Cardiac Function During Intraperitoneal CO2 Insufflation for Aortic Surgery: A Transesophageal Echocardiographic Study

Morphologic Change of In Vivo Porcine Liver Under 13 mm Hg Pneumoperitoneum Pressure

BACKGROUND

Clinically, the total and residual liver volume must be accurately calculated before major hepatectomy. However, liver volume might be influenced by pneumoperitoneum during surgery. Changes in liver volume change also affect the accuracy of simulation and augmented reality navigation systems, which are commonly first validated in animal models. In this study, the morphologic changes in porcine livers in vivo under 13 mm Hg pneumoperitoneum pressure were investigated.

MATERIALS AND METHODS

Twenty male pigs were scanned with contrast-enhanced computed tomography without pneumoperitoneum and with 13 mm Hg pneumoperitoneum pressure.

RESULTS

The surface area and volume of the liver and the vascular diameter of the aortic lumen, inferior vena cava lumen, and portal vein lumen were measured. There were statistically significant differences in the surface area and volume of the liver (P=0.000), transverse diameter of the portal vein (P=0.038), longitudinal diameter of the inferior vena cava (P=0.033), longitudinal diameter of the portal vein (P=0.036), vascular cross-sectional area of the inferior vena cava (P=0.028), and portal vein (P=0.038) before and after 13 mm Hg pneumoperitoneum pressure.

CONCLUSIONS

This study indicated that the creation of pneumoperitoneum at 13 mm Hg pressure in a porcine causes liver morphologic alterations affecting the area and volume, as well as the diameter of a blood vessel.

Effectiveness of intravenous magnesium sulfate to attenuate hemodynamic changes in laparoscopic surgery: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review and meta-analysis was to determine the effectiveness of intravenous magnesium sulfate when used to attenuate hemodynamic fluctuations associated with the creation of pneumoperitoneum in adults undergoing laparoscopic surgery.

INTRODUCTION

Laparoscopic surgery has gained popularity as a result of improved patient outcomes postoperatively, but pneumoperitoneum alters the patient's physiology and hemodynamic profile during the intraoperative period. Magnesium sulfate is a nonopioid agent known for its ability to blunt the physiologic sympathetic response associated with exposure to noxious stimuli. Magnesium sulfate may be efficacious in promoting anesthetic management that optimizes a patient's cardiopulmonary function while minimzing opioid use.

INCLUSION CRITERIA

Studies with participants at least 18 years old undergoing any elective laparoscopic surgery using pneumoperitoneum with CO2 insufflation were included. Studies were excluded if patients were being treated for pheochromocytoma. Studies eligible for inclusion employed any intravenous dosing strategy of magnesium sulfate, administered at any point in the perioperative period for the purpose of blunting the sympathetic response to creation of a pneumoperitoneum. The comparator utilized was normal saline.

METHODS

A systematic search of MEDLINE, CINAHL, Cochrane Library, Google Scholar, Trip Database, MedNar, Grey Literature Report, ClinicalTrials.gov, and ProQuest Dissertations and Theses was conducted to identify both published and unpublished studies. The search was limited to studies written in the English language and performed on human subjects. Studies were selected for review based on inclusion criteria and were appraised by two reviewers using the appropriate JBI standardized appraisal tool. Data extraction was performed for all outcome variables. Data were pooled using the JBI System for the Unified Management, Assessment and Review of Information. Mean differences (95% confidence interval) were calculated for all continuous variables. Meta-analysis using a fixed effects model was performed at various time points for heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Standard GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) evidence assessment was also reported.

RESULTS

A total of six randomized controlled trials were included in the review. Meta-analysis of data for biophysical parameters (heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure) at five minutes, 10 to 15 minutes, 30 minutes after pneumoperitoneum, and at the end of surgery showed a consistent reduction in the magnesium groups compared to placebo. Support for all outcome variables was determined to be high using the GRADE criteria.

CONCLUSION

The administration of magnesium sulfate consistently demonstrated improved hemodynamic measurements during laparoscopic surgery. All doses administered in the included studies proved beneficial compared to placebo. Magnesium sulfate should be considered as an adjunct agent in laparoscopic surgery to blunt the sympathetic nervous system response to surgical stimulation. The quality of the included studies was high, but small sample sizes and selection of healthy participants may limit the generalizability of the results. The use of magnesium sulfate may have improved effects on patients with significant health comorbidities, but the limitations of the included studies related to sample demographics make the evidence inconclusive.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO (CRD42019139991).

Beneficial Effects of Intravenous Magnesium Administration During Robotic Radical Prostatectomy: A Randomized Controlled Trial

INTRODUCTION

Robotic radical prostatectomy requires prolonged pneumoperitoneum and a steep Trendelenburg position. Magnesium can attenuate the stress response and hemodynamic perturbations. This study aimed to evaluate the effects of intravenous magnesium administration on hemodynamics and the stress response in patients undergoing robotic radical prostatectomy.

METHODS

In this prospective, double-blind, randomized controlled study, 52 patients undergoing robotic radical prostatectomy were randomized into two groups: 26 in the magnesium group and 26 in the control group. The patients in the magnesium group received magnesium sulfate 50 mg/kg intravenously, followed by infusion at a rate of 10 mg/kg/h during surgery. The patients in the control group received an equal volume of 0.9% saline. The primary outcomes were the changes in heart rate and mean arterial pressure (MAP) during surgery. The serum stress hormones (adrenocorticotropic hormone, cortisol, epinephrine, and norepinephrine) were also measured.

RESULTS

MAP showed a significant intergroup difference over time (P_group*time = 0.017); it increased significantly at 5 min after Trendelenburg position in the control group and decreased significantly at 30 min after Trendelenburg position in the magnesium group. The intergroup difference in the change in cortisol concentrations was significant over time (P_group*time = 0.006). The cortisol concentration decreased significantly from baseline to 24 h after surgery in the magnesium group but did not change significantly in the control group. The requirement for intraoperative remifentanil was 35% lower in the magnesium group (P = 0.011), and the severity of postoperative pain at 30 min and 6 h after surgery was also lower in the magnesium group (P = 0.024 and P = 0.015).

CONCLUSION

There is a possibility that intravenous magnesium administration during robotic radical prostatectomy reduces the increases in arterial pressure, cortisol concentrations, opioid requirements, and postoperative pain.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02833038.

Intra-Abdominal Hypertension Is Responsible for False Negatives to the Passive Leg Raising Test

OBJECTIVES

To compare the passive leg raising test ability to predict fluid responsiveness in patients with and without intra-abdominal hypertension.

DESIGN

Observational study.

SETTING

Medical ICU.

PATIENTS

Mechanically ventilated patients monitored with a PiCCO2 device (Pulsion Medical Systems, Feldkirchen, Germany) in whom fluid expansion was planned, with (intra-abdominal hypertension+) and without (intra-abdominal hypertension-) intra-abdominal hypertension, defined by an intra-abdominal pressure greater than or equal to 12 mm Hg (bladder pressure).

INTERVENTIONS

We measured the changes in cardiac index during passive leg raising and after volume expansion. The passive leg raising test was defined as positive if it increased cardiac index greater than or equal to 10%. Fluid responsiveness was defined by a fluid-induced increase in cardiac index greater than or equal to 15%.

MEASUREMENTS AND MAIN RESULTS

We included 60 patients, 30 without intra-abdominal hypertension (15 fluid responders and 15 fluid nonresponders) and 30 with intra-abdominal hypertension (21 fluid responders and nine fluid nonresponders). The intra-abdominal pressure at baseline was 4 ± 3 mm Hg in intra-abdominal hypertension- and 20 ± 6 mm Hg in intra-abdominal hypertension+ patients (p < 0.01). In intra-abdominal hypertension- patients with fluid responsiveness, cardiac index increased by 25% ± 19% during passive leg raising and by 35% ± 14% after volume expansion. The passive leg raising test was positive in 14 patients. The passive leg raising test was negative in all intra-abdominal hypertension- patients without fluid responsiveness. In intra-abdominal hypertension+ patients with fluid responsiveness, cardiac index increased by 10% ± 14% during passive leg raising (p = 0.01 vs intra-abdominal hypertension- patients) and by 32% ± 18% during volume expansion (p = 0.72 vs intra-abdominal hypertension- patients). Among these patients, the passive leg raising test was negative in 15 patients (false negatives) and positive in six patients (true positives). Among the nine intra-abdominal hypertension+ patients without fluid responsiveness, the passive leg raising test was negative in all but one patient. The area under the receiver operating characteristic curve of the passive leg raising test for detecting fluid responsiveness was 0.98 ± 0.02 (p < 0.001 vs 0.5) in intra-abdominal hypertension- patients and 0.60 ± 0.11 in intra-abdominal hypertension+ patients (p = 0.37 vs 0.5).

CONCLUSIONS

Intra-abdominal hypertension is responsible for some false negatives to the passive leg raising test.

Intravenous magnesium sulfate to attenuate hemodynamic changes in laparoscopic surgery: a systematic review protocol

OBJECTIVE

The objective of this systematic review is to determine the efficacy of intravenous magnesium sulfate when used to attenuate hemodynamic fluctuations associated with the creation of pneumoperitoneum in adults undergoing laparoscopic surgery.

INTRODUCTION

Laparoscopic surgery has gained popularity as a result of improved patient outcomes postoperatively, but pneumoperitoneum alters the patient's physiology and hemodynamic profile during the intraoperative period. Magnesium sulfate is a non-opioid agent known for its ability to blunt the physiologic sympathetic response associated with exposure to noxious stimuli. Magnesium sulfate may be efficacious in combating undesirable hemodynamic changes associated with pneumoperitoneum.

INCLUSION CRITERIA

Studies that included participants 18 years or older undergoing any laparoscopic surgery using pneumoperitoneum with CO2 insufflation will be considered. Studies will be excluded if patients were being treated for pheochromocytoma. Studies can employ any intravenous dosing strategy of magnesium sulfate, administered at any point in the perioperative period for the purpose of blunting the sympathetic response to creation of a pneumoperitoneum.

METHODS

A systematic search of MEDLINE, CINAHL, Cochrane Library, Google Scholar, Trip Database, MedNar, Grey Literature Report and ProQuest Dissertations and Theses will be conducted to identify both published and unpublished studies on the topic of interest. The search will be limited to studies written in English and performed on humans. Studies will be selected for review based on inclusion criteria and will be appraised by two reviewers using a standardized appraisal tool.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019139991.

Practical approach to diastolic dysfunction in light of the new guidelines and clinical applications in the operating room and in the intensive care

There is growing evidence both in the perioperative period and in the field of intensive care (ICU) on the association between left ventricular diastolic dysfunction (LVDD) and worse outcomes in patients. The recent American Society of Echocardiography and European Association of Cardiovascular Imaging joint recommendations have tried to simplify the diagnosis and the grading of LVDD. However, both an often unknown pre-morbid LV diastolic function and the presence of several confounders-i.e., use of vasopressors, positive pressure ventilation, volume loading-make the proposed parameters difficult to interpret, especially in the ICU. Among the proposed parameters for diagnosis and grading of LVDD, the two tissue Doppler imaging-derived variables e' and E/e' seem most reliable. However, these are not devoid of limitations. In the present review, we aim at rationalizing the applicability of the recent recommendations to the perioperative and ICU areas, discussing the clinical meaning and echocardiographic findings of different grades of LVDD, describing the impact of LVDD on patients' outcomes and providing some hints on the management of patients with LVDD.

Effect of pneumoperitoneum and steep reverse-Trendelenburg position on mean systemic filling pressure, venous return, and microcirculation during esophagectomy

Background

Keeping adequate tissue perfusion during high-risk abdominal surgery is of utmost importance to decrease postoperative complications. The objective was to investigate the alteration in mean systemic filling pressure (MSFP), venous return (VR) and sublingual microcirculation during pneumoperitoneum and steep reverse-Trendelenburg position during thoracolaparoscopic esophagectomy.

Methods

This is a single-center prospective observational study in operating room at a university hospital. Eleven consecutive patients undergoing minimally invasive esophagectomy. Intraoperative hemodynamic and sublingual microcirculatory variables were simultaneously measured within 5 minutes at the following time points: T1, baseline supine position before the start of surgery; T2, pneumoperitoneum in supine position; T3, steep reverse-Trendelenburg position after the pneumoperitoneum. The cardiac output (CO) was obtained with continuous pulse contour waveform-derived measurements, and the MSFP was estimated with the analogue method.

Results

The pneumoperitoneum and reverse-Trendelenburg caused an increase in stroke volume variation (SVV), MSFP and central venous pressure (CVP), and a decrease in the microcirculatory perfusion index (MFI, <0.05). However, changes in CO, pressure gradient of VR, resistance of VR and blood pressure were not consistent and did not differ significantly across timepoints. Moreover, MFI is significantly related to CVP and MSFP but not to CO and blood pressure (BP). Measurements with MFI ≤2 have a higher CVP and MSFP compared to those with MFI >2. Using a CVP ≥23 mmHg to detect MFI ≤2 results in a sensitivity of 61.54% and a specificity of 100%.

Conclusions

A high CVP is related to poor microcirculatory flow perfusion even if the macrocirculation has been maintained during pneumoperitoneum.

Predictive values of pulse pressure variation and stroke volume variation for fluid responsiveness in patients with pneumoperitoneum

Animal studies suggest that dynamic predictors remain useful in patients with pneumoperitoneum, but human data is conflicting. Our aim was to determine predictive values of pulse pressure variation (PPV) and stroke volume variation (SVV) in patients with pneumoperitoneum using LiDCORapid™ haemodynamic monitor. Standardised fluid challenges of colloid were administered to patients undergoing laparoscopic procedures, one fluid challenge per patient. Intra-abdominal pressure was automatically held at 12 mmHg. Fluid responsiveness was defined as an increase in nominal stroke index (nSI) ≥ 10%. Linear regression was used to assess the ability of PPV and SVV to track the changes of nSI and logistic regression and area under the receiver operating curve (AUROC) to assess the predictive value of PPV and SVV for fluid responsiveness. Threshold values for PPV and SVV were obtained using the "gray zone" approach. A p < 0.05 was considered as statistically significant. 56 patients were included in analysis. 41 patients (73%) responded to fluids. Both PPV and SVV tracked changes in nSI (Spearman correlation coefficients 0.34 for PPV and 0.53 for SVV). Odds ratio for fluid responsiveness for PPV was 1.163 (95% CI 1.01-1.34) and for SVV 1.341 (95% CI 1.10-1.63). PPV achieved an AUROC of 0.674 (95% CI 0.518-0.830) and SVV 0.80 (95% CI 0.668-0.932). The gray zone of PPV ranged between 6.5 and 20.5% and that of SVV between 7.5 and 13%. During pneumoperitoneum, as measured by LiDCORapid™, PPV and SVV can predict fluid responsiveness, however their sensitivity is lower than the one reported in conditions without pneumoperitoneum. Trial registry number: (with the Australian New Zealand Clinical Trials Registry): ACTRN12612000456853.

How Rescue Echocardiography Changed the Intraoperative Management of an Obese Patient with Refractory Hypotension?

The value of perioperative echocardiography as a rescue tool to complement the clinical assessment of patients who develop hemodynamic instability during noncardiac surgery is becoming increasingly recognized. Several studies have demonstrated the utility of echocardiography in establishing a diagnosis during clinical emergencies. We present the case of an obese patient with refractory hypotension during laparoscopic gynecologic surgery in which rescue transesophageal echocardiography was pivotal in elucidating a diagnosis and changing the course of management.

Bariatric Surgery Provides a "Bridge to Transplant" for Morbidly Obese Patients with Advanced Heart Failure and May Obviate the Need for Transplantation

BACKGROUND

In patients with advanced heart failure, morbid obesity is a relative contraindication to heart transplantation due to higher morbidity and mortality in these patients.

METHODS

We performed a retrospective analysis of consecutive morbidly obese patients with advanced heart failure who underwent bariatric surgery for durable weight loss in order to meet eligibility criteria for cardiac transplantation.

RESULTS

Seven patients (4 M/3 F, age range 31-56 years) with left ventricular ejection fraction (LVEF) ≤ 25 % underwent laparoscopic bariatric surgery. Median preoperative body mass index (BMI) was 42.8 kg/m(2) (range 37.5-50.8). There were no major perioperative complications in six of seven patients. Median length of hospital stay was 5 days. There was no mortality recorded during complete patient follow-up. At a median follow-up of 406 days, median BMI reduction was 12.9 kg/m(2) (p = 0.017). Postoperative LVEF improved to a median of 30 % (interquartile range (IQR) 25-53 %; p = 0.039). Two patients underwent successful cardiac transplantation. Two patients reported symptomatic improvement with little change in LV function and now successfully meet listing criteria. Three patients showed marked improvement of their LVEF and functional status, thus removing the requirement for transplantation.

CONCLUSIONS

Bariatric surgery can achieve successful weight loss in morbidly obese patients with advanced cardiac failure, enabling successful heart transplantation. In some patients, cardiac transplantation can be avoided through surgical weight loss.

American Society for Enhanced Recovery (ASER) and Perioperative Quality Initiative (POQI) joint consensus statement on perioperative fluid management within an enhanced recovery pathway for colorectal surgery

BACKGROUND

Enhanced recovery may be viewed as a comprehensive approach to improving meaningful outcomes in patients undergoing major surgery. Evidence to support enhanced recovery pathways (ERPs) is strong in patients undergoing colorectal surgery. There is some controversy about the adoption of specific elements in enhanced recovery "bundles" because the relative importance of different components of ERPs is hard to discern (a consequence of multiple simultaneous changes in clinical practice when ERPs are initiated). There is evidence that specific approaches to fluid management are better than alternatives in patients undergoing colorectal surgery; however, several specific questions remain.

METHODS

In the "Perioperative Quality Initiative (POQI) Fluids" workgroup, we developed a framework broadly applicable to the perioperative management of intravenous fluid therapy in patients undergoing elective colorectal surgery within an ERP.

DISCUSSION

We discussed aspects of ERPs that impact fluid management and made recommendations or suggestions on topics such as bowel preparation; preoperative oral hydration; intraoperative fluid therapy with and without devices for goal-directed fluid therapy; and type of fluid.

What is the evidence for the use of low-pressure pneumoperitoneum? A systematic review

Background

Laparoscopic surgery has several advantages when compared to open surgery, including faster postoperative recovery and lower pain scores. However, for laparoscopy, a pneumoperitoneum is required to create workspace between the abdominal wall and intraabdominal organs. Increased intraabdominal pressure may also have negative implications on cardiovascular, pulmonary, and intraabdominal organ functionings. To overcome these negative consequences, several trials have been performed comparing low- versus standard-pressure pneumoperitoneum.

Methods

A systematic review of all randomized controlled clinical trials and observational studies comparing low- versus standard-pressure pneumoperitoneum.

Results and conclusions

Quality assessment showed that the overall quality of evidence was moderate to low. Postoperative pain scores were reduced by the use of low-pressure pneumoperitoneum. With appropriate perioperative measures, the use of low-pressure pneumoperitoneum does not seem to have clinical advantages as compared to standard pressure on cardiac and pulmonary function. Although there are indications that low-pressure pneumoperitoneum is associated with less liver and kidney injury when compared to standard-pressure pneumoperitoneum, this does not seem to have clinical implications for healthy individuals. The influence of low-pressure pneumoperitoneum on adhesion formation, anastomosis healing, tumor metastasis, intraocular and intracerebral pressure, and thromboembolic complications remains uncertain, as no human clinical trials have been performed. The influence of pressure on surgical conditions and safety has not been established to date. In conclusion, the most important benefit of low-pressure pneumoperitoneum is lower postoperative pain scores, supported by a moderate quality of evidence. However, the quality of surgical conditions and safety of the use of low-pressure pneumoperitoneum need to be established, as are the values and preferences of physicians and patients regarding the potential benefits and risks. Therefore, the recommendation to use low-pressure pneumoperitoneum during laparoscopy is weak, and more studies are required.

Influence of intra-abdominal pressure on the specificity of pulse pressure variations to predict fluid responsiveness

BACKGROUND

The positive predictive value of pulse pressure variations (ΔPP) to discriminate patients who should respond to volume expansion (VE) may be altered in mechanically ventilated patients. Our goal was to determine whether intra-abdominal pressure (IAP) measurements could discriminate patients with true-positive ΔPP values versus patients with false-positive ΔPP values.

METHODS

We designed a prospective pathophysiologic study in a mixed intensive care unit of a university hospital. Sixteen mechanically ventilated patients with hypotension (SAP, <90 mm Hg) and with ΔPP of 13% or more were included. Cardiac output was assessed using Doppler echocardiography before and after VE; IAP was measured using the bladder pressure method. Patients were classified into two groups according to their response to a standardized VE (500 mL of NaCl 0.9%): responders (≥15% increase in cardiac output) and nonresponders.

RESULTS

Nine patients (57%) were responders, and seven patients (43%) were nonresponders. Before VE, IAP was statistically higher in nonresponders (15 [11-22] mm Hg vs. 9 [6.5-11] mm Hg; p = 0.008). The area under the curve of the receiver operating characteristic curve was 0.9 ± 0.08. In patients with ΔPP of 13% or more, an IAP cutoff value of 10.5 mm Hg discriminated between responders and nonresponders with a sensitivity of 100% (59-100%) and a specificity of 78% (40-97%).

CONCLUSION

An increase in IAP of more than 10.5 mm Hg can decrease the positive predictive value of ΔPP. Hence, in patients prone to present abnormal IAP values, IAP should be measured before performing VE directed by the ΔPP marker.

LEVEL OF EVIDENCE

Diagnostic study, level II.

Cardiac ultrasound and abdominal compartment syndrome

This review focuses on the available literature published about the evaluation of haemodynamic consequences of the abdominal compartment syndrome (ACS). Animal and clinical studies described decreased venous return, systemic vasoconstriction, systolic and diastolic dysfunction of left and right ventricles. Doppler echocardiography is a non-invasive bedside procedure which provides a complete haemodynamic evaluation of patients with ACS. Despite numerous evaluations in anesthesia during laparoscopic surgery, the use of echocardiography remains scarce in critically ill patients with ACS.

Noosa, 2 years later… a critical analysis of recent literature

INTRODUCTION

Since the second World Congress on the Abdominal Compartment Syndrome (WCACS) in Noosa 2 years ago, interest and publications on intra-abdominal hypertension (IAH) and ACS have increased exponentially. This paper aimed to critically review recent publications and put this new data into the context of already acquired knowledge concerning IAH/ACS.

METHODS

A Medline and PubMed search was performed from January 2005 up to now using "intra-abdominal pressure (IAP)", "intra-abdominal hypertension (IAH)", "abdominal compartment syndrome (ACS)" and "decompressive laparotomy" as search items.

RESULTS

Although consensus definitions of IAH/ACS have been formulated recently, data on awareness are still disconcerting. Several groups refined current IAP measurement techniques and tested new direct IAP measurement devices for use in selected subpopulations. A series of recent publications identified specific patient subpopulations in IAH/ACS, like patients with burns or severe acute pancreatitis, with their specific pathophysiology and therapy. Although many studies already assessed the effect of elevated IAP on regional and micro-circulatory organ perfusion, a number of new publications attempted to unravel the link between elevated IAP and more "downstream" organ function or histology. Finally, therapy for IAH/ACS still reveals more questions than it answers. Global resuscitation does not necessarily equate with organ resuscitation. In fact, fluid-resuscitation may even induce IAH/ACS.

CONCLUSIONS

After publication of consensus guidelines on IAH/ACS, there is an urgent need for human intervention studies and, in parallel, clinically relevant animal models. Given moderately low incidence of ACS and the complex and interrelated pathologies of the critically ill patient with IAH/ACS, large animal models of pathology-induced IAH/ACS might create the opportunity to gain clinically relevant knowledge on the treatment of IAH/ACS.

Hemodynamic changes during robotic radical prostatectomy

BACKGROUND

Effect on hemodynamic changes and experience of robot-assisted laparoscopic radical prostatectomy (RALRP) in steep Trendelenburg position (45°) with high-pressure CO(2) pneumoperitoneum is very limited. Therefore, we planned this prospective clinical trial to study the effect of steep Tredelenburg position with high-pressure CO(2) pneumoperitoneum on hemodynamic parameters in a patient undergoing RALRP using FloTrac/Vigileo™1.10.

METHODS

After ethical approval and informed consent, 15 patients scheduled for RALRP were included in the study. In the operation room, after attaching standard monitors, the radial artery was cannulated. Anesthesia was induced with fentanyl (2 μg/kg) and thiopentone (4-7 mg/kg), and tracheal intubation was facilitated by vecuronium bromide (0.1 mg/kg). The patient's right internal jugular vein was cannulated and the Pre Sep™ central venous oximetry catheter was connected to it. Anesthesia was maintained with isoflurane in oxygen and nitrous oxide and intermittent boluses of vecuronium. Intermittent positive-pressure ventilation was provided to maintain normocapnea. After CO(2) pneumoperitoneum, position of the patient was gradually changed to 45° Trendelenburg over 5 min. The robot was then docked and the robot-assisted surgery started. Intraoperative monitoring included central venous pressure (CVP), stroke volume (SV), stroke volume variation (SVV), cardiac output (CO), cardiac index (CI) and central venous oxygen saturation (ScvO(2)).

RESULTS

After induction of anesthesia, heart rate (HR), SV, CO and CI were decreased significantly from the baseline value (P>0.05). SV, CO and CI further decreased significantly after creating pneumoperitoneum (P>0.05). At the 45° Trendelenburg position, HR, SV, CO and CI were significantly decreased compared with baseline. Thereafter, CO and CI were persistently low throughout the 45° Trendelenburg position (P=0.001). HR at 20 min and 1 h, SV and mean arterial blood pressure after 2 h decreased significantly from the baseline value (P>0.05) during the 45° Trendelenburg position. CVP increased significantly after creating pneumoperitoneum and at the 45° Trendelenburg position (after 5 and 20 min) compared with the baseline postinduction value (P>0.05). All these parameters returned to baseline after deflation of CO(2) pneumoperitoneum in the supine position. There were no significant changes in SVV and ScvO(2) throughout the study period.

CONCLUSIONS

The steep Trendelenburg position and CO(2) pneumoperitoneum, during RALRP, leads to significant decrease in stroke volume and cardiac output.

Hemodynamic effects of positive end-expiratory pressure during abdominal hyperpression: a preliminary study in healthy volunteers

PURPOSE

An increase in abdominal pressure induces an increase in left ventricular afterload under clinical conditions. We tested the hypothesis that positive end-expiratory pressure (PEEP) could reverse the hemodynamic consequences of abdominal hyperpression by opposing the increase in left ventricular afterload.

MATERIALS AND METHODS

Eight healthy volunteers were investigated during 3 experimental conditions: (1) baseline, (2) increase in abdominal pressure by means of medical antishock trousers (MAST) inflation, and (3) addition of PEEP +10 cm H(2)O. Heart loading conditions and left ventricular systolic and diastolic function were assessed by transthoracic echocardiography.

RESULTS

The application of PEEP significantly reduced the prior increase in end-systolic wall stress: 45 ± 11 vs 55 ± 14 kdyn/cm(2), P < .05. Medical antishock trousers inflation significantly altered the deceleration time of mitral E wave: 199 ± 23 vs 156 ± 38 milliseconds, P < .05. Left ventricular preload and global systolic performance were unaffected by MAST and PEEP applications.

CONCLUSIONS

The increase in left ventricular afterload induced by MAST inflation can be efficiently reduced by the use of a moderate PEEP. Potential clinical applications in the abdominal compartment syndrome or in the setting of laparoscopic surgery should be developed.

Pulse pressure variation and stroke volume variation during increased intra-abdominal pressure: an experimental study

INTRODUCTION

The aim of this study was to evaluate dynamic indices of fluid responsiveness in a model of intra-abdominal hypertension.

METHODS

Nine mechanically-ventilated pigs underwent increased intra-abdominal pressure (IAP) by abdominal banding up to 30 mmHg and then fluid loading (FL) at this IAP. The same protocol was carried out in the same animals made hypovolemic by blood withdrawal. In both volemic conditions, dynamic indices of preload dependence were measured at baseline IAP, at 30 mmHg of IAP, and after FL. Dynamic indices involved respiratory variations in stroke volume (SVV), pulse pressure (PPV), and systolic pressure (SPV, %SPV and Δdown). Stroke volume (SV) was measured using an ultrasound transit-time flow probe placed around the aortic root. Pigs were considered to be fluid responders if their SV increased by 15% or more with FL. Indices of fluid responsiveness were compared with a Mann-Whitney U test. Then, receiver operating characteristic (ROC) curves were generated for these parameters, allowing determination of the cut-off values by using Youden's method.

RESULTS

Five animals before blood withdrawal and all animals after blood withdrawal were fluid responders. Before FL, SVV (78 ± 19 vs 42 ± 17%), PPV (64 ± 18 vs 37 ± 15%), SPV (24 ± 5 vs 18 ± 3 mmHg), %SPV (24 ± 4 vs 17 ± 3%) and Δdown (13 ± 5 vs 6 ± 4 mmHg) were higher in responders than in non-responders (P < 0.05). Areas under ROC curves were 0.93 (95% confidence interval: 0.80 to 1.06), 0.89 (0.70 to 1.07), 0.90 (0.74 to 1.05), 0.92 (0.78 to 1.06), and 0.86 (0.67 to 1.06), respectively. Threshold values discriminating responders and non-responders were 67% for SVV and 41% for PPV.

CONCLUSIONS

In intra-abdominal hypertension, respiratory variations in stroke volume and arterial pressure remain indicative of fluid responsiveness, even if threshold values identifying responders and non-responders might be higher than during normal intra-abdominal pressure. Further studies are required in humans to determine these thresholds in intra-abdominal hypertension.

Anatomical changes due to pneumoperitoneum analyzed by MRI: an experimental study in pigs

PURPOSE

Different effects on cardiovascular and respiratory systems and liver are associated with pneumoperitoneum. This study aimed to determine the morphological changes in the abdominal anatomy as a result of increased intra-abdominal pressure due to pneumoperitoneum using MRI.

METHODS

Ten healthy female pigs were used in this study. MRI studies of the abdomen in supine position were made before the creation of pneumoperitoneum and 1 h after increasing the pressure to 14 mmHg. Changes in area, volume, and longitudinal and transverse length of the liver were measured. The diameters of the lumen of the abdominal aorta, the inferior vena cava and portal vein were observed in three positions along the abdominal cavity. The position of the diaphragm after the induction of pneumoperitoneum was also analyzed.

RESULTS

After induction of pneumoperitoneum, volume and transverse length of the liver was significantly increased, while peak area was decreased. Stenosis in the aortic lumen was observed (P < 0.05). Longitudinal and transverse diameters of the portal lumen were reduced, but significant differences were only found in the longitudinal diameter. Alterations in the diameter of the inferior vena cava lumen were obtained in three analyzed positions, but differences were significant only in two of them. A mean cranial displacement of the diaphragm equal to 25 mm was also observed.

CONCLUSION

Increasing abdominal pressure up to laparoscopic pressure (14 mmHg) provokes morphological changes in the liver, vascular structures and diaphragm. These changes could be related to functional alterations that different organs experience after the induction of pneumoperitoneum.

Article Commentary: Laparoscopy Associated Mesenteric Vascular Complications

Since the first reported case in 1994, a small but significant number of patients have developed major mesenteric arterial and venous thromboses after laparoscopy, usually with catastrophic outcomes. The basic science data in both animal and human models suggest that these events were due in part to specific predisposing patient factors, combined with the physiologic changes in splanchnic hemodynamics that occur during induction and maintenance of pneumoperitoneum. The following manuscript examines the science of this phenomenon in detail and the features of the reported cases to date, with the goal being to increase awareness of this serious and likely underreported phenomenon.

The passive leg-raising maneuver cannot accurately predict fluid responsiveness in patients with intra-abdominal hypertension

OBJECTIVES

The passive leg-raising maneuver is a reversible fluid-loading procedure used to predict fluid responsiveness in mechanically ventilated patients. The aim of the present study was to determine whether intra-abdominal hypertension (which impairs venous return) reduces the ability of passive leg raising to detect fluid responsiveness in critically ill ventilated patients.

DESIGN

A prospective study.

SETTING

The medical and surgical intensive care unit of a university medical center.

PATIENTS

Forty-one mechanically ventilated patients with a pulse pressure variation of >12%.

INTERVENTIONS

Stroke volume was continuously monitored by esophageal Doppler. Intra-abdominal pressure was measured via bladder pressure. After a passive leg-raising maneuver and a return to baseline, fluid loading with 500 mL of saline was performed. Hemodynamic parameters were recorded at each step. Nonresponders to volume loading were not analyzed (10 patients). Thirty-one patients were classified into two groups according to their response to passive leg raising: responders to passive leg raising (at least a 12% increase in stroke volume) and nonresponders to passive leg raising.

MEASUREMENTS AND MAIN RESULTS

Sixteen patients (52%) were responders to passive leg raising, and 15 (48%) were nonresponders to passive leg raising (i.e., false negatives). At baseline, the median intra-abdominal pressure was significantly higher in the nonresponders to passive leg raising than in the responders to passive leg raising (20 [6.5] vs. 11.5 [5.5], respectively; p < .0001). The area under the receiver-operating characteristic curve was 0.969 +/- 0.033. An intra-abdominal pressure cutoff value of 16 mm Hg discriminated between responders to passive leg raising and nonresponders to passive leg raising with a sensitivity of 100% (confidence interval, 78-100) and a specificity of 87.5% (confidence interval, 61.6-98.1). An intra-abdominal pressure of > or =16 mm Hg was the only independent predictor of nonresponse to passive leg raising in a multivariate analysis (odds ratio, 2.6 [confidence interval, 1.1-6.6]; p = .04).

CONCLUSIONS

An intra-abdominal pressure of > or =16 mm Hg seems to be responsible for false negatives to passive leg raising. Hence, the intra-abdominal pressure should be measured in critically ill ventilated patients, especially before performing passive leg raising.

[The effects of pneumoperitoneum on heart rate, mean arterial blood pressure and cardiac output of hypertensive patients during laparoscopic colectomy]

PURPOSE

This study was performed to identify effects of pneumoperitoneum on hemodynamic changes of hypertensive patients undergoing laparoscopic colectomy under general anesthesia.

METHODS

Data collection was done from January 2 to June 10, 2008. Seventy-six patients, including 38 hypertensive patients, who had taken antihypertensive drugs more than 1 month and 38 normotensive patients undergoing laparoscopic colectomy were enrolled in this study. The hemodynamic parameters were heart rate (HR), mean arterial pressure (MAP) and cardiac output (CO) which were measured 7 times from before induction of anesthesia to 5 min after deflation of the pneumoperitoneum. Collected data were analyzed using Repeated Measures ANOVA and Bonferroni comparison method.

RESULTS

HR in the hypertensive group was significantly decreased at deflation of the pneumoperitoneum and 5 min after deflation of the pneumoperitoneum (p=.012). MAP in the hypertensive group was not different from the normotensive group (p=.756). CO in hypertensive group was significantly lower than normotensive group (p<.001) from immediately after pneumoperitoneum to 5 min after deflation of the pneumoperitoneum.

CONCLUSION

The results indicate that pneumoperitoneum during laparoscopic surgery does not lead to clinically negative hemodynamic changes in heart rate, mean arterial pressure or cardiac output of hypertensive patients, who have taken antihypertensive drugs for more than 1 month.

A computerized tomography scan method for calculating the hernia sac and abdominal cavity volume in complex large incisional hernia with loss of domain

Preoperative progressive pneumoperitoneum (PPP) is a safe and effective procedure in the treatment of large incisional hernia (size > 10 cm in width or length) with loss of domain (LIHLD). There is no consensus in the literature on the amount of gas that must be insufflated in a PPP program or even how long it should be maintained. We describe a technique for calculating the hernia sac volume (HSV) and abdominal cavity volume (ACV) based on abdominal computerized tomography (ACT) scanning that eliminates the need for subjective criteria for inclusion in a PPP program and shows the amount of gas that must be insufflated into the abdominal cavity in the PPP program. Our technique is indicated for all patients with large or recurrent incisional hernias evaluated by a senior surgeon with suspected LIHLD. We reviewed our experience from 2001 to 2008 of 23 consecutive hernia surgical procedures of LIHLD undergoing preoperative evaluation with CT scanning and PPP. An ACT was required in all patients with suspected LIHLD in order to determine HSV and ACV. The PPP was performed only if the volume ratio HSV/ACV (VR = HSV/ACV) was >or=25% (VR >or= 25%). We have performed this procedure on 23 patients, with a mean age of 55.6 years (range 31-83). There were 16 women and 7 men with an average age of 55.6 years (range 31-83), and a mean BMI of 38.5 kg/m(2) (range 23-55.2). Almost all patients (21 of 23 patients-91.30%) were overweight; 43.5% (10 patients) were severely obese (obese class III). The mean calculated volumes for ACV and HSV were 9,410 ml (range 6,060-19,230 ml) and 4,500 ml (range 1,850-6,600 ml), respectively. The PPP is performed by permanent catheter placed in a minor surgical procedure. The total amount of CO(2) insufflated ranged from 2,000 to 7,000 ml (mean 4,000 ml). Patients required a mean of 10 PPP sessions (range 4-18) to achieve the desired volume of gas (that is the same volume that was calculated for the hernia sac). Since PPP sessions were performed once a day, 4-18 days were needed for preoperative preparation with PPP. The mean VR was 36% (ranged from 26 to 73%). We conclude that ACT provides objective data for volume calculation of both hernia sac and abdominal cavity and also for estimation of the volume of gas that should be insufflated into the abdominal cavity in PPP.

Curva de aprendizado em cirurgia aórtica videolaparoscópica: estudo experimental em porcos

CONTEXTO: A cirurgia videolaparoscópica (CVL) vem evoluindo como alternativa cirúrgica menos invasiva para o tratamento da doença aterosclerótica oclusiva aorto-ilíaca e do aneurisma da aorta abdominal. Poucos estudos avaliaram objetivamente a curva de aprendizado com essa técnica em cirurgia vascular. OBJETIVO: Avaliar objetivamente os tempos e a evolução de cada passo cirúrgico e demonstrar a exeqüibilidade dessa técnica. MÉTODOS: Entre outubro 2007 e janeiro de 2008, dois cirurgiões vasculares iniciantes na CVL operaram, após cursos e treinamentos, seis porcos consecutivos, com dissecção aórtica e interposição de um enxerto de dácron em um segmento da aorta infra-renal abdominal, com técnica totalmente laparoscópica. RESULTADOS: Todos os tempos cirúrgicos foram decrescentes ao longo do estudo, apresentando redução de 45,9% no tempo total de cirurgia, 85,8% no tempo de dissecção da aorta, 81,2% na exposição da aorta, 55,1% no clampeamento total, 71% na confecção da anastomose proximal e 64,9% na anastomose distal. CONCLUSÃO: O presente estudo mostrou que os resultados técnicos satisfatórios da CVL vascular ocorreram somente após longa curva de aprendizado, que foi decrescente ao longo do tempo, à medida que aumentou a experiência e vivência com os materiais e com a visão não-estereoscópica. Essa técnica pode ser realizada com perfeição por cirurgiões vasculares desde que façam cursos especializados, com treinamento em simuladores e animais, e desde que busquem constante aprimoramento a fim de conseguir resultados similares aos obtidos com a cirurgia convencional.

Physiologic Responses to Infrarenal Aortic Cross-Clamping during Laparoscopic or Conventional Vascular Surgery in Experimental Animal Model: Comparative Study

The aim of this study was to compare the hemodynamic and ventilatory effects of prolonged infrarenal aortic cross-clamping in pigs undergoing either laparotomy or laparoscopy. 18 pigs were used for this study. Infrarenal aortic crossclamping was performed for 60 minutes in groups I (laparotomy, n = 6) and II (laparoscopy, n = 6). Group III (laparoscopy, n = 6) underwent a 120-minute long pneumoperitoneum in absence of aortic clamping (sham group). Ventilatory and hemodynamic parameters and renal function were serially determined in all groups. A significant decrease in pH and significant increase in PaCO₂ were observed in group II, whereas no changes in these parameters were seen in group I and III. All variables returned to values similar to baseline in groups I and II 60 minutes after declamping. A significant increase in renal resistive index was evidenced during laparoscopy, with significantly higher values seen in Group II. Thus a synergic effect of pneumoperitoneum and aortic cross-clamping was seen in this study. These two factors together cause decreased renal perfusion and acidosis, thus negatively affecting the patient's general state during this type of surgery.

Cardiac function during steep Trendelenburg position and CO2 pneumoperitoneum for robotic-assisted prostatectomy: a trans-oesophageal Doppler probe study

BACKGROUND

Haemodynamic changes associated with pneumoperitoneum and steep Trendelenburg position were investigated in non-obese, ASA I-II males, using general anaesthesia (sevoflurane in air/O2, 40%) undergoing robotic-assisted laparoscopic prostatectomy.

METHODS

A trans-oesophageal echo-Doppler probe (Arrow International) measured cardiovascular changes in heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), systemic vascular resistance (SVR), stroke volume (SV) and aortic diameter (AoD) in 35 of 37 males. Assessments were conducted after induction of general anaesthesia in: the supine position; at 45 degrees Trendelenburg; Trendelenburg + pnuemoperitoneum (intra-abdominal 15 mmHg); and at the end of surgery in the supine position.

RESULTS

The Trendelenburg position increased stroke volume. Trendelenburg position + pneumoperitoneum increased MAP and SVR and decreased AoD.

CONCLUSIONS

Pneumoperitoneum and steep Trendelenburg position significantly increase MAP and SVR. Trendelenburg position increased stroke volume. Pneumoperitoneum decreases aortic diameter. No significant changes in cardiac output or stroke volume were noted.

Pulse pressure variation as a tool to detect hypovolaemia during pneumoperitoneum

BACKGROUND

Pulse pressure variation (DeltaPP) and systolic pressure variation (SPV) induced by mechanical ventilation have been proposed to detect hypovolaemia and guide fluid therapy. During laparoscopic surgery, chest compliance is decreased by pneumoperitoneum. This may affect the value of SPV and DeltaPP as indicators of intravascular volume status. Thereby, we investigated the effects of pneumoperitoneum and hypovolaemia on SPV and DeltaPP.

METHODS

We measured DeltaPP, SPV and the inspiratory (Deltaup) and expiratory (Deltadown) components of SPV, at baseline, during pneumoperitoneum, during pneumoperitoneum and hypovolaemia and after the return to baseline conditions, in 11 mechanically ventilated rabbits. Pneumoperitoneum was induced by inflating the abdomen with carbon dioxide, and hypovolaemia was induced by controlled haemorrhage.

RESULTS

Pneumoperitoneum induced an increase in SPV from 8.5 +/- 1.6 to 13.3 +/- 2.6 mmHg (+56%, P < 0.05) as a result of an increase in Deltaup from 2.0 +/- 1.0 to 6.7 +/- 2.1 mmHg (+236%, P < 0.05), but no significant change in Deltadown, nor in DeltaPP. Haemorrhage induced a significant (P < 0.05) increase in SPV from 13.3 +/- 2.6 to 19.9 +/- 3.7 mmHg (+50%), in Deltadown from 6.6 +/- 3.3 to 14.0 +/- 4.9 mmHg (+112%) and in DeltaPP from 11.1 +/- 4.8 to 24.9 +/- 9.8% (+124%) but no change in Deltaup. All parameters returned to baseline values after blood re-infusion and abdominal deflation.

CONCLUSIONS

SPV is modified by haemorrhage but it is also influenced by pneumoperitoneum. In contrast, DeltaPP is modified by haemorrhage but not by pneumoperitoneum. These findings suggest that DeltaPP should be used preferentially instead of SPV to detect hypovolaemia and guide fluid therapy during laparoscopic surgery.

Respiratory and haemodynamic effects of volume-controlled vs pressure-controlled ventilation during laparoscopy: a cross-over study with echocardiographic assessment

BACKGROUND

The effects of pressure-controlled (PC) ventilation on the ventilatory and haemodynamic parameters during laparoscopy procedures had not been carefully assessed. This prospective cross-over study was undertaken to compare how volume-controlled (VC) and PC modes could affect pulmonary mechanics, gas exchange, and cardiac function in patients undergoing laparoscopy.

METHODS

Twenty-one patients undergoing laparoscopic urological procedures had their lungs ventilated at the beginning with VC ventilation. PC ventilation was instituted at the end of the VC sequence. Ventilator settings were adjusted to keep tidal volume, respiratory rate, and Fi(o(2)) constant in every mode. A complete set of ventilatory, haemodynamic, and gas exchange parameters was obtained under VC after 40 min of pneumoperitoneum and 20 min after switching for PC. Transoesophageal echocardiography was performed in order to evaluate systolic and diastolic function of the heart.

RESULTS

When VC was switched to PC, peak airway pressure decreased [mean (sd) 32 (6) vs 27 (6) cm H(2)O; P < 0.0001], peak inspiratory flow increased [17 (3) vs 48 (8) litre min(-1); P < 0.0001), and dynamic compliance improved [+15 (8)%]. No difference was noted for static airway pressure, static compliance, and arterial oxygenation. No significant change could be demonstrated in the systolic [left ventricular end-systolic wall stress 66 (16) vs 63 (14) x 10(3) dyn cm(-2) m(-2)] or diastolic function [early diastolic velocity 10.3 (2.5) vs 10.5 (2.7) cm s(-1)].

CONCLUSIONS

In this study, no short-term beneficial effect of PC ventilation could be demonstrated over conventional VC ventilation in patients with pneumoperitoneum.

Abdomino-thoracic transmission during acs: facts and figures

Elevated intra-abdominal pressure (IAP) exerts effects not only on intra-abdominal organs, but also on organs distant to the abdominal compartment. Abdomino-thoracic interaction during intra-abdominal hypertension (IAH) or abdominal compartment syndrome (ACS) interferes with pulmonary, cardiovascular and cerebral function. In accordance with recent guidelines, IAH is defined as IAP above 12 mmHg and ACS as IAP more than 20 mmHg with one or more new organ failures. In this review we will first discuss the effects of elevated IAP on pulmonary dynamics and the relevance for interpreting airway pressures and adjusting ventilator settings. We will then discuss the interaction between abdomino-thoracic pressure transmission and global haemodynamics, the knowledge of which is necessary for correct assessment of cardiac preload and to optimize fluid therapy in the setting of IAH/ACS. A discussion on the relationship between increased IAP, increased intracranial pressure (ICP) and decreased cerebral perfusion pressure (CPP) will follow. Finally, we will review ventilator-induced thoracic pressure swings and their transmission to the abdominal compartment.