Introduction
In cardiac surgery,anesthesia induction causes significant haemodynamic changes. However,
haemodynamic management routinely uses blood pressure and cardiac output targets,
and this is supported by blood analyses but for this rarely employs microvascular
monitoring [1]. However, macrohaemodynamics management following cardiac surgery is
limited in predicting the microcirculation [2]. The microcirculation can be assessed
by the use of vascular occlusion testing (VOT)[3] .NIRS is an easily applicable, non-invasive
method for assessing tissue oxygenation and microvascular reactivity [4].The aim of
the our study was to evaluate the effects of anaesthesia induction on microvascular
reactivity using VOT.
Methods
Prior to induction of anaesthesia, we performed the first VOT with NIRS.Thereafter,
all patients received a standardised anaesthesia induction with fentanyl (5 mcg/kg),
rocuronium (1 mg/kg), midazolam (0,1 mg/kg).Then,tracheal intubation, positive pressure
ventilation was started to maintain end-tidal CO2 tension of 30-35 mmHg.Maintenance
of anesthesia was performed using intermittent midazolam, fentanyl, and rocuronium.The
second VOT was performed 20 min after induction of anaesthesia (before skin incision).
Comparisons of data before and after induction were made by using the paired samples
t test.
Results
VOT variables before and after induction of anaesthesia are shown in Table . Baseline
StO2 was higher after induction of anaesthesia (78,8 vs. 85,1%, P = 0.03). Oxygen
consumption was significantly lower after induction, as indicated by the higher minimum
StO2 (54,8 vs.66,6 % p=0,001) and the slower occlusion slope (0,22 vs.0,16 p=0,001).
After induction of anaesthesia, reperfusion time was significantly longer (22,4 vs.28,7)
and reperfusion slope was significantly slower (1,82 vs.1,27 p=0,001).
Discussion
In our study of pediatric cardiac surgery patients, significant microcirculatory alterations
were observed after induction of anaesthesia.The clinical evaluation of microcirculatory
reactivity seems to be of great interest, but currently its assessmentis considered
technically challenging. Among a variety of non-invasive techniques,NIRS coupled with
VOT has been proposed to be an easy-to-perform and reliable tool to assess microvascular
reactivity[4]. The occlusion slope reflects oxygen consumption in the tissue; thus,
a slower occlusion rate indicates lower metabolic rate, impaired regional perfusion
distribution or impairment in oxygen utilisation by mitochondria. After reperfusion,
previously closed capillaries favourably open and blood flow in previously patent
capillaries increases, causing a hyperaemic response. Thus, a slower reperfusion slope
and a diminished degree of flow reperfusion indicate impaired microvascular reactivity[5].
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© 2021 Published by Elsevier Inc.
