Intra-abdominal CO2 Insufflation Research Articles

Comparative evaluation of optic nerve sheath diameter in patients undergoing laparoscopic cholecystectomy using low and standard pressures of gas insufflations.

Background and Aims:Intra-abdominal insufflation of CO2 is associated with an increase of intracranial pressure (ICP). We conducted this randomized control trial to compare the impact of low vs standard pressure pneumoperitoneum on ICP through the ultrasonographic estimation of the optic nerve sheath diameter (ONSD).Material and Methods:Patients of age group 18–80 years planned for laparoscopic cholecystectomy were randomly allocated into two groups; group S (standard pressure of 12–16 mmHg) and group L (low pressure of 8–10 mmHg) on the basis of intra-abdominal pressures used for the surgery. All were administered general anesthesia and end-tidal carbon dioxide (ETCO2) was maintained between 35 and 40 mmHg and peak airway pressures less than 35 cmH2O. ONSD was measured in either eye at a point 3 mm posterior to the globe at following time intervals; baseline, 5 min after induction, 10 min after insufflation, 10 min after reverse Trendelenburg, intraoperatively during surgery and after exsufflation in the supine position.Results:The demographic profile and operative times were comparable. ONSD was measured in 100 patients in each group for both the eyes and no patient had values above the cutoff value of 5.0 mm. No significant difference in the ONSD was observed at the above mentioned time intervals between the groups. There was a statistically significant lower value of the heart rate and mean arterial pressure in the low-pressure group.Conclusion:Intra-abdominal insufflation of CO2 at standard and low pressures does not increase ICP in short duration surgeries and thus both the pressures can be safely used in adult patients operated in reverse Trendelenburg position. Advantages of low pressure were limited to better hemodynamic control.

The change of endotracheal tube cuff pressure during laparoscopic surgery

BackgroundWe evaluated the endotracheal tube cuff pressure (Pcuff) changes during pneumoperitoneum for laparoscopic cholecystectomy and the correlations between body mass index (BMI), pneumoperitoneum time, and Pcuff changes.MethodsTotal 60 patients undergoing laparoscopic cholecystectomy were allocated to either a study group (BMI ≥ 25 kg/m2) or a control group (BMI < 25 kg/m2). The endotracheal intubation was performed with a high-volume low-pressure cuffed oral endotracheal tube. A manometer was connected to the pilot balloon using a 3-way stopcock and the cuff was inflated. The change in Pcuff was defined as the difference between the pressure just before intra-abdominal CO2 insufflation and the pressure before CO2 desufflation.ResultsPcuff increased to 5.3 ± 3.6 cmH2O in the study group and 5.7 ± 5.4 cmH2O in the control group. There was no significant difference between two groups. While BMI was not correlated with change in Pcuff (r = 0.022, p = 0.867), there was a significant correlation between change in Pcuff and the duration of pneumoperitoneum (r = 0.309, p = 0.016).ConclusionThe change in Pcuff was not affected by BMI and was significantly correlated with pneumoperitoneum time. We recommend regular measurement and adjustment of Pcuff during laparoscopic surgery.

Hemodynamic and Respiratory Effects of Robot‐assisted Laparoscopic Fundoplication in Children

Laparoscopic fundoplication is increasingly used for treating gastro-esophageal reflux disease in children. Mechanical and pharmacological effects may contribute to hemodynamic and respiratory changes during carbon dioxide pneumoperitoneum. The aim of the present study was to evaluate the hemodynamic and respiratory effects of pneumoperitoneum (PP) with an intra-abdominal pressure (IAP) of 12 mmHg in children undergoing robot-assisted laparoscopic fundoplication during total intravenous anesthesia. Ten children, aged 8-16 years, American Society of Anesthesiologists physical status II-III, scheduled for robot-assisted laparoscopic fundoplication in the reverse Trendelenburg position were investigated. Minute ventilation (MV), peak inspiratory pressure (PIP), IAP, heart rate (HR), mean arterial blood pressure (MAP) were recorded, together with pH, base excess, HCO3-, P(et)CO2, PaCO2, and PaO2 at six time points: before insufflation, 10, 30, 60, 90 minutes after creating PP and after desufflation. The IAP was maintained at 12 mmHg. During insufflation MAP increased significantly from 70.6 (+/-9.0) to 84.8 (+/-10.4) mmHg, MV was increased from 4.6 (+/-0.8) to 5.5 (+/-0.9) l min(-1), PIP increased, PaO2 and pH decreased. P(et)CO2 increased from 33.1 (+/-1.6) to 36.6 (+/-1.6) mmHg together with PaCO2. Hemodynamic and respiratory effects due to the intra-abdominal insufflation of CO2 with an IAP of 12 mmHg are well tolerated, and anesthesia with remifentanil, propofol and mivacurium facilitates extubation immediately at the end of surgery.

Low-flow Sevoflurane Anesthesia in Laparoscopic Cholecystectomy

There has been a revival of interest in low-flow anesthesia (LFA) techniques over the past decade or so, primarily driven by the introduction of newer anesthetic agents with low solubility and relatively higher costs. The advantages of LFA include a reduction in the consumption of anesthetic gases, reduced operating room and environmental pollution, and the conservation of heat and humidity within the respiratory tract of patients. Historically, most anesthesiologists have been trained to use high-flow anesthesia (HFA), and the anesthetic equipment and available anesthetic agents have not been suitable for LFA. HFA techniques, however, have the potential for inducing hypoxia and/or hypercapnia, administration of an overor underdosage of anesthetic gases, and the accumulation of potentially toxic degradation products. Laparoscopic cholecystectomy (LC) with intra-abdominal CO2 insufflation has a special anesthetic consideration in that it may induce hypercapnia, acidemia, and depressed hemodynamics. A number of studies have been published evaluating the use of LFA in a wide variety of surgical procedures, including gastrointestinal, gynechological and general surgery. Despite many advantages of the LFA as mentioned above, few studies have actually been done using LFA with sevoflurane in LC. One likely explanation is the potential for hypercapnia with LFA resulting from rebreathing exhaled CO2 coupled with an increase in arterial CO2 from the intraperitoneal CO2 insufflation. The purpose of this study was to investigate whether the LFA is safe and compatible with the LC involving abdominal CO2 insufflation.

Hemodynamic and Respiratory Effect of Pediatric Urological Laparoscopic Surgery: A Retrospective Study

We investigate the impact of extraperitoneal and intraperitoneal CO2 insufflation on cardiopulmonary variables in children undergoing laparoscopic surgery. The records of 73 patients who underwent laparoscopic urological surgery between December 2000 and April 2002 were retrospectively reviewed. Data collection included respiratory rate (RR), peak airway pressure (PAP), O2 saturation, end tidal CO2 (ETCO2), heart rate, systolic and diastolic blood pressure, electrocardiogram and insufflation pressure. All variables were recorded before and after CO2 insufflation. Only patients with complete records were included in the analysis. The study included 62 participants. Of the patients 16 boys and 13 girls with a mean age +/- SD of 7.2 +/- 5.1 years underwent extraperitoneal surgeries, 14 partial or total nephrectomy and 5 pyeloplasty. Mean retroperitoneal CO2 insufflation pressure was 12.1 +/- 1.5 mm Hg and mean operative time was 3.6 +/- 1 hours. We operated on 13 children on the right and 16 on the left decubitus lateral position. Significant increase in ETCO2, RR and PAP was recorded after CO2 insufflation in the extraperitoneal group. Use of the left lateral position resulted in a significant increase in ETCO2 (37.1 +/- 3.6 vs 40 +/- 3.8, p = 0.04) after CO2 insufflation compared to the right decubitus lateral position. Transperitoneal surgery was performed in 32 boys and 1 girl with a mean age of 3.8 +/- 4.1 years for cryptorchidism (32) and attempted pyeloplasty (1). Mean intraabdominal CO2 insufflation pressure was 11 +/- 2.4 mm Hg and mean operative time was 1.7 +/- 0.8 hours. A significant increase in RR (16.5 +/- 3.1 vs 17.9 +/- 3.4, p = 0.0002) and PAP (13.2 +/- 4.8 vs 16.1 +/- 5.7, p <0.0001), and a decrease in O2 saturation (99.6 +/- 0.6 vs 98.7 +/- 7.1, p = 0.0003) and heart rate (116 +/- 19 vs 113 +/- 18, p = 0.019) were recorded after CO2 insufflation. Our study documented significant hemodynamic and respiratory changes during pediatric laparoscopic surgeries. A similar effect on the respiratory parameters was observed in both groups. Although there were no apparent complications associated with either approach, further prospective studies are warranted to confirm the effect of laparoscopic urological surgery on cardiopulmonary function in children.

Efficacy and Safety of Positive Pressure Ventilation through A ProSeal Laryngeal Mask Airway during Laparoscopic Cholecystectomy

Background: W e evaluated the efficacy and safety of positive pressure ventilation (PPV with a ProSeal laryngeal mask airway (PLMA as compared with an endotracheal tube (ETT and with a classic laryngeal mask airway (LMA during laparoscopic cholecystectomy. Methods: One hundred ASA 1 2 adults scheduled for elective laparoscopic cholecystectomy were randomly assigned to ETT LMA or PLMA. Anesthesia was induced with fentanyl 2μg/kg lidocaine 0.5 mg/kg and propofol 2 mg/kg and maintained with a continous infusion of propofol 6-12 mg/kg/h in 67% N 2O atracurium and fentanyl. ETT LMA or PLMA was placed with atracurium 0.5 mg/kg. Respiratory and hemodynamic parameters were measured before and after intraabdominal CO2 insufflation. The surgeon assessed the degree of gastric distension change using a laparoscope. R esults: Oxygen saturation end tidal CO2 inspiratory pressure expiratory tidal volume and compliance of the respiratory system were similar in the three groups. Blood pressure and heart rate were lower in the PLMA and LMA groups than in the ETT group 5 min after induction (P ＜ 0.05. Audible gas leakage occurred more so in the LMA group (48.5% than in the PLMA group (8.8%. Because of inadequate ventilation endotracheal intubation was changed in one case in the LMA group. The degrees of gastric distension change were similar in the three groups. The PLMA and LMA resulted in less coughing after removal than ETT (P ＜ 0.05. A postoperative sore throat and dysphagia were similar in the three groups but dysphonia was more frequent in the ETT group. C onclusion: During laparoscopic cholecystectomy PPV with PLMA provide more effective pulmonary ventilation than LMA and fewer side effects than ETT. (Korean J Anesthesiol 2003; 44: 739～746

Effect of laparoscopy on intra-abdominal blood flow

Surgery 2001;129:385-9.

The Effects of Intraperitoneal CO2 Insufflation and/or Reversed Trendelenburg Position on Airway Pressure and Compliance

Background: We studied the effects of intraperitoneal CO₂ insufflation and/or the reversed Trendelenburg position on airway pressure and compliance of the total respiratory system. Methods: We selected and randomly allocated eighty adults to a control group C or laparoscopy group L. Without premedication, propofol and vecuronium were injected for anesthesia, In the supine position we checked peak and plateau airway pressures, and calculated the dynamic and static compliance of the total respiratory system. We only used 10 reverse Trendelenburg position in group C, and used both 10 reverse Trendelenburg position and abdominal CO₂ insufflation in group L. Afterwards, we checked airway pressure and compliance and compared them between groups. Results: In group C, there was no change in airway pressure and compliance. But in group L, peak airway pressure (13.9 2.4 vs 21.0 ± 3.3 cmH₂O) and plateau airway pressure (11.7 ± 2.1 vs 18.9 ± 3.2 cmH₂O) were increased and dynamic compliance (47.7 ± 9.1 vs 30,6 ± 5.9 ml/cmH₂O) and static compliance (58.4 ± 12.4 vs 13.1 ± 7.3 ml/cmH₂O) of the total respiratory system were decreased. Conclusion: In a laparoscopic cholecystectomy, intraabdominal insufflation of CO₂ raises airway pressure and reduces compliance of the total respiratory system. Reverse Trendelenburg position itself does not affect airway pressure and compliance.

The Relationship Among Carbon Dioxide Pneumoperitoneum, Vasopressin Release, and Hemodynamic Changes

We assessed the role of vasopressin (VP) for the hemodynamic response to pneumoperitoneum in pigs.Four groups of anesthetized pigs were investigated. Nine pigs were intraabdominally insufflated with CO2 and eight were intraabdominally insufflated with argon; eight pigs received an IV injection of 1 mg/kg SR 49059, a VP antagonist, before CO2 insufflation; and six pigs received SR 49059 alone. Hemodynamics, plasma concentrations of VP and vasoactive hormones, and PaCO2 were measured. Data were analyzed by using analysis of variance, Student's t-test, and Mann-Whitney U-test. Five minutes after insufflation, changes in systemic vascular resistance (SVR) were significantly correlated with changes in VP (r = 0.72; P = 0.005) but not with changes in epinephrine, norepinephrine, renin activity, or PaCO2. SVR increased during CO2 insufflation but not during argon insufflation or CO2 insufflation with a preceding infusion of SR 49059. The SR 49059 injection itself resulted in increases in heart rate and cardiac output and decreases in blood pressure and SVR. We conclude that, during CO2 pneumoperitoneum in pigs, absorbed CO2 initiates a pathophysiological process that stimulates VP release. Hence, VP most likely plays a key role in the hemodynamic response to a CO2-induced pneumoperitoneum. Implications: Intraabdominal insufflation of CO2 is associated with hemodynamic and hormonal changes. Investigating CO2 and argon-insufflated pigs and using a vasopressin antagonist, we found that CO2 insufflation released vasopressin, which, in turn, induced hemodynamic perturbances. (Anesth Analg 1999;89:278-83)

The relationship among carbon dioxide pneumoperitoneum, vasopressin release, and hemodynamic changes.

We assessed the role of vasopressin (VP) for the hemodynamic response to pneumoperitoneum in pigs. Four groups of anesthetized pigs were investigated. Nine pigs were intraabdominally insufflated with CO2 and eight were intraabdominally insufflated with argon; eight pigs received an i.v. injection of 1 mg/kg SR 49059, a VP antagonist, before CO2 insufflation; and six pigs received SR 49059 alone. Hemodynamics, plasma concentrations of VP and vasoactive hormones, and Paco2 were measured. Data were analyzed by using analysis of variance, Student's t-test, and Mann-Whitney U-test. Five minutes after insufflation, changes in systemic vascular resistance (SVR) were significantly correlated with changes in VP (r = 0.72; P = 0.005) but not with changes in epinephrine, norepinephrine, renin activity, or Paco2. SVR increased during CO2 insufflation but not during argon insufflation or CO2 insufflation with a preceding infusion of SR 49059. The SR 49059 injection itself resulted in increases in heart rate and cardiac output and decreases in blood pressure and SVR. We conclude that, during CO2 pneumoperitoneum in pigs, absorbed CO2 initiates a pathophysiological process that stimulates VP release. Hence, VP most likely plays a key role in the hemodynamic response to a CO2-induced pneumoperitoneum. Intraabdominal insufflation of CO2 is associated with hemodynamic and hormonal changes. Investigating CO2 and argon-insufflated pigs and using a vasopressin antagonist, we found that CO2 insufflation released vasopressin, which, in turn, induced hemodynamic perturbances.

Intrathoracic and pulmonary blood volume during CO2-pneumoperitoneum in humans.

Induction of CO2-pneumoperitoneum may have significant effects on systemic and pulmonary haemodynamics. We hypothesized that intrathoracic (ITBV) and pulmonary blood volume (PBV) are affected during intra-abdominal CO2-insufflation, which may be pronounced by positional changes of the patient. Sixteen anaesthetized patients were studied before, during and after CO2-pneumoperitoneum for laparoscopic cholecystectomy. A dye indicator technique was used to assess ITBV and PBV. In addition, gas exchange and haemodynamics were recorded. In the supine position, induction of CO2-pneumoperitoneum had no effects on ITBV, PBV and cardiac output. Mean systemic arterial pressure increased from 10.9 +/- 1.5 kPa (82 +/- 11 mmHg) to 12.7 +/- 1.5 kPa (95 +/- 11 mmHg, P < 0.01). In the reverse Trendelenburg position ITBV decreased from 19.8 +/- 5.1 ml.kg-1 to 16.7 +/- 3.7 ml.kg-1 (P < 0.05) during CO2-insufflation, but increased to control values after 20 min. PBV decreased from 4.2 +/- 1.2 ml.kg-1 to 3.4 +/- 1.1 ml.kg (P < 0.05) and remained decreased during CO2-pneumoperitoneum. Calculated venous admixture was unchanged throughout the study. Deflation of CO2-pneumoperitoneum increased ITBV (22.4 +/- 5.2 ml.kg-1, P < 0.05) and cardiac output above control values. In anaesthetized-paralyzed patients in the reverse Trendelenburg position intra-abdominal CO2-insufflation is associated with significant alterations of ITBV and PBV. The release of CO2-pneumoperitoneum is associated with a re-distribution of blood into the thorax.

Effects of intraabdominally insufflated carbon dioxide and elevated intraabdominal pressure on splanchnic circulation: an experimental study in pigs.

Intraabdominally insufflated carbon dioxide (CO2) during laparoscopy may have a specific effect on splanchnic circulation that may be unrelated to the effects of increased intraabdominal pressure alone. Therefore, the influences of insufflation with CO2 versus air on splanchnic circulation were compared. Pigs were chronically instrumented for continuous recording of mesenteric artery, portal venous, inferior vena cava, and pulmonary arterial blood flow and portal venous pressure. After induction of anesthesia, CO2 or air was insufflated in 14 and 10 pigs, respectively. With the pigs in the supine position, intraabdominal pressure was increased in steps of 4 mmHg up to 24 mmHg by graded gas insufflation. During air insufflation, mesenteric artery vascular resistance was unchanged, whereas mesenteric arterial blood flow decreased with increasing intraabdominal pressure. Shortly after CO2 insufflation to an intraabdominal pressure of 4 mmHg, mean arterial pressure, mesenteric arterial blood flow, and mesenteric arterial vascular resistance were increased by 21%, 12% and 9%, respectively. Subsequently, with the onset of CO2 resorption in the third minute, mean arterial pressure declined to baseline values and mesenteric arterial vascular resistance declined to 85% of baseline values, whereas mesenteric arterial blood flow continued to increase to a maximum of 24% higher than baseline values. At steady-state conditions during CO2 insufflation, mesenteric arterial blood flow was increased up to an intraabdominal pressure 16 mmHg but decreased at higher intraabdominal pressures. In contrast to air insufflation, intraabdominal insufflation of CO2 resulted in a moderate splanchnic hyperemia at an intraabdominal pressure < or = 12 mmHg. At higher intraabdominal pressure values, pressure-induced changes became more important than the type of gas used.

Arterial to End-tidal Gradients in Pregnant Subjects

Department of Veterinary Anesthesiology, Radiology, and Surgery, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon SK S7N 5B4, Canada.In Reply:-We appreciate the opportunity to respond to the letters by Steinbrook et al. and Shankar et al.Answering the letter by Steinbrook et al., case reports [1–7] of laparoscopic procedures during pregnancy with good outcomes were published previous to our study. Also, papers warning against the indiscriminate use of CO2pneumoperitoneum appeared in the literature. [8] It was the lack of controlled prospective studies that prompted our prospective experimental study. [9]In our animal model, we demonstrated a large and variable PaCO sub 2 -ETCO2gradient using direct measurement methods, whereas Steinbrook et al. did not attempt to directly evaluate the adequacy of ventilation during their procedures. It has been shown that the use of ETCO2to monitor ventilation in this group of patients might be inaccurate leading potentially to the development of respiratory acidosis. [10–11] Based on their study design and number of patients, we believe that no conclusions can be made from it to recommend against the necessity of using arterial blood gas sampling to monitor the adequacy of ventilation during laparoscopic procedures in third-trimester pregnant patients.In response to the interesting letter by Shankar et al., we agree that it would be an ideal situation to assume a constant 10 mmHg difference in PaCO2to ETCO2gradient values between insufflated and noninsufflated gravid patients. Unfortunately, we obtained PaCO2to ETCO2gradients in the range of 10–16 mmHg with ETCO2values in the range of 23–30 mmHg. This large range of values would prevent us from assuming a constant 10 mmHg gradient difference, which may lead to hypo- or hyperventilating the patient. This fact supports our recommendation of using arterial blood gas sampling to accurately monitor adequate ventilation in this group of patients.The work by Shankar et al. [12–13] merits recognition as they provide an interesting piece of information regarding cardiovascular physiology of late pregnancy and in the early postpartum period in anesthetized patients. However, there are physiologic differences when CO sub 2 pneumoperitoneum is induced, and therefore Shankar et al.'s results are difficult to apply to our study.With reference to the second point, in our study, ventilation was controlled as necessary to maintain maternal normocarbia by increasing tidal volume. Changes in respiratory rate were not significantly different between study groups, and we did not observe zero or negative PaCO2to ETCO2differences, which could indicate a large mismatch of ventilation-perfusion. In addition, we do not know the extent of CO2absorbed from the peritoneal cavity and its contribution to ETCO2measurement. Despite that, the PaCO2to ETCO2difference remained significantly larger in the insufflated group. It is our impression that the magnitude of arterial CO2changes are great enough to raise a concern regarding the use of noninvasive methods to monitor ventilation.We cannot answer precisely what happens in the alveoli during ventilation of patients undergoing intraabdominal CO2insufflation, but the results of our study strongly suggest a large and unpredictable difference between PaCO2and end-tidal CO2values; thereto our recommendation of monitoring PaCO2by direct methods.Addressing the third point, despite the disadvantages of using animal models with regards to their applicability to humans, they help us to understand and to obtain vistas and ideas of the mechanisms of biological operation. Naturally, results from animal models must always be interpreted with caution in lieu of physiologic differences between species. Nonetheless, the sheep model has been used in obstetric research for decades and has been accepted by the scientific community. However, a well-conducted clinical investigation in humans is still necessary to support our results.Antonio M. Cruz, D.V.M.Lesley-Ann Crone, M.D.Lucy C. Southerland, M.D.Tanya Duke, D.V.M.James G. Ferguson, D.V.M.Department of Veterinary Anesthesiology, Radiology, and Surgery; Western College of Veterinary Medicine; University of Saskatchewan; 52 Campus Drive; Saskatoon SK S7N 5B4; Canada(Accepted for publication August 24, 1997.)

Effects of carbon dioxide insufflation combined with changes in body position on blood gas and acid-base status in anesthetized llamas (Llama glama).

To study the combined effects of intra-abdominal CO2 insufflation with changes in body position during laparoscopy in xylazine-ketamine-halothane anesthetized llamas. Prospective, controlled study. Nine castrated, male llamas weighing 114 +/- 23 kg, 3 to 13 years old. Three llamas (preliminary study [PS] group) were used to study the effect of right, lateral, dorsal, and left lateral recumbency on gas exchange and acid-base status. The other six (experimental study [ES] group) were used to study the combined effects of changes in body position and CO2 insufflation to an intraabdominal pressure of 10 to 12 mm Hg. Heart rate, respiratory rate, and indirect arterial blood pressures (systolic [SAP], mean [MAP], and diastolic [DAP]) were recorded every 5 minutes during anesthesia. Arterial blood gases (PaO2 and PaCO2) and acid-base status (pHa and HCO3-) were measured immediately after induction of anesthesia and before each change of position. In the PS group, significant decreases in SAP, MAP and PaCO2 and increases in PaO2 and pHa were observed when the llamas were turned from right lateral to dorsal recumbency. Values for HCO3- were lower than the postinduction values, but they remained unaffected by the changes in position. In the ES group, values for MAP were significantly lower when the llamas were placed in dorsal and left lateral recumbency than those observed during right lateral recumbency. Arterial O2 tension during right lateral recumbency was lower but returned to preinsufflation values when the llamas were placed in the dorsal position. All llamas recovered uneventfully within 30 minutes after termination of anesthesia. Insufflation of CO2 and changing body position induce minor and transient changes in cardiovascular and respiratory function. Laparoscopy with mild intra-abdominal CO2 insufflation (10 to 12 mm Hg) can be used safely in spontaneously breathing llamas anesthetized with xylazine, ketamine, and halothane.

Retroperitoneal and Intraperitoneal CO2Insufflation Have Markedly Different Cardiovascular Effects

Both retroperitoneoscopic and laparoscopic surgical approaches to kidney and adrenal gland have been reported but their cardiopulmonary pathophysiology has been incompletely characterized. To test the hypothesis that these approaches have markedly different impact on the circulatory and respiratory systems, we assessed at similar insufflation pressures alterations in cardiovascular and respiratory variables during retroperitoneal and intraperitoneal CO2insufflation. Eighteen healthy, anesthetized (propofol, alfentanil, vecuronium), mechanically ventilated pigs were randomly instrumented for either retroperitoneoscopic (n= 9) or laparoscopic (n= 9) surgery. After CO2insufflation cardiovascular and respiratory variables were measured at four cavity pressures (baseline, 10, 15, and 20 mmHg), while end-expiratory CO2tension was maintained by adjusting tidal volume. Data were analyzed for both insufflation-pressure-dependent and group effects by one-way and two-way ANOVA for repeated measurements, respectively, followed by Newman–Keuls post hoc test (P< 0.05). Cardiac output, mean arterial, pulmonary artery, central venous, and femoral venous pressures increased significantly in both groups in an insufflation-pressure-dependent fashion. However, changes in cardiac output (P< 0.001), pulmonary artery (P< 0.007), central venous (P< 0.001), and iliac venous pressures (P< 0.001) for the same insufflation pressure were markedly and significantly greater with intraperitoneal than retroperitoneal CO2insufflation. Most important, intraperitoneal unlike retroperitoneal insufflation induced a marked inferior vena caval pressure gradient (8.9 ± 1.1 mmHg vs 1.0 ± 0.5 mmHg,P< 0.00001). While both retroperitoneal and intraperitoneal CO2insufflation required increased tidal volumes to adjust end-tidal CO2tension to baseline, intraperitoneal CO2insufflation resulted in a significantly greater increase of mixed venous and arterial carbon dioxide tensions (P< 0.007) even at similar insufflation pressures. Furthermore, significantly greater peak airway pressures (P= 0.018) were required with intraperitoneal than with retroperitoneal insufflation to administer the same tidal volume, indicating a greater decrease in quasi-static compliance with intraperitoneal insufflation (P= 0.0436). Thus, (i) cardiovascular and respiratory changes are much less during retroperitoneal than intraperitoneal CO2insufflation, even at the same insufflation pressures, and (ii) retroperitoneal CO2insufflation unlike intraabdominal CO2insufflation does not induce an inferior vena caval pressure gradient and hence does not appear to impair systemic lower body venous return up to insufflation pressures of 20 mmHg.

The Effects of Neuromuscular Block on Peak Airway Pressure and Abdominal Elastance During Pneumoperitoneum

Administration of muscle relaxants is considered as necessary to prevent high intraabdominal and peak inspiratory pressures induced by pneumoperitoneum during laparoscopy.In the present study, we hypothesized that neuromuscular block does not alter pulmonary or abdominal elastic properties in pigs receiving general anesthesia. To test this hypothesis, changes in peak airway pressure and abdominal elastance during intraabdominal CO2 insufflation from 0 to 15 mm Hg were recorded in anesthetized pigs, with or without muscle relaxants. A 100% increase in peak inspiratory airway pressure was obtained. This was unaffected by neuromuscular block induced by atracurium (13.2 +/- 5.0 mm Hg vs 25.0 +/- 4.8 mm Hg for the control group and 12.6 +/- 5.0 mm Hg vs 23.5 +/- 6.2 mm Hg for the paralyzed group). Abdominal pressure/volume relationships were independent of muscle relaxant administration (calculated elastance was 3.98 +/- 1.56 mm Hg/L without muscle relaxant vs 3.86 +/- 1.37 mm Hg/L in the atracurium group). We conclude that high peak inspiratory airway pressures and intraabdominal pressures during laparoscopy are not affected by neuromuscular block. These findings also question the necessity of muscle relaxants in clinical anesthetic practice during laparoscopic surgery. (Anesth Analg 1996;82:525-7)

Augmented arterial to end-tidal PCO2 difference during laparoscopic CO2 insufflation in man.

Acid-base status of the blood and tissue fluids and pulmonary gas exchange were continuously observed during intra-abdominal CO2 insufflation for 2 h in 8 paralyzed and artificially ventilated patients who underwent laparoscopic cholecystectomy or resection of the sigmoid colon. Carbon dioxide pressure in the arterial and mixed venous blood as well as in end-tidal air started to increase already at 5 min CO2 insufflation. On the other hand, appreciable elevation in VCO2 and tissue PCO2 (PTCO2) was noted only after 15 min. In vivo buffer value (beta) was well within the normal physiological range at 5 min and gradually declined up to 2 h. These observations indicated that chemical buffering to CO2 and redistribution of buffer base among the blood and tissue fluids were slowly developed during entire period of observation. In reflecting these experimental findings, arterial to end-tidal PCO2 difference (a-ADCO2) and respiratory gas exchange ratio (R) were promptly and significantly increased at 5 min and maintained slow increment up to 2 h. We conclude that these profiles of a-ADCO2 and R can be explained by initially rapid and subsequently slow augmentation in ventilation-perfusion ratio (VA/Q) during the specific type of respiratory acidosis elicited in this study.

Ventilatory Effects of Laparoscopy Under Epidural Anesthesia

This study evaluates the respiratory effects of laparoscopy under epidural anesthesia in seven female patients (ASA physical status I) scheduled for a gamete intrafallopian transfer procedure. Epidural anesthesia was performed with 15-18 mL of 1.5% plain lidocaine using a catheter inserted at the L3-4 level. The upper level of analgesia to pinprick was measured 20 min after lidocaine injection. Ventilatory measurements and arterial blood gas analyses were performed (a) preoperatively, in the horizontal supine position with a T7-9 level of analgesia; (b) in the 20 degrees Trendelenburg position with a T2-5 level of analgesia; (c) during intraabdominal insufflation of CO2 through the laparoscope; and (d) after CO2 exsufflation by manual compression of the abdomen before removal of the laparoscope while in the horizontal position. On-line measurements of VO2, VCO2, VE, VT, F, and PETCO2 were made using a Beckman metabolic cart, while the patients breathed room air through an anesthetic face mask. No significant changes in the ventilatory variables were observed in the Trendelenburg position. In contrast, CO2 insufflation significantly increased VE (from 9.1 +/- 1.0 L/min to 11.8 +/- 2.6 L/min, mean +/- SD), and F (from 16.9 +/- 1.9 breaths/min to 23.1 +/- 3.3 breaths/min, mean +/- SD), whereas VCO2 remained unchanged. PaCO2 remained constant throughout the study. These results suggest that epidural anesthesia may be a safe alternative to general anesthesia for outpatient laparoscopy, as it is not associated with ventilatory depression.

VENTILATORY EFFECTS OF LAPAROSCOPY UNDER EPIDURAL ANESTHESIA

This study evaluates the respiratory effects of laparoscopy under epidural anesthesia in seven female patients (ASA physical status I) scheduled for a gamete intrafallopian transfer procedure. Epidural anesthesia was performed with 15-18 mL of 1.5% plain lidocaine using a catheter inserted at the L3-4 level. The upper level of analgesia to pinprick was measured 20 min after lidocaine injection. Ventilatory measurements and arterial blood gas analyses were performed (a) preoperatively, in the horizontal supine position with a T7-9 level of analgesia; (b) in the 20 degrees Trendelenburg position with a T2-5 level of analgesia; (c) during intraabdominal insufflation of CO2 through the laparoscope; and (d) after CO2 exsufflation by manual compression of the abdomen before removal of the laparoscope while in the horizontal position. On-line measurements of VO2, VCO2, VE, VT, F, and PETCO2 were made using a Beckman metabolic cart, while the patients breathed room air through an anesthetic face mask. No significant changes in the ventilatory variables were observed in the Trendelenburg position. In contrast, CO2 insufflation significantly increased VE (from 9.1 +/- 1.0 L/min to 11.8 +/- 2.6 L/min, mean +/- SD), and F (from 16.9 +/- 1.9 breaths/min to 23.1 +/- 3.3 breaths/min, mean +/- SD), whereas VCO2 remained unchanged. PaCO2 remained constant throughout the study. These results suggest that epidural anesthesia may be a safe alternative to general anesthesia for outpatient laparoscopy, as it is not associated with ventilatory depression.