Physiological and Anesthetic Considerations of Safe and Optimal Pneumoperitoneal Pressures for Laparoscopic Surgeries in Children

ABSTRACT

Context:

In the era of minimally invasive surgeries, pediatric laparoscopic surgeries are now becoming the standard of care.

Aim:

In this study, we aim to determine the safe and optimal pneumoperitoneal pressures (PPs) for laparoscopic surgery in children aged 1–5 years, along with the technical ease for the surgeon.

Settings and Design:

Prospective, randomized, single-blinded study was conducted at SGPGI Lucknow.

Materials and Methods:

Children aged 1–5 years were randomized into Group I (n = 24): PP = 6–8 mmHg and Group II: (PP) = 9–10 mmHg. Hemodynamic, ventilatory, and blood gas changes were measured before CO₂ insufflation (T0), 20 min after insufflation (T1), before desufflation (T2), and 10 min after desufflation (T3). Surgeon’s technical ease of surgery, postoperative pain, the requirement of rescue analgesia, time to resume feeding, and complications were recorded and analyzed.

Statistical Analysis Used:

Paired t-test, Mann–Whitney test, and Wilcoxon signed-rank test were used for nonparametric/parametric data. Chi-square/Fisher’s test was used for nominal data.

Results:

Partial pressure of CO₂ (PaCO₂) was significantly higher in Group II at T1, T2, and T3, requiring frequent changes in ventilatory settings. Postoperative pain scores were higher in Group II at 1, 6, and 12 h, requiring rescue analgesia. Surgeon’s scores and hemodynamics were similar in both groups.

Conclusions:

Higher PP in Group II caused significant changes in PaCO₂, end-tidal CO₂, and postoperative pain requiring rescue analgesia, but blood gas changes were clinically insignificant and there were no significant changes in hemodynamic parameters. Since the surgeon’s ease of performing surgery was similar in both groups, we recommend that laparoscopy in children aged 1–5 years can be started with lower PPs of 6–8 mmHg, which can be increased if needed based on the surgeon’s comfort and the patient’s body habitus.

INTRODUCTION

In the era of minimally invasive surgery, pediatric laparoscopic surgeries are now the standard of care. Pneumoperitoneum is essential for performing laparoscopy, but it is associated with various physiological effects, especially in the pediatric population. It is a complex physiological event with a profound impact on homeostasis. Children are not miniature adults, and hence, adult recommendations cannot simply be extrapolated to the pediatric population.[1] A range of pneumoperitoneal pressures (PPs) varying from 5 to 15 mmHg is commonly used in infants and children for laparoscopic procedures, with variable physiological responses.[2,3,4,5,6] Surgeons are concerned about the adequacy of working space and operative ease, whereas anesthetists are concerned about safe ventilation with pneumoperitoneum to minimize physiological hazards.[7] The present study aims at determining the safe and optimal PPs in children aged 1–5 years, along with the technical ease for the surgeon in performing various pediatric laparoscopic surgeries at a tertiary care center.

MATERIALS AND METHODS

This prospective, randomized, single-blind study was conducted at a tertiary care center in North India between November 2020 and June 2022. The study protocol was reviewed, approved, and monitored by the institutional ethics committee. Informed parental consent was obtained before participation.

Study participants

Out of a total of 54 pediatric patients between the age of 1–5 years undergoing elective laparoscopic surgery, 52 were randomized into two groups by computer-generated number according to the range of PP: Group I included PP of 6–8 mmHg and Group II included PP of 9–10 mmHg. Out of these 52 patients, four patients were excluded: two converted to open surgery due to the difficult anatomy, one was excluded due to malfunction of the arterial blood gas analysis machine, and in one patient, we had to decrease PP. The remaining 48 patients were randomized to two groups with 24 patients each, and these were then considered for the final analysis [Figure 1].

Figure 1.

Study protocol flow chart

Study design

After shifting the patient in the operation theater, standard monitoring was applied, which included a five-lead electrocardiogram, automated noninvasive blood pressure monitoring, and pulse oximeter. Anesthesia was induced with thiopental sodium 4 mg/kg and fentanyl citrate 3 μg/kg. After adequate preoxygenation, tracheal intubation was done with atracurium besylate 0.5 mg/kg. Anesthesia was maintained with a sevoflurane air/O₂ mixture (FiO₂ = 0.4) using volume-controlled mode at I: E ratio of 1:2. Children were ventilated using a tidal volume of 8 mL/kg, positive end-expiratory pressure of 3 cmH₂O, and respiratory rate (RR) was adjusted to achieve normocarbia (end-tidal CO₂ [EtCO₂] 40 mmHg). After achieving normocarbia, the first port was inserted under direct vision by open technique, and then the peritoneum was insufflated with CO₂ using electronic insufflator (Karl Storz GmbH and Co. KG, Tuttlingen, Germany) with an initial flow rate of 0.5–1 L/min in all patients to achieve the desired pressures according to their randomization to Group I or II. The ventilatory settings were then not adjusted till after 25 min of establishing pneumoperitoneum. An arterial line was inserted in the radial artery with a 22–24G cannula for hemodynamic monitoring and blood gas analysis. Hemodynamic, respiratory, and blood gas changes were measured at four points: before CO₂ insufflation (T0), 20 min after insufflation (T1), before desufflation (T2), and 10 min after desufflation (T3). A nasogastric tube was also placed to decompress the stomach.

The parameters measured included heart rate (HR), mean arterial pressure (MAP), pH, arterial partial pressure CO₂ (PaCO₂), and EtCO₂. The number of times the ventilator settings needed to be changed after 25 min of pneumoperitoneum was recorded. During surgery, all children received an isotonic electrolyte solution (N/2 saline in 5% dextrose). At the end of the surgical procedure, neuromuscular blockade was reversed with intravenous neostigmine 50 μg/kg and glycopyrrolate 30 μg/kg. Postoperative pain was assessed using FLACC behavioral pain assessment model at 1, 6, and 12 h and the time to resume feeding was also recorded.

To assess optimal PP from the surgeon’s point of view, we evaluated the technical feasibility of performing the procedure at the allocated PP using the five-point rating scale[8] as shown in Table 1. Blinding of the surgeon to the Pneumoperitoneal Pressures was done by covering the set pressure visible on the insufflator machine with a cardboard. Adverse events were closely monitored during surgery and the postoperative period, including surgical emphysema and pneumothorax.

Table 1.

The five-point rating scale used to assess the surgical conditions during intracorporeal suturing[8]

Scale	Description
Extremely poor conditions	Unable to complete surgery without interventionsa
Poor conditions	Several minor adjustments needed to complete surgery (i.e., changes in patient positioning and surgeons position)
Acceptable conditions	After few minor adjustments, surgery can be completed
Good conditions	Surgical overview is good; there is some interference, but no need for adjustments
Optimal conditions	Surgical overview is optimal and the procedure can be completed without any interference

^aInterventions are defined as change in depth of neuromuscular blockade and/or increased pneumoperitoneum

Statistical analysis

The categorical variables were presented in the form of numbers and percentages (%). On the other hand, the quantitative data were presented as the means ± standard deviation and as a median with 25^th and 75^th percentiles (interquartile range). The data normality was checked using the Kolmogorov–Smirnov test. In the cases in which the data were not normal, we used nonparametric tests. The comparison of the variables that were quantitative and not normally distributed in nature was analyzed using the Mann–Whitney test, and variables that were quantitative and normally distributed in nature were analyzed using the independent t-test. Paired t-test was used for the comparison of normally distributed data across follow-up, and the Wilcoxon signed-rank test was used for the comparison of nonnormally distributed data across follow-up. The comparison of the variables, which were qualitative in nature, was analyzed using the Chi-square test. If any cell had an expected value of <5, Fisher’s exact test was used. The data entry was done in the Microsoft Excel spreadsheet, and the final analysis was done using the Statistical Package for the Social Sciences (SPSS) software, IBM manufacturer, Chicago, IL, USA, Version 25.0. For statistical significance, P < 0.05 was considered statistically significant.

RESULTS

Demographic characteristics were comparable in both groups having 24 patients each, as shown in Table 2. There was a significant difference in PaCO₂ values between Group I and Group II at T1 (43.42 ± 4.19 vs. 46.45 ± 2.18; P < 0.005), T2 (38.52 ± 2.44 vs. 40.17 ± 2.52; P < 0.05), and T3 (36.28 ± 2.71 vs. 37.9 ± 1.41; P < 0.05), respectively. There was a significant difference in the EtCO₂ at the T1 time point (41.08 ± 3.3 vs. 44.38 ± 2.37; P < 0.005). The number of times ventilatory settings was changed in Group II was 7.12 ± 1.7, which was significantly higher as compared to Group I (4.42 ± 1.79) (P < 0.0001) [Table 3].

Table 2.

Demographic characteristics

Variables	Mean±SD		P
	Group I	Group II
Age (years)	2.69±1.5	3.0±1.41	0.285
Sex (male:female)	15:09	13:11	0.558
Height (cm)	92.04±22.62	98.83±20.06	0.277
Weight (kg)	12.34±4.72	14.75±6.39	0.144

SD: Standard deviation

Table 3.

Comparison of intraoperative ventilatory parameters between Group I and Group II

Variables	Mean±SD		P
	Group I	Group II
PaCO2 T0	37.4±3.37	36.43±2.85	0.285
PaCO2 T1	43.42±4.19	46.45±2.18	0.003
PaCO2 T2	38.52±2.44	40.17±2.52	0.026
PaCO2 T3	36.28±2.71	37.90±1.41	0.013
EtCO2 T0	35.58±2.9	34.21±2.54	0.087
EtCO2 T1	41.08±3.33	44.38±2.37	0.0003
EtCO2 T2	36.67±2.3	37.79±2.3	0.097
EtCO2 T3	34.96±2.69	35.54±1.38	0.35
pH T0	7.38±0.04	7.38±0.03	0.555
pH T1	7.31±0.04	7.30±0.03	0.91
pH T2	7.36±0.04	7.34±0.02	0.054
pH T3	7.38±0.03	7.36±0.02	0.076
Number of times ventilatory settings were changed	4.42±1.79	7.12±1.7	<0.0001

PaCO₂: Partial pressure of CO₂, EtCO₂: End-tidal CO₂

There were no significant differences in the hemodynamic parameters such as HR and mean blood pressure. HR at T0, T1, T2, and T3 between Group I and II was 124.42 ± 12.77 versus 121.79 ± 17.43 (P = 0.441), 129.42 ± 15.63 versus 126.92 ± 14.42 (P = 0.567), 128.54 ± 15.84 versus 123.88 ± 13.1 (P = 0.272), and 129.04 ± 15.79 versus 121.58 ± 14.14 (P = 0.091), respectively, which was statistically insignificant at all time points. MAP at T0, T1, T2, and T3 between Group I and II was 66.75 ± 8.95 versus 64.5 ± 7.7 (P = 0.355), 70.88 ± 7.01 versus 68.5 ± 7.02 (P = 0.247), 69.88 ± 7.46 versus 69.29 ± 7.89 (P = 0.794), and 68.88 ± 6.28 versus 65.17 ± 9.12 (P = 0.108), respectively, which was statistically insignificant at all time points. As shown in Table 4, there was no difference in the five-point rating scale used to measure the ease at which the operating surgeon was able to perform surgery with P = 0.234. As shown in Table 5, postoperative pain was significantly lower in Group I at 1 h (2.58 ± 1.44 vs. 3.29 ± 2.21, P < 0.05), 6 h (3.62 ± 1.41 vs. 4.50 ± 1.47; P < 0.02), and 12 h (1.33 ± 1.55 vs. 2.62 ± 1.28; P < 0.05) after surgery and required a higher number of doses of rescue analgesia in Group II (3.38 ± 1.79 vs. 4.58 ± 2.21; P < 0.05). The time to resumption of feeding was similar in both groups and they witnessed an uneventful surgery with no complications in all the cases.

Table 4.

Comparison of surgeon’s five-point rating scale between Groups I and II

Surgeon’s rating	Group I (n=24), n (%)	Group II (n=24), n (%)	Total	P
Poor conditions	1 (4.17)	0	1 (2.08)	0.234*
Good conditions	2 (8.33)	0	2 (4.17)
Optimal conditions	21 (87.50)	24 (100)	45 (93.75)
Total	24 (100)	24 (100)	48 (100)

Table 5.

Comparison of postoperative parameters between the two groups

Variables	Mean±SD		P
	Group I	Group II
Pain at 1st postoperative hour	2.58±1.44	3.29±2.21	0.048
Pain at 6th postoperative hour	3.62±1.41	4.5±1.47	0.022
Pain at 12th postoperative hour	1.33±1.55	2.62±1.28	0.006
Number of doses of rescue analgesia	3.38±1.79	4.58±2.21	0.048
Time of resumption of feeding (h)	52.17±28.06	49.58±27.59	0.749

SD: Standard deviation

DISCUSSION

Laparoscopy is gradually replacing open abdominal surgery as it has several advantages, even in children. In particular, laparoscopy is associated with better cosmetic results, shorter hospital stay, lower postoperative pain, and a faster return to daily activities.[9,10]

Pneumoperitoneum is essential for laparoscopic surgery, but it affects abdominal cavity homeostasis and may result in metabolic changes through mechanical and biochemical effects.[11,12,13,14] Due to the lesser physiological reserve, the margin of error is considerably less in the pediatric population. Laparoscopic surgeries can be associated with clinical complications, including gas embolism, barotraumas, hypertension, hypotension, arrhythmias, cardiovascular compromise, deep venous thrombosis, subcutaneous emphysema, hypoxemia, and hypercapnia in children.

The range of PP for laparoscopy usually varies from 5 to 12 mmHg in infants and children, but the physiological response to PP in children remains an issue of debate.[4] Normal intra-abdominal pressure (IAP) should be 5–7 mmHg in children. For laparoscopic procedures, IAP levels within 8–12 mmHg are acceptable for children older than 1 year.[15] Moreover, an IAP level of 12 mmHg has been reported to be associated with decreased cardiac index and hypokinesia of the left ventricle in children. The duration of surgery and the position of patients could also lead to pathophysiological changes in children.[16,17] As we know, a higher IAP could contribute to better visualization of the anatomical structures and better manipulation of instruments. However, it could also lead to many pathophysiological changes such as respiratory and cardiovascular compromise. Thus, we need to strike a balance between the technical ease for the surgeon in terms of adequate working space and at the same time having safe and physiologically optimal PPs for children during laparoscopic surgery. The present study was conducted to determine the optimal and safe PPs in children aged 1–5 years as well as the technical ease for the surgeon in performing various pediatric laparoscopic surgeries. We added the novel element of the surgeon’s five-point rating scale to assess the ease of operability in terms of adequacy of working space which has been used by the author (AM) in the previous studies.[8]

In our study, PaCO₂ was significantly higher in Group II (PP of 9–10 mmHg) at 20 min after insufflation, just before desufflation, and also at 10 min after desufflation when compared with Group I (PP = 6–8 mmHg). EtCO₂ was significantly higher (P = 0.0003) in Group II (PP of 9–10 mmHg) at 20 min after insufflation. The number of times the ventilatory settings had to be changed was significantly higher (P < 0.0001) in Group II (PP of 9–10 mmHg) when compared with Group I (PP = 6–8 mmHg). Postoperative pain scores were significantly higher at 1, 6, and 12 h after surgery in Group II as compared to Group I, requiring a higher number of doses of rescue analgesia. There was no significant difference between the time of resumption of feeding (hours) between the two groups.

In a similar study done by Sureka SK et al. in 46 infants undergoing laparoscopic renal surgeries, their hemodynamic, respiratory, and blood gas changes were measured at four different time points: before CO₂ insufflation (T0), 10 min after insufflation (T1), before desufflation (T2), and 10 min after desufflation (T3).[3] The hemodynamic and respiratory changes were more pronounced with higher PP (PP = 9–10 mmHg) in infants for laparoscopic renal surgery. With a PP of 6–8 mmHg, intraoperative accessibility is optimal, and physiological changes are minimal. Interestingly, they found that infants with PP of 6–8 mmHg enjoy smooth and early postoperative recovery.[3] Their results are similar to our results. They assessed surgeons’ comfort with a simple yes or no, but we in our study, used a novel five-point rating scale for the surgeon to assess the ease at which the operation was performed.

Halachmi et al. retrospectively analyzed records of 73 patients who underwent laparoscopic urological surgery for RR, peak airway pressure (PAP), O₂ saturation, EtCO₂, HR, systolic and diastolic blood pressure (DBP), electrocardiogram, and insufflation pressure. All variables were recorded before and after CO₂ insufflation. Significant increase in EtCO₂, RR, and PAP was recorded after CO₂ insufflation in the extraperitoneal group, which is similar to our results.[18]

A retrospective data analysis was performed by Hou X et al.[19] on 1776 children aged 0.9–12 years needing laparoscopic high ligation of hernia sac. They recorded systolic blood pressure (SBP), DBP, stroke volume, and arterial PaCO₂ every 10 min from baseline T0 (5 min before insufflation), T1 (5 min after insufflation), T2 (15 min after insufflation), and T3 (end of insufflation). They found that, compared to 5 min before insufflation, the blood pressures of patients (SBP and DBP) and the PaCO₂ increased after CO₂ insufflation after 5, 15, and end of insufflation during the surgery (P < 0.05). Most of them had been statistically significantly elevated from the baseline measured value. We also had PaCO₂ values higher in Group II patients at 10 min, 20 min after insufflation and before desufflation and 10 min after desufflation.

Ho et al. reported that peritoneal insufflation of CO₂ leads to hypercarbia as a result of transperitoneal absorption of CO₂ using a porcine model.[20] Hypercarbia, in turn, leads to an increase in HR and blood pressure mediated by the sympathetic nervous system. However, in our study, there was no significant difference between HR and MAP between the two groups.

To summarize, there was a significant decrease in PaCO₂ and EtCO₂ values in the pediatric patients aged 1–5 years when insufflated with 6–8 mmHg PP as compared to patients insufflated with 9–10 mmHg PP at different time points, but these values though statistically significant were not clinically significant. The surgeon’s ease of performing surgery was similar in both groups. Although contemporary literature and previous studies suggest that there are significant hemodynamic and ventilatory benefits of using lower PP pressures, our study did not find any clinically significant benefit although there was a statistically significant difference in using lower PP pressures in our patients.

CONCLUSIONS

Higher PP in Group II caused significant changes in PaCO₂, EtCO₂, and postoperative pain requiring rescue analgesia, but blood gas changes were clinically insignificant and there were no significant changes in hemodynamic parameters. Since the surgeon’s ease of performing surgery was similar in both groups, we recommend that laparoscopy in children aged 1–5 years can be started with lower PPs of 6–8 mmHg, which can be increased if needed based on the surgeon’s comfort and the patient’s body habitus.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.