European Journal of Cardiovascular Medicine

Background: Obesity is associated with altered cardiorespiratory physiology, technical difficulty during surgery and a higher burden of perioperative morbidity. Although the laparoscopic approach offers clear advantages in obese patients, pneumoperitoneum, steep positioning and a thick abdominal wall create unique challenges for the anaesthetist and the surgeon. Aim: To study the spectrum, incidence and risk factors of intraoperative and postoperative complications in obese patients undergoing laparoscopic surgery. Materials and Methods: This prospective observational study included 100 obese adults (BMI ≥30 kg/m²) who underwent elective laparoscopic surgery in the Department of General Surgery of a tertiary care teaching hospital over 12 months (January 2019 to December 2019). Intraoperative events and complications occurring within 30 days of surgery were recorded and graded using the Clavien–Dindo classification. Patients were followed up for six months for port-site hernia. Data were analysed using the chi-square test, ANOVA and logistic regression. Results: The mean age was 41.6 ± 10.8 years, 64% were women and the mean BMI was 34.8 ± 4.1 kg/m². Laparoscopic cholecystectomy was the commonest procedure (46%). At least one intraoperative complication occurred in 38% of patients; hypercarbia (17%), transient hypoxaemia (11%), haemorrhage (9%) and gallbladder perforation (9%) were the most frequent. The conversion rate was 6%. Postoperative complications occurred in 34% of patients, the commonest being surgical site infection (11%) and atelectasis (10%); postoperative nausea and vomiting affected 24%. Intraoperative complication rates rose across BMI classes (29.6%, 40.6% and 64.3%; p = 0.021), as did postoperative complication rates (25.9%, 37.5% and 57.1%; p = 0.028), operative time and hospital stay. BMI ≥35 kg/m² (adjusted OR 2.9) and operative time >90 minutes (adjusted OR 3.8) were independent predictors of complications. There was no mortality. Conclusion: Obese patients can undergo laparoscopic surgery safely, but they have a graded, BMI-dependent increase in anaesthetic, technical and wound-related complications. Careful preoperative optimisation, an anticipatory anaesthetic plan, meticulous access technique and prolonged-surgery vigilance can reduce this burden.

Study design and setting

This was a hospital-based, prospective, observational study conducted in the Department of General Surgery at a tertiary care teaching hospital in India over a period of 12 months, from January 2019 to December 2019. Approval was obtained from the Institutional Ethics Committee before the start of the study, and the study was conducted in accordance with the Declaration of Helsinki [17]. Written informed consent was obtained from every participant after explaining the purpose of the study and the nature of the procedure, and confidentiality of data was maintained.

Sample size

The sample size was calculated using the formula n = Z²pq/d², taking the expected overall complication rate in obese patients undergoing laparoscopic surgery as 30%, a confidence level of 95% (Z = 1.96) and an absolute precision (d) of 9%. This gave a minimum of 100 patients, which was adopted as the study sample. Consecutive eligible patients were enrolled until this number was reached.

Inclusion and exclusion criteria

Adult patients aged 18 years or above with a BMI of 30 kg/m² or more who were scheduled for elective laparoscopic surgery and gave consent were included. BMI was calculated as weight in kilograms divided by the square of height in metres and patients were stratified into three classes: 30–34.9 kg/m² (class I), 35–39.9 kg/m² (class II) and 40 kg/m² or above (class III), in line with the WHO classification, whereas the Asian-specific cut-offs [2,3] were considered in the interpretation of results. Patients undergoing emergency surgery, those with malignancy, pregnant women, patients with ASA physical status IV or above, patients with uncontrolled cardiorespiratory or coagulation disorders and those who refused consent were excluded.

Preoperative evaluation

A detailed history and clinical examination were performed in all patients, recording age, sex, weight, height, waist circumference, comorbid illnesses, tobacco use and previous abdominal surgery. Airway assessment was performed using the modified Mallampati classification [18] and neck circumference, and physical status was graded according to the American Society of Anesthesiologists (ASA) classification [19]. Routine investigations included haemogram, blood sugar, renal and liver function tests, serum electrolytes, coagulation profile, electrocardiogram, chest radiograph and, where indicated, echocardiography, pulmonary function tests and a sleep apnoea screen. Diabetes and hypertension were optimised before surgery, and patients with respiratory disease received chest physiotherapy and incentive spirometry. Antibiotic prophylaxis was administered intravenously 30 minutes before the incision.

Anaesthetic technique

All patients received general anaesthesia with endotracheal intubation. After pre-oxygenation in a ramped (head-up) position, anaesthesia was induced with propofol and fentanyl, and neuromuscular blockade was achieved with a non-depolarising muscle relaxant. Maintenance was with oxygen–air–sevoflurane. Controlled ventilation used a tidal volume of 6–8 mL/kg of ideal body weight with positive end-expiratory pressure of 5–8 cm H₂O, and the respiratory rate was adjusted to maintain end-tidal carbon dioxide (EtCO₂) between 35 and 45 mmHg. Heart rate, blood pressure, SpO₂, EtCO₂, electrocardiogram and airway pressures were monitored continuously. Prophylaxis for postoperative nausea and vomiting (ondansetron with dexamethasone) and multimodal analgesia (paracetamol, a non-steroidal anti-inflammatory drug and local infiltration at port sites) were given to all patients. Patients were extubated awake in a semi-sitting position.

Surgical technique

Pneumoperitoneum was created by the closed (Veress needle) technique at the umbilicus or Palmer’s point, or by the open (Hasson) technique at the discretion of the operating surgeon, with the intra-abdominal pressure limited to 12–14 mmHg. Three to four ports were used according to the procedure, and the patient was positioned according to the operation. All procedures were performed or supervised by surgeons with more than five years’ experience of laparoscopic surgery. Fascial closure was performed for all ports of 10 mm or larger. Conversion to open surgery was defined as any unplanned laparotomy larger than that required for specimen retrieval. Mechanical thromboprophylaxis was used in all patients and low-molecular-weight heparin was added in those at high risk, and early ambulation was encouraged.

Outcome measures and definitions

Intraoperative complications were recorded prospectively by an independent observer. Hypoxaemia was defined as SpO₂ below 90% for more than one minute; hypercarbia as EtCO₂ above 45 mmHg requiring a ventilator adjustment; hypotension as a mean arterial pressure below 65 mmHg or a fall of more than 20% from baseline requiring treatment; and difficult intubation as a Cormack–Lehane grade III or IV view or the need for more than two attempts or an adjunct. Haemorrhage was defined as blood loss exceeding 100 mL or bleeding needing an additional haemostatic manoeuvre. Visceral injury, gallbladder perforation with spillage, difficulty in establishing pneumoperitoneum, subcutaneous emphysema and conversion were also noted.

Postoperative complications were recorded for 30 days after surgery. Surgical site infection (SSI) was defined according to standard criteria [20]. Postoperative nausea and vomiting (PONV) and shoulder-tip pain were recorded separately as expected minor sequelae of laparoscopy and anaesthesia [21], and were not counted among the complications used for rate calculation. Complications were graded according to the Clavien–Dindo classification [22], and the duration of hospital stay and any readmission were noted. Patients were followed up in the outpatient clinic at 2 weeks, 30 days and 6 months, the last visit being used to detect port-site hernia clinically and, when in doubt, by ultrasonography.

Statistical analysis

Data were entered in Microsoft Excel and analysed with SPSS version 20.0 (IBM Corp., Armonk, NY). Continuous variables are expressed as mean ± standard deviation and categorical variables as numbers and percentages. Categorical variables were compared with the chi-square test or Fisher’s exact test, and continuous variables across BMI classes with one-way analysis of variance. The association of risk factors with complications was expressed as odds ratio (OR) with 95% confidence interval (CI), and variables with p < 0.10 in univariate analysis were entered into a multivariable logistic regression model. A p value below 0.05 was considered statistically significant.

Baseline characteristics

A total of 100 obese patients were included and all completed the 30-day follow-up; 94 patients attended the six-month review. The mean age was 41.6 ± 10.8 years (range 20–68 years), and the largest group (31%) was aged 31–40 years. There was a female preponderance (64 women and 36 men; female:male ratio 1.8:1). The mean BMI was 34.8 ± 4.1 kg/m² (range 30.2–47.6), with 54 patients in class I, 32 in class II and 14 in class III obesity. Hypertension (38%) and type 2 diabetes mellitus (29%) were the most frequent comorbidities, and 30% of patients were ASA grade III (Table 1).

Table 1: Baseline characteristics of the study population (n = 100)

SD, standard deviation; BMI, body mass index; COPD, chronic obstructive pulmonary disease; ASA, American Society of Anesthesiologists. Comorbidities are not mutually exclusive.

Procedures performed

Laparoscopic cholecystectomy was the commonest operation (46%), followed by laparoscopic ventral or incisional hernia repair with intraperitoneal mesh (18%), gynaecological procedures (14%), laparoscopic inguinal hernia repair (8%), sleeve gastrectomy (8%) and appendicectomy (6%). The mean operative time was 78.1 ± 26.2 minutes. Six procedures (6%) were converted to open surgery. The reasons for conversion were dense adhesions (2 patients), poor exposure or unclear anatomy because of visceral fat (2), uncontrolled bleeding (1) and recognised small-bowel injury (1). Overall, 52 patients (52%) developed at least one intraoperative or postoperative complication (Table 2).

Table 2: Distribution of procedures, conversion and overall complications

IPOM, intraperitoneal onlay mesh; TEP, totally extraperitoneal; TAPP, transabdominal preperitoneal. “Any complication” includes intraoperative or postoperative complications.

Intraoperative complications

At least one intraoperative complication occurred in 38 patients (38%), with a total of 80 events, indicating that several patients had more than one problem. Anaesthetic and physiological problems were the most frequent group: hypercarbia requiring ventilator adjustment (17%), transient hypoxaemia (11%), difficult laryngoscopy or intubation (9%), hypotension (8%) and arrhythmia (5%). Among surgical complications, haemorrhage (9%) and gallbladder perforation with bile spillage (9 of 46 cholecystectomies; 19.6%) were commonest, followed by difficulty in establishing pneumoperitoneum needing conversion to open (Hasson) entry (7%), subcutaneous emphysema (4%) and a single bowel injury (1%) that was recognised and repaired (Table 3).

Table 3: Intraoperative complications (n = 100)

*Percentage calculated among the 46 patients undergoing cholecystectomy; the event is counted as 9% of the whole series in the total. Percentages for other events are of all 100 patients.

Postoperative complications

Postoperative complications (excluding PONV and shoulder-tip pain) occurred in 34 patients (34%), with 40 events in total. Surgical site infection was the commonest (11%; 9 superficial and 2 deep), followed by pulmonary atelectasis or prolonged oxygen requirement (10%), urinary retention or urinary infection (4%), seroma (3%), paralytic ileus (3%) and port-site hernia (3 of 94 patients reviewed at six months; 3.2%). Haematoma, pneumonia, one bile leak and one deep vein thrombosis made up the remainder (Table 4). Among the expected minor sequelae, PONV occurred in 24% and shoulder-tip pain in 18%. The mean hospital stay was 3.7 ± 1.8 days, four patients (4%) were readmitted within 30 days and two (2%) required reoperation. There was no mortality.

Table 4: Postoperative complications within 30 days (n = 100)

Complications according to the degree of obesity

Both the operative burden and the complication rate increased with BMI class (Table 5, Figure 1). The mean operative time rose from 70.2 minutes in class I to 98.5 minutes in class III (p < 0.001). Intraoperative complications occurred in 29.6%, 40.6% and 64.3% of patients in classes I, II and III, respectively (p = 0.021), and postoperative complications in 25.9%, 37.5% and 57.1% (p = 0.028). Conversion and surgical site infection showed the same upward trend, although the numbers were too small to reach statistical significance. Hospital stay was significantly longer in patients with higher BMI (p = 0.001).

Table 5: Operative and outcome parameters according to BMI class

p values: one-way ANOVA for continuous variables; chi-square (trend) or Fisher’s exact test for categorical variables.

Severity of postoperative complications

Using the Clavien–Dindo classification, most complications were minor: grade I in 14 patients and grade II in 13 patients (together 79.4% of those with complications). Grade IIIa complications (4 patients) comprised port-site and deep collections drained under local anaesthesia, and grade IIIb complications (2 patients) were one relaparoscopy and washout for a bile leak and one wound debridement under anaesthesia for deep infection. One patient with pneumonia required ventilatory support in the intensive care unit (grade IVa). There was no grade V complication (Table 6).

Table 6: Clavien–Dindo grading of postoperative complications (n = 34 patients)

Risk factors for complications

On univariate analysis, BMI of 35 kg/m² or more, diabetes mellitus, ASA grade III and an operative time of more than 90 minutes were significantly associated with the occurrence of any complication, whereas age above 50 years and female sex were not (Table 7). In the multivariable logistic regression model, BMI ≥35 kg/m² (adjusted OR 2.9; 95% CI 1.2–7.1; p = 0.019) and operative time >90 minutes (adjusted OR 3.8; 95% CI 1.4–10.2; p = 0.008) remained independent predictors of complications, while diabetes and ASA grade III lost significance after adjustment.

Table 7: Univariate analysis of risk factors for any complication (n = 52 of 100)

OR, odds ratio; CI, confidence interval. Reference category is the group without the factor.

Laparoscopic surgery is now offered routinely to obese patients, yet this group remains a high-risk population in which the benefits of minimal access surgery must be balanced against the physiological cost of pneumoperitoneum and the technical cost of a thick abdominal wall. In this prospective series of 100 obese patients, 38% had at least one intraoperative complication and 34% developed a postoperative complication, most of which were minor. The conversion rate was 6%, the reoperation rate 2% and there was no mortality. More importantly, the risk of complications rose in a graded fashion with increasing BMI, and BMI of 35 kg/m² or above and a long operative time emerged as independent predictors of an adverse course. These findings are consistent with the general observation that obesity increases perioperative morbidity, particularly in terms of wound and respiratory complications, without making laparoscopy unsafe [10,11].

The mean age of our patients was 41.6 years and nearly two-thirds were women. A female preponderance among obese patients undergoing laparoscopy is expected because the commonest procedure, cholecystectomy, is itself more frequent in obese women, and women also present more often for gynaecological and bariatric operations. Hypertension and diabetes were present in 38% and 29% of our patients, which agrees with the clustering of cardiometabolic risk factors described in urban Indian populations [6,7]. The fact that nearly one-third of our patients were ASA grade III underlines that the comorbid burden, not only the BMI, determines the anaesthetic risk. Indian authors have stressed that surgical decision-making in this population should take into account the lower BMI thresholds at which metabolic disease develops [3,16]; in our series, even patients in the 30–34.9 kg/m² class had a complication rate of nearly 30%, which supports this view.

Anaesthetic and physiological events were the most frequent intraoperative problems. Carbon dioxide pneumoperitoneum is absorbed across the peritoneum and, together with the cephalad displacement of the diaphragm, raises arterial carbon dioxide tension and reduces respiratory compliance, effects which are magnified in the obese [23,24]. Obese patients have an elevated baseline intra-abdominal pressure that correlates with abdominal diameter [25], so that the insufflation pressure that is well tolerated in a lean patient may produce a much larger physiological disturbance. The hypercarbia (17%) and hypoxaemia (11%) that we observed were generally transient and managed by adjusting minute ventilation, increasing PEEP, recruitment manoeuvres or temporarily reducing the insufflation pressure, but they illustrate why close monitoring is essential. The haemodynamic changes reported in morbidly obese patients under pneumoperitoneum are also relevant to our observations of hypotension and arrhythmia.

Difficult laryngoscopy or intubation occurred in 9% of our patients. Obesity is associated with more frequent difficult intubation than in lean patients [26], although BMI alone is a poor predictor and neck circumference and a high Mallampati score are better indicators [27]. We therefore routinely recorded neck circumference and Mallampati grade, used the ramped position and had difficult-airway equipment ready, and no patient came to harm from airway difficulty. A structured airway assessment is a simple and effective strategy that all centres can adopt.

Technical complications were also more frequent than would be expected in lean patients. Difficulty in establishing pneumoperitoneum occurred in 7% of cases and was solved by open entry. In obese patients the position of the umbilicus relative to the aortic bifurcation is altered, so that the umbilicus lies lower than the bifurcation and the angle of needle insertion must be adapted accordingly [28]. Reviews of laparoscopic entry have shown that no single technique is free of risk and that most major vascular and visceral injuries occur at the time of entry [29]; large series of gastrointestinal injuries during laparoscopy similarly emphasise that they usually occur at primary access and are often recognised late [30]. The single bowel injury in our series was recognised during the procedure and repaired, but it led to conversion. We believe that an open or optical-trocar entry, strict attention to the angle of insertion and a low threshold for conversion reduce the risk of catastrophic access injury.

Bleeding (9%) and gallbladder perforation with bile spillage (19.6% of cholecystectomies) reflect the technical difficulty arising from a fatty hilum, an enlarged liver and limited exposure. The conversion rate of 6% was higher in the class III group (14.3%) than in the class I group (3.7%). Conversions were largely due to poor exposure, adhesions and bleeding and not to anaesthetic intolerance of pneumoperitoneum, which is reassuring. Our conversion rate compares well with the experience of Indian high-volume laparoscopic centres in complex cases such as ventral hernia repair, where careful patient selection and experience allow a laparoscopic approach in most patients [31]. Large bariatric series likewise show that laparoscopic surgery can be performed with acceptable complication and conversion rates in the heaviest patients when performed by trained teams.

The postoperative morbidity of 34% in our series was dominated by wound and pulmonary events. Surgical site infection, the commonest complication (11%), is well known to be more frequent in obese patients, as shown by early evidence of an increased nosocomial infection rate in obese surgical patients [32] and by later work showing that the proportion of body fat predicts the occurrence of surgical site infection [33]. Poor penetration of antibiotics into adipose tissue, a large subcutaneous dead space, prolonged operating time, diabetes and difficulty in obtaining tissue perfusion are the likely mechanisms. Our SSI rate rose from 7.4% in class I to 21.4% in class III, although the difference was not statistically significant owing to the small numbers. In keeping with the available studies, wound complications were far less frequent than would be expected after an equivalent open operation, which remains a strong argument for the laparoscopic approach in obese patients.

Pulmonary atelectasis was found in 10% of our patients. Obesity predisposes to atelectasis during anaesthesia because of reduced functional residual capacity and in morbidly obese patients atelectasis may persist well into the postoperative period, so that its frequency is often underestimated [34]. The use of positive airway pressure or PEEP during induction and pre-oxygenation has been shown to reduce atelectasis formation in these patients [35], and the use of PEEP, recruitment, head-up positioning and early incentive spirometry in our protocol probably limited the severity of the problem. Only two patients developed pneumonia and one required intensive care, which highlights the importance of preoperative respiratory optimisation in those with asthma, COPD and obstructive sleep apnoea.

Nausea and vomiting affected 24% of our patients despite prophylaxis. Female sex, non-smoking status, a history of motion sickness and the use of postoperative opioids are the key predictors of PONV and our series, which is predominantly female and non-smoking, falls in a high-risk category. Laparoscopic surgery itself is an additional risk factor. Shoulder-tip pain (18%) is a recognised consequence of residual carbon dioxide under the diaphragm and may be reduced by using the lowest effective pressure, evacuating the gas fully and giving early mobilisation.

Port-site hernia occurred in 3.2% of those reviewed at six months. A systematic review of trocar-site hernia identified obesity, large port size, long operating time and failure to close the fascia as risk factors [36], and the fact that all our patients had a closure of the fascia at 10 mm ports and larger probably limited the problem; nevertheless, in obese patients the fascial closure is technically difficult and the use of a fascial closure device should be considered. Thromboembolic complications were uncommon (a single deep vein thrombosis), but obesity is a recognised risk factor, and venous thromboembolism after laparoscopic bariatric surgery has a recognised clinical burden even though the absolute risk is low and prophylaxis is effective [37]. We continue to recommend mechanical prophylaxis for all and pharmacological prophylaxis for high-risk patients.

Nearly 80% of our postoperative complications were Clavien–Dindo grade I or II, and major complications (grade III or higher) occurred in 7% of the series. This corresponds with the observation in a large prospective multicentre bariatric cohort that, although serious adverse outcomes were uncommon, they were concentrated in patients with specific risk factors such as a history of venous thromboembolism, obstructive sleep apnoea, a very high BMI and poor functional status [38]. Our own analysis supports the principle that risk stratification before surgery is more useful than a blanket judgement based on obesity alone.

In our series, BMI of 35 kg/m² or more and an operative time of more than 90 minutes were independent predictors of complications. The relation between BMI and operative difficulty is evident, since increasing visceral fat and abdominal wall thickness lengthen the operation, and the longer duration prolongs pneumoperitoneum, increases exposure to carbon dioxide and anaesthetic agents, and increases the risk of infection. Diabetes and ASA grade III were associated with complications on univariate analysis only, which suggests that they act partly through BMI and operative duration. These results emphasise that the surgical team can modify the most important risk factor, namely time, by good case selection, by experienced operators and by early conversion when progress is poor.

Several practical measures follow from our observations. First, preoperative optimisation of diabetes, hypertension and respiratory status is essential and should be coupled with counselling about weight loss where time permits. Second, the anaesthetic plan should anticipate a difficult airway and use ramped positioning, adequate pre-oxygenation, PEEP and lung-protective ventilation. Third, insufflation should be done at the lowest pressure that provides adequate exposure, with a careful and individualised access technique. Fourth, a multimodal, opioid-sparing analgesic and antiemetic regimen and early mobilisation, in the spirit of enhanced recovery principles, shorten recovery and reduce pulmonary and thromboembolic problems [39]. Finally, wound care measures such as appropriately weight-adjusted antibiotic dosing, careful subcutaneous haemostasis and fascial closure of larger ports should be emphasised in obese patients.

Strengths and limitations

The strengths of this study are its prospective design, the use of standard definitions and the Clavien–Dindo grading, independent recording of intraoperative events and a six-month follow-up for port-site hernia. The limitations include a single-centre setting, a modest sample size that reduces the power to detect differences in uncommon events (for example conversion and surgical site infection across BMI classes), the heterogeneity of the procedures, and the absence of a non-obese control group, which prevents a direct estimate of the excess risk attributable to obesity. In addition, the Asian-specific BMI categories were not used for the primary stratification. Larger multicentre studies with a matched control group are required to confirm our findings.

Laparoscopic surgery can be performed safely in obese patients, with no mortality and mostly minor complications in this series. However, anaesthetic, technical and wound-related complications are common and increase progressively with the degree of obesity, and BMI of 35 kg/m² or more and prolonged operative time are the main predictors of an adverse outcome. A systematic approach comprising preoperative optimisation, an anticipatory anaesthetic strategy, careful access technique, efficient operating and meticulous wound and thromboembolism prophylaxis should be the standard of care for obese patients scheduled for laparoscopic surgery. Surgeons should weigh patient selection and operator experience carefully in patients with class II and III obesity.

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