclusions: There were statistically significant increases in all studied PAIs during COVID. The 23 second increase in PAI for all calls may not have been clinically significant in most cases; however, for life-threatening patient presentations, the increase may have been particularly relevant. The increased PAI was compounded in the ECF environment, possibly due to state-mandated screening and temperature checks of EMS personnel before entering facilities. This was highlighted in the ECF cardiac arrest data, which demonstrated a clinically significant increase in PAI of 2m:17s. While this study was limited by the accuracy of contemporaneous time reports by EMS, the results support our hypothesis that PAI had increased during the COVID pandemic.

Transfusion Preparedness in the Labor and Delivery Unit: An Initiative to Improve Safety and Cost.

OBJECTIVE: To evaluate patient safety, resource utilization, and transfusion-related cost after a policy change from universal type and screen to selective type and screen on admission to labor and delivery. METHODS: Between October 2017 and September 2019, we performed a single-center implementation study focusing on risk-based type and screen instead of universal type and screen. Implementation of our policy was October 2018 and compared 1 year preimplementation with 1 year postimplementation. Patients were risk-stratified in alignment with California Maternal Quality Care Collaborative recommendations. Under the new policy, the blood bank holds a blood sample for processing (hold clot) on patients at low- and medium-risk of hemorrhage. Type and screen and crossmatch are obtained on high-risk patients or with a prior positive antibody screen. We collected patient outcomes, safety and cost data, and compliance and resource utilization metrics. Cost included direct costs of transfusion-related testing in the labor and delivery unit during the study period, from a health system perspective. RESULTS: In 1 year postimplementation, there were no differences in emergency-release transfusion events (4 vs 3, P>.99). There were fewer emergency-release red blood cell (RBC) units transfused (9 vs 24, P=.002) and O-negative RBC units transfused (8 vs 18, P=.016) postimplementation compared with preimplementation. Hysterectomies (0.05% vs 0.1%, P=.44) and intensive care unit admissions (0.45% vs 0.51%, P=.43) were not different postimplementation compared with preimplementation. Postimplementation, mean monthly type and screen-related costs (ABO typing, antibody screen, and antibody workup costs) were lower, $9,753 compared with $20,676 in the preimplementation year, P<.001. CONCLUSION: Implementation of selective type and screen policy in the labor and delivery unit was associated with projected annual savings of $181,000 in an institution with 4,000 deliveries per year, without evidence of increased maternal morbidity.

Anesthesia for Maternal-Fetal Interventions: A Survey of Fetal Therapy Centers in the North American Fetal Therapy Network.

INTRODUCTION: A wide range of fetal interventions are performed across fetal therapy centers (FTCs). We hypothesized that there is significant variability in anesthesia staffing and anesthetic techniques. METHODS: We conducted an online survey of anesthesiology directors at every FTC within the North American Fetal Therapy Network (NAFTNet). The survey included details of fetal interventions performed in 2018, anesthesia staffing models, anesthetic techniques, fetal monitoring, and postoperative management. RESULTS: There was a 92% response rate. Most FTCs are located within an adult hospital and employ a small team of anesthesiologists. There is heterogeneity when evaluating anesthesiology fellowship training and staffing, indicating there is a multidisciplinary specialty team-based approach even within anesthesiology. Minimally invasive fetal interventions were the most commonly performed. The majority of FTCs also performed ex utero intrapartum treatment (EXIT) and open mid-gestation procedures under general anesthesia (GA). Compared to FTCs only performing minimally invasive procedures, FTCs performing open fetal procedures were more likely to have a pediatric surgeon as director and performed more minimally invasive procedures. CONCLUSIONS: There is considerable variability in anesthesia staffing, caseload, and anesthetic techniques among FTCs in NAFTNet. Most FTCs used maternal sedation for minimally invasive procedures and GA for EXIT and open fetal surgeries.

Effects of maternal folic acid supplementation during the second and third trimesters of pregnancy on neurocognitive development in the child: an 11-year follow-up from a randomised controlled trial.

BACKGROUND: Maternal folic acid (FA) supplementation before and in early pregnancy prevents neural tube defects (NTD), but it is uncertain whether continuing FA after the first trimester has benefits on offspring health. We aimed to evaluate the effect of FA supplementation throughout pregnancy on cognitive performance and brain function in the child. METHODS: Follow-up investigation of 11-year-old children, residing in Northern Ireland, whose mothers had participated in a randomised trial of Folic Acid Supplementation in the Second and Third Trimesters (FASSTT) in pregnancy and received 400 µg/day FA or placebo from the 14th gestational week. Cognitive performance (Full Scale Intelligence Quotient, Verbal Comprehension, Working Memory, Perceptual Reasoning, and Processing Speed) was assessed using the Wechsler Intelligence Scale for Children. Neuronal function was assessed using magnetoencephalographic (MEG) brain imaging. RESULTS: Of 119 mother-child pairs in the FASSTT trial, 68 children were assessed for neurocognitive performance at 11-year follow-up (Dec 2017 to Nov 2018). Children of mothers randomised to FA compared with placebo scored significantly higher in two Processing Speed tests, i.e. symbol search (mean difference 2.9 points, 95% CI 0.3 to 5.5, p = 0.03) and cancellation (11.3 points, 2.5 to 20.1, p = 0.04), whereas the positive effect on Verbal Comprehension was significant in girls only (6.5 points, 1.2 to 11.8, p = 0.03). MEG assessment of neuronal responses to a language task showed increased power at the Beta (13-30 Hz, p = 0.01) and High Gamma (49-70 Hz, p = 0.04) bands in children from FA-supplemented mothers, suggesting more efficient semantic processing of language. CONCLUSIONS: Continued FA supplementation in pregnancy beyond the early period currently recommended to prevent NTD can benefit neurocognitive development of the child. MEG provides a non-invasive tool in paediatric research to objectively assess functional brain activity in response to nutrition and other interventions. TRIAL REGISTRATION: ISRCTN ISRCTN19917787 . Registered on 15 May 2013.

Error traps in anesthesia for fetal interventions.

A wide range of fetal interventions are being performed worldwide to save the fetus's life, prevent permanent fetal organ damage, and allow a successful transition to extrauterine life. However, these are invasive procedures and can be associated with serious complications. This article focuses on promoting a culture of safety by highlighting five common error traps while anesthetizing patients for fetal interventions. They include failure to preserve uteroplacental perfusion and gas exchange, failure to achieve adequate uterine relaxation prior to hysterotomy, failure to monitor the fetus and prepare for fetal/neonatal resuscitation, failure to prepare for maternal hemorrhage, and failure to promptly treat uterine atony. Practical tips for avoiding these serious complications will also be discussed.

Anesthesia for Maternal-Fetal Interventions: A Consensus Statement From the American Society of Anesthesiologists Committees on Obstetric and Pediatric Anesthesiology and the North American Fetal Therapy Network.

Maternal-fetal surgery is a rapidly evolving specialty, and significant progress has been made over the last 3 decades. A wide range of maternal-fetal interventions are being performed at different stages of pregnancy across multiple fetal therapy centers worldwide, and the anesthetic technique has evolved over the years. The American Society of Anesthesiologists (ASA) recognizes the important role of the anesthesiologist in the multidisciplinary approach to these maternal-fetal interventions and convened a collaborative workgroup with representatives from the ASA Committees of Obstetric and Pediatric Anesthesia and the Board of Directors of the North American Fetal Therapy Network. This consensus statement describes the comprehensive preoperative evaluation, intraoperative anesthetic management, and postoperative care for the different types of maternal-fetal interventions.

Use of Remifentanil for Open in utero Fetal Myelomeningocele Repair Maintains Uterine Relaxation with Reduced Volatile Anesthetic Concentration.

INTRODUCTION: Open fetal repair of myelomeningocele (MMC) is an option for prenatally diagnosed spina bifida. Historically, high-dose volatile anesthetic was used for uterine relaxation but is associated with fetal cardiovascular depression. We examined the impact of administering a supplemental remifentanil infusion on the concentration of inhaled anesthetic required for intraoperative uterine relaxation. METHODS: We retrospectively analyzed 22 consecutive patients who underwent open fetal MMC repair with desflurane anesthesia from 2014 to 2018. The anesthetic protocol was modified to include high-dose opioid with remifentanil in 2016. We examined intraoperative end-tidal desflurane concentrations, vasopressor use, incidence of umbilical artery Doppler abnormalities, and incidence of preterm labor and delivery. RESULTS: Patients (n = 11) who received desflurane and remifentanil (Des/Remi) were compared to patients (n = 11) who received desflurane (Des) alone. Intraoperatively, the maximum end-tidal desflurane required to maintain uterine relaxation was lower in the Des/Remi group (7.9 ± 2.2% vs. 13.1 ± 1.2%, p < 0.001). The mean phenylephrine infusion rate was also lower in the Des/Remi group (36 ± 14 vs. 53 ± 10 mcg/min, p = 0.004). DISCUSSION: Use of opioid with supplemental remifentanil was associated with lower volatile anesthetic dosing and decreased vasopressor use; fetal outcomes were not different. Remifentanil may allow for less volatile anesthetic use while maintaining adequate uterine relaxation.

New Method of Destroying Waste Anesthetic Gases Using Gas-Phase Photochemistry.

BACKGROUND: The inhalation anesthetics are potent greenhouse gases. To reduce the global environmental impact of the health care sector, technologies are sought to limit the release of waste anesthetic gas into the atmosphere. METHODS: Using a photochemical exhaust gas destruction system, removal efficiencies for nitrous oxide, desflurane, and sevoflurane were measured at various inlet concentrations (25% and 50%; 1.5%, 3.0%, and 6.0%; and 0.5%, 1.0%, and 2.0%, respectively) with flow rates ranging from 0.25 to 2.0 L/min. To evaluate the economic competitiveness of the anesthetic waste gas destruction system, its price per ton of carbon dioxide equivalent was calculated and compared to other greenhouse gas abatement technologies and current market prices. RESULTS: All inhaled anesthetics evaluated demonstrate enhanced removal efficiencies with decreasing flow rates (P < .0001). Depending on the anesthetic and its concentration, the photochemical exhaust gas destruction system exhibits a constant first-order removal rate, k. However, there was not a simple relation between the removal rate k and the species concentration. The costs for removing a ton of carbon dioxide equivalents are <$0.005 for desflurane, <$0.114 for sevoflurane, and <$49 for nitrous oxide. CONCLUSIONS: Based on this prototype study, destroying sevoflurane and desflurane with this photochemical anesthetic waste gas destruction system design is efficient and cost-effective. This is likely also true for other halogenated inhalational anesthetics such as isoflurane. Due to differing chemistry of nitrous oxide, modifications of this prototype photochemical reactor system are necessary to improve its removal efficiency for this gas.

A Comparison of Spinal Anesthesia Versus Monitored Anesthesia Care With Local Anesthesia in Minimally Invasive Fetal Surgery.

BACKGROUND: Minimally invasive fetal surgery is commonly performed to treat twin-to-twin transfusion syndrome with selective fetoscopic laser photocoagulation and twin-reversed arterial perfusion sequence using radiofrequency ablation. Although an increasing number of centers worldwide are performing these procedures, anesthetic management varies. Both neuraxial anesthesia and monitored anesthesia care with local anesthesia are used at different institutions. We sought to determine the efficacy and outcomes of these 2 anesthetic techniques for fetal procedures at our institution. METHODS: All patients undergoing minimally invasive fetal surgery for twin-to-twin transfusion syndrome or twin-reversed arterial perfusion sequence over a 6-year time period (2011-2016) were reviewed. Patients receiving monitored anesthesia care with local anesthesia were compared with those receiving spinal anesthesia in both selective fetoscopic laser photocoagulation and radiofrequency ablation fetal procedures. The primary outcome examined between the monitored anesthesia care and spinal anesthesia groups was the difference in conversion to general anesthesia using a noninferiority design with a noninferiority margin of 5%. Secondary outcome measures included use of vasopressors, procedure times, intraoperative fluids administered, maternal complications, and unexpected fetal demise within 24 hours of surgery. RESULTS: The difference in failure rate between monitored anesthesia care and spinal was -0.5% (95% CI, -4.8% to 3.7%). Patients receiving monitored anesthesia care plus local anesthesia were significantly less likely to need vasopressors, had a shorter presurgical operating room time, and received less fluid (P < .001). Operative time did not differ significantly. CONCLUSIONS: Monitored anesthesia care plus local anesthesia is a reliable and safe anesthetic choice for minimally invasive fetal surgery. Furthermore, it decreases maternal hemodynamic instability and reduces preincision operating room time.

Effect of continued folic acid supplementation beyond the first trimester of pregnancy on cognitive performance in the child: a follow-up study from a randomized controlled trial (FASSTT Offspring Trial).

BACKGROUND: Periconceptional folic acid prevents neural tube defects (NTDs), but it is uncertain whether there are benefits for offspring neurodevelopment arising from continued maternal folic acid supplementation beyond the first trimester. We investigated the effect of folic acid supplementation during trimesters 2 and 3 of pregnancy on cognitive performance in the child. METHODS: We followed up the children of mothers who had participated in a randomized controlled trial in 2006/2007 of Folic Acid Supplementation during the Second and Third Trimesters (FASSTT) and received 400 µg/d folic acid or placebo from the 14th gestational week until the end of pregnancy. Cognitive performance of children at 7 years was evaluated using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) and at 3 years using the Bayley's Scale of Infant and Toddler Development (BSITD-III). RESULTS: From a total of 119 potential mother-child pairs, 70 children completed the assessment at age 7 years, and 39 at age 3 years. At 7 years, the children of folic acid treated mothers scored significantly higher than the placebo group in word reasoning: mean 13.3 (95% CI 12.4-14.2) versus 11.9 (95% CI 11.0-12.8); p = 0.027; at 3 years, they scored significantly higher in cognition: 10.3 (95% CI 9.3-11.3) versus 9.5 (95% CI 8.8-10.2); p = 0.040. At both time points, greater proportions of children from folic acid treated mothers compared with placebo had cognitive scores above the median values of 10 (girls and boys) for the BSITD-III, and 24.5 (girls) and 21.5 (boys) for the WPPSI-III tests. When compared with a nationally representative sample of British children at 7 years, WPPSI-III test scores were higher in children from folic acid treated mothers for verbal IQ (p < 0.001), performance IQ (p = 0.035), general language (p = 0.002), and full scale IQ (p = 0.001), whereas comparison of the placebo group with British children showed smaller differences in scores for verbal IQ (p = 0.034) and full scale IQ (p = 0.017) and no differences for performance IQ or general language. CONCLUSIONS: Continued folic acid supplementation in pregnancy beyond the early period recommended to prevent NTD may have beneficial effects on child cognitive development. Further randomized trials in pregnancy with follow-up in childhood are warranted. TRIAL REGISTRATION: ISRCTN ISRCTN19917787 . Registered 15 May 2013.

Peripartum Anesthesia Considerations for Placenta Accreta.

Placenta accreta spectrum is becoming more common and is the most frequent indication for peripartum hysterectomy. Management of cesarean delivery in the setting of a morbidly adherent placenta has potential for massive hemorrhage, coagulopathies, and other morbidities. Anesthetic management of placenta accreta spectrum presents many challenges including optimizing surgical conditions, providing a safe and satisfying maternal delivery experience, preparing for massive hemorrhage and transfusion, preventing coagulopathies, and optimizing postoperative pain control. Balancing these challenging goals requires meticulous preparation with a thorough preoperative evaluation of the parturient and a well-coordinated multidisciplinary approach in order to optimize outcomes for the mother and fetus.

Effects of Changes in Arterial Carbon Dioxide and Oxygen Partial Pressures on Cerebral Oximeter Performance.

BACKGROUND: Cerebral oximetry (cerebral oxygen saturation; ScO2) is used to noninvasively monitor cerebral oxygenation. ScO2 readings are based on the fraction of reduced and oxidized hemoglobin as an indirect estimate of brain tissue oxygenation and assume a static ratio of arterial to venous intracranial blood. Conditions that alter cerebral blood flow, such as acute changes in PaCO2, may decrease accuracy. We assessed the performance of two commercial cerebral oximeters across a range of oxygen concentrations during normocapnia and hypocapnia. METHODS: Casmed FORE-SIGHT Elite (CAS Medical Systems, Inc., USA) and Covidien INVOS 5100C (Covidien, USA) oximeter sensors were placed on 12 healthy volunteers. The fractional inspired oxygen tension was varied to achieve seven steady-state levels including hypoxic and hyperoxic PaO2 values. ScO2 and simultaneous arterial and jugular venous blood gas measurements were obtained with both normocapnia and hypocapnia. Oximeter bias was calculated as the difference between the ScO2 and reference saturation using manufacturer-specified weighting ratios from the arterial and venous samples. RESULTS: FORE-SIGHT Elite bias was greater during hypocapnia as compared with normocapnia (4 ± 9% vs. 0 ± 6%; P < 0.001). The INVOS 5100C bias was also lower during normocapnia (5 ± 15% vs. 3 ± 12%; P = 0.01). Hypocapnia resulted in a significant decrease in mixed venous oxygen saturation and mixed venous oxygen tension, as well as increased oxygen extraction across fractional inspired oxygen tension levels (P < 0.0001). Bias increased significantly with increasing oxygen extraction (P < 0.0001). CONCLUSIONS: Changes in PaCO2 affect cerebral oximeter accuracy, and increased bias occurs with hypocapnia. Decreased accuracy may represent an incorrect assumption of a static arterial-venous blood fraction. Understanding cerebral oximetry limitations is especially important in patients at risk for hypoxia-induced brain injury, where PaCO2 may be purposefully altered.