The Effect of the Prone Position on Pulmonary Mechanics Is Frame-Dependent

Outcomes of a Single Transverse Chest Roll for Prone Positioning Technique During Percutaneous Nephrolithotomy

OBJECTIVE

To compare anesthetic parameters using a novel prone single transverse chest roll technique (STR) to the standard thoraco-pelvic dual transverse roll technique (DTR).

METHODS

A retrospective review of 441 patients who underwent PCNL between 2018 and 2022 was performed. A total of 4 surgeons were included-surgeon 1 utilized the STR technique while surgeons 2, 3, and 4 used the DTR technique. Anesthetic parameters including end-tidal CO2 (ETCO2), mean arterial pressure (MAP), peak airway pressure (Ppeak), plateau airway pressure (Pplat), positive end-expiratory pressure (PEEP), oxygen saturation (SpO2), and tidal volume (TV) were compared between both groups at 0 (supine), 15-, 30-, and 60-minute post-intubation intervals. Mixed effects regression models with interaction and pairwise comparisons were made between both groups (P <.05).

RESULTS

A total of 581 PCNLs were performed with 199 using STR and 382 using DTR. Surgery duration, ASA class, and age were similar amongst the STR and DTR groups. Estimated blood loss (59cc vs 83cc, P = .007) and length of stay (77 hrs vs 163 hrs, P = <.001) was significantly lower in the STR group. There was a significantly lower Ppeak, Pplat and TV in the STR compared to DTR group at 0, 15, 30, and 60 minutes (P <.001).

CONCLUSION

Usage of a single transverse chest roll during prone PCNL appears to be a safe positioning method. STR patients had lower Ppeak and Pplat at all time points, which has been shown to be predictive of lower blood loss.

Comparison of volume-controlled ventilation, pressure-controlled ventilation and pressure-controlled ventilation-volume guaranteed in infants and young children in the prone position: A prospective randomized study

STUDY OBJECTIVE

To explore if the pressure-controlled ventilation (PCV) and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes are superior to volume-controlled ventilation (VCV) in optimizing intraoperative respiratory mechanics in infants and young children in the prone position.

DESIGN

A single-center prospective randomized study.

SETTING

Children's Hospital, Zhejiang University School of Medicine.

PATIENTS

Pediatric patients aged 1 month to 3 years undergoing elective spinal cord detethering surgery.

INTERVENTIONS

Patients were randomly allocated to the VCV group, PCV group and PCV-VG group. The target tidal volume (VT) was 8 mL/kg and the respiratory rate (RR) was adjusted to maintain a constant end tidal CO2.

MEASUREMENTS

The primary outcome was intraoperative peak airway pressure (Ppeak). Secondary outcomes included other respiratory and ventilation variables, gas exchange values, serum lung injury biomarkers concentration, hemodynamic parameters and postoperative respiratory complications.

MAIN RESULTS

A total of 120 patients were included in the final analysis (40 in each group). The VCV group showed higher Ppeak at T2 (10 min after prone positioning) and T3 (30 min after prone positioning) than the PCV and PCV-VG groups (T2: P = 0.015 and P = 0.002, respectively; T3: P = 0.007 and P = 0.009, respectively). The prone-related decrease in dynamic compliance was prevented by PCV and PCV-VG ventilation modalities at T2 and T3 than by VCV (T2: P = 0.008 and P = 0.015, respectively; T3: P = 0.015 and P = 0.014, respectively). Additionally, there were no significant differences in other secondary outcomes among the three groups.

CONCLUSION

In infants and young children undergoing spinal cord detethering surgery in the prone position, PCV-VG may be a better ventilation mode due to its ability to mitigate the increase in Ppeak and decrease in Cdyn while maintaining consistent VT.

Comparison of pressure controlled, volume controlled, and volume guaranteed pressure controlled modes in prone position in patients operated for lumbar disc herniation: A randomized trial

BACKGROUND

To compare pressure-controlled ventilation (PCV), volume-controlled ventilation (VCV), and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes in patients undergoing spinal surgery in the prone position under general anesthesia.

METHODS

The study included 78 patients aged 20 to 80 years, American Society of Anesthesiologists 1-2, scheduled for lumbar spinal surgery. Patients included in the study were randomly divided into 3 groups Group-VCV; Group-PCV; Group-PCV-VG. Standard anesthesia protocol was applied. In addition to routine monitoring, train of four and BIS monitoring were performed. All ventilation modes were set with a target tidal volume of 6 to 8 mL/kg, FiO2: 0.40-0.45 and a respiratory rate of normocarbia. Positive end-expiratory pressure: 5 cm H2O, inspiration/expiration ratio = 1:2, and the maximum airway pressure:40 cm H2O. Hemodynamic, respiratory variables and arterial blood gases was measured, 15 minutes after induction of anesthesia in the supine position (T1), after prone position 15 minutes (T2), 30 minutes (T3), 45 minutes (T4), 60 minutes (T5), 75 minutes (T6), 90 minutes (T7).

RESULTS

There was no significant difference between the groups in patient characteristics. SAP, DAP, mean arterial pressure, and heart rate decreased after being placed in the prone position in all groups. Hemodynamic variables did not differ significantly between the groups. partial arterial oxygen pressure and arterial oxygen saturation levels in blood gas were found to be significantly higher in Group-PCV-VG compared to Group-PCV and Group-VCV in both the supine and prone positions. Ppeak and plateau airway pressure (Pplato) values increased and dynamic lung compliance (Cdyn) values decreased after placing the patients in the prone position in all groups. Lower Ppeak and Pplato values and higher Cdyn values were observed in both the supine and prone positions in the Group-PCV-VG group compared to the Group-PCV and Group-VCV groups.

CONCLUSION

PCV-VG provides lower Ppeak and Pplato values, as well as better Cdyn, oxygenation values compared to PCV and VCV. So that PCV-VG may be an effective alternative mode of mechanical ventilation for patients in the prone position during lumbar spine surgery.

Patient Positioning in Spine Surgery: What Spine Surgeons Should Know?

Spine surgery has advanced tremendously over the last decade. The number of spine surgeries performed each year has also been increasing constantly. Unfortunately, the reporting of position-related complications in spine surgery has also been steadily increasing. These complications not only result in significant morbidity for the patient but also raises the risk of litigation for the surgical and anesthetic teams. Fortunately, most position-related complications are avoidable with basic positioning knowledge. Hence, it is critical to be cautious and take all necessary precautions to avoid position-related complications. We discuss the various position-related complications associated with the prone position, which is the most commonly used position in spine surgery, in this narrative review. We also discuss the various methods for avoiding complications. Furthermore, we briefly discuss less commonly used positions in spine surgery, like the lateral and sitting positions.

Effect of spine frame on the changes in respiratory dynamics in prone patients under general anaesthesia- a prospective, observational study

Background and Aims

The prone position is one of the common surgical positions used in clinical practice. Manoeuvring patients from supine to a prone position can impact respiratory dynamics and result in haemodynamic variations.

Methods

This study included 64 patients and was conducted after obtaining approval from the ethics committee and registration of the trial. The primary objective was to evaluate the changes in peak inspiratory pressure (PIP), plateau pressure (Pplat) and mean airway pressure (MAP) in patients undergoing surgery under general anaesthesia in the prone position with (Group S) and without (Group P) spine frame. The secondary objective was to evaluate and compare the variations in heart rate and blood pressure.

Results

On turning the patient prone, there was statistically significant increase in median PIP (Group S 4 cmH2O vs. Group P 0.5 cmH2O, P < 0.001), Pplat (Group S 3.5 cmH2O vs. Group P 1 cmH2O, P = 0.004) and dynamic compliance (Group S -5.513 vs. Group P -2.78, P < 0.004).

Conclusions

Our study found that prone positioning with a spine frame led to a significantly greater increase in airway pressures and a decrease in dynamic compliance when compared to patients positioned prone without the spine frame.

Atlantoaxial Anterior Transarticular Screw Fixation: Indications and Surgical Technique

Posterior atlantoaxial screw fixation is a widely adopted therapeutic option for C1-C2 instability secondary to fractures or dislocation, degenerative diseases, or tumors at this level. Anterior transarticular screw fixation (ATSF) is an effective alternative to the posterior approaches, presenting several advantages despite being scarcely known and rarely chosen.In this chapter, we describe the ATSF step by step, illustrating its variations reported in literature, and we critically analyze the several advantages and contraindications of this technique. Moreover, we provide a list of tips and tricks on the surgical procedure, including critical operating room settings-the result of more than 10 years of experience in the field by a senior author.ATSF is a valid strategy for the treatment of different diseases occurring at the level of the atlantoaxial complex that needs consideration. Given the significant learning curve of this strategy, some hints may be essential to begin introducing this technique in the personal armamentarium of a spine surgeon so that they can perform ATSF safely and effectively.

International Alliance of Urolithiasis (IAU) Guideline on percutaneous nephrolithotomy

The International Alliance of Urolithiasis (IAU) would like to release the latest guideline on percutaneous nephrolithotomy (PCNL) and to provide a clinical framework for surgeons performing PCNLs. These recommendations were collected and appraised from a systematic review and assessment of the literature covering all aspects of PCNLs from the PubMed database between January 1, 1976, and July 31, 2021. Each generated recommendation was graded using a modified GRADE methodology. The quality of the evidence was graded using a classification system modified from the Oxford Center for Evidence-Based Medicine Levels of Evidence. Forty-seven recommendations were summarized and graded, which covered the following issues, indications and contraindications, stone complexity evaluation, preoperative imaging, antibiotic strategy, management of antithrombotic therapy, anesthesia, position, puncture, tracts, dilation, lithotripsy, intraoperative evaluation of residual stones, exit strategy, postoperative imaging and stone-free status evaluation, complications. The present guideline on PCNL was the first in the IAU series of urolithiasis management guidelines. The recommendations, tips and tricks across the PCNL procedures would provide adequate guidance for urologists performing PCNLs to ensure safety and efficiency in PCNLs.

Volume-controlled ventilation versus pressure-controlled ventilation during spine surgery in the prone position: A meta-analysis

Background

Many studies have investigated a comparison of the potency and safety of PCV versus VCV modes in spinal surgery in prone position. However, controversy about the maximal benefits of which ventilation modes remains. The main purpose of this meta-analysis was to investigate which one is the optimal ventilation for surgery patients undergoing spine surgery in prone position between the two ventilation modes as PCV and VCV.

Methods

We conducted a comprehensive search of PubMed, Embase, Web of Science, the Cochrane Library, and Google Scholar for potentially eligible articles. The continuous outcomes were analyzed using the mean difference and the associated 95% confidence interval. Meta-analysis was performed using Review Manager 5.4 software.

Results

Our meta-analysis included 8 RCTs involving a total of 454 patients between 2012 and 2020. The results demonstrated that IOB, Ppeak and CVP for VCV are significantly superior to PCV in spinal surgery in prone position. And PCV had higher Cdyn and PaO₂/FiO₂ than VCV. But there was no significant difference between PCV and VCV in terms of POB, Hb, HCT, HR and MAP.

Conclusions

The PCV mode displayed a more satisfying effect than VCV mode. Compared to VCV mode in same preset of tidal volume, the patients with PCV mode in prone position demonstrated less IOB, lower Ppeak and CVP, and higher PaO₂/FiO₂ in spinal surgery. However, there is no obvious difference between PCV and VCV in terms of hemodynamics variables (HR and MAP).

•

The PCV mode displayed a more satisfying effect than VCV mode.

•

Compared to VCV mode, the patients with PCV mode in prone position demonstrated less IOB, lower Ppeak and CVP, and higher PaO2/FiO2 in spinal surgery.

•

There is no obvious difference between PCV and VCV in terms of hemodynamics variables.

Comparison of volume-controlled ventilation mode and pressure-controlled ventilation with volume-guaranteed mode in the prone position during lumbar spine surgery

Background

During lumbar spine surgery, patients are placed in the prone position for surgical access. The prone position has various effects on cardiac and pulmonary function, including a decreased cardiac index (CI), decreased dynamic lung compliance (Cdyn), and increased peak inspiratory pressure (Ppeak). In this study, we compared the volume-controlled ventilation mode (VCV) and pressure-controlled ventilation with volume guaranteed mode (PCV-VG) based on hemodynamic and pulmonary variables in the prone position during lumbar spine surgery.

Methods

Thirty-six patients scheduled for lumbar spine surgery in the prone position were enrolled in this prospective, randomized clinical trial. The patients were randomly assigned to receive VCV or PCV-VG. Hemodynamic variables, respiratory variables, and arterial blood gases were measured in the supine position 15 min after the induction of anesthesia, 15 min after placement in the prone position, 30 min after placement in the prone position, and 15 min after placement in the supine position at the end of anesthesia.

Results

The hemodynamic variables and arterial blood gas results did not differ significantly between the two groups. Lower Ppeak values were observed in the PCV-VG group than in the VCV group (p = 0.045). The Cdyn values in the VCV group were lower than those in the PCV-VG group (p = 0.040).

Conclusion

PCV-VG led to lower Ppeak and improved Cdyn values compared with VCV, showing that it may be a favorable alternative mode of mechanical ventilation for patients in the prone position during lumbar spine surgery.

Trial registration

The study was retrospectively registered at ClinicalTrials.gov (NCT 03571854). The initial registration date was 6/18/2018.

Lipoabdominoplasty: repercussions for diaphragmatic mobility and lung function in healthy women

Objective:

To evaluate the impact of lipoabdominoplasty on diaphragmatic mobility (DM) and lung function in healthy women.

Methods:

This was a prospective cohort study using high-resolution ultrasound and forced spirometry to assess DM and lung function, respectively, prior to lipoabdominoplasty, as well as on postoperative day (POD) 10 and POD 30. DM was measured under two conditions: during tidal volume breathing and during a VC maneuver.

Results:

The sample consisted of 20 women, with a mean age of 39.85 ± 7.52 years and a mean body mass index of 26.21 ± 2.0 kg/m². Comparing the preoperative and postoperative periods, we found that DM and lung function values were significantly lower after lipoabdominoplasty, the mean DM on POD 10 being 17% and 15% lower during tidal volume breathing and during the VC maneuver, respectively, in comparison with the preoperative mean (p = 0.009 and p < 0.001, respectively). In addition, FEV₁, FVC, and PEF were significantly lower on POD 10 than in the preoperative period (p = 0.046, p = 0.002, and p < 0.001, respectively), returning to preoperative values by POD 30.

Conclusions:

Lipoabdominoplasty appears to have negative short-term repercussions for DM and lung function in healthy women. However, lung function and DM are both apparently restored to preoperative conditions by POD 30. (ClinicalTrials.gov identifier: NCT02762526 [http://www.clinicaltrials.gov/])

Ability of mini-fluid challenge to predict fluid responsiveness in obese patients undergoing surgery in the prone position

BACKGROUND

Pulse pressure variation (PPV) and stroke volume variation (SVV) can predict fluid responsiveness effectively. However, high Body Mass Index (BMI) can restrict their use due to changes in respiratory system compliance (CS), intra-abdominal pressure, and stroke volume (SV) in the prone position. Therefore, we aimed to investigate the effectiveness of mini-fluid challenge (MFC) in predicting fluid responsiveness in obese (BMI ≥30 kg/m2) patients in the prone position.

METHODS

A total of 33 patients undergoing neurosurgery were included. After standardized anesthesia induction, patients' PPV, SVV, stroke volume index (SVI) and CS values were recorded in the prone position (T1), after the infusion of 100 mL of crystalloid named as MFC (T2) and after fluid loading was completed with additional 400 mL of crystalloid. Patients whose SVI increased more than 15% after the fluid loading were defined as volume responders.

RESULTS

Fifteen (45%) patients were responders to 500 mL fluid loading. After the 100 mL fluid load, a higher percentage increase in SVI was observed among responders (P<0.001), with values of 6.6% (6.2-8.6%) and 3.5% (1.7-4.8%) in responders and non-responders, respectively. Areas under the receiver operating characteristic curves of MFC, PPV, and SVV were 0.967 (95% CI: 0.838-0.999), 0.683 (95% CI: 0.499-0.834), and 0.709 (95% CI: 0.526-0.853), respectively. The area under the curve of MFC was significantly higher than that of PPV (P=0.003) and SVV (P=0.005).

CONCLUSIONS

The increase in SVI after a rapid infusion of 100 mL crystalloid could predict fluid responsiveness in patients with BMI ≥30 kg/m2 in the prone position.

Ventilation With High or Low Tidal Volume With PEEP Does Not Influence Lung Function After Spinal Surgery in Prone Position: A Randomized Controlled Trial

BACKGROUND

Spinal surgery in the prone position is accompanied by increased intrathoracic pressure and decreased respiratory compliance. This study investigated whether intraoperative lung protective mechanical ventilation improved lung function evaluated with pulmonary function tests in patients at risk of postoperative pulmonary complications (PPCs) after major spinal surgery in the prone position.

METHODS

Seventy-eight patients at potential risk of PPCs were randomly assigned to the protective group (tidal volume; 6 mL/kg predicted body weight, 6 cm H2O positive end-expiratory pressure with recruitment maneuvers) or the conventional group (10 mL/kg predicted body weight, no positive end-expiratory pressure). The primary efficacy variables were assessed by pulmonary function tests, performed before surgery, and 3 and 5 days afterward.

RESULTS

Postoperative forced vital capacity (2.17±0.1 L vs. 1.91±0.1 L, P=0.213) and forced expiratory volume in 1 second (1.73±0.08 L vs. 1.59±0.08 L, P=0.603) at postoperative day (POD) 3 in the protective and conventional groups, respectively, were similar. Trends of a postoperative decrease in forced vital capacity (P=0.586) and forced expiratory volume in 1 second (P=0.855) were similar between the groups. Perioperative blood-gas analysis variables were comparable between the groups. Patients in the protective and conventional groups showed similar rates of clinically significant PPCs (8% vs. 10%, P>0.999).

CONCLUSIONS

In patients at potential risk of developing PPCs undergoing major spinal surgery, we did not find evidence indicating any difference between the lung protective and conventional ventilation in postoperative pulmonary function and oxygenation.

Increasing positive end-expiratory pressure (re-)improves intraoperative respiratory mechanics and lung ventilation after prone positioning

BACKGROUND

Turning a patient prone, changes the respiratory mechanics and potentially the level of positive end-expiratory pressure (PEEP) that is necessary to prevent alveolar collapse. In this prospective clinical study we examined the impact of PEEP on the intratidal respiratory mechanics and regional lung aeration in the prone position. We hypothesized that a higher PEEP is required to maintain compliance and regional ventilation in the prone position.

METHODS

After ethical approval, 45 patients with healthy lungs undergoing lumbar spine surgery were examined in the supine position at PEEP 6 cm H2O and in the prone position at PEEP (6, 9 and 12 cm H2O). Dynamic compliance (CRS) and intratidal compliance-volume curves were determined and regional ventilation was measured using electrical impedance tomography. The compliance-volume curves were classified to indicate intratidal derecruitment, overdistension, or neither.

RESULTS

CRS did not differ between postures and PEEP levels (P>0.28). At a PEEP of 6 cm H2O a compliance-volume profile indicating neither derecruitment nor overdistension was observed in 38 supine, but only in 20 prone positioned patients (P<0.001). The latter increased to 33 and 37 (both P<0.001) when increasing PEEP to 9 and 12 cm H2O, respectively. Increasing PEEP from 6 to 9 cm H2O in the prone position increased peripheral ventilation significantly.

CONCLUSIONS

Respiratory system mechanics change substantially between supine and prone posture, which is not demonstrated in routine measurements. The intratidal compliance analysis suggests that in most patients a PEEP above commonly used settings is necessary to avoid alveolar collapse in the prone position.

CLINICAL TRIAL REGISTRATION

DRKS 00005692.

Effect of Body Mass on Oxygenation and Intra-Abdominal Pressure When Using a Jackson Surgical Table in the Prone Position During Lumbar Surgery

STUDY DESIGN

Prospective observational study.

OBJECTIVE

To test the hypothesis that different types of surgical frame and the patient's body mass index (BMI) can affect pulmonary compliance, intra-abdominal pressure (IAP), and oxygenation.

SUMMARY OF BACKGROUND DATA

The oxygenation index (PaO2/FiO2) and IAP are known to be associated with BMI when patients are in the supine position. However, there are few reports on the correlation between BMI, the oxygenation index, and IAP in the prone position, especially when a Jackson surgical table is used.

METHODS

Thirty-seven adult patients were divided into two groups according to BMI: normal-weight patients (n = 19, BMI: 18.5-24.9 kg m) and overweight patients (n = 18, BMI ≥ 25 kg m). After the induction of general anesthesia, patients were turned to the prone position onto either a Jackson surgical table (Mizuho OSI) or a general surgical table (MAQUET; foam pad, China). The patient's IAP, peak airway pressure, pulmonary dynamic compliance (Cdyn), and oxygenation index were recorded.

RESULTS

In overweight patients, there was a greater increase in peak airway pressure and a greater decrease in Cdyn observed when a general surgical table was used compared with the Jackson surgical table. When the Jackson surgical table was used, there was a greater increase in the oxygenation index and a greater decrease in IAP. There was a significant negative correlation between the oxygenation index and BMI and a significant positive correlation between IAP and BMI in the prone position.

CONCLUSION

Turning patients from the supine to the prone position during anesthesia results in an increase in the oxygenation index and a decrease in IAP. Both of these factors are dependent upon the type of surgical frame used and the patient's BMI. The reduction in IAP was particularly significant when a Jackson surgical table was used for overweight patients.

LEVEL OF EVIDENCE

4.

The Effect of Position on PaCO2 and PETCO2 in Patients Undergoing Cervical Spine Surgery in Supine and Prone Position

BACKGROUND

As per American Society of Anesthesiologists guidelines, continuous monitoring of end tidal carbon dioxide (PETCO2) is recommended as standard II basics of anesthetic monitoring especially to ensure adequate ventilation during all anesthetics. Continuous monitoring of PETCO2 can also be used as a guide to maintain the partial pressure of carbon dioxide in arterial blood (PaCO2) to desired level during the surgery.

AIMS AND OBJECTIVES

To study the effect of position on PaCO2 and PETCO2 during cervical spine surgery in prone position.

MATERIALS AND METHODS

Following institutional ethical committee approval and written informed consent, a prospective study was conducted in 40 patients of 18 to 60 years and of American Society of Anesthesiologists I and II scheduled for cervical spine surgery in prone position. In operating room, the patient is connected to standard monitoring and intravenous access was secured. A 20 G arterial cannula was placed. General anesthesia administered and oral endotracheal intubation done. Baseline values of systolic blood pressure, diastolic blood pressure, mean arterial pressure, heart rate, temperature, SpO2, Ppeak, Pmean, and Pplateau were measured in supine position. For each patient the capnometer was calibrated before use. The P(a-ET)CO2 was calculated in supine position (S1). The PaCO2 and ETCO2 were measured after prone positioning P1, at each subsequent hour (P2, P3, P4), and on completion of the procedure in supine position (S2). The mean values were used for further analysis.

RESULTS

The PETCO2 and PaCO2 decreased significantly in cervical spine surgery patients with change of position from supine to prone with no significant change in arterial to end tidal CO2 gradient (P(a-ET)CO2).

CONCLUSIONS

PETCO2 can be used as a reliable guide to estimate PaCO2 during cervical spine procedures in prone position.

The Effect of Pressure-Controlled Ventilation and Volume-Controlled Ventilation in Prone Position on Pulmonary Mechanics and Inflammatory Markers

The aim of this present study is to compare the effect of pressure-controlled ventilation and volume-controlled ventilation on pulmonary mechanics and inflammatory markers in prone position. The study included 41 patients undergoing to vertebrae surgery. The patients were randomized into two groups: Group 1 received volume-controlled ventilation, while group 2 received pressure-controlled ventilation. The demographic data, pulmonary mechanics, the inflammatory marker levels just after the induction of anesthetics, at the 6th and 12th hours, and gas analysis from arterial blood samples taken at the beginning and the 30th minute were recorded. The inflammatory marker levels increased in both groups, without any significant difference among groups. Peak inspiratory pressure level was higher in the volume-controlled ventilation group. This study revealed that there is no difference regarding inflammatory marker levels between volume- and pressure-controlled ventilation.

Effects of pressure-controlled and volume-controlled ventilation on respiratory mechanics and systemic stress response during prone position

BACKGROUND

Prone position during general anesthesia for special surgical operations may be related with increased airway pressure, decreased pulmonary and thoracic compliance that may be explained by restriction of chest expansion and compression of abdomen. The optimum ventilation mode for anesthetized patients on prone position was not described and studies comparing volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) during prone position are limited. We hypothesized that PCV instead of VCV during prone position could achieve lower airway pressures and reduce the systemic stress response. In this study, we aimed to compare the effects of PCV and VCV modes during prone position on respiratory mechanics, oxygenation, and hemodynamics, as well as blood cortisol and insulin levels, which has not been investigated before.

METHODS

Fifty-four ASA I-II patients, 18-70 years of age, who underwent percutaneous nephrolithotomy on prone position, were randomly selected to receive either the PCV (Group PC, n = 27) or VCV (Group VC, n = 27) under general anesthesia with sevoflurane and fentanyl. Blood sampling was made for baseline arterial blood gases (ABG), cortisol, insulin, and glucose levels. After anesthesia induction and endotracheal intubation, patients in Group PC were given pressure support to form 8 mL/kg tidal volume and patients in Group VC was maintained at 8 mL/kg tidal volume calculated using predicted body weight. All patients were maintained with 5 cmH₂O PEEP. Respiratory parameters were recorded during supine and prone position. Assessment of ABG and sampling for cortisol, insulin and glucose levels were repeated during surgery and 60 min after extubation.

RESULTS

P-peak and P-plateau levels during supine and prone positions were significantly higher and P-mean and compliance levels during prone position were significantly lower in Group VC when compared with Group PC. Postoperative PaO₂ level was significantly higher in Group PC compared with Group VC. Cortisol levels were increased with surgery in both groups (p < 0.05) and decreased to baseline levels in Group PC while remained high in Group VC in the early postoperative period. Cortisol levels were significantly higher in Group VC during surgery and in the early postoperative period compared with Group PC.

CONCLUSION

When compared with VCV mode, PCV mode is associated with lower P-peak and P-plateau levels during both supine and prone positions, better oxygenation postoperatively, lower blood cortisol levels during surgery in prone position and in the early postoperative period. We concluded that PCV mode might be more appropriate in prone position during anesthesia.

Atlantoaxial anterior transarticular screw fixation: a case series and reappraisal of the technique

BACKGROUND CONTEXT

Atlantoaxial instability is commonly treated with C1-C2 fixation performed via posterior approaches. Although anterior transarticular screw (ATS) fixation, performed with a classic retropharyngeal approach, was described more than 10 years ago, the published literature still lacks a comprehensive analysis of the procedure and a real case series.

PURPOSE

We report a series of patients treated with atlantoaxial ATS, describing the surgical procedure in detail and discussing advantages and disadvantages of the technique.

STUDY DESIGN

The study design includes case series and technical report.

METHODS

We prospectively enrolled 15 patients affected by atlantoaxial instability secondary to trauma, degenerative diseases, or inflammatory diseases. Anterior transarticular screw fixation was performed with anteroposterior open-mouth and lateral intraoperative radiographs. All patients were evaluated radiologically at follow-up to identify bone fusion.

RESULTS

Anterior transarticular screw was performed successfully in 14 patients without complications. The procedure was aborted in a case of vertebral invagination, and one case required revision surgery owing to C2 articular bone fracture. Solid C1-C2 fusion was achieved in all cases (at 10- to 21-week follow-up) except in an elderly patient affected by severe osteoporosis. No complications occurred.

CONCLUSIONS

Although the procedure is still not widely known, ATS allows the effective and safe treatment of C1-C2 instability even in patients with systemic comorbidities. It offers several advantages over posterior approaches.

Increase in airway pressure resulting from prone position patient placing may predict intraoperative surgical blood loss

STUDY DESIGN

Prospective study on intraoperative blood loss during lumbar spine surgery.

OBJECTIVE

To evaluate the relationship between airway pressure change due to the patient's prone position and intraoperative blood loss during lumbar spine surgery.

SUMMARY OF BACKGROUND DATA

A prone position may increase abdominal pressure. Changes in abdominal pressure may influence airway pressure and cause intraoperative blood loss as a result of epidural venous congestion.

METHODS

Patients undergoing lumbar spine surgery were placed in a prone position after the administration of general anesthesia. Peak airway pressure, plateau pressure, mean blood pressure, and heart rate were measured 5 minutes after anesthesia induction and 15 minutes after being placed in a prone position. Intraoperative blood loss was measured at the end of surgery.

RESULTS

Mean peak airway pressure was 13.7 ± 1.8 mm Hg while in a supine position and increased to 15.1 ± 2.5 mm Hg after placement in the prone position (P = 0.002). Plateau pressure was 12.6 ± 2.5 mm Hg while in a supine position and increased to 14.1 ± 1.9 mm Hg after placement in a prone position (P = 0.0002). Intraoperative blood loss was correlated with peak (R2 = 0.405) and plateau (R2 = 0.489) airway pressure changes.

CONCLUSION

Increase in airway pressure resulting from placement into a prone position may predict intraoperative surgical blood loss.

Effects of prone and jackknife positioning on lumbar disc herniation surgery

BACKGROUND

Intra-abdominal hypertension due to surgical position increases bleeding at the surgical site. In this study, we evaluated the impact of prone and jackknife position on intra-abdominal pressure (IAP), lung mechanics, blood loss at the surgical site, and duration of the surgical procedure on lumbar disc operations.

METHODS

Forty patients operated for single-space lumber disc herniation were included in our study. All patients were ASA I-II and 18 to 70 years old. Patients who had undergone previous spinal surgery, were on anticoagulant or anti-aggregant therapy, had hypertension, cardiac, respiratory, liver, or renal disorders, and were obese (Body Mass Index >35 kg/m²) were excluded. Patients were randomly assigned to either the prone or the jackknife position for surgery. Differences in lung mechanics, IAP, and surgical-site blood loss were calculated in both patient groups. Changes in pulmonary and abdominal pressure levels were measured both in face-up and down positions.

RESULTS

Bleeding at the surgical site (prone: 180.0±100.0 mL, jackknife: 100.0±63.6 mL, P=0.018) and IAP (prone: 11.0±3.0 mm Hg, jackknife: 8.0±2.0 mm Hg, P=0.006) were significantly reduced when patients were in the jackknife position. Operating time was approximately 40 minutes shorter in the jackknife position group, although this difference was not significant.

CONCLUSIONS

The jackknife position causes less IAP elevation and less surgical site bleeding compared with the prone position. The jackknife position is the preferred choice for single-level lumbar disc surgery in healthy, nonobese patients.

Complications in spinal deformity surgery: issues unrelated directly to intraoperative technical skills

STUDY DESIGN

Literature review of complications unrelated directly to surgical skills involved in spinal deformity surgery.

OBJECTIVE

Highlight complications associated with perioperative issues.

SUMMARY OF BACKGROUND DATA

Complications can arise from mundane events that arise during the operative experience, but are not directly related to surgical skills.

METHODS

Literature reviews that touches on the more common potential complication events that do not involve direct surgical expertise.

RESULTS

The topics of positioning, nutrition, blood loss, comorbidities, OR time, and pulmonary and GI concerns are discussed as basics that could derail a surgical outcome even with an otherwise uneventful surgical technique. The need for vigilance is stressed and the nuances of understanding these are discussed.

CONCLUSION

Mundane events can derail a perfectly executed surgical undertaking. Attention to detail, team work, close monitoring, and checklist type focus will help to improve, focus, and avoid these preventable complications that have nothing to do with direct surgical skills.

The effect on respiratory mechanics when using a Jackson surgical table in the prone position during spinal surgery

Background

Respiratory dynamics may be monitored and evaluated indirectly by measuring the peak inspiratory pressure and plateau pressure. In this study, the respiratory dynamics of patients undergoing spinal surgery using a Jackson surgical table were observed with a device after converting their position from supine to prone. The effects of the dynamic compliance and airway resistance were observed from the changes in peak inspiratory pressure and plateau.

Methods

Twenty five patients were selected as subjects scheduled to undergo lumbar spine surgery. After intubation, the patients were ventilated mechanically with a tidal volume of 10 ml/kg and a respiration rate of 10/min. Anesthesia was maintained with sevoflurane 1.5%, nitrous oxide 2 L/min and oxygen 2 L/min. The peak inspiratory pressure, plateau pressure, resistance, compliance, arterial oxygen tension, carbon dioxide tension, heart rate and arterial blood pressure were measured at 10 minutes after the induction of anesthesia. These parameters were measured again 10 minutes after placing the patient in the prone position.

Results

The prone position did not significantly affect the arterial oxygen tension, carbon dioxide tension, blood pressure and heart rate, but significantly increased the peak inspiratory pressure and resistance and decreased the dynamic compliance.

Conclusions

The peak inspiratory pressure was increased using a Jackson surgical table to minimize the abdominal pressure when converting from the supine to prone position. This might be due to a decrease in lung and chest compliance as well as an increase in airway resistance.

Hemodynamic changes during spinal surgery in the prone position

BACKGROUND

Hypertension and fluctuations in blood pressure (BP) during lumbar spinal surgery in the prone position under anesthesia are not unusual. The purpose of this study was to investigate the causes of the decrease in BP during lumbar spinal surgery in the prone position using a noninvasive monitor of cardiac output.

METHODS

Twenty ASA Class I or II patients, scheduled for elective lumbar spinal surgery in the prone position, had their hemodynamic status monitored by a BioZ.com system Impedance Cardiograph during anesthesia. Hemodynamic data (heart rate [HR], mean BP, cardiac index [CI], stroke volume [SV] and systemic vascular resistance [SVR]) were registered at baseline, post-induction of general anesthesia, 10 minutes after the patient was turned from the supine to the prone position and 1 hour after the start of surgery. Friedman's test and the paired t test were used to compare the collected data on hemodynamic parameters.

RESULTS

The mean BP, SV, CI and HR were found to have significant differences (p < 0.05) at the designated time points as analyzed by Friedman's test, while the SVR and central venous pressure showed no significant changes. CI and SV were found to be markedly decreased from 2.4 +/- 0.3 to 2.0 +/- 0.3 L/minute/m2 and from 45.8 +/- 9.7 to 36.7 +/- 9.2 mL, respectively, after patients assumed the prone position. Mean BP also decreased significantly. After 1 hour of surgery, the mean BP decreased further with a fall in HR but the SV remained unchanged.

CONCLUSION

Decreases in SV and CI are the main causes of a decrease in BP in the prone position during lumbar spinal surgery.

Risks and benefits of patient positioning during neurosurgical care

Positioning of the surgical patient is an important part of anesthesia care and attention to the physical and physiologic consequences of positioning can help prevent serious adverse events and complications. The general principles of patient positioning of the anesthetized and awake neurosurgical patient are discussed in this article.

Effect of prone position on regional shunt, aeration, and perfusion in experimental acute lung injury

RATIONALE

The prone position is used to improve gas exchange in patients with acute respiratory distress syndrome. However, the regional mechanism by which the prone position improves gas exchange in acutely injured lungs is still incompletely defined.

METHODS

We used positron emission tomography imaging of [(13)N]nitrogen to assess the regional distribution of pulmonary shunt, aeration, perfusion, and ventilation in seven surfactant-depleted sheep in supine and prone positions.

RESULTS

In the supine position, the dorsal lung regions had a high shunt fraction, high perfusion, and poor aeration. The prone position was associated with an increase in lung gas content and with a more uniform distribution of aeration, as the increase in aeration in dorsal lung regions was not offset by loss of aeration in ventral regions. Consequently, the shunt fraction decreased in dorsal regions in the prone position without a concomitant impairment of gas exchange in ventral regions, thus leading to a significant increase in the fraction of pulmonary perfusion participating in gas exchange. In addition, the vertical distribution of specific alveolar ventilation became more uniform in the prone position. A biphasic relation between regional shunt fraction and gas fraction showed low shunt for values of gas fraction higher than a threshold, and a steep linear increase in shunt for lower values of gas fraction.

CONCLUSION

In a surfactant-deficient model of lung injury, the prone position improved gas exchange by restoring aeration and decreasing shunt while preserving perfusion in dorsal lung regions, and by making the distribution of ventilation more uniform.

Induction of anesthesia and insertion of a laryngeal mask airway in the prone position for minor surgery

The use of the prone position for surgery presents potential obstacles to rapid tracking of patients during ambulatory anesthesia. We describe a prospective audit of 73 patients who placed themselves in the prone position; anesthesia was induced in this position and a laryngeal mask airway (LMA) was used to maintain the airway. Additional increments of propofol were given to one patient who had laryngospasm and to nine who required deepening of anesthesia before the LMA could be inserted. Of four cases with LMA malpositioning, the LMA was adjusted easily in three, but in one patient who was edentulous, it was necessary to hold the LMA for the duration of the procedure. Manual ventilation of the lungs via the LMA was required because of arterial oxygen desaturation and hypoventilation in four patients. Blood was noted outside the nostrils in two patients, presumably caused by soft tissue trauma after insertion of the LMA, and bradycardia occurred in five patients. In the postoperative period, hoarseness and sore throat were observed in one and six patients, respectively. With experience and appropriate patient selection, it is possible to induce and maintain anesthesia using a LMA in patients in the prone position for ambulatory surgery.

IMPLICATIONS

With experience and appropriate patient selection, it is possible to induce and maintain anesthesia using a laryngeal mask airway in patients in the prone position for ambulatory surgery.