The Peripheral Perfusion Index tracks systemic haemodynamics during general anaesthesia

Role of the peripheral perfusion index in children with bronchial asthma

OBJECTIVE

Peripheral perfusion index (PI) is noninvasive method measuring peripheral blood volume in numerical form and indicating perfusion status. In this study, we have investigated whether the relationship between the measurements of PI and definition of bronchial asthma exacerbation classification and treatment.

METHODS

This prospective study included in aged 5-12 years children applied to the hospital between January 2020 and June 2020. They were divided into two groups as patients who presented bronchial asthma symptoms and the control group who were selected as children applied to the hospital for routine healthy child follow-up. The severity of the asthma exacerbations was evaluated. Before administering nebulizer therapy, vital signs, oxygen hemoglobin saturation and PI values were recorded. Appropriate nebulizer treatment was initiated for the severity of exacerbation and subsequent changes in the PI values were recorded.

RESULTS

Pretreatment PI values were higher in children with asthma than those in healthy children (p = 0.001). The PI measurements of the patients for diagnosing asthma exacerbation showed a statistically significant area under the ROC curve (p = 0.001), and AUC (0.842) values of the 2.25 cutoff point of the PI value were sufficiently high. In the ROC analysis conducted to determine the need for hospitalization in patients presented with asthma exacerbations, the area under the curve was statistically significant (p = 0.020), and AUC (0.830) values of the 3.25 cutoff point of the PI value were sufficiently high.

CONCLUSIONS

The PI measured in patients presented with asthma symptoms may use a valuable parameter for the diagnosing of asthma exacerbations and making hospitalization decisions.

Perfusion Index Predicts the Effectiveness of Supraclavicular Brachial Plexus Block in Children Under General Anesthesia: A Randomized Controlled Trial

Objectives: This study aimed to assess the predictive value of perfusion index (PI) in determining the effectiveness of supraclavicular block (SCB) in children under sevoflurane or propofol general anesthesia. Methods: In this randomized controlled study, 104 children who underwent elective upper extremity surgery under sevoflurane or propofol anesthesia were scheduled to be enrolled. The primary outcome was the effects of PI in predicting the effectiveness of SCB under general anesthesia. The PI value was obtained through pulse oximetries. Secondary outcomes include hemodynamic data, supplementary opioid doses, agitation score, pain score, and postoperative complications. Results: A total of 103 pediatric patients were analyzed. PI increased rapidly after anesthesia induction, and there was no significant difference in PI in the blocked side between the propofol group (PRO group) and sevoflurane group (SEV group). At 10 min after the block, PI in the blocked side was higher than that in the unblocked side in both groups (p < 0.05). However, PI showed low sensitivity and specificity in predicting the effect of SCB at 10 min in both groups. At PACU, PI exhibited a high sensitivity (0.837 vs. 0.796) and specificity (0.721 vs. 0.898) for SCB at cutoff values of 5.91 and 6.67 in both PRO and SEV groups. The area under the receiver operating characteristic curve (AUROC) values were 0.834 (95% CI 0.750-0.918) and 0.895 (95% CI 0.832-0.959). Conclusion: PI demonstrates limited sensitivity and specificity in predicting the effect of SCB at 10 min after block under general anesthesia. However, PI may serve as a more appropriate indicator to guide the necessity for supplemental analgesia in PACU. Trial Registration: ClinicalTrials.gov identifier: NCT04216823.

Peripheral Perfusion Index for Prediction of Fluid Responsiveness in Spontaneously Breathing Critically Ill Patients: A Prospective Observational Study

Background

Peripheral perfusion index (PPI), measured via plethysmography using a pulse oximeter, provides noninvasive, continuous insights into peripheral circulation. This study evaluates PPI's potential as a predictive marker for fluid responsiveness in critically ill patients, aiming to reduce vasopressor use.

Methods

A 20-month prospective study was conducted in the multidisciplinary surgical ICU of Christian Medical College, Vellore. Patients meeting specific inclusion criteria were enrolled. Parameters including blood pressure, pulse pressure (PP), heart rate, left ventricular outflow tract velocity time integral (LVOT VTI), oxygen saturation, and PPI were recorded before and after a passive leg raise (PLR) test. Positive PLR responders received fluid resuscitation, and PPI changes were monitored at regular intervals. The study excluded patients with peripheral vascular disease, burns involving extremities, those on nitroglycerin or other vasodilator infusions, and those on high doses of vasopressors.

Results

A 39% increase in PPI was identified as the threshold for fluid responsiveness. Subgroup analysis revealed variability: trauma patients showed a 55% increase, obstetrics patients 41%, and postoperative patients 6%. Notably, the study found that spontaneous breathing and minimal vasopressor requirements enhanced the reliability of PPI as a fluid responsiveness marker.

Conclusion

Peripheral perfusion index is a reliable and practical tool for predicting fluid responsiveness in spontaneously breathing critically ill patients. It offers a noninvasive and dynamic method to guide volume resuscitation, particularly when combined with established hemodynamic markers such as LVOT VTI and PP changes. This study underscores the importance of using PPI in conjunction with other parameters for comprehensive fluid management. Further validation in larger and more diverse patient populations is warranted to confirm these findings and optimize resuscitation strategies.

How to cite this article

Narayanan BJ, Rao SV, Kandasamy S. Peripheral Perfusion Index for Prediction of Fluid Responsiveness in Spontaneously Breathing Critically Ill Patients: A Prospective Observational Study. Indian J Crit Care Med 2025;29(2):151-154.

Vasoconstriction with phenylephrine increases cardiac output in preload dependent patients

General Anaesthesia (GA) is accompanied by a marked decrease in sympathetic outflow and thus loss of vasomotor control of cardiac preload. The use of vasoconstriction during GA has mainly focused on maintaining blood pressure. Phenylephrine (PE) is a pure α1-agonist without inotropic effects widely used to correct intraoperative hypotension. The potential of PE for augmenting cardiac stroke volume (SV) and -output (CO) by venous recruitment is controversial and no human studies have explored the effects of PE in preload dependent circulation using indicator dilution technique. We hypothesized that PE-infusion in patients with cardiac stroke volume limited by reduced preload would restore preload and thus augment SV and CO. 20 patients undergoing GA for gastrointestinal surgery were monitored with arterial catheter and LiDCO unity monitor. Upon stable haemodynamics after induction patients were placed in head-up tilt (HUT). All patients became preload responsive as verified by a stroke volume variation (SVV) of > 12%. PE-infusion was then started at 15-20mikrg/min and adjusted until preload was restored (SVV < 12%). Li-dilution cardiac output (CO) was initially measured after induction (baseline), again with HUT in the preload responsive phase, and finally when preload was restored with infusion of PE.At baseline SVV was 10 ± 3% (mean ± st.dev.), CI was 2,6 ± 0,4 L/min*m2, and SVI 43 ± 7mL/m2. With HUT SVV was 19 ± 4%, CI was 2,2 ± 0,4 L/min*m2, SVI 35 ± 7mL/m2. During PE-infusion SVV was reduced to 6 ± 3%, CI increased to 2,6 ± 0,5 L/min*m2, and SVI increased to 49 ± 11mL/m2. All differences p < 0,001. In conclusion: Infusion of phenylephrine during preload dependency increased venous return abolishing preload dependency as evaluated by SVV and increased cardiac stroke volume and -output as measured by indicator-dilution technique. (ClinicalTrials.gov NCT05193097).

The Use of the Perfusion Index to Predict Post-Induction Hypotension in Patients Undergoing General Anesthesia: A Systematic Review and Meta-Analysis

Post-induction hypotension (PIH) is a common and potentially serious complication of general anesthesia. This meta-analysis (Prospero registration number: CRD42024566321) aimed to evaluate the predictive efficacy of the perfusion index (PI) for PIH in patients undergoing general anesthesia. A comprehensive literature search was performed using multiple electronic databases (Google Scholar, EMBASE, Cochrane Library, and MEDLINE). Studies involving adult patients undergoing general anesthesia, with the PI measured before anesthesia induction and reporting PIH incidence, were included. The primary outcome was the diagnostic accuracy of the PI in predicting the probability of PIH. The secondary outcome was the pooled PIH incidence. Eight studies with 678 patients were included. The pooled incidence of PIH was 44.8% (95% confidence interval [CI]: 29.9%-60.8%). The combined sensitivity and specificity of the PI for predicting PIH were 0.84 (95% CI: 0.65-0.94) and 0.82 (95% CI: 0.70-0.90), respectively. The summary receiver operating characteristic (sROC) analysis revealed an area under curve of 0.89 (95% CI: 0.86-0.92). The Deek's funnel plot asymmetry test indicated no significant publication bias. The PI demonstrates high predictive efficacy for PIH in patients undergoing general anesthesia, indicating that it can be a valuable tool for identifying those at risk of PIH.

Association between peripheral perfusion index and postoperative acute kidney injury in major noncardiac surgery patients receiving continuous vasopressors: a post hoc exploratory analysis of the VEGA-1 trial

BACKGROUND

The peripheral perfusion index is the ratio of pulsatile to nonpulsatile static blood flow obtained by photoplethysmography and reflects peripheral tissue perfusion. We investigated the association between intraoperative perfusion index and postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

METHODS

In this exploratory post hoc analysis of a pragmatic, cluster-randomised, multicentre trial, we obtained areas and cumulative times under various thresholds of perfusion index and investigated their association with acute kidney injury in multivariable logistic regression analyses. In secondary analyses, we investigated the association of time-weighted average perfusion index with acute kidney injury. The 30-day mortality was a secondary outcome.

RESULTS

Of 2534 cases included, 8.9% developed postoperative acute kidney injury. Areas and cumulative times under a perfusion index of 3% and 2% were associated with an increased risk of acute kidney injury; the strongest association was observed for area under a perfusion index of 1% (adjusted odds ratio [aOR] 1.32, 95% confidence interval [CI] 1.00-1.74, P=0.050, per 100%∗min increase). Additionally, time-weighted average perfusion index was associated with acute kidney injury (aOR 0.82, 95% CI 0.74-0.91, P<0.001) and 30-day mortality (aOR 0.68, 95% CI 0.49-0.95, P=0.024).

CONCLUSIONS

Larger areas and longer cumulative times under thresholds of perfusion index and lower time-weighted average perfusion index were associated with postoperative acute kidney injury in patients undergoing major noncardiac surgery and receiving continuous vasopressor infusions.

CLINICAL TRIAL REGISTRATION

NCT04789330.

Prediction of preload dependency using phenylephrine-induced peripheral perfusion index during general anaesthesia: a prospective observational study

BACKGROUND

Tracking preload dependency non-invasively to maintain adequate tissue perfusion in the perioperative period can be challenging.The effect of phenylephrine on stroke volume is dependent upon preload. Changes in stroke volume induced by phenylephrine administration can be used to predict preload dependency. The change in the peripheral perfusion index derived from photoplethysmography signals reportedly corresponds with changes in stroke volume in situations such as body position changes in the operating room. Thus, the peripheral perfusion index can be used as a non-invasive potential alternative to stroke volume to predict preload dependency. Herein, we aimed to determine whether changes in perfusion index induced by the administration of phenylephrine could be used to predict preload dependency.

METHODS

We conducted a prospective single-centre observational study. The haemodynamic parameters and perfusion index were recorded before and 1 and 2 min after administering 0.1 mg of phenylephrine during post-induction hypotension in patients scheduled to undergo surgery. Preload dependency was defined as a stroke volume variation of ≥ 12% before phenylephrine administration at a mean arterial pressure of < 65 mmHg. Patients were divided into four groups according to total peripheral resistance and preload dependency.

RESULTS

Forty-two patients were included in this study. The stroke volume in patients with preload dependency (n = 23) increased after phenylephrine administration. However, phenylephrine administration did not impact the stroke volume in patients without preload dependency (n = 19). The perfusion index decreased regardless of preload dependency. The changes in the perfusion index after phenylephrine administration exhibited low accuracy for predicting preload dependency. Based on subgroup analysis, patients with high total peripheral resistance tended to exhibit increased stroke volume following phenylephrine administration, which was particularly prominent in patients with high total peripheral resistance and preload dependency.

CONCLUSION

The findings of the current study revealed that changes in the perfusion index induced by administering 0.1 mg of phenylephrine could not predict preload dependency. This may be attributed to the different phenylephrine-induced stroke volume patterns observed in patients according to the degree of total peripheral resistance and preload dependency.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN000049994 on 9/01/2023).

"The peripheral perfusion index discriminates haemodynamic responses to induction of general anaesthesia"

Induction of general anaesthesia is often accompanied by hypotension. Standard haemodynamic monitoring during anaesthesia relies on intermittent blood pressure and heart rate. Continuous monitoring systemic blood pressure requires invasive or advanced modalities creating a barrier for obtaining important information of the circulation. The Peripheral Perfusion Index (PPI) is obtained non-invasively and continuously by standard photoplethysmography. We hypothesized that different patterns of changes in systemic haemodynamics during induction of general anaesthesia would be reflected in the PPI. Continuous values of PPI, stroke volume (SV), cardiac output (CO), and mean arterial pressure (MAP) were evaluated in 107 patients by either minimally invasive or non-invasive means in a mixed population of surgical patients. 2 min after induction of general anaesthesia relative changes of SV, CO, and MAP was compared to the relative changes of PPI. After induction total cohort mean(± st.dev.) MAP, SV, and CO decreased to 65(± 16)%, 74(± 18)%, and 63(± 16)% of baseline values. In the 38 patients where PPI decreased MAP was 57(± 14)%, SV was 63(± 18)%, and CO was 55(± 18)% of baseline values 2 min after induction. In the 69 patients where PPI increased the corresponding values were MAP 70(± 15)%, SV 80(± 16)%, and CO 68(± 17)% (all differences: p < 0,001). During induction of general anaesthesia changes in PPI discriminated between the degrees of reduction in blood pressure and algorithm derived cardiac stroke volume and -output. As such, the PPI has potential to be a simple and non-invasive indicator of the degree of post-induction haemodynamic changes.

Comparison of the perfusion index as an index of noxious stimulation in monitored anesthesia care of propofol/remifentanil and propofol/dexmedetomidine: a prospective, randomized, case-control, observational study

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.

The Perfusion Index of the Ear as a Predictor of Hypotension Following the Induction of Anesthesia in Patients with Hypertension: A Prospective Observational Study

Patients with hypertension develop hemodynamic instability more frequently during anesthesia-particularly post-induction. Therefore, different monitoring methods may be required in patients with hypertension. Perfusion index-the ratio of the pulsatile blood flow to the non-pulsatile static blood flow in a patient's peripheral tissues, such as the fingers or ears-can show the hemodynamic status of the patient in a non-invasive way. Among the sites used for measuring the perfusion index, it is assumed that the ear is more reliable than the finger for hemodynamic monitoring, because proximity to the brain ensures appropriate perfusion. We hypothesized that the low value of preoperative ear PI could be a predictor of post-induction hypotension in patients with hypertension. Thirty patients with hypertension were enrolled. The perfusion index and pleth variability index were measured using the ear, finger, and blood pressure, and heart rate was recorded to monitor hypotension. After insertion of the supraglottic airway, 20 patients developed post-induction hypotension. Those who developed hypotension showed a significantly lower preoperative perfusion index of the ear. The preoperative perfusion index of the ear could predict post-induction hypotension in patients with hypertension.

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.

Effect of perioperative magnesium sulfate and labetalol infusion on peripheral perfusion and postoperative pain in nasal surgery: a randomized controlled trial

BACKGROUND

Maintenance of adequate peripheral perfusion during controlled hypotension is necessary for patient safety and improved surgical outcomes during controlled hypotension in nasal surgery. The hypothesis of this study was to investigate the effect of perioperative magnesium sulfate and labetalol infusion on peripheral perfusion and postoperative pain in patients undergoing nasal surgery.

METHODS

A total of 50 patients were randomly assigned into two equal groups in this double-blind clinical study: the magnesium sulfate group; received 40 mg/kg loading dose of intravenous (IV) magnesium sulfate followed by 10-15 mg/kg/h continuous IV infusion and the labetalol group; received 0.25 mg/kg loading dose of IV labetalol followed by 0.5-1 mg/kg/h continuous IV infusion to achieve a mean arterial blood pressure (MABP) of = 55-65 mmHg. The primary outcome was to compare the effect of perioperative magnesium sulfate and labetalol infusion on peripheral perfusion during nasal surgery. The secondary outcomes were the assessment of serum lactate, postoperative pain, time to the first call for pethidine (rescue analgesic) and total pethidine consumption.

RESULTS

PPI was comparable between the groups at baseline, intubation, and 5 min. In contrast, magnesium sulfate group had a significantly higher PPI than the labetalol group. The magnesium sulfate group had a significantly higher MABP and heart rate compared to labetalol group. The time to reach the target MABP was significantly prolonged in magnesium sulfate than the labetalol group [21.6 ± 1.7 vs 6.9 ± 1.5] min. VAS scores were significantly lower for 2 hs postoperatively in the magnesium sulfate group than the labetalol group. The time to first call of pethidine was significantly prolonged in the magnesium sulfate group compared to the labetalol group [113.1 ± 5.2 vs 28.2 ± 1.5] min.

CONCLUSIONS

Magnesium sulfate maintains wider PPI and offers better postoperative pain relief compared to labetalol during induced hypotension in nasal surgery.

TRIAL REGISTRATION

Institutional review board approval (ref: 6601/20-12-2020).

CLINICALTRIAL

gov (ref: NCT04688203 , date of registration: 29 -12-2020).

To identify normovolemia in humans: The stroke volume response to passive leg raising vs. head-down tilt

Volume responsiveness can be evaluated by tilting maneuvers such as head-down tilt (HDT) and passive leg raising (PLR), but the two procedures use different references (HDT the supine position; PLR the semi-recumbent position). We tested whether the two procedures identify "normovolemia" by evaluating the stroke volume (SV) and cardiac output (CO) responses and whether the peripheral perfusion index (PPI) derived from pulse oximetry provides similar information. In randomized order, 10 healthy men were exposed to both HDT and PLR, and evaluations were made also when the subjects fasted. Central cardiovascular variables were derived by pulse contour analysis and changes in central blood volume assessed by thoracic electrical admittance (TEA). During HDT, SV remained stable (fasted 110 ± 16 vs. 109 ± 16 ml; control 113 ± 16 vs. 111 ± 16 ml, p > 0.05) with no change in CO, TEA, PPI, or SV variation (SVV). In contrast during PLR, SV increased (fasted 108 ± 17 vs. 117 ± 17 ml; control 108 ± 18 vs. 117 ± 18 ml, p < 0.05) followed by an increase in TEA (p < 0.05) and CO increased when subjects fasted (6.7 ± 1.5 vs. 7.1 ± 1.5, p = 0.007) with no change in PPI or SVV. In conclusion, SV has a maximal value for rest in supine men, while PLR restores SV as CBV is reduced in a semi-recumbent position and the procedure thereby makes healthy volunteers seem fluid responsive.

Prediction of Fluid Responsiveness by the Effect of the Lung Recruitment Maneuver on the Perfusion Index in Mechanically Ventilated Patients During Surgery

Introduction

Excessive or inadequate fluid administration during perioperative period affects outcomes. Adjustment of volume expansion (VE) by performing fluid responsiveness (FR) test plays an important role in optimizing fluid infusion. Since changes in stroke volume (SV) during lung recruitment maneuver (LRM) can predict FR, and peripheral perfusion index (PI) is related to SV; therefore, we hypothesized that the changes in PI during LRM (ΔPILRM) could predict FR during perioperative period.

Methods

Patients who were scheduled for elective non-laparoscopic surgery under general anesthesia with a mechanical ventilator and who required VE (250 mL of crystalloid solution infusion over 10 min) were included. Before VE, LRM was performed by a continuous positive airway pressure of 30 cm H2O for 30 sec; hemodynamic variables with their changes (PI, obtained by pulse oximetry; and ΔPILRM, calculated by using [(PI before LRM—PI after LRM)/PI before LRM]*100) were obtained before and after LRM. After SV (measured by esophageal doppler) and PI had returned to the baseline values, VE was infused, and the values of these variables were recorded again, before and after VE. Fluid responders (Fluid-Res) were defined by an increase in SV ≥10% after VE. Receiver operating characteristic curves of the baseline values and ΔPILRM were constructed and reported as areas under the curve (AUC) with 95% confidence intervals, to predict FR.

Results

Of 32 mechanically ventilated adult patients included, 13 (41%) were in the Fluid-Res group. Before VE and LRM, there were no differences in the mean arterial pressure (MAP), heart rate, SV, and PI between patients in the Fluid-Res and fluid non-responders (Fluid-NonRes) groups. After LRM, SV, MAP, and, PI decreased in both groups, ΔPILRM was greater in the Fluid-Res group than in Fluid-NonRes group (55.2 ± 17.8% vs. 35.3 ± 17.3%, p &lt; 0.001, respectively). After VE, only SV and cardiac index increased in the Fluid-Res group. ΔPILRM had the highest AUC [0.81 (0.66–0.97)] to predict FR with a cut-off value of 40% (sensitivity 92.3%, specificity 73.7%).

Conclusions

ΔPILRM can be applied to predict FR in mechanical ventilated patients during the perioperative period.

The effect of vasoconstriction on intestinal perfusion is determined by preload dependency: A prospective observational study

BACKGROUND

The effects of vasoconstriction on cardiac stroke volume (SV) and indices of peripheral and intestinal perfusion are insufficiently described.

METHODS

In a non-randomized clinical study, 30 patients undergoing elective rectal surgery were exposed to modulation of preload. The primary endpoint was intestinal perfusion (flux), measured by single-point laser Doppler flowmetry. Secondary endpoints were central cardiovascular variables obtained by the LiDCO rapid monitor, the peripheral perfusion index (PPI) derived from the pulse oximetry signal and muscle (StO₂ ) and cerebral oxygenation (ScO₂ ) determined by near-infrared spectroscopy.

RESULTS

For the whole cohort (n = 30), administration of Phenylephrine during HUT induced a median [IQR] increase in SV by 22% [14-41], p = .003 and in mean arterial pressure (MAP) by 54% [31-62], p < .001, with no change in PPI, StO₂ and ScO₂ or flux. In patients who were preload dependent during HUT (stroke volume variation; SSV >10%; n = 23), administration of phenylephrine increased SV by 29% [12-43], p = .01 and MAP by 54% [33-63], p < .001, followed by an increase in intestinal perfusion flux by 60% [15-289], p = .05, while PPI, StO₂ and ScO₂  remained unchanged. For non-preload dependent patients (SSV <10%; n = 7), no changes in hemodynamic indices were seen besides an increase in MAP by 54% [33-58], p = .002.

CONCLUSION

The reflection of vasoconstrictive modulation of preload in systemic cardiovascular variables and indices of perfusion was dependent on preload responsiveness. Administration of phenylephrine to increase preload did not appear to compromise organ perfusion.

Plethysmographic Peripheral Perfusion Index: Could It Be a New Vital Sign?

The plethysmographic peripheral perfusion index (PPI) is a very useful parameter with various emerging utilities in medical practice. The PPI represents the ratio between pulsatile and non-pulsatile portions in peripheral circulation and is mainly affected by two main determinants: cardiac output and balance between sympathetic and parasympathetic nervous systems. The PPI decreases in cases of sympathetic predominance and/or low cardiac output states; therefore, it is a useful predictor of patient outcomes in critical care units. The PPI could be a surrogate for cardiac output in tests for fluid responsiveness, as an objective measure of pain especially in un-cooperative patients, and as a predictor of successful weaning from mechanical ventilation. The PPI is simple to measure, easy to interpret, and has continuously displayed variables, making it a convenient parameter for detecting the adequacy of blood flow and sympathetic-parasympathetic balance.

Peripheral perfusion index and diagnostic accuracy of the post-ROSC electrocardiogram in patients with medical out-of-hospital cardiac arrest

AIM

A 12-lead electrocardiogram (ECG) after the return of spontaneous circulation (ROSC) is recommended to diagnose a ST-segment elevation myocardial infarction (STEMI). In the early post-ROSC phase, the ECG can show signs of ischemia not necessarily of coronary origin and post-ROSC hypoperfusion could affect ECG reliability. We sought for an association between peripheral perfusion index (PI) values after ROSC and the percentage of false-positive ECG for STEMI.

METHODS

We considered all the consecutive patients with sustained ROSC after OHCA, admitted to the Fondazione IRCCS Policlinico San Matteo (Pavia) between January 1st, 2015 and December 31st, 2020. ECGs were defined false-positive if meeting the STEMI criteria but without a critical obstructive coronary artery disease worthy of treatment. The mean value of PI over 30 min-monitoring (MPI30) were calculated.

RESULTS

Among 351 eligible patients post-ROSC ECG, PI monitoring and an invasive coronary angiography (ICA) were available in 84 cases. The rate of false positive was 16/54 (29.6%) and it differed significantly in the three MPI₃₀ tertiles [T1 (0.2-1): 28.6%; T2 (1.1-2.5): 24.1%; T3 (2.6-6.9): 3.7%, p = 0.04; p for trend = 0.02]. Cardiac arrest duration [OR 1.06 (95 %CI 1-1.1), p = 0.007] and MPI₃₀ [T3 vs T1: OR 0.09 (95 %CI 0.01-0.8), p = 0.03] were significantly associated with the probability of acquiring a false-positive ECG. This association was also confirmed when MPI₃₀ was adjusted for cardiac arrest duration [OR 0.2 (95 %CI 0.1-0.6), p=<0.001].

CONCLUSIONS

The rate of false-positive ECG for STEMI after ROSC is related with low perfusion. Our results could help to identify the adequate candidates for an immediate ICA.

Changes in the Plethysmographic Perfusion Index During an End-Expiratory Occlusion Detect a Positive Passive Leg Raising Test

OBJECTIVES

The end-expiratory occlusion test for assessing preload responsiveness consists in interrupting mechanical ventilation for 15 seconds at end-expiration and measuring the cardiac index changes. The perfusion index is the ratio between the pulsatile and the nonpulsatile portions of the plethysmography signal and is, in part, determined by stroke volume. We tested whether the end-expiratory occlusion-induced changes in perfusion index could detect a positive passive leg raising test, suggesting preload responsiveness.

DESIGN

Observational study.

SETTING

Medical ICU.

PATIENTS

Thirty-one ventilated patients without atrial fibrillation.

INTERVENTIONS

We measured perfusion index (Radical-7 device; Masimo Corp., Irvine, CA) and cardiac index (PiCCO2; Pulsion Medical Systems, Feldkirchen, Germany) before and during a passive leg raising test and a 15-second end-expiratory occlusion.

MEASUREMENTS AND MAIN RESULTS

In 19 patients with a positive passive leg raising test (increase in cardiac index ≥ 10%), compared to the baseline value and expressed as a relative change, passive leg raising increased cardiac index and perfusion index by 17% ± 7% and 49% ± 23%, respectively, In these patients, end-expiratory occlusion increased cardiac index and perfusion index by 6% ± 2% and 11% ± 8%, respectively. In the 12 patients with a negative passive leg raising test, perfusion index did not significantly change during passive leg raising and end-expiratory occlusion. Relative changes in perfusion index and cardiac index observed during all interventions were significantly correlated (r = 0.83). An end-expiratory occlusion-induced relative increase in perfusion index greater than or equal to 2.5% ([perfusion index during end-expiratory occlusion-perfusion index at baseline]/perfusion index at baseline × 100) detected a positive passive leg raising test with an area under the receiver operating characteristic curve of 0.95 ± 0.03. This threshold is larger than the least significant change observed for perfusion index (1.62% ± 0.80%).

CONCLUSIONS

Perfusion index could be used as a reliable surrogate of cardiac index for performing the end-expiratory occlusion test. Confirming previous results, the relative changes in perfusion index also reliably detected a positive passive leg raising test.

Association of the intraoperative peripheral perfusion index with postoperative morbidity and mortality in acute surgical patients: a retrospective observational multicentre cohort study

Background

We hypothesised that in acute high-risk surgical patients, a lower intraoperative peripheral perfusion index (PPI) would indicate a higher risk of postoperative complications and mortality.

Methods

This retrospective observational study included 1338 acute high-risk surgical patients from November 2017 until October 2018 at two University Hospitals in Denmark. Intraoperative PPI was the primary exposure variable and the primary outcome was severe postoperative complications defined as a Clavien–Dindo Class ≥III or death, within 30 days.

Results

intraoperative PPI was associated with severe postoperative complications or death: odds ratio (OR) 1.12 (95% confidence interval [CI] 1.05–1.19; P<0.001), with an association of intraoperative mean PPI ≤0.5 and PPI ≤1.5 with the primary outcome: OR 1.79 (95% CI 1.09–2.91; P=0.02) and OR 1.65 (95% CI 1.20–2.27; P=0.002), respectively. Each 15-min increase in intraoperative time spend with low PPI was associated with the primary outcome (per 15 min with PPI ≤0.5: OR 1.11 (95% CI 1.05–1.17; P<0.001) and with PPI ≤1.5: OR 1.06 (95% CI 1.02–1.09; P=0.002)). Thirty-day mortality in patients with PPI ≤0.5 was 19% vs 10% for PPI >0.5, P=0.003. If PPI was ≤1.5, 30-day mortality was 16% vs 8% in patients with a PPI >1.5 (P<0.001). In contrast, intraoperative mean MAP ≤65 mm Hg was not significantly associated with severe postoperative complications or death (OR 1.21 [95% CI 0.92–1.58; P=0.2]).

Conclusions

Low intraoperative PPI was associated with severe postoperative complications or death in acute high-risk surgical patients. To guide intraoperative haemodynamic management, the PPI should be further investigated.

Post-ROSC peripheral perfusion index discriminates 30-day survival after out-of-hospital cardiac arrest

BACKGROUND

Prognostication after an out-of-hospital cardiac arrest (OHCA) remains a challenge. The peripheral-derived perfusion index (PI) is a simple and non-invasive way to assess perfusion. We sought to assess whether the PI was able to discriminate the prognosis of patients resuscitated from an OHCA.

METHODS

All the reports generated by the manual monitor/defibrillator (Corpuls 3 by GS Elektromedizinische Geräte G. Stemple GmbH, Germany) used for all the OHCAs who achieved ROSC treated by our Emergency Medical Service from January 2015 to December 2018 were reviewed. The mean PI value of each minute after ROSC was automatically provided by the device and the mean value of 30 min of monitoring (MPI₃₀) was calculated. Pre-hospital data were collected according to the Utstein 2014 recommendations.

RESULTS

Among 1,909 resuscitation attempts, ROSC was achieved in 346 and it was possible to calculate an MPI₃₀ in 164. MPI₃₀ was higher in the patients who survived at 30 days [1.6 (95% CI 1.2-2.1) vs 1 (95% CI 0.8-1.3), p = 0.0017]. At the multivariable Cox regression model, after correction for shockable rhythm, witnessed status, bystander CPR, age, and blood pressure, MPI₃₀ was found to be an independent predictor of both 30-day mortality [RR 0.83 (95% CI 0.69-0.99), p = 0.036] and 30-day mortality or poor neurologic outcome [RR 0.85 (95% CI 0.72-0.99), p = 0.04]. Overall 30-day survival with good neurologic outcome was significantly different in the three tertiles [T1: 0.1-0.8; T2: 0.9-1.8 and T3: 1.82-7.8, log-rank p = 0.007].

CONCLUSION

The post-ROSC peripheral perfusion index was found to be an independent predictor of 30-day mortality or poor neurologic outcome. It could help prognostication in OHCA patients.

Effects of nitroglycerin versus labetalol on peripheral perfusion during deliberate hypotension for sinus endoscopic surgery: a randomized, controlled, double-blinded trial

BACKGROUND

Deliberate hypotension is used to provide a bloodless field during functional endoscopic sinus surgery; however, the impact of controlled hypotension during anesthesia on peripheral tissue perfusion has not been extensively evaluated. The aim of this study was to compare the impact of nitroglycerin- versus labetalol-induced hypotension on peripheral perfusion.

METHODS

The present randomized, double-blinded, controlled trial included adult patients undergoing endoscopic sinus surgery. Patients were allocated to one of two groups according to the drug received for induction of deliberate hypotension: nitroglycerin (n = 20) or labetalol (n = 20). Mean arterial pressure was maintained at 55-65 mmHg in both groups. Both study groups were compared according to pulse oximeter-derived peripheral perfusion index (primary outcome), serum lactate level, mean arterial pressure, heart rate, surgical field score, and intraoperative blood loss.

RESULTS

Forty patients were included in the final analysis. The nitroglycerin group exhibited a higher peripheral perfusion index at nearly all records (p < 0.0001) and lower postoperative serum lactate levels (1.3 ± 0.2 mmol/L vs. 1.7 ± 0.4 mmol/L; p = 0.001) than the labetalol group. The peripheral perfusion index was higher in the nitroglycerin group than at baseline at most intraoperative readings. The median surgical field score was modestly lower in the labetalol group than in the nitroglycerin group in the first 20 min (2 [interquartile range (IQR) 2-2.5] versus 1.5 [IQR 1-2]; p = 0.001). Both groups demonstrated comparable and acceptable surgical field scores in all subsequent readings.

CONCLUSION

Nitroglycerin-induced deliberate hypotension was accompanied by higher peripheral perfusion index and lower serum lactate levels than labetalol-induced deliberate hypotension during sinus endoscopic surgery.

TRIAL REGISTRATION

The study was registered at clinicaltrials registry system with trial number: NCT03809065. Registered at 19 January 2019. This study adheres to CONSORT guidelines.