Postoperative Pain Following Bariatric Surgery: Correlation Between Intensity and Clinical-Surgical Variables

Abstract

Purpose:

To quantify and analyze the relation between the intensity of pain and clinical-surgical variables in the immediate postoperative period of patients submitted to laparoscopic bariatric surgery.

Methods:

Prospective observational study, done with obese patients submitted to laparoscopic bariatric surgery who had presented intense pain according to the visual analog scale and also postoperative nausea and vomiting in two distinct moments: in the postanesthesia care unit (PACU) and at the first postoperative day (1st POD).

Results:

The sample was predominantly female, body mass index ≥40, age between 31 and 45 years, nonsmoker nor alcoholic. It was observed that there was a significant reduction from intense pain (PACU) to moderate and mild (1st POD). A difference was observed in the intensity of pain between patients without surgical records (41.0%) and those with no history of postoperative acute pain (34.1%). There was no statistical significance in the correlation of surgical variables and the prevalence of postoperative intense pain. The correlation between high anxiety levels with surgeries and postoperative pain was verified.

Conclusion:

Intense pain was observed in the PACU. There was a significant reduction to moderate and mild in the 1st POD. Previous surgeries and history of postoperative acute pain were identified as protection factors for postoperative pain.

Introduction

Pain is a by-product of the interaction between the individual and the environment. Its interpretation is deeply related to previous experiences and subjective values, such as culture and social relationships.¹ Its concept overtakes that of a simple inconvenience and implies a massive cascade of physiological reactions that grows even more complex and important in patients submitted to surgical procedures. Hence, the inappropriate treatment of the postoperative pain represents an important clinical problem, resulting not only in worse outcomes at the immediate postoperative period, but also in greater risks of developing persistent postoperative pain later on.²

The pain management is of particular relevance among the obese population, due to their high susceptibility of perioperative complications, such as cardiovascular, thromboembolic, and pulmonary events.³ These conditions account for the higher mortality rates observed during the postoperative period among obese patients when compared with the nonobese population.⁴

The obese population is increasing worldwide and so is the number of bariatric surgeries performed.⁵ Bariatric surgery appears to be the mainstay of treatment for obesity and its metabolic complications when the drug therapy fails.⁶ This procedure promotes massive weight loss along with normalization of glycemic metabolism in patients with type 2 diabetes mellitus.^5,6

Postoperative nausea and vomiting (PONV) are some of the most important causes of patient dissatisfaction after bariatric surgery. Exaggerated anxiety and the postoperative pain, especially when it is originated in the pelvic or visceral regions, can also lead to a greater incidence of PONV.⁷

The consequences of PONV are delay in the discharge from the postanesthesia care unit (PACU), increased incidence of pulmonary aspiration, and significant postoperative discomfort. These aspects, likewise the physiological repercussions of the postoperative pain, limit the early deambulation and delay the hospital discharge.⁷

Thus, the purpose of this study was to identify the link between pain intensity and clinical-surgical variables during the immediate postoperative period of patients submitted to laparoscopic bariatric surgery. Furthermore, the investigation of a possible connection between postoperative pain intensity and the profile of the obese patients, alongside factors associated with the perioperative period, can add evidence for the guidelines regarding the management of these parameters in the bariatric population.

Materials and Methods

This study was performed at Hospital das Clínicas, Federal University of Pernambuco, Recife, Pernambuco, Brazil, during the period between 2015 and 2018, when 204 obese patients submitted to laparoscopic bariatric surgery were analyzed. Postoperative pain was assessed through a visual analog scale (VAS), and, alongside with PONV, was assessed in two different moments: in the PACU and 24 h after the surgery or first postoperative day (1st POD). Based on the clinical history of the patients, a database was created to analyze the clinical-surgical variables.

This study enrolled patients with formal indication for bariatric surgery [body mass index (BMI) between 30 and 34.9 kg/m² associated with a severe comorbidity; BMI between 35 and 39.9 kg/m² associated with at least one comorbidity; BMI ≥40 kg/m²], with age between 16 and 70 years and no gender distinction The included patients underwent laparoscopic bariatric surgery by vertical gastrectomy (Sleeve) or Roux-en-Y gastric bypass (RYGB). Patients who presented any complications during the perioperative or postoperative periods, such as surgical site infection and gastrojejunostomy leak, were excluded from the study.

Intensity of pain

The VAS is designed to quantify the intensity of pain in a simple and objective way. VAS is a numerical and unidirectional scale that ranges from 0 to 10 (0–2 is no or mild pain; 3–7 is moderate pain; 8–10 is intense pain). It was required of the patients to match the score that best describes the pain intensity during each moment of the evaluation.

Statistical analysis

Data were quantified and presented in tables with their respective absolute and relative frequencies. Continuous variables were presented as measures of central tendency and dispersion. For the comparison between the levels of pain in the two moments of evaluation, a table of contingency was made and the chi-square test of homogeneity was applied. For the correlation between the intensity of pain and the clinical-surgical profile of the patients, the chi-square test for comparison and proportion was performed. All of the interpretations were made taking into consideration the significance level of 5%.

This research project was approved by the Ethics Committee for Research involving human beings of the Federal University of Pernambuco's Center of Health Sciences (No. 859.739) CAAE: 5606.3816.6.0000.5208. Informed Consent was obtained from all individual participants included in the study.

Results

Women prevailed in this study (70.1%) with age range from 31 to 45 years (49.8%) and class III obesity (48.0%). It was observed that the proportion comparison test was significant for all analyzed factors (p < 0.001). It was verified that the majority of patients were nonalcoholic (67%), nonsmokers (91.2%), nondiabetic (76.7%), and nonhypertensive (52.2%). Despite the fact that most of them denied motion sickness (76.0%), the majority referred chronic pain (78.4%) and declared chronic use of analgesic drugs (70.6%). Still, it was observed that the proportion comparison test was significant for all parameters (p < 0.001), except for hypertension (p = 0.528), indicating that the aforementioned profile is statistically relevant.

Table 1 exhibits the comparison between the intensity of pain in the two moments of evaluation (PACU and 1st POD). It was verified, at the PACU, that intense pain was the most prevalent pattern (41.7%), contrasting with the 1st POD, where moderate and mild pain were more prevalent (35.8%). The homogeneity test showed statistical significance (p = 0.019), indicating reduction of pain levels at the 1st POD when compared with the evaluation at the PACU.

Table 1.

Comparison Between the Intensity of Pain in Two Moments of Evaluation (Postanesthesia Care Unit and First Postoperative Day)

Intensity	Moments		p ^*
Intensity	PACU, n (%)	1st POD, n (%)	p ^*
Intense	85 (41.7)	58 (28.4)	0.019
Moderate	57 (27.9)	73 (35.8)
Mild	62 (30.4)	73 (35.8)

p-Value of chi-square test for homogeneity.

1st POD, first postoperative day; PACU, postanesthesia care unit.

Table 2 shows the relation between the clinical variables and the intensity of pain at the 1st POD. It was verified that patients who had never been submitted to surgeries (41.0%) and those who had never had previous postoperative acute pain (34.1%) presented intense pain in the 1st POD (p < 0.5). The other variables presented no statistical significance.

Table 2.

Relation Between Clinical Variables and Pain Intensity in the First Postoperative Day

Factor	Intensity			Total	Prevalence of intense pain	p^*
Factor	Intense	Moderate	Mild	Total	Prevalence of intense pain	p^*
Gender, n (%)
Men	18 (29.5)	28 (45.9)	15 (24.6)	61	29.5	0.824
Women	40 (28.0)	45 (31.5)	58 (40.6)	143	28.0	0.824
Age, n (%)
≤30 years	22 (38.6)	22 (38.6)	13 (22.8)	57	38.6	0.250
31–45 years	26 (25.4)	38 (37.3)	38 (37.3)	101	25.4
46–59 years	9 (22.0)	13 (31.7)	19 (46.3)	41	22.0
≥60 years	1 (25.0)	0 (0.0)	3 (75.0)	4	25.0
BMI, n (%)
Overweight	0 (0.0)	0 (0.0)	2 (100.0)	2	0.0	0.911
Obesity class I	3 (33.3)	4 (44.4)	2 (22.2)	9	33.3
Obesity class II	28 (29.5)	33 (34.7)	34 (35.8)	95	29.5
Obesity class III	27 (27.6)	36 (36.7)	35 (35.7)	98	27.6
Smoker, n (%)
Yes	3 (16.7)	5 (27.8)	10 (55.6)	18	16.7	0.247
No	55 (29.6)	68 (36.6)	63 (33.9)	186	29.6	0.247
Diabetes, n (%)
Yes	12 (25.0)	12 (25.0)	24 (50.0)	48	25.0	0.547
No	46 (29.5)	61 (39.1)	49 (31.4)	156	29.5	0.547
Hypertension, n (%)
Yes	26 (26.8)	29 (29.9)	42 (43.3)	97	26.8	0.624
No	32 (29.9)	44 (41.1)	31 (29.0)	107	29.9	0.624
Chronic pain, n (%)
Yes	46 (28.8)	52 (32.5)	62 (38.8)	160	28.8	0.847
No	12 (27.3)	21 (47.7)	11 (25.0)	44	27.3	0.847
Chronic use of analgesics, n (%)
Yes	39 (27.1)	50 (34.7)	55 (38.2)	144	27.1	0.508
No	19 (31.7)	23 (38.3)	18 (30.0)	60	31.7	0.508
Previous surgeries, n (%)
Yes	26 (20.6)	43 (34.1)	57 (45.2)	126	20.6	0.001
No	32 (41.0)	30 (38.5)	16 (20.5)	78	41.0	0.001
Previous acute postoperative pain, n (%)
Yes	2 (5.0)	20 (50.0)	18 (45.0)	40	5.0	<0.001
No	56 (34.1)	53 (32.3)	55 (33.5)	164	34.1	<0.001

p-Value of chi-square test for proportion comparison (if p-value <0.05 [in bold] the proportions differ significantly).

BMI, body mass index.

Table 3 exhibits the relation between surgical variables and intensity of pain registered in the 1st POD. There was no significant statistical difference between these parameters.

Table 3.

Relation Between the Surgical Variables and the Pain Intensity in the First Postoperative Day

Factor	Intensity—VAS			Total	Prevalence of intense pain	p^*
Factor	Intense	Moderate	Mild	Total	Prevalence of intense pain	p^*
Surgical technique, n (%)
Sleeve	49 (31.6)	57 (36.8)	49 (31.6)	155	31.6	0.073
Bypass	9 (18.4)	16 (32.7)	24 (49.0)	49	18.4	0.073
Drain use, n (%)
Yes	14 (34.1)	16 (39.0)	11 (26.8)	41	34.1	0.333
No	43 (26.5)	57 (35.2)	62 (38.3)	162	26.5	0.333
Previous PONV, n (%)
Yes	7 (17.1)	19 (46.3)	15 (36.6)	41	17.1	0.071
No	51 (31.3)	54 (33.1)	58 (35.6)	163	31.3	0.071
Present PONV, n (%)
Yes	42 (32.6)	54 (41.9)	33 (25.6)	129	32.6	0.087
No	16 (21.3)	19 (25.3)	40 (53.3)	75	21.3	0.087

p-Value of chi-square test for proportion comparison (if p-value <0.05 the proportions differ significantly).

PONV, postoperative nausea and vomiting; VAS, visual analog scale.

Discussion

To analyze the great variability of postoperative pain,⁸ the characteristics of the studied group, such as age, gender, experience of the doctor, and the surgical technique performed must be considered.

Intense postoperative pain was more frequent in the PACU (41.7%), whereas at the 1st POD, moderate and mild pain was more prevalent (35.8% both). Silva et al. (n = 84) obtained similar results regarding the occurrence of intense pain in the PACU (38.3%).⁹ According to the guidelines of the American Society of Anesthesiologists, the routine monitoring of pain contributes to decrease adverse outcomes during the postoperative period.¹⁰

Reduction of pain level, from intense to moderate, between the PACU and the 1st POD was also significant (p = 0.019), contrasting to a study of 50.523 patients, where the highest pain levels were registered in the 1st POD.¹¹

A revision performed by Oliveira demonstrated that midsize surgical procedures, including some laparoscopic approaches, might result in unexpectedly high levels of postoperative pain.¹² In 2014, another study found that 75% of patients presented moderate/intense pain during the immediate postoperative period, and 74% presented different levels of pain even after being discharged from the hospital.¹³ Therefore, the inclusion of the pain scores obtained in the 1st POD and its correlations with the clinical and surgical variables, regardless of the statistical relevance (28.4%), are plausible.

In the infirmary, nurses are essential professionals between the patient and the medical staff. One task that must be accomplished is to identify the moment of maximum pain; which symptoms are important and which are not; and which are evidence of negligence and what kind of negligence.¹⁴

The relationship of previous surgical procedures and acute postoperative pain episodes was shown to indicate the prevalence of intense pain. In this study, intense pain was found in 41% of those patients who experienced previous surgeries, and in 34.1% of those with history of acute postoperative pain. An improved preoperative preparation, well discussed with the patient, might result in milder levels of postoperative pain, given that the patient will be oriented and aware of the natural evolution of the postoperative period.

Regarding patient's habits, smoking did not present statistical relevance to the intensity of pain, as was also shown by previous published studies involving obese patients after bariatric surgery.¹⁵

Although it is imperative to have a strategy for prevention and treatment of pain, other postoperative complications in bariatric surgery deserve attention. Postoperative vomiting, for example, occurs in ∼30% of all surgeries.⁷ To Chatterjee et al., BMI >30 is associated with PONV in the postoperative period of surgeries.¹⁶

Apart from independent risk factors of each patient, increased intra-abdominal pressure and the pharmacokinetic effects of the lipophilic anesthetic agents must be considered.¹⁷ Other factor that must be discussed is the relation between PONV and postoperative pain. This research results did not indicate statistical difference, whereas Apfel et al. identified, in a prospective study involving 520 patients, four risk factors for PONV (female gender, previous episodes of PONV, nonsmokers, and postoperative use of opioids).¹⁸ In this research there was a predominance of women (70.1%) and nonsmokers (91.2%). This added to the fact that 76% did not present motion sickness, it contradicts the concepts that PONV are directly related to surgery duration, being more prevalent in women, nonsmokers, and those with a previous history of PONV or motion sickness.¹⁵

Owing to the inexistence of a structured protocol for postoperative pain management in the institution where this research took place, and due to the lack of formal training of health professionals to investigate and evaluate the postoperative pain, this study used an autonomous research protocol. The main limitation of this study is that intraoperative opioid administration and postoperative opioid consumption were not standardized.

Conclusion

Intense pain was largely reported after laparoscopic bariatric surgery, especially in the PACU. An unpredicted reduction in the 1st POD was also detected. Also, previous surgeries together with the occurrence of previous acute postoperative pain can correlate with the intensity of postoperative pain, potentially being identified as protection factors.

For better evaluation, it is relevant to manage the signs of postoperative pain intensity, making possible an overall improvement of the patient's condition.

Footnotes

Author Disclosure Statement

The authors declare no potential conflicts of interest.

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