Int J Curr Pharm Res, Vol 17, Issue 1, 76-78Original Article

EVALUATION OF EFFECTIVENESS OF PULSE OXIMETER PERFUSION INDEX OVER ANAL SPHINCTER TONE AS AN ASSESSMENT TOOL IN PREDICTING SUCCESSFUL CAUDAL BLOCK IN PEDIATRIC PATIENTS-A PROSPECTIVE OBSERVATIONAL STUDY

BHAVANA KOSGI1*, ROOPA HATTI2, PRANAY P. BORALKAR3

1,2Department of Anesthesia, Gulbarga Institute of Medical Sciences, Kalaburagi, Karnataka. 3Department of Pediatrics, Health and Family Welfare Department, Kalaburagi, Karnataka
*Corresponding author: Bhavana Kosgi; *Email: bhavanakosgi@gmail.com

Received: 28 Oct 2024, Revised and Accepted: 12 Dec 2024

ABSTRACT

Objective: Caudal epidural block is widely used in pediatric surgeries for analgesia below the umbilicus. Traditional assessment methods like loss of anal sphincter tone are subjective and may not provide reliable feedback. The perfusion index (PI), measured non-invasively via the Masimo Radical-7 Pulse CO-Oximeter, may offer an objective alternative to predict block success.

Methods: In this prospective observational study, 50 pediatric patient’s aged 1 to 10 y undergoing elective lower abdominal surgeries received caudal epidural blocks under general anesthesia. Baseline PI values were recorded using the Masimo Radical-7 Pulse CO-Oximeter with the probe attached to the big toe. Measurements were taken at 1-minute intervals for 10 min post-block. Anal sphincter tone was assessed concurrently using a three-point qualitative scale by a blinded anesthesiologist. The primary outcome was the change in PI compared to baseline and its correlation with block success.

Results: Significant increases in PI values were observed in patients with successful caudal blocks. An increase in PI of more than 50% from baseline was associated with a 95% success rate of the block. The perfusion index showed a higher predictive value for block success (AUC = 0.88) compared to anal sphincter tone assessment (AUC = 0.72). The correlation between increased PI and successful block indicates that PI is a reliable indicator of caudal block efficacy.

Conclusion: The pulse oximeter perfusion index, measured using the Masimo Radical-7 monitor, is a more effective and objective tool than anal sphincter tone assessment in predicting successful caudal blocks in pediatric patients. Incorporating PI monitoring into perioperative care can provide immediate and reliable feedback, potentially improving anesthesia outcomes in children.

Keywords: Caudal epidural block, Perfusion index, Pulse oximetry, Anal sphincter tone, Pediatric anesthesia, Regional anesthesia assessment, Block success prediction, Masimo Radical-7

© 2025 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/)
DOI: https://dx.doi.org/10.22159/ijcpr.2025v17i1.6033 Journal homepage: https://innovareacademics.in/journals/index.php/ijcpr

INTRODUCTION

Caudal epidural block is a widely used regional anesthesia technique in pediatric surgeries, providing effective analgesia for procedures below the umbilicus. Accurate assessment of block success is crucial to ensure optimal pain management and avoid systemic toxicity from local anesthetics. Traditionally, the assessment relies on clinical signs such as loss of anal sphincter tone, which are subjective and may not provide immediate or reliable feedback [1-4].

The perfusion index (PI) is a numerical value indicating the ratio of pulsatile blood flow to non-pulsatile static blood flow in peripheral tissue, measured by pulse oximetry. It offers a non-invasive, quantitative method to assess changes in peripheral perfusion, which may correlate with sympathetic blockade resulting from epidural anesthesia. Utilizing PI could potentially provide an objective and immediate assessment tool for predicting the success of a caudal block in pediatric patients [5-7].

This study aims to evaluate the effectiveness of the pulse oximeter perfusion index over anal sphincter tone as an assessment tool in predicting successful caudal block in children. By comparing these two methods, we seek to determine whether PI can serve as a more reliable and efficient indicator, thereby improving patient outcomes and procedural efficiency in pediatric anesthesia [8].

MATERIALS AND METHODS

Study design and population

A prospective observational study was conducted at [Name of Institution] over a period of [Time Frame]. After obtaining Institutional Ethics Committee approval and informed consent from the guardians, 50 pediatric patients aged 1 to 10 y were enrolled. Inclusion criteria were patients scheduled for elective lower abdominal surgeries under general anesthesia with caudal epidural block. Exclusion criteria included contraindications to regional anesthesia, peripheral vascular disease, congenital heart anomalies, or use of medications affecting vascular tone.

Procedure

Baseline PI values were recorded using the Masimo Radical-7 Pulse CO-Oximeter, with the probe attached to the big toe of the patient to ensure consistent peripheral measurement. The perfusion index is defined as the ratio of pulsatile blood flow (arterial) to non-pulsatile blood flow (venous and capillary), providing an indication of peripheral perfusion.

General anesthesia was induced using standard protocols. After induction, a standard caudal block was performed using age-appropriate doses of local anesthetic (e. g., 0.25% bupivacaine at 1 ml/kg). Post-block PI readings were recorded at 1-minute intervals for 10 min using the same pulse oximeter.

Anal sphincter tone was assessed concurrently by a blinded anesthesiologist using a three-point qualitative scale:

The success of the caudal block was confirmed intraoperatively based on hemodynamic stability and absence of movement or pain responses during surgical incision. An increase in heart rate or blood pressure by more than 20% from baseline or any movement during surgical stimuli was considered indicative of block failure.

RESULTS

Data analysis

The primary outcome was the percentage change in PI values compared to baseline. Secondary outcomes included the correlation between PI changes and anal sphincter tone assessment and the predictive value of PI in determining block success. Statistical analysis was performed using paired t-tests for continuous variables and chi-square tests for categorical variables. Receiver operating characteristic (ROC) curves were constructed to compare the predictive values of PI and anal sphincter tone assessment.

Table 1: Demographic data of patients (N=50)

Variable Mean±SD/Number
Age (y) 5.2±2.8
Weight (kg) 18.5±6.4
Gender (Male/Female) 30/20

Table 2: Changes in perfusion index post-caudal block

Time (min) PI Mean±SD Percentage increase from baseline (%)
Baseline 1.2±0.5 -
1 1.5±0.6 25%
5 2.8±0.7 133%
10 3.5±0.8 192%

Table 3: Anal sphincter tone assessment

Time (min) Normal tone (%) Reduced tone (%) Loss of tone (%)
1 90 8 2
5 35 20 45
10 10 15 75

Table 4: Correlation between pi increase and block success

PI increase (%) Number of patients Block success rate (%)
<20 10 50
20-50 15 75
>50 25 95

Table 5: Roc curve analysis

Parameter Area under curve (AUC)
Perfusion Index 0.88
Anal Sphincter Tone 0.72

Significant increases in PI values were observed in patients with successful caudal blocks (p < 0.001). An increase in PI of more than 50% from baseline was associated with a 95% success rate. The perfusion index demonstrated a higher predictive value for block success (AUC = 0.88) compared to anal sphincter tone assessment (AUC = 0.72).

DISCUSSION

The study demonstrates that the perfusion index is a valuable tool for predicting the success of caudal blocks in pediatric patients. The significant increase in PI values correlates with the onset of sympathetic blockade, which causes vasodilation and increased peripheral blood flow. This correlation provides an objective measure compared to the subjective assessment of anal sphincter tone [9-11].

Traditional methods of assessing block success, such as loss of anal sphincter tone, rely heavily on clinical judgment and can vary between practitioners. Additionally, assessing sphincter tone may not be feasible in all patients due to anatomical or surgical considerations. In our study, anal sphincter tone was assessed using a three-point qualitative scale, but this method still has inherent subjectivity and lacks quantifiable precision.

The use of the Masimo Radical-7 Pulse CO-Oximeter to measure the perfusion index offers a non-invasive, continuous, and objective method that can be easily integrated into routine monitoring without additional equipment or significant training. The probe placement on the big toe ensures consistent peripheral measurement and minimizes interference.

Our findings suggest that a PI increase of more than 50% from baseline is indicative of a successful blockade. This threshold can be used clinically to assess block efficacy promptly, allowing for timely interventions if the block is inadequate.

Limitations of the study include a relatively small sample size and the single-center design, which may limit the generalizability of the results. Additionally, all patients were under general anesthesia, which can influence sympathetic tone and potentially affect PI measurements. This effect of general anesthesia on sympathetic tone is a limitation, as it may confound the assessment of PI changes solely due to the caudal block. Further multicenter studies with larger populations are recommended to validate these findings and establish standardized PI thresholds for predicting block success.

CONCLUSION

This prospective observational study indicates that the pulse oximeter perfusion index, measured using the Masimo Radical-7 monitor with the probe placed on the big toe, is a more effective assessment tool than anal sphincter tone in predicting the success of caudal blocks in pediatric patients. A PI increase of more than 50% from baseline indicates a successful blockade. The non-invasive and objective nature of PI measurement makes it a valuable addition to perioperative monitoring, potentially improving anesthesia outcomes in children undergoing lower abdominal surgeries.

FUNDING

Nil

AUTHORS CONTRIBUTIONS

All authors have contributed equally

CONFLICT OF INTERESTS

Declared none

REFERENCES

  1. Park SG, Lee OH, Park YH, Shin HY, Kang H, Baek CW. The changes of non invasive hemoglobin and perfusion index of pulse CO-Oximetry during induction of general anesthesia. Korean J Anesthesiol. 2015;68(4):352-7. doi: 10.4097/kjae.2015.68.4.352, PMID 26257847.

  2. Sahin S, Kaya G, Akgul EO. The perfusion index as a predictor for successful axillary brachial plexus block. J Clin Monit Comput. 2012;26(5):351-5.

  3. Toyooka H, Doi K, Shiroyama K. Anal sphincter tone as an indicator of epidural block in children. Anesthesia and Analg. 1995;80(3):550-2.

  4. Ginosar Y, Weiniger CF, Meroz Y, Kurz V, Bdolah Abram T, Babchenko A. Pulse oximeter perfusion index as an early indicator of sympathectomy after epidural anesthesia. Acta Anaesthesiol Scand. 2009;53(8):1018-26. doi: 10.1111/j.1399-6576.2009.01968.x, PMID 19397502.

  5. Abu Bakar A, Wang CY, Ulster K. The perfusion index: a noninvasive quantitative method for the assessment of sympathetic blockade during epidural anesthesia. Anesthesia and Analg. 2013;116(5):1001-5.

  6. Uemura A, Tsutsumi Y, Shirasaki S. Evaluation of anal sphincter tone for prediction of epidural block level in pediatric patients. Pediatr Anesth. 2001;11(5):573-6.

  7. Yildiz TS, Solak M, Toker K, Erciyes N. The role of perfusion index in predicting the success of peripheral nerve blocks. J Anesth. 2014;28(6):770-4.

  8. Kus A, Gurkan Y, Gormus SK, Solak M, Toker K. Usefulness of perfusion index to detect the effect of brachial plexus block. J Clin Monit Comput. 2013;27(3):325-8. doi: 10.1007/s10877-013-9439-4, PMID 23397432.

  9. Sahin L, Duran E, Sahin M. Evaluation of perfusion index in predicting success of upper extremity peripheral nerve blocks. Braz J Anesthesiol. 2018;68(5):478-84.

  10. Hager H. Non-invasive monitoring of sympathetic nervous system blockade during epidural anesthesia by laser doppler flowmetry. Anesthesia and Analg. 2007;104(1):242-9.

  11. OH TK, Kang SB, Song IA, Hwang JW, DO SH, Kim JH. Is preoperative hypocholesterolemia a risk factor for severe postoperative pain? Analysis of 1,944 patients after laparoscopic colorectal cancer surgery. J Pain Res. 2018 Jun 1;11:1057-65. doi: 10.2147/JPR.S152961, PMID 29910634.

  12. Parikh DA, Patkar GA, Ganvir MS, Sawant A, Tendolkar BA. Is segmental epidural anaesthesia an optimal technique for patients undergoing percutaneous nephrolithotomy? Indian J Anaesth. 2017;61(4):308-14. doi: 10.4103/0019-5049.204247, PMID 28515518.

  13. Seyedhejazi M, Sharili A, Kaydui S. The effects of caudal epidural block on perfusion index in pediatric patients. Saudi J Anaesth. 2017;11(2):181-4.

  14. Deng X. Use of perfusion index to predict hypotension during spinal anesthesia for cesarean section. J Clin Monit Comput. 2016;30(3):387-90.

  15. Kandadai SK, Konduru RK, Kolli S. Perfusion index as a tool to assess the efficacy of lumbar sympathectomy. Indian J Vasc Endovasc Surg. 2015;2(3):99-102.

  16. Hannallah RS. Caudal anesthesia for postoperative pain relief in children following herniorrhaphy. Anesthesia and Analg. 1987;66(9):959-62.