Changes In Pulse Pressure Variation Research Articles

Comparison Between Changes in Systolic-Pressure Variation and Pulse-Pressure Variation After Passive Leg Raising to Predict Fluid Responsiveness in Postoperative Critically Ill Patients

ObjectiveThe authors aimed to evaluate the precision of changes in systolic pressure variation after passive leg raising (PLR) as a predictor of fluid responsiveness in postoperative critically ill patients and to compare the precision of changes in pulse pressure variation after PLR (ΔPPVPLR) with changes in systolic pressure variation after PLR (ΔSPVPLR). DesignA prospective observational study. SettingA surgical intensive care unit of a tertiary hospital. Participants74 postoperative critically ill patients with acute circulatory failure were enrolled. InterventionsFluid responsiveness was defined as an increase of 10% or more in stroke volume after PLR, dividing patients into two groups: responders and nonresponders. Measurement and Main ResultsHemodynamic data were recorded at baseline and after PLR, and the stroke volume was measured by transthoracic echocardiography. 38 patients were responders, and 36 were nonresponders. ΔPPVPLR predicted fluid responsiveness with the areas under the receiver operating characteristic curves (AUC) of 0.917, and the optimal cut-off values were 2.3% with the grey zone of 1.6% to 3.3% including 19 (25.7%) patients. ΔSPVPLR predicted fluid responsiveness with the AUC of 0.908, and the optimal cut-off values were 1.9% with the grey zone of 1.1% to 2.0% including 18 (24.3%) patients. No notable distinction was observed between the AUC for ΔPPVPLR and ΔSPVPLR (p = 0.805) in predicting fluid responsiveness. ConclusionsΔSPVPLR and ΔPPVPLR could accurately predict fluid responsiveness in postoperative critically ill patients. There was no difference in the ability to predict fluid responsiveness between ΔSPVPLR and ΔPPVPLR.

Comparison of the carotid corrected flow time and tidal volume challenge for assessing fluid responsiveness in robot-assisted laparoscopic surgery.

We aimed to compare the ability of carotid corrected flow time assessed by ultrasound and the changes in dynamic preload indices induced by tidal volume challenge predicting fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. This prospective single-center study included patients undergoing robot-assisted laparoscopic surgery in the modified head-down lithotomy position. Carotid Doppler parameters and hemodynamic data, including corrected flow time, pulse pressure variation, stroke volume variation, and stroke volume index at a tidal volume of 6mL/kg predicted body weight and after increasing the tidal volume to 8mL/kg predicted body weight (tidal volume challenge), respectively, were measured. Fluid responsiveness was defined as a stroke volume index ≥ 10% increase after volume expansion. Among the 52 patients included, 26 were classified as fluid responders and 26 as non-responders based on the stroke volume index. The area under the receiver operating characteristic curve measured to predict the fluid responsiveness to corrected flow time and changes in pulse pressure variation (ΔPPV6-8) after tidal volume challenge were 0.82 [95% confidence interval (CI) 0.71-0.94; P < 0.0001] and 0.85 (95% CI 0.74-0.96; P < 0.0001), respectively. The value for pulse pressure variation at a tidal volume of 8mL/kg was0.79 (95% CI 0.67-0.91; P = 0.0003). The optimal cut-off values for corrected flow time and ΔPPV6-8 were 357ms and > 1%, respectively. Both the corrected flow time and Changes in pulse pressure variation after tidal volume challenge reliably predicted fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. And pulse pressure variation at a tidal volume of 8mL/kg maybe also a useful predictor.Trial registration: Chinese Clinical Trial Register (CHiCTR2200060573, Principal investigator: Hongliang Liu, Date of registration: 05/06/2022).

Passive leg raising-induced changes in pulse pressure variation to assess fluid responsiveness in mechanically ventilated patients: a multicentre prospective observational study

BackgroundPassive leg raising-induced changes in cardiac index can be used to predict fluid responsiveness. We investigated whether passive leg raising-induced changes in pulse pressure variation (ΔPPVPLR) can also predict fluid responsiveness in mechanically ventilated patients. MethodsIn this multicentre prospective observational study, we included 270 critically ill patients on mechanical ventilation in whom volume expansion was indicated because of acute circulatory failure. We did not include patients with cardiac arrythmias. Cardiac index and PPV were measured before/during a passive leg raising test and before/after volume expansion. A volume expansion-induced increase in cardiac index of >15% defined fluid responsiveness. To investigate whether ΔPPVPLR can predict fluid responsiveness, we determined areas under the receiver operating characteristic curves (AUROCs) and grey zones for relative and absolute ΔPPVPLR. ResultsOf the 270 patients, 238 (88%) were on controlled mechanical ventilation with no spontaneous breathing activity and 32 (12%) were on pressure support ventilation. The median tidal volume was 7.1 (inter-quartile range [IQR], 6.6–7.6) ml kg−1 ideal body weight. One hundred sixty-four patients (61%) were fluid responders. Relative and absolute ΔPPVPLR predicted fluid responsiveness with an AUROC of 0.92 (95% confidence interval [95% CI], 0.88–0.95; P<0.001) each. The grey zone for relative and absolute ΔPPVPLR included 4.8% and 22.6% of patients, respectively. These results were not affected by ventilatory mode and baseline characteristics (type of shock, centre, vasoactive treatment). ConclusionsPassive leg raising-induced changes in pulse pressure variation accurately predict fluid responsiveness with a small grey zone in critically ill patients on mechanical ventilation. Clinical trial registrationNCT 03225378.

Changes in pulse pressure variation to assess preload responsiveness in mechanically ventilated patients with spontaneous breathing activity: an observational study

BackgroundPulse pressure variation (PPV) is not reliable in predicting preload responsiveness in patients receiving mechanical with spontaneous breathing (SB) activity. We hypothesised that an increase in PPV after a tidal volume (VT) challenge (TVC) or a decrease in PPV during passive leg raising (PLR) can predict preload responsiveness in such cases. MethodsThis prospective observational study was performed in two ICUs and included patients receiving mechanical ventilation with SB, for whom the treating physician decided to test preload responsiveness. Transthoracic echocardiography was used to measure the velocity–time integral (VTI) of the left ventricular outflow tract. Patients exhibiting an increase in VTI ≥12% during PLR were defined as PLR+ patients (or preload responders). Then, a TVC was performed by increasing VT by 2 ml kg−1 predicted body weight (PBW) for 1 min. PPV was recorded at each step. ResultsFifty-four patients (Simplified Acute Physiology Score II: 60 (25) ventilated with a VT of 6.5 (0.8) ml kg−1 PBW, were included. Twenty-two patients were PLR+. The absolute decrease in PPV during PLR and the absolute increase in PPV during TVC discriminated between PLR+ and PLR– patients with area under the receiver operating characteristic (AUROC) curve of 0.78 and 0.73, respectively, and cut-off values of –1% and +2%, respectively. Those AUROC curve values were similar but were significantly different from that of baseline PPV (0.61). ConclusionIn patients undergoing mechanical ventilation with SB activity, PPV does not predict preload responsiveness. However, the decrease in PPV during PLR and the increase in PPV during a TVC help discriminate preload responders from non-responders with moderate accuracy. Clinical trial registrationNCT04369027 (ClinicalTrials.gov).

Do changes in pulse pressure variation and inferior vena cava distensibility during passive leg raising and tidal volume challenge detect preload responsiveness in case of low tidal volume ventilation?

BackgroundIn patients ventilated with tidal volume (Vt) < 8 mL/kg, pulse pressure variation (PPV) and, likely, the variation of distensibility of the inferior vena cava diameter (IVCDV) are unable to detect preload responsiveness. In this condition, passive leg raising (PLR) could be used, but it requires a measurement of cardiac output. The tidal volume (Vt) challenge (PPV changes induced by a 1-min increase in Vt from 6 to 8 mL/kg) is another alternative, but it requires an arterial line. We tested whether, in case of Vt = 6 mL/kg, the effects of PLR could be assessed through changes in PPV (ΔPPVPLR) or in IVCDV (ΔIVCDVPLR) rather than changes in cardiac output, and whether the effects of the Vt challenge could be assessed by changes in IVCDV (ΔIVCDVVt) rather than changes in PPV (ΔPPVVt).MethodsIn 30 critically ill patients without spontaneous breathing and cardiac arrhythmias, ventilated with Vt = 6 mL/kg, we measured cardiac index (CI) (PiCCO2), IVCDV and PPV before/during a PLR test and before/during a Vt challenge. A PLR-induced increase in CI ≥ 10% defined preload responsiveness.ResultsAt baseline, IVCDV was not different between preload responders (n = 15) and non-responders. Compared to non-responders, PPV and IVCDV decreased more during PLR (by − 38 ± 16% and − 26 ± 28%, respectively) and increased more during the Vt challenge (by 64 ± 42% and 91 ± 72%, respectively) in responders. ∆PPVPLR, expressed either as absolute or as percent relative changes, detected preload responsiveness (area under the receiver operating curve, AUROC: 0.98 ± 0.02 for both). ∆IVCDVPLR detected preload responsiveness only when expressed in absolute changes (AUROC: 0.76 ± 0.10), not in relative changes. ∆PPVVt, expressed as absolute or percent relative changes, detected preload responsiveness (AUROC: 0.98 ± 0.02 and 0.94 ± 0.04, respectively). This was also the case for ∆IVCDVVt, but the diagnostic threshold (1 point or 4%) was below the least significant change of IVCDV (9[3–18]%).ConclusionsDuring mechanical ventilation with Vt = 6 mL/kg, the effects of PLR can be assessed by changes in PPV. If IVCDV is used, it should be expressed in percent and not absolute changes. The effects of the Vt challenge can be assessed on PPV, but not on IVCDV, since the diagnostic threshold is too small compared to the reproducibility of this variable.Trial registration: Agence Nationale de Sécurité du Médicament et des Produits de santé: ID-RCB: 2016-A00893-48.

The influence of positive end-expiratory pressure (PEEP) in predicting fluid responsiveness in patients undergoing one-lung ventilation.

Background: Dynamic preload parameters such as pulse pressure variation (PPV) and stroke volume variation (SVV) have widely been used as accurate predictors for fluid responsiveness in patients under mechanical ventilation. To circumvent the limitation of decreased cyclic change of intrathoracic pressure, we performed an intermittent PEEP challenge test to evaluate whether PPV or SVV can predict fluid responsiveness during one-lung ventilation (OLV).Methods: Forty patients undergoing OLV were analyzed. Baseline hemodynamic variables including PPV and SVV and respiratory variables were recorded after chest opening in lateral position under OLV (T1). Five minutes after application of PEEP 10 cmH2O, the parameters were recorded (T2). Thereafter, PEEP was withdrawn to 0 cmH2O for 5 minutes (T3), and fluid loading was performed with balanced crystalloid solution 6 mL/kg of ideal body weight for 5 minutes. Five minutes after completion of fluid loading, all variables were recorded (T4). The patient was classified as fluid responder if SV increased ≥10% after fluid loading and as non-responder if SV increased <10%.Results: Prediction of fluid responsiveness was evaluated with area under the receiver operating characteristic (ROC) curve (AUC). Change in stroke volume variation (ΔSVV) showed AUC of 0.9 (P < 0.001), 95% CI = 0.82-0.99, sensitivity = 88%, specificity = 82% for discrimination of fluid responsiveness. Change in pulse pressure variation (ΔPPV) showed AUC of 0.88 (P < 0.001), 95% CI = 0.78-0.97, sensitivity = 83%, specificity = 72% in predictability of fluid responsiveness. Cardiac index and stroke volume were well maintained after PEEP challenge in non-responders while they increased in responders.Conclusions: ΔPPV and ΔSVV induced by PEEP challenge are reliable parameters to predict fluid responsiveness as well as very good predictors of fluid unresponsiveness during OLV.

Predicting Fluid Responsiveness Using Change in Pulse Pressure Variation and Stroke Volume Variation after Tidal Volume Challenge in Postoperative Patients Receiving Lung Protective Ventilation

Background: Lung protective ventilation with low tidal volume (VT) is beneficial in patients with intermediate to high risk of post-operative pulmonary complications. However, during low VT ventilation, pulse pressure variation (PPV) and stroke volume variation (SVV) do not predict fluid responsiveness. Objective: To determine whether changes in PPV and SVV after transient increases in VT could predict fluid responsiveness. Materials and Methods: The authors recorded 20 measurements from 15 patients experiencing post-operative acute circulatory failure. The authors performed a VT challenge by transient increasing VT from 6 to 8 mL/kg (VT₆-₈), 8 to 10 mL/kg (VT₈-₁₀), and 6 to 10 mL/kg (VT₆-₁₀) of patients’ predicted body weight. The change in PPV (∆PPV) at VT₆-₈ (∆PPV₆-₈), VT₈-₁₀ (∆PPV₈-₁₀), VT₆-₁₀ (∆PPV₆-₁₀), and the change in SVV (∆SVV) at VT₆-₈ (∆SVV₆-₈), VT₈-₁₀ (∆SVV₈-₁₀), and VT₆-₁₀ (∆SVV₆-₁₀) were recorded. Patients were classified as fluid responders if there was an increase in stroke volume of more than 10% after a fluid bolus. Results: Following the VT challenge, ∆PPV and ∆SVV failed to predict fluid responsiveness, with areas under the receiver operating characteristic curves (with 95% confidence intervals) of 0.49 (0.23 to 0.74), 0.54 (0.29 to 0.79), 0.52 (0.28 to 0.77) for ∆PPV₆-₈, ∆PPV₈-₁₀, and ∆PPV₆-₁₀, and 0.55 (0.30 to 0.80), 0.55 (0.31 to 0.80), and 0.59 (0.34 to 0.84) for ∆SVV₆-₈, ∆SVV₈-₁₀, and ∆SVV₆-₁₀, respectively. Conclusion: Changes in PPV and SVV after the VT challenge did not predict fluid responsiveness in post-operative patients with low VT ventilation. Trial registration: Thai Clinical Trials Registry, TCTR 20190808003 Keywords: Pulse pressure variation, Stroke volume variation, Fluid responsiveness, Tidal volume challenge

Parameters of fluid responsiveness.

On the basis of recent literature, we summarized the new advances on the use of available dynamic indices of fluid responsiveness. Reliability of passive leg raising to assess fluid responsiveness is well established provided that a real-time haemodynamic assessment is available. Recent studies have focused on totally noninvasive techniques to assess its haemodynamic effects with promising results. Presence of intra-abdominal hypertension is associated with false-negative cases of passive leg raising. Use of pulse pressure and stroke volume variations is limited and other heart-lung interaction tests have been developed. The tidal volume challenge may overcome the limitation of low tidal volume ventilation. Preliminary data suggest that changes in pulse pressure variation during this test well predict fluid responsiveness. Growing evidence confirms the good predictive performance of the end-expiratory occlusion test. All these dynamic tests allow selecting appropriate fluid responders and preventing excessive fluid administration. Performance of a mini-fluid challenge may help for the decision-making process of fluid management if other tests are not available. Several new dynamic variables and monitoring techniques to predict fluid responsiveness were investigated in the past years. Nevertheless, further research investigating their reliability and feasibility in larger cohorts is warranted. VIDEO ABSTRACT.

Change in cardiac output during Trendelenburg maneuver is a reliable predictor of fluid responsiveness in patients with acute respiratory distress syndrome\xa0in the prone position under protective ventilation

BackgroundPredicting fluid responsiveness may help to avoid unnecessary fluid administration during acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate the diagnostic performance of the following methods to predict fluid responsiveness in ARDS patients under protective ventilation in the prone position: cardiac index variation during a Trendelenburg maneuver, cardiac index variation during an end-expiratory occlusion test, and both pulse pressure variation and change in pulse pressure variation from baseline during a tidal volume challenge by increasing tidal volume (VT) to 8 ml.kg-1.MethodsThis study is a prospective single-center study, performed in a medical intensive care unit, on ARDS patients with acute circulatory failure in the prone position. Patients were studied at baseline, during a 1-min shift to the Trendelenburg position, during a 15-s end-expiratory occlusion, during a 1-min increase in VT to 8 ml.kg-1, and after fluid administration. Fluid responsiveness was deemed present if cardiac index assessed by transpulmonary thermodilution increased by at least 15% after fluid administration.ResultsThere were 33 patients included, among whom 14 (42%) exhibited cardiac arrhythmia at baseline and 15 (45%) were deemed fluid-responsive. The area under the receiver operating characteristic (ROC) curve of the pulse contour-derived cardiac index change during the Trendelenburg maneuver and the end-expiratory occlusion test were 0.90 (95% CI, 0.80–1.00) and 0.65 (95% CI, 0.46–0.84), respectively. An increase in cardiac index ≥ 8% during the Trendelenburg maneuver enabled diagnosis of fluid responsiveness with sensitivity of 87% (95% CI, 67–100), and specificity of 89% (95% CI, 72–100). The area under the ROC curve of pulse pressure variation and change in pulse pressure variation during the tidal volume challenge were 0.52 (95% CI, 0.24–0.80) and 0.59 (95% CI, 0.31–0.88), respectively.ConclusionsChange in cardiac index during a Trendelenburg maneuver is a reliable test to predict fluid responsiveness in ARDS patients in the prone position, while neither change in cardiac index during end-expiratory occlusion, nor pulse pressure variation during a VT challenge reached acceptable predictive performance to predict fluid responsiveness in this setting.Trial registrationClinicalTrials.gov, NCT01965574. Registered on 16 October 2013. The trial was registered 6 days after inclusion of the first patient.

The Changes in Pulse Pressure Variation or Stroke Volume Variation After a "Tidal Volume Challenge" Reliably Predict Fluid Responsiveness During Low Tidal Volume Ventilation.

Stroke volume variation and pulse pressure variation do not reliably predict fluid responsiveness during low tidal volume ventilation. We hypothesized that with transient increase in tidal volume from 6 to 8 mL/kg predicted body weight, that is, "tidal volume challenge," the changes in pulse pressure variation and stroke volume variation will predict fluid responsiveness. Prospective, single-arm study. Medical-surgical ICU in a university hospital. Adult patients with acute circulatory failure, having continuous cardiac output monitoring, and receiving controlled low tidal volume ventilation. The pulse pressure variation, stroke volume variation, and cardiac index were recorded at tidal volume 6 mL/kg predicted body weight and 1 minute after the "tidal volume challenge." The tidal volume was reduced back to 6 mL/kg predicted body weight, and a fluid bolus was given to identify fluid responders (increase in cardiac index > 15%). The end-expiratory occlusion test was performed at tidal volumes 6 and 8 mL/kg predicted body weight and after reducing tidal volume back to 6 mL/kg predicted body weight. Thirty measurements were obtained in 20 patients. The absolute change in pulse pressure variation and stroke volume variation after increasing tidal volume from 6 to 8 mL/kg predicted body weight predicted fluid responsiveness with areas under the receiver operating characteristic curves (with 95% CIs) being 0.99 (0.98-1.00) and 0.97 (0.92-1.00), respectively. The best cutoff values of the absolute change in pulse pressure variation and stroke volume variation after increasing tidal volume from 6 to 8 mL/kg predicted body weight were 3.5% and 2.5%, respectively. The pulse pressure variation, stroke volume variation, central venous pressure, and end-expiratory occlusion test obtained during tidal volume 6 mL/kg predicted body weight did not predict fluid responsiveness. The changes in pulse pressure variation or stroke volume variation obtained by transiently increasing tidal volume (tidal volume challenge) are superior to pulse pressure variation and stroke volume variation in predicting fluid responsiveness during low tidal volume ventilation.

Changes in pulse pressure variation and plethysmographic variability index caused by hypotension-inducing hemorrhage followed by volume replacement in isoflurane-anesthetized dogs.

To compare changes in pulse pressure variation (PPV) and plethysmographic variability index (PVI) induced by hemorrhage followed by volume replacement (VR) in isoflurane-anesthetized dogs. 7 healthy adult dogs. Each dog was anesthetized with isoflurane and mechanically ventilated. End-tidal isoflurane concentration was adjusted to maintain mean arterial pressure (MAP) at 60 to 70 mm Hg before hemorrhage. Controlled hemorrhage was initiated and continued until the MAP decreased to 40 to 50 mm Hg, then autologous blood removed during hemorrhage was retransfused during VR. Various physiologic variables including PPV and PVI were recorded immediately before (baseline) and after controlled hemorrhage and immediately after VR. Mean ± SD PPV and PVI were significantly increased from baseline after hemorrhage (PPV, 20 ± 6%; PVI, 18 ± 4%). After VR, the mean PPV (7 ± 3%) returned to a value similar to baseline, whereas the mean PVI (10 ± 3%) was significantly lower than that at baseline. Cardiac index (CI) and stroke index (SI) were significantly decreased from baseline after hemorrhage (CI, 2.07 ± 0.26 L/min/m(2); SI, 20 ± 3 mL/beat/m(2)) and returned to values similar to baseline after VR (CI, 4.25 ± 0.63 L/min/m(2); SI, 36 ± 6 mL/beat/m(2)). There was a significant positive correlation (r(2) = 0.77) between PPV and PVI after hemorrhage. Results suggested that both PPV and PVI may be useful for identification of dogs that respond to VR with increases in SI and CI (ie, dogs in the preload-dependent limb of the Frank-Starling curve).

Effects of dexmedetomidine on pulse pressure variation changes induced by hemorrhage followed by volume replacement in isoflurane-anesthetized dogs.

To evaluate the effects of dexmedetomidine (DEX) on changes in pulse pressure variation (PPV) induced by hemorrhage followed by volume replacement (VR) during isoflurane (ISO) anesthesia. Prospective, randomized, crossover study. Research laboratory at a veterinary teaching hospital. Eight adult dogs. Anesthesia was maintained with 1.3 times the minimum alveolar concentration (MAC) of ISO alone or ISO with DEX (ISO-DEX, 1.6 μg/kg [bolus], followed by 2 μg/kg/h). Atropine was administered 30 minutes prior to hemorrhage in the ISO-DEX treatment. Ventilation was controlled (tidal volume of 12 mL/kg, positive end-expiratory pressure of 7 cm H2 O, respiratory rate of 16-20/min) under neuromuscular blockade. After recording baseline data, progressive withdrawal of 10%, 20%, and 30% of blood volume (HV10 , HV20 , and HV30 , respectively [measurements during hemorrhage, indicating x% of blood volume removed]) was followed by VR with autologous blood. In 4 of 8 ISO dogs, hemorrhage decreased mean arterial pressure (MAP) < 60 mm Hg. Based on mean arterial pressure after hemorrhage, dogs were assigned to hypotensive (HG) and normotensive (NG) groups post hoc. During ISO, stroke index and cardiac index decreased with hemorrhage (P < 0.05), while VR normalized or increased these variables. The PPV (%, mean [range]) was increased by hemorrhage from 7 (5-9) to 20 (12-27) and 27 (17-40) at HV20 and HV30 , respectively, only in ISO dogs in the HG; PPV returned to baseline after VR. Dexmedetomidine caused increases in systemic vascular resistance (in dogs in HG and NG), and prevented the increase in PPV with hemorrhage. During ISO anesthesia, PPV increases in individuals prone to developing hypotension from hypovolemia. Because DEX prevents the increase in PPV associated with hypovolemia, PPV should not be used to guide VR in dogs that have been given DEX.

Can Changes in Arterial Pressure be Used to Detect Changes in Cardiac Output during Volume Expansion in the Perioperative Period?

Cardiac output (CO) is rarely monitored during surgery, and arterial pressure remains the only hemodynamic parameter for assessing the effects of volume expansion (VE). However, whether VE-induced changes in arterial pressure accurately reflect changes in CO has not been demonstrated. The authors studied the ability of VE-induced changes in arterial pressure and in pulse pressure variation to detect changes in CO induced by VE in the perioperative period. The authors studied 402 patients in four centers. Hemodynamic variables were recorded before and after VE. Response to VE was defined as more than 15% increase in CO. The ability of VE-induced changes in arterial pressure to detect changes in CO was assessed using a gray zone approach. VE increased CO of more than 15% in 205 patients (51%). Areas under the receiver operating characteristic curves for VE-induced changes in systolic, diastolic, means, and pulse pressure ranged between 0.64 and 0.70, and sensitivity and specificity ranged between 52 and 79%. For these four arterial pressure-derived parameters, large gray zones were found, and more than 60% of the patients lay within this inconclusive zone. A VE-induced decrease in pulse pressure variation of 3% or more allowed detecting a fluid-induced increase in CO of more than 15% with a sensitivity of 90% and a specificity of 77% and a gray zone between 2.2 and 4.7% decrease in pulse pressure variation including 14% of the patients. Only changes in pulse pressure variation accurately detect VE-induced changes in CO and have a potential clinical applicability.

Do We Need to Monitor Cardiac Output during Major Surgery?

Do We Need to Monitor Cardiac Output during Major Surgery?