Effect of CO(2) pneumoperitoneum on ventilation-perfusion relationships during laparoscopic cholecystectomy

Physiological and clinical effects of trunk inclination adjustment in patients with respiratory failure: a scoping review and narrative synthesis

BACKGROUND

Adjusting trunk inclination from a semi-recumbent position to a supine-flat position or vice versa in patients with respiratory failure significantly affects numerous aspects of respiratory physiology including respiratory mechanics, oxygenation, end-expiratory lung volume, and ventilatory efficiency. Despite these observed effects, the current clinical evidence regarding this positioning manoeuvre is limited. This study undertakes a scoping review of patients with respiratory failure undergoing mechanical ventilation to assess the effect of trunk inclination on physiological lung parameters.

METHODS

The PubMed, Cochrane, and Scopus databases were systematically searched from 2003 to 2023.

INTERVENTIONS

Changes in trunk inclination.

MEASUREMENTS

Four domains were evaluated in this study: 1) respiratory mechanics, 2) ventilation distribution, 3) oxygenation, and 4) ventilatory efficiency.

RESULTS

After searching the three databases and removing duplicates, 220 studies were screened. Of these, 37 were assessed in detail, and 13 were included in the final analysis, comprising 274 patients. All selected studies were experimental, and assessed respiratory mechanics, ventilation distribution, oxygenation, and ventilatory efficiency, primarily within 60 min post postural change.

CONCLUSION

In patients with acute respiratory failure, transitioning from a supine to a semi-recumbent position leads to decreased respiratory system compliance and increased airway driving pressure. Additionally, C-ARDS patients experienced an improvement in ventilatory efficiency, which resulted in lower PaCO2 levels. Improvements in oxygenation were observed in a few patients and only in those who exhibited an increase in EELV upon moving to a semi-recumbent position. Therefore, the trunk inclination angle must be accurately reported in patients with respiratory failure under mechanical ventilation.

Sánchez-Margallo F, Eugenia Candanosa-Aranda I, Poelaert J, Castellanos G, L. N. G. Malbrain M. The pathophysiological impact of intra-abdominal hypertension in pigs

BACKGROUND

Intra-abdominal hypertension and abdominal compartment syndrome are common with clinically significant consequences. We investigated the pathophysiological effects of raised IAP as part of a more extensive exploratory animal study. The study design included both pneumoperitoneum and mechanical intestinal obstruction models.

METHODS

Forty-nine female swine were divided into six groups: a control group (Cr; n = 5), three pneumoperitoneum groups with IAPs of 20mmHg (Pn20; n = 10), 30mmHg (Pn30; n = 10), 40mmHg (Pn40; n = 10), and two mechanical intestinal occlusion groups with IAPs of 20mmHg (MIO20; n = 9) and 30mmHg (MIO30; n = 5).

RESULTS

There were significant changes (p<0.05) noted in all organ systems, most notably systolic blood pressure (SBP) (p<0.001), cardiac index (CI) (p = 0.003), stroke volume index (SVI) (p<0.001), mean pulmonary airway pressure (MPP) (p<0.001), compliance (p<0.001), pO2 (p = 0.003), bicarbonate (p = 0.041), hemoglobin (p = 0.012), lipase (p = 0.041), total bilirubin (p = 0.041), gastric pH (p<0.001), calculated glomerular filtration rate (GFR) (p<0.001), and urine output (p<0.001). SVV increased progressively as the IAP increased with no obvious changes in intravascular volume status. There were no significant differences between the models regarding their impact on cardiovascular, respiratory, renal and gastrointestinal systems. However, significant differences were noted between the two models at 30mmHg, with MIO30 showing worse metabolic and hematological parameters, and Pn30 and Pn40 showing a more rapid rise in creatinine.

CONCLUSIONS

This study identified and quantified the impact of intra-abdominal hypertension at different pressures on several organ systems and highlighted the significance of even short-lived elevations. Two models of intra-abdominal pressure were used, with a mechanical obstruction model showing more rapid changes in metabolic and haematological changes. These may represent different underlying cellular and vascular pathophysiological processes, but this remains unclear.

Use of volume controlled vs. pressure controlled volume guaranteed ventilation in elderly patients undergoing laparoscopic surgery with laryngeal mask airway

Background

The peak inspiratory pressure (PIP) is crucial in mechanical ventilation with supraglottic airway device (SAD). Pressure-controlled ventilation volume-guaranteed (PCV-VG), delivering a preset tidal volume with the lowest required airway pressure, is being increasingly used during general anesthesia. In this study, we compared respiratory mechanics and circulatory parameters between volume-controlled ventilation (VCV) and PCV-VG in elderly patients undergoing laparoscopic surgery using the laryngeal mask airway supreme (LMA).

Methods

Eighty participants scheduled for laparoscopic surgery were enrolled in this prospective, randomized clinical trial. The participants were randomly assigned to receive VCV or PCV-VG. PIP, dynamic compliance (Cdyn) and mean inspiratory pressure (Pmean) were recorded at 5 min after induction of anesthesia (T1), 5 min after pneumoperitoneum(T2), 30 and 60 min after pneumoperitoneum (T3 and T4). Data including other respiratory variables, hemodynamic variables, and arterial blood gases were also collected. The difference in PIP between VCV and PCV-VG was assessed as the primary outcome.

Results

PIP was significantly lower at T2, T3, and T4 in both groups compared with T1 (all P <  0.0001), and it was significantly lower in the PCV-VG group than the VCV group at T2, T3, and T4 (all P <  0.001). Cydn was decreased at T2, T3, and T4 in two groups compared with T1 (all P <  0.0001), but it was higher in PCV-VG group than in VCV group at T2, T3, and T4 (all P <  0.0001). There were on statistically significant differences were found between the groups for other respiratory and hemodynamic variables.

Conclusion

In elderly patients who underwent laparoscopic surgery using an LMA, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.

Ventilation in patients with intra-abdominal hypertension: what every critical care physician needs to know

The incidence of intra-abdominal hypertension (IAH) is high and still underappreciated by critical care physicians throughout the world. One in four to one in three patients will have IAH on admission, while one out of two will develop IAH within the first week of Intensive Care Unit stay. IAH is associated with high morbidity and mortality. Although considerable progress has been made over the past decades, some important questions remain regarding the optimal ventilation management in patients with IAH. An important first step is to measure intra-abdominal pressure (IAP). If IAH (IAP > 12 mmHg) is present, medical therapies should be initiated to reduce IAP as small reductions in intra-abdominal volume can significantly reduce IAP and airway pressures. Protective lung ventilation with low tidal volumes in patients with respiratory failure and IAH is important. Abdominal-thoracic pressure transmission is around 50%. In patients with IAH, higher positive end-expiratory pressure (PEEP) levels are often required to avoid alveolar collapse but the optimal PEEP in these patients is still unknown. During recruitment manoeuvres, higher opening pressures may be required while closely monitoring oxygenation and the haemodynamic response. During lung-protective ventilation, whilst keeping driving pressures within safe limits, higher plateau pressures than normally considered might be acceptable. Monitoring of the respiratory function and adapting the ventilatory settings during anaesthesia and critical care are of great importance. This review will focus on how to deal with the respiratory derangements in critically ill patients with IAH.

Pressure-controlled Volume Guaranteed Mode Improves Respiratory Dynamics during Laparoscopic Cholecystectomy: A Comparison with Conventional Modes

Background:

Pneumoperitoneum and altered positioning 1in laparoscopic cholecystectomy predispose to alterations in cardiorespiratory physiology. We compared the effects of volume controlled, pressure controlled, and the newly introduced pressure controlled-volume guaranteed ventilation (PCV-VG) modes of ventilation on respiratory mechanics and oxygenation during laparoscopic cholecystectomy.

Materials and Methods:

Seventy-five physical status American Society of Anesthesiologists Classes I and II patients with normal lungs undergoing laparoscopic cholecystectomy were randomly allocated to receive volume controlled ventilation (VCV), pressure-controlled ventilation (PCV), or PCV-VG modes of ventilation during general anesthesia. In all modes of ventilation, the tidal volume was set at 8 mL/kg, and respiratory rate was set at 12 breaths/min with inspired oxygen of 0.4. After pneumoperitoneum, respiratory rate was adjusted to maintain an end-tidal carbon dioxide between 32 and 37 mm Hg. The peak airway pressures, compliance, the mean airway pressures, oxygen saturation, end tidal carbon dioxide and hemodynamics were recorded at the time of intubation (T1), 15 min after pneumoperitoneum (T2) and after desufflation (T3) and were compared. Arterial oxygen tension, arterial carbon dioxide tension at T2 and T3 were compared.

Results:

PCV-VG and PCV mode resulted in lower peak airway pressures than VCV (23.04 ± 3.43, 24.52 ± 2.79, and 27.24 ± 2.37 cm of water, respectively, P = 0.001). Compliance was better preserved in the pressure mediated modes than VCV (fall from baseline was 42%, 29%, and 30% in VCV, PCV, and PCV-VG). The arterial to end-tidal carbon dioxide gradient was lower in PCV-VG and PCV compared to VCV. No difference in oxygenation and hemodynamics were observed.

Conclusion:

PCV and PCV-VG modes are superior to VCV mode in providing adequate oxygenation at lower peak inspiratory pressures.

Effects of pneumoperitoneum and of an alveolar recruitment maneuver followed by positive end-expiratory pressure on cardiopulmonary function in sheep anesthetized with isoflurane-fentanyl

OBJECTIVE

To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep.

STUDY DESIGN

Prospective, randomized, crossover study.

ANIMALS

A total of nine adult sheep (36-52 kg).

METHODS

Sheep were administered three treatments (≥10-day intervals) during isoflurane-fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg^-1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO₂ pneumoperitoneum); PNEUMO_ARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH₂O increases in PEEP of 1 minute duration until 20 cmH₂O of PEEP) was followed by 10 cmH₂O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation.

RESULTS

PaO₂ was decreased from 435-462 mmHg (58.0-61.6 kPa) (range of mean values in CONTROL) to 377-397 mmHg (50.3-52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (C_qst, mL cmH₂O^-1 kg^-1) was decreased from 0.85-0.92 in CONTROL to 0.52-0.58 in PNEUMO. PaO₂ increased from 383-385 mmHg (51.1-51.3 kPa) in PNEUMO to 429-444 mmHg (57.2-59.2 kPa) in PNEUMO_ARM/PEEP (p < 0.05) and C_qst increased from 0.52-0.53 in PNEUMO to 0.70-0.74 in PNEUMO_ARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO₂ and C_qst to control values. Cardiac index (L minute^-1 m²) decreased from 4.80-4.70 in CONTROL to 3.45-3.74 in PNEUMO and 3.63-3.76 in PNEUMO_ARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg.

CONCLUSIONS AND CLINICAL RELEVANCE

Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.

Assessment of Ventilation Distribution during Laparoscopic Bariatric Surgery: An Electrical Impedance Tomography Study

Introduction. The aim of the study was to assess changes of regional ventilation distribution at the level of the 3rd intercostal space in the lungs of morbidly obese patients as a result of general anaesthesia and laparoscopic surgery as well as the relation of these changes to lung mechanics. We also wanted to determine if positive end-expiratory pressure of 10 cm H₂O prevents the expected atelectasis in the morbidly obese patients during general anaesthesia. Materials and Methods. 49 patients completed the examination and were randomized to 2 groups: ventilated without positive end-expiratory pressure (PEEP 0) and with PEEP of 10 cm H₂O (PEEP 10) preceded by a recruitment maneuver with peak inspiratory pressure of 40 cm H₂O. Impedance Ratio (IR) was utilized to examine ventilation distribution changes as a result of anaesthesia, pneumoperitoneum, and change of body position. We also analyzed intraoperative respiratory mechanics and pulse oximetry values. Results. In both groups general anaesthesia caused a ventilation shift towards the nondependent lungs which was not further intensified after pneumoperitoneum. Reverse Trendelenburg position promoted homogeneous ventilation distribution. Respiratory system compliance was reduced after insufflation and improved after exsufflation of pneumoperitoneum. There were no statistically significant differences in ventilation distribution between the examined groups. Respiratory system compliance, plateau pressure, and pulse oximetry values were higher in PEEP 10. Conclusions. Changes of ventilation distribution in the obese do occur at cranial lung regions. During pneumoperitoneum alterations of ventilation distribution may not follow the direction of the changes of lung mechanics. In the obese patients PEEP level of 10 cm H₂O preceded by a recruitment maneuver improves respiratory compliance and oxygenation but does not eliminate atelectasis induced by general anaesthesia.

P53 related apoptosis in kidneys in CO₂ pneumoperitoneum rat model: an immunohistochemical study

Laparoscopic surgery techniques have been increasingly preferred to classic laparotomy by surgeons since 1987. However, this method may have some side effects on different intraabdominal organs including kidneys. The aim of this study is to evaluate the effects of different pressures of CO2 on p53 related apoptosis in kidneys. Totally 24 male rats were divided into four equal groups. CO2 is insufflated into rats' intraabdominal cavity in two different pressures of 10 and 20 mmHg during 1 h. However, in sham group, only cannula was inserted, but no gas was insufflated. After 1 h, 30 min reperfusion was applied. At last, the kidneys were excised and p53 expression and apoptosis were evaluated immunohistochemically. All the data revealed that the number of apoptotic cell in kidney' tubular cells significantly increases in proportion to CO2 pressure level. On the other hand, p53 expression was detected only in the highest pressure. Because the low CO2 pressured group' rats had no p53 expression in kidneys, we suggest that this method can be safely used for abdominal surgery. At the same time, increasing in the number of apoptotic cells parallel to pressure also suggest that CO2 pressure level and application time are very important parameters during CO2 pneumoperitoneum.

Respiratory function during anesthesia: effects on gas exchange

Anaesthesia causes a respiratory impairment, whether the patient is breathing spontaneously or is ventilated mechanically. This impairment impedes the matching of alveolar ventilation and perfusion and thus the oxygenation of arterial blood. A triggering factor is loss of muscle tone that causes a fall in the resting lung volume, functional residual capacity. This fall promotes airway closure and gas adsorption, leading eventually to alveolar collapse, that is, atelectasis. The higher the oxygen concentration, the faster will the gas be adsorbed and the aleveoli collapse. Preoxygenation is a major cause of atelectasis and continuing use of high oxygen concentration maintains or increases the lung collapse, that typically is 10% or more of the lung tissue. It can exceed 25% to 40%. Perfusion of the atelectasis causes shunt and cyclic airway closure causes regions with low ventilation/perfusion ratios, that add to impaired oxygenation. Ventilation with positive end-expiratory pressure reduces the atelectasis but oxygenation need not improve, because of shift of blood flow down the lung to any remaining atelectatic tissue. Inflation of the lung to an airway pressure of 40 cmH2O recruits almost all collapsed lung and the lung remains open if ventilation is with moderate oxygen concentration (< 40%) but recollapses within a few minutes if ventilation is with 100% oxygen. Severe obesity increases the lung collapse and obstructive lung disease and one-lung anesthesia increase the mismatch of ventilation and perfusion. CO2 pneumoperitoneum increases atelectasis formation but not shunt, likely explained by enhanced hypoxic pulmonary vasoconstriction by CO2. Atelectasis may persist in the postoperative period and contribute to pneumonia.

Prolonged outpatient vitamin K antagonist use and risk of venous thromboembolism in patients undergoing total hip or knee replacement

BACKGROUND

Long-term risk of venous thromboembolism (VTE) following total hip or knee replacement (THR/TKR) compared with controls has not been studied extensively, and the long-term influence of outpatient anticoagulant use on VTE risk remains unknown. The objectives were to evaluate long-term VTE risk following THR/TKR compared with matched controls, and to investigate effect modification by prolonged outpatient vitamin K antagonist use.

METHODS

A Danish retrospective nationwide cohort study was conducted. All patients undergoing primary THR/TKR (n = 95,227) between 1998 and 2007 were selected, each matched by age, sex and region with three controls (no THR/TKR). Patients were stratified by prolonged outpatient vitamin K antagonist use in the previous 3 months (in a time-dependent manner). All subjects were followed for VTE, and Cox models were used to calculate disease and medication history adjusted hazard ratios (HRs).

RESULTS

Within 6 weeks following surgery, a 13-fold increased risk of VTE was found for THR (adj. HR 12.9; 95% CI 11.2-14.7), and a 14-fold elevated risk for TKR (adj. HR 13.6; 95% CI 11.0-16.7), compared with matched controls. The risk remained substantially increased for at least 4 months following THR/TKR. Within this period, prolonged outpatient vitamin K antagonist use reduced the increase in VTE risk by 69% for THR and 54% for TKR.

CONCLUSION

The risk of VTE remains substantially elevated for at least 4 months following THR/TKR; this is well beyond the recommended duration of anticoagulant use. The increase in VTE risk is less pronounced in prolonged outpatient vitamin K antagonist users.

Optimizing working space in porcine laparoscopy: CT measurement of the effects of intra-abdominal pressure

BACKGROUND

Several factors may affect volume and dimensions of the working space in laparoscopic surgery. The precise impact of these factors has not been well studied. In a porcine model, we used computed tomographic (CT) scanning for measuring working space volume and distances. In a first series of experiments, we studied the relationship between intra-abdominal pressure (IAP) and working space.

METHODS

Eleven 20 kg pigs were studied under standardized anesthesia and volume-controlled ventilation. Cardiorespiratory parameters were monitored continuously, and blood gas samples were taken at different IAP levels. Respiratory rate was increased when ETCO₂ exceeded 7 kPa. Breath-hold CT scans were made at IAP levels of 0, 5, 10, and 15 mmHg. Insufflator volumes were compared to CT-measured volumes. Maximum dimensions of pneumoperitoneum were measured on reconstructed CT images.

RESULTS

Respiratory rate had to be increased in three animals. Mild hypercapnia and acidosis occurred at 15 mmHg IAP. Peak inspiratory pressure rose significantly at 10 and 15 mmHg. CT-measured volume increased relatively by 93 % from 5 to 10 mmHg IAP and by 19 % from 10 to 15 mmHg IAP. Comparing CT volumes to insufflator volumes gave a bias of 76 mL. The limits of agreement were -0.31 to +0.47, a range of 790 mL. The internal anteroposterior diameter increased by 18 % by increasing IAP from 5 to 10 mmHg and by 5 % by increasing IAP from 10 to 15 mmHg. At 15 mmHg, the total relative increase of the pubis-diaphragm distance was only 6 %. Abdominal width did not increase.

CONCLUSIONS

CT allows for precise calculation of the actual CO₂ pneumoperitoneum volume, whereas the volume of CO₂ released by the insufflator does not. Increasing IAP up to 10 mmHg achieved most gain in volume and in internal anteroposterior diameter. At an IAP of 10 mmHg, higher peak inspiratory pressure was significantly elevated.

Comparison of femoral and carotid blood pressure during laparoscopy in piglets

PURPOSE

The impact of a capnoperitoneum on the known blood pressure (BP) difference of the upper and lower limb was studied in piglets.

METHODS

Eleven German Landrace piglets (body weight, 4.3-7.4 kg; mean body weight, 6.2 kg) were studied. Arterial lines were placed in the right carotid and right femoral artery for pressure monitoring. Intraabdominal pressure levels were increased in steps of 6 mm Hg up to 24 mm Hg.

RESULTS

We found that elevated intraabdominal pressures up to 24 mm Hg did not change the preexisting systolic BP difference between the carotid and femoral arteries. Systolic femoral artery pressure constantly remained 5% higher than its carotid counterpart. In addition, mean and diastolic values were not affected.

CONCLUSIONS

Arterial BP measurements recorded at the legs of piglets when abdominal pressure is increased by up to 24 mm Hg can be used for intraoperative assessment of systemic arterial BP.

Improved ventilation-perfusion matching with increasing abdominal pressure during CO(2) -pneumoperitoneum in pigs

BACKGROUND

CO(2) -pneumoperitoneum (PP) is performed at varying abdominal pressures. We studied in an animal preparation the effect of increasing abdominal pressures on gas exchange during PP.

METHODS

Eighteen anaesthetized pigs were studied. Three abdominal pressures (8, 12 and 16 mmHg) were randomly selected in each animal. In six pigs, single-photon emission computed tomography (SPECT) was used for the analysis of V/Q distributions; in another six pigs, multiple inert gas elimination technique (MIGET) was used for assessing V/Q matching. In further six pigs, computed tomography (CT) was performed for the analysis of regional aeration. MIGET, CT and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia and after 60 min on each of the three abdominal pressures. SPECT was performed three times, corresponding to each PP level.

RESULTS

Atelectasis, as assessed by CT, increased during PP and in proportion to abdominal pressure [from 9 ± 2% (mean ± standard deviation) at 8 mmHg to 15 ± 2% at 16 mmHg, P<0.05]. SPECT during increasing abdominal CO(2) pressures showed a shift of blood flow towards better ventilated areas. V/Q analysis by MIGET showed no change in shunt during 8 mmHg PP (9 ± 1.9% compared with baseline 9 ± 1.2%) but a decrease during 12 mmHg PP (7 ± 0.9%, P<0.05) and 16 mmHg PP (5 ± 1%, P<0.01). PaO(2) increased from 39 ± 10 to 52 ± 9 kPa (baseline to 16 mmHg PP, P<0.01). Arterial carbon dioxide (PCO(2) ) increased during PP and increased further with increasing abdominal pressures.

CONCLUSION

With increasing abdominal pressure during PP perfusion was redistributed more than ventilation away from dorsal, collapsed lung regions. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction mediated by increasing PCO(2) .

Effect of PEEP on regional ventilation during laparoscopic surgery monitored by electrical impedance tomography

BACKGROUND

Anesthesia per se and pneumoperitoneum during laparoscopic surgery lead to atelectasis and impairment of oxygenation. We hypothesized that a ventilation with positive end-expiratory pressure (PEEP) during general anesthesia and laparoscopic surgery leads to a more homogeneous ventilation distribution as determined by electrical impedance tomography (EIT). Furthermore, we supposed that PEEP ventilation in lung-healthy patients would improve the parameters of oxygenation and respiratory compliance.

METHODS

Thirty-two patients scheduled to undergo laparoscopic cholecystectomy were randomly assigned to be ventilated with ZEEP (0 cmH(2)O) or with PEEP (10 cmH(2)O) and a subsequent recruitment maneuver. Differences in regional ventilation were analyzed by the EIT-based center-of-ventilation index (COV), which quantifies the distribution of ventilation and indicates ventilation shifts.

RESULTS

Higher amount of ventilation was examined in the dorsal parts of the lungs in the PEEP group. Throughout the application of PEEP, a lower shift of ventilation was found, whereas after the induction of anesthesia, a remarkable ventral shift of ventilation in ZEEP-ventilated patients (COV: ZEEP, 40.6 ± 2.4%; PEEP, 46.5 ± 3.5%; P<0.001) was observed. Compared with the PEEP group, ZEEP caused a ventral misalignment of ventilation during pneumoperitoneum (COV: ZEEP, 41.6 ± 2.4%; PEEP, 44 ± 2.7%; P=0.013). Throughout the study, there were significant differences in the parameters of oxygenation and respiratory compliance with improved values in PEEP-ventilated patients.

CONCLUSION

The effect of anesthesia, pneumoperitoneum, and different PEEP levels can be evaluated by EIT-based COV monitoring. An initial recruitment maneuver and a PEEP of 10 cmH(2)O preserved homogeneous regional ventilation during laparoscopic surgery in most, but not all, patients and improved oxygenation and respiratory compliance.

Hemodynamic perturbations during robot-assisted laparoscopic radical prostatectomy in 45° Trendelenburg position

BACKGROUND

Robot-assisted laparoscopic radical prostatectomy has gained widespread use. However, circulatory effects in patients subjected to an extreme Trendelenburg position (45°) are not well characterized.

METHODS

We studied 16 patients (ASA physical status I-II) with a mean age of 59 years scheduled for robot-assisted laparoscopic radical prostatectomy (45° head-down tilt, with an intraabdominal pressure of 11-12 mm Hg). Hemodynamics, echocardiography, gas exchange, and ventilation-perfusion distribution were investigated before and during pneumoperitoneum, in the Trendelenburg position and, in 8 of the patients, also after the conclusion of surgery.

RESULTS

In the 45° Trendelenburg position, central venous pressure increased almost 3-fold compared with the initial value, with an associated 2-fold increase in mean pulmonary artery pressure and pulmonary capillary wedge pressure (P<0.01). Mean arterial blood pressure increased by 35%. Heart rate, stroke volume, cardiac output, and mixed venous oxygen saturation were unaffected during surgery, as were echocardiographic heart dimensions. After induction of anesthesia, isovolumic relaxation time was prolonged, with no further change during the study. Deceleration time was normal and stable. In the horizontal position after pneumoperitoneum exsufflation, filling pressures and mean arterial blood pressure returned to baseline levels. Pneumoperitoneum reduced lung compliance by 40% (P<0.01). Addition of the Trendelenburg position caused a further decrease (P<0.05). Arterial blood acid-base balance was normal. End-tidal carbon dioxide tension increased whereas arterial carbon dioxide was unaffected with unchanged ventilation settings. Pneumoperitoneum increased PaO2 (P<0.05). Ventilation-perfusion distribution, shunt, and dead space were unaltered during the study.

CONCLUSIONS

Pneumoperitoneum and 45° Trendelenburg position caused 2- to 3-fold increases in filling pressures, without effects on cardiac performance. Filling pressures were normalized immediately after surgery. Lung compliance was halved. Gas exchange was unaffected. No perioperative cardiovascular complications occurred.

Ventilation-perfusion distributions and gas exchange during carbon dioxide-pneumoperitoneum in a porcine model

BACKGROUND

Carbon dioxide (CO₂)-pneumoperitoneum (PP) of 12 mm Hg increases arterial oxygenation, but it also promotes collapse of dependent lung regions. This seeming paradox prompted the present animal study on the effects of PP on ventilation-perfusion distribution (V/Q) and gas exchange.

METHODS

Fourteen anaesthetized pigs were studied. In seven pigs, single photon emission computed tomography (SPECT) was used for spatial analysis of ventilation and perfusion distributions, and in another seven pigs, multiple inert gas elimination technique (MIGET) was used for detailed analysis of V/Q matching. SPECT/MIGET and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia before and 60 min after induction of PP.

RESULTS

SPECT during PP showed no or only poorly ventilated regions in the dependent lung compared with the ventilation distribution during anaesthesia before PP. PP was accompanied by redistribution of blood flow away from the non- or poorly ventilated regions. V/Q analysis by MIGET showed decreased shunt from 9 (sd 2) to 7 (2)% after induction of PP (P<0.05). No regions of low V/Q were seen either before or during PP. Almost no regions of high V/Q developed during PP (1% of total ventilation). Pa(o₂) increased from 33 (1.2) to 35.7 (3.2) kPa (P<0.01) and arterial to end-tidal Pco₂ gradient (Pae'(co₂) increased from 0.3 (0.1) to 0.6 (0.2) kPa (P<0.05).

CONCLUSIONS

Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction.

Development of atelectasis and arterial to end-tidal PCO2-difference in a porcine model of pneumoperitoneum

BACKGROUND

Intraperitoneal insufflation of carbon dioxide (CO2) may promote collapse of dependent lung regions. The present study was undertaken to study the effects of CO2-pneumoperitoneum (CO2-PP) on atelectasis formation, arterial oxygenation, and arterial to end-tidal PCO2-gradient (Pa-E'(CO2)).

METHODS

Fifteen anaesthetized pigs [mean body weight 28 (SD 2) kg] were studied. Spiral computed tomography (CT) scans were obtained for analysis of lung tissue density. In Group 1 (n=5) mechanical ventilation (V(T)=10 ml kg (-1), FI(O2)=0.5) was applied, in Group 2 (n=5) FI(O2) was increased for 30 min to 1.0 and in Group 3 (n=5) negative airway pressure was applied for 20 s in order to enhance development of atelectasis. Cardiopulmonary and CT data were obtained before, 10, and 90 min after induction of CO2-PP at an abdominal pressure of 12 mmHg.

RESULTS

Before CO2-PP, in Group 1 non-aerated tissue on CT scans was 1 (1)%, in Group 2 3 (2)% (P<0.05, compared with Group 1), and in Group 3 7 (3)% (P<0.05, compared with Group 1 and Group 2). CO2-PP significantly increased atelectasis in all groups. PaO2/FI(O2) fell and venous admixture ('shunt') increased in proportion to atelectasis during anaesthesia but CO2-PP had a varying effect on PaO2/FI(O2) and shunt. Thus, no correlation was seen between atelectasis and PaO2/FI(O2) or shunt when all data before and during CO2-PP were pooled. Pa-E'(CO2), on the other hand correlated strongly with the amount of atelectasis (r2=0.92).

CONCLUSIONS

Development of atelectasis during anaesthesia and PP may be estimated by an increased Pa-E'(CO2).

High flow insufflation for the maintenance of the pneumoperitoneum during bariatric surgery

Minimally invasive bariatric procedures next to becoming more and more popular have established a new field of applications for carbon dioxide (CO2) insufflators. In laparoscopic bariatric procedures, gas is used to insufflate the peritoneal cavity and increase the intra-abdominal pressure up to 15 mm Hg for optimal exposure and a suitable operating field. The increased intra-abdominal pressure during pneumoperitoneum can reduce femoral venous flow, intra-operative urine output, portal venous flow, respiratory compliance,and cardiac output. However, clinical complications related to these effects are rare. Yet, surgeons should be constantly aware that the duration of an operation is an important factor in reducing the patient's exposure to CO2 pneumoperitoneum and its adverse effects. The optimized performance of the bariatric high flow insufflator allows reaching stable abdominal pressure conditions quicker and at a higher level than a common insufflator. Therefore, high flow insufflators offer great advantages in maintaining intra-abdominal pressure and temperature in comparison to conventional insufflators and thus enhance laparoscopic bariatric surgery by potentially reducing the operating time and the undesirable effects of CO2 pneumoperitoneum.

The comparative effects of pneumoperitoneum on apoptosis and p53 expression in gastrointestinal organs

BACKGROUND

Laparoscopic surgical techniques have been increasingly preferred to classic laparotomy by surgeons since 1987. The pneumoperitoneum is often used to facilitate the intra-abdominal field, but it carries the risk of its ischemic potential and has differences [l2]of metabolic, inflammatory, and infectious consequences, depending on the pressure set and kind of gas used. However, the mechanisms related with the cell injury observed after laparoscopy are still unknown. The aim of this study was to evaluate the effects of different pressures of CO(2) on apoptosis and p53 expression in small and large intestines and the stomach.

MATERIALS AND METHODS

In total, 30 Sprague-Dawley male rats were used in the study. CO(2) is insufflated into the intra-abdominal cavity through a angiocatheter cannule by an insufflator set at two different pressures of 10 and 20 mm Hg during 60 minutes. In the control group, the cannule was inserted into the intra-abdominal cavity without any other surgical procedure and no gas was insufflated. After 60 minutes, the rats were sacrificed and a laparotomy was performed. The small and large intestines and stomach were excised. The samples were histologically processed and an immunohistochemical analysis was performed.

RESULTS

The results of the study revealed that the number of apoptotic cells in intra-abdominal organs we studied increased in proportion to the CO(2) pressure level. However, the p53 expression was detected only in the stomach.

CONCLUSIONS

Our study showed that the number of apoptotic cells rises in parallel to the increase in intra-abdominal pressure following the CO(2) pneumoperitoneum in rat large and small intestine and stomach. Although the apoptosis was activated by the p53 pathway in the stomach, it was not so in the large and small intestine.

Laparoscopic colon surgery: unreliability of end-tidal CO2 monitoring

BACKGROUND

The relatively good haemodynamic and respiratory tolerance to abdominal CO(2) insufflation has mostly been observed in healthy patients during short-lasting laparoscopic procedures. End-tidal CO(2) pressure (PetCO(2)) has been shown to be a reliable method to assess arterial CO(2) (PaCO(2)) in the absence of cardio-respiratory disease in this setting. However, no study has investigated whether PetCO(2) is accurately related to PaCO(2) during laparoscopic colon surgery. Indeed, these procedures last longer, prolonging the pneumoperitoneum and requiring a Trendelenburg position. The aim of the present study was to measure the PaCO(2)-PetCO(2) difference over time in patients undergoing laparoscopic colon surgery and to determine whether PaCO(2) is reliably assessed by PetCO(2).

METHODS

Forty consecutive patients (ASA I and II) scheduled for laparoscopic colon surgery were anaesthetized and ventilated to obtain a PetCO(2) between 4.0 and 5.5 kPa. After initiation of CO(2) insufflation, PaCO(2) and PetCO(2) were recorded every 30 min during surgery.

RESULTS

No complication was observed during anaesthesia. The mean arterial pressure increased significantly after CO(2) insufflation and remained steady up to the end of pneumoperitoneum. The heart rate remained stable over time. The relation between PaCO(2) and PetCO(2) was not constant among patients and increased over time within the same patients. The R(2) values fluctuated and did not show a constant correlation between PaCO(2) and PetCO(2).

CONCLUSION

The correlation between PaCO(2) and PetCO(2) during laparoscopic colon surgery is inconsistent mainly due to inter- and intra-individual variability.

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.

Pressure-controlled ventilation does not improve gas exchange in morbidly obese patients undergoing abdominal surgery

BACKGROUND

Morbid obesity results in marked respiratory pathophysiologic changes that may lead to impaired intraoperative gas exchange. The decelerating inspiratory flow and constant inspiratory airway pressure resulting from pressure-controlled ventilation (PCV) may be more adapted to these changes and improve gas exchanges compared with volume-controlled ventilation (VCV).

METHODS

Forty morbidly obese patients scheduled for gastric bypass were included in this study. Total intravenous anesthesia was given using the target-controlled infusion technique. During the first intraoperative hour, VCV was used and the tidal volume was adjusted to keep end-tidal PCO(2) around 35 mmHg. After 1 h, patients were randomly allocated to 30-min VCV followed by 30-min PCV or the opposite sequence using a Siemens Servo 300. FiO(2) was 0.6. During PCV, airway pressure was adjusted to provide the same tidal volume as during VCV. Arterial blood was sampled for gas analysis every 15 min. Ventilatory parameters were also recorded.

RESULTS

Peak inspiratory airway pressures were significantly lower during PCV than during VCV (P < 0.0001). The other ventilatory parameters were similar during the two periods of ventilation. PaO(2) and PaCO(2) were not significantly different during PCV and VCV.

CONCLUSION

PCV does not improve gas exchange in morbidly obese patients undergoing gastric bypass compared to VCV.

p53 Expression and apoptosis in liver and spleen during CO2 pneumoperitoneum

BACKGROUNDS AND AIMS

Laparoscopic surgery techniques have been increasingly preferred to classic laparotomy by surgeons since 1987. However, this method has some important adverse effects on intra-abdominal organs. The aim of this study is to evaluate the effects of different pressures of CO(2) on apoptosis and p53 expression in cells in liver and spleen.

METHODS

In total, 30 male Sprague-Dawley rats were used in the study. CO(2) was insufflated into the intra-abdominal cavity via angiocatheter cannule by an insufflator in two different pressures of 10 and 20 mm Hg for 60 min. However, in the control group, only cannule was inserted into the intra-abdominal cavity, but no gas was insufflated. After 60 min, the rats were killed and laparotomy was applied. The liver and spleen were excised. The samples were histologically processed and immunohistochemistry was applied.

RESULTS

All the data revealed that the number of apoptotic cells in liver and spleen increases in proportion to CO(2) pressure level. No p53 expression was detected in both organs.

CONCLUSION

CO(2) pressure level and application time may affect on cells living in liver and spleen. High pressure and/or long application time may cause releasing of cytokines and superoxide radicals from these organs' cells, and transient or serious organ dysfunctions may occur.

Effect of age on pulmonary gas exchange during laparoscopy in the Trendelenburg lithotomy position

BACKGROUND

Physiological changes in respiratory mechanics caused by aging may lead to a deterioration in pulmonary gas exchange, an increase in the alveolar-arterial oxygen gradient [(A-a)D(O2)] and a difference between the arterial carbon dioxide (CO(2)) tension (P(a)(CO(2))) and expired end-tidal CO(2) tension (P(ET)(CO(2))) [P((a-ET))(CO(2))] during laparoscopy in the Trendelenburg lithotomy position (TLP).

METHODS

The subjects were 51 gynecologic patients. Pressure-controlled ventilation was used to maintain P(ET)(CO(2)), measured by the side stream method, within the range 4-4.67 kPa. During laparoscopy with CO(2) insufflation in TLP, the tidal volume was increased to keep P(ET)(CO(2)) within +/- 20% of the pre-insufflation value. The subjects were divided into three groups by age: young group (< 45 years); middle-aged group (45-64 years); and elderly group ( > or = 65 years).

RESULTS

Before pneumoperitoneum (PPN), significant differences were found between the young and elderly groups in the arterial oxygen tension (P(a)(O(2))), (A-a)D(O(2)), P(a)(CO(2)) and P((a-ET))(CO(2)). In all groups, the peak inspiratory pressure and P(a)(CO(2)) increased progressively during PPN in TLP. P((a-ET))(CO(2)) increased gradually after starting CO(2) insufflation in TLP only in the elderly group.

CONCLUSIONS

An increase in P((a-ET))(CO(2)) was seen during PPN in TLP in the elderly group. With CO(2) insufflation in TLP, the setting of mechanical ventilation based on the value of P(ET)(CO(2)) (measured by the side stream method) should be determined with caution in elderly patients.

Effects of pneumoperitoneum on the amplitude of diaphragmatic excursion in pigs

OBJECTIVE

To study the effects that pneumoperitoneum achieved through carbon dioxide insufflation has on diaphragmatic excursion in pigs.

METHODS

A total of 14 male Landrace pigs, 30 to 45 days of age and weighing five to seven kilograms each, were used. The sample was randomly and equally divided into two groups: one (n = 7) in which pneumoperitoneum was maintained at 10 mmHg for 60 minutes; and another (n = 7) in which pneumoperitoneum was maintained at 15 mmHg (also for 60 minutes). After anesthetic induction, the animals were intubated. Flow volume was monitored, and the amplitude of diaphragmatic excursion was analyzed using noninvasive ultrasound imaging of the right hemidiaphragm.

RESULTS

In both groups, restricted diaphragmatic excursion was observed only during the procedure. There was no statistical difference between the two pressure levels studied.

CONCLUSION

The amplitude of diaphragmatic excursion was restricted during abdominal insufflation, independent of the pressure level (within the 10-15 mmHg range), during the study period.

Positive end-expiratory pressure improves arterial oxygenation during prolonged pneumoperitoneum

BACKGROUND

Laparoscopic surgery usually requires the use of a pneumoperitoneum by insufflating gas in the peritoneal space. The gas most commonly used for insufflation is carbon dioxide. Increased intra-abdominal pressure causes cephalad displacement of the diaphragm resulting in compressed lung areas, which leads to formation of atelectasis, especially during mechanical ventilation. The aim of this prospective study was to investigate the effect of prolonged intraperitoneal gas insufflation on arterial oxygenation and hemodynamics during mechanical ventilation with and without positive end-expiratory pressure (PEEP).

METHODS

Twenty patients undergoing totally endoscopic robot-assisted radical prostatectomy were randomly allocated to one of two groups. In the PEEP group (n = 10) a constant PEEP of 5 cmH(2)O was used, whereas in the ZPEEP group (n = 10) no PEEP was used.

RESULTS

Application of PEEP (5 cmH(2)O) resulted in significantly higher P(a)O(2) levels after 3 h (182 +/- 49 vs. 224 +/- 35 mmHg) and 4 h (179 +/- 48 vs. 229 +/- 29 mmHg) of pneumoperitoneum; after desufflation, P(a)O(2) values decreased significantly below preinsufflation values. While there were no significant differences in heart rate, central venous pressure (CVP) and mean arterial blood pressure (MAP) during pneumoperitoneum between both groups, baseline values in CVP and MAP differed significantly between both groups with higher levels in the ZPEEP group.

CONCLUSION

The application of a constant positive airway pressure of 5 cmH(2)O preserves arterial oxygenation during prolonged pneumoperitoneum.

Repercussões respiratórias do pneumoperitônio induzido em suínos

Objetivo: Estudar, na faixa tida como segura, as repercussões respiratórias de diferentes pressões de pneumoperitônio, com dióxido de carbono, induzido em suínos. Métodos: Foram utilizados 14 suínos machos, da raça Landrace, pesando entre cinco e sete quilos, com 30 a 45 dias de idade. A amostra foi subdividida igualitariamente em Grupo A (pneumoperitônio com 10mmHg durante 60 minutos) e Grupo B (pneumoperitônio com 15mmHg durante 60 minutos). Após a indução anestésica, os animais foram intubados, sendo monitorado o volume corrente (VC) e a saturação periférica de oxigênio (SpO2). Resultados: Não houve diferença estatística nos valores do VC e SpO2 antes, durante e após a indução do pneumoperitônio. Conclusão: O pneumoperitônio, nos níveis pressóricos de 10 a 15mmHg, não causou alteração significativa nos padrões respiratórios de suínos, durante o período de tempo estudado.

Effects of continuous negative extra-abdominal pressure on cardiorespiratory function during abdominal hypertension: an experimental study

OBJECTIVE

To investigate whether negative extra-abdominal pressure (NEXAP) improves respiratory function and induces a blood shift from the intrathoracic compartment and to assess whether these effects are influenced by abdominal pressure.

DESIGN AND SETTING

Prospective, randomized, controlled trial in the animal laboratory of a university hospital.

SUBJECTS

Eight sedated and paralyzed pigs (19.6+/-3.4 kg).

INTERVENTIONS

Application of NEXAP (-20 cmH(2)O).

MEASUREMENTS AND RESULTS

Airway, esophageal, gastric and central venous pressures were recorded simultaneously. Intrathoracic blood volume was assessed by PiCCO. The effects of NEXAP were assessed with and without abdominal hypertension by intraperitoneal insufflation of helium. NEXAP caused a lasting drop of gastric (1.97+/-2.26 mmHg) and esophageal (1.21+/-0.67 mmHg) pressures, while end-expiratory airway pressure was similar, hence transpulmonary pressure increased. Intrathoracic blood volume dropped from 358+/-47 to 314+/-47 ml. The fall was associated with a decrease in central venous pressure (R(2)=0.820). When peritoneal pressure was raised (24.7+/-5.5 mmHg), the effects were less marked. However, the difference between negative pressure around the abdomen and the pressure inside the abdomen (effective NEXAP) was correlated with the proportional changes in intrathoracic blood volume (R(2)=0.648), being greater with more negative effective NEXAP. NEXAP improved chest wall elastance during abdominal hypertension (from 0.067+/-0.023 to 0.056+/-0.021 cmH(2)O/ml).

CONCLUSIONS

NEXAP increases lung volume and causes a shift of blood from the intrathoracic compartment. It needs to be tailored against abdominal pressure to be effective.

Aminotransferases after experimental pneumoperitoneum in dogs

BACKGROUND

Laparoscopic surgery has rapidly become a popular and widely used technique. Elevated intra abdominal pressure due to gas insufflation for laparoscopic surgery may result in a number of local and systemic effects on the organism. The effects of pneumoperitoneum on the cardiovascular and respiratory system are well known today, but very few studies have been carried out on the consequences of pneumoperitoneum on hepatic integrity. The aim of the present study was to assess changes in aminotransferases, bilirubin and prothrombin time after pneumoperitoneum in dogs.

METHODS

The effects of different levels and duration of intra abdominal pressure and different gases on liver function test were investigated in dogs. The levels of aspartate aminotransferase, alanine aminotransferase, total and direct bilirubin, and prothrombin time, according to the duration and the level of pneumoperitoneum and gas, were measured at 6, 12, 24 and 48 h of desufflation.

RESULTS

The levels of total bilirubin, direct bilirubin and prothrombin time showed no significant alteration. A statistically significant (P < 0.01) elevation of aspartate aminotransferase and alanine aminotransferase was recorded in the group of animals with higher intra abdominal pressure and longer duration of pneumoperitoneum. They returned to normal values within 48 h.

CONCLUSION

Transient elevation of hepatic transaminases occurred after laparoscopic surgery, but they returned to normal values within 48 h. These increases were more prominent with higher and longer intra abdominal pressures irrespective of the type of insufflated gas. Alteration in aminotransferases was not associated with any clinical signs of hepatic dysfunction in experimental animals.

Anaesthetic considerations in patients with chronic pulmonary disease

PURPOSE OF REVIEW

Chronic pulmonary diseases are getting more important in daily anaesthetic practice, because prevalence is increasing and improved anaesthetic techniques have led to the abandonment of previous contraindications to anaesthesia. It is therefore essential for the anaesthetist to be up to date with current clinical concepts and their impact on the conduction of anaesthesia as well as new insights into how to anaesthetise these patients safely.

RECENT FINDINGS

If patients are treated adequately, open and minimally invasive operations can be safely performed under regional and general anaesthesia. The management of acute exacerbations remains challenging, and first-line medical treatment should be supported by non-invasive ventilation. In controlled mechanical ventilation, parameters should be set to avoid dynamic hyperinflation.

SUMMARY

Assessing the functional status of patients admitted for surgery remains a difficult task, and in patients identified as being at risk by clinical examination additional spirometry and blood gas measurements may be helpful. If there are flow limitations and signs of respiratory failure, the anaesthetist should be highly alarmed and monitor the patient closely and invasively, yet there is no reason to deny any patient a substantially beneficial operation.