Objectives: To verify oxygen metabolic changes and to assess the corellation between oxygen consumption (VO2), oxygen delivery (DO2) and oxygen extraction (ERO2). Subjects and methods: 67 patients with pulmonary hypertension related left heart diseases who underwent elective (MVR) and/or aortic valve replacement (AVR) enrolled in the study. Calculated parameters by pulmonary artery catheter inserted at operation theater and monitor system.
Trang 1MITRAL VALVE REPLACEMENT OR MITRAL VALVE REPLACEMENT AND CONCOMITANT AORTIC VALVE REPLACEMENT IN PATIENTS
WITH PULMONARY HYPERTENSION
Kieu Van Khuong*; Pham Thi Hong Thi**; Nguyen Quoc Kinh*** SUMMARY
Objectives: To verify oxygen metabolic changes and to assess the corellation between oxygen consumption (VO 2 ), oxygen delivery (DO 2 ) and oxygen extraction (ERO 2 ) Subjects and methods: 67 patients with pulmonary hypertension related left heart diseases who underwent elective (MVR) and/or aortic valve replacement (AVR) enrolled in the study Calculated parameters by pulmonary artery catheter inserted at operation theater and monitor system Results and conclusion: Cardiac output index (CI), ERO 2 and VO 2 increased significantly intra and after operation with respect to baseline levels DO2 decreased after intubation and cardiopulmonary bypass stop but increased significantly at intensive care unit admission The close corellation between VO 2 and DO 2 , ERO 2 was at all postoperative points of time
* Keywords: Mitral valve replacement; Pulmonary hypertension; Oxygen delivery; Oxygen metabolism; Aortic valve replacement
INTRODUCTION
The important problems of postoperative
cardiac care are those of cardiac output,
tissue oxygenation, the ratio of myocardial
oxygen supply and demand Ideally, one
should strive to obtain a cardiac index
mixed venous oxygen saturation while
optimizing the oxygen supply/demand ratio
Oxygen delivery (DO2) is considered
as principal target for adequate tissue
perfusion [1]
When oxygen exceed a threshold value
whereby sufficient DO2 can not be
assured by increasing cardiac output (CO)
or hematocrit levels, a shift from erobic to
anerobic metabolism occurs From this point, the resulting oxygen debt leads
to increased arterial lactate production This physiological dependence of oxygen
avoided, as hyperlactatemia is associated with increased postoperative mortality, morbidity and hospital length of stay Previous studies have shown that a
during cardiopulmonary bypass (CPB) is independently associated with acute kidney injury [2]
The postoperative course after heart valve surgery with CPB is characterized
by a progressive increase in cellular oxygen demand This increase, known as
* 103 Military Hospital
** Vietnam Natinoal Heart Institute
*** Vietduc Hospital
Corresponding author: Kieu Van Khuong (icudoctor103 @ gmail.com)
Date received: 10/01/2018
Date accepted: 06/03/2018
Trang 2hypermetabolic status, persists for several
hours [3, 4] or, in some experiences, for a
few days [5] after surgery Previous reports
have suggested that CPB could be the main
cause of the increased metabolism after
cardiac surgery and of the perioperative
changes between VO2 and DO2 [5, 6]
The aim of this study was to: Evaluate
oxygen metabolism changes after isolated
mitral valve replacement or mitral valve
replacement and concomitant aortic valve
replacement
1 Subjects
This study was carried out at Heart
Center of Hue Center Hospital from May
to November 2017 We enrolled 67 patients
with pulmonary hypertension associated
with left heart diseases who underwent
isolated MVR or MVR and concomitant
AVR The study protocol was approved by
Ethics Committee of Hospital and a written
consent was obtained for each patient
Patients were excluded if they had any
evidence of sepsis (temperature > 37.50C,
WBC > 12 G/L), a history of
hyper-or-hypothyroidism or claustrophobia or facial
deformities (canopy kit intolerence or ill-fit)
2 Methods
* Preoperative assessment:
A 4-lumen pulmonary artery catheter
(PAC) (7.5F size) with a thermistor probe
(B.Braund) was inserted via the right internal
jugular vein
* Anesthesia:
General anesthesia was induced with
fentanyl, 3 - 5 µg/kg and mydazolam
0.2 mg/kg The therapy for PAH was
instituted with a nitroglycerin infusion (0.5 - 1 µg/kg/min), deliberate hypocarbia (arterial carbon dioxide tension < 35 mmHg), fractional inspired oxygen concentration (FiO2) of 1.0, and elective ventilation for at least 12h in the postoperative period Rocuronium and vecuronium were used
as muscle relaxants
* Technique of MVR:
All patients were operated on CPB under moderate hypothermia (28 - 300C) using standard techniques Mitral valve was approached either through the left atrium or via the interatrial septum (trans-septal approach) Whenever possible, total chordal preservation was carried out The valve used was ATS or St.Jude Mediacal bileaflet mechanical prosthesis
* Measurements and formulas:
Measurements were obtained at the following time points:
- T0: baseline, pre-induction; T1: post-intubation; T2: immediate post-CPB; T3:
at ICU admission; T4: first 6 hours at ICU and Toff (T14): before PAC removing and the hemodynamics had been stabilized
- Mixed venous samples were taken via the distal port of the PAC Calculate DO2 = CO x CaO2 (1) while CaO2 = Hb x 1.34 x SaO2 + (0,003 x PaO2) VO2= CO x (CaO2 - CvO2) ERO2 = (CaO2 - CvO2)/CaO2 [7]
- Cardiac output (CO) was measured
by the thermodilution technique using
10 mL of 0.9% ice-cold saline and a hemodynamic monitor (Phillip MP70) having inbuilt capacity to measure CO
Trang 3Three consecutive successful determinations
were averaged and the difference between
any two readings did not exceed 15%
Mean value of systolic pulmonary artery
pressure, pulmonary capillary wedge
pressure (PAOP), pulmonary vascular
resistance (PVR) and cardiac index (CI)
were calculated Baseline (control)
hemodynamics, total complete blood
count and arterial blood gas (ABG)
induction of anesthesia
* Statistical analysis:
All values are mentioned as mean ± standard deviation (SD) and range Unpaired student’s t-test and Chi-square test were used for comparison of data of the two groups, where applicable For statistical analysis, the statistical software SPSS version 19.0 for windows (SPSS Inc., Chicago, IL) was used p value < 0.05 was considered statistically significant
RESULTS
1 Patients, demographic and intra-operative characteristics
Table 1: Patient characteristics
(Abbreviation: ACC: Aortic cross-clamp time; CPB: Cardiopulmonary bypass time)
Among 67 patients, 45 patients underwent isolated mitral valve replacement and 22 patients underwent MVR and concomitant AVR The study group was mainly female (77.6%), mean age 45.51 ± 10.74 years All patients were pulmonary hypertension related left heart diseases (PAPs ≥ 35 mmHg measured by echo)
Trang 42 Oxygen metabolism and hemodynamic changes
Table 2: Changes in oxygen consumption and delivery
(ap < 0.0001 vs baseline; bp < 0.05 vs baseline)
There was a progressive increase in CI, ERO2 and VO2 after operation with respect
to baseline levels, but significantly decrease in SvO2 No significant differences in DO2 level at T4 and Toff time point CI, SvO2, DO2, ERO2, VO2 was in mean value
2 Correlation between oxygen consumption and oxygen delivery, oxygen extraction
in MVR at diffirent time points
Table 3: Relation between oxygen consumption and oxygen delivery, oxygen extraction
in MVR at diffirent time points
(Spearman’s correlation)
(Spearman’s correlation) Time points
No significant relation between VO2 and DO2 could be demonstrated before anesthesia induction (T0 time point) Since that time point a constantly significant linear relation between VO2 and DO2 was demonstrated up to remove PAC postoperatively There was a negative correlation between VO2 and ERO2 at base time point
Time
2
Trang 5Some intraoperative and postoperative
results showed in table 1 The mean CPB
(114.18 ± 57.71 mins)and the mean aortic
cross-clamp time (79.76 ± 36.78 mins) was
similar to Xiaochun Song’s study outcome
(CPB 119.9 ± 37.4 mins and ACC: 82.5 ±
31.8 mins) [8] This result was higher than
that Abu El-Hussein’s (CPB 55 mins; ACC
is the patient group of that study was
replaced one valve surgery only
Our results showed a significant decrease
in DO2 and VO2 during operation in
comparison of baseline data (table 2) We
consider that it may be due to the effect of
sedation following premedication and
anesthesia drugs Besides, we can see
the early increase in VO2 and DO2 at ICU
admission (T3 time point), which was
mostly attributed to rewarming (early phase)
and the neurohumeral catabolic response
to major surgery These findings are
similar to those in the reports of oxygen
metabolism changes in patients with
rheumatic mitral valve disease at different
intervals after MVR In the study by P.S
Myles [5], the mean DO2 as well as VO2
decreased significantly at post-induction
(DO2: from 954 to 681 mL/mins, VO2: from
202 to 139 mL/mins) and after CPB (DO2:
709 mL/mins, VO2: 199 mL/mins) in patients
undergoing coronary artery bypass and
valvular surgery Another study conducted
by Parolary et al [10] showed effects of
time on the changes in DO2 were significant
There was a significant postoperative DO2
decrease in both groups, starting after
anesthesia induction and lasting up to
time affected the changes of VO2 significantly: after surgery, starting from
“skin” time point, VO2 significantly increased in both groups with respect to baseline levels ERO2 behavior was similar to VO2, both of which increased dramatically Only time indicated a remarkable effect and there was a significant ERO2 increase over time in both groups ERO2 value in the study did not change at T1, T2 and T3 time point but increased significantly at T4 and T14
time point (table 2) In our opinion, it may
be due to inadequate cardiac output and increased oxygen extraction in an attempt
to meet oxygen needs Such an increase
in oxygen extraction frequently is associated with a prolonged postoperative recovery period
The relation between VO2 and DO2, this study revealed that in the intraoperative and early postoperative period of cardiac surgery, oxygen metabolism was substantially different from normal conditions, where a biphasic relation can be demonstrated [11] There was a significant relationship between DO2 and VO2 during postoperative period During physical activities or experiments, the increase in oxygen demand is met by an increase in both cardiac output and oxygen extraction ratio This case was not our patient after cardiopulmonary bypass As usual, SvO2 and thus oxygen extraction remained relatively stable during operation and up
to ICU admission, whereas the increase
in VO2 was primarily matched by an increase in cardiac output and DO2 Hence, there was a remarkably close
Trang 6relationship between VO2 and DO2 Similarly,
the recent study by Christina Routsi [11]
identified relationship between VO2 and
DO2 in 36 patients (159 measurements):
VO2 = 28 + 0.27 x DO2, r = 0.79, p < 0.0001,
which was similar to our results at
postoperative various time points (table 3)
There was a highly significant correlation
between VO2 and DO2 intra-and
post-operation The congruent or significant
relationship between VO2 and DO2
expressed the stable balance oxygen
between demand and consumption after
valve replacement Furthermore, dramatic
relationship between ERO2 and VO2
strongly suggests that the increase in
VO2 was primarily accomplished by an
increase in ERO2, and usually not by an
increase CI Because patients had
pre-existing heart failure and cardiac damage
due to surgery, their ability to increase
cardiac output was limited
There was a significant effect of time
and surgery on this relation: the close
relation between VO2 and DO2 increased
over time, peaking after surgery at 6 hour
postoperative time point (T4) These findings
suggest that careful management of the
patients remains an important issue,
especially in the early postoperative
period, when patients are at higher risk for
the occurrence of oxygen debt and,
consequently, of anaerobic metabolism
CONCLUSION
Our data indicates that the progressive
increase in VO2 after isolated MVR or MVR
and concomitant aortic valve replacement
is accomplished primarily by an increase
in cardiac index and DO2 There was a significant change in the relation between VO2 and DO2 Both changes do not depend
on CPB use
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