Prediction of hypotension using perfusion index following spinal anesthesia in lower segment caesarean section

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NJOG / VOL 15 / NO.2 / Issue 31 / Jul - Dec, 2020
Original Article
Nep J Obstet Gynecol. 2020;15(31):67-72
CORRESPONDENCE
Dr Akshay Prasad Pradhan
Department of Anesthesiology, Paropakar Maternity and
Women's Hospital, apathali, Kathmandu
Email: akspra699@gmail.com; Mobile: +977-9841618413
Prediction of hypotension using perfusion index following spinal
anesthesia in lower segment caesarean section
Akshay Prasad Pradhan, Achyut Sharma, Amir Babu Shrestha, Tara Gurung, Sangeeta Shrestha, Ujjwal
Basnet, Jay Prakash Thakur, Mukesh Kumar
Received: August 3, 2020 Accepted: October 16, 2020
ABSTRACT
Aims: To correlate the relation between perfusion index and the prediction of hypotension in lower segment caesarean section.
Methods: This is a prospective observational study of parturients undergoing caesarean section from 4th February to 2nd June 2020
at Paropakar Maternity and Women's Hospital in Kathmandu. Cases were studied by their Perfusion Index (PI) value of 3.5 as cut-off.
parturients undergoing caesarean section. Hemodynamic effects and PI values were monitored recorded and compared between low and
high PI groups. Statistical analysis was done using independent sample T test and Pearson correlation.
Results: Total 106 cases were studied with 52 with low PI value and 54 cases with high PI value. The incidence of hypotension in low PI
was 26% whereas it was 48% in high PI group and mean consumption of phenylephrine was more in high PI group.
Conclusions: Parturients with a higher baseline PI index of more than 3.5 have more incidence of hypotension and require vasopressors
support following spinal anesthesia in elective LSCS
Keywords: Caesarean section; Hypotension; Perfusion index; Spinal anesthesia; Vasopressors;
Citation: Pradhan AP, Sharma A, Shrestha AB, Gurung T, Shrestha S, Basnet U, et al. Prediction of hypotension using perfusion index
following spinal anesthesia in lower segment caesarean section. Nep J Obstet Gynecol. 2020;15(31):67–72. DOI: https://doi.
org/10.3126/njog.v15i2.32909
INTRODUCTION
Providing safe yet adequate anesthesia in obstetric
patients is very challenging for every anesthesiologist.
The physiological changes associated with pregnancy
make every pregnant woman vulnerable for various
intra-operative upheavals that often complicate and
threaten the lives of the mother and the fetus.1 For
caesarean sections (CS), subarachnoid block (SAB)
is the most commonly performed anesthesia for
various reasons pertaining to maintaining the safety
of the mother and fetus.
Perfusion index is defined as the ratio of pulsatile
blood flow to non-pulsatile blood flow in the
peripheral tissues and it is measured using a relatively
cheap, and non-invasive pulse oximeter.2
The use of perfusion index (PI) as a dynamic measure
of vascular responsiveness and its use in prediction
of hypotension will certainly create a new approach
to patient safety. There are, however, very scarce
articles on the use of this innovative strategy for
patient management and most of which have shown
promising results3-5 but some studies6 have produced
equivocal results to the use of this technique. It is
very difficult in a country like ours from financial,
technical, and ethical point to use invasive and/or
costly non-invasive monitoring techniques to guide
fluid/vasopressors in cases of expectant hypotension.
Thus, study using perfusion index which require
only meager resources will certainly help in a
cost-effective management of patient at times of
hypotension. There are also very limited to no such
studies being conducted in this part of the world also
provides us enough impetus to conduct such study in
our center.
METHODS
An observational analytical study was performed
from 4th February to 2nd June 2020 at Operation
Theater of Paropakar Maternity and Women’s
Hospital in Kathmandu which is the tertiary level
public hospital with more than 6000 cesarean section

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Prediction of hypotension using perfusion index SAB in LSCS
NJOG / VOL 15 / NO.2 / Issue 31 / Jul - Dec, 2020
annually. Parturient women were classified by
perfusion index (PI) cut-off of 3.5 as low (<3.5) and
high PI (≥3.5) group for the purpose of comparison.
IRC approval was taken and a written informed
consent was obtained. The inclusion criteria were
ASA II physical status, planned for elective LSCS,
gestational age >36 weeks and <41 weeks, and age
20 years to 35 years. Cases excluded were patients
with contraindications to spinal anesthesia, BMI >40,
preeclampsia, placenta praevia, and comorbidities
like cerebrovascular or cardiovascular disease, and
gestational diabetes. For all planned surgery patients
were instructed to remain fasted for 8 hours for solid
food, 6 hours for liquid and 2 hours for clear liquid.
No oral premedication was given.
On receiving the subject in the holding area, baseline
hemodynamic parameters (including SBP, DBP,
MAP, and PI) were recorded and PI was measured
again at supine position. With Lifescope™ monitor
by an anesthesiologist who was not involved in any
other part of the study. Patients were kept in supine
position and baseline PI was recorded. According to
baseline PI subjects were divided into two groups,
Group I had a PI index of <3.5 and Group patients
had a PI index of ≥3.5. Following pre-hydration, next
set of baseline vitals were recorded and premedicated
with intravenous Metoclopramide 10 mg and
Ranitidine 50 mg.
The parturient was then subjected to routine neuraxial
blockade using standard technique in standard
set up based on hospital’s protocol. During the
administration of neuraxial anesthesia, the pulse
oximeter was disconnected to prevent observer
bias and SpO2 was recorded using portable pulse
oximeter. Spinal anesthesia was performed by an
anesthesiologist who was blinded to the baseline PI
values, using 25G Whitacre spinal needle (PENCAN)
in left lateral decubitus position with 11 mg of 0.5%
hyperbaric Bupivacaine (Anawin heavy 0.5%, Neon
Laboratories, India) total volume of 2.2 ml at either
L3-L4 or L4-L5 inter-space. The parturient was
then shifted back to supine with left lateral uterine
displacement of 150 by tilting of the bed or manual
displacement. The (Lifescope™) pulse oximeter
was reconnected to monitor the patient until the end
of surgery. Throughout the surgical procedure, the
parturient was provided with oxygen supplementation
via nasal cannula at 2l/min.
During the surgery, Ringer’s lactate was given at
600 ml/hr. The level of sensory block at 5 minutes
was checked using cold ice pack and recorded in
the proforma. Failure to achieve a level of T6 at 5
minutes following spinal resulted in exclusion of
the parturient from the study and case was managed
accordingly to the standard institutional protocol.
Maximum cephalad spread of local anesthetic was
recorded at 20 minutes following SAB. Vitals such
as NIBP, HR, RR, SpO2 and PI were recorded
continuously at 2 minutes interval for the first
20 minutes, then at 5 minutes interval until the
end of surgery by the same anesthesiologist who
administered the spinal anesthesia.
Hypotension was defined as fall in MAP <65 mm Hg
and treated with IV bolus of Inj. Phenylephrine 100
mcg along with 100 ml of Ringer’s lactate. The first 60
minutes following administration of spinal anesthesia
was considered for spinal induced hypotension.
Bradycardia was defined as HR <50 beats/min and
treated with Inj. Atropine 0.6 mg IV bolus.
Following extraction of the baby, Apgar score was
recorded at 1st and 5th minutes. Following the delivery
of the baby, Inj. Oxytocin 3 U was given as bolus and
other 10 U will be given at 200mU/min as a separate
infusion if required as per the surgeon. Parturient
requiring additional oxytocics and/or additional
interventions were excluded from the study.
The incidence of other side effects including nausea
and vomiting were recorded and was managed
by supportive management and giving injection
Ondansetron 0.1 mg/kg IV. Repeated episodes of
vomiting within 5 minutes were recorded as one.
Calculated sample size by 30% expected change (as
obtained from a pilot study) obtained at least 44 in
each study group. Data were entered in SPSS version
23 for statistical analysis.
RESULTS
A total of 106 patients were included in the study out
of which 2 were excluded due to inadequate level of
spinal blockade, 3 were excluded due to increased
requirement of oxytocics and 1 was excluded due
to conversion to GA. there were 52 cases in low PI
group and 54 in high PI group. The demographic
parameters such as age weight and height were
comparable between the two groups.

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NJOG / VOL 15 / NO.2 / Issue 31 / Jul - Dec, 2020
Table-1: Demographic parameters of grouped by
perfusion index (N=106)
Demographic
parameters
Low PI
(n=52)
High PI
(n=54)
p- value
Age in years 27.24 27.66 0.75
Weight in kg 68.26 66.84 0.46
Height in inches 63.02 62.10 0.10
The median level of cephalad spread of sensory
block was T6 in both the groups. The mean baseline
PI value of low PI group was 1.73 ±.72 and that of
high PI group was 5.37±1.79 which is expected as
the parturients were divided according to values of
more than 3.5 or less than 3.5 based on the study of
Toyama et al, PI values for the rest of the study were
statistically insignificant. Intraoperatively the mean
HR of both the groups was stable and uneventful;
none of the patients had any episode of bradycardia
and did not receive atropine or any other rescue
drugs. The mean HR between the two groups was
statistically insignificant.
The mean baseline blood pressure between the two
groups was statistically insignificant with a mean SBP
of 123.44±14.07 in low and 121.6 ±15.08 in high PI
group. There was statistically significant difference
from 4th to 10th minutes (p<0.05) [Figure-1].
Figure-1: Systolic blood pressure low PI (yellow) and
high PI (red) groups
The baseline mean DBP between the two groups
were comparable with mean DBP for both groups
(81.6±11.30 and 77.92 ±11.45) but there was
statistically significant difference in 4th and 6th minute
[Figure-2].
Figure-2: Diastolic blood pressure in low PI (yellow)
and high PI (red) groups
From the above result we can assume that the systolic
blood pressure is affected more than the diastolic
pressure during spinal anesthesia in parturients and
adding to that, the group of parturient with a low PI
index has less decrease in both systolic and diastolic
pressure as compared to parturients with a high PI
index.
The baseline mean arterial pressure between the
two groups were comparable with mean MAP
(92.3±11.38 and 87.32±20.29) (p=0.13) except in 6th
minute. Hence from this we can assume that the mean
arterial pressure is not well affected as compared to
systolic and diastolic pressure.
Figure-3: Mean arterial blood pressure in low PI
(yellow) and high PI (red) groups
The incidence of hypotension between the two
group were statistically significant as 26% (14 in
52) patients of low PI had incidence of hypotension
requiring vasopressors support whereas there was a
large percentage (48%; 26 in 54) of patients with high
PI required it. The mean phenylephrine consumption
was also significantly higher (p=0.03) in high PI

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NJOG / VOL 15 / NO.2 / Issue 31 / Jul - Dec, 2020
group (122.41±57.61 vs 94.64 ±9.03).
The Respiratory rate and SpO2 were comparable
between the two groups throughout the whole study
period, There were no significant APGAR score
differences between the groups in the 1stand the 5th
minute; and the incidence of nausea and vomiting
were similar in both the groups.
On spearmans rank correlation we found a highly
significant co relation between baseline PI of >3.5
and number of episodes of hypotension (rs = 0.26 and
p<0.05) [Figure-4].
Figure-4: Spearman rank correlation between baseline
PI and hypotension
DISCUSSION
The present study was done to determine whether
patients with higher baseline PI value were more
susceptible to hypotension after spinal anesthesia.
The results conclude that parturients with higher PI of
>3.5 had higher number of episodes of hypotension.
Hypotension is one of the most common side effects
of spinal anesthesia and there are definite indicators
which predict the likelihood of hypotension. Studies
have tried to evaluate the usefulness of perfusion
index as a predictor for hypotension following spinal
anesthesia in parturients because there are no non
invasive methods which can predict the likelihood of
hypotension.
The principle7 of SpO2 is based on two light sources
with different wavelength, 660 nm and 940 nm
emitted through the cutaneous vascular bed of
finger or ear lobes based on Beer- lamberts law. The
absorbance of both the wavelength has a pulsatile
component, which is then presented as fluctuations
in volume in the arteries between the source and the
receptor or detector. The non-pulsatile component is
from the bones and tissues, the perfusion index (PI)
is the ratio between the pulsatile and non-pulsatile
component.8
In a normal pregnancy, there is a decrease in systemic
vascular resistance and increase in blood volume and
cardiac output, due to various factors. The decrease in
systemic vascular resistance in different parturients is
varied due to various factors. As there is an increase in
flow due to decrease systemic vascular resistance this
will lead to a pulsatile component in the arteries and
hence leading to a higher PI index in the vasodilated
state. Induction of sympathetectomy by methods such
as spinal anesthesia leads peripheral pooling of blood
and hypotension.
Parturients with higher PI index are expected to
have a decreased peripheral vascular tone and are
at higher risk of developing hypotension, following
sympathetectomy, PI index has been used by Mowafi
et al9 to detect intravascular injection of epinephrine
containing test dose during epidural anesthesia,
Ginosar et al10 demonstrated sympathetectomy by an
increase in PI following epidural anesthesia. From the
mentioned studies we can assume that that PI index
can be used as a reliable indicator of vascular tone.
The baseline cutoff value for PI of 3.5 was based on a
study conducted by Toyama et al4 who did regression
analysis and ROC analysis and identified 3.5 to be a
cut off value which was based on the fact that decrease
in vascular resistance is related to the number of
gravidity and parity. As the study conducted by
Toyama et al4 where he conducted study to identify
3.5 as the cut off value in Japanese population, we did
not try to explore and correlate to refute or challenge
this baseline PI in our Nepalese population.
On Spearman rank correlation, there was low

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correlation found between the incidence of
hypotension, total dose of phenylephrine used and the
total IV fluid consumed in parturients with baseline
PI value of >3.5.
The correlation of incidence of hypotension and
PI index was found to be highly significant with
26 patients out of 54 patients had hypotension
whereas only 14 patients out of 52 patients had
hypotension, the correlation between the total dose of
phenylephrine and PI was not significant (p=0.078).
The correlation of PI index and total fluid consumption
was not significant p=0.74), hence we did not find
a significant correlation between incidence of
hypotension and total dose and phenylephrine and
total fluid consumption and PI index.
Toyama et al4 found a sensitivity and specificity of
81% and 86% respectively for baseline PI with a cut
off of 3.5 to predict hypotension, our study showed
a sensitivity of 58% and specificity of 24%. The
differences may be due to differences in methodology,
as in the other study the definition of hypotension
decrease in SBP of more than 25% of baseline, co
loading used in the other study if of colloid whereas
we used crystalloid in our study, other factors may
also play a role such as patient movement, anxiety,
operating room temperature. In our study we set the
operating room temperature at 25 degrees centigrade
and also asked the patient to be calm, but these are
the only measures we could do to comfort and allay
anxiety in a parturient who could not be given any
form of medication before the delivery of the fetus.
Uterotonics such as prostraglandins F2 alpha and,
methylergometrine would have influenced the
vascular tone and parturients receiving these drugs
were excluded from the study as they received these
drugs 20 and 25 mins after spinal anesthesia.
There are many limitations to our study such as
anything that increases the sympathetic activity of
the patient such as anxiety can easily influence the PI
value, other factors such as movement of the hand. In
our study we took various precautions to record the
baseline PI index value, all patients were counseled
before the surgery to allay anxiety, all the baseline
record were done in supine position on the same hand
of every patients, all of the reading were done in left
lateral position to decrease the effects of aorto-caval
compression.
Our study has various limitations as we did not use
parameters such as stroke volume, calculation of
total peripheral resistance, and as it were cases of
elective caesarean sections, we did not use invasive
procedures such as invasive arterial pressure
monitoring or central venous pressure. Secondly the
pulse oximeter is subjected to changes due to anxiety,
patient movement and discomfort or any other stimuli
that will result in increase in sympathetic activity.
Secondly due to financial constraints and institutional
protocol we could not use colloid for preloading or co
loading the patient as studies have shown preloading
or co loading with colloid had various benefits over
crystalloid.
CONCLUSIONS
Prediction of post spinal hypotension in caesarean
section is an interesting prospect as it allows better
care for the parturient, PI index is a simple safe
and very easy method to predict hypotension intra
operatively. PI with values of <3.5 have less incidence
of hypotension and values of ≥3.5 have more
incidence of hypotension but it cannot be used alone
as a tool due to its low sensitivity and specificity.
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