The Safety of One, or Repeated, Vital Capacity Maneuvers During General Anesthesia

Effect of the pulmonary recruitment maneuver on pain after laparoscopic gynecological oncologic surgery: a prospective randomized trial

OBJECTIVE

To evaluate the effectiveness of the pulmonary recruitment maneuver (PRM) at the end of the operation to decrease laparoscopy-induced abdominal or shoulder pain after gynecological oncologic surgery.

METHODS

In total, 113 women undergoing laparoscopic surgery for malignant or premalignant gynecological lesions were assigned randomly to two groups: the PRM group (the patient was placed in the Trendelenburg position (30°) and the PRM, consisting of two manual pulmonary inflations to a maximum pressure of 40 cmH₂O) (n=54) and the control group (n=52). Postoperative shoulder and abdominal pain was assessed 12, 24, and 48 hours later using a visual analog scale (0-10). In addition, the incidence of post-discharge nausea and vomiting was recorded until 48 hours after discharge.

RESULTS

Postoperative shoulder pain at 12 and 24 hours was significantly less severe in the PRM group (2.2±0.5 and 2.0±0.4) than in the control group (4.0±0.5 and 3.9±0.4; both p<0.001). The PRM significantly reduced the severity of upper abdominal pain at 12 and 24 h compared with the control group (3.1±0.4 and 2.9±0.4 vs. 5.9±0.5 and 4.9±0.5; both p<0.001). The analgesic requirement during the postoperative period was similar in the two groups (control group, 78.8%; PRM group, 75.9%; p=0.719).

CONCLUSION

The PRM effectively and safely reduced postoperative shoulder and upper abdominal pain levels in patients undergoing laparoscopic gynecological oncologic surgery. Trial registry at ClinicalTrials.gov, NCT01940042.

Effect of Low-pressure Pulmonary Recruitment Maneuver on Postlaparoscopic Shoulder Pain: Randomized Controlled Trial

STUDY OBJECTIVE

Postlaparoscopic shoulder pain (PLSP) is effectively reduced by a pulmonary recruitment maneuver (PRM). The goal of this study is to assess the efficacy of a PRM using maximal inspiratory pressure of 30 cm H₂O, which is lower than previously studied pressure for reducing PLSP.

DESIGN

Randomized controlled trial.

SETTING

University hospital.

PATIENTS

Eighty-four patients who were undergoing elective gynecologic laparoscopy.

INTERVENTIONS

Patients were randomly assigned to the control (n = 42) or the PRM (n = 42) group.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the intensity of the shoulder pain using the visual analog scale (VAS). The VAS score of shoulder pain (median [interquartile range]) was significantly lower in the PRM group than in the control group at 24 hours (0 [0-0] vs 1.5 [0-4.0], p <.001) and 48 hours (0 [0-0] vs 1.0 [0-2.0], p <.001) after surgery. Other variables, including surgical pain score and vital signs, were similar between the 2 groups.

CONCLUSION

The PRM with 30 cm H₂O can be a simple method to reduce PLSP. Therefore, it would be helpful to perform the PRM with 30 cm H₂O routinely.

Evaluation of lung recruitment maneuvers in acute respiratory distress syndrome using computer simulation

Introduction

Direct comparison of the relative efficacy of different recruitment maneuvers (RMs) for patients with acute respiratory distress syndrome (ARDS) via clinical trials is difficult, due to the heterogeneity of patient populations and disease states, as well as a variety of practical issues. There is also significant uncertainty regarding the minimum values of positive end-expiratory pressure (PEEP) required to ensure maintenance of effective lung recruitment using RMs. We used patient-specific computational simulation to analyze how three different RMs act to improve physiological responses, and investigate how different levels of PEEP contribute to maintaining effective lung recruitment.

Methods

We conducted experiments on five ‘virtual’ ARDS patients using a computational simulator that reproduces static and dynamic features of a multivariable clinical dataset on the responses of individual ARDS patients to a range of ventilator inputs. Three recruitment maneuvers (sustained inflation (SI), maximal recruitment strategy (MRS) followed by a titrated PEEP, and prolonged recruitment maneuver (PRM)) were implemented and evaluated for a range of different pressure settings.

Results

All maneuvers demonstrated improvements in gas exchange, but the extent and duration of improvement varied significantly, as did the observed mechanism of operation. Maintaining adequate post-RM levels of PEEP was seen to be crucial in avoiding cliff-edge type re-collapse of alveolar units for all maneuvers. For all five patients, the MRS exhibited the most prolonged improvement in oxygenation, and we found that a PEEP setting of 35 cm H₂O with a fixed driving pressure of 15 cm H₂O (above PEEP) was sufficient to achieve 95% recruitment. Subsequently, we found that PEEP titrated to a value of 16 cm H₂O was able to maintain 95% recruitment in all five patients.

Conclusions

There appears to be significant scope for reducing the peak levels of PEEP originally specified in the MRS and hence to avoid exposing the lung to unnecessarily high pressures. More generally, our study highlights the huge potential of computer simulation to assist in evaluating the efficacy of different recruitment maneuvers, in understanding their modes of operation, in optimizing RMs for individual patients, and in supporting clinicians in the rational design of improved treatment strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0723-6) contains supplementary material, which is available to authorized users.

Effects of inspired oxygen concentration on ventilation, ventilatory rhythm, and gas exchange in isoflurane-anesthetized horses

OBJECTIVE

To compare the effects of 2 fractions of inspired oxygen, 50% and > 95%, on ventilation, ventilatory rhythm, and gas exchange in isoflurane-anesthetized horses.

ANIMALS

8 healthy adult horses.

PROCEDURES

In a crossover study design, horses were assigned to undergo each of 2 anesthetic sessions in random order, with 1 week separating the sessions. In each session, horses were sedated with xylazine hydrochloride (1.0 mg/kg, IV) and anesthesia was induced via IV administration of diazepam (0.05 mg/kg) and ketamine (2.2 mg/kg) Anesthesia was subsequently maintained with isoflurane in 50% or > 95% oxygen for 90 minutes. Measurements obtained during anesthesia included inspiratory and expiratory peak flow and duration, tidal volume, respiratory frequency, end-tidal CO(2) concentration, mixed expired partial pressures of CO(2) and O(2), PaO(2), PaCO(2), blood pH, arterial O(2) saturation, heart rate, and arterial blood pressure. Calculated values included the alveolar partial pressure of oxygen, alveolar-to-arterial oxygen tension gradient (PaO(2) - PaO(2)), rate of change of PAO(2) - PaO(2), and physiologic dead space ratio. Ventilatory rhythm, based on respiratory rate and duration of apnea, was continuously observed and recorded.

RESULTS

Use of the lower inspired oxygen fraction of 50% resulted in a lower arterial oxygen saturation and PaO(2) than did use of the higher fraction. No significant difference in PaCO(2), rate of change of PAO(2) - PaO(2), ventilatory rhythm, or other measured variables was observed between the 2 sessions.

CONCLUSION AND CLINICAL RELEVANCE

Use of 50% inspired oxygen did not improve the ventilatory rhythm or gas exchange and increased the risk of hypoxemia in spontaneously breathing horses during isoflurane anesthesia. Use of both inspired oxygen fractions requires adequate monitoring and the capacity for mechanical ventilation.

Lung function after total intravenous anaesthesia or balanced anaesthesia with sevoflurane

BACKGROUND

We investigated the effects of total i.v. anaesthesia (TIVA) and balanced anaesthesia (BAL) with sevoflurane on postoperative lung function in patients undergoing surgery in the prone position.

METHODS

Sixty patients, aged 21-60 yr, undergoing elective lumbar disc surgery in the prone position were randomly allocated to undergo TIVA (propofol-remifentanil) or BAL (fentanyl-nitrous oxide-sevoflurane). Forced vital capacity (FVC), forced expiratory volume in 1 s, mid-expiratory flow (MEF 25-75), and peak expiratory flow were measured before and after general anaesthesia.

RESULTS

Both groups were similar with respect to patient characteristic data and preoperative lung function parameters. Irrespective of the type of anaesthesia administered, lung function parameters decreased after operation, with the decrease in FVC being greater after TIVA than after BAL with sevoflurane.

CONCLUSIONS

In patients emerging from general anaesthesia, postoperative reduction in FVC is greater after TIVA than after BAL with sevoflurane.

Intraoperative ventilatory strategies for prevention of pulmonary atelectasis in obese patients undergoing laparoscopic bariatric surgery

BACKGROUND

Atelectasis occurs regularly after induction of general anesthesia, persists postoperatively, and may contribute to significant postoperative morbidity and additional health care costs. Laparoscopic surgery has been reported to be associated with an increased incidence of postoperative atelectasis. It has been shown that during general anesthesia, obese patients have a greater risk of atelectasis than nonobese patients. Preventing atelectasis is important for all patients but is especially important when caring for obese patients.

METHODS

We randomly allocated 66 adult obese patients with a body mass index between 30 and 50 kg/m(2) scheduled to undergo laparoscopic bariatric surgery into 3 groups. According to the recruitment maneuver used, the zero end-expiratory pressure (ZEEP) group (n = 22) received the vital capacity maneuver (VCM) maintained for 7-8 s applied immediately after intubation plus ZEEP; the positive end-expiratory pressure (PEEP) 5 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 5 cm H(2)O of PEEP; and the PEEP 10 group (n = 22) received the VCM maintained for 7-8 s applied immediately after intubation plus 10 cm H(2)O of PEEP. All other variables (e.g., anesthetic and surgical techniques) were the same for all patients. Heart rate, noninvasive mean arterial blood pressure, arterial oxygen saturation, and alveolar-arterial Pao(2) gradient (A-a Pao(2)) were measured intraoperatively and postoperatively in the postanesthesia care unit (PACU). Length of stay in the PACU and the use of a nonrebreathing O(2) mask (100% Fio(2)) or reintubation were also recorded. A computed tomographic scan of the chest was performed preoperatively and postoperatively after discharge from the PACU to evaluate lung atelectasis.

RESULTS

Patients in the PEEP 10 group had better oxygenation both intraoperatively and postoperatively in the PACU, lower atelectasis score on chest computed tomographic scan, and less postoperative pulmonary complications than the ZEEP and PEEP 5 groups. There was no evidence of barotrauma in any patient in the 3 study groups.

CONCLUSIONS

Intraoperative alveolar recruitment with a VCM followed by PEEP 10 cm H(2)O is effective at preventing lung atelectasis and is associated with better oxygenation, shorter PACU stay, and fewer pulmonary complications in the postoperative period in obese patients undergoing laparoscopic bariatric surgery.

Inhomogeneity of lung parenchyma during the open lung strategy: a computed tomography scan study

RATIONALE

The open lung strategy aims at reopening (recruitment) of nonaerated lung areas in patients with acute respiratory distress syndrome, avoiding tidal alveolar hyperinflation in the limited area of normally aerated tissue (baby lung).

OBJECTIVES

We tested the hypothesis that recruited lung areas do not resume elastic properties of adjacent baby lung.

METHODS

Twenty-five anesthetized, mechanically ventilated pigs were studied. Four lung-healthy pigs served as controls and the remaining 21 were divided into three groups (n = 7 each) in which lung injury was produced by surfactant lavage, lipopolysaccharide infusion, or hydrochloride inhalation. Computed tomography scans, respiratory mechanics, and gas exchange parameters were recorded under three conditions: at baseline, during lung recruitment maneuver, and at end-expiration and end-inspiration when ventilating after an open lung protocol.

MEASUREMENTS AND MAIN RESULTS

During recruitment maneuver and open lung protocol, the gas volume entering the insufficiently aerated compartment was 96% (75-117%) and 48% (41-63%) (median [interquartile range]) of the functional residual capacity measured before and at zero end-expiratory pressure, respectively. Nonetheless, the volume of hyperinflated lung increased during both recruitment maneuver (by 1-28% of total lung volume; P < 0.01) and open lung protocol ventilation at end-inspiration (by 1-15% of total lung volume; P < 0.01). Regional elastance of recruited lung tissue was consistently higher than that of the baby lung regardless of the ARDS model (P < 0.01).

CONCLUSIONS

Alveolar recruitment is not protective against hyperinflation of the baby lung because lung parenchyma is inhomogeneous during ventilation with the open lung strategy.

A recruitment breath manoeuvre directly after endotracheal suction improves lung function: an experimental study in pigs

BACKGROUND

Atelectasis occurs after a well performed endotracheal suction. Clinical studies have shown that recruitment manoeuvres added after endotracheal suction during mechanical ventilation restore lung function. Repetitive lung over-distension is, however, harmful for the lung, and the effects of adding a larger breath, recruitment breath, directly after repeated endotracheal suction were therefore investigated.

METHODS

Twelve healthy anaesthetized pigs were randomized into two groups: one without and one with a recruitment breath manoeuvre (RBM), i.e. a breath 15 cmH(2)O above inspiratory pressure for 10 s during pressure-controlled ventilation. The pigs were suctioned every hour for 4 hours with an open suction system.

RESULTS

At the end of the study there was a statistically significant difference between the group given RBM and that without with respect to PaCO(2), tidal volume (V(T)), and compliance (Crs). Without RBM, the PaCO(2) increased from 4.6+/-0.4 to 6.1+/-1.5 kPa, V(T) decreased from 345+/-39 to 247+/-71 mL, and Crs decreased from 28+/-6 to 18+/-5 mL/cmH(2)O. There was no change in PaCO(2) or Crs when a RBM was given. Morphological analysis revealed no differences in aeration of apical and central lung parenchyma. In the basal lung parenchyma there were, however, greater areas with normal lung parenchyma and less atelectasis after RBM.

CONCLUSIONS

Atelectasis created by endotracheal suction can be opened by inflating the lung for a short duration with low pressure, without over-distension, immediately after suction.

A simple clinical maneuver to reduce laparoscopy-induced shoulder pain: a randomized controlled trial

OBJECTIVE

To estimate the efficacy of a simple clinical maneuver that facilitates removal of residual abdominal carbon dioxide (CO2) after laparoscopic surgery to reduce shoulder pain.

METHODS

A total of 116 female outpatients who were scheduled for elective gynecologic laparoscopic surgery were randomly allocated to either the current standard (control group) or to additional efforts to remove residual CO2 at the end of surgery. In the control group, CO2 was removed by passive deflation of the abdominal cavity through the cannula. In the intervention group, CO2 was removed by means of Trendelenburg position (30 degrees) and a pulmonary recruitment maneuver consisting of five manual inflations of the lung. Postoperative shoulder pain was assessed before discharge and 12, 24, 36, and 48 hours later using a visual analog scale (VAS, 0-100). In addition, positional characteristics of the shoulder pain and incidence of postdischarge nausea and vomiting were recorded until 48 hours after discharge.

RESULTS

Pain scores in the control and intervention groups were 30.3+/-4.5 compared with 15.6+/-3.0, 25.7+/-4.7 compared with 10.8+/-2.4, and 21.7+/-4.3 compared with 9.1+/-2.5 at 12, 24 and 36 hours after discharge, respectively (all P<.05). The intervention reduced positional pain from 63% to 31% (P<.05) and the incidence of postoperative nausea and vomiting from 56.5% to 20.4% (P<.001).

CONCLUSION

This simple clinical maneuver at the end of surgery reduced shoulder pain as well as postoperative nausea and vomiting after laparoscopic surgery by more than half.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, ClinicalTrials.gov, NCT00575237

LEVEL OF EVIDENCE

I.

The effect of increased FIO(2) before tracheal extubation on postoperative atelectasis

General anesthesia promotes pulmonary atelectasis, which can be eliminated by a vital capacity (VC) maneuver (inflation of the lungs to 40 cm H(2)O for 15 s). High-inspired oxygen concentration favors recurrence of atelectasis. Therefore, 100% oxygen before tracheal extubation may contribute to atelectasis. To evaluate whether the use of 100% oxygen before extubation increases the amount of postoperative atelectasis, we studied 30 adults scheduled for elective surgery of the extremities. Ten minutes before the presumed end of surgery, patients were randomly assigned to (a) a fraction of inspired oxygen (FIO(2)) = 1.0 (n = 10), (b) VC maneuver + FIO(2) = 1.0 (n = 10), or (c) VC maneuver + FIO(2) = 0.4 (n = 10). The amount of atelectasis was measured by computed tomography scan, and oxygenation was studied by arterial blood gas analysis. Data were analyzed by one-way analysis of variance with Bonferroni correction. Results are presented as mean +/- SD; P < 0.05 was considered significant. In the VC maneuver + FIO(2) = 0.4 group, postoperative atelectasis was smaller (2.6% +/- 1.1% of total lung surface, P < 0.05) than in the FIO(2) = 1.0 group (8.3% +/- 6.2%) and in the VC maneuver + FIO(2) = 1.0 group (6.8% +/- 3.4%). Oxygen 100% at the end of general anesthesia promotes postoperative atelectasis. A safety margin in terms of oxygenation during tracheal extubation is essential, and further studies should therefore evaluate whether atelectasis formation could be prevented despite the use of 100% oxygen.

IMPLICATIONS

For safety reasons, it is common to ventilate patients with 100% oxygen before tracheal extubation. This study demonstrates that this practice favors postoperative atelectasis.