Comparison of Goal-Directed Hemodynamic Optimization Using Pulmonary Artery Catheter and Autocalibrated Arterial Pressure Waveform Analysis Vigileo-FloTrac™ System in On-Pump Coronary Artery Bypass Graft Surgery: A Randomized Controlled Studya.

BACKGROUND: It is a challenge for anesthesiologists to balance between administering intravenous fluid, vasoactive agents, and inotropic drugs to maintain appropriate cardiac output. AIM: The aim of this study was to evaluate the effect of treatment algorithm guided either by pulmonary artery catheter (PAC) or by the fourth generation FloTrac/Vigileo system combined with monitoring of oxygen transport on hemodynamic management and outcome after coronary artery bypass graft surgery (CABG). SETTINGS AND
DESIGN: This study design was a prospective randomized controlled clinical study. PATIENTS AND METHODS: Sixty patients aged 45-65 years, scheduled for CABG surgery for two or more grafts with cardiopulmonary bypass, were randomized into two groups 30 patients in each; (1) (Group P) patients in which PAC was inserted into internal jugular vein and connected to monitor. (2) (Group F) Patients in which arterial pressure catheter was inserted in radial artery and connected to the FloTrac sensor and Vigileo monitor. STATISTICAL ANALYSIS USED: Student's t-test or Mann-Whitney U-test and Chi-square or Fisher's exact tests were used.
RESULTS: Central venous pressure rose at the end of surgery in both groups and postoperatively declined transiently. Although the volume of crystalloids administered during surgery did not differ significantly between the groups, Group F received 24% more crystalloids and 3-fold more colloids postoperatively. Duration of postoperative respiratory support increased by 36% in Group P (P = 0.04).
CONCLUSIONS: Goal-directed therapy based on pulse pressure analysis and oxygen transport increases the volume of fluid therapy, improves hemodynamics, and reduces the duration of respiratory support after CABG surgery.

INTRODUCTION

Early goal-directed therapy in high-risk surgery[1] is a term used to describe the guidance of intravenous fluid and vasopressor/inotropic therapy using cardiac output (CO) or similar parameters such as stroke volume, cardiac index (CI), peripheral vascular resistance, blood pressure, and the variation of stroke volume to optimize volume status, myocardial contractility, and tissue perfusion.[2] It has been associated with reduced postoperative morbidity and mortality, along with decreased cardiac complications.[3]

It is a challenge for anesthesiologists to balance between administering intravenous fluid, vasoactive agents, and inotropic drugs to maintain appropriate CO. In several studies that focused on cardiac output optimization, a cardiac output monitor was used to bring the patient to the plateau of the Frank–Starling curve.[2]

A pulmonary artery catheter (PAC) with intermittent thermodilution has been used as a clinical gold standard CO measurement, but it causes increased cardiovascular complication compared with less-invasive CO monitors, so its use has decreased, and consequently, there has been an increased use of minimally invasive monitoring techniques in operating rooms and Intensive Care Units (ICUs).[4]

The term, “minimally invasive monitoring,” indicates any monitoring technique that is less invasive than PAC; currently, minimally invasive monitoring techniques include the Vigileo-FloTrac™ system, PiCCO™ monitor, LiDCO™ system, and pressure recording analytic method.[56]

PATIENTS AND METHODS

The Ethical Committee of our institute approved this randomized prospective controlled study to be executed in Fayoum University Hospital for 2 years (from February 2016 to February 2018) on 60 patients scheduled for elective coronary artery bypass graft (CABG) surgery for two or more grafts with cardiopulmonary bypass (CPB) with an expected time of CPB between 45 min and 2 h, after obtaining a written informed consent for anesthesia from each patient after explaining to them the nature of study and complications.

Inclusion criteria included patient's aged 45–65-year-old, both sexes, and those who scheduled for elective CABG surgery for two or more grafts with CPB with an expected time of CPB between 45 min and 2 h.

Exclusion criteria included history of cardiac surgery, severe congestive heart failure (ejection fraction ≤25%), cardiac arrhythmias, cardiac valve disease, intracardiac shunt, extreme obesity, severe pulmonary diseases, and history of coagulation disorders.

The patients were randomized into two groups (30 patients in each group) using computer-generated random number.

Group P: Patients in which PAC was inserted into internal jugular vein and connected to monitor and the placement is confirmed by arterial wave pressure and chest X-ray. Group F: Patients in which arterial pressure catheter was inserted in radial artery and connected to the FloTrac sensor and Vigileo monitor (version 4.00).

Under local infiltration anesthesia (lidocaine 2%), a peripheral venous cannula (14 or 16 G) and a 20 G arterial cannula were inserted after Allen's test to select radial or ulnar arterial cannulation, the arterial cannula was connected to the fourth generation FloTrac Vigileo system for the patient assigned for Group F.

Anesthesia was induced in a slow smooth, controlled fashion with thiopental 3–5 mg. kg−1, fentanyl 2–10 ug. kg−1, and pancuronium 0.1 mg. kg−1.

The patient was intubated with an oral cuffed endotracheal tube and was connected to the ventilator. After intubation a triple lumen central venous catheter triple-lumen 7.5 French was inserted in the right internal jugular vein.

A 7.5 French four-port PAC was inserted in the right internal jugular vein in Group P and their position confirmed by pressure wave and chest X-ray and connected to the pressure transducer system and CO monitor (Datascope).

Anesthesia was maintained with isoflurane with incremental does of fentanyl 1–2 ug. kg−1 with total fentanyl does 25–35 ug. kg−1 and pancuronium 0.01 mg. kg−1 every 90 min. On CPB, anesthesia was maintained with propofol 50–100 mg. kg−1.min−1.

Nonpulsatile CPB at 2.0–3.0 L. min−1.m2−1 was conducted using a membrane oxygenator (D903 Avant Phisio; Dideco, Mirandola, Italy) with hypothermia (28°C core temperature). The circuit was primed with Ringer's acetate, mannitol, and heparin. Before weaning from CPB, all patients were warmed to a 37°C nasopharyngeal temperature.

For cardiac arrest and myocardial protection, we were used continuous warm blood cardioplegia through the cardiopulmonary machine.

Restoration of cardiac function after bypass time was either spontaneous or facilitated by means of an epicardial pacemaker or defibrillator at 15–30 J and weaning from CPB was performed in a stepwise manner.

Fluid replacement included crystalloid solutions with an initial infusion rate 6–7 mL. kg−1. h−1 before and during anesthesia and 1–2 mL. kg−1.h−1.

The hemodynamic optimization in Group P was targeted using parameters provided by PAC including pulmonary arterial occlusion pressure (PAOP), CI, and systemic vascular resistance index (SVRI), as shown in Figure 1.

Figure 1

The algorithms of goal-directed hemodynamic optimization: (a) The PAC group, (b) the FloTrac/Vigileo system group. CPB = Cardiopulmonary bypass; MAP = Mean arterial pressure; PAOP = Pulmonary artery occlusion pressure; CI = Cardiac index; SVI = Stroke volume index; SVV = Stroke volume variation; ScvO2 = Central venous oxygen saturation; SVRI = Systemic vascular resistance index

In Group F, hemodynamics managed using arterial waveform analysis including CI, stroke volume index (SVI), and stroke volume variation (SVV), as measured with the FloTrac transducer and connected to Vigileo monitor (FloTrac/Vigileo system version 4.00), as shown in [Figure 1].

The primary outcome of this prospective randomized and observer study was to compare the volume of fluid therapy between groups. The secondary outcomes of this study were to compare hemodynamics and the duration of respiratory support after elective on-pump CABG surgery between groups.

Statistical analysis

The sample size was calculated using G power program 3.1.9.2. Data were analyzed using IBM SPSS advanced statistics (Statistical Package for the Social Sciences), version 21 (SPSS Inc., Chicago, IL).

Data were checked for normal distribution by means of the Kolmogorov–Smirnov's test. Values are presented as mean ± standard deviation or median (range) for parametrically or nonparametrically distributed variables, respectively. In compliance with the distribution of data, Student's t-test or Mann–Whitney's U-test was used for comparisons between groups. Intragroup comparisons were performed using parametric or nonparametric repeated measure of variance (Friedman test) as appropriate. Chi-square or Fisher's exact tests were used to compare between the groups with respect to categorical data. P ≤ 0.05 was considered statistically significant. All tests are two tailed.

RESULTS

Sixty patients were included in our study and were randomly divided into two groups, and each group has 30 patients.

There was no statistically significant difference between the study groups as regards age, weight, and height, as shown in Table 1.

Table 1

Comparison of the mean of age, weight, and height in different study groups

Although the volume of crystalloids administered during surgery did not differ significantly between the groups, Group F received 24% more crystalloids and 3-fold more colloids postoperatively (P < 0.05). The total volume of postoperative fluid therapy in this group exceeded that of Group P by 20% (P = 0.01). The postoperative fluid balance tended to be higher in Group F, as shown in Table 2.

Table 2

Comparison of crystalloids intraoperative, crystalloids during 24 h postoperative, and colloids during 24 h postoperative in different study groups

The incidence of colloid administration tended to be higher in the FloTrac group; by contrast, the incidence of inotropic/vasopressor support in FloTrac group demonstrated a trend toward lower doses as compared to the PAC-monitored patients, and the incidence of diuretic administration did not differ between the groups as shown in Table 3.

Table 3

Comparison of the systemic vascular resistance index, mean arterial pressure, and heart rate in different study groups

Regarding central venous pressure (CVP). In both groups, CVP rose at the end of surgery in both groups. Postoperatively, CVP declined transiently. In contrast, in Group F, CVP exceeded the corresponding values of Group P at 6 and 12 h (P < 0.05), as shown in Figure 2.

Figure 2

The changes in the median of central venous pressure among Group P and group F

Postoperatively, mean arterial pressure (MAP) and heart rate (HR) rose in both groups whereas SVRI decreased until 6 h compared with the preoperative values (P < 0.05). At 12 h, SVRI increased in Group P (P = 0.03) but decreased beyond 12 h postoperatively in Group F, as shown in Table 4.

Table 4

Comparison of fluids during 24 h postoperatively and fluid balance at 24 h postoperatively in different study groups

Duration of postoperative respiratory support increased by 36% in Group P (P = 0.04). However, the duration of ICU stay and hospitalization did not differ significantly, as shown in Table 5.

Table 5

Comparison of the duration of administration of inotropic/vasopressor after operation, duration of respiratory support, length of Intensive Care Unit and hospital stay in different study groups

DISCUSSION

In the current study, we evaluate the effect of GDT with treatment algorithm guided either by PAC or by fourth-generation FloTrac/Vigileo system combined with monitoring of oxygen transport on perioperative hemodynamic management and outcome after elective on-pump CABG surgery.

CVP rose at the end of surgery in both groups due to priming on the cardiopulmonary bypass. Postoperatively, CVP declined transiently with weaning from the ventilation.

In contrast, in Group F, CVP exceeded the corresponding values of Group P at 6 and 12 h with statistically significant difference, this can be explained by the high amount of crystalloids and colloids according to the treatment algorithm, and there is an significant difference within the groups compared with the preoperative value at postoperative and 24 h postoperative.

These results correspond with other studies of goal-directed therapy in cardiac surgery[127] with significant difference within this group compared with the preoperative value and at 24 h postoperative.

At the end of surgery, we found lower MAP, high SVRI, and HR values in Group P more than Group F. Systemic vasodilatation and tachycardia can be explained by the CPB-induced SIRS that might be attenuated by the FloTrac-driven fluid therapy including more crystalloids and colloids.[89]

In contrast to Group F, the patients of Group P presented with systemic vasoconstriction postoperatively, as evidenced by the increase in SVRI with statistically significant difference between two groups at postoperative, 6, 12, and 24 h postoperative, which we interpret as a compensatory mechanism counteracting the reduced blood volume.

The preload optimization following CABG surgery in Group F might have contributed to an increase in heart performance with higher SVI compared with Group P. Similar results were obtained by Hofer et al.[10]

Despite the transient perioperative changes in arterial and central venous oxygenation, we observed an increase in oxygen delivery in parallel with regress of metabolic acidosis at 24 h postoperatively in both groups. These results confirm the efficacy of the goal-directed hemodynamic optimization. Hence, there are increased oxygen transport and attenuation of the surgical stress and hypoperfusion following combined CPB and CABG surgery.

Walker and Welliver[11] validated that the FloTrac/Vigileo™ system provides reliable data that may be used to manage perioperative patient hemodynamics. The system reliably trends CO values for estimation of patients' hemodynamic. Furthermore, the monitoring system produces reliable SVV which is practical for assessing patients' need and responsiveness to the fluid. SVV contributes data that the anesthesia provider can incorporate for hemodynamic management decision-making.

As a result of goal-directed therapy, the patients in Group F received more crystalloids intraoperative and during 24 h postoperatively with no statistically significant difference between two groups regarding crystalloids intraoperative and statistically significant difference between two groups regarding crystalloids during 24 h postoperatively.

As regarding colloids, Group F has percentage of administration and receives more colloids during 24 h postoperatively with statistically significant difference between two groups.

Correction of hypovolemia and cardiac output according to the study algorithm was resulted in a better oxygen delivery and reduced the duration of respiratory support in Group F with statistically significant difference between two groups. The length of ICU and hospital stay is longer in Group F with no statistically significant difference between two groups. These findings are consistent with beneficial effects of goal-directed therapy both in coronary and general surgery patients.[123] As shown by other authors, monitoring of CI, SVRI, SVI, SVO2, and DO2I may help clinicians in initiating therapy early in the postoperative period and improve the outcome[3] using continuous minimally invasive monitoring.[12] Organ dysfunction and multiple organ failures are the main causes of prolonged hospital stay after cardiac surgery. Enhanced oxygen delivery and utilization have been associated with improved outcome.[13]

On the other hand, Hendy and Bubenek[14] did randomized control trials performed in cardiac surgery (using two types of pulse pressure analysis techniques, PiCCO and FloTrac/Vigileo); these devices did not demonstrate that they played a role in decreasing mortality but only decreasing the ventilation time and the ICU and hospital length of stay.

This study has several limitations related to the differences in study algorithms. First, we did not measure PAOP in Group F or SVV in Group P. Second, in Group P, in contrast to Group F, DO2I was determined intermittently and was not included in the algorithm of goal-directed therapy. Moreover, this single-center study has a limited number of observations and was not powered for demonstrating the reduction in ICU and hospital stay in group F.

CONCLUSIONS

Goal-directed therapy based on pulse pressure analysis and oxygen transport increases the volume of fluid therapy, improves hemodynamics, and reduces the duration of respiratory support after elective on-pump CABG surgery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.