**3. Results**

40 patients (32 men, 8 women) were included in the study. The mean age ± S.D. was 69 ± 5.8 years in Group A and 67 ± 6.8 years in Group B. Preoperative patient characteristics are pre‐ sented in Table 1. There were no statistical significant differences in preoperative character‐ istics between the groups.

Operative data are listed in Table 2. The groups were comparable for these parameters.

Statistically significant differences were found when groups were compared in regard to the use of a lesser priming volume in mini CPB as one of its main advantages in comparison with standard CPB (1501 ± 44 ml in Group A vs. 837 ± 205 ml in Group B). It was also associ‐ ated with a lower drop in hematocrit level during CPB (25.3 ± 1.1% in Group A and 31.0 ± 2.3% in Group B). The immediate postoperative values of hematocrit (ICU admission) were not significantly different.

Analysis of the data during CPB showed differences betweens groups.

The main difference was a lower real blood flow during CPB in Group B (3.5 ± 0.51 l.min-1) vs. calculated flow (4.6 ± 0.45 l.min-1) than real flow in Group A (4.9 ± 0.41 l.min-1) vs. calcu‐ lated flow (4.7 ± 0.39 l.min-1) (Table 2).

There was a direct correlation between mean arterial pressure (MAP) and ptO2 in Group A during CPB (↓MAP ≈ ↓ ptO2). Pumped blood flow was continuously maintained at the same calculated level. A decrease in ptO2 levels without correlation to MAP was found during surgery after CPB (Figure 9).

On the other hand, a direct correlation between pumped blood flow and MAP (↓flow ≈↓MAP) was found during CPB in Group B. The value of ptO2 was continuously higher and independent at this time. A decrease in ptO2 levels without correlation to MAP was found during surgery after CPB as in Group A (Figure 10).

Lower levels of ptO2 without correlation to MAP were analysed postoperatively in both groups and we observed a trend towards a reduced ptO2 during the first hours after admis‐ sion to the intensive care unit (Figure 9,10).

Arterial blood pressure, blood flow during CPB, laboratory markers of tissue perfusion,

Data from the oxymetric catheter in all patients were compared at the following time inter‐ vals: 1) 30 min after incision, 2) 15 min before CPB, 3) CPB, 4,5,6- at 20 min intervals during CPB, 7) end of crossclamp, 8) 15 min. after release of crossclamp, 9) end of CPB, 10) 15 min

Demographic and perioperative data are reported as number, means ± standard deviation (S.D.) or median. Comparisons between preoperative characteristics and perioperative data were made using the Student´s *t* test or the Mann-Whitney U-test and Kolmogorov-Smirnov test where appropriate. Values are expressed as means ± standard error of the mean (S.E.M.). Intergroup comparisons between two variables at the same time point were per‐ formed using the Mann-Whitney U-test. Group comparison was done using the Wilcoxon

The data were analyzed using the programs NCSS 2004 and Statistica. Differences were con‐

40 patients (32 men, 8 women) were included in the study. The mean age ± S.D. was 69 ± 5.8 years in Group A and 67 ± 6.8 years in Group B. Preoperative patient characteristics are pre‐ sented in Table 1. There were no statistical significant differences in preoperative character‐

Statistically significant differences were found when groups were compared in regard to the use of a lesser priming volume in mini CPB as one of its main advantages in comparison with standard CPB (1501 ± 44 ml in Group A vs. 837 ± 205 ml in Group B). It was also associ‐ ated with a lower drop in hematocrit level during CPB (25.3 ± 1.1% in Group A and 31.0 ± 2.3% in Group B). The immediate postoperative values of hematocrit (ICU admission) were

The main difference was a lower real blood flow during CPB in Group B (3.5 ± 0.51 l.min-1) vs. calculated flow (4.6 ± 0.45 l.min-1) than real flow in Group A (4.9 ± 0.41 l.min-1) vs. calcu‐

There was a direct correlation between mean arterial pressure (MAP) and ptO2 in Group A during CPB (↓MAP ≈ ↓ ptO2). Pumped blood flow was continuously maintained at the same calculated level. A decrease in ptO2 levels without correlation to MAP was found during

Operative data are listed in Table 2. The groups were comparable for these parameters.

Analysis of the data during CPB showed differences betweens groups.

after termination of CPB, 11) end of surgery, 12,13,14- at 1 h intervals in the I.C.U.

blood gases and body temperature were recorded and analyzed as well.

**2.5. Statistical analysis**

108 Artery Bypass

test for paired data.

istics between the groups.

not significantly different.

surgery after CPB (Figure 9).

lated flow (4.7 ± 0.39 l.min-1) (Table 2).

**3. Results**

sidered statistically significant at the level of *P*<0.05.

**Figure 9. Levels of ptO2, blood flow and MAP in Group A (standard CPB) in intervals** (Intervals: 1- 30 min. after incision, 2- 15 min. before CPB, 3- CPB, 4,5,6- à 20 min. of CPB, 7- end of crossclamp, 8- after 15 min., 9- end of CPB, 10 after 15 min., 11- end of surgery, 12,13,14- à 1 h. I.C.U.)

Changes of ptO2 at this time compared with initial level are shown in Figure 11.

Higher levels of ptO2 during and after CPB in comparison with initial levels were observed in Group B. A decrease in ptO2 levels after surgery was found in both groups.

Changes in flow (%) in time compared to calculated flow are shown in Figure 12.

A higher blood flow during perfusion was analysed in Group A and lower than calculated blood flow was found in Group B.

We also observed a lower muscle oxygen (ptO2) tension than in arterial blood during the

Peripheral Tissue Oxygenation During Standard and Miniaturized Cardiopulmonary Bypass (Direct Oxymetric Tissue

Peri-operative biochemical parameters of perfusion (arterial blood gas variables) are shown

**before CPB** 7.41 ± 0,06 7.42 ± 0,04 n.s. **during CPB** 7.42 ± 0,07 7.41 ± 0,03 n.s. **after CPB** 7.39 ± 0,03 7.37± 0,04 n.s.

**before CPB** 142 ± 81 182 ± 72 n.s. **during CPB** 171± 31 191 ± 31 n.s. **after CPB** 191 ± 71 189 ± 48 n.s.

**before CPB** 35 ± 3 37 ± 4 n.s. **during CPB** 38 ± 6 39 ± 3 n.s. **after CPB** 39 ± 5 37 ± 7 n.s.

**before CPB** - 0.53 ± 1.72 - 0.54 ± 1.34 n.s. **during CPB** 0.45 ± 1.91 0.29 ± 1.72 n.s. **after CPB** - 1.39 ± 1.8 - 0.40 ± 1.4 n.s. **DO2 [ml.min-1.m-2]** 259 ± 34 256 ± 39 n.s.

There were no significant differences in postoperative levels of lactate and arterial blood gas

**I.C.U. admission** 7,45 ± 0,03 7,46 ± 0,06 n.s. **I.C.U after 6 h** 7,37 ± 0,05 7,43 ± 0,03 n.s.

**Group B**

**(n=20) p-value**

**Group A (n=20)**

**Group B**

**(n=20) p-value**

Perfusion Monitoring Study) http://dx.doi.org/10.5772/54300 111

**Group A (n=20)**

whole operation in both groups.

in Table 4. There were no statistically significant differences.

**pH**

**pO2 [mm Hg]**

**pCO2 [mm Hg]**

**BE**

**Table 4.** Laboratory characteristics of perfusion (arterial blood gases)

variables between groups (Table 5).

**pH**

**Figure 10. Levels of ptO2, blood flow and MAP in Group B (mini CPB) in intervals** (Intervals: 1- 30 min. after inci‐ sion, 2- 15 min. before CPB, 3- CPB, 4,5,6- à 20 min. of CPB, 7- end of crossclamp, 8- after 15 min., 9- end of CPB, 10 after 15 min., 11- end of surgery, 12,13,14- à 1 h. I.C.U.)

**Figure 11.** Changes of ptO2 compared to initial levels (%)(Group A- green line, Group B- blue line. Intervals: 1- 30 min. after incision, 2- 15 min. before CPB, 3- CPB, 4,5,6- à 20 min. of CPB, 7- end of crossclamp, 8- after 15 min., 9- end of CPB, 10-after 15 min., 11- end of surgery, 12,13,14- à 1 h. I.C.U.)

**Figure 12.** Changes in blood flow (%) during perfusion compared to calculated flow (Group A- green line, Group Bblue line. Intervals: 1- CPB, 2,3,4- à 20 min. of CPB, 5-end of crossclamp, 6- after 15 min.)

We also observed a lower muscle oxygen (ptO2) tension than in arterial blood during the whole operation in both groups.

Peri-operative biochemical parameters of perfusion (arterial blood gas variables) are shown in Table 4. There were no statistically significant differences.


**Table 4.** Laboratory characteristics of perfusion (arterial blood gases)

**Figure 10. Levels of ptO2, blood flow and MAP in Group B (mini CPB) in intervals** (Intervals: 1- 30 min. after inci‐ sion, 2- 15 min. before CPB, 3- CPB, 4,5,6- à 20 min. of CPB, 7- end of crossclamp, 8- after 15 min., 9- end of CPB, 10-

**Figure 11.** Changes of ptO2 compared to initial levels (%)(Group A- green line, Group B- blue line. Intervals: 1- 30 min. after incision, 2- 15 min. before CPB, 3- CPB, 4,5,6- à 20 min. of CPB, 7- end of crossclamp, 8- after 15 min., 9- end of

**Figure 12.** Changes in blood flow (%) during perfusion compared to calculated flow (Group A- green line, Group B-

blue line. Intervals: 1- CPB, 2,3,4- à 20 min. of CPB, 5-end of crossclamp, 6- after 15 min.)

after 15 min., 11- end of surgery, 12,13,14- à 1 h. I.C.U.)

110 Artery Bypass

CPB, 10-after 15 min., 11- end of surgery, 12,13,14- à 1 h. I.C.U.)

There were no significant differences in postoperative levels of lactate and arterial blood gas variables between groups (Table 5).



On the other hand some studies do not entirely confirm the positive clinical effect of using minisystems [13], even though the laboratory tests of these studies lean towards miniinva‐

Peripheral Tissue Oxygenation During Standard and Miniaturized Cardiopulmonary Bypass (Direct Oxymetric Tissue

Perfusion Monitoring Study) http://dx.doi.org/10.5772/54300 113

One discussed question while using CPB is the constant value of blood flow during the op‐ eration [1,2]. Preoperative calculated value of optimal blood flow using mini CPB is the

Nevertheless adequate and optimal blood flow during CPB is still an important question. There are no standards for optimal pump flow during CPB. Initial flow is calculated on the basis of body surface area and a temperature management strategy. The calculated blood

The reason for the necessary decrease in pumped blood flow is the increase in arterial blood pressure during the operation most likely as a result of increased blood in the vascular bed

Another reason for decreased flow could be the flooding of the operating field during wors‐

Decreased venous return could be another reason. The flow of a centrifugal pump during mini CPB is fully dependent upon adequate venous return with resultant filling of the ve‐

In an effort to achieve the calculated blood flow the centrifugal rotational velocity is in‐ creased resulting in increased suction pressure within the venous part of the system and thus suction of the artifact with the venous cannulas. The ability to control flow via a cardi‐ otomy reservoir is missed in this case. A possible solution is an increase of blood in the body (patient´s body position in space, application of vasopressors, filling of the circulatory sys‐ tem) or decreasing blood flow in the system. The "antitrendelenburg" position (head up), during which the filling of the lower half of the body is partly increased and consequently an increased venous flow (return), is of some advantage. Further, in this position the heart chambers are adequately emptied. The trendelenburg position described in the literature as a means to increase venous return has typically no effect when mini CPB is applied. In the

It is necessary during the procedure to have a coordinated approach between the surgeon,

During an acute case of a decrease in the pumped blood flow, in the presence of an impaired venous return, filling was supplemented by blood collected in a collapsible bag at the begin‐ ning of the operation. To restore satisfactory parameters usually a sufficient volume of less

The perfusion pressure in both groups was maintained at levels between 50-70 mmHg [1,3,9,10]. In the case of mini CPB this did not fall below 50 mmHg while on the other hand

flow often has to be decreased during perfusion using mini CPB.

case of a closed system the patient´s own body is the reservoir.

there was a tendency for higher levels of pressure.

sive systems compared to standard CPB.

same as standard CPB.

(an absence of a CPB reservoir).

anesthesiologist and perfusionist.

than 100ml was required.

ened venous return.

nous bed of the patient.

**Table 5.** Postoperative laboratory characteristics of perfusion (arterial blood gases, lactate)

No death, acute renal failure, or stroke occured during the postoperative course either group. The only differences were postoperative atrial fibrillation (6 in Group A, 2 in Group B) (Table 3).

There were no cases of local complications at the site of inserted sensors, and there were no signs of general infection or sepsis in either group.
