Basic Concepts and Factors Associated With Ventral Hernia Recurrence

A hernia is described as a protrusion of an organ or tissue from its normal cavity. This protrusion may extend outside the abdominal wall or between body cavities. Hernias vary in presentation including congenital, umbilical and epigastric hernias, inguinal, traumatic flank hernias, and incisional hernias to name a few. In addition, hernia etiology may differ based upon type. A congenital hernia, present at birth, is the result of defective development of the abdominal wall; alternatively, hernias may be acquired later in life as the result of injury to the abdominal wall via trauma or surgery. An acquired hernia may be attributed to overexertion, weight lifting, jumping from a high distance, or violent coughing episodes, although underlying connective tissue disorders may also be a contributing factor. In recent years, the role of connective tissue disease such as Marfan syndrome, Ehlers-Danlos syndrome, and osteogenesis imperfecta have shown a predisposition for hernia development. Similarly, syndromes such as polycystic kidney disease, known for an abnormal extracellular matrix production, have been demonstrated to be associated with up to a 43% incidence of hernias. It is believed that abnormalities in collagen metabolism contribute to hernia formation and high recurrence rates in these populations. Multiple genomics projects are ongoing, looking at candidate genes responsible for the production of type I and III collagens as well as matrix metalloproteinases (MMPs).

The goal of ventral hernia repair generally includes closure of the midline without excess tension. Many risk factors influence the longevity of that repair including patient factors (increased intraabdominal pressure, diminished tissue integrity) and technical factors (infection, lateral mesh detachment, missed hernia). It is estimated that 75% of all recurrences are due to infection and inadequate repair material fixation and/or overlap. Each type of hernia has specific hernia recurrence rates. Midline laparotomies for nonhernia surgery carry a 25% risk of developing an incisional hernia. Five-year reoperation rates for incisional hernia repairs have been reported at 24% following the first reoperation, 35% after the second, 39% after the third, with the 7-year rate after three operations nearing 50%. These data underscore the importance of minimizing the risk for subsequent reoperations by employing the best evidence-based approach for the first hernia repair. Multiple comorbidities have been identified to increase the risk of infection following hernia repair. A higher infection occurrence then augments the risk of recurrence. Comorbidities that increase rates of postoperative infections include smoking, diabetes, chronic corticosteroid use, immunosuppression, coronary artery disease, chronic obstructive pulmonary disease, low preoperative serum albumin levels, prolonged operative times, and use of absorbable synthetic mesh.

Many classification systems have also been developed to categorize hernias to better understand who is at risk.

Global classifications for wound status include the Centers for Disease Control and Prevention (CDC) wound classification. This system categorized all surgeries into one of four groups: clean, clean-contaminated, contaminated, and dirty. Each CDC class was assigned a risk of postoperative wound infections by the CDC in 1985. Clean wounds are known uninfected wounds without entry into any visceral tracts that carry a low risk of 1% to 5%. Clean-contaminated wounds are those in which the respiratory, alimentary, genital, or urinary tracts are entered under controlled conditions, increasing infection risk to 3% to 11%. Contaminated wounds include open, fresh, accidental wounds, those with major breaks in sterile technique, gross spillage from the gastrointestinal tract, and presence of nonpurulent inflammation. The risk of infection in a contaminated wound is 10% to 17%. Finally, dirty or infected wounds include those with old traumatic wounds, retained devitalized tissue, and those with an existing clinical infection or perforated viscus. Their risk is expectedly elevated to greater than 27% for postoperative surgical site infection (SSI). The CDC updated the estimated SSI rates again in 1985 and 1991 following changes in antibiotic coverage and technique with 2.1% for clean, 3.3% for clean-contaminated, 10% to 17% for contaminated, and over 27% for dirty. CDC classification focuses only on the characteristics of the wound at the time of repair.

The Ventral Hernia Working Group (VHWG) classification system developed a grading scale to predict SSI based on characteristics of the individual and their hernia defect. Grade 1 represents patients considered low risk, no comorbidities, no history of prior wound infection, or current contamination. Grade 2 hernias include patients with comorbidities including smoking, obesity, diabetes, immunosuppression, chronic obstructive pulmonary disease, without current wound contamination or active infection. These patients are at increased risk of infection due to their associated comorbidities. Grade 3 hernias include those with a history of prior wound infection, presence of a stoma, or concurrent violation of the gastrointestinal tract. Grade 4 hernias are classified as infected with known mesh infections or septic dehiscence. The awareness of risk factors and hernia grade allow for personalization of hernia repair, mesh selection, and risk optimization. The VHWG grading scale was not validated, however, due to lack of available data.

Published in 2012, the VHWG was modified following the review of 299 open ventral hernia repairs with determination of SSI rates for each grade. Following this analysis, the modified system was developed representing three grades. VHWG-M grade 1 includes low risk hernias with low risk of complications and no prior wound infections with a reported surgical site occurrence (SSO) rate of 14%. VHWG-M grade 2 hernias represent patients with significant comorbidities. VHWG-M grade 2 patients experience postoperative SSO rates of 27%. VHWG-M grade 3 includes hernias with all degrees of bacterial contamination including clean-contaminated, contaminated, and dirty procedures with SSO rates of 46%.

The Ventral Hernia Risk Score (VHRS) was developed using a single-center data within a Veterans Affairs population to stratify SSI risk based upon wound classification, comorbid conditions, and technique. The VHRS assigns points ascribed to each of five clinical attributes: concomitant hernia repair (2 points), creation of skin flaps (2 points), American Society of Anesthesiologists (ASA) score 3 or greater (2 points), body mass index (BMI) 40 or more kg/m ² (3 points), and incision class 4 or dirty (7 points). There are five VHRS subgroups with progressive associated risk for wound infection based upon the range of points accumulated: group I (0 points), group II (2 to 3 points), group III (4 points), group IV (5 to 10 points), and group V (11 to 16 points). The risk of SSI development varied from group I at 7.8% compared with group V at 83.3%. The VHRS was externally validated and found to have greater predictive accuracy compared with VHWG and CDC classification systems in determining risk of SSI at 30 days. Morbid obesity (odds ratio [OR] 2.4), elevated ASA class (OR 3.4), skin flap creation (OR 3.3), CDC wound class 4 (OR 4.7), and concomitant hernia repair (OR 1.7) are all risk factors for SSI. Smoking and diabetes mellitus were both associated with SSI development on univariable analysis but were not independent variables in the VHRS model. Several components of the VHRS are modifiable patient factors, allowing for identification of patients who will benefit from preoperative interventions.

The European Hernia Society has developed a nomenclature system to facilitate the use of standardized terminology to describe hernias. It was developed following a 2008 consensus conference in Belgium focusing on location of each hernia and width that can be attributed to midline and lateral primary hernias as well as incisional hernias. The classification system allows for more specific discussion and comparison of hernias with a common nomenclature. Midline hernias are designated from the xiphoid process to the pubic bone and medial to the lateral margin of the rectus sheath on both sides. Lateral hernias occur from costal margin to inguinal region and from the lateral margin of the rectus sheaths to the lumbar region. Hernias are demarcated by size: W1, 1 to 4 cm; W2, 4 to 10 cm; and W3, greater than or equal to 10 cm as well as recurrent nature. Table 50.1 , adapted from the European Hernia Society definitions, depicts the types of hernias that can occur on the abdominal wall. A standardized classification for hernias should be used to allow for effective description of outcome measures as pertaining to hernia groups, recognizing that not all hernia repairs are associated with comparable results.

TABLE 50.1

European Hernia Society Classification of Incisional Hernia

Midline hernias	Subxiphoid	M1	From the xiphoid process to 3 cm caudally
	Epigastric	M2	From 3 cm below the xiphoid process to 3 cm above the umbilicus
	Umbilical	M3	3 cm above the umbilicus to 3 cm below the umbilicus
	Infraumbilical	M4	From 3 cm below umbilicus to 3 cm above pubis
	Suprapubic	M5	From the pubic bone to 3 cm caudally
Lateral hernias	Subcostal	L1	Between the coastal margin and the horizontal line 3 cm above the umbilicus
	Flank	L2	Lateral to the rectus sheath in the area 3 cm above and below the umbilicus
	Iliac	L3	Between a horizontal line 3 cm below the umbilicus and the inguinal region
	Lumbar	L4	Lateral and dorsal to the anterior axillary line

Optimizing Known Risk Factors

Multiple risk factors have been associated with increased ventral hernia recurrence following repair. It is important to optimize each one of these risk factors.

Diabetes Mellitus

Diabetes mellitus has long been described as a risk factor for major morbidity and mortality after surgery. Poorly regulated glucose metabolism due to insulin resistance or stress hyperglycemia after acute illness or trauma results in short-term glucose elevations associated with an increased SSI rate. A recent study by Goodenough et al. reported the correlation of elevated preoperative HbA1c to perioperative glycemic control. Patients with normal preoperative HbA1c were more likely to have normal peak perioperative glucose, and similarly, patients with an elevated HbA1c experience a higher incidence of perioperative hyperglycemia, defined as glucose greater than 160 mg/dL. HbA1c was shown to be a stronger predictor of adverse events compared with preoperative diabetes mellitus status or perioperative glucose. Other studies have identified a similar association between HbA1c and surgical outcomes. Although the optimal preoperative HbA1c has not been established, efforts should be made to optimize glycemic control and HbA1c prior to consideration of any elective hernia repair to enhance postoperative outcomes.

In 2001 Latham et al. reported a 7.9% SSI rate in patients with a HbA1c greater than 8, a twofold risk compared with patients with an HbA1c less than 8. Endara et al. found that HbA1c greater than 6.5% was associated with increased rates of dehiscence after surgical wound closure similar to the finding by Goodenough et al. in which 6.5% was found to be the threshold HbA1c level at which complication rates increase. Underwood et al. treated diabetic patients with HbA1c greater than 8% preoperatively, resulting in considerable blood glucose level improvements on the day of surgery. The American Diabetes Association recommends that outpatient management of diabetes should ideally include a combination of target HbA1c less than 7%, preprandial blood glucose level of 90 to 130 mg/dL, and a peak postprandial blood glucose level of less than 180 mg/dL. While no finite recommendation exists, most experts agree that attempts to obtain a HbA1c less than 8 should be made prior to elective hernia repair with a goal as close to 6.5% as feasible.

In Goodenough et al. publication, one-third of patients without a history of diabetes were found to have HbA1c greater than 6.5% on screening. These patients were more likely to have a BMI greater than 30, have additional comorbidities including coronary artery disease, and have chronic pulmonary obstructive disease, as well as categorized as non-Caucasian. Based on these findings, we recommend obtaining HbA1c levels on all patients with BMI greater than 30 kg/m ² presenting for elective ventral hernia repair.

Smoking and Alcohol Cessation

Smoking and alcohol use have been shown to negatively impact postoperative outcomes. Current smokers have an increased risk of pulmonary and wound complications following operation. The effects of nicotine on a cellular level include vasoconstriction and tissue level hypoxia correlating with tissue nicotine levels, increased platelet aggregation, and reduced fibroblast migration. Carbon monoxide levels also reduce oxygen delivery to the tissues, leaving smokers who consume greater than 20 cigarettes hypoxic most of the day. The additive effects of tissue hypoxia, reduced fibroblast proliferation, reduced collagen 1 to 3 ratios and reduced overall collagen deposition in smokers leads to increased wound infections and reduced tissue strength. Smoking one cigarette decreases cutaneous and subcutaneous blood flow by 38.1%. Smoking cessation of 4 weeks preoperatively has been shown to reduce wound infection rates from 12% in 1 pack per day smokers to 1%, values comparable with patients who have never smoked. In that investigation, there was no difference between transdermal nicotine patch and placebo patches used for smoking cessation techniques. Specifically, in hernia patients, active smokers experience more frequent hernia recurrences and postoperative infections than comparable nonsmoking patients. Smoking cessation efforts rank highly among the most challenging initiatives for patients and physicians. Smoking recidivism rates are not insignificant following attempts at smoking cessation. However, considering the increased morbidity and cost associated with hernia complications and recurrences, attempts at smoking cessation prior to elective ventral hernia repair should be attempted. Although extenuating circumstances may compel patients and surgeons to proceed with elective repair in patients using cigarettes, the risks should be carefully considered preoperatively, as each hernia recurrence carries a greater risk of recurrence than the prior repair. Patients with multiple recurrent hernias are generally not suitable for elective repair while smoking, but first-time repairs in smokers should be similarly discouraged to avoid the creation of recurrent-hernia patients.

Alcohol abuse is associated with an increased risk of bleeding, wound, and cardiopulmonary complications. Alcohol abuse is categorized as ingestion of five or more drinks (60 g of ethanol) a day. Abstinence from alcohol for 1 month preoperatively reduces postoperative morbidity with reduced responses to surgical stress, improved cardiac and immune dysfunction.

Weight Optimization

BMI is considered a significant predictor for surgical site occurrence. Morbidly obese patients are at a higher risk for the development of abdominal wall defects and progression of the size of the defects due to increased intraabdominal pressure and poor wound healing potential. The relationship between obesity and surgical complications including SSIs has been reported in colorectal surgery, and more recently, the association has been specifically related to ventral hernia repair. BMI is considered a significant predictor for SSI when analyzed as a continuous variable, thus demonstrating that SSI risk increases with increasing BMI. These authors recommend optimization of comorbidities such as morbid obesity prior to surgical intervention. While the ideal BMI for elective hernia repair is often debated, BMI should be evaluated in the context of individual patient and hernia characteristics when determining the best strategy for patient management. Other factors such as risk for incarceration, crescendo symptomatology, and rapidity of hernia progression may influence decision making. For example, patients with small defects with large volumes of incarcerated bowel may be at risk for significant intestinal loss in the event of strangulation. In such circumstances, elective repair may be appropriate in high BMI patients despite the increased perioperative risks.

Accordingly, patients amenable to a laparoscopic approach might be considered for an elective operation at higher BMI levels due to the reduced likelihood of postoperative infections in the morbidly obese compared with open hernia repairs. While conversion to an open procedure is always possible, conversion rates are low in many large laparoscopic ventral hernia repair series.

As the incidence of obesity in the adult population increases, surgeons are evaluating the outcomes of this patient subset to better understand the feasibility of hernia repair. One recent study reviewed the care of patients with BMI as high as 50 kg/m ² in association with other patient characteristics that were deemed to be favorable for laparoscopic repair (gynecoid body habitus, reducible hernias found in a central location, abdominal wall thickness less than 4 cm, and the defect's largest diameter not exceeding 8 cm). In a short 2-year follow-up, there were minimal recurrences ; however, critics of this study state that hernia recurrence at later time intervals is eminent. A retrospective review of a prospectively maintained database of four hernia surgeons focused on patients with BMI greater than or equal to 40 kg/m ² compared with patients with BMI less than 40 kg/m ² undergoing laparoscopic ventral hernia repair. The authors found operative duration, length of hospital stay, and recurrence rate for a mean follow-up time of 19 months were significantly greater in the morbidly obese group than for patients with BMI less than 40 kg/m ² . Other studies have found the laparoscopic approach to offer a safe alternative for obese patients but with apparent increased risk of recurrence of hernia for this subset of patients.

Weight loss surgery is an effective method of weight loss, and ventral hernia repair can be safely combined with weight loss procedures such as Roux-en-Y gastric bypass and sleeve gastrectomy or performed in stages. A large national database study showed that patients who underwent ventral hernia repair in conjunction with either laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy had increased incidence of SSI but not overall morbidity in the 30-day postoperative time period, again providing evidence of the seeming appropriateness of the combination of these procedures. However, long-term outcome studies specifically addressing hernia recurrence rates in these populations are lacking.

As a patient's BMI approaches 30 kg/m ² , the risk of infection and recurrence reduce; however, an optimal cutoff BMI for ventral hernia repair in the obese population is still debatable. In general, a BMI of less than 40 kg/m ² may be considered safe for repair supported by the work of Tsereteli et al.

Prior Wound Infections

Antecedent wound complications are not uncommon among patients presenting with incisional hernias as this is a significant risk factor for hernia formation. In a landmark study in the 1980s, a history of previous wound infection predicted a greater risk for subsequent wound infection following incisional hernia repair. Houck et al. noted that 41% of patients with prior wound infections developed an infection following subsequent repairs compared with an infection rate of 12% in patients without previous infections ( P < .05), thus emerging the concept that once an abdominal wall is infected, the risk for subsequent infections remains elevated. Subsequent infections increase the risk of hernia recurrence by 80% with a relative risk of 4.3 compared with noninfected repairs. Although the presence of prior infections represents a nonmodifiable risk factor for future complications, this increased risk associated with prior infections should heighten the awareness of other modifiable risk factors to facilitate optimal outcomes.

Preoperative Risk Reduction

Multiple enhanced recovery protocols have been developed to both optimize the risk factors previously discussed as well as optimize immediate nutritional and infectious factors to limit wound infections and complications. These enhanced recovery protocols strive to implement and standardize best practices to reduce perioperative risk, reduce hospital length of stay, and reduce the cost of care, thus enhancing health care value. Numerous measures are included in an enhanced recovery protocol, each of equal importance; thus, the implementation of the entirety of the program is essential in maximizing risk reduction.

Immune Modulators and Preoperative Nutrition

Experimental studies have shown nutritional supplements containing l -arginine, omega-3 polyunsaturated fatty acids, and nucleotides boost immune responsiveness after surgery or trauma. l -Arginine is a semiessential amino acid and a precursor of nitric oxide, which is the most important endothelial vasodilator. L-arginine has been shown to improve wound healing, restore postoperative depressed macrophage function and lymphocyte responsiveness, and augment resistance to infections. Intake of additional omega-3 polyunsaturated fatty acids alters cell membrane phospholipid content and prostaglandin synthesis that is theorized as an important factor in suppression of the generalized inflammatory response and subsequent immunosuppression and capillary leakage after major surgery. Elevated omega-3 levels also inhibit the metabolism of arginine. An oral immune-enhancing nutritional supplement taken for 5 days preoperatively has been shown to result in increased preoperative serum arginine concentration and decreased number of postoperative infections with preserved renal function. Similarly, low albumin is also independently associated with major complications that can be improved with preoperative nutrition augmentation. As a component of our enhanced recovery protocol, patients undergoing ventral hernia repair are prescribed a 5-day course of an arginine-based supplement as an immune enhancing measure. Although the impact of this dietary regimen in ventral hernia repair has not been independently studied, the numerous studies demonstrating the benefits in other patient populations cannot be disregarded.

Traditional surgical and anesthesia dogma has required patients to abstain from oral intake for at least 8 hours prior to an elective operation. Despite years of practice, no scientific evidence exists to support the basis for this fast, and in a Cochrane review, there was no evidence to suggest a shortened fluid fast results in an increased risk of aspiration, regurgitation, or morbidity compared with the standard fasting policy. Patients following a standard fast present with depleted glycogen stores in the liver, which increases the demand for amino acids production resulting in protein catabolism following surgical stressors rather than tissue repair. Recent protocols have transitioned to providing a clear fluid that contains a relatively high concentration of complex carbohydrates 2 to 3 hours before induction of anesthesia allowing patients to undergo surgery in a metabolically fed state with adequate glycogen stores. As little as 400 mL of a 12.5% drink of mainly maltodextrins (e.g., Gatorade) reduces preoperative thirst, hunger, anxiety and postoperative insulin resistance, resulting in less postoperative losses of nitrogen and protein and better-maintained lean body mass and muscle strength. Our enhanced recovery protocol includes administration of 32 ounces of a carbohydrate-rich, clear fluid 3 to 4 hours preoperatively as a method of ensuring euvolemia and adequate glycogen stores as elective hernia repair commences.

Methicillin-Resistant Staphylococcus Aureus Prophylaxis

Ventral hernia patients with a history of methicillin-resistant Staphylococcus aureus (MRSA) at any prior location (blood, urine, sputum, wound) experience increased wound infection rates compared with those patients without a history for MRSA. In an effort to decolonize known MRSA carriers or reduce the risk of colony-forming units (CFU) of the skin flora with unknown MRSA status, the use of mupirocin intranasal ointment twice daily combined with chlorhexidine showers for 5 days preoperatively is considered effective with reports of a 44% reduction in SSI. Although decontamination protocols have not been evaluated independently in hernia patients, MRSA decolonization has been investigated as a component of a hernia-enhanced recovery protocol. Identification of patients with a history of MRSA infection often represents the greatest barrier to implementation. As a result, mupirocin and chlorhexidine showers may be prescribed preoperatively to all patients undergoing ventral hernia repair due to the low cost, infrequent side effects, and potential benefit in SSI reduction.

Prevention of Intraoperative Hypothermia

Patients becoming hypothermic (<36°C) have higher rates of wound infection, morbid cardiac events, and bleeding. The maintenance of a patient's temperature, rather than restoration following temperature decreases, is paramount. Normothermia may be accomplished with a suitable warming device and warmed intravenous fluids should be used routinely to keep body temperature greater than 36°C. Monitoring is essential to titrate warming devices and to avoid hyperpyrexia. Warming devices such as forced-air heating blankets and warmed intravenous fluids should be routinely used to keep body temperature greater than 36°C.

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