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Year : 2023  |  Volume : 17  |  Issue : 1  |  Page : 7-11

Perfusion index during endotracheal intubation and extubation: A prospective observational study

Department of Anaesthesiology, GSMC and KEMH, Parel, Mumbai, Maharashtra, India

Correspondence Address:
Prerana N Shah
Department of Anaesthesiology, GSMC and KEMH, Mumbai - 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sja.sja_539_22

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Date of Submission21-Jul-2022
Date of Acceptance05-Aug-2022
Date of Web Publication02-Jan-2023


Introduction: Perfusion index (PI) can be detected using a pulse oximeter. Its value decreases in response to noxious stimuli. Here, we investigated its efficacy in detecting hemodynamic responses during endotracheal intubation and extubation.
Methods: An approval from the institutional ethics committee was obtained along with a written informed consent from the patients involved in this study. A sample size of 30 was calculated. Reading of PI, heart rate, and blood pressures (systolic, diastolic, and mean arterial) were recorded at pre-intubation, post-intubation, during neuromuscular block reversal, pre-extubation and at extubation. Clinically significant heart rate, blood pressure (systolic, diastolic, and mean) and PI was defined as increase by >10 bpm, rise by ≥15 bpm and a decrease by ≥10%, respectively, from pre-intubation value.
Results: Clinically significant change in PI was seen at all intervals with maximum decrease in PI occurring during neuromuscular block reversal (42.6% at the start and 56.7% at the end of neuromuscular block reversal). A negative correlation was noted between PI and the other non-invasive hemodynamic parameters.
Conclusion: PI decreases on noxious stimuli and correlates negatively with the other non-invasive hemodynamic parameters. Hemodynamic response at neuromuscular block reversal is maximum.

Keywords: Hypotension, laryngoscopy, perfusion index

How to cite this article:
Shah PN, Kezo A. Perfusion index during endotracheal intubation and extubation: A prospective observational study. Saudi J Anaesth 2023;17:7-11

How to cite this URL:
Shah PN, Kezo A. Perfusion index during endotracheal intubation and extubation: A prospective observational study. Saudi J Anaesth [serial online] 2023 [cited 2023 Mar 31];17:7-11. Available from:

  Introduction Top

Perfusion index (PI) is a non-invasive hemodynamic monitor which can be detected by the use of a standard pulse oximeter. As it is a monitor of peripheral perfusion, its values increase and decrease during events causing local vasodilation and vasoconstriction respectively.[1] Stressful response to endotracheal intubation and extubation has been found to cause hemodynamic changes with increase in heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP).[2] PI, in any stressful response, is expected to decrease as a result of vasoconstriction.[2],[3]

Hager et al.[3] found that PI could correctly assess changes in peripheral perfusion caused by inhalational agents like sevoflurane and may be of use in the future to assess perioperative changes in peripheral perfusion as a result of different anesthetic conditions. This study seeks to assess if PI can be used as an alternative to the other non-invasive hemodynamic monitors (HR, SBP, DBP, and MAP).

  Aims and Objectives Top

Primary objective

To observe PI changes as compared to pre-operative values during endotracheal intubation with laryngoscopy and extubation

Secondary objective

To observe changes in the other non-invasive hemodynamic parameters (HR, SBP, DBP, and MAP) during intubation and extubation and look for correlation if any with PI.

Type of study

Prospective analytical observational study.

  Materials and Methods Top

This study was registered under clinical trial registry of India (Trial number CTRI/2016/12/007619). An institutional ethics committee approval and a well written and informed consent were obtained to conduct this study on 30 patients. Sample size was calculated using STATA[2] keeping power of study at 80% and α-error at 5%. Those between the ages of 18 years and 65 years undergoing general anesthesia with endotracheal intubation and belonging to ASA physical statuses I and II were included in the study while those who refused to give consent or suffering from severe systemic diseases or where difficult airway was anticipated were excluded from the study.

On the day of surgery, starvation and pre-operative findings (clinical examination and investigations) were confirmed after which the patients were wheeled into the operation theatre. Standard multi-parameter monitor (Mindray Beneview T5/T5 OR) to monitor PI, HR, and blood pressure (BP) using pulse oximeter, electrocardiogram, and non-invasive blood pressure (NIBP), respectively, was used. Pulse oximeter was attached to the middle finger and wrapped with a towel to reduce interference by ambient light. Pre-operative readings of PI, HR, and BP were recorded. A 20G intravenous cannula was inserted in the hand contralateral to the one where NIBP was attached and a 500 ml Lactated Ringer's solution was attached to it.

Standard general anesthesia was administered using intravenous midazolam 0.02, pentazocine 0.6, propofol 2, and rocuronium 0.6 Tracheal tube (7.0 mm for females and 8.0 mm for males) was used for intubation by laryngoscopy. HR, NIBP (SBP, DBP, MAP), and PI were measured at pre-intubation, post-intubation (1st, 3rd, and 5th minutes), during neuromuscular block (NMB) reversal (at the start and end of intravenous neostigmine), pre-extubation, and post-extubation (1st, 3rd, and 5th minute).

Clinically significant HR, SBP, DBP, MAP, and PI was defined as increase in HR by >10 bpm, rise in BP (SBP, DBP, MAP) by ≥15 bpm and a decrease in PI by ≥10% from pre-intubation value.

Statistical analysis

Using SPSS 16.0 (Chicago, IL) statistical analysis was performed. Continuous data was presented as either mean ± standard deviation (SD) or median [range] and categorical data was presented as proportions. Since our study had more than three hemodynamic parameters, an ANOVA with repeated measures (RMs) has been used to compare each event.

The P value was calculated by Holm-Sidak method. To find a correlation between PI and the other hemodynamic parameters, Pearson correlation was used. P < 0.05 is kept as significant for all the statistical analysis.

  Results Top

Clinically significant change in PI [Table 1] was seen at all intervals except during the 3rd and 5th minute post-intubation. HR showed clinically significant rise in all intervals except at 3rd and 5th minutes of both post-intubation and post-extubation. SBP on the other hand showed a clinically significant increase at all intervals. Clinically significant rise in DBP was seen at all intervals except at 5th minute post-intubation and 3rd and 5th minutes post- extubation, while in MAP, all intervals except the 5th minute post-extubation showed clinically significant rise.
Table 1: Change in non-invasive hemodynamic parameters during pre-intubation, post-intubation, neuromuscular block reversal, and post-extubation

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HR, SBP, DBP, and MAP showed negative correlation with PI. While correlation with PI was seen to be statistically significant during the post-extubation period for HR (at 1st, 3rd, and 5th minutes with P values of 0.003, 0.009, and 0.004, respectively), SBP (at 1st minute only with P value of 0.016), and MAP (at 1st and 5th minute with P values of 0.015 and 0.047, respectively) while DBP showed no statistically significant correlation with PI.

  Discussion Top

The possibility of using the pulse oximeter for more than just monitoring HR and oxygen saturation has sparked a curiosity of its varied employment. It has been positively suggested for predicting the intravascular insertion of epidural catheter,[4] fluid responsiveness in critical care[5] and depth of anesthesia.[6]

Here, 30 patients undergoing general anesthesia were observed prospectively during intubation and extubation. Their hemodynamic responses, that is, HR, SBP, DBP, MAP, and PI were noted during intubation and extubation which was the primary objective of the study. As studies have mentioned about various hemodynamic, responses following intubation,[7],[8] extubation,[7],[9]and NMB reversal,[10] the study also aimed to find if there was any correlation of PI with the other hemodynamic parameters (HR, SBP, DBP, MAP). A standard multi-para monitor available was used for recording during each event.

Pre-intubation values were taken as baseline for comparison.

The study done by us showed significant change of PI (i.e., a drop of >10% from the pre-intubation value) at all intervals except at 3rd and 5th minute post-intubation. Statistical significance was seen at the start and end of NMB reversal, pre-extubation and at 1st and 3rd minute post-extubation. There was a maximum fall of PI at the end of NMB reversal (-56.7%) and minimum fall at the 5th minute post-intubation (-3%). Atef et al.[2] found that the PI change was significant at post-intubation 1st minute (1.65 ± 0.54, PI change from pre-insertion value – 23.6%) and 3rd minute (1.94 ± 0.40, PI change from pre-insertion value – 10.18%) but not at the 5th minute post-intubation (2.12 ± 0.41, PI change from pre-insertion value – 1.85%).

Kakazu[11] and Yamazaki[12] prove that the value of PI increases with vasodilatation while another study by Hager[13] showed that noxious stimuli causes a fall in PI value due to vasoconstriction.

Our study found clinically and statistically significant change in HR at post-intubation –1st minute, start and end of NMB reversal, pre-extubation and post-extubation –1st minute. Change from pre-intubation value being 14.5 bpm, 11.7 bpm, 24 bpm, 21.94 bpm, and 14.94 bpm, respectively.

In their landmark paper, Reid and Brace[14] described the hemodynamic response to laryngoscopy and endotracheal intubation as a result of noxious stimuli in the upper airway. Laboratory data confirmed that stimulation of the epipharyngeal and laryngopharyngeal area augments cervical sympathetic activity in the efferent fibres to the heart resulting to an increase in the circulating catecholamine and ultimately an increase in HR and BP.

Although clinically significant increase in SBP and MAP was observed at all intervals, DBP had six intervals (post-intubation –1st and 3rd minutes, at the start and end of NMB reversal, pre-extubation and post-extubation –1st minute) that had clinically significant increase out of nine. Maximum increase in SBP was seen at the 1st minute post-intubation (from 113 ± 18.88 mmHg to 156.53 ± 40.45 mmHg, i.e., an increase of 42.86 mmHg) and least increase was seen at the 5th minute post-intubation (133.07 ± 30.73 mmHg, i.e., 20.16 mmHg increase from baseline).

For DBP, maximum increase was seen at the end of NMB reversal (from 72.17 ± 9.82 mmHg to 99.47 ± 14.33 mmHg, i.e., an increase by 27.3 mmHg) and minimum change at the 5th minute post-extubation with increase being 8.23 mmHg from baseline.

At the end of NMB block reversal maximum (from 85.33 ± 14.99 mmHg to 115.67 ± 17.55 mmHg, i.e., an increase by 30.34 mmHg) increase of MAP was observed while minimum change was observed at the 5th minute post-intubation (an increase by 15.17 mmHg).

Montazari[15] mentioned that hypertension, tachycardia, and arrhythmias can be generated by tracheal intubation due to a reflex sympathetic activity. HR was also found to increase following the administration of NMB reversal as compared to that before reversal.[10]

The reason for increase in the values of the hemodynamic parameters during reversal may be as a result of pain, return of awareness and decreased depth of anesthesia as we approached the end of anesthesia.

A correlation between PI and the other non-invasive hemodynamic parameters were sought in our study. Significant negative correlation of PI with HR was seen at all the three intervals after extubation, that is, the first, third, and fifth minutes. With SBP, significant negative correlation was seen at the first minute post-extubation only. DBP did not show significant correlation with PI at any interval while a significant negative correlation with MAP was seen at the first and the fifth minute post-extubation.


PI is a dynamic monitor like the ECG but there was no option to set the trend for PI in any of the standard multi-para monitors so readings could not be viewed later. Each of the events required readings to be noted vigilantly. There were incidences when the NIBP cycling took longer than usual so real time recording may have been missed in such incidences. It is impossible to keep the duration of laryngoscopy similar in all cases. Even though it was done by the same individual, the duration of laryngoscopy can influence the hemodynamic parameters.[15]

  Conclusion Top

From what has been observed in our study PI changed significantly during the first minute post-intubation, at the start and end of NMB reversal, pre-extubation, and post-extubation. Hemodynamic response was maximum during NMB reversal. PI correlated negatively with the other non-invasive hemodynamic parameters. Negative correlation indicated that the two variables (PI and the other hemodynamic parameters) are moving in opposite directions on a linear graph. So, while PI decreased in response to noxious stimuli, HR, SBP, DBP, and MAP increased. As PI did not correlate uniformly to any of the non-invasive hemodynamic parameters, its use as an alternative to the other non-invasive hemodynamic parameters for peri-operative monitoring needs further investigation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.


Clinical trial number: CTRI/2016/12/007619.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Perfusion Index: Clinical applications of Perfusion Index. Available from: [Last accessed on 2016 Dec 13].  Back to cited text no. 1
Atef HM, Fattah SA, Gaffer MEA, Al Rahman AA. Perfusion Index versus non-invasive hemodynamic parameters during insertion of i-gel, classic laryngeal mask airway and endotracheal tube. Indian J Anaesth 2013;57:156-62.  Back to cited text no. 2
[PUBMED]  [Full text]  
Hagar H, Church S, Mandadi G, Pulley D, Kurz A. The perfusion index measured by a pulse oximeter indicates painful stimuli in anaesthetised volunteers. Anaesthesiology 2004;101:A514.  Back to cited text no. 3
Mowafi HA, Ismail SA, Shafi MA, Al-Ghamdi AA. The efficacy of perfusion index as an indicator for intravascular injection of epinephrine containing epidural test dose in propofol anaesthetised adults. Anesth Analg 2009;108:549-53.  Back to cited text no. 4
Cannesson M, Dessebe O, Rosamel P, Dellannoy B, Robin J, Bastien O, Lehot JJ. Pleth variability to monitor waveform aplitude and predict fluid responsiveness in the operating theatre. Br J Anaesth 2008;101:200-6.  Back to cited text no. 5
Kowalzcyk M, Fijalkowska A, Nestorowicz A. A new generation pulse oximetry for the assessment of peripheral perfusion during general anaesthesia – A comparison between propofol and desflurane. Anaesthesiol Intensive Ther 2013;45:138-44.  Back to cited text no. 6
Edwards ND, Alford AM, Dobson PMS, Peacock JE, Reilly CS. Myocardial ischaemia during tracheal intubation and extubation. Br J Anaesth 1994;73:537-9.  Back to cited text no. 7
Barak M, Ziser A, Greenberg A, Lischinsky S, Rosenberg B. Hemodynamic and catecholamine response to tracheal intubation: Direct laryngoscopy compared with fibreoptic intubation. J Clin Anesth 2003;15:132-6.  Back to cited text no. 8
Paulissen R, Salem MR, Joseph NJ, Braverman B, Cohen HC, Crystal GJ, et al. Hemodynamic responses to endotracheal extubation after coronary artery bypass grafting. Anesth Analg 1991;73:10-5.  Back to cited text no. 9
Kochaki S, Behaeen K, Mahmodi K, Fatahi M, Rahmani H. The study of hemodynamic changes of patients under general anaesthesia with different rates of injection of reverse. WJPPS 2015;4:255-65.  Back to cited text no. 10
Kakazu CZ, Chan BJ, Kwan WF. Masimo set technology using perfusion index is a sensitive indicator for epidural onset. Anaesthesiology 2005;103:A576.  Back to cited text no. 11
Yamazaki H, Nishiyama J, Suzuki T. Use of perfusion index from pulse oximetry to determine efficacy of stellate ganglion block. Local and Regional Anaesthesia 2012;5:9-14.  Back to cited text no. 12
Hager H, Reddy D, Kurz A. Perfusion index – A valuable tool to assess changes in peripheral perfusion caused by sevoflurane? Anaesthesiology 2003;A-593.  Back to cited text no. 13
Reid LC, Brace DE. Irritation of respiratory tract and its reflex effect on heart rate. Surg Gynaec Obstet 1940;70:157-62.  Back to cited text no. 14
Montazari K, Naghibi KH, Hashemi SJ. Comparison of haemodynamic changes after insertion of laryngeal mask airway, facemask and endotracheal intubation. Acta Medica Irana 2004;42:437-40.  Back to cited text no. 15


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