Hemodynamics and oxygen transport dynamics during hepatic resection at different central venous pressures in a pig model

BACKGROUND

Although low central venous pressure (CVP) has been used to minimize blood loss during hepatectomy, the impact of variations of CVP on the rate of blood loss and on the perfusion of end-organs has not been evaluated. This animal study aimed to evaluate the hemodynamics and oxygen transport changes during hepatic resection at different CVP levels.

METHODS

Forty-eight anesthetized Bama miniature pigs were divided into 8 groups with CVP during hepatic resection controlled at 0 to <1, 1 to <2, 2 to <3, 3 to <4, 4 to <5, 5 to <6, 6 to <7, and 7 to <8 cmH2O. Intergroup comparisons were made for hemodynamic parameters, oxygen transport dynamics, and the rate of blood loss.

RESULTS

The rate of blood loss and the hepatic venous pressure during hepatic resection were almost linearly related to the CVP. A significant drop in the mean arterial pressure, cardiac output, and cardiac index occurred between CVP ≥2 and <2 cmH2O. Oxygen delivery (DO2), oxygen consumption (VO2) and oxygen extraction ratio (ERO2) remained relatively constant between CVPs of 2 to <8 cmH2O. There was a significant drop in DO2 when the CVP was <2 cmH2O. There was also a significant drop in VO2 and ExO2 when the CVP was <1 cmH2O.

CONCLUSION

The optimal CVP for hepatic resection is 2 to 3 cmH2O.

Comparison of central venous pressure and venous oxygen saturation from venous catheters placed in the superior vena cava or via a femoral vein: the numbers are not interchangeable

OBJECTIVE

To compare venous pressure and haemoglobin oxygen saturation measured from a catheter in the superior vena cava (SVC) with a catheter inserted via the femoral vein, and to assess the agreement of these measurements. To assess the effect of intra-abdominal pressure and intrathoracic pressures on these measurements.

DESIGN, SETTING AND PARTICIPANTS

Prospective study of patients in an adult intensive care unit, Alfred Hospital, Melbourne, Australia.

MAIN OUTCOME MEASURES

Central venous pressure (CVP), femoral venous pressure (FVP), venous haemoglobin oxygen saturation in the SVC (SO₂C) and via the femoral vein (SO₂F), agreement between these measures using the Bland-Altman method, and the effect of intra-abdominal pressure and intrathoracic pressure.

RESULTS

43 patients were included; the mean bias for FVP -CVP was 1.05 mmHg (95% CI, 0.30-1.79 mmHg), with limits of agreement of -3.79 to 5.89 mmHg (95% CI, -5.08 to 7.18 mmHg). The bias for SO₂F -SO₂C was -3.21 (95% CI, -6.33 to -0.10), with limits of agreement of -22.43 to 16.01 (95% CI, -27.81 to 21.39). Intra-abdominal pressure had a significant (P < 0.01) effect on both the FVP and on the difference (FVP -CVP).

CONCLUSIONS

This study demonstrates poor agreement between CVP and FVP and between SO₂C and SO₂F and that the measurements taken from these two sites are not interchangeable clinically.

[Intrathoracic blood volume index as an indicator of fluid management in septic shock]

OBJECTIVE

To investigate the value of intrathoracic blood volume index (ITBVI) monitoring in fluid management strategy in septic shock patients.

METHODS

In a prospective study, 33 patients who were diagnosed to be suffering from septic shock in the intensive care unit (ICU) were enrolled . Seventeen patients who received pulse indicator continuous cardiac output (PiCCO) monitoring, and ITBVI was used as indicator of fluid management, were enrolled into ITBVI group; 16 patients who received traditional fluid management strategy [directed by central venous pressure (CVP)] were enrolled into control group. Acute physiology and chronic health evaluation II (APACHEII) score, sepsis related organ failure assessment (SOFA) score and vasopressor score were compared between 1 day and 3 days of treatment. The characteristics of fluid management were recorded and compared within 72 hours.

RESULTS

(1)In 3 days of treatment, APACHEII, SOFA and vasopressor score were significantly lower in ITBVI group compared with that of in 1 day of treatment[21.3±6.2 vs. 25.4±7.2, 6.1±3.4 vs. 9.0±3.5, 5 (0, 8.0) vs. 20.0 (8.0, 35.0), respectively, all P<0.01], whereas there were no changes in control group. (2)Although fluid output (ml) was higher in ITBVI group during 48-72 hours period (2 421± 868 vs. 1 721±934, P=0.039), there was no difference in fluid intake, fluid output or fluid balance (ml) within 0-72 hours between two groups (fluid intake: 9 918±137 vs. 10 529±1 331, fluid output : 6 035±1 739 vs. 5 827±2 897, fluid balance: 3 882±1 889 vs. 4 703±2 813, allP>0.05). (3)Comparing the fluid volume (ml) used for fluid replacement period, except that there was no significance in fluid challenge with colloid during 0-6 hours between two groups [ml: 250 (125, 500) vs. 250 (69,250), P>0.05], more fluid intake (ml) was found in ITBVI group [0-6 hours crystalloid: 250(150,250) vs. 125 (105,125), 6-72 hours crystalloid: 125 (125, 250) vs. 100 (56, 125), 0-72 hours crystalloid: 250(125, 250) vs. 125 (75, 125), 6-72 hours colloid: 125 (106, 250) vs. 75 (50, 125), 0-72 hours colloid: 200 (125, 250) vs. 100 (50, 125),all P<0.01].

CONCLUSION

Clinical picture in patients with septic shock is improved after 3 days of treatment than 1 day of treatment under fluid management directed by ITBVI, compared with by CVP. This improvement may be attributable to accurate assessment of preload and appropriate infusion rate in fluid challenge.

[Effects of mechanical ventilation and positive end-expiratory on central venous pressure]

OBJECTIVE

To investigate the effects of mechanical ventilation and positive end expiratory pressure (PEEP) on central venous pressure (CVP).

METHODS

Forty cases of respiratory failure with mechanical ventilation were enrolled. Catheter was inserted via subclavian vein in each. And then CVP was measured without mechanical ventilation and under different PEEP conditions of 0, 6 and 12 cm H2O.

RESULTS

Mechanical ventilation could affect the levels of CVP, P(peak) ≈ PS+PEEP, followed PEEP, t = 3.364, P = 0.006. There was significant difference was found among the three groups, F = 15.293, P = 0.000. And CVP increased with a rising level of PEEP.

CONCLUSION

Mechanical ventilation and PEEP affect the accuracy of CVP.

[Assessment of cardiovascular preload and response to volume expansion]

Volume expansion is used in patients with hemodynamic insufficiency in an attempt to improve cardiac output. Finding criteria to predict fluid responsiveness would be helpful to guide resuscitation and to avoid excessive volume effects. Static and dynamic indicators have been described to predict fluid responsiveness under certain conditions. In this review we define preload and preload-responsiveness concepts. A description is made of the characteristics of each indicator in patients subjected to mechanical ventilation or with spontaneous breathing.

[Effects of central venous pressure on acute kidney injury in septic shock]

OBJECTIVE

To investigate the effects of central venous pressure on acute kidney injury (AKI) in septic shock.

METHODS

A total of 86 septic shock patients with PiCCO (pulse indicator continuous cardiac output) monitoring admitted at our department from January 2009 to January 2011 were retrospectively studied. They were divided into 2 groups based on central venous pressure (CVP) at 24 hs after PiCCO monitoring. There were 41 cases in low CVP group (CVP ≤ 10 mm Hg and 45 cases in high CVP group (CVP > 10 mm Hg). Their hemodynamic data, lactate concentration, ScvO₂ (central venous oxygen saturation), APACHEII (acute physiology & chronic health evaluation II) score and serum creatinine were obtained at the beginning and 24 hours after PiCCO monitoring. The incidence and mortality of AKI, the outcome of these patients in ICU and at Day 28 post-diagnosis were recorded.

RESULTS

(1) The incidences of AKI were 51.2% (21/41) and 75.6% (34/45) in low and high CVP groups respectively; (2) Nine cases (22.0%) died in ICU in low CVP group and 20 cases (44.4%) in high CVP group. And 12 cases (29.3%) died within 28 days in low CVP group while 21 cases (46.7%) in high CVP group.

CONCLUSION

A high CVP may increase the incidence and morbidity of AKI in septic shock. And an excessively high CVP should be prevented.

Central venous pressure and pulmonary capillary wedge pressure: fresh clinical perspectives from a new model of discordant and concordant heart failure

Heart-failure phenotypes include pulmonary and systemic venous congestion. Traditional heart-failure classification systems include the Forrester hemodynamic subsets, which use 2 indices: pulmonary capillary wedge pressure (PCWP) and cardiac index. We hypothesized that changes in PCWP and central venous pressure (CVP), and in the phenotypes of heart failure, might be better evaluated by cardiovascular modeling. Therefore, we developed a lumped-parameter cardiovascular model and analyzed forms of heart failure in which the right and left ventricles failed disproportionately (discordant ventricular failure) versus equally (concordant failure). At least 10 modeling analyses were carried out to the equilibrium state. Acute discordant pump failure was characterized by a "passive" volume movement, with fluid accumulation and pressure elevation in the circuit upstream of the failed pump. In biventricular failure, less volume was mobilized. These findings negate the prevalent teaching that pulmonary congestion in left ventricular failure results primarily from the "backing up" of elevated left ventricular filling pressure. They also reveal a limitation of the Forrester classification: that PCWP and cardiac index are not independent indices of circulation. Herein, we propose a system for classifying heart-failure phenotypes on the basis of discordant or concordant heart failure. A surrogate marker, PCWP-CVP separation, in a simplified situation without complex valvular or pulmonary disease, shows that discordant left and right ventricular failures are characterized by differences of ≥ 4 and ≤ 0 mmHg, respectively. We validated the proposed model and classification system by using published data on patients with acute and chronic heart failure.

Changes in intra-abdominal, iliac venous and central venous pressures in patients undergoing abdominal surgery due to large tumors of the colon--a pilot study

Changes in intra-abdominal pressure during bowel tumor surgery have not been documented. The purpose of the present study was to analyze changes in intra-abdominal pressure (IAP), central venous pressure (CVP) and iliac venous pressure (IVP) in patients undergoing laparotomy due to large tumor of the bowel. Twenty-one adult patients undergoing elective abdominal surgery were examined. Intra-abdominal pressure, CVP and IVP were measured during anesthesia, surgery and early postoperative period. The mean IAP before anesthesia was 12.76 +/- 1.09 mm Hg and mean bowel tumor volume 1550 +/- 227.48 mL. Anesthesia induction decreased IAP to 10.52 +/- 1.32 mm Hg and excision of intra-peritoneal tumors to 5.24 +/- 1.51 mm Hg (49.7%). Ten minutes after anesthesia, IAP increased to 7.47 +/- 1.2 mm Hg and one hour after surgery decreased to 6.19 +/- 1.43 mm Hg. There was a strong overall correlation between IAP and CVP (P = 0.0000; r = 0.7779), as well as between IAP and IVP (P = 0.0000; r = 0.8635). Moreover, IAP correlated with IVP immediately after anesthesia and one hour after anesthesia. In conclusion, induction of anesthesia decreased IAP; excision of large bowel tumors decreased IAP; and IAP strongly correlated with CVP and IVP.

[Prediction of fluid responsiveness by physiological variables]

OBJECTIVE

To investigate the clinical values of blood pressure, heart rate and central venous pressure before and after fluid challenge to predict volume responsiveness.

METHODS

A total of 86 fluid challenges in 39 patients with hemodynamic monitoring were retrospectively analyzed. Fluid challenges were separated into responder group and control group based on whether a 10% increase in cardiac output was achieved by fluid challenge. Such physiologic variables as systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), mean arterial pressure (MAP), heart rate (HR) and central venous pressure (CVP) were recorded before and after fluid challenges.

RESULTS

ΔSBP, ΔDBP, ΔPP and ΔMAP before and after fluid challenge were significantly higher in responder group than control group. Logistic regression analysis identified ΔPP as the only independent predictor of fluid responsiveness (OR 1.100, 95%CI 1.037 - 1.167). Fluid responsiveness was predicted by ΔPP ≥ 5 mm Hg with sensitivity 78.4%, specificity 75.7%, positive predict value 76.3% and negative predict value 77.8%. Only ΔPP correlated with ΔCO by Pearson correlation analysis (r = 0.417, P < 0.001).

CONCLUSION

ΔPP before and after fluid challenge can predict volume responsiveness while HR and CVP can not.

Central venous pressure during the post-anhepatic phase is not associated with early postoperative outcomes following orthotopic liver transplantation

BACKGROUND

Fluid management during orthotopic liver transplantation poses unique challenges for the anesthesiologist. Maintenance of hypovolemia as indicated by low central venous pressure has been associated with reduced blood loss and improved outcomes in some studies, but with higher 30-day mortality and increased incidence of renal dysfunction in others. The primary aim was to evaluate the association of central venous pressure management after liver allograft reperfusion with immediate postoperative patient outcomes.

METHODS

This was a retrospective investigation evaluating the intraoperative and postoperative records of 144 consecutive patients who underwent orthotopic liver transplantation at a single institution.

RESULTS

We did not find any important association between central venous pressure management after graft reperfusion and postoperative patient outcomes. Specifically, these data do not support the hypothesis that maintenance of lower central venous pressure during the post-anhepatic phase of orthotopic liver transplantation is associated with improved immediate postoperative allograft function (except for a steeper decrease in post operative days 1-3 in 2 of the 3 liver function test: alanine aminotransferase and bilirubin) or overall patient survival, graft survival, composite graft/patient survival, intensive care length of stay, hospital length of stay or the occurrence of infections.

CONCLUSION

Maintaining a lower central venous pressure during the post-anhepatic phase during orthotopic liver transplantation is not associated with any benefit in terms of immediate postoperative allograft function, graft survival or patient survival.

[Stroke volume variation in the evaluation of fluid responsiveness in refractory septic shock]

OBJECTIVE

To evaluate fluid responsiveness by stroke volume variation(SVV) in mechanically ventilated patients with refractory septic shock.

METHODS

Forty-two refractory septic shock patients were enrolled in the study. According to the responsiveness of fluid loading, the patients were divided into responsive group and non-responsive group. The SVV values of two groups were retrospectively analyzed. The receiver operating characteristic curve was drafted to determine the cut-off value of SVV for predicting fluid responsiveness.

RESULTS

Among the 42 refractory septic shock patients, 24 were found responsive to fluid loading, 18 were not; before the fluid loading, central venous pressure, heart rate, mean arterial pressure and global end-diastolic volume index in the both groups showed no significant differences whereas the SVV in the responsive group was much higher than that in the nonresponsive group (P=0.006). Using SVV≥12% as the threshold to predict fluid responsiveness, the sensitivity was 77%, specificity was 85%.

CONCLUSION

SVV can accurately predict fluid responsiveness in refractory septic shock patients.

[Accuracy of perioperative cardiac preload monitoring by global end-diastolic volume and intrathoracic blood volume in orthotopic liver transplantation]

OBJECTIVE

To investigate the clinical value of global end-diastolic volume (GEDV) and intrathoracic blood volume (ITBV) in perioperative monitoring of the cardiac preload in patients undergoing orthotopic liver transplantations (OLT).

METHODS

Eight ASA III or IV patients aged 42-50 years undergoing OLT without venovenous bypass under general anesthesia were enrolled in this study. Before the induction, a thermodilution femoral artery catheter was inserted into the femoral artery under local anesthesia and connected to a PiCCOplus system to monitor ITBV and GEDV. A CCO catheter was inserted into the right internal jugular vein to monitor the pulmonary artery obstruction pressure (PAOP), central venous press (CVP) and stroke volume (SVPAC). Anesthesia was induced with a combination of midazolam (0.1 mg/kg), propofol (1 mg/kg) and fentanyl (3 microg/kg). Pipecuronium (0.1 mg/kg) was given to facilitate naso-endotracheal intubation. Before anesthesia (T0) and at 10 min before the anhepatic phase (T1), 10 min after anhepatic phase (T2), 10 min after neohepatic phase (T3) and at the end of surgery (T4), all the TPTD and CCO parameters were measured by injecting 10 ml cold saline solution (below 8 degrees celsius;) via the distal port of the central venous catheter.

RESULTS

ITBV and GEDV at T2 were significantly lower than those at T0, T1, T3 and T4 (P<0.05). SVPAC at T2 was dramatically decreased compared with that at T0 and T1 (P<0.05). The changes in the pressure preload parameters of the pulmonary artery catheter (PAOP and CVP) did not correlate to the changes in SVPAC, whereas the changes in the volume preload parameters (ITBV and GEDV) of the TPTD was significantly correlated to the changes in SVPAC (P<0.01). PAOP and CVP did not correlate to the changes in ITBV and GEDV.

CONCLUSION

ITBV and GEDV are more reliable than PAOP and CVP in perioperative monitoring of the cardiac preload in patients undergoing OLT.

Arterial base deficit in pulmonary embolism is an index of severity and diagnostic delay

In acute pulmonary embolism, patients free from circulatory failure usually present a blood gas pattern consistent with respiratory alkalosis. We investigated whether the appearance of arterial base deficit in these patients indicates disease severity and diagnostic delay. Twenty-four consecutive patients with pulmonary embolism were retrospectively evaluated. Twelve patients had arterial base excess > or =0 mmol/L (Group 1), and 12 patients arterial base deficit <0 mmol/L (Group 2). No patient showed signs of circulatory failure. Group 1 was characterized by a mean base excess of 2.2 +/- 1.7 mmol/L, while in Group 2, the mean base deficit was -1.9 +/- 0.7 mmol/L (p < 0.0001). At 1 week since the embolism, 11 patients of Group 1 and 6 of Group 2 received a PE diagnosis (p < 0.05). The vascular obstruction index was more severe in Group 2 than in Group 1 (48 +/- 12 vs. 36 +/- 17%, respectively, p < 0.05). In Group 2, the PaCO(2) was lower (33 +/- 3 vs. 36 +/- 5 mmHg, respectively, p < 0.05), the arterial pH was decreased (7.442 +/- 0.035 vs. 7.472 +/- 0.050, respectively, p = 0.097), the Pv(50) was lower (28.3 +/- 1.7 vs. 29.8 +/- 1.6 mmHg, respectively, p < 0.05), the aHCO(3) (-) was lower (22.5 +/- 0.7 vs. 26.1 +/- 1.6 mmol/L, respectively; p < 0.0001), while between the Groups, O(2) delivery, O(2) mixed venous saturation, and O(2) extraction ratio were equivalent. Despite no signs of circulatory failure, an arterial Base deficit develops in patients with respiratory alkalosis subsequent to more severe pulmonary vascular obstruction. Diagnostic delay favors a base deficit. Depending on the degree of hypocapnia, there may be limitation of peripheral O(2) uptake despite adequate O(2) availability. Progressive bicarbonate deficit suggests an increased risk for underlying conditions such as cardio-respiratory disorders or cancer, and requires close control and treatment.

Global and right ventricular end-diastolic volumes correlate better with preload after correction for ejection fraction

BACKGROUND

Volumetric monitoring with right ventricular end-diastolic volume indexed (RVEDVi) and global end-diastolic volume indexed (GEDVi) is increasingly being suggested as a superior preload indicator compared with the filling pressures central venous pressure (CVP) or the pulmonary capillary wedge pressure (PCWP). However, static monitoring of these volumetric parameters has not consistently been shown to be able to predict changes in cardiac index (CI). The aim of this study was to evaluate whether a correction of RVEDVi and GEDVi with a measure of the individual contractile reserve, assessed by right ventricular ejection fraction (RVEF) and global ejection fraction, improves the ability of RVEDVi and GEDVi to monitor changes in preload over time in critically ill patients.

METHODS

Hemodynamic measurements, both by pulmonary artery and by transcardiopulmonary thermodilution, were performed in 11 mechanically ventilated medical ICU patients. Correction of volumes was achieved by normalization to EF deviation from normal EF values in an exponential fashion. Data before and after fluid administration were obtained in eight patients, while data before and after diuretics were obtained in seven patients.

RESULTS

No correlation was found between the change in cardiac filling pressures (DeltaCVP, DeltaPCWP) and DeltaCI (R(2) 0.01 and 0.00, respectively). Further, no correlation was found between DeltaRVEDVi or DeltaGEDVi and DeltaCI (R(2) 0.10 and 0.13, respectively). In contrast, a significant correlation was found between DeltaRVEDVi corrected to RVEF (DeltacRVEDVi) and DeltaCI (R(2) 0.64), as well as between DeltacGEDVi and DeltaCI (R(2) 0.59). An increase in the net fluid balance with +844 + or - 495 ml/m(2) resulted in a significant increase in CI of 0.5 + or - 0.3 l/min/m(2); however, only DeltacRVEDVi (R(2) 0.58) and DeltacGEDVi (R(2) 0.36) correlated significantly with DeltaCI. Administration of diuretics resulting in a net fluid balance of -942 + or - 658 ml/m(2) caused a significant decrease in CI with 0.7 + or - 0.5 l/min/m(2); however, only DeltacRVEDVi (R(2) 0.80) and DeltacGEDVi (R(2) 0.61) correlated significantly with DeltaCI.

CONCLUSION

Correction of volumetric preload parameters by measures of ejection fraction improved the ability of these parameters to assess changes in preload over time in this heterogeneous group of critically ill patients.

Detection of elevated right atrial pressure using a simple bedside ultrasound measure

AIMS

Accurate assessment of right atrial pressure (RAP) often requires invasive measurement. With normal RAP, Valsalva increases right internal jugular vein (RIJV) cross sectional area (CSA) 20% to 30%. With high RAP, when venous compliance is low, we hypothesized that the increase in CSA would be blunted and could be detected non-invasively with bedside ultrasound.

METHODS AND RESULTS

RIJV ultrasound images were obtained in 67 patients undergoing right heart catheterization. The median RAP at end-expiration was 7 mm Hg (interquartile range [IQR] 5-9 mm Hg) in patients with normal RAP (n = 47) versus 15 mm Hg (IQR 12-22 mm Hg) in patients with elevated RAP (n = 20). With Valsalva, the median percent change in RIJV CSA was 35% (IQR 19%-79%) versus 5% (IQR 3%-14%) for normal and high RAP, respectively. By receiver operating curve analysis, a <17% increase in RIJV CSA with Valsalva predicted elevated RAP (> or =12 mmHg) with 90% sensitivity, 74% specificity, 94% negative predictive value, and 60% positive predictive value (area under the curve 0.86, P < .001).

CONCLUSIONS

An increase in RIJV CSA >17% during Valsalva effectively rules out elevated RAP. This simple bedside technique may be useful to assess central venous pressure and reduce the need for invasive pressure measurement.

Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial

CONTEXT

Goal-directed resuscitation for severe sepsis and septic shock has been reported to reduce mortality when applied in the emergency department.

OBJECTIVE

To test the hypothesis of noninferiority between lactate clearance and central venous oxygen saturation (ScvO2) as goals of early sepsis resuscitation.

DESIGN, SETTING, AND PATIENTS

Multicenter randomized, noninferiority trial involving patients with severe sepsis and evidence of hypoperfusion or septic shock who were admitted to the emergency department from January 2007 to January 2009 at 1 of 3 participating US urban hospitals.

INTERVENTIONS

We randomly assigned patients to 1 of 2 resuscitation protocols. The ScvO2 group was resuscitated to normalize central venous pressure, mean arterial pressure, and ScvO2 of at least 70%; and the lactate clearance group was resuscitated to normalize central venous pressure, mean arterial pressure, and lactate clearance of at least 10%. The study protocol was continued until all goals were achieved or for up to 6 hours. Clinicians who subsequently assumed the care of the patients were blinded to the treatment assignment.

MAIN OUTCOME MEASURE

The primary outcome was absolute in-hospital mortality rate; the noninferiority threshold was set at Delta equal to -10%.

RESULTS

Of the 300 patients enrolled, 150 were assigned to each group and patients were well matched by demographic, comorbidities, and physiological features. There were no differences in treatments administered during the initial 72 hours of hospitalization. Thirty-four patients (23%) in the ScvO2 group died while in the hospital (95% confidence interval [CI], 17%-30%) compared with 25 (17%; 95% CI, 11%-24%) in the lactate clearance group. This observed difference between mortality rates did not reach the predefined -10% threshold (intent-to-treat analysis: 95% CI for the 6% difference, -3% to 15%). There were no differences in treatment-related adverse events between the groups.

CONCLUSION

Among patients with septic shock who were treated to normalize central venous and mean arterial pressure, additional management to normalize lactate clearance compared with management to normalize ScvO2 did not result in significantly different in-hospital mortality.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00372502.

[Effects of irrigating fluid absorption in percutaneous nephrolithotripsy]

OBJECTIVE

To determine the hemodynamic status, fluid-electrolyte changes and complications associated with irrigation time in percutaneous nephrolithotripsy.

METHODS

A total of 68 renal calculi patients (31 males and 37 females) were recruited. The lateral recumbent percutaneous nephrolithotripsy was operated with Ho laser under ultrasonic guidance. 0.9% NaCI was used as perfusion fluid. The following items were recorded: mean arterial blood pressure (MAP), heart rate, central venous pressure (CVP), hemoglobin, sodium, potassium and chloride; perfusion time during operation; peri-operative and post-operative complications.

RESULTS

(1) Peri-operative and post-operative conditions: the average operative time was 83.1 +/- 22.21 minutes. Two cases stopped because of bleeding after puncture and the tube of stoma was placed for stone clearance of the second time. There was more bleeding in 11 patients, but the operations were continued with blood transfusion and close monitoring. Two operations ceased because of a premunition of congestive heart failure. Nine patients needed post-operative blood transfusion and 18 had a post-operative fever. One patient bled in and around the tube and had a peri-renal infection a week later. (2) Changes of observation parameters: there was no significant difference in CVP, heart rate, hemoglobin, sodium, potassium and chloride (P > 0.05). The post-perfusion value of MAP increased (P < 0.05) especially in the cases of more bleeding and long time of irrigation. Peri-operative and post-operative injection of furosemide could reduce the CVP value. The average irrigation time in the fever group was longer than the non-fever group (P < 0.05) and the CVP value of the fever group was higher than the non-fever group (P < 0.05).

CONCLUSION

Low pressure and short time of perfusion are safe in clinical practice. Congestive heart failure after the perfusion and the occurrence of post-operative infections are difficult to avoid when there are a long time of irrigation and more bleeding during operation.

[Perspectives of Sugiura operation by portal hypertension in children]

23 children, aged 3-17 years, have undergone the Sugiura operation since 1989. 18 children had extrahepatic portal hypertension, 3 - the inborn liver fibrosis, 2 - liver cirrhosis. The procedure has been complemented by endoscopic sclerotherapy since 2001. Of 13 children, who had just Sugiura operation, bleeding relapsed in 4 cases. Of 10 patients, who had the combined procedure, the recurrent bleeding was registered in 2 cases. The Sugiura operation in combination with endoscopic varices sclerotherapy was suggested as a method of choice in children with contraindications to portosystemic bypass procedure.

Damage control: cavoatrial anastomosis during a catastrophic right intrapericardial pneumonectomy

While undergoing an intrapericardial pneumonectomy for a massive right pulmonary inflammatory pseudotumor that had invaded the mediastinum, an 18-year-old woman experienced a nearly fatal iatrogenic complication. Dense scarring adjacent to the pseudotumor had drawn in the superior vena cava posterolaterally and fused the right main pulmonary artery to the right superior pulmonary vein within the pericardium. The failure of a linear stapler to secure the pulmonary vessels led to torrential hemorrhage. Attempts to control the bleeding resulted in inadvertent superior vena cava occlusion and central venous pressure elevation. Because cardiopulmonary bypass might not have been reliably established in time to avoid irreversible cerebral ischemia, we borrowed a technique from congenital heart surgery and rapidly fashioned a cavoatrial connection. The patient survived the operation without negative neurologic or cardiac sequelae, recovered fully, and had no recurrence of the pseudotumor. Herein, we describe the intraoperative decisions that were made under intense time pressure to avert catastrophe.

The influence of thoracic epidural anesthesia on liver hemodynamics in patients under general anesthesia

BACKGROUND AND OBJECTIVE

Hepatic hypoperfusion is regarded as an important factor in the pathophysiology of perioperative liver injury. Although thoracic epidural anesthesia is a widely used technique, limited data are available about the effects on hepatic blood flow with blockade restricted to thoracic segments in humans. The main objective of the present study was to investigate the effects of thoracic epidural anesthesia on hepatic blood flow under general anesthesia in humans.

MATERIAL AND METHODS

In 40 patients under general anesthesia, we assessed hepatic blood flow using plasma disappearance rate of indocyanine green (PDRICG) as a simple noninvasive method before and after induction of thoracic epidural anesthesia. The epidural catheter was inserted at the Th7/8 or Th8/9, and 1% lidocaine at a mean (range) dose of 8 (6-10) mL was injected. Ephedrine bolus was given to patients who demonstrated a decrease in mean arterial blood pressure below 60 mm Hg after induction of thoracic epidural anesthesia (TEA-E group). Other patients did not receive any catecholamines during the study period (TEA group). Ten patients who did not undergo TEA served as controls (control group).

RESULTS

In 7 patients, administration of ephedrine was necessary to avoid a decrease in mean arterial blood pressure below 60 mm Hg. Thus, the TEA-E group consisted of 7 patients and TEA group of 33. In the TEA group, thoracic epidural anesthesia was associated with a mean 2.3% min(-1) decrease in PDRICG (P<0.05). In the TEA-E group, all seven patients showed a 2.2% min(-1) decrease in PDRICG (P<0.05). Patients in the control group showed a mean 1.1% min(-1) increase in PDRICG (P<0.05). In contrast to hepatic blood flow, cardiac output was not affected by thoracic epidural anesthesia.

CONCLUSIONS

In humans, thoracic epidural anesthesia is associated with a decrease in hepatic blood flow. Thoracic epidural anesthesia combined with ephedrine bolus was found to result in further decrease in hepatic blood flow.

Effects of airway pressure release ventilation on blood pressure and urine output in children

OBJECTIVE

Increased intrathoracic pressures during airway pressure release ventilation (APRV) may compromise systemic venous return resulting in decreased cardiac output and renal perfusion. We sought to study the short-term effect of APRV on blood pressure (BP) and urine output (UO) in children with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS).

DESIGN

Retrospective cohort study.

PATIENTS

All patients with ALI/ARDS who were admitted to our Pediatric Intensive Care Unit (PICU) between 1/00 and 06/04, and who were ventilated with APRV (for at least 12 hr) for worsening oxygenation while on conventional ventilation (CV).

MEASUREMENTS AND RESULTS

Medical records were reviewed for patients' demographics, Pediatric Risk of Mortality (PRISM III) score, admitting diagnosis, ventilator settings, gas exchange data, heart rate (HR), central venous pressure (CVP), blood pressure (BP), UO, and use of other therapies [sedatives, pressors, inotropes, and intravenous fluid (IVF)]. Eleven patients met our inclusion and exclusion criteria with a mean age of 6.2 +/- 4.8 years (range: 1-15 years), a weight of 35.5 +/- 29.5 kg (range: 12-90 kg), and a PRISM score of 18.4 +/- 9.6 (range: 2-36). Within 10 hrs of APRV, patients' mean airway pressure (Paw) increased from 16.1 +/- 6.6 to 21.1 +/- 5.5 cm of H(2)O (P = 0.04). Despite a higher Paw there were no differences in HR, CVP, BP, UO, IVF and use of other therapies while on CV or APRV (P > 0.10).

CONCLUSION

In children with ALI/ARDS, despite a higher Paw, APRV does not affect BP or UO.

Eisenmenger's syndrome in pregnancy: use of Proseal laryngeal mask airway (PLMA) and epidural analgesia for elective cesarean section

We describe the successful anesthetic management of cesarean section in a patient with Eisenmenger's syndrome secondary to an atrial septal defect. Although conception is discouraged in women with Eisenmenger's syndrome, in inevitable circumstances, careful and meticulous planning of anesthesia can help the parturient survive the ordeal of a cesarean section. The cardiac output must be maintained and systemic vascular resistance must not be allowed to fall. This should ensure that there is minimal change in the right to left shunt. In our patient, the scenario of Eisenmenger's syndrome was complicated by biventricular hypertrophy. We achieved the goals in our patient by using general anesthesia with the Proseal laryngeal mask airway, a combination of ketamine and propofol, and epidural analgesia.

[Effect of positive end-expiratory pressure on the pressure gradient of venous return in hypovolemic patients under mechanical ventilation]

OBJECTIVE

To assess the effects of positive end-expiratory pressure (PEEP) on central venous pressure (CVP) and common iliac venous pressure (CIVP), and the difference between CVP and CIVP [D(c-i)VP] in hypovolemic patients under mechanical ventilation.

METHODS

From May 2007 to May 2009, 30 acute hypovolemic adult patients undergoing mechanical ventilation in intensive care unit (ICU) were enrolled. The patients were randomly divided into three groups, and PEEP with 0, 5, 10 cm H(2)O (1 cm H(2)O=0.098 kPa) levels were used respectively. Ten mechanically ventilated patients with similar basic clinical conditions but normal blood volume were selected randomly as the control group. CVP, CIVP and D(c-i)VP were measured and recorded at each PEEP level in both groups. The patients' heart rate, mean artery pressure and respiratory pressure data were also collected. The correlation analysis was used to analyze relationship between CVP and CIVP and between the changes in venous pressure and the changes in respiratory pressure.

RESULTS

(1)CVP increased significantly when PEEP level was elevated in the study group. When PEEP was 0, 5 and 10 cm H(2)O, the CVP was (1.3+/-0.9), (3.1+/-1.3) and (4.5+/-1.3) mm Hg, respectively (1 mm Hg=0.133 kPa, all P<0.01). Whereas, in the control group, the changes in CVP was small. At 0, 5 and 10 cm H(2)O PEEP levels, CVP was (6.9+/-1.3), (7.2+/-1.2) and (8.0+/-1.5) mm Hg, respectively, but when CVP at PEEP0 and PEEP5 was compared with that of PEEP10, the difference was significant (P<0.01 and P<0.05). There was slight increase of CIVP in both groups when PEEP was elevated. D(c-i)VP was increased significantly in the study group compared with control group (all P<0.01). But the value was gradually decreased when with elevation of PEEP. When PEEP level was elevated from 0 to 10 cm H(2)O, D(c-i)VP value was lowered from (4.9+/-1.7) mm Hg to (2.8+/-1.4) mm Hg. No significant difference in D(c-i)VP was found in the control group. The D(c-i)VP values in the control group were equal or lower than 1.5 mm Hg at three PEEP levels. (2)No relationship was found between CVP and CIVP at each PEEP level in the study group (r(1)=0.236, r(2)=0.299, r(3)=0.262, all P>0.05), but there was a statistically significant correlation between CVP and CIVP in the control group (r(1)=0.485, r(2)=0.679, r(3)=0.748, all P<0.05).

CONCLUSION

The findings suggest that it may not be appropriate to use CVP or CIVP to evaluate the patients' blood volume and effect of volume resuscitation in the hypovolemic patients undergoing mechanical ventilation in combination with PEEP.

Hemodynamic measurement in the operating room: a review of conventional measures to identify hypovolemia

Direct measurement of physiologic systems is often impractical. To overcome these obstacles, indirect physiologic measures have been developed. Indirect physiologic measures such as heart rate, blood pressure, and many others are surrogates that are believed to accurately represent the function of a physiologic system. Although a powerful tool, physiologic measurement has several potential limitations and errors. This can result in erroneous instrument data. For that reason, it is the responsibility of the clinician to question and interpret monitor output and to ultimately correctly assess validity of the measurement. This article reviews commonly used intraoperative monitoring techniques and discusses their potential limitations as they relate to hypovolemia and hemorrhagic shock.

Circulation and invasive monitoring: back to basics

Introduction

The monitoring of patients within the perioperative environment has become increasingly sophisticated as technological advances are made within anaesthesia and anaesthetic technique. The contemporary anaesthetic practitioner (AP) is required to prepare an ever mounting array of complex monitoring equipment within their daily routine. For clarification, in this article the abbreviation AP will refer to a nurse or operating department practitioner who is performing the anaesthetic assistant role, not to a physicians' assistant (anaesthesia) (AAGBI 2008).

Use of ventricular assist device as a bridge to cardiac transplantation: impact of age and other determinants on outcomes

We sought to compare outcomes in patients > or = 60 years of age with those of their younger counterparts who underwent ventricular assist device implantation intended as a bridge to cardiac transplantation and also to identify retrospectively additional pre- and postoperative factors that might portend adverse outcomes.The medical records of 88 patients who were treated with bridge-to-transplantation ventricular assist devices from 1996 through 2007 were reviewed. Laboratory values, hemodynamic parameters, and the need for hemodynamic support were evaluated. Postoperative complications and bridge-to-transplantation success rates versus death rates were evaluated. Seventeen patients were > or = 60 years old and 71 patients were < 60 years old. In the older group, 59% of patients underwent successful bridging to transplantation, compared with 69% of the younger patients (P = 0.41). Multivariate analysis distinguished age > or = 60, female sex, earlier time period of operation, higher mean pulmonary arterial and central venous pressures, need for preoperative intra-aortic balloon pumps, and postoperative respiratory failure as independent risk factors for death. After orthotopic heart transplantation, survival to hospital discharge was 100% in the older group and 93.9% in the younger patients. Median lengths of stay were similar in both age categories.Multivariate analysis identified age as 1 of 6 independent risk factors for death in this study. Patients who successfully underwent cardiac transplantation, however, had similar survival statistics regardless of age category. Case-by-case evaluation is warranted when analyzing risk-benefit ratios of bridge-to-transplantation ventricular assist device therapy in the older patient population.

[Central venous pressure, rewarming time, and total fluid replacement volume are predictors of mortality and complications after cardiac surgery]

OBJECTIVE

To analyze the influence of early (first day) postoperative factors on postoperative course in patients who have undergone heart surgery.

PATIENTS AND METHODS

A cross-sectional study of consecutively enrolled heart surgery patients was designed. We recorded central venous pressure, time required for rewarming to a core temperature of 35.5degrees C, and total fluids administered in 24 hours. We then analyzed their influence on mortality and cardiac, pulmonary, and renal complications.

RESULTS

Two hundred thirty-six patients were included. Central venous pressure over 18 mm Hg, time to rewarming over 6 hours, and administration of more than 5 L of fluids in the first 24 hours were factors associated with increased mortality and the development of cardiovascular, pulmonary, and renal complications.

CONCLUSIONS

Central venous pressure, rewarming time, and fluid replacement volume required on the first day are predictors of postoperative course.

[The role of central venous pressure to evaluate volume responsiveness in septic shock patients]

OBJECTIVE

To investigate the clinical role of central venous pressure (CVP) to evaluate fluid responsiveness in septic shock patients.

METHODS

66 septic shock patients were studied, every patient was administered a volume challenge, before and after it, CVP, intrathoracic blood volume index (ITBVI), global end-diastolic volume index (GEDVI), cardiac index (CI), stroke volume index (SVI) were measured by PiCCO method. All the obtained values were analyzed by statistics method.

RESULTS

Initial CVP in responders is significantly different from that in nonresponders; DeltaITBVI, DeltaGEDVI, DeltaCI, DeltaSVI, DeltaHR (Delta:changes) before and after volume challenge in responders were significantly different from those in nonresponders; the significance of DeltaITBVI, DeltaGEDVI to predict volume responsiveness was strong indicated by high values of areas under the receiver operating characteristic curves (0.674 and 0.700, respectively). If patients were regrouped by CVP <or= 11 mm Hg (1 mm Hg = 0.133 kPa) and CVP > 11 mm Hg, initial ITBVI and GEDVI in responders were not significantly different from that in nonresponders; DeltaITBVI, DeltaGEDVI, DeltaCI, DeltaSVI before and after volume challenge in responders were significantly different from those in nonresponders.

CONCLUSION

In septic shock patients, CVP play a guidance role to predict and evaluate volume responsiveness and when CVP was > 11 mm Hg, a positive response will be less likely. Initial volumetric parameters (intrathoracic blood volume and global end-diastolic volume) play a questionable role in predicting and evaluating volume responsiveness, changes before and after volume challenge maybe helpful.

Hypertonic saline 5% vs. lactated ringer for resuscitating patients in hemorrhagic shock

BACKGROUND

Though hypertonic and isotonic crystalloids are used nowadays in resuscitating patients in hemorrhagic shock, yet there is no sufficient data in support of either. The aim of this study was to compare the hemodynamic effects of hypertonic saline 5% and lactated ringer solutions when used for the resuscitation of patients in hemorrhagic shock.

METHODS

In a double-blinded randomized clinical trial, sixty adult patients in hemorrhagic shock admitted to the Emergency Department of a teaching hospital between September 2005 and September 2006, were enrolled in this study. Patients were divided into two groups. The first group received lactated ringer 20 ml/kg, and the second group received 4 ml/kg of 5% hypertonic saline infused intravenously within 10 to 15 minutes followed by lactated ringer 10 ml/kg/hr. Hemodynamic parameters were measured at hospital admission as well as every 15 minutes for an hour; and the results were compared between the two groups.

RESULTS

Gastrointestinal bleeding was the most common cause of shock. There was a significant difference between the baseline and final hemodynamic parameters (MAP, HR, CVP) in each group; however, data of the two groups did not differ significantly. The PaO2 was higher in the lactated ringer group and there was no difference in PaCO2 neither in each group, nor between the two groups.

CONCLUSION

Both hyper and isotonic crystalloid solutions can improve hemodynamic status and the blood gas measurements, similarly; however, lactated ringer is a more potent solution in improving tissue oxygenation.

Influence of angiotensin-I-converting-enzyme insertion/deletion gene polymorphism on perioperative hemodynamics after coronary bypass graft surgery

AIM

The angiotensin I-converting enzyme insertion/ deletion polymorphism (ACE-I/D), including three genotypes (II, ID, DD), with a known impact on midterm mortality and morbidity in patients after coronary artery bypass graft surgery (CABG), was studied. Since this polymorphism has been linked with increased vascular response to phenylephrine during cardiopulmonary bypass (CPB), we investigated its possible effect on perioperative hemodynamics in patients undergoing CABG.

METHODS

Genotyping for the ACE-I/D was performed by polymerase chain reaction (PRC) amplification in 110 patients who underwent elective CABG with CPB. Patients were assigned to two groups according to their genotype (group II [II genotype] and group ID/DD [ID and DD genotypes]). Systemic hemodynamics were measured directly before and at 4 h, 9 h, and 19 h after CPB.

RESULTS

Genotype distribution of ACE-I/D was 18%, 57%, and 25% in genotypes II, ID, and DD, respectively. The two groups were similar in age (group II: 66+/-6 years, group ID/DD: 66+/-8 years), body-mass-index (BMI) (group II: 28+/-2, group ID/DD: 29+/-5 kg/m2), male: female ratio (group II: 16: 4, group ID/DD: 63: 27) and Euroscore (group II: 3.1+/-1.9, group ID/DD: 3.5+/-2.1). There were no differences in mortality rate or perioperative systemic hemodynamics. The pulmonary vascular resistance before cardiopulmonary bypass was higher in the ID/DD genotypes than in the II genotypes (227+/-121 vs 297+/-169 dyn.s(-1).m2.cm(-5)). Four hours after CPB no difference remained; at 9 h after cardiopulmonary bypass there was a slight difference in pulmonary vascular resistance between the two groups (247+/-134 vs 290+/-117 dyn.s(-1).m2.cm(-5)) and a significant difference in pulmonary arterial pressure (19+/-6 vs 23+/-8); at 19 h after CPB the differences were no longer detectable.

CONCLUSION

ACE-I/D had no influence on perioperative systemic hemodynamics. However, transitory differences in pulmonary hemodynamic were observed after CPB. These differences may have been due to changes in serum ACE activity during CPB.

Large right atrial myxoma containing gastric heterotopia presenting with dyspnea and bilateral leg edema due to pulmonary emboli and cardiovascular obstruction: the first known report of gastric heterotopia in the cardiovascular system

A 52-year-old male presented with progressive dyspnea, bilateral leg edema, and elevated central venous pressure due to a large right atrial myxoma that caused vascular obstruction and pulmonary emboli. The myxoma contained gastric heterotopia. Other unusual features of this atrial myxoma included its large size, right atrial location, and attachment to the right atrial wall. Although gastric heterotopia has been reported throughout the gastrointestinal tract, and occasionally in other organs, this is the first report of gastric heterotopia in the cardiovascular system. This report confirms and extends previous reports of glandular elements or enteric glands within atrial, or cardiac, myxomas. The clinical presentation of the currently reported patient is explained as follows: the elevated central venous pressure resulted from cardiovascular obstruction and the dyspnea from multiple pulmonary emboli due to the large atrial myxoma. In this case, the clinical presentation was not attributable to the gastric heterotopia. The association of gastric heterotopia with atrial myxoma may, however, be clinically important because of the propensity of gastric heterotopia in the gastrointestinal tract to produce complications. The reported association may provide clues to the histogenesis of these two entities.

Central venous pressure--evaluation, interpretation, monitoring, clinical implications

Physicians need to understand, evaluate and address hemodynamics in every patient and even more importantly in patients that are critically ill. Being able to determine and interpret central venous pressure is one of the most useful bedside evaluation skills, even in the 21st century (Fig. 3). Full Text (Free, PDF) www.bmj.sk.

Altered hormonal regulation and blood flow distribution with cardiovascular deconditioning after short-duration head down bed rest

This study tested the hypothesis that cardiovascular and hormonal responses to lower body negative pressure (LBNP) would be altered by 4-h head down bed rest (HDBR) in 11 healthy young men. In post-HDBR testing, three subjects failed to finish the protocol due to presyncopal symptoms, heart rate was increased during LBNP compared with pre-HDBR, mean arterial blood pressure was elevated at 0, −10, and −20 mmHg and reduced at −40 mmHg, central venous pressure (CVP) and cardiac stroke volume were reduced at all levels of LBNP. Plasma concentrations of renin, angiotensin II, and aldosterone were significantly lower after HDBR. Renin and angiotensin II increased in response to LBNP only post-HDBR. There was no effect of HDBR or LBNP on norepinephrine while epinephrine tended to increase at −40 mmHg post-HDBR ( P = 0.07). Total blood volume was not significantly reduced. Splanchnic blood flow taken from ultrasound measurement of the portal vein was higher at each level of LBNP post-compared with pre-HDBR. The gain of the cardiopulmonary baroreflex relating changes in total peripheral resistance to CVP was increased after HDBR, but splanchnic vascular resistance was actually reduced. These results are consistent with our hypothesis and suggest that cardiovascular instability following only 4-h HDBR might be related to altered hormonal and/or neural control of regional vascular resistance. Impaired ability to distribute blood away from the splanchnic region was associated with reduced stroke volume, elevated heart rate, and the inability to protect mean arterial pressure.

Effect of central hypervolemia on respiratory function

Effects of central hypervolemia on respiratory function and compensatory capabilities of the respiratory system were studied in the anesthetized, vagally intact or vagotomized rats. Central hypervolemia was induced by a head-down tilt on -30 degree rotation. The tilt evoked an elevation of central venous pressure (from -2+/-0.4 cmH2O to 3.9+/-0.8 cmH2O). At 30 min after tilting, airway resistance and negative intrathoracic pressure (indirect measure of respiratory effort) significantly increased, whereas inspiratory flow, tidal volume, and minute ventilation decreased. Load compensatory response was strongly weakened. The tilt-induced esophageal pressure augmentation was suppressed by transection of the vagal nerves. In vagotomized animals inspiratory swings of the intrathoracic pressure increased barely to 116+/-15%, whereas they increased to 216+/-17% of control in vagally intact animals (P<0.05). We conclude that central hypervolemia increases mechanical loading and weakens compensatory capabilities of the respiratory system. Vagal afferents have a part in the realization of the respiratory response to central hypervolemia.

Use of bladder pressure to correct for the effect of expiratory muscle activity on central venous pressure

OBJECTIVE

To assess whether subtracting the expiratory change in intra-abdominal (bladder) pressure (Delta IAP) from central venous pressure (CVP) provides a reliable estimate of transmural CVP in spontaneously breathing patients with expiratory muscle activity.

DESIGN AND SETTING

Prospective observational study in a medical ICU.

PATIENTS

Twenty-four spontaneously breathing patients with central venous and bladder catheters: 18 with no clinical evidence of active expiration (group 1) and 6 with active expiration (group 2).

INTERVENTIONS

Patients in group 1 were coached to change their breathing pattern to one of active expiration for several breaths; those in group 2 were asked to sip water through a straw to briefly interrupt active expiration.

MEASUREMENTS AND RESULTS

During active expiration end-expiratory CVP (uncorrected CVP) and Delta IAP were measured; Delta IAP was subtracted from uncorrected CVP to obtain corrected CVP. End-expiratory CVP during relaxed breathing (best CVP) was assumed to represent the best estimate of transmural CVP. The absolute difference between corrected CVP and best CVP was much less than the difference between uncorrected CVP and best CVP (2.3+/-2.0 vs. 12.5+/-4.7 mmHg).

CONCLUSIONS

In patients with active expiration, subtracting Delta IAP from end-expiratory CVP yields a more reliable (and lower) estimate of transmural CVP than does the uncorrected CVP value.

Are Selective Lung Recruitment Maneuvers Hemodynamically Safe in Severe Hypovolemia? An Experimental Study in Hypovolemic Pigs with Lobar Collapse

BACKGROUND

We have previously shown, in normovolemic pigs, that a selective lung recruitment maneuver (S-LRM), i.e., insufflation of air-oxygen via a balloon catheter with its tip located in the bronchus of a collapsed lung lobe, effectively improves oxygenation and lung volume without affecting hemodynamics negatively. In this study, we examined the respiratory and circulatory effects of S-LRM during hypovolemia with compromised circulation.

METHODS

In eight ventilated (fraction of inspired oxygen, Fio2 1.0) and anesthetized pigs a balloon catheter was inserted in the bronchus of the right lower lung lobe. The lobe was selectively lavaged to create a dense lobar collapse. The pigs were then subjected to S-LRM (40 cm H2O airway pressure for 30 s) at normovolemia, after venesection of 20% and 40% of the blood volume, respectively. Blood gases, compliance of the respiratory system (Crs), vascular pressures, and cardiac output were registered before, during, and after the S-LRM.

RESULTS

Pao2, venous admixture, and Crs improved significantly with S-LRM at all three volume levels. No change in hemodynamics with S-LRM occurred in normovolemia and 20% hypovolemia. For 40% hypovolemia, cardiac output was unchanged by S-LRM, whereas minor decreases in mean arterial blood pressure were seen: 48 (37-52) mm Hg (median, 25th and 75th percentiles) 3 min before S-LRM, 40 (35-44) mm Hg at the end of S-LRM (P = 0.0207), and 47 (39-54) mm Hg 3 min after S-LRM.

CONCLUSION

A S-LRM effectively improved oxygenation and Crs and had only minor circulatory side effects, even in severe hypovolemia in this animal model of lobar collapse.

AMELIORATION OF CARDIAC FUNCTION IN CHRONIC MYOCARDIAL INFARCTED RATS FOLLOWING ADMINISTRATION OF VECTOR pcDNA3.1AM

1. The present study was designed to examine the cardiovascular effects of intravenously administered pcDNA3.1AM, a recombinant non-virus vector carrying a rat adrenomedullin (AM) gene translation fragment, in rats with chronic cardiac dysfunction induced by ligation of the left descending coronary artery. 2. Haemodynamic parameters were recorded by intraventricular catheterization. In situ hybridization and polymerase chain reaction (PCR) were performed to identify the distribution of the introduced vector. The concentration of AM was determined by radioimmunoassay. 3. Progressive cardiac dysfunction was observed following coronary artery ligation, as indicated by a significant reduction in mean arterial pressure (MAP) and increases in both central venous pressure (CVP) and end-diastolic pressure of the left ventricle (LVEDP; P < 0.01). Administration of pcDNA3.1AM significantly attenuated the progressive cardiac dysfunction and lowered the elevated CVP and LVEDP. The introduced vector was widely distributed in different organs, including the lungs, kidney, heart, liver, spleen and brain. However, intense staining of pcDNA3.1 AM was observed in the lungs and kidneys. The introduced vector was localized mainly in the endothelial cells of blood vessels. Radioimmunoassay showed elevated levels of AM in the plasma and lung and heart after surgery, but there was no significant further increase in the concentration of AM after pcDNA3.1AM delivery. 4. The present study has provided some novel findings on the potential beneficial effects of AM gene delivery on chronic cardiac function in rats. Expression of AM by a non-virus vector may also have therapeutic value against cardiac dysfunction in vivo.

Haemodynamic monitoring in acute heart failure

Acute Heart Failure is a major cause of hospitalisation, with a rate of death and complications. New guidelines have been developed in order to diagnose and treat this disease. Despite these efforts pathophysiology and treatments options are still limited. There is agreement among the experts that increasing the cardiac output and the stroke volume without fluid overloading the patient should be the goal of every treatment. Despite this, there is no agreement on how to monitor the cardiac function and how to follow it after a therapeutic intervention. In other fields of critical care cardiovascular monitoring and application of early goal directed protocols showed benefits. This review explores the available possibilities of how to monitor the cardiac function in Acute Heart Failure. Standard and more advanced techniques are presented. Cardiac output monitors from the pulmonary artery catheter to the pulse pressure analysis and Doppler techniques are discussed, with focus on this specific clinical setting. Undoubtedly monitoring is valuable tool, but without a protocol of how to manipulate the haemodynamics, no monitor will prove alone to be beneficial. Haemodynamic driven early goal directed therapy are largely awaited in this field of medicine.