Association between Preoperative Toe Perfusion Index and Maternal Core Temperature Decrease during Cesarean Delivery Under Spinal Anesthesia: A Prospective Cohort Study

Background: The main mechanism of temperature decrease during spinal anesthesia for cesarean delivery is core-to-peripheral redistribution of body heat, attributable to vasodilation. Perfusion index (PI) obtained with a pulse oximeter helps to assess peripheral perfusion dynamics by detecting changes in peripheral vascular tone. This study aimed to examine whether preoperative toe PI could predict spinal anesthesia-induced core temperature decrease during cesarean delivery.Methods: Parturients undergoing scheduled cesarean delivery under combined spinal-epidural anesthesia from September 2019 to March 2020 were enrolled in this single-center prospective cohort study. All parturients received 0.5% hyperbaric bupivacaine (10 mg) with fentanyl (15 µg) intrathecally. A pulse oximeter probe was placed on the left second toe for continuous PI measurement. The 3M™ Bair Hugger™ Temperature Monitoring System placed over the right temporal region was used to record core temperature over time. We evaluated the association between the maximum core temperature decrease, which is the primary outcome, and the preoperative toe PI at operating room (OR) admission using a segmented regression model (SRM) and a generalized additive model (GAM). The maximum core temperature decrease was defined as the difference between core temperature at OR admission and minimum intraoperative core temperature.Results: Forty-eight patients were evaluated. In the SRM, the slope for the association between the maximum core temperature decrease and the preoperative toe PI changed from 0.031 to 0.124 after PI = 2.4%. Likewise, with the GAM, there was a small core temperature decrease when preoperative toe PI was greater than 2.0% to 3.0%.Conclusions: A lower preoperative toe PI was associated with maternal core temperature decrease during cesarean delivery under spinal anesthesia. Preoperative toe PI is a simple, non-invasive, and effective tool for the early prediction of perioperative core temperature decrease during cesarean delivery.Trial registration: UMIN Clinical Trials Registry (registry number: UMIN000037965).URL: https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000042953

Cardiac Output and Cerebral Oxygenation in Term Neonates during Neonatal Transition

The immediate transition from foetus to neonate includes substantial changes, especially concerning the cardiovascular system. Furthermore, the brain is one of the most vulnerable organs to hypoxia during this period. According to current guidelines for postnatal stabilization, the recommended parameters for monitoring are heart rate (HR) and arterial oxygen saturation (SpO2). Recently, there is a growing interest in advanced monitoring of the cardio-circulatory system and the brain to get further objective information about the neonate’s condition during the immediate postnatal transition after birth. The aim of the present study was to combine cardiac output (CO) and brain oxygenation monitoring in term neonates after caesarean section in order to analyse the potential influence of CO on cerebral oxygenation during neonatal transition. This was a monocentric, prospective, observational study. For non-invasive cardiac output measurements, the electrical velocimetry (EV) method (Aesculon Monitor, Osypka Medical, CA, USA) was used. The pulse oximeter probe for SpO2 and HR measurements was placed on the right hand or wrist. The cerebral tissue oxygen index (cTOI) was measured using a NIRO-200NX monitor with the near-infrared spectroscopy (NIRS) transducer on the right frontoparietal head. Monitoring started at minute 1 and was continued until minute 15 after birth. At minutes 5, 10, and 15 after birth, mean CO was calculated from six 10 s periods (with beat-to-beat analysis). During the study period, 99 term neonates were enrolled. Data from neonates with uncomplicated transitions were analysed. CO showed a tendency to decrease until minute 10. During the complete observational period, there was no significant correlation between CO and cTOI. The present study was the first to investigate a possible correlation between CO and cerebral oxygenation in term infants during the immediate neonatal transition. In term infants with uncomplicated neonatal transition after caesarean section, CO did not correlate with cerebral oxygenation.

Comparison of Transmittance and Reflectance Pulse Oximetry in Anesthetized Dogs

Objectives: The tongue is the standard site for placement of a pulse oximeter probe but is difficult to access during certain procedures such as dental and ophthalmic procedures and computerized tomography of the head. The aim of this study was to evaluate the performance of a new-generation reflectance pulse oximeter using the tail and tibia as sites for probe attachment.Materials and Methods: A total of 100 client-owned dogs that underwent anesthesia for various reasons were premedicated with butorphanol (n = 50; 0.2 mg/kg; group BUT) or butorphanol and dexmedetomidine (n = 50; 5 μg/kg; group DEX), administered intravenously. Anesthesia was induced with propofol and maintained with sevoflurane. A transmittance pulse oximeter probe was placed on the tongue and served as the reference standard. A reflectance probe was randomly placed on the tail base or the proximal tibia, and the position changed after testing. Signals from three consecutive measurements were obtained at each position. Failure was defined as “no signal,” “low signal,” or a pulse difference >10/min compared with the ECG heart rate. Data were analyzed using chi-square test, Wilcoxon matched-pair signed-rank test, and Bland-Altman analysis. P < 0.05 was considered significant.Results: In both groups (BUT and DEX), failure rate was higher when the tibia and tail were used as probe sites compared with the tongue. In both groups, the failure rate was higher for the tibia than for the tail. Dexmedetomidine-induced vasoconstriction increased failure rate at all probe positions.Clinical Significance: The tail base, but not the tibia, is an acceptable position for reflectance pulse oximeter probes in dogs. The tongue remains the probe site of choice, if accessible.

Pulp Vitality Testing with a Developed Universal Pulse Oximeter Probe Holder

Background and Objectives An accurate determination of the pulp status is relevant for a proper endodontic diagnosis. Objectives: The aim was to develop a universal pulse oximeter probe holder for measuring the oxygen saturation and to evaluate the use of pulse oximetry as a test for pulp vitality, by comparing the levels of oxygen saturation in the index finger and in the healthy dental pulp. Materials and Methods The universal holder was designed with software and printed with a 3D printer. The study was carried out on 128 healthy teeth. They were divided into eight groups according to tooth type. Ten root canal treated teeth served as a negative control group. For each patient, a pulse oximeter was first applied on the tooth followed by the index finger. The significance level (α) was set at 0.05. Results: The developed and manufactured universal pulse oximeter probe holder was suitable to measure the pulp vitality of all types of teeth. The handle allowed for holding the pulse oximeter on the tooth in parallel, firmly and securely. Significantly higher oxygen saturation was observed in the index finger (97.22%) compared to the dental pulp (93.17%) (p < 0.001). No correlation was observed between the maxillary teeth and index finger oxygen saturation values (r = 0.05, p = 0.72), whereas, between the mandibular teeth and index finger, a positive correlation was detected (r = 0.29, p = 0.02). There were no significant differences in the pulp oxygen saturation values between different teeth groups. Conclusion: The newly developed universal pulse oximeter probe holder is an effective device for pulp vitality testing.

Accuracy of SpO2 measurements by placing probes on newborns' wrist and ankle

Background: Pulse oximetry is a noninvasive technique of measuring oxygenation of the blood that is used worldwide to assess critically ill patients. The accuracy of pulse oximetry reading may be related to the site of pulse oximeter probe placement; but this may be difficult in sick neonates. In neonates, palm and sole are commonly used site for probe placement. Objective: This study was conducted to assess the accuracy of pulse oximeter oxygen saturation (SpO2) from probe placement at wrist and ankle as an alternative to palm and sole in neonates. Methods: This cross sectional study was carried out in SCABU of Dhaka Shishu (Children) Hospital from December 2012 to March 2013. A total of 169 neonates were enrolled in this study. Two pulse oximeters were used for simultaneous paired SpO2 measurements. The SpO2 was measured at 0 sec, then at 30 sec and at 1 min over the palm and ipsilateral wrist, both side and repeated the same procedure over the sole and ipsilateral ankle, both side and were recorded in the case record form. Two tailed, Student’s t-test was performed for analysis of continuous, normally distributed variables. Regression analysis was performed to determine the relationship between paired SpO2 measurements. Results: A total of 169 patients (birth weight 2530.8±772.2 g, gestational age 36.7±3.9 weeks, mean age 7.7 days and age range 1-27 days) were enrolled. There was a good correlation between SpO2 measured at the palm versus the wrist (r= 0.92, p<0.0001 (right); r= 0.88, p< 0.0001 (left)) and between SpO2 measured at the sole versus the ankle (r=0.90, p<0.0001 (right); r= 0.98, p<0.0001 (left)). There was also a good agreement between paired SpO2 measurements from these sites. The bias and precision for SpO2 at the right palm and right wrist was 0.08 ± 0.65% and for the left palm and left wrist 0.05 ± 0.79%. Similarly, the bias and precision for SpO2 at the right sole and right ankle was -0.11 ± 0.63% and for the left sole and left ankle was 0.56 ± 0.32%. Conclusion: The wrist and ankle can be used as alternative sites, to measure SpO2 in newborn infants in place of the routinely used palm or sole.