Foot pulse oximeter perfusion index correlates with calf muscle perfusion measured by near-infrared spectroscopy in healthy neonates

Correlation between Perfusion Index and Left Ventricular Output in Healthy Late Preterm Infants

OBJECTIVE

The perfusion index (PI) is a noninvasive marker derived from photoelectric plethysmographic signals in pulse oximetry in the evaluation of peripheral perfusion. This study was aimed to determine the correlation between PI and left ventricular output (LVO) in healthy late preterm infants at 48th hour of life.

STUDY DESIGN

With new generation pulse oximeter (MASIMO Rad 7 Oximeter) pre- and post-ductal PI values were recorded from healthy late preterm babies at the 48th hour of life. PI was determined simultaneously with LVO as measured by transthoracic echocardiography.

RESULTS

A total of 50 late preterm babies were included in the study. The mean gestational age of the cases was 35.4 ± 0.7 weeks and the birth weight was 2,586 ± 362 g. Mean pre- and post-ductal PI values at the postnatal 48th hour of babies' life were found to be 2.0 ± 0.9 and 1.7 ± 1.1. The mean LVO value was 438 ± 124, LVO/kg 175 ± 50. When the LVO value was normalized according to the babies' body weight, there was no statistically significant correlation between the pre- and post-ductal PI and the LVO/kg value (r <0.2, p >0.05 in both comparisons).

CONCLUSION

There was no correlation between pre- and post-ductal PI and LVO values in healthy late preterm infants. This may be due to the failure of the LVO, a systemic hemodynamic parameter, to accurately reflect microvascular blood flow due to incomplete maturation of the sympathetic nervous system involved in the regulation of peripheral tissue perfusion in preterm babies.

KEY POINTS

· No correlation found between PI and LOV in preterm babies.. · LVO cannot adequately reflect peripheral blood flow.. · Sympathetic nervous system is immature in preterm infants..

Development of a Machine Learning Model of Postoperative Acute Kidney Injury Using Non-Invasive Time-Sensitive Intraoperative Predictors

Acute kidney injury (AKI) is a major postoperative complication that lacks established intraoperative predictors. Our objective was to develop a prediction model using preoperative and high-frequency intraoperative data for postoperative AKI. In this retrospective cohort study, we evaluated 77,428 operative cases at a single academic center between 2016 and 2022. A total of 11,212 cases with serum creatinine (sCr) data were included in the analysis. Then, 8519 cases were randomly assigned to the training set and the remainder to the validation set. Fourteen preoperative and twenty intraoperative variables were evaluated using elastic net followed by hierarchical group least absolute shrinkage and selection operator (LASSO) regression. The training set was 56% male and had a median [IQR] age of 62 (51-72) and a 6% AKI rate. Retained model variables were preoperative sCr values, the number of minutes meeting cutoffs for urine output, heart rate, perfusion index intraoperatively, and the total estimated blood loss. The area under the receiver operator characteristic curve was 0.81 (95% CI, 0.77-0.85). At a score threshold of 0.767, specificity was 77% and sensitivity was 74%. A web application that calculates the model score is available online. Our findings demonstrate the utility of intraoperative time series data for prediction problems, including a new potential use of the perfusion index. Further research is needed to evaluate the model in clinical settings.

Perfusion index in newborns with CHD without clinical signs of hypoperfusion and heart failure: comparison with healthy newborns

INTRODUCTION

Peripheral perfusion index has been proposed as a possible method for detecting circulatory impairment. We aimed to determine the normal range of peripheral perfusion index in healthy newborns and compare it with that of newborns with CHD.

METHODS

Right-hand saturation and right-hand peripheral perfusion index levels were recorded, and physical examination and echocardiography were performed in newborns who were 0-28 days old and whom were evaluated in our paediatric cardiology outpatient clinic. The saturation and peripheral perfusion index levels of newborns with normal heart anatomy and function were compared with those of newborns with CHD.

RESULTS

Out of 358 newborns (238 mature and 75 premature) enrolled in the study, 39 had CHD (20 mild CHD, 13 moderate CHD, and 6 severe CHD), of which 29 had CHD with left-to-right shunting, 5 had obstructive CHD, and 5 had cyanotic CHD. No newborn had clinical signs of hypoperfusion or heart failure, such as prolonged capillary refill, weakened pulses, or coldness of extremities. Peripheral perfusion index level was median (interquartile range) 1.7 (0.6) in healthy newborns, 1.8 (0.7) in newborns with mild CHD, and 1.8 (0.4) in newborns with moderate and severe CHD, and there was no significant difference between the groups regarding peripheral perfusion index level.

CONCLUSION

Peripheral perfusion index remains unchanged in newborns with CHD without the clinical signs of hypoperfusion or heart failure. Larger studies with repeated peripheral perfusion index measurements can determine how valuable this method will be in the follow-up of newborns with CHD.

Effect of intraoperative operating table rotation on lower limb perfusion index in patients in the lithotomy position

We focused on "returning to the horizontal position," one of the measures for preventing well leg compartment syndrome implemented at our hospital, and aimed to clarify the effect of intraoperative positional changes by operating table rotation on blood perfusion in the lower extremities during lithotomy in patients under general anesthesia. This prospective observational study examined 64 patients scheduled to undergo general anesthesia in the lithotomy position from March 2021 to May 2022. The primary endpoint was the perfusion index (PI) of the lower limb before and after operating table rotation. The baseline lower limb PI before the operating table rotation was 2.376 (1.591), and the lower limb PI after the change from Trendelenburg to the horizontal position was as follows: immediately after, 2.123 (1.405); 5 minutes, 1.894 (1.138); 10 minutes, 1.915 (1.167); and 15 minutes, 1.993 (1.218). Compared with the baseline, no significant difference was noted in the change in the lower limb PI due to the Trendelenburg to horizontal positional change. The baseline lower leg pressure before the operating table rotation was 51.4 (13.4) mm Hg, and the lower leg pressure after the change from the Trendelenburg to the horizontal position was as follows: immediately after, 36.6 (10.3) mm Hg; 5 minutes, 36.5 (10.2) mm Hg; 10 minutes, 36.4 (10.0) mm Hg; and 15 minutes, 36.5 (10.2) mm Hg. Compared with the baseline, the change in lower leg pressure due to the Trendelenburg to horizontal positional change showed a significant decrease immediately afterward (P < .001). After operating table rotation from the Trendelenburg to the horizontal position, the lower limb PI did not change significantly after 15 min. However, lower leg pressure showed a significant decrease immediately after returning to the horizontal position. This result provides evidence for operating table rotation as a preventive measure for well leg compartment syndrome.

Peripheral fractional oxygen extraction measured with near-infrared spectroscopy in neonates-A systematic qualitative review

BACKGROUND

Peripheral fractional oxygen extraction (pFOE) measured with near-infrared spectroscopy (NIRS) in combination with venous occlusion is of increasing interest in term and preterm neonates.

OBJECTIVE

The aim was to perform a systematic qualitative review of literature on the clinical use of pFOE in term and preterm neonates and on the changes in pFOE values over time.

METHODS

A systematic search of PubMed, Embase and Medline was performed using following terms: newborn, infant, neonate, preterm, term, near-infrared spectroscopy, NIRS, oximetry, spectroscopy, tissue, muscle, peripheral, arm, calf, pFOE, OE, oxygen extraction, fractional oxygen extraction, peripheral perfusion and peripheral oxygenation. Additional articles were identified by manual search of cited references. Only studies in human neonates were included.

RESULTS

Nineteen studies were identified describing pFOE measured with NIRS in combination with venous occlusion. Nine studies described pFOE measured on the forearm and calf at different time points after birth, both in stable preterm and term neonates without medical/respiratory support or any pathological findings. Nine studies described pFOE measured at different time points in sick preterm and term neonates presenting with signs of infection/inflammation, anemia, arterial hypotension, patent ductus arteriosus, asphyxia or prenatal tobacco exposure. One study described pFOE both, in neonates with and without pathological findings.

CONCLUSION

This systematic review demonstrates that pFOE may provide additional insight into peripheral perfusion and oxygenation, as well as into disturbances of microcirculation caused by centralization in preterm and term neonates with different pathological findings.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021249235].

Advances in the Approaches Using Peripheral Perfusion for Monitoring Hemodynamic Status

Measures of peripheral perfusion can be used to assess the hemodynamic status of critically ill patients. By monitoring peripheral perfusion status, clinicians can promptly initiate life-saving therapy and reduce the likelihood of shock-associated death. Historically, abnormal perfusion has been indicated by the observation of pale, cold, and clammy skin with increased capillary refill time. The utility of these assessments has been debated given that clinicians may vary in their clinical interpretation of body temperature and refill time. Considering these constraints, current sepsis bundles suggest the need to revise resuscitation guidelines. New technologies have been developed to calculate capillary refill time in the hopes of identifying a new gold standard for clinical care. These devices measure either light reflected at the surface of the fingertip (reflected light), or light transmitted through the inside of the fingertip (transmitted light). These new technologies may enable clinicians to monitor peripheral perfusion status more accurately and may increase the potential for ubiquitous hemodynamic monitoring across different clinical settings. This review will summarize the different methods available for peripheral perfusion monitoring and will discuss the advantages and disadvantages of each approach.

The effect of patent ductus arteriosus on pre-ductal and post-ductal perfusion index in preterm neonates

OBJECTIVE

The ductus arteriosus is a blood vessel that connects the pulmonary artery to the descending aorta during fetal life and generally undergoes spontaneous closure shortly after birth. In premature neonates it often fails to close (patent ductus arteriosus-PDA), which can result in diversion of a significant part of the left-ventricular cardiac output to the pulmonary circulation. This left-to-right shunt may result in significant increase of pulmonary blood flow and decrease of systemic perfusion (hemodynamically significant PDA-hsPDA), which may lead to severe neonatal morbidity. The study objective was to find the relationship between hsPDA and perfusion index (PI), a photoplethysmographic parameter related to systemic perfusion.

APPROACH

PI measures the relative systolic increase in tissue light absorption due to the systolic increase in the tissue blood volume. PI has been found to be directly related to tissue perfusion and is therefore expected to be affected by hsPDA.

MAIN RESULTS

PI was found to be higher in preterm neonates with hsPDA after first week of life, in comparison to those with closed DA, despite the lower systemic perfusion, probably due to reverse flow during diastole.

SIGNIFICANCE

In our study, perfusion index increased despite the lower systemic perfusion, indicating that in neonates with hsPDA, perfusion index is not necessarily a measure of perfusion. Nevertheless, PI can be used as a screening tool for suspicious PDA, in order to select a relatively small group of neonates for a more definitive examination by echocardiography, which is not suitable for universal screening.

Objective cardiovascular assessment in the neonatal intensive care unit

Traditionally, cardiovascular well-being was essentially based on whether the mean blood pressure was above or below a certain value. However, this singular crude method of assessment provides limited insight into overall cardiovascular well-being. Echocardiography has become increasingly used and incorporated into clinical care. New objective modality assessments of cardiovascular status continue to evolve and are being evaluated and incorporated into clinical care. In this review article, we will discuss some of the recent advances in objective assessment of cardiovascular well-being, including the concept of multimodal monitoring. Sophisticated haemodynamic monitoring systems are being developed, including mechanisms of data acquisition and analysis. Their incorporation into clinical care represents an exciting next stage in the management of the infant with cardiovascular compromise.

Target value of oxygen saturation during the first 10 min after birth

BACKGROUND

During neonatal resuscitation, careful oxygenation is needed. Pulse oximetry is recommended to evaluate the need for oxygenation, but it is not clear whether peripheral perfusion is adequate for the evaluation of arterial oxygen saturation (SpO₂ ). Additionally, there has been no study on the changes in SpO₂ immediately after birth in Japan, despite the indispensable need for definitive oxygenation criteria.

METHODS

A prospective observational study was performed in neonates at gestational age 35-41 weeks. An SpO₂ measurement probe was attached to the neonates immediately after birth at the right palm or wrist, and the perfusion index (PI), pulse rate, and SpO₂ were measured until 10 min after birth.

RESULTS

Sixty neonates were examined. Stable PI was obtained soon after birth, preceding SpO₂ measurement. The median PI (%) was constant at approximately 1.3, and the median SpO₂ at 2-10 min was 70%, 81%, 82%, 87%, 89%, 92%, 92%, 94%, and 95%, respectively. The current target value for SpO₂ in the Neonatal Cardiopulmonary Resuscitation (NCPR) guideline in Japan is approximately the 25th percentile.

CONCLUSION

PI is stable and sufficient in the early postnatal period, meaning that peripheral perfusion is adequate for the measurement of SpO₂ . The current target SpO₂ used in the NCPR guidelines is at approximately the 25th percentile and is thought to be sufficient for meeting oxygenation criteria.

Relationship between perfusion index and patent ductus arteriosus in preterm infants

BACKGROUND

Perfusion index (PI) is a noninvasive measure of perfusion. ΔPI (difference between pre- and postductal PI) may identify hemodynamically significant PDA. However, studies are limited to brief and intermittent ΔPI sampling. Our objective is to assess the value of continuous high resolution ΔPI monitoring in the diagnosis of PDA.

METHODS

Continuous ΔPI monitoring in preterm infants was prospectively performed using two high-resolution pulse oximeters. Perfusion Index measures (ΔPI mean and variability, pre- and postductal PI) were analyzed over a 4-h period prior to echocardiography. A cardiologist blinded to the results evaluated for PDA on echocardiography. Linear mixed regression models were utilized for analyses.

RESULTS

We obtained 31 echocardiography observations. Mean ΔPI (-0.23 vs. 0.16; P < 0.05), mean pre-PI (0.86 vs. 1.26; P < 0.05), and ΔPI variability (0.39 vs. 0.61; P = 0.05) were lower in infants with PDA compared to infants without PDA at the time of echocardiography.

CONCLUSION

Mean ΔPI, ΔPI variability, and mean pre-PI measured 4 h prior to echocardiography detect PDA in preterm infants. PI is dynamic and should be assessed continuously. Perfusion index is a promising bedside measurement to identify PDA in preterm infants.

Perfusion Index and Pulse Oximetry Screening for Congenital Heart Defects

OBJECTIVE

To evaluate the efficacy of combined pulse oximetry (POX) and perfusion index (PI) neonatal screening for severe congenital heart defects (sCHD) and assess different impacts of screening in tertiary and nontertiary hospitals.

STUDY DESIGN

A multicenter, prospective study in 10 tertiary and 6 nontertiary maternity hospitals. A total of 42 169 asymptomatic newborns from among 50 244 neonates were screened; exclusion criteria were antenatal sCHD diagnosis, postnatal clinically suspected sCHD, and neonatal intensive care unit admission. Eligible infants underwent pre- and postductal POX and PI screening after routine discharge examination. Targeted sCHD were anatomically defined. Positivity was defined as postductal oxygen saturation (SpO₂) ≤95%, prepostductal SpO₂ gradient >3%, or PI <0.90. Confirmed positive cases underwent echocardiography for definitive diagnosis. Missed cases were identified by consulting clinical registries at 6 regional pediatric heart centers. Main outcomes were incidence of unexpected sCHD; proportion of undetected sCHD after discharge in tertiary and nontertiary hospitals; and specificity, sensitivity, positive predictive value, and negative predictive value of combined screening.

RESULTS

One hundred forty-two sCHD were detected prenatally. Prevalence of unexpected sCHD was 1 in 1115 live births, similar in tertiary and nontertiary hospitals. Screening identified 3 sCHD (low SpO₂, 2; coarctation for low PI, 1). Four cases were missed. In tertiary hospitals, 95% of unsuspected sCHDs were identified clinically, whereas only 28% in nontertiary units; in nontertiary units PI-POX screening increased the detection rate to 71%.

CONCLUSIONS

PI-POX predischarge screening provided benefits in nontertiary units, where clinical recognition rate was low. PI can help identify coarctation cases missed by POX but requires further evaluation in populations with higher rates of missed cases.

The Predictive Value of Pulse Oximeters for Pulse Improvement after Angiography in Infants and Children

Background

Information from pulse oximeter waves confirms the presence of a pulse and helps obtain waves from tissue when the supplying artery is not readily accessible.

Objectives

This study determined the predictive value of pulse oximeters for detecting improved arterial pulses after angiography.

Patients and Methods

This cross-sectional, multi-center study included 467 4-day-old to 12-year-old patients and was conducted from January 2012 to January 2016. Angiographies were performed on 12-year-old or younger children for various medical reasons using venous, arterial, or both types of paths. The posterior malleolar or dorsalis pedis were palpated in punctured lower extremities. In the absence of a pulse, pulse oximetry was performed to identify pulse curves at 1 hour, 6 hours, and 12 hours after each angiography.

Results

Pulse oximetry displayed the pulses of 319 patients immediately following each angiography. Of these, 262 patients had palpable pulses at 6 hours after angiography (P < 0.0001), while 57 patients had no palpable pulse. Of these 57 patients, 15 had no palpable pulse at 12 hours after angiography (P < 0.0001). The odds of pulse improvement in children 6 hours after catheter angiography were 76% for the arterial path, 90% for the venous path, and 83.2% for both paths. At 12 hours after catheter angiography, these values increased to 91.6% for the arterial path, 100% for the venous path, and 95.9% for both paths.

Conclusions

The pulse oximeter can display the pulse curve immediately (1 hour) after angiography and indicate pulse improvement at 12 hours maximally following an angiography. In this case, heparin alone may be used instead of thrombolytic agents.

Perfusion Index in Very Low Birth Weight Premature Infants During Their First 2 Weeks of Life

BACKGROUND

Our program of research focuses on thermal and circulatory stability in extremely premature infants. In prior studies, we found that infants have long periods of time in which foot temperature (FT) is higher than central temperature. We thus wanted to determine whether blood flow in the foot is increased when FT is elevated. Perfusion index (PI) can be used as a clinical indicator of peripheral perfusion, but reports on use of PI in premature infants are lacking. We employed exploratory methodology to examine foot perfusion and temperature in very low birth weight infants.

AIMS

For premature infants after birth: (1) describe foot PI values for the first 2 weeks of life and (2) describe the relationship of longitudinal FT and PI.

STUDY DESIGN

Case study design with longitudinal FT and PI in 17 infants born at <29 weeks' gestation with birth weight < 1,200 g for 2 weeks after birth.

RESULTS

Infants averaged 851 g at birth and were 24-29 weeks' gestational age. The mean PI across all infants for 14 days was 1.04, SD = 0.79. Using a repeated measures multilevel model approach confirmed that FT and PI were positively related in these infants.

CONCLUSIONS

These findings demonstrate that perfusion is increased in the periphery in extremely premature infants when FT is increased. PI measures can be used as a trend for peripheral perfusion, and these values increase over the first 2 weeks of life in infants weighing more than 750 g.

Perfusion Index-Bedside Diagnosis of Hemodynamically Significant Patent Ductus Arteriosus

BACKGROUND

Patent ductus arteriosus (PDA) is a significant problem in preterm babies <34 weeks old. Echocardiogram (echo) is the gold standard for diagnosing PDA. Perfusion index (PI) using a pulse oximeter could aid in diagnosing a hemodynamically significant PDA (HsPDA).

OBJECTIVE

To evaluate the accuracy of delta-PI (ΔPI; pre-ductal - post-ductal PI) in diagnosing HsPDA in preterm babies <34 weeks old.

DESIGN

Prospective analytical cross-sectional (observational) study.

METHODS

Preterm infants <34 weeks old (n = 27) were enrolled in the study after parental consent. ΔPI was calculated on Days 1 and 3. Babies are categorized into two groups-HsPDA and no HsPDA based on echo on Day 3.

RESULTS

The mean gestational ages were 30.4 ± 1.9 (HsPDA) and 31.7 ± 1.6 weeks (no HsPDA), and birth weights were 1.23 ± 0.32 kg and 1.43 ± 0.34 kg, respectively (p > 0.05). Ten infants had HsPDA. The ΔPI values in Groups A and B differed significantly on Days 1 and 3 (Day 1: 1.06 ± 0.3 vs. 0.54 ± 0.2 and Day 3: 1.11 ± 0.15 vs. 0.57 ± 0.3). The area under the receiver operating characteristic curve was significant for ΔPI on Days 1 and 3. The ΔPI > 0.85 on Day 1 and > 0.95 on Day 3 had a sensitivity and specificity of 80% and 94% and 80% and 88.2%, respectively, for diagnosing HsPDA.

CONCLUSION

ΔPI is a useful, simple parameter, which could help in the assessment of PDA in preterm babies.

Oxygen saturation and perfusion index from pulse oximetry in adult volunteers with viable incisors

OBJECTIVE

Evaluation of pulp vitality is an important diagnostic procedure in dentistry. Conventional techniques for measurement of pulp vitality, including thermal stimulation, electrical stimulation, or direct dentin stimulation, are frequently associated with false positive or false negative results. Recently, oxygen saturation from pulse oximetry has been utilized in the evaluation of pulp vitality. Perfusion index (PI) data calculated from photoplethysmography have been widely used to evaluate peripheral perfusion. The combination of oxygen saturation and PI may aid in the accurate measurement of pulp vitality. We aimed to investigate the baseline values of oxygen saturation and PI using pulse oximetry in adult volunteers.

MATERIAL AND METHODS

Fifteen adult volunteers with viable incisors were tested. To measure PI, a fabricated oxygen sensor was applied to an incisor without a pulp lesion while oxygen saturation was simultaneously measured in the finger. Oxygen saturation and PI were continuously measured with customized software. The normal reference values of oxygen saturation and PI were obtained by analyzing the recorded data.

RESULTS

Pulse oximetry showed relatively stable, objective, and accurate oxygen saturation results. The tooth oxygen saturation ranged from 97% to 100%. The PI ranged from 0.3% to 0.5%, and PI and oxygen saturation showed relatively consistent values across subjects.

CONCLUSIONS

Although there are some limitations to our study, these results may prove useful for detecting teeth with impaired vitality and non-invasively differentiating between necrotic and vital pulp.

Reflectance Photoplethysmography as Noninvasive Monitoring of Tissue Blood Perfusion

In the last decades, photoplethysmography (PPG) has been used as a noninvasive technique for monitoring arterial oxygen saturation by pulse oximetry (PO), whereas near-infrared spectroscopy (NIRS) has been employed for monitoring tissue blood perfusion. While NIRS offers more parameters to evaluate oxygen delivery and consumption in deep tissues, PO only assesses the state of oxygen delivery. For a broader assessment of blood perfusion, this paper explores the utilization of dual-wavelength PPG by using the pulsatile (ac) and continuous (dc) PPG for the estimation of arterial oxygen saturation (SpO2) by conventional PO. Additionally, the Beer-Lambert law is applied to the dc components only for the estimation of changes in deoxyhemoglobin (HHb), oxyhemoglobin (HbO2), and total hemoglobin (tHb) as in NIRS. The system was evaluated on the forearm of 21 healthy volunteers during induction of venous occlusion (VO) and total occlusion (TO). A reflectance PPG probe and NIRS sensor were applied above the brachioradialis, PO sensors were applied on the fingers, and all the signals were acquired simultaneously. While NIRS and forearm SpO2 indicated VO, SpO2 from the finger did not exhibit any significant drop from baseline. During TO, all the indexes indicated the change in blood perfusion. HHb, HbO2, and tHb changes estimated by PPG presented high correlation with the same parameters obtained by NIRS during VO (r(2) = 0.960, r(2) = 0.821, and r(2) = 0.974, respectively) and during TO (r(2) = 0.988, r(2) = 0.940, and r(2) = 0.938, respectively). The system demonstrated the ability to extract valuable information from PPG signals for a broader assessment of tissue blood perfusion.

Peripheral Muscle Near-Infrared Spectroscopy in Neonates: Ready for Clinical Use? A Systematic Qualitative Review of the Literature

BACKGROUND

Peripheral muscle near-infrared spectroscopy (NIRS) measurements are of increasing interest especially in the care of critically ill patients.

OBJECTIVE

The aim was to perform a systematic qualitative review on peripheral muscle NIRS measurements in the clinical care of term and preterm neonates.

METHODS

A systematic search of PubMed and Ovid Embase was performed using the following terms: neonate, neonates, newborn, newborns, infant, infants, near-infrared spectroscopy, NIRS, oxygenation, perfusion, oxygen extraction, peripheral, tissue, muscle, calf, forearm and thigh. Additional articles were identified by a manual search of the cited references. Only human studies were included.

RESULTS

Twenty-one studies were identified to use peripheral muscle NIRS measurements as a single method, 17 studies combined cerebral and peripheral muscle NIRS measurements and 1 study used multi-site NIRS measurements in human neonates. Two randomized studies were identified. Two additional publications were included because they provided important general information about peripheral muscle NIRS measurements.

CONCLUSION

In the care of critically ill neonates peripheral muscle NIRS measurements alone or in combination with cerebral or multi-site NIRS measurements provide useful additional information about peripheral circulation and oxygenation. This method is a promising tool in the recognition of early states of centralization (compensated shock) in this vulnerable group of patients. However, before this method can be used in the clinical routine it has to be tested as monitoring to guide interventions in further studies.

Reference values of perfusion indices in hemodynamically stable newborns during the early neonatal period

We aimed to determine reference values of perfusion index (PI) in healthy newborns during the early neonatal period. Preductal (right hand) and postductal (foot) PI values were assessed during the first 5 days of life by using a new generation pulse oximetry. A total of 241 newborn infants (196 [81.3 %] term and 45 [18.7 %] preterm) were enrolled to the study. On the first day, in term infants, the median (interquartile range [IQR]) preductal and postductal PI were 1.35 (1.02-1.91) and 0.88 (0.62-1.22), respectively (p = 0.001). These values were 0.88 (0.60-1.26) and 0.61 (0.35-0.92) in preterm infants, with the same respect (p = 0.001). From the first to third days, preductal PI remained significantly higher than the postductal PI (p < 0.001, for all comparisons). Both preductal and postductal PI of term newborns were significantly higher than those of preterm infants (p < 0.001, for both comparisons). These differences in PI disappeared on the fifth day of life. Conclusion PI values which reflect peripheral perfusion seem to reach to a steady state on the fifth day of life following physiological maturation.

Perfusion index in newborn infants: a noninvasive tool for neonatal monitoring

AIM

To review the utility of perfusion index (PI) in the evaluation of neonatal clinical conditions. Twenty-five manuscripts were reviewed. PI provides information about haemodynamic stability, illness severity, early neonatal respiratory outcome, low superior vena cava flow and subclinical chorioamnionitis.

CONCLUSION

PI is a valuable tool to assess the newborn's health condition and could become a standardised measure in clinical evaluation. Different study designs are necessary to provide further validation to this method.

A pilot study to examine maturation of body temperature control in preterm infants

OBJECTIVE

To test instrumentation and develop analytic models to use in a larger study to examine developmental trajectories of body temperature and peripheral perfusion from birth in extremely low-birth-weight (EBLW) infants.

DESIGN

A case study design.

SETTING

The study took place in a Level 4 neonatal intensive care unit (NICU) in North Carolina.

PARTICIPANTS

Four ELBW infants, fewer than 29 weeks gestational age at birth.

METHODS

Physiologic data were measured every minute for the first 5 days of life: peripheral perfusion using perfusion index by Masimo and body temperature using thermistors. Body temperature was also measured using infrared thermal imaging. Stimulation and care events were recorded over the first 5 days using video which was coded with Noldus Observer software. Novel analytical models using the state space approach to time-series analysis were developed to explore maturation of neural control over central and peripheral body temperature.

RESULTS/CONCLUSION

Results from this pilot study confirmed the feasibility of using multiple instruments to measure temperature and perfusion in ELBW infants. This approach added rich data to our case study design and set a clinical context with which to interpret longitudinal physiological data.

Perfusion index in the very preterm infant

AIM

Perfusion Index (PI) is a quantifiable measurement of peripheral perfusion and may be a useful adjunct to the assessment of circulatory status in the newborn. (i) To assess reproducibility of PI and (ii) To determine whether there is a difference between simultaneously obtained limb measurements of PI in newborns <32 weeks GA in the transitional period.

METHODS

Perfusion Index was measured in newborns <32 weeks during the first 48 h of life. To examine reproducibility, the pulse oximetry probe was replaced on the same limb consecutively by the same operator. Upper and lower limbs were then simultaneously evaluated over a 5-min period. Heart rate, blood pressure, birth weight, ventilation requirement, inotrope use, lactate, PCO2 and CRIB-II score were also recorded.

RESULTS

Thirty infants were assessed. Intraclass correlation coefficient for reproducibility in the same limb was high (r value = 0.982 p < 0.001). Measurements obtained in the right upper limb were consistently higher than either lower limb. The median (IQR) PI for the entire cohort was 0.70 (0.29-1.35). No correlation existed between gestational age, birth weight, CRIB scores, systolic and diastolic blood pressure, mean blood pressure and median PI values.

CONCLUSION

Perfusion Index measurement is reproducible, and values are highest in the right upper limb. Wide differences between right upper and lower limb readings are most likely related to transitional circulatory changes.

Effects of red cell transfusion on cardiac output and perfusion index in preterm infants

OBJECTIVE/AIM

The present investigation was designed to study the effect of blood transfusion on cardiac output and perfusion index. The aim was to demonstrate a relationship between hematocrit, lactate, cardiac output and perfusion index in anemic preterm infants and to investigate significant changes in these parameters induced by RBC transfusion.

METHODS

Anemic infants who were under 35 weeks of gestational age (GA) and were in a stable clinical condition without respiratory or cardiac problems, signs of sepsis, or renal disease at the time of investigation were enrolled in the study. Enrolled infants received 15 ml/kg pure red blood cells over 4 h. Hematocrit and lactate levels were studied before and after transfusion. Cardiac output was measured by an ultrasound device (USCOM 1A) and perfusion index was monitored by pulse oximeter (MasimoRad7).

RESULTS

Cardiac output decreased by 9% (p < 0.05), due to decrease in heart rate by 10% (p < 0.05) and stroke volume significantly by 5% (p < 0.05) both in left and right sided cardiac measurements. Perfusion index significantly increased and lactate levels significantly decreased after transfusion (p < 0.05). Htc was inversely correlated with lactate levels, HR, CI and CO (r = -0.33, p = 0.01; r = -0.53, p = 0; r = -0.37, p = 0.004, r = -0.28, p = 0.03). PI was not significantly correlated with Htc levels before and after transfusion (r = 0.07, p = 0.7 and r = 0.007, p =0.97).

CONCLUSION

Our data support that heart rate, CO and CI and lactate levels increased as a response to anemia in preterm infants and RBC transfusion improved perfusion index suggesting better tissue oxygenation.

Perfusion index as a possible predictor for postanesthetic shivering

BACKGROUND

Postanesthetic shivering can be triggered by surgical stress and several aspects of anesthetic management and is frequently preceded by a decrease in peripheral blood flow due to thermoregulatory vasoconstriction. As perfusion index correlates with peripheral blood flow, we examined whether perioperative perfusion index, measured using pulse oximetry, might be correlated with postanesthetic shivering.

METHODS

Twenty-eight patients presenting for elective abdominal surgery were enrolled. Core (esophagus) and peripheral (finger) temperatures and perfusion index were recorded in the perioperative periods. Correlations between perfusion index and peripheral temperature and core-to-peripheral temperature gradient were then explored. Plasma levels of epinephrine and norepinephrine were also measured. The extent of shivering was graded after emergence from anesthesia.

RESULTS

Perfusion index declined before emergence from anesthesia in patients who then developed postanesthetic shivering. This coincided with the time at which the difference between core and peripheral temperature became dissociated and peripheral temperature declined. Perioperative perfusion index was correlated with peripheral temperature and peripheral-core temperature gradient. Perfusion index at closure of the peritoneum predicted postanesthetic shivering and was significantly correlated with the extent of shivering. Plasma levels of both epinephrine and norepinephrine were significantly elevated after shivering events.

CONCLUSIONS

Perfusion index was significantly lower in patients with postanesthetic shivering before emergence from anesthesia, indicating that measurement of perfusion index during and before the end of anesthesia might be a useful means of predicting postanesthetic shivering.

Perfusion index and its dynamic changes in preterm neonates with patent ductus arteriosus

AIM

The perfusion index (PI) and its dynamic change during respiration, and supressed the plethysmographic variability index (PVI), are calculated from pulse oximetry, and these indexes were recently proposed for continuous and noninvasive assessment of peripheral perfusion in neonates. We aimed to assess the effect of patent ductus arteriosus (PDA) on PI and PVI, according to ductal Doppler flow pattern.

METHODS

Forty-five neonates with median (Q25-75) gestational age (GA) and birthweight of 27 (25-28) weeks and 857 (750-1080) grams, respectively, were assessed prospectively using serial echocardiography and pulse oximetry during the first postnatal week.

RESULTS

Perfusion index increased from 0.70 (0.50-1.05) at day 1 to 1.50 (1.0-2.00) at day 7 (p < 0.01) and was not influenced by ductal flow pattern. PVI was 22 (18-27) and did not vary during the study period but differed according to ductal flow pattern, with lower values in the growing and pulsatile groups compared with the pulmonary hypertension (p < 0.05), closing and closed groups (p < 0.01).

CONCLUSIONS

Ductal persistence and flow pattern did not affect PI but did affect PVI in preterm neonates of less than 29 weeks of GA. Future studies are needed to establish the usefulness of PVI in the early detection and management of PDA in preterm neonates.

Equipment and monitoring--what is in the future to improve safety?

There have been a number of recent developments in the practice of anesthesia and intensive care aimed at improving outcome in terms of reducing both morbidity and mortality, as well as other less-defined factors, such as quality of service provision. Significant advances have been made in airway devices such as pediatric tracheal tube designs, Microcuff(®) tracheal tubes, and new laryngoscopes. Noninvasive monitoring devices, including continuous hemoglobin analysis and near infrared spectrometry, are being increasingly used in pediatric anesthesia. Other, 'scaled-down' versions from adult anesthesia care, however, have not universally been shown to result in improved safety and outcomes in pediatric anesthesia.

Regional tissue oxygen saturation: comparability and reproducibility of different devices

Comparability and reproducibility of different near-infrared spectroscopy devices measuring regional tissue oxygen saturation remain poor. Aim of the present study was to compare values and reproducibility of cerebral∕peripheral "tissue-oxygenation-index" (TOI; NIRO 300, Hamamatsu(®), Japan) with cerebral∕peripheral "regional-oxygen-saturation" (rSO; INVOS5100, Somanetics(®), USA), and to analyze the influence of quality criteria.

METHODS

cTOI and crSO2 were measured on the left forehead, pTOI and prSO2 were measured on the left calf. To analyse reproducibility, optodes were reapplied five times. A quality criterion was introduced for cTOI, crSO2 and prSO2. For pTOI quality criteria were introduced in combination with a venous occlusion technique.

RESULTS

Cerebral measurements were performed in 37 neonates. cTOI (72.7+∕-6.2%) was lower than crSO2 (83.3+∕-5.8%) (p < 0.001). The mean difference between cTOI and crSO2 was 10%. Mean standard deviations of cTOI and crSO2 were similar (cTOI: 4.9+∕-3.6; crSO2: 4.5+∕-2.6). Peripheral measurements were performed in 39 neonates. pTOI (66.0+∕-7.9%) was lower than prSO2 (82.0+∕-7.0%)(p < 0.001). The mean difference between pTOI and prSO2 was 15%. Mean standard deviations of pTOI (3.7+∕-2.6%) were lower than of prSO2 (5.0+∕-3.0%) (p = 0.047).

CONCLUSION

TOI values were significantly lower than rSO2 values, in cerebral and peripheral measurements. Reproducibility was higher for pTOI than for prSO2.

The perfusion index derived from a pulse oximeter for predicting low superior vena cava flow in very low birth weight infants

OBJECTIVE

Superior vena cava (SVC) flow is used as an index for evaluating systemic blood flow in neonates. Thus far, several reports have shown that low SVC flow is a risk factor for intraventricular hemorrhage (IVH) in the preterm infant. Therefore, it is likely to be a useful index in the management of the preterm infant. The perfusion index (PI) derived from a pulse oximeter is a marker that allows noninvasive and continuous monitoring of peripheral perfusion. The objective of this paper was to determine the accuracy of the PI for detecting low SVC flow in very low birth weight infants born before 32 weeks of gestation.

STUDY DESIGN

We studied the correlation between PI and SVC flow 0 to 72 h after birth in very low birth weight infants born before 32 weeks of gestation. The best cut-off value for low SVC flow was calculated from the respective receiver-operating characteristic curves.

RESULT

A positive correlation was found between the PI and SVC flow (r=0.509, P<0.001). The best cut-off value for the PI to detect low SVC flow was 0.44 (sensitivity 87.5%, specificity 86.3%, positive predictive value 38.9%, negative predictive value 98.6%).

CONCLUSION

This study found that the PI was associated with SVC flow, and it was a useful index for detecting low SVC flow in very low birth weight infants born before 32 weeks of gestation. Therefore, use of the PI should be evaluated in the cardiovascular management of the preterm infant.

Interactions among peripheral perfusion, cardiac activity, oxygen saturation, thermal profile and body position in growing low birth weight infants

AIMS

To investigate the correlation between the 'perfusion index' (PI) and other commonly used estimates of cutaneous blood flow [heart rate (HR), surface temperatures (ST) and central-to-peripheral thermal gradients (C-P grad)] and to use this new non-invasive tool to compare differences between prone and supine sleep position in low birth weight (LBW) infants.

METHODS

Six-hour continuous recordings of pulse oximetry, cardiac activity and absolute ST from three sites (flank, forearm and leg), along with minute-to-minute assessment of behavioural states were performed in 31 LBW infants. Infants were randomly assigned to the prone or supine position for the first 3 h and then reversed for the second 3 h. PI data were correlated with HR and C-P grad, and compared across sleep positions during quiet sleep (QS) and active sleep (AS).

RESULTS

Perfusion index correlated significantly with HR (r(2) = 0.40) and flank-to-forearm thermal gradient (r(2) = 0.28). In the prone position during QS, infants exhibited higher PI (3.7 +/- 0.9 vs. 3.1 +/- 0.7), HR (158.4 +/- 8.9 vs. 154.1 +/- 8.8 bpm), SpO(2) (95.8 +/- 2.6 vs. 95.2 +/- 2.6%), flank (36.7 +/- 0.4 vs. 36.5 +/- 0.4 degrees C), forearm (36.1 +/- 0.6 vs. 35.5 +/- 0.4 degrees C) and leg (35.4 +/- 0.7 vs. 34.7 +/- 0.7 degrees C) temperatures and narrower flank-to-forearm (0.6 +/- 0.4 vs. 0.9 +/- 0.3 degrees C) and flank-to-leg (1.3 +/- 0.6 vs. 1.8 +/- 0.7 degrees C) gradients, compared to those of the supine position. Similar differences were observed during AS.

CONCLUSION

Perfusion index is a good non-invasive estimate of tissue perfusion. Prone sleeping position is associated with a higher PI, possibly reflecting thermoregulatory adjustments in cardiovascular control. The effects of these position-related changes may have important implications for the increased risk for sudden infant death syndrome in prone position.

Pulse oximeter perfusion index as an early indicator of sympathectomy after epidural anesthesia

BACKGROUND

The pulse oximeter perfusion index (PI) has been used to indicate sympathectomy-induced vasodilatation. We hypothesized that pulse oximeter PI provides an earlier and clearer indication of sympathectomy following epidural anesthesia than skin temperature and arterial pressure.

METHODS

Forty patients received lumbar epidural catheters. Patients were randomized to receive either 10 ml 0.5% bupivacaine or 10 ml 0.25% bupivacaine. PI in the toe, mean arterial pressure (MAP) and toe temperature were all assessed at baseline and at 5, 10 and 20 min following epidural anesthesia. The effect of epidural anesthesia over time was assessed by repeated measures analysis of variance. Additionally, we defined clinically evident sympathectomy criteria (a 100% increase in the PI, a 15% decrease in MAP and a 1 degrees C increase in toe temperature). The numbers of patients demonstrating these changes for each test were compared using the McNemar test for each time point.

RESULTS

Twenty-nine subjects had photoplethysmography signals that met a priori signal quality criteria for analysis. By 20 min, PI increased by 326%, compared with a 10% decrease and a 3% increase in MAP and toe temperature, respectively. For PI 15/29, 26/29 and 29/29 of the subjects met the sympathectomy criteria at 5, 10 and 20 min, respectively, compared with 4/29, 6/29 and 18/29 for MAP changes and 3/29, 8/29 and 14/29 for toe temperature changes.

CONCLUSIONS

PI was an earlier, clearer and more sensitive indicator of the development of epidural-induced sympathectomy than either skin temperature or MAP.

Combination of different noninvasive measuring techniques: a new approach to increase accuracy of peripheral near infrared spectroscopy

One of the problems of near-infrared-spectroscopy (NIRS) measurements is low reproducibility. The aim of the present study was to introduce quality criteria to increase reproducibility of peripheral NIRS measurements. In a prospective cohort study in 40 neonates, repeated NIRS measurements were performed on the calf. During five "reapplication" periods (of NIRS optodes), five "measurements" (venous occlusions) were performed. Tissue oxygenation index (TOI), mixed venous oxygenation (SvO2), fractional oxygen extraction (FOE), hemoglobin flow (Hbflow), oxygen delivery (DO2), and oxygen consumption (VO2) were assessed. Measurements with linear changes during venous occlusions were included for further analysis (first quality criterion: R(2)>0.95). The second quality criterion was the equation 0 < or = TOI-SvO2 < or = (SaO2-SvO2)x0.2. Variance components and mean standard deviations were analyzed after introduction of the quality criteria. Variance components of reapplication and measurement decreased after introduction of the second quality criterion (TOI: 46.6-35.0%, SvO2: 76.8-38.2%, FOE: 73.1-37.5%, Hbflow: 70.3-51.9%, DO2: 71.5-52.7%, and VO2: 70.9-63.8%). Mean standard deviations of TOI (6.6+/-3.0 to 4.7+/-3.2%), SvO2 (11.1+/-4.8 to 5.7+/-3.9%), FOE (11.3+/-4.8 to 5.9+/-4.0%), Hbflow (4.3+/-2.0 to 2.9+/-1.6 micromol100 mLmin), and DO2 (17.8+/-7.6 to 11.4+/-6.2 micromol100 mLmin) decreased significantly, too. Only 12% of measurements fulfilled both quality criteria. With the introduction of two quality criteria, test-retest variability of peripheral NIRS measurements decreased significantly and reproducibility increased significantly.

Maternal pulse oximetry perfusion index as a predictor of early adverse respiratory neonatal outcome after elective cesarean delivery

OBJECTIVE

Evidence suggests increased morbidity, in particular early neonatal respiratory complications, in newborns from elective cesarean section compared with those from vaginal delivery. No reliable maternal predictors of adverse neonatal outcome at elective cesarean section are known. Here, we prospectively tested the hypothesis that a low maternal perfusion index at the baseline phase (i.e., preanesthesia) of the elective cesarean section is a predictor of early adverse neonatal respiratory outcome.

DESIGN

Prospective cohort study.

SETTING

Operating and delivery rooms of a public health hospital with a tertiary-level neonatal intensive care unit.

PATIENTS

Forty-four healthy pregnant women with no known risk factors undergoing elective cesarean section at term gestation.

INTERVENTIONS

Elective cesarean section was divided into nine phases. Analysis of pulse oximetry-derived signals (perfusion index, pulse rate, and oximetry) and systolic, diastolic, and differential blood pressure were recorded. Maternal arterial and venous newborn cord blood gas analyses and placental histology were evaluated.

MEASUREMENTS AND MAIN RESULTS

Early respiratory complications (transient tachypnea of the newborn, n = 5; respiratory distress syndrome, n = 1) were observed in 13.6% (6 of 44) of the newborns. A maternal perfusion index < or = 1.9 (lower quartile) during the preanesthesia phase of the elective cesarean section was an independent predictor of early adverse neonatal respiratory outcome (odds ratio 68.0, 95% confidence interval 6.02-767.72; p < .0001).

CONCLUSIONS

A decreased perfusion index value in the preanesthesia phase of elective cesarean section is a maternal predictor of increased neonatal morbidity and is significantly related to subclinical placental inflammatory disease. These observations suggest the feasibility of a noninvasive pulse oximeter prenatal screening of the high-risk fetus/newborn in elective cesarean section.

Early versus late cord clamping: effects on peripheral blood flow and cardiac function in term infants

BACKGROUND

In the debate on the best cord clamping time in newborn infants, we hypothesized that late cord clamping enables an increased volemia due to blood transfer to the newborn from the placenta.

AIM

To assess whether clamping time can affect limb perfusion and heart hemodynamics in a group of 22 healthy term newborn infants.

STUDY DESIGN

A case-control study.

SUBJECTS

Eleven early-clamped (at 30 s) vaginally-delivered newborn infants were compared with eleven late-clamped (at 4 min) newborns.

OUTCOME MEASURES

The two groups were studied using near-infrared spectroscopy and M-mode echocardiography.

RESULTS

Late cord clamping coincided with a higher hematocrit (median 62% versus 54%) and hemoglobin concentration (median 17.2 versus 15 g/dL), whilst there were no changes in bilirubin level. Echocardiography showed a larger end-diastolic left ventricle diameter (1.7 cm median value versus 1.5) coupled with unvaried shortening and ejection fraction values. There were no changes in calf blood flow, oxygen delivery, oxygen consumption or fractional oxygen extraction calculated from the NIRS measurements, or in foot perfusion index.

CONCLUSIONS

Our results demonstrated that late cord clamping coincides with an increased placental transfusion, expressed by higher hematocrit and hemoglobin values, and larger left ventricle diameter at the end of the diastole, with no changes in peripheral perfusion or oxygen metabolism.

Near-infrared spectroscopy/imaging for monitoring muscle oxygenation and oxidative metabolism in healthy and diseased humans

Near-infrared spectroscopy (NIRS) was initiated in 1977 by Jobsis as a simple, noninvasive method for measuring the presence of oxygen in muscle and other tissues in vivo. This review honoring Jobsis highlights the progress that has been made in developing and adapting NIRS and NIR imaging (NIRI) technologies for evaluating skeletal muscle O(2) dynamics and oxidative energy metabolism. Development of NIRS/NIRI technologies has included novel approaches to quantification of the signal, as well as the addition of multiple source detector pairs for imaging. Adaptation of NIRS technology has focused on the validity and reliability of NIRS measurements. NIRS measurements have been extended to resting, ischemic, localized exercise, and whole body exercise conditions. In addition, NIRS technology has been applied to the study of a number of chronic health conditions, including patients with chronic heart failure, peripheral vascular disease, chronic obstructive pulmonary disease, varying muscle diseases, spinal cord injury, and renal failure. As NIRS technology continues to evolve, the study of skeletal muscle function with NIRS first illuminated by Jobsis continues to be bright.