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Prediction of fluid responsiveness using dynamic preload indices in patients undergoing robot-assisted surgery with pneumoperitoneum in the Trendelenburg position.

SUMMARY

We investigated the abilities of pulse pressure variation (PPV) and stroke volume variation (SVV) to predict fluid responsiveness during robot-assisted laparoscopic prostatectomy, requiring pneumoperitoneum and the Trendelenburg position. In 42 patients without cardiopulmonary disease, PPV and SVV were measured before and after administration of 500 ml colloid under pneumoperitoneum combined with the steep Trendelenburg position (35[degrees]). Fluid responsiveness was defined as a [greater than or equal to] 15% increase in stroke volume after the fluid loading measured using transoesophageal echocardiography. Of the 42 included patients, 22 were responders and 20 were non-responders. A PPV of [greater than or equal to] 9.5% identified responders with a sensitivity of 77.3% and a specificity of 90.0%, and a SVV of [greater than or equal to] 9.5% also identified responders with a sensitivity of 77.3% and a specificity of 75.0%. The area under receiver operating characteristic curves for PPV and SVV were 0.87 (P <0.001) and 0.81 (P=0.001), respectively. The findings suggest that both PPV and SVV could be useful predictors of fluid responsiveness in patients without cardiopulmonary disease undergoing robotic laparoscopic surgery with pneumoperitoneum in the Trendelenberg position.

Key Words: preload, pulse pressure variation, stroke volume variation, fluid responsiveness, pneumoperitoneum, Trendelenburg

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Adequate cardiac preload is one of the most important factors for optimising cardiac output. Although achieving adequate cardiac preload has been guided by static preload indices such as central venous pressure and pulmonary artery occlusion pressure, these indices do not always provide reliable information on cardiac preload (1,2). As an alternative to these static indices, dynamic preload indices, such as pulse pressure variation (PPV) and stroke volume variation (SVV), have been reported to indicate cardiac response to volume loading in several clinical settings during mechanical ventilation (3-8). PPV and SVV are based on heart-lung interactions induced by cyclic changes in intrathoracic pressure during mechanical ventilation (9).

Laparoscopy is increasingly used for major abdominal and pelvic surgery. Laparoscopic surgery for the abdominal visceral organs requires pneumoperitoneum and the Trendelenburg position to optimise surgical conditions, and can reduce cardiac output and respiratory compliance (10). Intrathoracic pressure has been known to increase in patients with raised intra-abdominal pressure and the Trendelenburg position (10) Accordingly, the usefulness of PPV and SVV, which are affected by changes in intrathoracic pressure, in predicting fluid responsiveness during laparoscopic surgery under these conditions may be questioned. An animal study showed that PPV, but not SVV, could predict fluid responsiveness under isolated pneumoperitoneum (11). In contrast, another recent study reported that PPV and SVV could not predict fluid responsiveness during laparoscopic surgery (12), but the implications were limited by the uncontrolled clinical conditions, such as ongoing blood loss, use of vasopressors, and changes in ventilator settings during measurement, which could have affected the cardiac response to volume loading.

In the current study we investigate the abilities of PPV and SVV to predict fluid responsiveness in patients who undergo robot-assisted (da Vinci[TM] Surgical System; Intuitive Surgical, Mountain View, CA, USA) laparoscopic radical prostatectomy, which involves both pneumoperitoneum and the Trendelenburg position.

MATERIALS AND METHODS

Patients

The study protocol was approved by the Institutional Review Board at Asan Medical Center (AMC 2011-1028), and written informed consent was obtained from each patient. This study was registered with the Clinical Research Information Service (KCT 0000165). Forty-five patients scheduled for robot-assisted laparoscopic radical prostatectomy were enrolled and 42 patients were evaluated. Patients with arrhythmias, body mass index <15 or >40 kg/[m.sup.2], valvular heart disease, coronary artery disease, left ventricular ejection fraction <50%, pulmonary disease, or oesophageal disease were excluded.

After application of routine haemodynamic monitoring (three-lead electrocardiogram, noninvasive blood pressure and pulse oximetry), anaesthesia was induced using a bolus intravenous injection of thiopentone 4 to 5 mg/kg. This was followed by vecuronium 0.1 mg/kg. After tracheal intubation, patients were mechanically ventilated with a tidal volume of 8 ml/kg at a respiratory rate of 8 to 12 per minute to maintain end-tidal C[O.sub.2] between 28 and 35 mmHg. Positive end-expiratory pressure was not applied and the inspiratory-to-expiratory time ratio was set to 1:2. Fentanyl 2 [micro]g/kg was administered before skin incision and anaesthesia was maintained with sevoflurane 1 to 2 minimum alveolar concentrations, in oxygen-enriched (50%) air.

Automated calculation of SVV

A 20-gauge catheter was inserted into the radial artery and connected to the FloTrac[TM]/Vigileo[TM] system with software version 3.02 (Edwards Lifesciences, CA, USA). This system displays stroke volume (SV) and cardiac output continuously by pulse contour analysis, with calculations performed on data from the previous 20 seconds (13,14). SVV represents the variation of pulse contour derived beat-to-beat SV from the mean value during the previous 20 seconds data. Maximal (SVmax) and minimal (SVmin) values were determined within each period, and SVV was calculated as: SVV = (SVmax - SVmin)/[(SVmax + SVmin)/2]. The mean values of three measurements at each time point were used for analysis.

Automated calculation of PPV

Pulse pressure was defined as the difference between systolic and diastolic arterial pressure. Maximal (PPmax) and minimal (PPmin) values were determined, and PPV was calculated as: PPV = (PPmax--PPmin)/[(PPmax + PPmin)/2] (15). PPV was automatically determined by the IntelliVue MP70 monitor (Philips Medizinsysteme, Boeblingen, Germany) and was calculated from the data during four consecutive windows of eight seconds. The mean values of three measurements at each time point were used for analysis.

Echocardiographic measurements

Transoesophageal echocardiography (TOE) was performed using an iE33 Ultrasound System (Philips Ultrasound, Bothell, WA, USA) and a S7.2 OMNI probe. One experienced cardiac anaesthetist performed all echocardiographic examinations.

The left ventricular outflow tract diameter was determined in a mid-oesophageal aortic long axis view. Aortic blood flow velocities were measured using pulsed wave Doppler in a deep transgastric long axis view at the same site as the left ventricular outflow tract diameter measurement. The aortic blood flow velocity time integral at end-expiration was measured, and the averaged aortic blood flow velocity time integrals of three consecutive respiratory cycles were used to calculate SV. The SV was calculated using the formula:

SV = left ventricular outflow tract area x aortic flow velocity time integral where left ventricular outflow tract area = [pi] (left ventricular outflow tract diameter) (2) /4.

Study protocol

When haemodynamically stable conditions were reached, measurements were performed at the following four points: after induction of anaesthesia in the supine position ([T.sub.S]), three minutes after pneumoperitoneum during which time insufflation pressure was set to 20 mmHg ([T.sub.P]), three minutes after the steep Trendelenburg position (35[degrees] which was measured with protractor) was added to pneumoperitoneum during which time insufflation pressure was set to 15 mmHg ([T.sub.P+T]), and three minutes after administration of 500 ml of colloid (Voluven[R]; Fresenius Kabi, Germany) over ten minutes using an infusion pump in the [T.sub.P+T] position ([T.sub.P+T/VL]) (Figure 1). In general, insufflation pressure during laparoscopic surgery did not exceed 15 mmHg. We employed 15 mmHg of insufflation pressure at [T.sub.P+T] and [T.sub.P+T/VL] consistent with that used during the surgery. On the other hand, 20 mmHg of insufflation pressure (which has been reported to be the maximum to allow stable haemodynamics (16)) was applied at [T.sub.P] transiently to maximise the effect of the pneumoperitoneum on PPV and SVV. The effects of position on PPV and SVV were determined at [T.sub.S], [T.sub.P] and [T.sub.P+T], and the abilities of PPV and SVV to predict fluid responsiveness under pneumoperitoneum combined with the Trendelenburg position were determined at [T.sub.P+T] and [T.sub.P+TVL].

At each time point, the following variables were measured; heart rate, mean arterial blood pressure, PPV, SVV, airway peak pressure, airway plateau pressure, end-tidal C[O.sub.2] and echocardiographic variables. One investigator measured PPV, SVV, and other haemodynamic and respiratory variables and another investigator simultaneously measured echocardiographic variables. Total static compliance of the respiratory system was calculated as: static compliance = tidal volume/(airway plateau pressure - positive end-expiratory pressure).

During data recording, ventilator settings and anaesthetic depth were kept unchanged and stimulus to patients, inotropes and vasopressors were avoided. The study protocol was stopped in patients requiring inotropes or vasopressors for unstable haemodynamics (mean arterial blood pressure <60 mmHg), or the occurrence of an arrhythmia.

Statistical analysis

Continuous data are expressed as mean [+ or -] SD for parametric data or median (interquartile range [IQR]) for non-parametric data, and categorical data as number and percentages. A sample size was chosen to achieve 80% power to detect a difference of 0.25 between the area under the receiver operating characteristics (ROC) curve under the null hypothesis of 0.5 and the area under ROC curve under alternative hypothesis of 0.75 using a two-sided t-test at a significance level of 0.05. It was calculated that a minimum sample size of 40 patients was required. Expecting a dropout rate of about 10%, we aimed to enrol 45 patients. To evaluate the effect of pneumoperitoneum and the Trendelenburg position on haemodynamic and respiratory variables, one-way repeated measures analysis of variance (ANOVA) or one-way repeated measures ANOVA on rank were used. If the one-way repeated measures ANOVA or one-way repeated measures ANOVA on rank revealed a significant interaction, post hoc analysis was performed using Bonferroni or Dunn's test. To compare the changes in haemodynamic and respiratory variables before and after volume loading under pneumoperitoneum combined with the Trendelenburg position, a paired Student's t-test or Mann-Whitney U test were used.

Patients were classified as responders if volume loading induced an increase in stroke volume determined using transoesophageal echocardiography (SV-TOE) [greater than or equal to] 15% under pneumoperitoneum combined with the Trendelenburg position, compared with that before volume loading in the same position; and as non-responders otherwise (17). The ability to predict fluid responsiveness was quantified for PPV and SVV by calculating the area under the ROC curves. The area under ROC curve was calculated by an extended trapezoidal rule, and a confidence interval (CI) of the area under ROC curve was constructed using DeLong's variance estimate (18). After the ROC curve was constructed, the optimal cutoff value was defined as the value based on Youden's Index, which was calculated as maximum {sensitivity + specificity-1} (19,20).

A P value <0.05 was considered statistically significant. All statistical analysis was performed using SAS software, version 9.1 (SAS Institute, Cary, NC, USA).

RESULTS

Of the 45 patients, three were excluded: two patients who developed arrhythmias after establishing the pneumoperitoneum (one with a third-degree atrioventricular block and one with frequent premature ventricular contractions) and one patient whose operation changed to open prostatectomy due to unexpected intra-abdominal adhesions. The remaining 42 patients completed this study protocol. The patients' characteristics are shown in Table 1.

Abilities of PPV and SW to predict fluid responsiveness in pneumoperitoneum combined with the Trendelenburg position

Of the 42 included patients, 22 were responders and 20 were non-responders. Before volume loading, PPV and SVV were higher in responders than in non-responders (P <0.001 and <0.001, respectively) (Figure 2). After volume loading, PPV decreased significantly in responders (mean [+ or -] SD, 12.4 [+ or -] 4.2 vs 7.3 [+ or -] 2.5%, P <0.001) and non-responders (median [IQR], 7.0 [6.0 to 8.5] vs 5.0 [4.0 to 7.21%, P=0.003), as did SVV in responders (12.9 [+ or -] 4.3 vs 9.1 [+ or -] 3.6%, P <0.001) and non-responders (9.0 [+ or -] 2.2 vs 7.8 [+ or -] 2.5%, P=0.041) (Table 2).

According to the ROC curve analysis, PPV and SVV were able to predict the response to volume loading at [T.sub.P+T]. The area under ROC curve for PPV and SVV were 0.87 (95% CI: 0.75 to 0.99, P <0.001) and 0.81(95% CI: 0.68 to 0.94, P=0.001), respectively (Figure 2). A PPV cutoff value of 9.5% discriminated between responders and non-responders with a sensitivity of 77.3% (95% CI: 54.6 to 92.2) and a specificity of 90.0% (95% CI: 68.3 to 98.8). A SVV cutoff value of 9.5% discriminated between responders and non-responders with a sensitivity of 77.3% (95% CI: 54.6 to 92.2) and a specificity of 75.0% (95% CI: 50.9 to 91.3).

Effect of position on haemodynamic and respiratory variables

Haemodynamic and respiratory variables at different positions were shown in Table 3. PPV (median [IQR], 9.0 [5.7 to 11.3] at [T.sub.S] vs 16.0 [11.0 to 22.4]% at [T.sub.P], P <0.001) and SVV (8.0 [6.5 to 9.3] at [T.sub.S] vs 16.4 [11.5 to 21.41% at [T.sub.P], P <0.001) were significantly higher at [T.sub.P] than at [T.sub.S] along with decreased SV-TOE and total static compliance of the respiratory system (Figure 3). At [T.sub.P+T], PPV (16.0 [11.0 to 22.4] at [T.sub.P] vs 8.9 [7.0 to 12.01% at [T.sub.P+T], P <0.001) and SVV (16.4 [11.5 to 21.4] at [T.sub.P] vs 10.0 [8.0 to 13.0]% at [T.sub.P+T], P <0.001) were significantly lower than at [T.sub.P], while SV-TOE was increased and total static compliance were unchanged compared with those at [T.sub.P].

DISCUSSION

We have shown that both PPV and SVV [greater than or equal to] 9.5% are useful predictors of an increase of SV [greater than or equal to] 15% after 500 ml colloid fluid loading even under conditions of pneumoperitoneum and steep Trendelenburg position in patients without cardio-pulmonary disease. PPV and SVV increased with a concomitant decrease in SV under pneumoperitoneum compared with the supine position. In addition, PPV and SVV decreased with an increase in SV under pneumoperitoneum with the steep Trendelenburg position compared to pneumoperitoneum alone.

The abilities of PPV and SVV to predict fluid responsiveness have been studied in several clinical settings that altered respiratory compliance. PPV and SVV have been shown to predict fluid responsiveness in patients in the prone position during scoliosis surgery, although higher cutoff values were needed to identify responders in the prone position compared to the supine position (7). In contrast, PPV was unable to predict fluid responsiveness in patients receiving protective mechanical ventilation due to acute respiratory distress syndrome (21). Our results show that PPV and SVV could be a useful predictor of fluid responsiveness under pneumoperitoneum combined with the steep Trendelenburg position and was consistent with those of previous studies which demonstrated fluid responsiveness of dynamic preload indices (5,7,15). In addition, we found that PPV and SVV were significantly higher with than without pneumoperitoneum in the supine position. It has been recently reported that both PPV and SVV did not change under pneumoperitoneum (10 to 12 mmHg of insufflation pressure) and were poorly predictive of fluid responsiveness during laparoscopic surgery (12). The higher insufflation pressure (20 mmHg) in the present study compared with the previous study might explain the different result. Moreover, the previous study did not control the clinical conditions such as blood loss, use of vasopressors, and changes in ventilator settings which may alter PPV and SVV independent of volume loading.

We also found that pneumoperitoneum resulted in an increased mean arterial blood pressure, decreased SV, and increased PPV and SVV compared with the supine position, and pneumoperitoneum combined with Trendelenburg position resulted in an unchanged mean arterial blood pressure, increased SV, unchanged PPV, and increased SVV compared with isolated pneumoperitoneum. The change in PPV and SVV during pneumoperitoneum might be attributable to a decrease in chest wall compliance caused by an increase in abdominal pressure (22). Chest wall compliance compressing cardiovascular structures has been reported to be a primary determinant of pleural pressure variation, irrespective of lung compliance (21). Reduced chest wall compliance increases pleural pressure variation (23), being associated with an increase in dynamic indices of fluid responsiveness (24,25). The pneumoperitoneum-induced increases in abdominal pressure may compress the inferior vena cava, resulting in decreased right ventricular preload. Furthermore, increased inspiratory pressure has been shown to disturb venous return (26).

Elevated PPV and SVV cut-off values for discriminating fluid responsiveness might be expected under conditions of pneumoperitoneum combined with steep Trendelenburg position, because elevated intra-abdominal pressure shifts the diaphragm cephalad, leading to increased intrathoracic pressure and stiffened abdominal part of the chest wall (27). Pneumoperitoneum has been known to decrease chest wall compliance (22). Indeed, reduced total static compliance of the respiratory system during pneumoperitoneum in our results might reflect decreased chest wall compliance which is one determinant of total static compliance of the respiratory system. However, the PPV and SVV cutoff values we measured were not as high as in previous studies (7,11). The PPV and SVV cutoff values in the present study may have been affected primarily by our use of the steep Trendelenburg position. Addition of this position, a 35[degrees] incline, to pneumoperitoneum may induce an increase in cardiac preload, together with decreases in PPV and SVV, compared with those observed under pneumoperitoneum alone. The Trendelenburg position has been known to augment the cardiac preload (28).

In our results, the clinical utility of PPV and SVV may not apply to all patients undergoing major laparoscopic surgery, because about a quarter of patients, both responders and non-responders, showed values of PPV and SVV in an opposite direction to the cut-off values. Moreover, our results do not necessarily apply to patients with arrhythmias, body mass index <15 or >40 kg/[m.sup.2], valvular heart disease, coronary artery disease, left ventricular ejection fraction <50% or pulmonary disease. We think that other haemodynamic indices such as blood pressure should be considered when choosing fluid administration strategies based on the value of PPV and SVV. For example, fluid administration might be preferentially performed if a patient shows unstable haemodynamics combined with a lower value (<9.5%) of dynamic preload indices during laparoscopic surgery. However, in the absence of more reliable indices to guide fluid management during major laparoscopic surgery, the present study suggests that dynamic preload indices such as PPV and SVV might be helpful to predict fluid responsiveness and thereby to optimise fluid therapy in patients during major laparoscopic surgery with pneumoperitoneum in the Trendelenberg position.

Our study has other limitations as we did not examine the ability of PPV and SVV to predict fluid responsiveness in the supine position. Therefore, we did not measure the cut-off values of PPV and SVV in the supine position as baseline values. Most patients who underwent robot-assisted laparoscopic radical prostatectomy by experienced urologic surgeons in our institution experienced less than 500 ml of intraoperative bleeding. Thus, administration of over 500 ml fluid could have led to volume overloading. Also, the utilities of PPV and SVV during isolated pneumoperitoneum were not assessed. Further studies will be needed to evaluate the abilities of PPV and SVV during isolated pneumoperitoneum. However, the Trendelenburg position is needed for surgical access during laparoscopic surgery for abdominal organs. Thus, the clinical relevance for the present study still applies. TOE used for SV is not the gold standard method for measuring cardiac output. However, cardiac output measured by TOE has been reported to be in very good agreement with cardiac output derived by thermodilution (29).

In conclusion, both PPV and SVV could be useful predictors of fluid responsiveness in patients without cardiopulmonary disease even during pneumoperitoneum combined with the steep Trendelenburg position. Further study is needed to assess the value of these indices under these conditions in patients with cardiopulmonary disease.

Caption: Figure 1: The time line for the study process. PnP = pneumoperitoneum, [T.sub.s] = after induction of anaesthesia in the supine position, [T.sub.p] = three minutes after pneumoperitoneum during which time insufflation pressure was set to 20 mmHg, [T.sub.P+T] = three minutes after the steep Trendelenburg position (35[degrees]) was added to pneumoperitoneum during which time insufflation pressure was set to 15 mmHg, [T.sub.P+T/VL] = three minutes after administration of 500 ml colloid over ten minutes at the [T.sub.P+T] position.

Caption: Figure 2: Under pneumoperitoneum with the steep Trendelenburg position, (A) individual values of pulse pressure variation (PPV) and stroke volume variation (SVV) before volume loading in responders (R) and non-responders (NR) (solid and dotted line represent median value and cut-off value to discriminate between R and NR, respectively.), and B) receiver operating characteristic curves demonstrating the performances of PPV and SVV. A = area under the receiver operating characteristic curves.

Caption: Figure 3: Changes in pulse pressure variation (PPV) and stroke volume variation (SVV) at different positions. The top, bottom, and line through the middle of the box in panels correspond to 75th percentile (top quartile), 25th percentile (bottom quartile), and 50th percentile (median), respectively. The whiskers extend from the 10th percentile (bottom decile) and to the 90th percentile (top decile). [T.sub.s] = after induction of anaesthesia in the supine position, [T.sub.P] = three minutes after pneumoperitoneum during which time insufflation pressure was set to 20 mmHg, [T.sub.P+T] = three minutes after the steep Trendelenburg position (35[degrees]) was added to pneumoperitoneum during which time insufflation pressure was set to 15 mmHg. * P < 0.05 vs [T.sub.s]. [dagger] P < 0.05 vs [T.sub.P].

ACKNOWLEDGEMENT

We thank Seon-Ok Kim, BS, of the Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, Seoul, Korea, for help with the statistical work.

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(15.) Derichard A, Robin E, Tavernier B, Costecalde M, Fleyfel M, Onimus Jet al. Automated pulse pressure and stroke volume variations from radial artery: evaluation during major abdominal surgery. Br J Anaesth 2009; 103:678-684.

(16.) Marik PE, Cavallazzi R, Vasu T, Hirani A. Dynamic changes in arterial waveform derived variables and fluid responsiveness in mechanically ventilated patients: a systematic review of the literature. Crit Care Med 2009; 37:2642-2647.

(17.) DeLong ER, DeLong DM, Clarke-Pearson DL. Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach. Biometrics 1988; 44:837-845.

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J. H. CHIN *, E. H. LEE ([dagger]), G. S. HWANG ([double dagger]), J. H. HWANG ([double dagger]), W. J. CHOI ([section])

Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

* MD, PhD, Assistant Professor.

([dagger]) MD, PhD, Associate Professor.

([double dagger]) MD, PhD, Professor.

([section]) MD, PhD, Assistant Professor.

Address for correspondence: Assistant Professor W. J. Choi, Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Pungnap 2-dong, Songpa-gu, Seoul 138-736, Korea.

Accepted for publication on May 10, 2013.

Table 1
Patient characteristics

Number of patients   42
Age, y               62.8 [+ or -] 7.1
Weight, kg           70.9 [+ or -] 9.9
Height, cm           167.4 [+ or -] 6.6
Diabetes mellitus    4 (9.5%)
Hypertension         17 (40.5%)

Values are mean [+ or -] SD or number (percentage).

Table 2
Haemodynamic and respiratory variables before and after volume
loading in those patients assessed as responders vs non-responders
during pneumoperitoneum combined with the steep Trendelenburg
position

                                     Responders (n = 22)

                        Before VL           After VL            P

MABP, mmHg              85.0 [+ or -] 11.8  87.6 [+ or -] 10.6  0.148
HR, /min                60.0 [+ or -] 10.6  63.7 [+ or -] 11.4  0.004
Ppeak, cm[H.sub.2]O     27.8 [+ or -] 4.8   29.8 [+ or -] 4.9   <0.001
Pplat, cm[H.sub.2]O     27.2 [+ or -] 4.7   29.1 [+ or -] 4.8   <0.001
Cstat, ml/cm[H.sub.2]O  21.5 [+ or -] 3.2   20.0 [+ or -] 2.8   <0.001
ETC[O.sub.2], mmHg      31.1 [+ or -] 1.9   32.2 [+ or -] 2.2   0.002
SV-TOE, ml              54.1 [+ or -] 13.4  66.1 [+ or -] 15.4  <0.001
PPV (%)                 12.4 [+ or -] 4.2    7.3 [+ or -] 2.5   <0.001
SVV (%)                 12.9 [+ or -] 4.3    9.1 [+ or -] 3.6   <0.001

                                   Non-responders (n = 20)

                        Before VL           After VL            p

MABP, mmHg              90.2 [+ or -] 10.4  85.5 [+ or -] 11.4  0.105
HR, /min                60.2 [+ or -] 13.1  62.0 [+ or -] 11.9  0.164
Ppeak, cm[H.sub.2]O     28.4 [+ or -] 5.4   29.7 [+ or -] 5.4   <0.001
Pplat, cm[H.sub.2]O     27.8 [+ or -] 5.4   29.1 [+ or -] 5.3   <0.001
Cstat, ml/cm[H.sub.2]O  20.4 [+ or -] 2.7   19.4 [+ or -] 2.5   <0.001
ETC[O.sub.2], mmHg      31.9 [+ or -] 2.0   32.1 [+ or -] 2.2   0.592
SV-TOE, ml              60.3 [+ or -] 6.4   63.5 [+ or -] 7.6   0.007
PPV (%)                 7.0 (6.0-8.5)        5.0 (4.0-7.2)      0.003
SVV (%)                 9.0 [+ or -] 2.2     7.8 [+ or -] 2.5   0.041

Values are mean [+ or -] SD or median (interquartile range).
VL = volume loading, MABP = mean arterial blood pressure, HR = heart
rate, Ppeak = airway peak pressure, Pplat = airway plateau pressure,
Cstat = total static compliance of the respiratory system,
ETC[.sub.2] = end-tidal C[O.sub.2], SV-TOE = stroke volume measured
using transoesophageal echocardiography, PPV = pulse pressure
variation, SVV = stroke volume variation.

Table 3
Effect of position on haemodynamic and respiratory variables

                         [T.sub.S]           [T.sub.P]

MABP, mmHg               76.0 (69.3-82.7)    88.7 (81.2-105.9) *
HR, /min                 63.5 (54.2-79.7)    63.2 (56.9-76.3)
Ppeak, cm[H.sub.2]O      13.7 (11.8-15.8)    28.0 (23.7-30.2) *
Pplat, cm[H.sub.2]O      13.0 (11.0-15.0)    27.2 (23.4-30.0) *
Cstat, ml/cm[H.sub.2]O   42.5 (39.2-48.1)    20.9 (19.5-22.9) *
ETC[O.sub.2], mmHg       29.0 [+ or -] 2.0   28.9 [+ or -] 2.7
SV-TOE, ml               57.5 (51.8-64.5)    46.7 (38.5-53.2) *
PPV (%)                  9.0 (5.7-11.3)      16.0 (11.0-22.4) *
SVV (%)                  8.0 (6.5-9.3)       16.4 (11.5-21.4) *

                         [T.sub.P + T]

MABP, mmHg               86.7 (78.8-95.9) *
HR, /min                 57.3 (51.7-66.0) * ([dagger])
Ppeak, cm[H.sub.2]O      28.0 (23.0-30.7) *
Pplat, cm[H.sub.2]O      27.2 (23.0-30.7) *
Cstat, ml/cm[H.sub.2]O   20.7 (18.4-23.2) *
ETC[O.sub.2], mmHg       31.5 [+ or -] 2.0 * ([dagger])
SV-TOE, ml               55.2 (49.5-63.6) ([dagger])
PPV (%)                  8.9 (7.0-12.0)t
SVV (%)                  10.0 (8.0-13.0) * ([dagger])

Values are mean [+ or -] SD or median (interquartile range).
[T.sub.S] = after anaesthetic induction in supine position,
[T.sub.P] = three minutes after pneumoperitoneum during which time
insufflation pressure was set to 20 mmHg, [T.sub.P + T] = three
minutes after the steep Trendelenburg position (35[degrees]) was
added to pneumoperitoneum during which time insufflation pressure was
set to 15 mmHg, MABP = mean arterial blood pressure, HR = heart rate,
Ppeak = airway peak pressure, Pplat = airway plateau pressure,
Cstat = total static compliance of the respiratory system,
ETC[O.sub.2] = end-tidal C[O.sub.2], SV-TOE = stroke volume measured
using transoesophageal echocardiography, PPV = pulse pressure
variation, SVV = stroke volume variation. * P <0.05 vs [T.sub.S].
([dagger]) P <0.05 vs [T.sub.P].
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Title Annotation:Original Papers
Author:Chin, J.H.; Lee, E.H.; Hwang, G.S.; Hwang, J.H.; Choi, W.J.
Publication:Anaesthesia and Intensive Care
Article Type:Clinical report
Date:Jul 1, 2013
Words:5341
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