Evaluation of oxygen administration in cesarean section under spinal anesthesia via lung ultrasound and the oxygen reserve index

BACKGROUND

Respiratory functions may be impaired in cesarean section (C/S) delivery performed under spinal anesthesia (SA) and oxygen supplementation may be required. Therefore, we conducted a randomized controlled study aimed to evaluate the effects of different oxygen administrations in pregnant women on the lungs during C/S under SA using ultrasound and oxygen reserve index (ORI).

METHODS

We conducted a randomized, controlled, single-center study from May 1, 2021, to March 31, 2022. A total of 90 patients scheduled for C/S under SA were randomly divided into 3 groups. Following the SA, patients in group 0 were treated with room air, in Group 3 were administered 3 L/min O₂ with a nasal cannula (NC), in Group 6 were administered 6 L/min O₂ with a simple face mask. In addition to routine monitoring, ORI values were measured. Lung aeration was evaluated through the modified lung ultrasound score (LUS) before the procedure (T0), at minute 0 (T1), 20 (T2), and hour 6 (T3) after the procedure, and ∆LUS values were recorded.

RESULTS

After SA, the ORI values of Group 3 were higher than Group 0 at all times (p < 0.05), while the intraoperative 1st minute and the 10th, 25th and 40th minutes after delivery (p = 0.001, p = 0.027, p = 0.001, p = 0.019) was higher than Group 6. When the LUS values of each group were compared with the T0 values a decrease was observed in Group 3 and Group 6 (p < 0.001, p = 0.016). While ∆LUS values were always higher in Group 3 than in Group 0, they were higher only in T1 and T2 in Group 6.

CONCLUSION

We determined that it would be appropriate to prefer 3 L/min supplemental oxygen therapy with NC in C/S to be performed under SA.

Comparison of remimazolam-based and propofol-based total intravenous anesthesia on hemodynamics during anesthesia induction in patients undergoing transcatheter aortic valve replacement: a randomized controlled trial

PURPOSE

This study aimed to compare the hemodynamic effects of remimazolam- and propofol-based total intravenous anesthesia in patients who underwent transcatheter aortic valve replacement.

METHODS

This was a single-center, single-blind, randomized controlled trial set at Nara Medical University, Kashihara, Japan. We included 36 patients aged ≥ 20 years scheduled to undergo elective transfemoral transcatheter aortic valve replacement (TAVR) under general anesthesia. The participants were randomly assigned to the remimazolam and propofol groups (n = 18 each). Remimazolam- or propofol-based total intravenous anesthesia was initiated at 12 mg/kg/min or 2.5 mcg/mL via target-controlled infusion, respectively, along with remifentanil. After confirming the loss of consciousness, the administration rate was adjusted using electroencephalographic monitoring. The primary outcome was the rate of arterial hypotension, defined as a mean arterial pressure < 60 mmHg, from anesthesia induction until the beginning of the surgical incision. The total doses of ephedrine and phenylephrine were also assessed.

RESULTS

During anesthesia induction, the arterial hypotension rates were 11.9% and 21.6% in the remimazolam and propofol groups, respectively (P = 0.01). The total dose of ephedrine was higher in the propofol group (14.4 mg) than in the remimazolam group (1.6 mg) (P < 0.001); however, the total dose of phenylephrine was not significantly different between the two groups (propofol 0.31 mg vs. remimazolam: 0.17 mg, P = 0.10).

CONCLUSION

Remimazolam-based total intravenous anesthesia resulted in a lower hypotension rate than propofol-based total intravenous anesthesia during induction in patients undergoing TAVR. Remimazolam-based total intravenous anesthesia can be used safely during anesthetic induction in patients with severe aortic stenosis.

Diagnostic utility of perfusion index in identifying radial artery embolism during hyperthermic intraperitoneal chemotherapy procedure: a case report

Invasive arterial cannulation is a widely used method in intensive care units and operating rooms. However it has potential complications such as thrombosis, peripheral embolism, hematoma formation, and infection. The Masimo Root Radical-7 Pulse CO-Oximeter® (Masimo Corporation, Irvine, CA, USA) is a non-invasive hemodynamic monitoring device that measures perfusion index and pleth variability index, provides guidance to anaesthesiologists in the cases where hemodynamic fluctuations are expected. In this particular case, the perfusion index played a crucial role in the immediate diagnosis of radial artery embolism in a patient undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy procedure.

Comparing Perfusion Index and Visual Analogue Scores for Postoperative Pain Assessment Following Upper Limb Surgeries Under Supraclavicular Brachial Plexus Block: An Observational Study

BACKGROUND

Effective pain assessment is crucial to tailor the analgesic regimen post-operatively. Perfusion index (PI) has been reported to be a useful objective assessment tool for monitoring pain. This study aimed to explore the utility of PI in assessing postoperative pain in upper limb surgeries under supraclavicular block and its correlation with visual analogue scale (VAS) scores.

METHODS

This prospective, observational study included 140 patients scheduled for elective upper limb surgeries. PI, VAS scores, heart rate (HR), mean arterial pressure (MAP) and physiological parameters were recorded at baseline and postoperatively. Inj. tramadol was administered when the VAS score exceeded ≥ 4 and the VAS score, PI, HR and MAP were recorded at 5, 10, 15 and 20 minutes after administration. Comparison of normally and non-normally distributed data was done using t-statistics and Mann-Whitney U-test respectively. Pearson correlation was used to establish a correlation between variables and the receiver operating characteristic (ROC) curve was used to calculate the cut-off value of PI to determine the onset of pain.

RESULTS

There was a significant and moderate correlation between pre-analgesic and post-analgesic PI and VAS score (r = -0.425 and -0.448 respectively, p<0.001), while PI and MAP or PI and HR showed only a weak correlation. A cut-off value of 14.7 for PI showed 76.3% sensitivity and 100% specificity in predicting rescue analgesia requirements.

CONCLUSION

The study supports the use of PI as an objective measure for postoperative pain assessment, with a notable correlation with VAS scores. The identified cut-off value for PI adds to its clinical utility in predicting the need for rescue analgesia.

Changes in the corrected carotid flow time can predict spinal anesthesia-induced hypotension in patients undergoing cesarean delivery: an observational study

PURPOSE

Spinal anesthesia is a standard technique for cesarean delivery; however, it possesses a risk of hypotension. We hypothesised that the changes in the corrected flow time induced by the Trendelenburg position could predict the incidence of hypotension after spinal anesthesia for cesarean delivery.

METHODS

Patients undergoing elective cesarean delivery under spinal anesthesia were enrolled. Before anesthesia induction, corrected flow time was measured in the supine and Trendelenburg positions (FTc-1 and FTc-2, respectively). Additionally, a percent change in corrected flow time induced by the Trendelenburg position was defined as ΔFTc. The primary endpoint was to investigate the ability of ΔFTc to predict the incidence of spinal anesthesia-induced hypotension until delivery. The receiver operating characteristics curves to assess the ability of FTc-1, FTc-2, and ΔFTc to predict the incidence of hypotension were generated.

RESULTS

Finally, 40 patients were included, and of those, 26 (65%) developed spinal anesthesia-induced hypotension. The areas under the curve for FTc-1, FTc-2, and ΔFTc were 0.591 (95% CI: 0.424 to 0.743) (P = 0.380), 0.742 (95% CI: 0.579 to 0.867) (P = 0.004), and 0.882 (95% CI: 0.740 to 0.962) (P < 0.001) respectively, indicating ΔFTc as the best predictor among these three parameters. The best threshold for ΔFTc was 6.4% (sensitivity: 80.8% (95% CI: 53.8 to 96.2), specificity: 85.7% (95% CI: 42.9 to 100.0)).

CONCLUSIONS

This study demonstrated that changes in the corrected carotid flow time induced by the Trendelenburg position could serve as a good predictor of spinal anesthesia-induced hypotension for cesarean delivery.

The diagnostic accuracy of preoperative perfusion index as a predictor of postspinal anesthesia hypotension in parturients undergoing cesarean delivery: A prospective non-blinded observational study

Background and Objectives

Spinal anesthesia is the technique of choice for elective cesarean section with a prominent side effect of postspinal anesthesia hypotension (PSH). This needs an early prediction to avoid feto-maternal complication. This study aimed to assess the diagnostic accuracy of perfusion index (PI) and inferior vena cava collapsibility index (IVCCI) in the prediction of PSH.

Material and Methods

Thirty parturients of American Society of Anesthesiologists Physical Status (ASA-PS) 1 and two undergoing cesarean delivery participated in the study. IVCCI, PI, baseline systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), and heart rate (HR) were noted in the preoperative period. The fall of MBP by 20% from baseline or below 65 mm Hg was considered PSH. After spinal anesthesia, SBP, DBP, MBP, and HR were noted again for diagnosing PSH.

Results

It did not show any statistical difference when comparing the PI between the PSH and non-PSH groups in both the PSH definition groups. IVCCI was significantly higher when PSH was considered MBP <65 mm Hg (P = 0.01). However, IVCCI was found to be statistically insignificant if PSH was considered a 20% reduction in baseline MBP. The correlation matrix between IVCCI and PI showed Pearson's r-value of 0.525, indicating a substantial relationship between the two (P = 0.003). Multivariate logistic regression analysis had shown that neither IVCCI nor PI was a good predictor of PSH in parturients for both definition groups for PSH.

Conclusion

Although there is a modest correlation between PI and IVCCI, both cannot be used to predict postspinal hypotension in parturients undergoing elective lower-segment cesarean section (LSCS).

Evaluation of perfusion index as a predictor of successful caudal block in pediatric patients: A prospective randomized study

Background and Aims

Caudal block is among the most widely administered regional anesthesia in pediatric patients. The clinical signs and objective assessments are not fast and reliable enough to provide a good feedback. Perfusion index (PI) is considered as a sensitive marker to assess the efficacy of caudal block. We aim to assess PI as an indicator for success of caudal block in pediatric patients.

Material and Methods

Sixty pediatric patients scheduled for elective surgery of lower abdomen and below were included. Patients were randomly allocated into two groups (n = 30): Group 1 received caudal block after general anesthesia and Group 2 only received general anesthesia. PI, heart rate, mean arterial pressure, and anal sphincter tone (AST) were recorded at 5, 10, 15, and 20 min following induction of anesthesia.

Results

A persistent increase in the PI value was observed in Group 1 starting from 5 min till 20 min, as compared to Group 2, at all the time intervals. When mean PI was statistically compared between both the groups, it was found to be highly significant (P = 0.001). Group 1 patients have progressive laxity of AST which was found to be significantly different from Group 2 (P < 0.001).

Conclusion

We have found that both PI and AST are good indicators for assessing success of caudal block onset in pediatric patients but AST took slightly longer time (~20 mins). Therefore, we conclude that PI is simple, economical, and noninvasive monitor that predicts the caudal onset much earlier than AST.

Perfusion index to predict post spinal hypotension in lower segment caesarean section

Background and Aims

It is important to predict and prevent post-spinal hypotension in lower segment cesarean section (LSCS). Peripheral vascular tone can be monitored as a perfusion index (PI) from a pulse oximeter. We aimed to study baseline PI as a predictor of post-spinal hypotension in LSCS.

Material and Methods

Prospective observational study conducted in a tertiary care teaching public hospital on patients posted for elective LSCS under spinal anesthesia. Baseline PI and hypotension were compared. A receiver operating characteristic (ROC) curve was plotted and data were analyzed using SPSS version 20.

Results

Among 90 females, 43 (47.8%) had a PI ≤3.5 and 47 (52.2%) had a PI >3.5. In the PI >3.5 group, 46 (97.9%) females had hypotension and required a high volume of IV fluids, and 29 (61.7%) required vasopressors, and the association with PI was statistically significant with Pearson's Chi-square values of 32.26 and 32.36, respectively (P = 0.001). In the ROC, the area under the curve (AUC) was 0.917, proving baseline PI >2.9 as an excellent classifier (P < 0.0001,95% confidence interval [CI] 0.840-0.965) and can predict hypotension with a sensitivity of 83.08% and specificity of 96.00%.

Conclusion

Baseline PI >3.5 was associated with significant post-spinal hypotension and vasopressor administration in LSCS. We established baseline PI >2.9 can predict post-spinal hypotension with high sensitivity and specificity. PI is simple, quick, and non-invasive and can be used as a predictor for post-spinal hypotension in parturients undergoing LSCS so that prophylactic measures can be considered in at-risk patients for better maternal and fetal outcomes.

"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.

Predictive Efficacy of the Perfusion Index for Hypotension following Spinal Anesthesia in Parturient Undergoing Elective Cesarean Section: A Systematic Review and Meta-Analysis

This meta-analysis assessed the predictive efficacy of perfusion index for hypotension following spinal anesthesia (SA) in parturients undergoing elective cesarean section (CS). Electronic databases, including Google Scholar, EMBASE, Cochrane Library, and MEDLINE, were searched from inception to June 2023. The primary outcome was the diagnostic accuracy of the perfusion index in predicting the probability of perioperative hypotension following SA. The review included 12 studies involving 2009 patients, published between 2017 and 2023. The pooled sensitivity and specificity were 0.81 (95% confidence interval (CI) = 0.72-0.87) and 0.75 (95% CI = 0.67-0.82), respectively. Additionally, the pooled area under the curve (AUC) was calculated as 0.84 (95% CI = 0.81-0.87), suggesting a moderate to good accuracy of the diagnostic test. Using Fagan's nomogram plot, the positive likelihood ratio (LR) and negative LR were found to be 3 and 0.26, respectively. The results demonstrated that the perfusion index exhibited an acceptable level of accuracy in predicting perioperative hypotension after spinal anesthesia in parturients undergoing elective CS. These findings highlight the potential value of incorporating a perfusion index as a useful tool for clinicians to integrate into routine clinical practice, which necessitates further large-scale studies for verification.

Predictive ability of pulse oximetry-derived indices for hypotension after spinal anaesthesia for caesarean section: protocol for a systematic review and meta-analysis

INTRODUCTION

In general, caesarean sections are performed under spinal anaesthesia. Hypotension after spinal anaesthesia adversely affects both the mother and fetus. Although several studies have used pulse oximetry-derived indices, such as pulse perfusion index (PI) and Pleth variability index (PVI), to predict hypotension after spinal anaesthesia, the predictive ability of the PI and PVI remain controversial.

METHODS AND ANALYSIS

We prepared this protocol following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines. We will conduct searches of MEDLINE, Embase, Web of Science, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Clinicaltrial.gov, European Union Clinical Trials Register (EU-CTR), WHO International Clinical Trials Registry Platform (ICTRP) and University Hospital Medical Information Network Clinical Trials Registry (UMIN) from inception until 8 October 2022. We will include retrospective and prospective observational studies and randomised controlled trials that evaluated the predictive ability of PI and PVI for hypotension after spinal anaesthesia for caesarean section, published in any language. We will exclude case reports, case series and animal studies. Two authors will independently scan and select eligible studies and perform data extraction and assessment of risk of bias. We will estimate predictive ability of PI and PVI as indices of hypotension after spinal anaesthesia for caesarean section using the Reitsma-type bivariate random-effects synthesis model and the hierarchical summary receiver operating characteristic curve. We will assess the quality of evidence using the Grading of Recommendation Assessment, Development and Evaluation approach.

ETHICS AND DISSEMINATION

Ethics approval is not required as the systematic review will use existing published data. The results will be submitted for publication in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022362596.

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 utility of the perfusion index as an indicator of anesthetic depth for repeated propofol sedation in children: An observational study

BACKGROUND

Children receiving proton therapy require repeated sedation. In this study, we aimed to investigate the utility of the perfusion index (PI) for evaluating consciousness level during repeated propofol sedation.

METHODS

In this prospective observational study, children aged from birth to 19 years old scheduled for proton therapy under repeated propofol sedation were enrolled. The primary outcome was the equivalence of PI values 5 min after anesthesia induction on consecutive sedation. Total consumption of propofol during sedation, time to reach the University of Michigan sedation scale (UMSS) score 1 after end of proton therapy, and duration of post-anesthesia care unit (PACU) stay were recorded.

RESULTS

The PI values measured 5 min after induction of anesthesia were not equivalent to each other in consecutive sedation except for the second versus third (1st vs. 2nd: 97.5% CI: -1.34, 0.91; p = 0.206, 0.034; 2nd vs. 3rd: 97.5% CI: -0.87, 0.94; p = 0.023, 0.036 3rd vs. 4th: 97.5% CI: -2.08, -0.26; p < 0.99, <0.001; 4th vs. 5th: 97.5% CI: 0.21, 2.28; p < 0.001, >0.99; respectively). In consecutive sedation, there was not a significantly different difference in the time to reach UMSS score 1 (p > 0.99, all) for total consumption of propofol, time to reach UMSS score 1 after the end of proton therapy, and duration of PACU stay.

CONCLUSIONS

During repeated propofol sedation in children, PI was insufficient to be used as an indicator of consciousness level assessment. However, we suggest that the information related to repeated sedation provided by this study may be helpful in clinical practice.

Perfusion Index and Its Correlation With Intraoperative Hypotension in Lower-Segment Cesarean Section Under Spinal Anesthesia: A Prospective Observational Study in a Tertiary Care Hospital in Eastern India

Background

Hypotension is commonly encountered in patients undergoing lower-segment cesarean section (LSCS) under the subarachnoid block (SAB) owing to decreased vascular resistance caused by the sympathetic blockade and decreased cardiac output because of blood pooling in blocked areas of the body. Perfusion index (PI) is a good indicator of systemic vascular resistance and can foretell hypotension. This study aimed to associate baseline PI with intraoperative hypotension after SAB in LSCS.

Methodology

This was a prospective observational study with a sample size of 50. The baseline PI was recorded every 10 seconds for one minute in a supine position on the right index finger at room temperature of 26°C to 28°C. The blood pressure (BP) and heart rate (HR) were recorded at an interval of one minute for three minutes. The mean of PI, BP, and HR were taken as the preoperative value. Spinal anesthesia was administered as per institutional protocol. Hypotension, defined as mean arterial pressure (MAP) <20% of baseline or MAP <60 mmHg was treated with vasopressors. Regression analysis with the Spearman correlation coefficient was done to correlate PI and hypotension.

Results

The incidence of hypotension in parturients with PI <2.85 was 28.6% (5/20) and in parturients with PI >2.85 was 82.8% (p < 0.001). The requirement of sympathomimetics was higher in parturients with PI >2.85.The area under the receiver operating characteristic curve was 0.8883. A cut-off PI value of 2.85 can identify parturients at risk for central neuraxial block-induced hypotension with a sensitivity of 80% and a specificity of 75% (p < 0.001).

Conclusions

The PI is a useful tool for predicting hypotension in healthy parturients undergoing elective cesarean section under SAB.

Provisional Decision-Making for Perioperative Blood Pressure Management: A Narrative Review

Blood pressure (BP) is a basic determinant for organ blood flow supply. Insufficient blood supply will cause tissue hypoxia, provoke cellular oxidative stress, and to some extent lead to organ injury. Perioperative BP is labile and dynamic, and intraoperative hypotension is common. It is unclear whether there is a causal relationship between intraoperative hypotension and organ injury. However, hypotension surely compromises perfusion and causes harm to some extent. Because the harm threshold remains unknown, various guidelines for intraoperative BP management have been proposed. With the pending definitions from robust randomized trials, it is reasonable to consider observational analyses suggesting that mean arterial pressures below 65 mmHg sustained for more than 15 minutes are associated with myocardial and renal injury. Advances in machine learning and artificial intelligence may facilitate the management of hemodynamics globally, including fluid administration, rather than BP alone. The previous mounting studies concentrated on associations between BP targets and adverse complications, whereas few studies were concerned about how to treat and multiple factors for decision-making. Hence, in this narrative review, we discussed the way of BP measurement and current knowledge about baseline BP extracting for surgical patients, highlighted the decision-making process for BP management with a view to providing pragmatic guidance for BP treatment in the clinical settings, and evaluated the merits of an automated blood control system in predicting hypotension.

Peripheral Perfusion Index: A Predictor of Post-Spinal Hypotension in Caesarean Section

Background

Early prediction of hypotension helps to decide appropriate prophylactic measures and, hence, safe anaesthesia for mothers and improved neonatal outcomes. Perfusion index (PI) measured from a standard pulse oximeter has shown positive results in the prediction of hypotension. This study aims to determine if PI can equally predict hypotension in parturients after administration of spinal anaesthesia at different time points.

Methods

Parturients posted for elective caesarean section belonging to the American Society of Anesthesiology II (ASA II) were divided into two groups based on baseline PI as group A <3.5 and group B ≥3.5. Fifty-six parturients were enrolled in the study. PI and blood pressure were monitored at baseline, every two minutes for 12 minutes and every five minutes until the end of the surgery, after administration of spinal anaesthesia with hyperbaric bupivacaine 10 mg. Incidence of hypotension was compared between groups at all time points of observation. Spearman’s rank correlation coefficient was determined to check the correlation between baseline PI and the number of episodes of hypotension. Receiver operating characteristic (ROC) curve was plotted to determine the ideal cut-off at different time points.

Results

Baseline PI significantly correlated with the number of episodes of hypotension (r-0.525). The overall incidence of hypotension was significantly higher in parturients with baseline PI ≥3.5 (79.16%) as compared to those with PI <3.5 (33.33%). The incidence of hypotension at sixth, 10th and 37th minutes post-spinal anaesthesia administration was significantly higher in the group with PI ≥3.5. The sensitivity and specificity for the 3.5 cut-off of PI were 85.7% and 60%, respectively, at the 6th and 10th minute after spinal administration. A higher cut-off of 3.9 increases the specificity to 69% without much change in the sensitivity.

Conclusion 

Parturients with PI >3.9 at baseline have a higher risk of hypotension in the initial 10-12 minutes following spinal anaesthesia during caesarean delivery.

A Cross-Sectional Study on the Agreement of Perfusion Indexes Measured on Different Fingers by a Portable Pulse Oximeter in Healthy Adults

Background

Pulse oximeters measure oxygen saturation, heart rate, and perfusion index (PI) by analyzing photoplethysmographic signals. PI is an indirect measure of peripheral perfusion expressed as a percentage of pulsatile signals to non-pulsatile signals. PI measured from different sites may show variation. PI may vary when measured on different fingers. In this study, we aimed to observe the variation of PI among different fingers of both hands.

Methodology

This cross-sectional, observational study was conducted using a convenience sample recruited from a tertiary care hospital in eastern India. PI was measured in apparently healthy adults in a sitting posture after a five-minute rest. The pulse oximeter probe was attached to each finger and readings were taken after one minute. The analysis of variance and intraclass correlation coefficient (ICC) were calculated to compare and find agreement among PI.

Results

Data from a total of 391 (229 [58.57%] male and 162 [41.43%] female) adult research participants with a mean age of 34.88 ± 10.65 years were analyzed. The PI was the highest on the middle finger in both hands. There was a significant difference among the PI measured on different fingers, F (9, 3900) = 15.49, p <0.0001. The ICC was 0.474, 0.368, and 0.635 for overall, right-hand, and left-hand fingers, respectively, which indicate poor (ICC < 0.5) to moderate (ICC = 0.5-0.75) levels of reliability.

Conclusions

The PI measured using consumer-grade pulse oximeters on different fingers may provide different readings. The highest PI reading is found on the middle finger. Clinicians and primary care physicians should consider the differences in measured PI among different fingers and should use the readings with caution for any diagnostic purposes.

An observational study on perfusion index to predict and correlate incidences of hypotension following spinal anaesthesia using pulse oximeter

Perfusion Index (PI) is the ratio of the pulsatile blood flow to the non-pulsatile or static blood in the peripheral tissues. It is a new parameter tried for predicting hypotension during spinal anaesthesia.  Our aim was to observe Perfusion Index as an early predictor of hypotension under spinal anaesthesia in patients undergoing elective surgeries. In this observational study, 30 patients between the age group of 18-50years and belonged to ASA I and II category were taken. Spinal anaesthesia was performed with 3-4 ml of injection Bupivacaine 0.5% (hyperbaric) at L3–L4 interspace. Following spinal anaesthesia heart rate, blood pressure, and PI were recorded for 30 minutes. Hypotension was defined as fall in the MAP of 20% from the baseline and was treated with fluids, parasympatholytic ± vasopressors. Analysis was performed using software IBM SPSS statistics for windows, Data was presented as mean ± standard deviation. A P value < 0.05 was considered statistically significant. Regression analysis with Spearman’s rank correlation coefficient was done to assess the correlation between baseline PI and hypotension. Receiver operating characteristic (ROC) curve was plotted for PI and occurrence of hypotension. 

A study to evaluate the change in perfusion index as an indicator of successful ultrasound-guided supraclavicular block

Background and Aims:

Perfusion index (PI) is a new simple, objective and non-invasive method for evaluation of the success of central neuraxial and peripheral nerve blocks. So, we conducted a study with an aim to evaluate PI as an indicator for success of ultrasound-guided supraclavicular block (SCB).

Methods:

65 patients of either sex, age 18–60 years, American Society of Anesthesiologists physical status I and II posted for upper limb surgery under ultrasound (US)-guided SCB were included. PI was recorded at baseline every 2 minutes till 10 minutes and then every 5 minutes till 30 minutes after block. PI ratio was calculated as the ratio between PI at 10 minutes and baseline PI. Sensory and motor blocks were assessed at 5-minutes intervals up to 30 minutes. Descriptive analysis was applied by mean and standard deviation for quantitative, frequency and proportion for categorical variables.

Results:

Mean PI increased continuously from baseline and reached the maximum at 10 minutes and then slightly decreased up to 30 minutes, but values at subsequent time intervals were quite high as compared to baseline. In case of successful blocks, median PI started increasing 2 minutes after the block and then increased in a linear fashion till 10 minutes, whereas in case of failed blocks, it only increased minimally.

Conclusion:

PI is an objective and faster indicator for evaluating success of US-guided SCB. A cut-off value of 3.25 for PI and 3.03 for PI ratio showed a fairly good ability with high sensitivity and specificity for predicting the success of SCB.

Optimum dose of spinal ropivacaine with or without single intravenous bolus of S-ketamine during elective cesarean delivery: a randomized, double-blind, sequential dose-finding study

Background

Maternal hypotension after spinal anaesthesia occurs at a high rate during caesarean delivery and can lead to adverse maternal or foetal outcomes. The aim of this study was to determine the optimal dose of spinal ropivacaine for caesarean section with or without intravenous single bolus of S-ketamine and to observe the rates of hypotension associated with both methods.

Methods

Eighty women undergoing elective caesarean delivery were randomly allocated into either a ropivacaine only or ropivacaine with intravenous S-ketamine group. If the upper sensory level of the patient reached T6 and the visual analogue scale (VAS) scores remained below 3 points before delivery, the next patient had a 1/9th chance of receiving a lower dose or an 8/9th chance of receiving the same dose as the previous patient. If the patient had VAS scores of more than 2 points or needed an extra epidural rescue bolus before delivery, a higher dose was used for the next patient. The primary outcome was the successful use of spinal ropivacaine to maintain patient VAS score of < 3 points before delivery and the incidence of post-spinal hypotension in both groups. Secondary outcomes included the rates of hypotension-related symptoms and interventions, upper sensory level of anaesthesia, level of sedation, neonatal outcomes, Edinburgh Postnatal Depression Scale scores at admission and discharge, and post-operative analgesic effect. The 90% effective dose (ED90) and 95% confidence interval (95% CI) were estimated by isotonic regression.

Results

The estimated ED90 of ropivacaine was 11.8 mg (95% CI: 11.7–12.7) with and 14.7 mg (95% CI: 14.6–16.0) without intravenous S-ketamine, using biased coin up-down sequential dose-finding method. The rates of hypotension and associated symptoms were significantly lower in S-ketamine group than in the ropivacaine only group.

Conclusions

A spinal dose of ropivacaine 12 mg with a single intravenous 0.15 mg/kg bolus dose of S-ketamine may significantly reduce the risk of hypotension and induce sedation before delivery. This method may be used with appropriate caution for women undergoing elective caesarean delivery and at a high risk of hypotension or experiencing extreme nervousness.

Trial registration

http://www.chictr.org.cn (ChiCTR2000040375; 28/11/2020).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04229-y.

Perfusion index: Physical principles, physiological meanings and clinical implications in anaesthesia and critical care

Photoplethysmography (PPG) has been extensively used for pulse oximetry monitoring in anaesthesia, perioperative and intensive care. However, some components of PPG signal have been employed for other purposes, such as non-invasive haemodynamic monitoring. Perfusion index (PI) is derived from PPG signal and represents the ratio of pulsatile on non-pulsatile light absorbance or reflectance of the PPG signal. PI determinants are complex and interlinked, involving and reflecting the interaction between peripheral and central haemodynamic characteristics, such as vascular tone and stroke volume. Recently, several studies have shed light on the interesting performances of this variable, especially assessing regional or neuraxial block success, and haemodynamic monitoring in anaesthesia, perioperative and intensive care. Nevertheless, no review has yet been published concerning the interest of PI in these fields. In this narrative review will be exposed first the physiological and pathophysiological determinants of PI, and then the mean to measure this value as well as its potential limitations. In the second part, the existing data concerning usefulness of PI in different clinical settings such as operating theatres, intensive care units and emergency departments will be presented and discussed. Finally, the perspectives concerning the use of PI and mentioned aspects that should be explored regarding this tool will be underlined.

Performance of the Hypotension Prediction Index With Noninvasive Arterial Pressure Waveforms in Awake Cesarean Delivery Patients Under Spinal Anesthesia

BACKGROUND

Arterial hypotension is common after spinal anesthesia (SA) for cesarean delivery (CD), and to date, there is no definitive method to predict it. The hypotension prediction index (HPI) is an algorithm that uses the arterial waveform to predict early phases of intraoperative hypotension. The aims of this study were to assess the diagnostic ability of HPI working with arterial waveforms detected by ClearSight system in predicting impending hypotension in awake patients, and the agreement of pressure values recorded by ClearSight with conventional noninvasive blood pressure (NIBP) monitoring in patients undergoing CD under SA.

METHODS

In this retrospective analysis of pregnant patients scheduled for elective CD under SA, continuous hemodynamic data measured with the ClearSight monitor until delivery were downloaded from an Edwards Lifesciences HemoSphere platform and analyzed. Receiver operating characteristic (ROC) curves were constructed to evaluate the performance of HPI algorithm working on the ClearSight pressure waveform in predicting hypotensive events, defined as mean arterial pressure (MAP) <65 mm Hg for >1 minute. The sensitivity, specificity, positive predictive value, and negative predictive value were computed at the optimal cutpoint, selected as the value that minimizes the difference between sensitivity and specificity. ClearSight MAP values were compared to NIBP MAP values by linear regression and Bland-Altman analysis corrected for repeated measurements.

RESULTS

Fifty patients undergoing CD were included in the analysis. Hypotension occurred in 23 patients (48%). Among patients experiencing hypotension, the HPI disclosed 71 alerts. The HPI predicted hypotensive events with a sensitivity of 83% (95% confidence interval [CI], 69-97) and specificity of 83% (95% CI, 70-95) at 3 minutes before the event (area under the curve [AUC] 0.913 [95% CI, 0.837-0.99]); with a sensitivity of 97% (95% CI, 92-100) and specificity of 97% (95% CI, 92-100) at 2 minutes before the event (AUC 0.995 [95% CI, 0.979-1.0]); and with a sensitivity of 100% (95% CI, 100-100) and specificity 100% (95% CI, 100-100) 1 minute before the event (AUC 1.0 [95% CI, 1.0-1.0]). A total of 2280 paired NIBP MAP and ClearSight MAP values were assessed. The mean of the differences between the ClearSight and NIBP assessed using Bland-Altman analysis (±standard deviation [SD]; 95% limits of agreement with respective 95% CI) was -0.97 mm Hg (±4.8; -10.5 [-10.8 to -10.1] to 8.5 [8.1-8.8]).

CONCLUSIONS

HPI provides an accurate real time and continuous prediction of impending intraoperative hypotension before its occurrence in awake patients under SA. We found acceptable agreement between ClearSight MAP and NIBP MAP.

Effects of magnesium sulphate on the onset time of rocuronium at different doses: a randomized clinical trial

Background and aims

Rocuronium may provide excellent onset time, but high doses are required for effective action. Several strategies have managed to shorten rocuronium onset time, including the use of Magnesium Sulphate (MgSO₄).

Methods

One hundred and eighty patients were randomized into six groups according to rocuronium dose received (0.3, 0.6 or 1.2 mg.kg^-1) and the administration of saline or MgSO⁴ (60 mg.kg^-1). Correlations between tissue perfusion and rocuronium onset time was determined by variations in perfusion index.

Results

Median (quartiles) rocuronium onset times were 85.5 (74.0–92.0); 76.0 (52.0–87.0) and 50.0 (41.0–59.5) seconds for 0.3, 0.6 mg.kg^-1 and 1.2 mg.kg^-1 doses, respectively. MgSO₄ decreased rocuronium onset at doses of 0.3 mg.kg^-1 (60.0 [48.0–74.3] seconds) and 0.6 mg.kg^-1 (44.0 [39.0–49.0] seconds) but not at 1.2 mg.kg^-1 (38.0 [33.5–56.3] seconds) (p < 0.001). Perfusion index variations in groups that received MgSO₄ were greater than in controls. A negative correlation between shorten onset and increased perfusion index was observed in rocuronium doses of 0.3 mg.kg^-1 (r = -0.50; p < 0.001) and 0.6 mg.kg^-1 (r = -0.424; p < 0.001), but not for 1.2 mg.kg^-1 dose (r = -0.25; p = 0.07).

Conclusion

MgSO₄ reduces rocuronium onset time at doses of 0.3 mg.kg^-1 and 0.6 mg.kg^-1 being that the latter has a similar effect when compared to the dose of 1.2 mg.kg^-1, with or without the use of MgSO₄.

Trial registry at

http://www.ensaiosclinicos.gov.br/

Registry Number

RBR-96CY3K

Preoperative perfusion index as a predictor of post-anaesthetic shivering in caesarean section with spinal anaesthesia

BACKGROUND

Post-anaesthetic shivering is frequently preceded by a decrease in peripheral blood flow. Perfusion index is a fast non-invasive method to assess peripheral blood flow, thus might be correlated with post-anaesthetic shivering.

AIM

To analyse the relationship between preoperative perfusion index and post-anaesthetic shivering in patients undergoing caesarean section with spinal anaesthesia.

METHODS

In this prospective observational study, preoperative perfusion index measurements were performed on 40 participants who were undergoing elective caesarean section under spinal anaesthesia. Spinal anaesthesia was performed using Lidodex (Lignocaine + Dextrose 5%) at vertebrae L4-L5 or L3-L4 interspace. Shivering was observed until 120 minutes according to the Crossley and Mahajan scale. Statistical analysis was performed to examine the correlation and cut-off of preoperative perfusion index as a predictor for post-anaesthetic shivering.

RESULT

There was a significant relationship between preoperative perfusion index with the incidence (p = 0.005) and the degree (p = 0.014) of post-anaesthetic shivering. The preoperative perfusion index cut-off value based on the ROC curve was 4.2 (AUC = 0.762, p = 0.002) with a sensitivity of 73.9% and specificity of 88.2%. Participants with preoperative PI < 4.2 had a greater risk of post-anaesthetic shivering (p < 0.001, RR = 3.13).

CONCLUSION

Preoperative perfusion index less than 4.2 can predict post-anaesthetic shivering in patients undergoing caesarean section with spinal anaesthesia.

Prediction of spinal anesthesia-induced hypotension during elective cesarean section: a systematic review of prospective observational studies

BACKGROUND

Spinal anesthesia is the standard for elective cesarean section but spinal anesthesia-induced hypotension remains an important problem. Accurate prediction of hypotension could enhance clinical decision-making, alter management, and facilitate early intervention. We performed a systematic review of predictors of spinal anesthesia-induced hypotension and their predictive value during cesarean section.

METHODS

PubMed, Embase, Cochrane Library, Google Scholar and Web of Science databases were searched for prospective observational studies assessing the diagnostic accuracy of predictors of spinal anesthesia-induced hypotension in elective cesarean section. The quality of studies was assessed and predictors were grouped in domains based on the type of predictor.

RESULTS

Thirty-eight studies (n=3086 patients) were included. In most studies, patients received 500-1000 mL crystalloid preload or 500-2000 mL crystalloid coload. Vasopressors for post-spinal hypotension were boluses of ephedrine 5-15 mg and/or phenylephrine 25-100 µg in most studies. The hypotension rate varied from 29% to 80% based on the definition. For analysis, >30 predictors were classified into seven domains: demographic characteristics, baseline hemodynamic variables, baseline sympathovagal balance, postural stress testing, peripheral perfusion indices, blood volume and fluid responsiveness indices, and genetic polymorphism.

CONCLUSIONS

Environmental and individual factors increased outcome variability, which restricted the value of the autonomic nervous system and peripheral perfusion indices for prediction of spinal anesthesia-induced hypotension. Supine stress tests may reflect parturients' cardiovascular tolerance during hemodynamic fluctuations and may optimize the predictive value of static state predictors. Future research for predicting spinal anesthesia-induced hypotension should focus on composite and dynamic parameters during the supine stress tests.

Predictability of preoperative carotid artery-corrected flow time for hypotension after spinal anaesthesia in patients undergoing caesarean section: A prospective observational study

BACKGROUND

Spinal anaesthesia-induced hypotension is frequently reported in patients undergoing caesarean section. Mechanistically, sympathetic blockade reduces the systemic vascular resistance and the left ventricular preload, causing hypotension, which is augmented by aortocaval compression. The corrected blood flow time (FTc) is affected by the preload and is inversely related to the afterload.

OBJECTIVE

We hypothesised that the preanaesthetic carotid artery FTc could predict hypotension after induction in patients undergoing a caesarean section with spinal anaesthesia.

DESIGN

A prospective observational study.

SETTING

A tertiary referral centre in South Korea from September 2018 to November 2019.

PARTICIPANTS

Thirty-eight parturients scheduled for elective caesarean section under spinal anaesthesia.

INTERVENTIONS

Using carotid ultrasonography, FTc was measured twice prior to inducing spinal anaesthesia. FTc was calculated using both Bazett's (B) and Wodey's (W) formulae. Hypotension was defined as an SBP decrease to less than 80 mmHg, or less than 75% of baseline, or if symptoms consistent with hypotension occurred from the time of injection of the spinal anaesthetic until delivery.

MAIN OUTCOME MEASURES

The primary endpoint was to determine the predictive value of preanaesthetic FTc for postspinal hypotension during caesarean delivery.

RESULTS

Among the 35 patients who completed this study, hypotension occurred in 21 (60%). The areas under the receiver-operating characteristic curves for FTc (B) and FTc (W) were 0.905 [95% confidence interval (CI), 0.757 to 0.978, P < 0.001] and 0.922 (95% CI, 0.779 to 0.985, P < 0.001), respectively. The optimal cut-off values for predicting hypotension were 346.4 and 326.9 ms, respectively. The grey zone for FTc (B) and FTc (W) included 40 and 14% of the patients, respectively.

CONCLUSION

Preanaesthetic carotid artery FTc was a reliable indicator of postspinal hypotension in parturients. Considering the grey zone, Wodey's formula is better than Bazett's formula.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03631329.

Correlation between the Perfusion Index and Intraoperative Hypothermia: A Prospective Observational Pilot Study

Background and Objectives: We examined the association between the baseline perfusion index (PI) and changes in intraoperative body temperature during general anesthesia. The PI reflects the peripheral perfusion state. The PI may be associated with changes in body temperature during general anesthesia because the degree of redistribution of body heat from the central to the peripheral compartment varies depending on the peripheral perfusion state. Materials and Methods: Thirty-eight patients who underwent brain surgery were enrolled in this study. The baseline PI and body temperature of the patients were measured on entering the operating room. Body temperature was recorded every 15 min after induction of anesthesia using an esophageal temperature probe. Univariate and multivariate logistic regression analyses were performed to identify the risk factors for intraoperative hypothermia. Results: Eighteen patients (47 %) developed hypothermia intraoperatively. The baseline PI was significantly lower among patients in the hypothermia group (1.8 ± 0.7) than among those in the normothermia group (3.0 ± 1.2) (P < 0.001). The baseline PI and body temperature were independently associated with intraoperative hypothermia (PI: odds ratio [OR], 0.270; 95% confidence interval [CI], 0.105-0.697; P = 0.007, baseline body temperature: OR, 0.061; 95% CI, 0.005-0.743; P = 0.028). Conclusions: This study showed that low baseline PI was the factor most related to the development of intraoperative hypothermia. Future studies should consider the PI as a predictor of intraoperative hypothermia.

Causes of arterial hypotension during anesthetic induction with propofol investigated with perfusion index and ClearSightTM in young and elderly patients

BACKGROUND

Mechanism underlying the hypotension during anesthetic induction in elderly patients is inferred to differ from that in younger patients due to structural changes in arteries. The aim of the study was to determine if a decrease in cardiac output (CO) or systemic vascular resistance (SVR) is the main mechanism of the hypotension.

METHODS

Fifty-six patients comprising 28 healthy elderly patients aged 75-90 years (group E) and 28 healthy younger patients aged 20-40 years (group Y) were enrolled. General anesthesia was induced with propofol (1.2 mg/kg, group E; 2 mg/kg, group Y), remifentanil (0.15 µg/kg/min, group E; 0.3 µg/kg/min, group Y) and rocuronium. Primary outcome was to compare serial changes in PI of Radical-7^TM, SVR, CO and stroke volume variations (SVV) of ClearSight^TM (Edwards Lifesciences Corp., Irvine, CA, USA) during the five-minute period from propofol administration until intubation.

RESULTS

The degree of increase in PI and reduction in SVR in group Y were significantly greater than those in group E (P<0.01 with repeated measure ANOVA). The degree of reduction in CO and increase in SVV were significantly larger in group E (P<0.01). All values of mean arterial blood pressure measured during the five-minute correlated negatively with PI in group Y (r=0.44, P<0.01) and positively with CO in group E (r=0.4, P<0.01).

CONCLUSIONS

The main mechanisms of hypotension during anesthetic induction contribute to the decrease in CO in elderly and reduction of SVR in younger. PI only shows the vascular tone of a finger but can be a surrogate for SVR.

Utility of the Pleth Variability Index in predicting anesthesia-induced hypotension in geriatric patients

Background/aim

Anesthesia-induced hypotension may have negative consequences in geriatric patients. Therefore, predicting hypotension remains an important topic for anesthesiologists. Pleth Variability Index (PVI) measurement provides information about the fluid status and vascular tonus of patients. In this study, the ability of the Pleth Variability Index to predict hypotension after general anesthesia induction was evaluated.

Materials and methods

PVI values ​​obtained from pulse oximetry were recorded, in addition to preoperative standard anesthesia monitoring. The correlation between the PVI value and mean arterial pressure (MAP), systolic arterial blood pressure (SAP) changes, and the power of PVI values ​​to predict the incidence of hypotension after anesthesia induction (>20% MAP decrease) was tested.

Results

Eighty patients over 65 years of age who were operated under general anesthesia were included in the study. Hypotension was observed in 20 patients (25%). PVI values were mild and positively correlated with MAP changes (r = 0.195 and P = 0.041). According to receiver operating characteristic (ROC) analysis, the incidence of hypotension increased in patients with PVI values above 15.45%. We also found the following diagnostic results for PVI value for predicting hypotension: P = 0.044 and area under the ROC curve of 0.651 ± 0.073 (95% confidence interval (CI): 0.507–0.794), 40% sensitivity, 80% specificity, a PPV of 40%, an NPV of 80%, a cut-off value of 15.45, a positive likelihood ratio of 2, a negative likelihood ratio of 0.75, and a Youden Index of 0.2.

Conclusion

Predicting hypotension in geriatric patients is an important issue for anesthesiologists. As an easily applicable test, the Pleth Variability Index is useful in predicting MAP reduction in patients. This practical technique can be used routinely in all geriatric patient groups.

The transverse diameter of right common femoral vein by ultrasound in the supine position for predicting post-spinal hypotension during cesarean delivery

Background

Post-spinal anesthesia hypotension during cesarean delivery is caused by decreased systemic vascular resistance due to the blockage of the autonomic nerves, which is further worsened by inferior vena cava (IVC) compression by the gravid uterus. This study aimed to assess whether peak velocity and diameter of the IVC below the xiphoid or right common femoral vein (RCFV) in the inguinal region, as measured on ultrasound, could reflect the degree of IVC compression and further identify parturients at risk of post-spinal hypotension.

Methods

Fifty-six parturients who underwent elective cesarean section with spinal anesthesia were included in this study; peak velocities and anteroposterior diameters of the IVC and peak velocities and transverse diameters of the RCFV were measured using ultrasound before anesthesia. The primary outcome was the ultrasound measurements of IVC and RCFV acquired before spinal anesthesia and their association with post-spinal hypotension. Hypotension was defined as a drop in systolic arterial pressure by > 20% from the baseline. Multinomial logistic regression analysis was used to identify the association between the measurements of IVC, RCFV, and post-spinal hypotension during cesarean delivery. Receiver operating characteristic curves were used to test the abilities of the identified parameters to predict post-spinal hypotension; the areas under the curve and optimum cut-off values for the predictive parameters were calculated.

Results

A longer transverse diameter of the RCFV was associated with the occurrence of post-spinal hypotension (odds ratio = 2.022, 95% confidence interval [CI] 1.261–3.243). The area under the receiver operating characteristics curve for the prediction of post-spinal hypotension was 0.759 (95% CI 0.628–0.890, P = 0.001). A transverse diameter of > 12.2 mm of the RCFV could predict post-spinal hypotension during cesarean delivery.

Conclusions

A longer transverse diameter of RCFV was associated with hypotension and could predict parturients at a major risk of hypotension before anesthesia.

Trial registration

This study was registered at http://www.chictr.org.cn on 16, May, 2018. No. ChiCTR1800016163.

To study the role of perfusion index as a predictor of hypotension during spinal anesthesia in lower segment cesarean section – A prospective observational study

Background and Aims:

Spinal anesthesia has become the choice of neuraxial anesthesia for cesarean delivery. Hypotension, the most common side effect of spinal anesthesia is more in parturients. Perfusion index (PI) is one of the newest methods, used noninvasively for the prediction of hypotension postspinal anesthesia, evaluation of regional block success, and a tool for pain assessment. In our study, we have used PI for predicting the occurrence of hypotension postsubarachnoid block in elective lower segment cesarean section (LSCS).

Methods:

In this prospective observational study, parturients posted for elective LSCS under spinal anesthesia were included. Spinal anesthesia was performed at L₃-L₄ interspace using 25G (gauge) Quincke needle, with 1.8 mL of 0.5% hyperbaric bupivacaine plus 20 μg fentanyl. Hypotension was defined as a decrease in systolic blood pressure >25% from the baseline.

Statistical Analysis Used:

Statistical analysis was performed using the paired sample t-test, Chi-square test, and independent t-test.

Results:

From our study, we had found that a positive correlation exists between the baseline PI of the patient and the occurrence of hypotension intraoperatively. A cutoff value of 1.75 (with P < 0.001) was found to be significant; above which the occurrence of hypotension was definite. The sensitivity of this cutoff value was 75% and specificity was 71% for this value.

Conclusion:

Baseline perfusion of >1.75 can predict hypotension postspinal anesthesia in LSCS. The incidence of hypotension was about 93% in parturients whose baseline was above the cutoff value.

Observation of hemodynamic parameters using a non-invasive cardiac output monitor system to identify predictive indicators for post-spinal anesthesia hypotension in parturients undergoing cesarean section

The administration of high-level spinal anesthesia for cesarean section may lead to significant hemodynamic changes. Bioreactance-based non-invasive cardiac output monitoring (NICOM^™) provides an accurate monitoring system for parturients under spinal anesthesia. The present study hypothesized that baseline hemodynamic parameters obtained via the NICOM^™ system could serve as predictive indicators for post-spinal anesthesia hypotension. Therefore, 80 full-term parturients with singleton pregnancies who underwent scheduled cesarean section were enrolled and allocated to either a supine position group or a 15˚ left tilt group. All parturients received standard pre-hydration with 750 ml of 0.9% saline. Baseline cardiac output index (CI), total peripheral resistance index (TPRI) and stroke volume (SV) were recorded using the NICOM^™ system. Subsequently, spinal anesthesia with 2.4 ml of 0.5% hyperbaric bupivacaine, 10 µg of fentanyl and 0.2 mg of morphine was administered. Receiver operating characteristic (ROC) curves and multivariate logistic regression were used to analyze the data. A total of 40 parturients (51.9%) developed hypotension. The areas under the ROC curves were 0.666, 0.594 and 0.622 for the CI, TPRI and SV, respectively. The optimal cut-off value of the CI in predicting hypotension was 3.68 l/min/m² (ROC, sensitivity=85.0%, specificity=48.6%). Furthermore, CI was considered as an independent factor for post-spinal anesthesia hypotension. In conclusion, the baseline CI obtained via the bioreactance-based NICOM^™ system may serve as a predictor of post-spinal anesthesia hypotension in parturients regardless of patient position.

Evaluating the Relationship between the Pleth Variability Index and Hypotension and Assessing the Fluid Response in Geriatric Hip Fracture under Spinal Anaesthesia: An Observational Study

OBJECTIVE

We aimed to test the efficacy of the pre-operative Pleth variability index (PVI) in evaluating hypotension that developed after spinal anaesthesia in patients who were spontaneously breathing, pre-operatively hypovolemic, and were at an advanced age.

METHODS

This observational study included 94 patients aged >65 years with hip fracture. Demographic data, pre-operative heart rate, non-invasive arterial pressures, PVI values, and haemogram values were continuously measured following spinal anaesthesia. The measurements with and without hypotension were distinguished and their data were compared.

RESULTS

The mean age of the patients was 77.4±8.2 years. In total, 56.4% of the patients developed hypotension after spinal anaesthesia, and hypotension was higher in women (p=0.037). Low pre-operative diastolic arterial pressures values were associated with the development of hypotension (p=0.037). The relationship between PVI and post-spinal hypotension was negative but significant (r=-0.239; p<0.05). Depending on the volume loss, an increase in the PVI (p<0.001) and its subsequent significant decrease after treatment in patients with hypotension (p<0.001) was observed. The correlation between noninvasively measured haemoglobin values and the values obtained from arterial blood gas samples was significant (p<0.001).

CONCLUSION

This study showed that post-spinal hypotension may be associated with increased as well as decreased PVI values. However, these values cannot be clinically used for predicting pre-operative hypotension in hypovolemic patients.

Discrepancy in finger pulse oximetry reading related to positioning: a case report

Pulse oximetry is one of the five cardinal vital signs used to monitor patients in the clinical setting, and has contributed significantly to patient safety. Unfortunately, extremes in patient positioning may lead to changes in peripheral perfusion pressures resulting in erroneous pulse oximetry readings. We present a case of a relatively well patient coming for robot-assisted laparoscopic radical prostatectomy who became hypoxic in the Trendelenburg position that spontaneously resolved upon transiting to supine. The reliability of the traditional method of assessing the pulse oximeter value via the plethysmograph is questioned and we discuss other modalities to assist in interpretation of the suspicious pulse oximetry reading.

Do changes in perfusion index reflect changes in stroke volume during preload-modifying manoeuvres?

Changes in stroke volume (deltaSV) induced by a lung recruitment manoeuvre (LRM) have been shown to accurately predict fluid responsiveness during protective mechanical ventilation. Cardiac output monitors are used in a limited number of surgical patients. In contrast, all patients are monitored with a pulse oximeter, that may enable the continuous monitoring of a peripheral perfusion index (PI). We postulated that changes in PI (deltaPI) may reflect deltaSV during brief modifications of cardiac preload. We studied 47 patients undergoing neurosurgery and ventilated with a tidal volume of 6-8 ml/kg. All patients were monitored with a pulse contour system enabling the continuous monitoring of SV and with a pulse oximeter enabling the continuous monitoring of PI. LRMs were performed by increasing airway pressure up to 30 cmH₂0 for 30 s. Fluid loads (250 ml of saline 0.9% in 10 min) were performed only in patients who experienced a deltaSV > 30% during LRMs (potential fluid responders). LRMs induced a 26% decrease in SV (p < 0.05) and a 27% decrease in PI (p < 0.05). We observed a fair relationship between deltaPI and deltaSV (r² = 0.34). A deltaPI ≥ 26% predicted a deltaSV > 30% with a sensitivity of 83% and a specificity of 78%  (AUC  =  0.84, 95%CI 0.71-0.93). 24 patients experienced a deltaSV > 30% and subsequently received fluid. Fluid loads induced a 16% increase in SV and a 17% increase in PI, but fluid-induced deltaPI and deltaSV were weakly correlated (r² = 0.19). In neurosurgical patients, we conclude that deltaPI may be used as a surrogate for deltaSV during LRMs but not during fluid loading.

Tissue Oxygen Saturation Change on Upper Extremities After Ultrasound-Guided Infraclavicular Brachial Plexus Blockade; Prospective Observational Study

Background and Objective: The aim of this study was to investigate whether tissue oxygen saturation (StO2) is a reliable and objective method for assessing the adequacy of infraclavicular block and to describe the time course of StO2 changes. Materials and Methods: In this prospective observational study, StO2 was measured in 40 patients planned for elective hand surgery under infraclavicular block. Noninvasive StO2 monitoring was used prior to ultrasound-guided infraclavicular brachial plexus block and during the first 30 min of the blockade. Sensory and motor blocks were evaluated every 5 min followed by pinprick testing and Bromage scale. Results: Preanesthetic median StO2 values of the blocked side and nonblocked side were similar (p = 0.532), whereas the postanesthetic values of the blocked side were higher. At the fifth minute and the following minute, measurements compared to the nonblocked side (p < 0.001). The median StO2 values increased significantly, which increased by 4.5% at 5 min, by another 5.5% at 30 min, and by an average of 1% from 5 to 30 min compared to the baseline values in the blocked side. The responses of the patients to the questions probed in the pinprick test and Bromage scale were fully compatible with the data obtained by the near-infrared spectroscopy (NIRS) method. Conclusions: StO2 monitoring may provide a useful instrument for rapid evaluation of the success of regional anesthesia in the upper extremity.

The effects of passive leg raising may be detected by the plethysmographic oxygen saturation signal in critically ill patients

BACKGROUND

A passive leg raising (PLR) test is positive if the cardiac index (CI) increased by > 10%, but it requires a direct measurement of CI. On the oxygen saturation plethysmographic signal, the perfusion index (PI) is the ratio between the pulsatile and the non-pulsatile portions. We hypothesised that the changes in PI could predict a positive PLR test and thus preload responsiveness in a totally non-invasive way.

METHODS

In patients with acute circulatory failure, we measured PI (Radical-7) and CI (PiCCO2) before and during a PLR test and, if decided, before and after volume expansion (500-mL saline).

RESULTS

Three patients were excluded because the plethysmography signal was absent and 3 other ones because it was unstable. Eventually, 72 patients were analysed. In 34 patients with a positive PLR test (increase in CI ≥ 10%), CI and PI increased during PLR by 21 ± 10% and 54 ± 53%, respectively. In the 38 patients with a negative PLR test, PI did not significantly change during PLR. In 26 patients in whom volume expansion was performed, CI and PI increased by 28 ± 14% and 53 ± 63%, respectively. The correlation between the PI and CI changes for all interventions was significant (r = 0.64, p < 0.001). During the PLR test, if PI increased by > 9%, a positive response of CI (≥ 10%) was diagnosed with a sensitivity of 91 (76-98%) and a specificity of 79 (63-90%) (area under the receiver operating characteristics curve 0.89 (0.80-0.95), p < 0.0001).

CONCLUSION

An increase in PI during PLR by 9% accurately detects a positive response of the PLR test.

TRIAL REGISTRATION

ID RCB 2016-A00959-42. Registered 27 June 2016.

Peripheral perfusion index does not accurately reflect hypoperfusion in healthy dogs undergoing elective ovariohysterectomy

This study evaluated the variability of the peripheral perfusion index (PI) in 22 anaesthetised female dogs undergoing elective ovariohysterectomy and examined the relationship between peripheral PI and heart rate, blood pressure, blood pH, end tidal CO₂ (EtCO₂), O₂ saturation (SpO₂), core-peripheral temperature gradient (ΔTc-p), partial pressure of CO₂ (PCO₂), and concentrations of glucose, cortisol, lactate and bicarbonate (HCO₃^-). Blood pH, lactate and glucose concentrations were determined 15, 30, 45min into the ovariohysterectomy procedure and after extubation. Cortisol concentrations were assessed before anaesthesia and after extubation. Other variables were recorded at every 5min throughout the ovariohysterectomy procedure. Hyperglycaemia was observed in 59% of bitches during surgery, but serum cortisol concentrations remained unchanged. Most measures of perfusion (ΔTc-p, pH, PCO₂, EtCO₂, SpO₂) and heart rate remained unchanged throughout anaesthesia and did not correlate with peripheral PI. Mean arterial pressure increased during the ovariohysterectomy procedure, while peripheral PI decreased, resulting in negative correlations between these variables at 30 and 45min. Lactate concentrations decreased from baseline to the time of measurement post-extubation. Peripheral PI gradually decreased during the ovariohysterectomy procedure, probably reflecting vasoconstriction induced by nociceptive stimuli. Using lactate concentrations as the reference standard for peripheral perfusion, low peripheral PI in healthy bitches undergoing ovariohysterectomy might not represent peripheral hypoperfusion.