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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. [ABSTRACT FROM AUTHOR]

Pain is a common and undertreated problem in critically ill patients. Pain assessment in critically ill patients is challenging and relies on complex scoring systems. The aim of this work was to find out the possible role of the perfusion index (PI) measured by a pulse oximeter (Masimo Radical 7; Masimo Corp., Irvine, CA, USA) in pain assessment in critically ill patients. A prospective observational study was carried out on 87 sedated non-intubated patients in a surgical intensive care unit. In addition to routine monitoring, a Masimo pulse oximeter probe was used for PI measurement. The sedation level of the patients was assessed by using the Richmond Agitation-Sedation Scale (RASS). The pain intensity was determined by applying the behavioral pain scale for non-intubated (BPS-NI) patients. The PI, arterial blood pressure, heart rate, RASS, and BPS-NI values before and after the application of a standard painful stimulus (changing the patient position) were reported. Correlation between the PI and other variables was carried out at the two measurements. Correlation between changes in the PI (delta PI) and in the hemodynamic variables, RASS, and BPS-NI was also done. Changing the patient position resulted in a significant increase in SBP (128 ± 20 vs 120.4 ± 20.6, P = 0.009), DBP (71.3 ± 11.2 vs 68.7 ± 11.3, P = 0.021), heart rate (99.5 ± 19 vs 92.7 ± 18.2, P = 0.013), and BPS-NI (7[6-8] vs 3[3-3], P < 0.001) values and a significant decrease in the PI (1[0.5-1.9] vs 2.2[0.97-3.6], P < 0.001) value compared to the baseline readings. There was no correlation between the values of the PI and the ABP, BPS-NI, and RASS at the two measurements. A good correlation was found between the delta PI and delta BPS-NI (r = -0.616, P < 0.001). A weak correlation was observed between the PI and heart rate after the patient positioning (r = -0.249, P < 0.02). In surgical critically ill non-intubated patients, the application of a painful stimulus was associated with decreased PI. There was a good correlation between the change in the PI and the change in BPS-NI values after the application of painful stimulus. [ABSTRACT FROM AUTHOR]

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Perfusion index (PI) is a non-invasive marker of peripheral perfusion which is detected by an oximeter. We aimed to assess the correlation between PI and left ventricular output (LVO) in healthy term infants at the time of the screening for congenital heart disease (CHD). PI was measured at 48±2 h of life in the infant's right hand (PIrh) and in one foot (PIf) contemporary to SpO2 for CHD screening. Heart ultrasound was performed immediately after the screening procedure for measuring LVO. Forty-nine healthy term infants were studied. PIrh and PIf were 1.9 ± 0.6 and 1.9 ± 0.8, respectively, and their values were significantly correlated (p < 0.0001) with a coefficient r = 0.8. Bland-Altman analysis shows a mean difference of -0.06 ± 0.47 (95%LOA -0.98-0.86). PIrh correlates with LVO (r = 0.68) and LVO/kg (r = 0.61) with an increase of 151 mL/min (95%CI 103-198) of LVO and 42 mL/kg/min (95%CI 26-58) of LVO/kg per point of PIrh. PIf correlates with LVO (r = 0.74) and LVO/kg (r = 0.73) with an increase of 123 mL/min (95%CI 90-155) of LVO and 37 mL/kg/min (95%CI 27-47) of LVO/kg per point of PIf.Conclusion: PI is significantly correlated with LVO in healthy term infants. These results support the theoretical potential role of PI in the CHD screening. What is Known: • Perfusion index is an indirect measure of perfusion which depends on cardiac output and peripheral vascular resistance whose normal values have been documented in term and preterm infants in the first days of life. • Perfusion index has been proposed for the screening of congenital heart disease with duct-dependent systemic circulation in term infants. What is New: • Perfusion index shows a significant correlation with the left ventricular output in term infants at the moment of the screening for congenital heart disease. • Perfusion index might have a theoretical role in improving the accuracy of pulse oximetry in the screening of CHD associated to low systemic flow. [ABSTRACT FROM AUTHOR]

Aim: Early hemodynamic assessment of global parameters in critically ill newborns fails and requires mostly invasive measurements in neonatal intensive care unit. Clinical signs are frequently used for assessment of peripheral perfusion. Perfusion index (PI) is a new noninvasive numerical value of peripheral perfusion. Serum lactate levels and PI are the indicators that are important in determining prognosis of preterm infants. In this study, we aimed to investigate the relationship of serum lactate levels and PI with mortality and morbidity in very low-birth weight infants (VLBW).Study Design: This study was conducted between July 2014 and July 2015 in a Level III NICU. The study enrolled preterm infants with a gestational age ≤ 32 weeks, birth weight ≤ 1500 g. Serum lactate levels from blood gases and PI, SpO2 measurements were recorded at 1st, 12th and 24th hours by using a new generation pulse-oximeter. Morbidities and mortalities were documented.Results: A total of 60 VLBW infants were enrolled the study. Mean birth weight and gestational age were 991 ± 288 g and 27.5 ± 2.5 w, respectively. Retinopathy of prematurity (ROP) was significantly higher in the patients with high lactate levels (>4 mg/dl) at 1st hour and low-PI levels (<0.5) at 12th hour of life (p = 0.042, p = 0.015), respectively. Bronchopulmonary displasia (BPD) was significantly higher in the patients with low PI (< 0.5) at 1st hour. Lactate and PI values were not significantly correlated with necrotizing enterocolitis, intraventricular hemorrhage, patent ductus arteriosus, sepsis and mortality.Conclusion: High lactate levels (> 4 mg/dl) and low PI (< 0.5) could be used as early parameters for prediction of ROP and BPD. This data suggests that in VLBW infants lactate levels and PI parameters during the first 24 h will be effective in determining the prognosis of the disease. We believe that larger, randomized controlled clinical trials are likely to establish the true benefit. [ABSTRACT FROM AUTHOR]

Purpose: Several factors affect the accuracy of non-invasive continuous hemoglobin concentration (SpHb) measurements. We had previously shown an increase in the perfusion index (PI) following induction of anesthesia which was associated with an increase in the difference between SpHb and total hemoglobin (tHb) (SpHb-tHb). We hypothesized that blunting the increase in PI by maintaining blood pressure during induction of anesthesia would improve the agreement between SpHb and tHb measurements. Methods: Twenty-nine adult patients were enrolled. Patients were randomly assigned by use of sequentially numbered, opaque sealed envelopes to a control (group C) or a phenylephrine group (group P). Anesthesia was induced and maintained with propofol, remifentanil, and ketamine. In group P, phenylephrine was infused at 0.5 µg/kg/min during induction of anesthesia. SpHb and PI were monitored with a Radical-7 Pulse CO-Oximeter. tHb and hematocrit were measured with the ABL800 blood gas analyzer. Results: Following induction of anesthesia, PI increased significantly in both groups ( p < 0.001 and p < 0.05 in groups C and P, respectively). However, the increase in PI was significantly smaller in group P than in group C (2.6 ± 1.3 vs 0.8 ± 1.4%, p < 0.001). Similarly, the change in SpHb-tHb was significantly smaller in group P than in group C (0.40 ± 0.78 vs 0.97 ± 0.70 g/dl, p < 0.05). Changes in SpHb-tHb are correlated with changes in PI ( r = 0.46, p < 0.05). Conclusions: The findings suggest that blunting the increase in PI by maintaining arterial pressure during induction of anesthesia improves the agreement between SpHb and tHb values. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Postoperative pain (POP) occurs following the trauma caused by surgery, and its management depends mostly on timely and accurate assessment. Since traditional POP assessment tools rely on the patient's ability to communicate pain intensity, there is a need for alternative approaches that can be used even when the patient cannot provide the self-report. Some indexes derived from photoplethysmographic (PPG) waveform analysis, such as Surgical Pleth Index (SPI) and Perfusion Index (PI), have shown some promise during surgery. However, their usefulness in postoperative scenarios remains controversial. To provide possible explanations for this issue and a foundation for future research, we examined the current state-of-the-art devoted to exploring the potential value of PPG-derived indexes in POP assessment. After critically reviewing the related literature, we identified several challenges at the conceptual and methodological levels, including an incomplete understanding of the POP experience, an inaccurate interpretation of the results provided by statistical tools, and a lack of validity protocol standards. As PPG-derived indexes could still be valuable for developing objective and valid tools to assess pain after surgery, it is necessary to clarify how those metrics might contribute to POP conceptualization, assessment, and management. The uniqueness of the pain experienced in the post-anesthesia care unit must also be recognized by both researchers and clinicians. [ABSTRACT FROM AUTHOR]

Brain computed tomography (CT) perfusion is a technique that allows for the fast evaluation of cerebral hemodynamics. However, quantitative studies of brain CT perfusion in veterinary medicine are lacking. The purpose of this study was to investigate the normal range of perfusion determined via CT in brains of healthy dogs and to compare values between white matter and gray matter, differences in aging, and each hemisphere. Nine intact male beagle dogs were prospectively examined using dynamic CT scanning and post-processing for brain perfusion. Regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), mean transit time, and time to peak were calculated. Tissue ROIs were drawn in the gray matter and white matter of the frontal, temporal, parietal, and occipital lobes; caudate nucleus; thalamus; piriform lobe; hippocampus; and cerebellum. Significant differences were observed between the white matter regions and gray matter regions for rCBV and rCBF ( p < 0.05). However, no significant differences were identified between hemispheres and between young and old groups in brain regions. The findings obtained in this study involving healthy beagle dogs might serve as a reference for regional CT perfusion values in specific brain regions. These results may aid in the characterization of various brain diseases in dogs.

Regional anesthesia (RA) is a common and irreplaceable technique in clinical, which can be used in different surgery sites and control of acute and chronic pain, especially for outpatients, pediatrics and the elderly. RA demands are increasing during COVID-19 pandemic because many surgeries could be performed under RA to reduce the risk of cross-infection between patients and health care workers. Early and accurate identification of the effects of RA can help physicians make timely decisions about whether to supplement analgesics or switch to general anesthesia, which will save time and improve patient satisfaction in a busy operating room. Perfusion index (PI) is a parameter derived from photoplethysmography (PPG) and represents the ratio of pulsatile and non-pulsatile blood flow at monitoring sites. It reflects local perfusion and is mainly affected by stroke volume and vascular tone. With characteristics of non-invasive, rapid, simple, and objective, PI is widely used in clinical practice, such as fluid responsiveness prediction, nociceptive assessment, etc. Recently, many studies have assessed the accuracy of PI in early prediction of RA success, including brachial plexus block, sciatic nerve block, neuraxial anesthesia, paravertebral block, caudal block and stellate ganglion block. Successful RA often parallels increased PI. In this narrative review, we describe the principles and influencing factors of PI, and introduce the effects of PI on early identification of RA effectiveness.

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.

(1) Background: The renal microcirculation is essential to maintain the renal function, but its determinants in humans have been poorly studied. Contrast-enhanced ultrasound (CEUS) allows the non-invasive quantification of the cortical micro-perfusion at the bedside using the perfusion index (PI). The aims of this study were to assess whether differences exist in PI between healthy males and females and to identify clinical determinants associated with cortical micro-perfusion. (2) Methods: Healthy, normotensive volunteers (eGFR > 60 mL/min/1.73 m 2 , no albuminuria) underwent CEUS under standardized conditions with the destruction-reperfusion (DR) technique. The mean PI of four DR sequences was reported as the primary outcome measure (3) Results: A total of 115 subjects (77 females and 38 males) completed the study; the mean ± SD age was, respectively, 37.1 ± 12.2 and 37.1 ± 12.7 years in females and males, and the mean eGFR was 105.9 ± 15.1 and 91.0 ± 17.4 mL/min/1.73 m 2 . The PI (median) was higher in females than in males, i.e., 2705 (IQR 1641-3777) vs. 1965 (IQR 1294-3346) arbitrary units (a.u), p = 0.02). A correlation analysis showed positive associations between PI and eGFR, female sex, heart rate, plasma renin activity (PRA) and plasma aldosterone concentrations (PAC), negative associations with potassium, bicarbonate and systolic blood pressure, and no associations with age, body mass index and renal resistive index (RRI). In a multivariate linear regression analysis, only PRA remained significantly associated with PI. (4) Conclusions: Although the PI was higher among females, this association was no longer significant after adjustment for covariates. There was no difference in females tested during the follicular or the luteal phases. In conclusion, the PI was only weakly influenced by classic clinical variables, but was positively associated with PRA, suggesting that the renin-angiotensin system plays a role in the regulation of the cortical micro-perfusion in humans. Identifying which other factors contribute to the large variations in micro-perfusion across individuals needs further study.

Background: This study was performed to compare the perfusion index (PI) between affected and unaffected limbs in patients with complex regional pain syndrome (CRPS); it also evaluated the usefulness of the PI for monitoring the response to intravenous ketamine infusion therapy in such patients., Methods: In total, 46 patients with CRPS in one arm or leg were enrolled in this study. The PIs of the unaffected (PI Control ) and affected (PI CRPS ) limbs were simultaneously evaluated before and after treatment., Results: PI CRPS was significantly lower than PI Control at all time points. The change in PI from immediately before to 30 min after intravenous ketamine infusion therapy (T Before and T 30 min , respectively) in the affected limb was significantly correlated with the change in visual analog pain scale (VAS) between the two time points (r = 0.646, p < 0.001). The area under the curve for the changes in VAS and PI CRPS between T Before and T 30 min was 0.928. The optimal threshold value for the change in PI CRPS between T Before and T 30 min , to distinguish responders with a ≥ 50-point reduction in VAS score from nonresponders, was 22.60% with a sensitivity of 0.811 (95% CI: 0.774-0.848) and a specificity of 0.889 (95% CI: 0.848-0.930). Thirty-one patients showed a ≥ 50-point reduction in VAS score [67% (95% CI: 54%-80%)] and 15 patients showed a < 50-point reduction in VAS score [33% (95% CI: 20%-46%)]. Thirty patients showed an increased PI ≥ 22.60% [65% (95% CI: 50%-78%)] and 16 patients showed an increased PI < 22.60% [35% (95% CI: 22%-50%)]. Twenty-seven patients had a ≥ 50-point reduction in VAS score and an increased PI ≥ 22.60% [59% (95% CI: 44%-74%)]. Eleven patients had shown a < 50-point pain reduction in VAS score and increased PI < 22.60% [24% (95% CI: 13%-37%)]., Conclusion: The PI significantly differed between affected and unaffected limbs in patients with CRPS. The PI may be useful for monitoring the response to intravenous ketamine therapy in patients with CRPS., (© 2023 World Institute of Pain.)

Background: Dexmedetomidine, one of the sedatives, has an analgesic effect. We aimed to investigate postoperative analgesia with dexmedetomidine as adjuvants for procedural sedation using perfusion index (PI)., Methods: In this prospective, randomized, case-control, observational study, 72 adult patients, 19-70 years, who were scheduled for chemoport insertion under monitored anesthesia care were performed. According to the group assignment, remifentanil or dexmedetomidine was simultaneously infused with propofol. The primary outcome was PI 30 min after admission to the post anesthesia care unit (PACU). And, pain severity using numerical rating scale (NRS) score and the relationship between NRS score and PI were investigated., Results: During PACU staying, PI values were significantly different between the two groups PI values at 30 min after admission to the PACU were 1.3 (0.9-2.0) in the remifentanil group and 4.5 (2.9-6.8) in the dexmedetomidine group (median difference, 3; 95% CI, 2.1 to 4.2; P < 0.001). The NRS scores at 30 min after admission to the PACU were significantly lower in the dexmedetomidine group (P = 0.002). However, there was a weak positive correlation between NRS score and PI in the PACU (correlation coefficient, 0.188; P = 0.01)., Conclusion: We could not find a significant correlation between PI and NRS score for postoperative pain control. Using PI as a single indicator of pain is insufficient., Trial Registration: Clinical Trial Registry of Korea, https://cris.nih.go.kr : KCT0003501, the date of registration: 13/02/2019., (© 2023. The Author(s).)

Background: The relationship between perfusion index (PI) and organ dysfunction in patients in the intensive care unit (ICU) is not clear. This study aimed to explore the relationship between PI and renal function in the perioperative critical care setting and evaluate the predictive efficiency of PI on patients with acute kidney injury (AKI) in the ICU., Methods: This retrospective analysis involved 12,979 patients who had undergone an operation and were admitted to the ICU in Peking Union Medical College Hospital from January 2014 to December 2019. The distribution of average PI in the first 24 h after ICU admission and its correlation with AKI was calculated by Cox regression. Receiver operating characteristic (ROC) curves were generated to compare the ability of PI, mean arterial pressure (MAP), creatinine, blood urea nitrogen (BUN), and central venous pressure (CVP) to discriminate AKI in the first 48 h in all perioperative critically ill patients., Results: Average PI in the first 24 h served as an independent protective factor of AKI (Odds ratio [OR]=0.786, 95% confidence interval [CI]: 0.704-0.873, P <0.0001). With a decrease in PI by one unit, the incidence of AKI increased 1.74 times. Among the variables explored for the prediction of AKI (PI, MAP, creatine, BUN, and CVP), PI yielded the highest area under the ROC curve, with a sensitivity of 64.34% and specificity of 70.14%. A cut-off value of PI ≤2.12 could be used to predict AKI according to the Youden index. Moreover, patients in the low PI group (PI ≤2.12) exhibited a marked creatine elevation at 24-48 h with a slower decrease compared with those in the high PI group (PI >2.12)., Conclusions: As a local blood flow indicator, the initial 24-h average PI for perioperative critically ill patients can predict AKI during their first 120 h in the ICU., (© 2023 The Author(s).)

Objective: To study the correlation of objective parameters for diagnosing shock viz., perfusion index (PI), plethysmography variability index (PVI) and serum lactate (SL) with invasive blood pressure in late preterm and term infants with shock., Methods: Prospective observational study (diagnostic test) conducted at the neonatal intensive care unit of Kanchi Kamakoti CHILDS Trust Hospital, Chennai between June, 2018 and May, 2020. Term and late preterm neonates with shock were included in the study. PI, PVI, SL, SpO2 and heart rate were monitored. PI, PVI and SLL were recorded at 0,12, 24 and 72 hours of onset of shock. All the babies were followed up till discharge or death., Results: Total 78 neonates were enrolled in the study. At 0 hour, SL and PVI had negative correlation (P =0.002 and P=0.003) while PI had a weak-to-moderate positive correlation (P=0.002) with invasive blood pressure. SL ≥4.65 had a sensitivity of 75% and specificity of 75.8%, and PI <0.455 had a sensitivity of 65%, and specificity of 58.6% for predicting invasive hypotension. PVI ≥23.5 had a sensitivity of 90% and specificity of 63.8% in predicting invasive hypotension., Conclusion: PI has moderate positive correlation while SL and PVI have moderate negative correlation with invasive blood pressure. The cutoff values of SL ≥4.65, PI <0.45 and PVI ≥23.5 can predict invasive hypotension with good sensitivity and negative predictive value.

Objective: To observe the correlation between the four limbs perfusion index (PI) and blood lactic acid in patients with neurosis, and evaluate the predictive value of PI on microcirculation perfusion metabolic disorder in patients with neurosis., Methods: A prospective observational study was conducted. Adult patients admitted to the department of neurological intensive care unit (NICU) of the First Affiliated Hospital of Xinjiang Medical University from July 1 to August 20 in 2020 were enrolled. Under the condition of indoor temperature controlled at 25 centigrade, all patients were placed in the supine position, and the blood pressure, heart rate, PI of both fingers and thumb toes and arterial blood lactic acid were measured within 24 hours and 24-48 hours after NICU. The difference of four limbs PI at different time periods and its correlation with lactic acid were compared. Receiver operator characteristic curve (ROC curve) was used to evaluate the predictive value of four limbs PI on patients with microcirculatory perfusion metabolic disorder., Results: A total of 44 patients with neurosis were enrolled, including 28 males and 16 females; average age (61.2±16.5) years old. There were no significant differences in PI of the left index finger and the right index finger [2.57 (1.44, 4.79) vs. 2.70 (1.25, 5.33)], PI of the left toe and the right toe [2.09 (0.85, 4.76) vs. 1.88 (0.74, 4.32)] within 24 hours after entering the NICU, and the PI of the left index finger and the right index finger [3.17 (1.49, 5.07) vs. 3.14 (1.33, 5.36)], PI of the left toe and the right toe [2.07 (0.75, 5.20) vs. 2.07 (0.68, 4.67)] at 24-48 hours after NICU admission (all P > 0.05). However, compared to the PI of the upper and lower limbs on the same side, except for the 24-48 hours after ICU of the PI difference between the left index finger and the left toe (P > 0.05), the PI of the toe was lower than that of the index finger at the other time periods (all P < 0.05). The correlation analysis showed that the PI value of four limbs of patients in both time periods were significantly negatively correlated with arterial blood lactic acid (the r values of the left index finger, the right index finger, the left toe and the right toe were -0.549, -0.482, -0.392 and -0.343 respectively within 24 hours after entering the NICU; the r values of the left index finger, the right index finger, the left toe and the right toe were -0.331, -0.292, -0.402 and -0.442 respectively after entering the NICU 24-48 hours, all P < 0.05). Taking lactic acid ≥ 2 mmol/L as the diagnostic standard for metabolic disorder of microcirculation perfusion (total 27 times, accounting for 30.7%). The efficacy of four limbs PI in predicting microcirculation perfusion metabolic disorder were compared. ROC curve analysis showed that the area under the curve (AUC) and 95% confidence interval (95%CI) of left index finger, right index finger, left toe and right toe predicting microcirculation perfusion metabolic disorder were 0.729 (0.609-0.850), 0.767 (0.662-0.871), 0.722 (0.609-0.835), 0.718 (0.593-0.842), respectively. There was no significant difference in AUC compare with each other (all P > 0.05). The cut-off value of PI of right index finger for predicting microcirculation perfusion metabolic disorder was 2.46, the sensitivity was 70.4%, the specificity was 75.4%, the positive likelihood ratio was 2.86, and the negative likelihood ratio was 0.30., Conclusions: There are no significant differences in PI of bilateral index fingers, bilateral toes in patients with neurosis. However, unilateral upper and lower limbs showed lower PI in the toe than in the index finger. There is a significantly negatively correlation between PI and arterial blood lactic acid in all four limbs. PI can predict the metabolic disorder of microcirculation perfusion, and its cut-off value is 2.46.

The results of the pinprick and cold tests performed on the arm, forearm, and wrist-wrist areas of patients scheduled for upper extremity procedures are subjective and dependent on patient's compliance. The purpose of this study was to determine whether the perfusion index (PI) could be used as an objective indicator to demonstrate block efficacy. Fifty patients between the ages of 18 and 65 years who were scheduled for upper extremity procedures and had an American Society of Anesthesiologists risk assessment class of I-II were included in this study. Infraclavicular block was performed on the patients using the peripheral nerve stimulation and ultrasonography. Preoperative and postoperative PI values were measured and recorded. The pinprick test took an average of 7.98 ± 1.49 minutes to turn positive, whereas the grade 3 of Modified Bromage Scale took an average of 11.08 ± 1.71 minutes. Differences between baseline values and perioperative values were found to be significantly different in the paired comparisons of the PI values. With 80% sensitivity and 80% specificity, increases in the PI value by or above 3.8 units were indicative for sensory block. With 84% sensitivity and 84% specificity, increases in the PI value by or above 3.9 units were indicative for grade 3 of Modified Bromage Scale in patients. It was determined that the PI is a faster, more reliable, and simpler technique than conventional methods for determining the efficacy of a block because of the vasodilatation that occurs before sensory and motor block.

Background: Peripheral vasodilation is a well-recognized side effect of general anesthesia, and induces changes in the amplitude of the pulse plethysmograph (PPG) waveform. This can be continuously quantitaed using the Perfusion Index (PI), a ratio of the pulsatile to nonpulsatile signal amplitude in the PPG waveform. We hypothesized that the perfusion index would rise with the induction of anesthesia in children, and fall with emergence, and performed a prospective, observational study to test this. Aim: Our primary aim was to test whether the different clinical stages of anesthesia were associated with changes in the perfusion index, and the secondary aim was to test the correlation between the normalized perfusion index and the MAC value. Methods: Twenty-one patients between the ages of 1 and 18 undergoing minor procedures with no anticipated painful stimuli were recruited. Patients with significant illnesses were excluded. Data collection commenced with a preinduction baseline, and data were collected continuously, with event marking, until completion of the anesthesia and removal of the pulse oximeter. Data collected included perfusion index, heart rate, and anesthetic gas concentration values. A normalized perfusion index was calculated by subtracting the initial baseline perfusion index value from all perfusion index values, allowing changes, from a standardized initial baseline value of zero, to be analyzed. Results: During induction, the mean normalized perfusion index rose from 0.0 to 4.2, and then declined to 0.470 when the patients returned to consciousness. P < 0.001 using repeated measures ANOVA test. The normalized perfusion index was correlated with MAC values (r2 = 0.33, 95% CI 0.18–0.47, P < 0.01). Conclusion: The perfusion index changed significantly during different stages of anesthesia. There is a significant correlation between the perfusion index, measured by pulse oximetry, and the MAC value, in pediatric patients undergoing minor procedures. [ABSTRACT FROM AUTHOR]

Objectives To evaluate perfusion index ( PI) as a determinant of regional nerve block success following sciatic nerve blockade with bupivacaine in dogs undergoing stifle surgery. Study design Prospective clinical trial. Animals Ten adult dogs, aged 5.6 ± 2.6 years and weighing 36.9 ± 16.8 kg, undergoing a tibial plateau leveling osteotomy. Methods Dogs were premedicated with acepromazine (0.03 mg kg−1) and hydromorphone (0.1 mg kg−1) intramuscularly, and anesthetized with propofol (up to 4 mg kg−1) intravenously and isoflurane in oxygen. An ultrasound-guided femoral and sciatic (F+S) nerve block was performed on the surgical limb with bupivacaine (0.75%), 0.2 mL kg−1 at the femoral site and 0.3 mL kg−1 at the sciatic site, with a maximum volume of 10 mL per site. Physiological variables were recorded every 5 minutes throughout anesthesia. A pulse co-oximeter probe was placed between the third and fourth digits of both pelvic limbs, and the PI was recorded 5 minutes before infiltration with bupivacaine, immediately afterwards, and every 5 minutes for 30 minutes. Motor nerve conduction velocity ( MNCV) of the sciatic nerve was performed on the surgical limb 5 minutes before and 20 minutes after bupivacaine administration to confirm nerve block. Results The PI of the surgical limb was significantly greater than the contralateral pelvic limb at 10 minutes ( p = 0.03) and 15 minutes ( p < 0.01) after F+S nerve blockade. The MNCV performed after sciatic nerve blockade revealed a functional motor blockade for all dogs. There were no significant changes in physiological variables. Conclusions and clinical relevance The PI provided a reliable indication of successful sciatic nerve blockade in the clinical patients in this study. No increase in the PI by 15 minutes after bupivacaine administration around the sciatic nerve could indicate partial or total failure of anesthetic blockade. [ABSTRACT FROM AUTHOR]

Background: Perfusion index (PI) is a non-invasive numerical value of peripheral perfusion obtained from a pulse oximeter. In this study, we evaluated the efficacy of PI for detecting haemodynamic stress responses to insertion of i-gel, laryngeal mask airway (LMA) and endotracheal tube and compare, its reliability with the conventional haemodynamic criteria in adults during general anaesthesia. Methods: Sixty patients scheduled for elective general surgery under general anaesthesia were randomised to three groups. (i-gel, LMA and ET groups ( n=20/group). Heart rate (HR) (positive if ≥10 bpm), systolic blood pressure (SBP), diastolic blood pressure (DBP) (positive if ≥15 mm Hg) and PI (positive if ≤10%) were monitored for 5 min after insertion. Main outcome measures: SBP, DBP, HR and PI were measured before induction of anaesthesia and before and after insertion of the airway device. Results: Insertion of airway devices produced significant increases in HR, SBP and DBP in LMA and ET groups. Moreover, PI was decreased significantly by 40%, 100% and 100% in the three groups. Using the PI criterion, the sensitivity was 100% (CI 82.4-100.0%). Regarding the SBP and DBP criterions, the sensitivity was 44.4% (CI 24.6-66.3%), 55.6% (CI 33.7-75.4%) respectively. Also, significant change in the mean PI over time (from pre-insertion value to the 1 st min, 3 rd min, until the 4 th min after insertion without regard the device type), ( P

Background: The pleth variability index (PVI), which is calculated from respiratory variations in the perfusion index (PI), has been shown to predict fluid responsiveness in mechanically ventilated patients; however, vasomotor tone changes induced by hypercapnia can affect PI and hence may slim down the accuracy of PVI. This study was designed to find out the impact of mild hypercapnia on PVI. Methods: A total of 30 patients were randomized after induction of general anesthesia with target controlled infusion propofol and remifentanil to either hypercapnia, (etCO 2 =45 mmHg), (group 1, 15 patients) or normocapnia (etCO 2 =35 mmHg) (group 2, 15 patients). After a stabilization period of 10 min, patients were crossed over to the other intentional level of etCO 2 . Heart rate (HR), mean arterial pressure (MAP), PI, PVI were collected at the end of each stabilization period. Results: Patient characteristics and baseline values of HR, MAP, PI and PVI were comparable between the groups. Carryover effect was statistically excluded. Hypercapnia significantly increased PI and decreased PVI with significant negative correlation. Conclusion: Hypercapnia retracts back PVI values compared with normocapnia. Precise judgment of fluid responsiveness as indicated by PVI necessitates its comparison against similar etCO 2 levels.