A comparative analysis of the effects of sevoflurane and propofol on cerebral oxygenation during steep Trendelenburg position and pneumoperitoneum for robotic-assisted laparoscopic prostatectomy

Purpose

Steep Trendelenburg position and pneumoperitoneum during robotic-assisted laparoscopic prostatectomy (RALP) increase intracranial pressure (ICP) and may alter cerebral blood flow (CBF) and oxygenation. Volatile anesthetics and propofol have different effects on ICP, CBF, and cerebral metabolic rate and may have different impact on cerebral oxygenation during RALP. In this study, we measured jugular venous bulb oxygenation (SjO₂) and regional oxygen saturation (SctO₂) in patients undergoing RALP to evaluate cerebral oxygenation and compared the effects of sevoflurane and propofol. We also verified whether SctO₂ may be an alternative to SjO₂.

Methods

Fifty patients scheduled for RALP were randomly assigned to undergo sevoflurane (group S) or propofol (group P) anesthesia. SjO₂, SctO₂, mean arterial pressure (MAP), heart rate (HR), cardiac index (CI), central venous pressure (CVP), partial pressures of arterial oxygen (PaO₂) and carbon dioxide (PaCO₂), hemoglobin concentration (Hb), Bispectral Index (BIS) and nasopharyngeal temperature (BT) were recorded 5 min before surgery commencement, 5 min after pneumoperitoneum, 5, 30, 60, 90, and 120 min after pneumoperitoneum in a Trendelenburg position, and after desufflation in a supine position.

Results

SjO₂ was significantly higher in group S than in group P at all measurement points [group S vs. group P: 77 % (11) vs. 65 % (13), mean of all measurement points (1SD); p < 0.01]. Linear regression analysis (β = 0.106; r ² = 0.065; p = 0.004) shows a weak relationship between SjO₂ and SctO₂.

Conclusions

Sevoflurane maintains higher SjO₂ levels than propofol during RALP. SctO₂ does not accurately reflect SjO₂.

     

The effect of pneumoperitoneum and Trendelenburg position on acute cerebral blood flow–carbon dioxide reactivity under sevoflurane anaesthesia

This study compared cerebral blood flow–carbon dioxide (CBF–CO₂) reactivities in the supine and modest Trendelenburg position under pnemoperitoneum during sevoflurane anaesthesia. After induction of anaesthesia in 25 patients, mechanical ventilation was adjusted to increase Paco ₂ from 4.7 (T₁) to 6.0 kPa (T₂) in the supine position, and the change in jugular bulb oxygen saturation was measured as an index of CBF. Then, after establishment of pneumoperitoneum and 30° Trendelenburg position, the CO₂ step and measurement of CBF were repeated. The CBF–CO₂ reactivity was 7.5 (3.3) %.kPa^?1 (% change in jugular bulb oxygen saturation per unit change in Paco ₂) in the supine position and 6.8 (2.3) %.kPa^?1 in the 30° Trendelenburg‐pneumoperitoneum condition (p = 0.086). We conclude that CBF–CO₂ reactivity is unchanged by the modest Trendelenburg position under pneumoperitoneum during sevoflurane anaesthesia.     

Impact of Overweight and Pneumoperitoneum on Hemodynamics and Oxygenation during Prolonged Laparoscopic Surgery

Background Anesthesia adversely affects respiratory function and hemodynamics in obese patients. Although many studies have been performed in morbidly obese patients, data are limited concerning overweight patients [BMI 25–29.9 kg m⁻²]. The aim of this study was to evaluate the effects of prolonged pneumoperitoneum in Trendelenburg position on hemodynamics and gas exchange in normal and overweight patients. Methods We studied 15 overweight and 15 non-obese [BMI 18.5–24.9 kg m⁻²] patients who underwent totally endoscopic robot-assisted radical prostatectomy under general anesthesia with an inspired oxygen fraction of 0.5. A standardized anesthetic regimen was used, and patients were examined at standard times: after induction of anesthesia and Trendelenburg posture, every 30 minutes after establishing pneumoperitoneum, and after the release of the pneumoperitoneum with the patient still in Trendelenburg position. Results After induction of anesthesia and Trendelenburg positioning arterial oxygen pressure [P_aO₂] and alveolar-arterial difference in oxygen tension [A_aDO₂] differed significantly between both groups with lower P_aO₂ [235 ± 27 versus 164 ± 51 mmHg] and higher A_aDO₂ [149 ± 48 versus 76 ± 28 mmHg] values in overweight patients. During pneumoperitoneum, P_aO₂ transient increased above baseline values in overweight patients, whereas A_aDO₂ decreased. Hemodynamic parameters [HR, MAP, and CVP] did not differ significantly between groups. Conclusions Arterial oxygenation and A_aDO₂ are significantly impaired in overweight patients under general anesthesia in Trendelenburg posture. In overweight patients pneumoperitoneum transient reduced the impairment of arterial oxygenation and lead to a decrease in A_aDO₂. Hemodynamic parameters were not affected by body weight.     

High positive end-expiratory pressure preserves cerebral oxygen saturation during laparoscopic cholecystectomy under propofol anesthesia

Background

Positive end-expiratory pressure (PEEP) can improve respiratory mechanics during pneumoperitoneum, but may influence intracranial and cerebral perfusion pressure. This study investigated the changes in hemodynamic parameters and cerebral oxygen saturation (rSO₂) associated with 10 cmH₂O PEEP during pneumoperitoneum while undergoing laparoscopic cholecystectomy under propofol anesthesia.

Methods

Sixty patients aged 18–60 years undergoing laparoscopic cholecystectomy were randomly allocated into two groups: application of no external PEEP (ZEEP group, n = 30) or PEEP = 10 cmH₂O (PEEP group, n = 30). PEEP was applied after insufflation of CO₂. Except for the PEEP level, all other ventilator settings were identical for both groups. Hemodynamic variables, end-tidal carbon dioxide concentration (ETCO₂), ventilatory parameters, and rSO₂ were measured.

Results

There was no significant difference in rSO₂, mean arterial pressure (MAP), heart rate (HR), and ETCO₂ between the groups throughout the study. When compared with baseline, MAP, HR, and ETCO₂ increased significantly after insufflation of CO₂ in both groups, whereas rSO₂ did not change. No patient had cerebral desaturation, defined as rSO₂ <80 % of baseline or <50 % in both groups throughout the study.

Conclusion

Application of PEEP with 10 cmH₂O during CO₂ pneumoperitoneum could preserve the rSO₂ value and hemodynamic stability in patients undergoing laparoscopic cholecystectomy under propofol anesthesia.     

Effects of high positive end‐expiratory pressure on haemodynamics and cerebral oxygenation during pneumoperitoneum in the Trendelenburg position

We investigated the effects of 10 cmH₂O positive end‐expiratory pressure on cerebral haemodynamics and cerebral oxygenation in patients undergoing laparoscopic lower abdominal surgery in the 30° Trendelenburg position during desflurane anaesthesia. Twenty‐six patients were enrolled in this study. After anaesthesia induction, pneumoperitoneum was applied in Trendelenburg position. Twenty minutes later, positive end‐expiratory pressure was applied. There was no change in regional cerebral oxygen saturation (p = 0.376). Cerebral perfusion pressure decreased significantly over time (p < 0.001) and positive end‐expiratory pressure caused a further decrease in cerebral perfusion pressure (p = 0.036). The application of 10 cmH₂O positive end‐expiratory pressure during pneumoperitoneum in the Trendelenburg position preserved regional cerebral oxygen saturation, but cerebral perfusion pressure decreased significantly due to its secondary haemodynamic effects.     

Hemodynamic changes due to Trendelenburg positioning and pneumoperitoneum during laparoscopic hysterectomy

More prolonged gynecological laparoscopic operations are being performed in recent years, and a steeper head-down position is required. The early reports of hemodynamic changes during gynecologic laparoscopy are conflicting, and the effects of anesthesia, head-down tilt and pneumoperitoneum have not been clearly separated. Invasive hemodynamic monitoring was carried out in 20 female ASA Class I-II patients who underwent laparoscopic hysterectomy. Baseline measurements were made in the supine, supine-lithotomy and Trendelenburg (25 30 degrees) positions in awake patients. Measurements were repeated in the supine-lithotomy and Trendelenburg positions after induction of anesthesia, during laparoscopy 5 minutes after the beginning of peritoneal CO₂-insufflation (intra-abdominal pressure 13–16 mmHg) and at 15-minute intervals thereafter, after laparoscopy in the Trendelenburg and supine positions, after extubation and in the recovery room at 30-minute intervals. Patients received balanced general anesthesia with isoflurane in 35% O₂ in an oxygen/air mixture. End tidal PGO₂ was maintained between 4.5–4.8 kPa (33—36 mmHg) by changing the minute volume of controlled ventilation. The Trendelenburg position in awake and anesthetized patients increased pulmonary arterial pressures (PAP), central venous pressure (GVP) and pulmonary capillary wedge pressure (PCWP). These pressures increased further at the start of CO₂-insufflation, decreased towards the end of the laparoscopy and reached pre-insufflation levels after deflation of pneumoperitoneum. The mean arterial pressure (MAP) increased at the beginning of laparoscopy in comparison with the pre-laparoscopic values. Heart rate (HR) was quite stable during laparoscopy. The cardiac index (CI) decreased with anesthesia from 3.8 to 3.2 1 · min^-1 · m^-2 and further during laparoscopy to 2.7 1 · min^-1 · m^-2, returning to pre-insufflation values soon after deflation. The stroke index (SI) changed in concert with the GI changes. The right ventricular stroke work index decreased during laparoscopy more than the left ventricular stroke work index. The right atrial pressure (GVP) exceeded the PCWP more often during laparoscopy than during any other phase of the procedure. Anesthesia and the Trendelenburg position increased the CVP, PCWP and pulmonary arterial pressures and decreased cardiac output. Pneumoperitoneum increased these pressures further mostly in the beginning of the laparoscopy, and cardiac output decreased towards the end of the laparoscopy. The risk of systemic CO₂-embolus was increased during laparoscopy.     

Laparoscopic colon surgery: unreliability of end-tidal CO2 monitoring

Background: The relatively good haemodynamic and respiratory tolerance to abdominal CO₂ insufflation has mostly been observed in healthy patients during short‐lasting laparoscopic procedures. End‐tidal CO₂ pressure (PetCO₂) has been shown to be a reliable method to assess arterial CO₂ (PaCO₂) in the absence of cardio‐respiratory disease in this setting. However, no study has investigated whether PetCO₂ is accurately related to PaCO₂ 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 PaCO₂–PetCO₂ difference over time in patients undergoing laparoscopic colon surgery and to determine whether PaCO₂ is reliably assessed by PetCO₂. Methods: Forty consecutive patients (ASA I and II) scheduled for laparoscopic colon surgery were anaesthetized and ventilated to obtain a PetCO₂ between 4.0 and 5.5 kPa. After initiation of CO₂ insufflation, PaCO₂ and PetCO₂ were recorded every 30 min during surgery. Results: No complication was observed during anaesthesia. The mean arterial pressure increased significantly after CO₂ insufflation and remained steady up to the end of pneumoperitoneum. The heart rate remained stable over time. The relation between PaCO₂ and PetCO₂ was not constant among patients and increased over time within the same patients. The R² values fluctuated and did not show a constant correlation between PaCO₂ and PetCO₂. Conclusion: The correlation between PaCO₂ and PetCO₂ during laparoscopic colon surgery is inconsistent mainly due to inter‐ and intra‐individual variability.     

Effect of prolonged inspiratory time on gas exchange during robot-assisted laparoscopic urologic surgery

Background

Gas exchange disturbance may develop during urologic robotic laparoscopic surgery with the patient in a steep Trendelenburg position. This study investigated whether prolonged inspiratory time could mitigate gas exchange disturbances including hypercapnia.

Methods

In this randomized cross-over trial, 32 patients scheduled for robot-assisted urologic surgery were randomized to receive an inspiratory to expiratory time ratio (I:E) of 1:1 for the first hour of pneumoperitoneum followed by 1:2 for last period of surgery (group A, n?=?17) or I:E of 1:2 followed by 1:1 (group B, n?=?15). Arterial blood gas analysis, airway pressure and hemodynamic variables were assessed at four time points (T1: 10?min after induction of general anesthesia, T2: 1?h after the initiation of pneumoperitoneum, T3: 1?h after T2 and T4: at skin closure). The carry over effect of initial I:E was also evaluated over the next hour through arterial blood gas analysis.

Results

There was a significant decrease in partial pressure of oxygen in arterial blood (PaO₂) for both groups at T2 and T3 compared to T1 but in group B the PaO₂ at T4 was not decreased from the baseline. Partial pressure of carbon dioxide in arterial blood (PaCO₂) increased with I:E of 1:2 but did not significantly increase with I:E of 1:1; however, there were no differences in PaO₂ and PaCO₂ between the groups.

Conclusion

Decreased oxygenation by pneumoperitoneum was improved and PaCO₂ did not increase after 1 h of I:E of 1:1; however, the effect of equal ratio ventilation longer than 1 h remains to be determined. There was no carryover effect of the two different I:E ratios.

     

Increase in intraocular pressure is less with propofol than with sevoflurane during laparoscopic surgery in the steep Trendelenburg position

Background

Intraocular pressure is increased during laparoscopic surgeries performed in a steep Trendelenburg position. This study compared the effects of propofol with those of sevoflurane on intraocular pressure in patients undergoing robot-assisted laparoscopic radical prostatectomy in a 30° Trendelenburg position.

Methods

Sixty-six patients were randomly allocated to a maintenance anesthetic consisting of remifentanil and sevoflurane (Sevoflurane Group) or remifentanil and propofol (Propofol Group). Intraocular pressure (IOP) was measured at nine predefined time points, including baseline (T0), five minutes after establishing pneumoperitoneum (T2), 30 min after establishing the Trendelenburg position with pneumoperitoneum (T3), five minutes after returning to the horizontal position (T4), and immediately after tracheal extubation (T6). The primary outcome was the change in intraocular pressure from T0 to T3.

Results

The results of linear mixed model analysis showed that intraocular pressure differed between the two groups (P = 0.0039). At T3, the mean (SD) IOP was greater in the Sevoflurane Group [23.5 (4.3) mmHg] than in the Propofol Group [19.9 (3.8) mmHg] (P = 0.0019). At T2 and T6, IOP was also greater in the Sevoflurane Group than in the Propofol Group (P = 0.038 and P = 0.009, respectively). There was a statistically significant increase in intraocular pressure from baseline to T3 (pneumoperitoneum and steep Trendelenberg) in the Sevoflurane Group [6.0 (5.0) mmHg; P < 0.001] but not in the Propofol Group [2.1 (5.1) mmHg; P = 0.136]. None of the patients experienced ocular complications.

Conclusions

Intraocular pressure increases after pneumoperitoneum and the steep Trendelenburg position are established. This increase is less with propofol than with sevoflurane anesthesia. This trial was registered at ClinicalTrials.gov: NCT01744262.     

Time course of cerebrovascular autoregulation during extreme Trendelenburg position for robotic‐assisted prostatic surgery

Trendelenburg positioning in combination with pneumoperitoneum during robotic‐assisted prostatic surgery possibly impairs cerebrovascular autoregulation. If cerebrovascular autoregulation is disturbed, arterial hypertension might induce cerebral hyperaemia and brain oedema, while low arterial blood pressure can induce cerebral ischaemia. The time course of cerebrovascular autoregulation was investigated during use of the Trendelenburg position and a pneumoperitoneum for robotic‐assisted prostatic surgery using transcranial Doppler ultrasound. Cerebral blood flow velocity was correlated with arterial blood pressure and the autoregulation index (Mx) was calculated. In 23 male patients, Mx was assessed at baseline, after induction of general anaesthesia, during the Trendelenburg position (40–45°), and after repositioning. During the Trendelenburg position, Mx increased over time, indicating an impairment of cerebrovascular autoregulation. After repositioning, Mx recovered to baseline levels. It can be concluded that with longer durations of Trendelenburg position and pneumoperitoneum, cerebrovascular autoregulation deteriorates, and, therefore, blood pressure management should be adapted to avoid cerebral oedema and the duration of Trendelenburg position should be as short as possible.     

改良抬胸Trendelenburg位对腹腔镜结直肠癌根治术老年患者脑氧代谢和早期术后认知功能的影响

目的 观察改良抬胸位对腹腔镜结直肠癌根治术老年患者的脑氧代谢和早期术后认知功能的影响.方法 择期拟行腹腔镜结直肠癌根治术患者80例,年龄60～82岁,体重44～69 kg,ASA分级Ⅰ、Ⅱ级,性别不限,按随机数字表法分为2组(每组40例):M组加用定制体位垫使患者呈改良抬胸Trendelenburg体位(简称T位),T组采用T位.于常规全身麻醉插管后平卧位5 min(T1),气腹改良抬胸T位/T位即刻(T2)、30 min(T3)、60 min(T4)和90 min(T5),气腹放气平卧位15 min(T6),分别采集桡动脉和颈静脉球血样,记录血气分析、血糖、乳酸值及MAP等,计算脑动静脉氧含量差(arteriovenous O2 content difference,Ca-jv DO2)及脑葡萄糖摄取(arteriovenous O2 glucose difference,Da-jvglu)等;并于麻醉前,麻醉结束后2、6、24、48、72 h时,采用简易智能量表(mini-mental state exam,MMSE)进行认知功能评分.结果 与T1时比较,两组患者动脉血二氧化碳分压(arterial partial pressure carbon dioxide,PaCO2)在T3-6时均显著升高,MAP在T2时显著降低,两组患者在T3～5时颈静脉球血氧分压(jugular venous partial pressure oxygen,PjvO2)显著升高,T4-5时颈静脉球血氧饱合度(jugular venous oxygen saturation,SjvO2)显著升高(P＜0.05);M组MAP在T4-6时显著升高,T组在T3-6时显著升高(P＜0.05);T组在T6时SjvO2[(75±9)％]显著升高,T5时Caa-jvDO2[(5.2±1.5)％]显著下降,而颈静脉球血乳酸(jugular venous lactate,Lacjv)[(2.0±0.5) mmol/L]显著上升(P＜0.05).与T组比较,M组MAP在T4-6时上升较慢,Ca-jvDO2[(5.9±1.6)％]在T5时无明显下降,Da-jvglu气腹前后差异无统计学意义(P＞0.05),SjvO2 [(75±9)％]和Lacjv[(1.5±0.5) mmol/L]无显著上升,而PaCO2[(34±3) mmHg(1 mmHg=0.133 kPa)]在T6时显著降低(P＜0.05).与T组比较,M组麻醉结束后6、24 h时MMSE评分明显较高;与麻醉前比较,麻醉结束后2h两组MMSE评分显著降低(P＜0.05).结论 改良抬胸T位缓解了气腹后期脑氧供需失衡,麻醉结束后24 h内认知功能下降的发生率明显降低,有利于较长时间手术的安全.     

Ventilatory requirements during laparoscopic cholecystectomy

The purpose of this clinical study was to determine: (1) the increase in minute ventilation required to maintain preinsufflation arterial carbon dioxide tension (PaCO₂) during laparoscopic cholecystectomy, and (2) whether end-tidal PCO₂ (PetCO ₂) can be used as an index of PaCO₂ and, therefore, of the adequacy of minute ventilation during the pneumoperitoneum. We measured PaCO₂,PetCO ₂, expired minute volume (V_exp) standardized for body surface area (SA), airway and intra-abdominal pressure (Paw, Pabd) during general anaesthesia for laparoscopic cholecystectomy just before and 30 min after the creation of a CO₂ pneumoperitoneum in 28 healthy (ASA class 1 and 2) consenting adults. They were in the reverse Trendlenburg position (20°) with a 5° lateral tilt. Expired minute volume was increased from 3.75 (SEM ± 0.12) to 4.19 (0.15) L·min^?1·m^?2 to maintain PaCO₂ close to control levels: 38.9 (0.8) vs 40.1 (0.6) mmHg 5.19 (0.1) vs 5.35 (0.08) kPa). In most of the patients (23/28),PetCO ₂ was less than 41 mmHg with a correlation between PaCO₂ andPetCO ₂. In ten of these patients, (Pa-Pet)CO₂ was greater than the normal range. In 5/28, (Pa-Pet)CO₂ was negative. The “driving pressure” (Paw-Pabd) increased from 8.7 (1.0) to 10.4 (1.1) cm H₂O, without any correlation between the increase in Paw-Pabd and that in \(\dot Vexp\) . The results indicate the need for extra ventilatory requirement during laparoscopy and thatPetCO ₂ is an imperfect index of PaCO₂ under these circumstances.     

Comparison of volume-controlled ventilation and pressure-controlled ventilation volume guaranteed during laparoscopic surgery in Trendelenburg position

Study objectiveTo analyze the effects of pressure-controlled ventilation-volume guaranteed (PCV-VG) and volume controlled ventilation (VCV) on airway pressures and respiratory and circulatory indicators during laparoscopic surgery in Trendelenburg position.DesignProspective randomized comparative clinical study.SettingTertiary hospital.PatientsForty ASA physical status 1 and 2 patients who underwent elective laparoscopic surgery in Trendelenburg position.InterventionsPatients were randomly allocated to either VCV group (n = 20) or the PCV-VG group (n = 20). After induction of anesthesia, for both modes of ventilation, the target tidal volume (V_T) was 8 mL/kg and the respiratory rate was adjusted to avoid hypercarbia.MeasurementsThe peak and mean inspiratory pressures, dynamic compliance, exhaled V_T, oxygenation index and physiological dead space were calculated and recorded at T1, 5 minutes after induction of anesthesia in supine position, T2, 5 minutes after stabilization of pneumoperitoneum, T3 and T4, 15 and 60 minutes after 30° Trendelenburg position with pneumoperitoneum respectively.Main resultsPCV-VG group had significantly lower peak inspiratory pressure and greater dynamic compliance than VCV group (P < .001).ConclusionsIn patients who underwent laparoscopic surgery in Trendelenburg position, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.     

A prospective assessment of renal oxygenation in children undergoing laparoscopy using near-infrared spectroscopy

Background

This study was designed to determine whether a decrease in renal oxygenation occurs during CO₂ pneumoperitoneum in children with normal renal function undergoing laparoscopy.

Methods

Near infrared spectroscopy (NIRS) probes were applied to both the lateral flank (T10-L2) and lateral cerebral area of all patients with normal renal function undergoing a laparoscopic procedure. Information was recorded in 5-s intervals for 15-min before, during, and for 15-min after pneumoperitoneum insufflation and desufflation. Simultaneously, additional hemodynamic parameters (arterial saturation, mean arterial pressure, end tidal CO₂, and urine output) were recorded every 5-min. Pneumoperitoneum pressures used were: 0–1 month old, <6 mmHg; 2–12 months old, <8 mmHg; 1–2 years old, <10 mmHg, and 2–8 years old, <12 mmHg. The lowest possible pressure was used to obtain adequate vision.

Results

Twenty-nine patients were enrolled in the study. Renal regional oxygen saturation (rSO₂) did not decrease significantly between baseline (preinsufflation), insufflation, and desufflation of the pneumoperitoneum (p = 0.343). Meta-analysis of this data demonstrated a pooled weighted difference of ?1.4 (?3.5 to 0.54), confirming no significant change. A significant increase in cerebral rSO₂ occurred during the insufflation period of the CO₂ pneumoperitoneum (p = 0.001). Heart rate (F = 11.05; p < 0.001) and mean arterial pressure (MAP) (F = 19.2; p < 0.001) also increased significantly during the laparoscopy. No significant correlation was identified between fluid input and urine output during the laparoscopy (r = 0.012; p = 0.953).

Conclusions

Renal hypoxia does not occur during laparoscopic surgery in children if the minimum age-appropriate intra-abdominal pressures are used. Alternative causes must account for the oliguria and anuria demonstrated in children undergoing laparoscopy.     

Comparação entre ventilação garantida por volume controlado por pressão e ventilação controlada por volume em pacientes obesos durante cirurgia laparoscópica ginecológica na posição de Trendelenburg

Background and objectivesThe aim of this study was to investigate the efficacy of the pressure‐controlled, volume‐guaranteed (PCV‐VG) and volume‐controlled ventilation (VCV) modes for maintaining adequate airway pressures, lung compliance and oxygenation in obese patients undergoing laparoscopic hysterectomy in the Trendelenburg position.MethodsPatients (104) who underwent laparoscopic gynecologic surgery with a body mass index between 30 and 40 kg.m^-2 were randomized to receive either VCV or PCV‐VG ventilation. The tidal volume was set at 8 mL.kg^-1, with an inspired oxygen concentration of 0.4 with a Positive End‐Expiratory Pressure (PEEP) of 5 mmHg. The peak inspiratory pressure, mean inspiratory pressure, plateau pressure, driving pressure, dynamic compliance, respiratory rate, exhaled tidal volume, etCO₂, arterial blood gas analysis, heart rate and mean arterial pressure at 5 minutes after induction of anesthesia in the and at 5, 30 and 60 minutes, respectively, after pneumoperitoneum in the Trendelenburg position were recorded.ResultsThe PCV‐VG group had significantly decreased peak inspiratory pressure, mean inspiratory pressur, plateau pressure, driving pressure and increased dynamic compliance compared to the VCV group. Mean PaO₂ levels were significantly higher in the PCV‐VG group than in the VCV group at every time point after pneumoperitoneum in the Trendelenburg position.ConclusionsThe PCV‐VG mode of ventilation limited the peak inspiratory pressure, decreased the driving pressure and increased the dynamic compliance compared to VCV in obese patients undergoing laparoscopic hysterectomy. PCV‐VG may be a preferable modality to prevent barotrauma during laparoscopic surgeries in obese patients.     

The effects of elevated intraabdominal pressure, hypercarbia, and positioning on the hemodynamic responses to laparoscopic colectomy in pigs

Background: This study investigated three factors postulated to be sources of physiological stress in laparoscopic surgery: hypercarbia, elevated intraabdominal pressure, and the steep Trendelenburg position. Our research was designed to define the effects of each of these potential stressors on hemodynamic responses observed during laparoscopic colectomy in pigs. Methods: Twenty-four pigs were randomized into the following four groups, based on the method for obtaining surgical exposure while a colectomy or laparoscopic-assisted colectomy was performed: Open surgery (n = 6), CO₂ pneumoperitoneum (n = 6), Helium pneumoperitoneum (n = 6), and abdominal wall Lifter (n = 6). The animals were paralyzed with minute ventilation adjusted. All animals underwent extensive pulmonary and hemodynamic monitoring with measurements of the following parameters: RR, Vt, minute ventilation, O₂, sat, ETCO₂, PVR, HR, MAP, CO, PAP, CVP, PCWP, SV, LVSWI, DO₂, and VO₂. The laparoscopic pigs were placed in the steep Trendelenburg position during surgery. Results: The effect of a CO pneumoperitoneum was to increase PaCO₂ PVR and cause an acidemia that could not be prevented by an increase in minute ventilation. Elevated intraabdominal pressure decreased UO. Both pneumoperitoneum groups had a fourfold increase in IVCP, a measure of intraabdominal pressure. Some of this increase was due to placement into the Trendelenburg position; IVCP increased to a lesser degree in the Lifter group. The steep Trendelenburg position caused significant increases in PAP, CVP, and PCWP; however, a contributory effect of elevated intraabdominal pressure cannot be ruled out. None of these procedures had any significant effect on the HR or MAP. There was a significant increase in CO in the CO₂ and Lifter groups; however, when CO was controlled for HR effects, there was no significant effect on SV from any of these different procedures. LVSWI, DO₂, and VO₂ were not affected by any of the different exposure methods. Conclusions: The effects of laparoscopic surgery and open surgery on hemodynamic responses are minimal, and no one method is superior to another when performed in pigs that are healthy, hydrated, and hyperventilated to keep ETCO₂ <40. However, since elderly and sick patients have a lower threshold for physiologic decompensation, we can infer that the small hemodynamic changes noted in this study might become significant factors when surgery is performed on compromised patients. The finding that an abdominal wall lifting device causes the fewest metabolic and hemodynamic effects makes its use an important consideration when performing laparoscopic surgery in patients with cardiopulmonary compromise, hemodynamic instability, or any preexisting renal insufficiency.     

Hipertensión endocraneal asociada a la sedación con sevoflurano mediante el dispositivo AnaConDa®en un paciente con traumatismo craneoencefálico severo

Sedation in neurocritical patients remains a challenge as there is no drug that meets all the requirements. Since the appearance of the AnaConDa^® device, and according to the latest recommendations, sevoflurane has become an alternative for patients with brain injury. The use of AnaConDa^® produces an increase in the anatomical dead space that leads to a decrease in alveolar ventilation. If the decrease in the alveolar ventilation is not offset by an increase in minute volume, there will be an increase in PaCO₂. We report the case of a patient with severe traumatic brain injury who suffered an increase in intracranial pressure as a result of increased PaCO₂ after starting sedation with the AnaConDa^® device.     

Intraocular pressure variation during colorectal laparoscopic surgery: standard pneumoperitoneum leads to reversible elevation in intraocular pressure

Background

The potential effects of laparoscopic surgery on intra- and postoperative intraocular pressure (IOP) are not completely understood. Although prior studies have reported that pneumoperitoneum may increase IOP, it is not clear whether this increase is related to the effects of pneumoperitoneum or to the patient’s position, such as the Trendelenburg position. This study aimed to evaluate the potential fluctuations of IOP during colorectal laparoscopic surgery in two groups of patients: those with and those without Trendelenburg positioning.

Methods

For this prospective study 45- to 85-year-old patients undergoing laparoscopic colorectal surgery were enrolled after a thorough ophthalmologic assessment. The study protocol included measurement of IOP at eight different time points (before, during, and after surgery) using a contact tonometer in both eyes.

Results

The study enrolled 29 patients: 17 (58.6 %) with Trendelenburg position placement during surgery and 12 (41.4 %) without Trendelenburg positioning. The two groups did not differ in terms of gender, age, body mass index (BMI), American Society of Anesthesiology (ASA) class, or operative time. In all the patients, pneumoperitoneum induction led to a mild rise in IOP, averaging 4.1 mmHg. The patients with Trendelenburg positioning showed a greater increase than the patients without it (5.05 vs 4.23 mmHg at 45 min; p = 0.179), but IOP evaluation 48 h after surgery showed no substantial differences between the two groups. Among the 29 patients, 17 (58.6 %) showed an increase in IOP of 5 mmHg or more during surgery. A greater percentage of the patients who underwent Trendelenburg positioning showed an IOP increase of 5 mmHg or more (76.5 vs 33.3 %; p = 0.020). At the multivariate analysis, no potential predictors of increased IOP during surgery was identified.

Conclusions

Standard pneumoperitoneum (≤14 mmHg) led to mild and reversible IOP increases. A trend was observed toward a greater IOP increase in patients with Trendelenburg positioning. Thus, the patient’s position during surgery may represent a stronger risk factor for IOP increase than pneumoperitoneum-related intraabdominal pressure.     

Noninvasive control of adequate cerebral oxygenation during low-flow antegrade selective cerebral perfusion on adults and infants in the aortic arch surgery

Abstract Real‐time readings of the regional oxygen saturation (rSO₂) using near‐infrared spectroscopy (NIRS) during the aortic arch surgery can provide an early detection of perfusion or oxygenation abnormalities. Background: Aortic arch repair techniques using low‐flow antegrade selective cerebral perfusion have been standardized to a certain degree. However, some of the often‐stated beneficial effects have never been proven. Especially, the existence of an adequate continuous flow in both cerebral hemispheres during the surgical procedure still remains unclear as the monitoring of an effective perfusion remains a nonstandardized technique. Methods: Seventeen patients underwent surgical reconstruction of the aortic arch due to aortic aneurysm surgery (adult group n = 8 patients) or of the hypoplastic aortic arch due to hypoplastic left heart syndrome (HLHS) or aortic coarctation (infant group n = 9 patients) under general anesthesia and mild hypothermia (adult group 28 °C; infant group 25 °C). Mean weights were 92.75 ± 14.00 kg and 4.29 ± 1.32 kg, and mean ages were 58.25 ± 10.19 years and 55.67 ± 51.11 days in the adult group and the infant group, respectively. The cerebral O₂ saturation measurement was performed by continuous plotting of the somatic reflectance oximetry of the frontal regional tissue on both cerebral hemispheres (rSO₂, INVOS^®; Somanetics Corporation, Troy, MI, USA). Results: During low‐flow antegrade perfusion via innominate artery, continuous plots with similar values of O₂ saturation (rSO₂) in both cerebral hemispheres were observed, whereas a decrease in the rSO₂ values below the desaturation threshold correlated with a displacement or an incorrect positioning of the arterial cannula in the right subclavian artery. Conclusions: Continuous monitorization of the cerebral O₂ saturation during aortic arch surgery in adults and infants is a feasible technique to control an adequate cannula positioning and to optimize clinical outcomes avoiding neurological complications related to cerebral malperfusion.     

Effects of pneumoperitoneum and body position on the morphology of the caudal cava vein analyzed by MRI and plastinated sections

Background

Pneumoperitoneum and patient positioning are essential factors during laparoscopic surgical procedures. They cause hemodynamic and anatomical changes in several abdominal organs among which the caudal cava vein (CCV) is involved. Hemodynamic changes in this vein (decreased venous return) have been described in the porcine model, but how the vein morphology and size is affected at different abdominal levels is unknown. We sought to assess the morphological and morphometrical changes in the CCV of the pig caused by pneumoperitoneum and the reverse Trendelenburg position by in vivo magnetic resonance imaging (MRI).

Methods

Six pigs were scanned via MRI under four situations: S1, control (no pneumoperitoneum); S2, control in the reverse Trendelenburg position; S3, pneumoperitoneum (14 mmHg); and S4, pneumoperitoneum in the reverse Trendelenburg position. MRI and plastinated body sections were used to evaluate the topography, morphology and cross-sectional area of the CCV.

Results

Two portions of the CCV were differentiated: a prehepatic portion (located between the vertebral levels L1–T15) with flat and irregular morphology, and a hepatic portion (between T14–T11) that was almost rounded. The reverse Trendelenburg position caused an increase in the lumen affecting mainly the prehepatic portion, while pneumoperitoneum caused a decrease in the total vascular lumen, exerting a greater effect on the hepatic portion. The combination of both situations resulted in a further decrease in the vascular area and global morphological changes.

Conclusions

The pneumoperitoneum and reverse Trendelenburg position caused morphological and morphometrical changes in the prehepatic and hepatic portions of the CCV, which should assist in gaining a better understanding of the hemodynamic changes described in the literature.