Comparison of iNIBP, linear inflation non-invasive bloodpressure measurement, and conventional deflation NIBPin detecting hypotension during Caesarean section

Seirei Hamamatsu General Hospital, Department of Anesthesiology,

Shingo Irikoma

Introduction
The first choice for anaesthesia in Caesarean section (C-section) is
combined spinal-epidural anesthesia (CSEA). Management ofmaternal hypotension is important to maintain the physicalwell-being of the baby in C-section under CSEA during delivery.
Management of maternal hypotension consists of prevention,detection and treatment. Since it is impossible to prevent maternal
hypotension in all cases, prompt appropriate treatment is required.
Therefore, it is important to detect hypotension as soon as possible.
We prospectively evaluated if Nihon Kohden’ s linear inflation
non-invasive blood pressure measurement technology (iNIBP) can
detect maternal hypotension during anesthesia more quickly thanconventional deflation non-invasive blood pressure measurement
technology (dNIBP).

Transfusion

Maternal
hypotension
Pressurerisingleft uterine
displacement

Three key approaches to deal
with maternal hypotension.

Materials and Methods
Female patients with single pregnancy who were scheduled for C-section under CSEA from August toDecember 2015 were included in this evaluation. We obtained institutional review board (IRB) approval andwritten informed consent from all patients before enrollment. An iNIBP cuff was placed on the same arm as an
intravenous line, and a dNIBP cuff was placed on the other arm. iNIBP and dNIBP were simultaneouslymeasured at 2 minute intervals. Anesthesia was induced and maintained with combined spinal-epidural
anesthesia (CSEA) through a single puncture. To prevent hypotension, preloading with intravenous fluid andleft uterine displacement (about 10 degrees) were performed soon after anesthesia induction. We defined
hypotension as systolic arterial pressure of 107 mmHg or less on the left arm which is about 10 cm lower, andpressure of 92 mmHg or less on the right arm which is about 10 cm higher. Measurement time was the timefrom induction of anaesthesia to delivery of the baby. A two-tailed z test was performed to statistically analyze
the difference between iNIBP and dNIBP measurement results.

Results
Out of 100 cases, 76 patients were diagnosed with hypotension (76.0%). Of these, iNIBP detected hypotension
sooner than dNIBP in 47 cases (61.8%) (p=0.03). The average time for iNIBP to detect hypotension afterinduction of anesthesia was 379 seconds, an average of 45 seconds sooner than dNIBP (424 seconds).

Conclusion
iNIBP detected hypotension more quickly than conventional deflation NIBP without compromising themeasurement reliability, even in the clinical setting of C-section under CSEA where there are various artifacts
that may interfere with the measurement of blood pressure.

Comparison of iNIBP, linear inflation non-invasive blood pressure measurement,
and conventional deflation NIBP in detecting hypotension during Caesarean section

iNIBP is Nihon Kohden’ s non-invasive blood pressure measurement
algorithm using linear inflation technology. iNIBP completes themeasurement while inflating a cuff. It has been shown that the iNIBP
measurement time is shorter and target inflation pressure is lower ascompared to the conventional method 1), 2).
The conventional step-deflation method sets the target inflation pressure based on the previous systolicblood pressure. Therefore, when the patient’ s blood pressure increases compared to previous measurements,
the target inflation pressure may be set to a level which is insufficient for the measurement. In these cases,
another inflation-deflation cycle is required, and may be repeated, increasing both the measurement timeand potential for patient discomfort (Figure 1). When the patient’s blood pressure has dropped since theprevious measurement, the target inflation pressure is set significantly above the previous systolic bloodpressure, which again leads to longer measurement time and excessive pressure applied to the patient(Figure 2). On the contrary, the iNIBP algorithm effects a slow inflation of a cuff while simultaneously
detecting oscillations, then deflates the cuff as soon as systolic blood pressure is determined. It has beenreported that iNIBP can be useful even in situations where patient’s hemodynamics is greatly varying 3).

Cuﬀ 300
pressure（mmHg）
250

iNIBP

240mmHgiNIBP

Measurement
completes assoon as SYS
is determined

200 Lower pressure
150

150
SYS

Deﬂationmeasurement
completes

502030iNIBP

Deﬂation method250mmHg
Pressure still too low

210mmHg

SYS

Pressure too low

iNIBP

140mmHg

Measurement
completes assoon as SYS
is determined

10050

Shorter measurement
time
10Cuﬀ 300
pressure（mmHg）
250
200130mmHg

1000Deﬂation method

405060Time (sec)0

Shorter measurementtime10203040

References1) Onodera J, Kotake Y et al. Validation of inflationary non-invasive blood pressure monitoring in adult surgical patients.
J Anesth, 2011;25:127-1302) Sasaki J, Hori S et al. Validation of inflationary non-invasive blood pressure monitoring in emergency room patients.
Blood Press Monit. 2015 Aug 33) Hirata N. Usefulness of linear inflation non-invasive blood pressure measurement (iNIBP) in anesthesia induction.
Academic and Technical Information. Nihon Kohden Corporation. 2016; No. SP66-0011

8810 SP66-0017 ’16.8. CLB. A.

Deﬂationmeasurement
completes5060
Time (sec)