Effect of intra-abdominal pressure on respiratory function in patients undergoing ventral hernia repair

[CT imaging in the treatment of ventral hernias]

Ventral hernias are one of the most common problems in abdominal surgery. At the same time, clinical diagnosis of abdominal hernia is a straightforward issue amenable to surgical treatment in the absence of severe comorbidities. However, long-term follow-up revealed disappointing results regarding complication rates and incidence of postoperative recurrences. In this context, preoperative planning with control of comorbidities and complete visualization of hernia and its anatomical relationships with abdominal organs is important. Computed tomography (CT) offers the best opportunity to determine dimensions and location of hernial defect(s), diastasis recti and/or associated muscle atrophy, as well as loss of domain. This information is valuable to select the best surgical technique (open or minimally invasive), location and fixation of mesh, possible need for various separation techniques, botulinum toxin, preoperative pneumoperitoneum or reduction interventions on abdominal organs. Nevertheless, this issue remains peripheral to active surgical discussions focusing on intervention techniques, postoperative management, etc., since there is currently no clear communication between radiologists and surgeons in this area of surgery. This review is devoted to the role of CT in the treatment of ventral hernias.

Intra-abdominal hypertension and compartment syndrome after complex hernia repair

PURPOSE

Abdominal compartment syndrome (ACS) is a well-known concept after trauma surgery or after major abdominal surgery in critically ill patients. However, ACS as a complication after complex hernia repair is considered rare and supporting literature is scarce. As complexity in abdominal wall repair increases, with the introduction of new tools and advanced techniques, ACS incidence might rise and should be carefully considered when dealing with complex abdominal wall hernias. In this narrative review, a summary of the current literature will highlight several key features in the diagnosis and management of ACS in complex abdominal wall repair and discuss several treatment options during the different steps of complex AWR.

METHODS

We performed a literature search across PubMed using the search terms: "Abdominal Compartment syndrome," "Intra-abdominal pressure," "Complex abdominal hernia," and "Ventral hernia." Articles corresponding to these search terms were individually reviewed by primary author and selected on relevance.

CONCLUSION

Intra-abdominal hypertension (IAH) and ACS require imperative attention and should be carefully considered when dealing with complex abdominal wall hernias, even without significant loss of domain. Development of a true abdominal compartment syndrome is relatively rare, but is a devastating complication and should be prevented at all cost. Current evidence on surgical treatment of ACS after hernia repair is scarce, but conservative management might be an option in the early phase and low grades of IAH. However, life-saving treatment by relaparotomy and open abdomen management should be initiated when ACS starts setting in.

Pre-Clinical Validation of A Novel Continuous Intra-Abdominal Pressure Measurement Equipment (SERENNO)

Introduction: Increased intra-abdominal pressure (IAP) has an important impact on morbidity and mortality in critically ill patients. The SERENNO Sentinel system (Serenno Medical, Yokne'am Illit, Israel) is a novel device that allows automatic and continuous IAP measurements. Aims: Pre-clinical validation in a bench model study comparing the new device with the gold standard method and two other continuous IAP measurement devices. Methods: IAP measurement with the novel SERENNO device (IAPSER) was compared with the gold standard IAPH2O (water column height) and two other automatic and continuous IAP measurement devices: IAPCiM measured via the CiMON device (Pulsion Medical Systems, Munich, Germany) and IAPSPIE measured using the Spiegelberg device (Spiegelberg, Hamburg, Germany), which previously received the CE mark for clinical applications. The IAP measurement was performed six times (n = 6) at each pressure value (between 0 and 35 mmHg) with different methods and the height of the water column in a bench-top phantom was used as the reference IAP for further interpretations. In addition to the quadruple comparisons, intra- and inter-observer variability of IAP measurements were also calculated. Correlation studies and Bland and Altman's analyses were performed in addition to the concordance study. Results: The CiMON and Spiegelberg devices showed a greater dynamic range and standard deviation when recording IAPCiM and IAPSPIE compared with IAPSER. In general, the maximum and minimum values of IAP recorded with each device (at each level of IAPH2O) were significantly different from each other. However, the average values were in very good agreement. The highest correlation was observed between IAPSER and IAPH2O, and IAPSER and IAPSPIE (R = 0.99, p = 0.001 for both comparisons and intra- and inter-observer measurements). Although the CiMON and SERENNO systems were in very good agreement with each other, a slightly smaller correlation coefficient was found between them (R = 0.95, p = 0.001, and R = 0.96, p = 0.001 for intra- and inter-observer measurements, respectively). When compared to the gold standard (IAPH2O), Bland and Altman's analysis showed a mean difference of +0.44, -0.25, and -0.04 mmHg for the intra-observer measurements and +0.18, -0.75, and -0.58 mmHg for the inter-observer measurements for IAPSER, IAPCiM, and IAPSPIE, respectively. IAPSER showed a small positive bias (overestimation), while IAPCiM and IAPSPIE showed a negative bias (underestimation) when compared to IAPH2O. Further statistical analysis showed a concordance coefficient of 100% with an excellent ability of the SERENNO system in tracking IAPH2O changes. Conclusions: Pre-clinical validation of a new IAP monitoring device (SERENNO) showed very promising results when compared with the gold standard and other continuous techniques; however, clinical trials should be followed as the next stage of the validation process. Based on the actual research guidelines, the SERENNO system can be used interchangeably with the gold standard.

Tanaka score predicts surgical intensive care admission following abdominal wall reconstruction

PURPOSE

With the advancement of abdominal wall reconstruction, more complex hernia patients are undergoing repairs that may require a postoperative surgical intensive care unit (SICU) admission. The volume ratio (VR) of the hernia sac to the abdominal cavity is an easily applied method to quantify disease severity and the ensuing physiologic insult. This study aimed to predict postoperative SICU admission using VR and other preoperative variables.

METHODS

A single-center retrospective review was conducted for patients undergoing large abdominal hernias (width ≥ 18 cm) repaired from September 2014 to October 2019. Patient demographics, comorbidities, abdominal surgical history, and VR were analyzed through univariate and multivariable methods to identify predictors of SICU admission within the first two postoperative days. A predictive model was generated and validated.

RESULTS

Of 434 patients meeting inclusion criteria, 127(29%) required a SICU admission within the first two postoperative days. VR was significantly higher in SICU patients (Median 30.6% [IQR 14.4-59.0] vs. 10.6% [IQR 4.35-23.6], P < 0.001). Male sex, history of chronic obstructive pulmonary disease, prior component separation, recurrent incisional hernia, hernia grade 3, and VR showed higher odds of SICU admission. When validated on a testing dataset, these variables showed strong SICU admission predictions, with an area under the curve, sensitivity, and specificity of 0.82, 81.7% and 68.5%, respectively.

CONCLUSIONS

The volume ratio in combination with preoperatively available variables can reliably predict postoperative SICU admission following abdominal wall reconstruction. Anticipating such events preoperatively allows for bed space allocation as well as optimizing postoperative care.

Laparoscopic ventral hernia repair in patients with obesity: should we be scared of body mass index?

BACKGROUND

Obesity is a risk factor for ventral hernia development and affects up to 60% of patients undergoing ventral hernia repair. It is also associated with a higher rate of surgical site occurrences and an increased risk of recurrence after ventral hernia repair, but data is lacking on the differences between obesity classes.

METHODS

Between 2008 and 2018, 322 patients with obesity underwent laparoscopic ventral hernia repair in our department: class I n = 231 (72%), II n = 55 (17%), III n = 36 (11%). We compared short and long-term outcomes between the three classes.

RESULTS

Patients with class III obesity had a longer median length of hospital stay compared to I and II (5 days versus 4 days in the other groups, p = 0.0006), but without differences in postoperative complications or surgical site occurrences. After a median follow up of 49 months, there were no significant differences in the incidence of seroma, recurrence, chronic pain, pseudorecurrence and port-site hernia. At multivariate analysis, risk factors for recurrence were presence of a lateral defect and previous hernia repair; risk factors for seroma were immunosuppression, defect > 15 cm and more than one previous hernia repair; the only risk factor for postoperative complications was chronic obstructive pulmonary disease.

CONCLUSION

Class III obesity is associated with longer length of hospital stay after laparoscopic ventral hernia repair, but without differences in postoperative complications and long-term outcomes compared with class I and class II obesity.

Protective ventilation from ICU to operating room: state of art and new horizons

The prevention of ventilator-associated lung injury (VALI) and postoperative pulmonary complications (PPC) is of paramount importance for improving outcomes both in the operating room and in the intensive care unit (ICU). Protective respiratory support includes a wide spectrum of interventions to decrease pulmonary stress-strain injuries. The motto 'low tidal volume for all' should become routine, both during major surgery and in the ICU, while application of a high positive end-expiratory pressure (PEEP) strategy and of alveolar recruitment maneuvers requires a personalized approach and requires further investigation. Patient self-inflicted lung injury is an important type of VALI, which should be diagnosed and mitigated at the early stage, during restoration of spontaneous breathing. This narrative review highlights the strategies used for protective positive pressure ventilation. The emerging concepts of damaging energy and power, as well as pathways to personalization of the respiratory settings, are discussed in detail. In the future, individualized approaches to protective ventilation may involve multiple respiratory settings extending beyond low tidal volume and PEEP, implemented in parallel with quantifying the risk of VALI and PPC.

The impact of weight change on intra-abdominal and hernia volumes

BACKGROUND

Weight loss is often encouraged or required before open ventral hernia repair. This study evaluates the impact of weight change on total, intra-abdominal, subcutaneous, and hernia volume.

METHODS

Patients who underwent open ventral hernia repair from 2007 to 2018 with two preoperative computed tomography scans were identified. Scans were reviewed using 3D volumetric software. Demographics, operative characteristics, and outcomes were evaluated. The impact of weight change on intra-abdominal, subcutaneous, and hernia volume was assessed using Spearman's correlation coefficients and linear regression models.

RESULTS

A total of 250 patients met the criteria with a mean defect area of 155.6 ± 155.4 cm², subcutaneous volume of 6,800.0 ± 3,868.8 cm³, hernia volume of 915.7 ± 1,234.5 cm³, intra-abdominal volume equaling 4,250.2 ± 2,118.1 cm³, and time between computed tomography scans 13.9 ± 11.0 months. Weight change was associated with change in hernia, intra-abdominal, total, and subcutaneous volume (Spearman's correlation coefficients 0.17, 0.48, 0.51, 0.45, respectively, P ≤ 0.03 all values) and not associated in hernia length, width, or area (P ≥ 0.18 all values). A Δ5 kg was significantly associated with Δintra-abdominal volume (164.1 ± 30.0 cm³/Δ5 kg,P < .0001), Δtotal volume (209.9 ± 33.0 cm³/Δ5 kg, P < .0001), and Δsubcutaneous volume (234.4 ± 50.8 cm³/Δ5 kg, P < .0001). Per Δ5 kg, male patients had more than double the Δintra-abdominal, Δtotal, and Δsubcutaneous volume than did female patients. A weight change of 5 kg to10 kg was associated with approximately double the change in computed tomography parameters/Δ5 kg than any weight change after 10 kg. Regardless of weight change, all measured hernia parameters increased over time, with mean hernia volume of +40.6 ± 94.9 cm³/mo and area of +7.8 ± 13.3 cm²/mo (Spearman's correlation coefficient -0.03 to 0.07, P value 0.37-0.96).

CONCLUSION

Weight change is linearly correlated with intra-abdominal and subcutaneous fat gain or loss. Males show greater abdominal-related response to weight gain or loss. Hernia dimensions increase over time regardless of weight change.

Too big to breathe: predictors of respiratory failure and insufficiency after open ventral hernia repair

INTRODUCTION

Increased intra-abdominal pressure in open ventral hernia repair (OVHR) is hypothesized to contribute to postoperative respiratory insufficiency (RI) or failure (RF). This study examines the impact of abdominal volumes on postoperative RI in OVHR.

METHODS

OVHR patients with preoperative CT scans were identified. 3D volumetric software measured hernia volume (HV), subcutaneous volume (SQV), and intra-abdominal volume (IAV). The ratio of hernia to intra-abdominal volume (HV:IAV) was calculated. A principal component analysis was performed to create new component variables for collinear volume and hernia variables.

RESULTS

There were 1178 OVHR patients with preoperative CT scans. Demographics included a mean BMI of 34.2 ± 7.7 kg/m², age of 58.5 ± 12.4 years, and 57.8% were female. RI occurred in 8.3% of patients, including 4.0% requiring > 24 h respiratory support with ezPAP, CPAP, or biPAP (RI), and 4.3% requiring intubation (RF). Patients who developed RI had a higher BMI (33.8 ± 7.5 vs. 38.2 ± 9.1 kg/m², p < 0.0001), older age (58.1 ± 12.5 vs. 62.8 ± 10.4 years, p = 0.0001), larger defects (140.9 ± 128.4 vs. 254.0 ± 173.9 cm², p < 0.0001), HV (865.8 ± 1200.0 vs. 2005.6 ± 1791.7 cm³, p < 0.0001), and HV:IAV (0.26 ± 0.45 vs. 0.53 ± 0.58, p < 0.0001). Three PC variables accounted for 85% of variance: hernia volume PC consists primarily of HV (61.8%), ratio HV:IAV (57.7%), and defect size (50.1%) and accounts for 38.3% variance. Extra-abdominal volume PC consists primarily of SQV (63.7%) and BMI (60.8%) and accounts for 32.5% variance. Intra-abdominal volume PC is primarily IAV (75.8%) and accounts for 14.9% variance. In multivariate analysis, predictors of RI included asthma and COPD (OR 4.04, CI 1.82-8.96), hernia PC (OR 1.47, CI 1.48-1.98), EAV PC (OR 1.24, CI 1.04-1.48), increased age (OR 1.04, CI 1.01-1.06), and diabetes (OR 1.8, CI 1.11-2.91). Component separation, fascial closure, contamination, and panniculectomy were not associated with RI.

CONCLUSION

The impact of defect size, BMI, HV, SQV, IAV, and HV:IAV on respiratory insufficiency after OVHR is collinear. Patients with large defects and a large ratio of HV:IAV (greater than 0.5) are also at significantly increased risk of RI after OVHR. While BMI impacts these parameters, it is not directly predictive of postoperative RI.

Three-dimensional hernia analysis: the impact of size on surgical outcomes

INTRODUCTION

BMI and hernia defect size are strongly associated with outcomes after open ventral hernia repair (OVHR). The impact of abdominal subcutaneous fat (SQV), intra-abdominal volume (IAV), hernia volume (HV), and ratio of HV to intra-abdominal volume (HV:IAV, representing visceral eventration) is less clearly elucidated. This study examines the interaction of multiple markers of adiposity and hernia size in OVHR.

METHODS

OVHR with preoperative CT scans were identified. 3D volumetric software measured HV, SQV, IAV, and HV:IAV was calculated. A principal component analysis was performed to create new component variables for collinear variables. Hernia PC was composed primarily of hernia dimensions, EAV (extra-abdominal volume PC) included SQV and BMI, and IAV PC included IAV.

RESULTS

A total of 1178 OVHR patients had a preoperative CT scan. Their demographics included a mean age of 58.5 ± 12.4 years, BMI of 34.2 ± 7.7 kg/m², and 57.8% were female. The mean defect area was 150.8 ± 136.7 cm², and 66.0% were recurrent, Patients had mean SQV of 6719.4 ± 3563.9 cm³, HV of 966.9 ± 1303.5 cm³, IAV of 4250.2 ± 2118.1 cm³, and a HV:IAV of 0.29 ± 0.46. In multivariate analysis, Hernia PC was associated with panniculectomy (OR 1.52, CI 1.37-1.69) and component separation (OR 1.34, CI 1.21-1.49) and was negatively associated with fascial closure (OR 0.78, CI 0.69-0.88). Hernia PC was also associated with reoperation, readmission, and development of wound complications (OR 1.18, CI 1.08-1.30; OR 1.15, CI 1.04-1.27; OR 1.28, CI 1.16-1.41, respectively). EAV PC was associated with performance of a panniculectomy (OR 1.33, CI 1.20-1.48), readmission (OR 1.18, CI 1.06-1.32), and wound complications (OR 1.41, CI 1.27-1.57). IAV PC was not associated with adverse outcomes.

CONCLUSION

Values of hernia area, volume, IAV, HV:IAV, BMI, and SQV are collinear markers of patient obesity and hernia proportions. They are distinct enough to be represented by three principal component variables, indicating more nuanced discrete influences on variability of surgical outcomes other than BMI.

Incidence, Risk Factors, and Outcomes of Intra-Abdominal Hypertension in Critically Ill Patients-A Prospective Multicenter Study (IROI Study)

OBJECTIVES

To identify the prevalence, risk factors, and outcomes of intra-abdominal hypertension in a mixed multicenter ICU population.

DESIGN

Prospective observational study.

SETTING

Fifteen ICUs worldwide.

PATIENTS

Consecutive adult ICU patients with a bladder catheter.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four hundred ninety-one patients were included. Intra-abdominal pressure was measured a minimum of every 8 hours. Subjects with a mean intra-abdominal pressure equal to or greater than 12 mm Hg were defined as having intra-abdominal hypertension. Intra-abdominal hypertension was present in 34.0% of the patients on the day of ICU admission (159/467) and in 48.9% of the patients (240/491) during the observation period. The severity of intra-abdominal hypertension was as follows: grade I, 47.5%; grade II, 36.6%; grade III, 11.7%; and grade IV, 4.2%. The severity of intra-abdominal hypertension during the first 2 weeks of the ICU stay was identified as an independent predictor of 28- and 90-day mortality, whereas the presence of intra-abdominal hypertension on the day of ICU admission did not predict mortality. Body mass index, Acute Physiology and Chronic Health Evaluation II score greater than or equal to 18, presence of abdominal distension, absence of bowel sounds, and positive end-expiratory pressure greater than or equal to 7 cm H2O were independently associated with the development of intra-abdominal hypertension at any time during the observation period. In subjects without intra-abdominal hypertension on day 1, body mass index combined with daily positive fluid balance and positive end-expiratory pressure greater than or equal to 7 cm H2O (as documented on the day before intra-abdominal hypertension occurred) were associated with the development of intra-abdominal hypertension during the first week in the ICU.

CONCLUSIONS

In our mixed ICU patient cohort, intra-abdominal hypertension occurred in almost half of all subjects and was twice as prevalent in mechanically ventilated patients as in spontaneously breathing patients. Presence and severity of intra-abdominal hypertension during the observation period significantly and independently increased 28- and 90-day mortality. Five admission day variables were independently associated with the presence or development of intra-abdominal hypertension. Positive fluid balance was associated with the development of intra-abdominal hypertension after day 1.

Preoperative Respiratory Physiotherapy in Abdominoplasty Patients

BACKGROUND

After abdominoplasty, patients experience decreased ventilatory function and increased intra-abdominal pressure (IAP). Breathing exercises are used during the pre- and postoperative periods of several abdominal surgeries to prevent or minimize postoperative complications.

OBJECTIVES

The aim of this study was to assess the effect of preoperative respiratory physiotherapy on the outcome of abdominoplasty patients.

METHODS

Thirty-three patients were divided into 2 groups. The control group (n = 18) received no preoperative intervention. The intervention group (n = 15) performed breathing exercises during the preoperative period, including incentive spirometry, diaphragmatic breathing, shortened expiration, and sustained maximal inspiration. Respiratory physiotherapy started one week before surgery. Breathing exercises were performed daily. They were performed 3 times weekly in the presence of a physiotherapist and patients were instructed to carry on the exercises at home on days without physiotherapy sessions for three sets of 20 repetitions each. Patients were assessed by spirometry and IAP measurements.

RESULTS

No significant difference in spirometry was found between groups. However, patients in the intervention group had lower IAP at the start of surgery and at all time points (P = 0.010) compared with controls.

CONCLUSIONS

Preoperative respiratory physiotherapy had no impact on spirometry, but may have contributed to reduce IAP intraoperatively.

LEVEL OF EVIDENCE 2

Biomechanical abdominal wall model applied to hernia repair

BACKGROUND

Most surgical innovations require extensive preclinical testing before employment in the operative environment. There is currently no way to develop and test innovations for abdominal wall surgery that is cheap, repeatable and easy to use. In hernia repair, the required mesh overlap relative to defect size is not established. The aims of this study were to develop a biomechanical model of the abdominal wall based on in vivo pressure measurements, and to apply this to study mesh overlap in hernia repair.

METHODS

An observational study of intra-abdominal pressure (IAP) levels throughout abdominal surgery was conducted to identify the peak perioperative IAP in vivo. This was then applied in the development of a surrogate abdominal wall model. An in vitro study of mesh overlap for various defect sizes was then conducted using this clinically relevant surrogate abdomen model.

RESULTS

The mean peak perioperative IAP recorded in the clinical study was 1740 Pa, and occurred during awakening from anaesthesia. This was reproduced in the surrogate abdomen model, which was also able to replicate incisional hernia formation. Using this model, the mesh overlap necessary to prevent hernia formation up to 20 kPa was found, independent of anatomical variations, to be 2 × (defect diameter) + 25 mm.

CONCLUSION

This study demonstrated that a surgically relevant surrogate abdominal wall model is a useful translational tool in the study of hernia repair. Surgical relevance This study examined the mesh overlap requirements for hernia repair, evaluated in a biomechanical model of the abdomen. Currently, mesh size is selected based on empirical evidence and may underpredict the requirement for large meshes. The study proposes a relationship between the defect size and mesh size to select the appropriate mesh size. Following further trials and investigations, this could be used in clinical practice to reduce the incidence of hernia recurrence.