An Evaluation of a New Combined Spo2/PtcCO2 Sensor in Very Low Birth Weight Infants

Short term general anesthesia for retro-bulbar block in ophthalmic surgery generates no significant hypercapnia

To assess the impact of short time hypnosis for retro-bulbar anesthesia on ventilation in patients undergoing ophthalmic surgery of the anterior eye chamber. In all patients, a combined continuous transcutaneous carbon dioxide tension (PtcCO₂) and partial oxygen saturation (SpO₂) measurement was applied in addition to routine monitoring. To enable unconscious application of retro-bulbar anesthesia, intravenous thiopental was given in one to multiple bolus doses. Transient breathing support included chin lift, Esmarch maneuver and manual hand-bag ventilation via face mask. Main endpoints were apnea time, recovery time according to the Richmond Agitation Sedation Scale, as well as SpO₂ and PtcCO₂ readings at predefined time points. Fifty-two patients with a mean age of 68 ± 13 years were included. Average thiopental dose was 2.7 ± 0.6 mg/kg. In seven (13.5%) patients repeated doses of thiopental were necessary to a total of 3.3 ± 1.1 mg/kg. Except one patient, no severe, significant or clinical relevant hypercapnia or desaturation periods were observed, and the occurring elevation of PtcCO₂ values did not correlate with the application of repeated doses of thiopental or the need for the Esmarch maneuver. Higher PtcCO₂ values were associated with the presence of hypertension and smoking. Apnea (p < 0.001) and recovery (p = 0.003) time were significantly prolonged in the patients needing the Esmarch maneuver. Short term anesthesia with thiopental in ophthalmic surgery is associated with a mild but not clinically relevant hypercapnia.

Agreement of Mixed Venous Carbon Dioxide Tension (PvCO2) and Transcutaneous Carbon Dioxide (PtCO2) Measurements in Ventilated Infants

Background:

Noninvasive transcutaneous carbon dioxide monitoring has been shown to be accurate in infants and children, limited data are available to show the usefulness and limitations of partial transcutaneous carbon dioxide tension (PtCO₂) value.

Objectives:

The current study prospectively determines the effectiveness and accuracy of PtCO₂ measurements in newborns.

Materials and Methods:

Venous blood gas sampling and monitoring of the PtCO₂ level (TCM TOSCA, Radiometer) were done simultaneously. All measurements are performed on mechanically ventilated infants. Partial venous carbon dioxide tension (PvCO₂) values divided into three groups according to hypocapnia (Group 1: < 4.68 kPa), normocapnia (Group 2: 4.68–7.33 kPa), hypercapnia (Group 3: > 7.33 kPa) and then PvCO₂ and PtCO₂ data within each group were compared separately.

Results:

A total of 168 measurements of each PvCO₂ and PtCO₂ data were compared in three separated groups simultaneously (13 in Group 1, 118 in Group 2, and 37 in Group 3). A bias of more than ± 0.7 kPa was considered unacceptable. PtCO₂ was related to PvCO₂ with acceptable results between the two measurements in hypocapnia (mean difference 0.20 ± 0.19 kPa) and normocapnia (0.002 ± 0.30 kPa) groups. On the other hand in hypercapnia group PtCO₂ values were statistically significant (P < 0.001) and lower than PvCO₂ data (mean difference 0.81 ± 1.19 kPa)

Conclusions:

PtCO₂ measurements have generally good agreement with PvCO₂ in hypocapnic and normocapnic intubated infants but there are some limitations especially with high level of CO₂ tension. Monitoring of PtCO₂ is generally a useful non-invasive indicator of PvCO₂ in hypocapnic and normocapnic infants.

Transcutaneous PCO2 monitoring in infants hospitalized with viral bronchiolitis

Our objective was to assess within a feasibility study the correlation and agreement of transcutaneous carbon dioxide (PtcCO2) monitoring with venous carbon dioxide (PvCO2) in infants with bronchiolitis in the emergency room (ER) and pediatric department. Sixty infants (aged 3.6 ± 3.3 months) admitted to our ER with bronchiolitis were included. PtcCO2 measurements (SenTec Digital Monitoring System) collected prospectively were compared with simultaneous PvCO2 drawn for patient care. Analysis included 100 measurements. The correlation of PtcCO2 and PvCO2 (r = 0.71, p < 0.001) was good, and the agreement (mean difference ± standard deviation of the differences 1.9 ± 7.0 mmHg) was adequate; average PtcCO2 was slightly lower than PvCO2. Changes in PtcCO2 and PvCO2 for consecutive measurements within each patient correlated (r = 0.41, p < 0.01). The level of PtcCO2 correlated with disease severity clinical score (p < 0.001).

CONCLUSIONS

PtcCO2 monitoring was feasible in the ER and pediatric department and was found to have a good correlation and adequate agreement with PvCO2 in infants with bronchiolitis. Because the standard deviation of the differences was relatively high, though comparable to the literature, we suggest that PtcCO2 should not replace blood gas but rather serve as a complementary tool for trending and for real-time continuous assessment of the CO2 levels.

Use of a combined SpO₂/PtcCO₂ sensor in the delivery room

Arterial oxygen saturation (SaO₂) and partial arterial pressure of carbon dioxide (PaCO₂) are important respiratory parameters in critically ill neonates. A sensor combining a pulse oximeter with the Stow-Severinghaus electrode, required for the measurement of peripheral oxygen saturation (SpO₂) and transcutaneous partial pressure of carbon dioxide (PtcCO₂), respectively, has been recently used in neonatal clinical practice (TOSCA^500ÒRadiometer). We evaluated TOSCA usability and reliability in the delivery room (DR), throughout three different periods, on term, late-preterm, and preterm neonates. During the first period (period A), 30 healthy term neonates were simultaneously monitored with both TOSCA and a MASIMO pulse oximeter. During the second period (period B), 10 healthy late-preterm neonates were monitored with both TOSCA and a transcutaneous device measuring PtcCO₂ (TINA^Ò TCM3, Radiometer). During the third period (period C), 15 preterm neonates were monitored with TOSCA and MASIMO after birth, during stabilization, and during transport to the neonatal intensive care unit (NICU). Blood gas analyses were performed to compare transcutaneous and blood gas values. TOSCA resulted easily and safely usable in the DR, allowing reliable noninvasive SaO₂ estimation. Since PtcCO₂ measurements with TOSCA required at least 10 min to be stable and reliable, this parameter was not useful during the early resuscitation immediately after birth. Moreover, PtcCO₂ levels were less precise if compared to the conventional transcutaneous monitoring. However, PtcCO₂ measurement by TOSCA was useful as trend-monitoring after stabilization and during transport to NICU.

Comparison of ear and chest probes in transcutaneous carbon dioxide pressure measurements during general anesthesia in adults

OBJECTIVE

For transcutaneous carbon dioxide pressure (tcPCO(2)) measurement, the probe on the trunk or extremities has been used for many years. Our previous study showed that chest was better than arm for tcPCO(2) monitoring. Recently, the ear probe has been developed. The accuracy of tcPCO(2) as a surrogate measurement of arterial carbon dioxide pressure (PaCO(2)) has not been compared between the measurement with probe on the chest and measurement with probe on the earlobe. This study compared the accuracy of tcPCO(2) measured on the chest and tcPCO(2) measured on earlobe during general anesthesia in adults using linear regression analysis and Bland-Altman plot.

METHODS

Ten patients aged 30-70 years scheduled for abdominal surgery under general anesthesia were enrolled. TcPCO(2) by TCM4™ (Radiometer, Copenhagen, Denmark, TtcPCO(2)) with its probe on the chest, tcPCO(2) by Sentec™ (Sentec AG, Therwil, Switzerland, StcPCO(2)) with ear probe, end-tidal carbon dioxide pressure (EtCO(2)), and PaCO(2) were simultaneously measured at four different sets of EtCO(2) levels in each patient. In total, 40 measurements were performed. The Scatter plot and Bland-Altman plot were obtained. Correlation coefficient (R(2)) ≥0.70 and limits of agreement ≤4 mmHg were judged as significant.

RESULTS

TtcPCO(2) showed significant positive correlation with PaCO(2) (R(2) = 0.80) but StcPCO(2) did not (R(2) = 0.55). TtcPCO(2) and PaCO(2), and StcPCO(2) and PaCO(2) had large limits of agreement (-6.56 mmHg, 4.21 mmHg and -11.05 mmHg, 7.64 mmHg, respectively). TtcPCO(2) and StcPCO(2) had no significant correlation (R(2) = 0.63) and large limits of agreement (-8.98 mmHg to 7.91 mmHg).

CONCLUSION

During general anesthesia in adults, both TtcPCO(2) and StcPCO(2) were not interchangeable with PaCO(2), but only TtcPCO(2) had good positive correlation with PaCO(2).

Transcutaneous blood gas monitoring during neonatal intensive care

AIM

To evaluate the accuracy in transcutaneous (Tc) blood gas monitoring in newborn infants, including extremely low birth weight infants, during neonatal intensive care.

METHODS

Tc PO(2) /PCO(2) was monitored in the neonatal intensive care unit (NICU) during stable infant conditions. In comparison, simultaneous arterial PO(2) and PCO(2) was measured. Sixty measurements were taken in 46 infants with median (range) birth weight of 0.93 (0.53-4.7) kg and at median (range) age of 8.5 (1-44) days. Comparison of measurements was performed using Bland-Altman plots, and the mean (95% CI) of the difference was calculated. Comparison was also performed in relation to body weight, postnatal age and oxygen requirement.

RESULTS

The mean (95% CI) difference in PO(2) (TcPO(2)-aPO(2)) was 0.3 (-0.2-0.9) kPa, and the corresponding difference in PCO(2) (TcPCO(2)-aPCO(2)) was 0.4 (0.03-0.8, p < 0.05) kPa. Some differences were related to body weight, age and oxygen requirement, but these differences were small.

CONCLUSION

There was good agreement between TcPO(2)/TcPCO(2) and corresponding arterial measurements. The mean difference between the methods was small and clinically acceptable in a current NICU. Tc blood gas monitoring could be recommended as a valuable complement for blood gas monitoring also in extremely low birth weight infants.

Accuracy of three transcutaneous carbon dioxide monitors in critically ill children

OBJECTIVES

To study the accuracy of three devices for measuring transcutaneous CO(2) tension in critically ill children.

METHODS

A prospective study comparing the values from three transcutaneous CO(2) monitors (SenTec, TOSCA 500, and TINA TCM3) with simultaneous arterial CO(2) (PaCO(2)) and end-tidal CO(2) (EtCO(2)) values. Clinical data were collected from the patients. Influence of core-skin temperature gradient and doses of inotropic drugs was evaluated.

RESULTS

There were 62 samples from 41 critically ill children with ages between 2 and 192 months (median, 18.5 months) and weights between 3.1 and 72 kg (median, 9 kg). The median PaCO(2) was 42.5 mmHg (range, 28-85 mmHg). Transcutaneous CO(2) (PtcCO(2)) values correlated better with PaCO(2) than with EtCO(2). The correlation coefficient between PaCO(2) and PtCO(2) was 0.833 with the TINA TCM3 monitor, 0.931 with the SenTec monitor, and 0.765 with the TOSCA 500 monitor. The mean (SD) differences between the PaCO(2) and PtcCO(2) were 4.5 (3.7) mmHg, 4.3 (3.8) mmHg, and 5.6 (5.1) mmHg, respectively, with the three monitors, and the differences between the PaCO(2) and PtcCO(2) were less than 7.5 mmHg in 77.7%, 81.2%, and 67.7% of the samples. Bland-Altman analysis showed a precision of +/-11.5 mmHg for TINA TCM3 monitor, +/-10.6 mmHg for SenTec monitor, and +/-14.8 mmHg for TOSCA monitor. No influence of core-skin temperature gradient and inotropic index on the differences between PaCO(2) and PtcCO(2) was observed.

CONCLUSIONS

The three transcutaneous CO(2) monitors have an acceptable correlation with arterial CO(2) tension and can be useful in critically ill children.

Optical-thermal characterization of cutaneous transilluminators

In recent years, there has been an increase in the popularity of light-emitting diode (LED)-based, battery-powered transilluminators (BPTs) for facilitating transdermal vascular access in adults and neonates. BPTs are believed to have lower potential for inducing skin burns than prior devices based on high-power broadband lamps; however, the optical and thermal outputs of BPTs are not well documented and safety limits for these devices are not well established. In this study, we characterize and assess the optical and thermal outputs of six BPTs that incorporate red, orange and white LEDs. Optical measurements included spectral irradiance and peak local irradiance. Thermal measurements included transient temperature readings for an exposure time of 4 min in ambient air and ex vivo tissue pre-heated to physiological temperatures. The greatest mean temperature rise produced in tissue by a non-white-light diode BPT was 2.5 degrees C, whereas a mean temperature rise of 9.1 degrees C was measured in a BPT that incorporated white-light diodes with relatively high irradiance levels. The dominant cause of temperature rise was most likely heat generation within the devices. Thermal damage analyses based on temperature limits and the Arrhenius equation indicate that although some of the devices studied approach the threshold for damage, none appear to exceed it under normal operating conditions. The results demonstrated that ambient air measurements may be suitable for identifying worst-case BPT temperatures. This study highlights the potential risk of LED-based medical devices as well as the need for additional research on related issues such as neonatal thermal injury thresholds.