Abstract
Background: Laparoscopic bariatric surgery has become a regular procedure, and it has largely replaced traditional open surgery. Patients experience postoperative pain even after laparoscopic surgery, although the intensity is low compared to open surgery. We compared the effectiveness of intravenous (IV) vs. intraperitoneal (IP) magnesium sulphate (MgSO4) injection in pain management in laparoscopic mini-gastric bypass surgery.
Methodology: We selected 100 patients based on convenient sampling and randomly divided into two groups; the IV group (50 patients) received MgSO4 50 mg/kg in 250 ml normal intravenously, and the IP group (50 patients) received MgSO4 50 mg/kg in 30 ml normal saline intraperitoneally. Nalbuphine was used as rescue analgesic and its total postoperative consumption during the first 24 h was recorded based on VAS score. Postoperative nausea and vomiting (PONV), sedation score and hemodynamic changes with pneumoperitoneum were also assessed.
Results: Total nalbuphine consumption postoperatively was more in IV group than IP group (12 ± 3.03 mg vs. 8.3 ± 2.8 mg; P < 0.001). Postoperative pain score was significantly lower in IP group in comparison to IV group (P < 0.001). Intraoperative hypotension and bradycardia were significantly more (P = 0.03) in IV group (21% and 17% respectively) compared to IP group (10% and 7% respectively). Postoperative sedation and nausea and vomiting scores were reduced in IP group compared to IV group, the difference being highly significant (P < 0.001).
Conclusion: Intraperitoneal MgSO4 instillation has better results than intravenous infusion in attenuation of postoperative pain and hemodynamic response associated with pneumoperitoneum, and results in less PONV when used in laparoscopic minigastric bypass patients.
Key words: Analgesics / administration & dosage; Analgesics / pharmacology; Analgesics / therapeutic use; Bariatric; Magnesium Sulfate / administration & dosage; Magnesium Sulfate / pharmacokinetics; Magnesium Sulfate / therapeutic use; Mini-gastric bypass; Pain management; Pneumoperitoneum
Citation: El-Sesy MG, Abdel Hameed AE, Abdelaziz AA, Ahmed IM, Elhennawy AM. A comparative study between intravenous and intraperitoneal magnesium sulphate for pain management in laparoscopic mini gastric bypass: a randomized clinical trial. Anaesth. pain intensive care 2022;26(4):450-457; DOI: 10.35975/apic.v26i4.1947
Received: April 18, 2022; Reviewed: June 16, 2022; Accepted: July 10, 2022
Introduction
Obesity is a global and rapidly rising condition with a serious impact on all aspects of healthcare especially perioperative care. The frequency of bariatric surgeries has been escalating worldwide for medically confounded obesity patients, who are unable to lose weight by various strategies.1
Laparoscopic surgery is made possible by instillation of inert gas in the peritoneum under pressure, creating pneumoperitoneum. This condition has been found to cause a rise in systemic vascular resistance that is mostly due to the effects of the released vasopressin and catecholamines. Magnesium sulphate (MgSO4) suppresses the secretion of catecholamines from the adrenal medulla in as well as from adrenergic nerve endings. A significant vasodilator action on blood vessels was observed resulting in a decrease in blood pressure. MgSO4 is also able to weaken vasopressin–mediated vasoconstriction.2
Intraperitoneal instillation of MgSO4 might lessen the hemodynamic stress reaction resulting from pneumoperitoneum besides enhancing patient’s satisfaction by decreasing postoperative pain. Among multiple actions of Mg, the blockage of calcium channels and N-methyl-D-aspartate (NMDA) receptors has a significant importance to anesthesia. MgSO4 has been observed to have a good effect in pain management besides inhibiting somatic, autonomic and endocrinal responses motivated by painful stimulus.3
We compared the outcome of early intraperitoneal instillation of MgSO4 before any dissection on hemodynamic response and its analgesic effect vs. administration of IV MgSO4 in laparoscopic mini-gastric bypass surgery patients.
Methodology
This randomized prospective comparative study was conducted from December 2020 to December 2021 at Ain Shams University Hospitals. We enrolled 100 obese patients, ages between 21-60 y, BMI 35–59.9 Kg/m2, both genders, ASA (II and III) undergoing elective laparoscopic mini-gastric bypass surgery.
The exclusion criteria were; patient refusal, pregnant or breast-feeding women, ASA > III, the need to convert laparoscopic surgery to an open one, allergy to MgSO4, 1st or 2nd degree heart block, chronic treatment by beta-blockers, heart rate < 50 bpm, heart failure with LVEF < 40%, severe chronic disease, severe obstructive sleep apnea (OSA), history of chronic pain, alcohol or drug abuse and psychiatric illness.
All candidates provided written informed consent, and were randomized to one of the two groups through a computer randomization software.
The intravenous (IV) group included 50 patients who were given MgSO4 50 mg/kg in 250 ml of normal saline. The intraperitoneal (IP) group included 50 patients who were given MgSO4 50 mg/kg in 30 ml of normal saline intraperitoneally before insufflation of CO2.
Medical and surgical history, physical examination, including appropriate evaluation of the airway and investigations, including complete blood count (CBC), coagulation profile, kidney and liver functions tests, and electrocardiography (ECG), echocardiography and pulmonary function tests (for patients with BMI > 40), were done in anesthesia clinic. The plan was discussed with the patients and the visual analogue scale was explained to them to describe pain perception post- surgical procedure.
At OR, an 18G IV cannula was inserted. Basic monitoring was started. All patients received famotidine (H2-blocker) 50 mg, metoclopramide 10 mg and dexamethasone 4 mg IV for prophylaxis from nausea and vomiting.
Inj. midazolam 2 mg was given for sedation. Pre-oxygenation with 100% was done. GA was induced with fentanyl 1 µg/kg, propofol 1.5-2 mg/kg, and muscle relaxation by atracurium (started by 0.5 mg/Kg) later on (0.1 mg/kg) boluses as a maintenance doses. After that, Endotracheal tube (ETT) of proper size was introduced to protect airway. Anesthesia was maintained by isoflurane (1.2% mean alveolar concentration MAC) within 50/50 of oxygen and air mix, and the MAC was modified according to patient’s hemodynamics, and Fentanyl was infused IV in the rate of 1 µg /kg/h in 50 ml syringe throughout the whole procedure started prior to skin incision. Controlled ventilation in the form of intermittent positive pressure ventilation (IPPV) started; settings were accustomed to preserve end tidal CO2 level (EtCO2) within 35-45 mmHg.
A reference number was distinguished the MgSO4 syringes, which were all identically labelled. This ensured the safety of the patients as well as the blinding of all participants, including anesthetic personnel.
Patients in Group IV received MgSO4 50 mg/kg in 250 ml normal saline intravenously. Then received 30 ml normal saline intraperitoneally before insufflation of CO2. Patients of Group IP received 250 ml normal saline intravenously. Then received MgSO4 50 mg/kg in 30 ml of normal saline intraperitoneally before insufflation of CO2.
Fentanyl infusion was withdrawn after skin closure. Inj. paracetamol 1 G and inj. diclofenac 75 mg were
administrated intra-operatively to all patients. Inj. neostigmine 0.05 mg/kg and atropine 0.01 mg/kg was administrated at the end of the procedure to reverse the residual muscle relaxation. Awake extubation was done after oral suctioning.
Patients were transported to post anesthesia care unit (PACU) after being fully recovered.
Analgesia was maintained by inj. paracetamol 1 G IV every 6 h over subsequent 24 h, besides rescue analgesic nalbuphine 50 µg/kg, if visual analogue score (VAS) score was more than 3.
The primary outcome of our study was total nalbuphine consumption during the first 24 h postoperatively based on VAS score. The VAS was measured 30 min after recovery, and at 2 h, 4 h, 6 h, 12 h and 24 h postoperatively.
Secondary outcomes were; frequency of PONV in the first 24 h after extubation. Nausea was assessed at the same as of VAS via a scoring system (0 = none, 1 = mild, 2 = moderate, 3 = severe). Patients suffering from vomiting or who rated their nausea at level 2 or more were given inj. ondansetron 4 mg IV.
Sedation was also assessed at the same intervals of VAS by a scale (0 = alert, 1 = quietly awake, 2 = asleep but easily aroused and 3 =deep sleep).
Hemodynamic parameters; mean arterial blood pressure (MAP) and heart rate (HR) were recorded prior to induction of anesthesia as a baseline reading (Tb), immediately after intubation (Ti), before pneumoperitoneum (P0), then every 10 min till 30 min (P10, P20, and P30) and after extubation (Tex). Also, incidents of bradycardia, hypotension and hypertension were recorded. Bradycardia was described as: HR ≤ 50 bpm. Hypotension was described as a decline in systolic blood pressure less than 20% of the baseline value. Hypertension is described as a rise in systolic blood pressure more than 20% of the baseline value.
Intraoperative hypotension was managed by ephedrine 5–10 mg IV bolus, then titrated as needed. hypertension was handled by increasing isoflurane MAC to 2 or 3%, or a bolus of fentanyl 25 µg IV, then nitroglycerin infusion 1 µg /kg/min was added if still needed. Bradycardia was handled by a bolus of atropine 0.01 mg/kg, repeated as required.
Statistical Analysis
PASS11 program was used for sample size calculation, setting alpha error at 5%. Elfiky M. and his colleagues (2018), showed that the total analgesic requirement during the first postoperative 24 h was (2.34 ± 1.08) for IV group versus (1.26 ± 0.78) for IP group. Based on these findings, a sample size of 50 patients per group
would reach 100% power for detecting the difference in the pain level between the two groups.
Data were analyzed using Statistical package for Social Science (SPSS) version 22.0. Mean ± standard deviation
(SD) were used for quantitative data. Frequency and percentage were used for qualitative data.
Independent-samples t-test of significance was utilized for two means comparison. Chi-square (X2) test of significance was utilized for proportions comparison between two qualitative parameters. Mann Whitney U test compared two-groups in non-parametric data. The confidence interval was set to 95% and the margin of error accepted was set to 5%. P ≤ 0.05 was considered significant.
Results
One hundred patients were enrolled, 50 patients in each group. The two groups were comparable in demographic data (in terms of age, sex, BMI and ASA) and duration of surgery and there were no statistically significant difference between groups (P > 0.05) (Table 1).
IV group was lesser than IP group as regard MABP, and a significant difference was observed before pneumoperitoneum, 10 min, 20 min, 30 min after pneumoperitoneum and after extubation (P = 0.03, 0.03, 0.047, 0.003 and 0.002 respectively) (Figure 1).
Regarding HR, a significant difference was observed before pneumoperitoneum, and at 10 min, 20 min and 30 min after pneumoperitoneum (P = 0.048, 0.006, 0.021, and 0.007) respectively, HR change was small in the IV group as compared to IP group (Figure 2).
Regarding HR, a significant difference was observed before pneumoperitoneum, and at 10 min, 20 min and 30 min after pneumoperitoneum (P = 0.048, 0.006, 0.021, and 0.007) respectively, HR change was small in the IV group as compared to IP group (Figure 2).
IV group demonstrated significantly more hypotension and bradycardia episodes (P =
0.03 and P = 0.035) respectively. Although IV group showed less hypertension episodes. but the difference was statistical not significant (Table 2).
The IP group demonstrated lower pain scores than IV group, with significant differences at 30 min, 2 h, 4 h and 6 h after surgery (P < 0.05). The total postoperative nalbuphine consumption was more in the IV group (12 ± 3.03) than IP group (8.3 ± 2.8) (Table 3).
The IP group showed less PONV with significant difference at 30 min, 2 h, 4 h and 6 h postoperatively (P < 0.05). Otherwise there was no statistical difference between two groups (Table 4).
The IP group showed less sedation than the IV group with significant difference at 30 min and 2 h postoperatively. Otherwise there was no statistical difference between two group (Table 5).
Discussion
Magnesium is considered the second most frequent intra-cellular cation with a chief function to preserve homeostasis. Magnesium is an essential factor for cell signaling, the normal function of enzymes and neurotransmission. Studies show that magnesium has an antagonist effect on NMDA receptors, which could affect pain sensitivity and extent.5 The usage of magnesium for perioperative analgesia was
initially studied by Koinig et al. in candidates with similar degrees of surgical stimuli.6
Pre-emptive analgesia has been a popular practice among anesthetists and its role in the pain management has been widely discussed. It is aimed to avoid CNS sensitization to following stimuli that intensify pain signals.7 Postoperative pain perception has a harmful impact on recovery, hemodynamics, respiration, ambulation, and it prolongs the hospital stay. Unfortunately, it is known that opioid-based analgesia in obese patients is accompanied with critical side effects like apnea, hypoxemia, sleepiness, ileus, delayed ambulation, and so increased mortality rates.1 Although MgSO4 causes mild sedation, it decreases anesthetic needs; this is useful in decreasing residual anesthetic effects in bariatric patients, decreasing risk of postoperative apnea.2
In our study, MABP and HR there were significantly lower in IV group before pneumoperitoneum, 10 min, 20 min, 30 min after pneumoperitoneum and after extubation (Figure 1 and 2). IV group had more frequency of hypotension and bradycardia. We found that attenuation of the hemodynamic changes associated with pneumoperitoneum was better with IV group than IP group. IP group was better in events of bradycardia and hypotension than IV group. This might be due to rapid rise in magnesium levels and ithus onset of action with IV administration.
Our results were similar to those reported by El Mourad and Arafa about the benefits of IV and IP intake of MgSO4 in attenuating the hemodynamic alterations created due to pneumoperitoneum.2 Paul et al. demonstrated a significant decline in HR and MAP throughout pneumoperitoneum for laparoscopic cholecystectomy after administration of 30 mg/kg MgSO4 IV.8 Ali et al. instilled 20 ml MgSO4 10% IP following pneumoperitoneum in laparoscopic cholecystectomy and reported a reduction of unwanted hemodynamic changes in comparison to the controls.9 The IP intake of local anesthetics with or without adjuvant was reported to be efficient in enhancing perception of pain during different laparoscopic surgeries. This might be caused by blockage of visceral afferent pain transmission. Furthermore, absorption from the huge surface like peritoneum might also add to analgesia.2
In our study, the IP group patients expressed less pain perception, and less postoperative nalbuphine utilization than the IV group. Magnesium affects the influx of calcium into the cells and moreover antagonizes NMDA receptors, which affect neuronal signaling and pain processing in the central nervous system. By these receptors blockage, it causes blockage of both somatic and visceral pain fibers and so decreases postoperative pain.10 Similar results in patients undergoing laparoscopic cholecystectomy were shown by other researchers.1,2,5,11,12
A systematic review by Lysakowski et al. did not identify a significant systemic impact of MgSO4 on pain management postoperatively. That might be explained by less clinical trials in addition to fewer participants (n = 778) in comparison with meta-analysis reported by De Oliveira et al. Besides, Lysakowski et al. assessed patients undergoing dissimilar modes of anesthesia, including neuraxial blocks, while De Oliveira et al. limited their study to patients, who underwent operations under general anesthesia.5,13
In our study, the IP group showed less PONV with significant difference at 30 min, 2h, 4h and 6h postoperatively. Similar results were reported by El Mourad and Arafa.2 They explained that by the anesthetic / analgesic sparing actions of MgSO4 had led to reduced frequency of PONV; another clarification was the NMDA antagonist action of MgSO4 on receptors situated in the common pathway of nausea and vomiting. Nevertheless, there is no current information available on the direct effect of MgSO4 on PONV.2,9 On the other side, Kizilcik et al. reported that the prevalence of unfavorable side effects like PONV in addition to shivering was almost similar between the patients, who received IV MgSO4 and control group although morphine consumption was reduced.1
In our study, the IP group showed less sedation with significant difference at 30 min and 2 h postoperatively. In accordance to our results, Elfiky et al. reported that patients receiving IV magnesium needed more time to achieve an Alderete score of 9 to be fit for discharge from PACU; and had higher sedation score in the first 2 h postoperatively than IP group.11 Ali et al. also reported that sedation score was significantly higher in patients receiving IV MgSO4 in comparison with controls during the first 3 h postoperatively.9
The timing of instillation of local anesthetic and adjuvant through the procedure is still debatable. Barczynski et al. recommended early instillation of intraperitoneal local anesthetics before creation of pneumoperitoneum to provide better hemodynamic response and postoperative pain management in comparison with infusion within the closing stages of the procedure. More studies are required to establish the ideal time and the route of administration of MgSO4 for laparoscopic procedures.
Conclusions
Intraperitoneal instillation of MgSO4 is a safe technique that has better results than intravenous infusion in attenuation of hemodynamic response with pneumoperitoneum, and offers reduced postoperative pain and PONV with laparoscopic mini gastric bypass patients.
Limitations
It is not obvious whether magnesium has to be administrated along with the actual or ideal bodyweight in obese patients due to the inadequate information on the usage of MgSO4 in bariatric candidates. We calculated MgSO4 dosage using actual body weight as was done in several earlier studies. Moreover, the timing of the instillation of the local anesthetic and adjuvants remains to be deduced with clear criteria.
Ethics approval and consent to participate
This study was approved by the research ethics committee at the faculty of medicine, Ain Shams University (FMASU M D 235/2020) and registered with Pan African Clinical Trial Registry, identifier: PACTR202111620456298. Written informed consent was obtained from all patients.
Availability of data
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Competing interests
The authors declare no conflicts of interest.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors.
References
Background: Laparoscopic bariatric surgery has become a regular procedure, and it has largely replaced traditional open surgery. Patients experience postoperative pain even after laparoscopic surgery, although the intensity is low compared to open surgery. We compared the effectiveness of intravenous (IV) vs. intraperitoneal (IP) magnesium sulphate (MgSO4) injection in pain management in laparoscopic mini-gastric bypass surgery.
Methodology: We selected 100 patients based on convenient sampling and randomly divided into two groups; the IV group (50 patients) received MgSO4 50 mg/kg in 250 ml normal intravenously, and the IP group (50 patients) received MgSO4 50 mg/kg in 30 ml normal saline intraperitoneally. Nalbuphine was used as rescue analgesic and its total postoperative consumption during the first 24 h was recorded based on VAS score. Postoperative nausea and vomiting (PONV), sedation score and hemodynamic changes with pneumoperitoneum were also assessed.
Results: Total nalbuphine consumption postoperatively was more in IV group than IP group (12 ± 3.03 mg vs. 8.3 ± 2.8 mg; P < 0.001). Postoperative pain score was significantly lower in IP group in comparison to IV group (P < 0.001). Intraoperative hypotension and bradycardia were significantly more (P = 0.03) in IV group (21% and 17% respectively) compared to IP group (10% and 7% respectively). Postoperative sedation and nausea and vomiting scores were reduced in IP group compared to IV group, the difference being highly significant (P < 0.001).
Conclusion: Intraperitoneal MgSO4 instillation has better results than intravenous infusion in attenuation of postoperative pain and hemodynamic response associated with pneumoperitoneum, and results in less PONV when used in laparoscopic minigastric bypass patients.
Key words: Analgesics / administration & dosage; Analgesics / pharmacology; Analgesics / therapeutic use; Bariatric; Magnesium Sulfate / administration & dosage; Magnesium Sulfate / pharmacokinetics; Magnesium Sulfate / therapeutic use; Mini-gastric bypass; Pain management; Pneumoperitoneum
Citation: El-Sesy MG, Abdel Hameed AE, Abdelaziz AA, Ahmed IM, Elhennawy AM. A comparative study between intravenous and intraperitoneal magnesium sulphate for pain management in laparoscopic mini gastric bypass: a randomized clinical trial. Anaesth. pain intensive care 2022;26(4):450-457; DOI: 10.35975/apic.v26i4.1947
Received: April 18, 2022; Reviewed: June 16, 2022; Accepted: July 10, 2022
Introduction
Obesity is a global and rapidly rising condition with a serious impact on all aspects of healthcare especially perioperative care. The frequency of bariatric surgeries has been escalating worldwide for medically confounded obesity patients, who are unable to lose weight by various strategies.1
Laparoscopic surgery is made possible by instillation of inert gas in the peritoneum under pressure, creating pneumoperitoneum. This condition has been found to cause a rise in systemic vascular resistance that is mostly due to the effects of the released vasopressin and catecholamines. Magnesium sulphate (MgSO4) suppresses the secretion of catecholamines from the adrenal medulla in as well as from adrenergic nerve endings. A significant vasodilator action on blood vessels was observed resulting in a decrease in blood pressure. MgSO4 is also able to weaken vasopressin–mediated vasoconstriction.2
Intraperitoneal instillation of MgSO4 might lessen the hemodynamic stress reaction resulting from pneumoperitoneum besides enhancing patient’s satisfaction by decreasing postoperative pain. Among multiple actions of Mg, the blockage of calcium channels and N-methyl-D-aspartate (NMDA) receptors has a significant importance to anesthesia. MgSO4 has been observed to have a good effect in pain management besides inhibiting somatic, autonomic and endocrinal responses motivated by painful stimulus.3
We compared the outcome of early intraperitoneal instillation of MgSO4 before any dissection on hemodynamic response and its analgesic effect vs. administration of IV MgSO4 in laparoscopic mini-gastric bypass surgery patients.
Methodology
This randomized prospective comparative study was conducted from December 2020 to December 2021 at Ain Shams University Hospitals. We enrolled 100 obese patients, ages between 21-60 y, BMI 35–59.9 Kg/m2, both genders, ASA (II and III) undergoing elective laparoscopic mini-gastric bypass surgery.
The exclusion criteria were; patient refusal, pregnant or breast-feeding women, ASA > III, the need to convert laparoscopic surgery to an open one, allergy to MgSO4, 1st or 2nd degree heart block, chronic treatment by beta-blockers, heart rate < 50 bpm, heart failure with LVEF < 40%, severe chronic disease, severe obstructive sleep apnea (OSA), history of chronic pain, alcohol or drug abuse and psychiatric illness.
All candidates provided written informed consent, and were randomized to one of the two groups through a computer randomization software.
The intravenous (IV) group included 50 patients who were given MgSO4 50 mg/kg in 250 ml of normal saline. The intraperitoneal (IP) group included 50 patients who were given MgSO4 50 mg/kg in 30 ml of normal saline intraperitoneally before insufflation of CO2.
Medical and surgical history, physical examination, including appropriate evaluation of the airway and investigations, including complete blood count (CBC), coagulation profile, kidney and liver functions tests, and electrocardiography (ECG), echocardiography and pulmonary function tests (for patients with BMI > 40), were done in anesthesia clinic. The plan was discussed with the patients and the visual analogue scale was explained to them to describe pain perception post- surgical procedure.
At OR, an 18G IV cannula was inserted. Basic monitoring was started. All patients received famotidine (H2-blocker) 50 mg, metoclopramide 10 mg and dexamethasone 4 mg IV for prophylaxis from nausea and vomiting.
Inj. midazolam 2 mg was given for sedation. Pre-oxygenation with 100% was done. GA was induced with fentanyl 1 µg/kg, propofol 1.5-2 mg/kg, and muscle relaxation by atracurium (started by 0.5 mg/Kg) later on (0.1 mg/kg) boluses as a maintenance doses. After that, Endotracheal tube (ETT) of proper size was introduced to protect airway. Anesthesia was maintained by isoflurane (1.2% mean alveolar concentration MAC) within 50/50 of oxygen and air mix, and the MAC was modified according to patient’s hemodynamics, and Fentanyl was infused IV in the rate of 1 µg /kg/h in 50 ml syringe throughout the whole procedure started prior to skin incision. Controlled ventilation in the form of intermittent positive pressure ventilation (IPPV) started; settings were accustomed to preserve end tidal CO2 level (EtCO2) within 35-45 mmHg.
A reference number was distinguished the MgSO4 syringes, which were all identically labelled. This ensured the safety of the patients as well as the blinding of all participants, including anesthetic personnel.
Patients in Group IV received MgSO4 50 mg/kg in 250 ml normal saline intravenously. Then received 30 ml normal saline intraperitoneally before insufflation of CO2. Patients of Group IP received 250 ml normal saline intravenously. Then received MgSO4 50 mg/kg in 30 ml of normal saline intraperitoneally before insufflation of CO2.
Fentanyl infusion was withdrawn after skin closure. Inj. paracetamol 1 G and inj. diclofenac 75 mg were
| Table 1: Comparative demographic data and duration of surgery | ||||
| IV group
(n=50) |
IP group
(n=50) |
T/Z/x2 | p-value | |
| Age (years)* | 44.9 ± 4.3 | 44.5 ± 4.2 | 0.5t | 0.6 |
| BMI (Kg/m2)* | 43.42 ± 3 | 42.98 ± 2.5 | 0.79t | 0.43 |
| ASA** | 3 (2-3) | 3 (2-3) | 0.2z | 0.84 |
| Sex (Males)*** | 27 (54%) | 24 (48%) | 0.16x2 | 0.69 |
| Duration of surgery* | 84.2 ± 7.6 | 83.8 ± 6.97 | 0.28 t | 0.78 |
| Data defined as *mean ± SD, **median (IQR), ***proportion.
t = student t test, Z= Mann-Whitney test, x2= Chi square |
||||
administrated intra-operatively to all patients. Inj. neostigmine 0.05 mg/kg and atropine 0.01 mg/kg was administrated at the end of the procedure to reverse the residual muscle relaxation. Awake extubation was done after oral suctioning.
Patients were transported to post anesthesia care unit (PACU) after being fully recovered.
Analgesia was maintained by inj. paracetamol 1 G IV every 6 h over subsequent 24 h, besides rescue analgesic nalbuphine 50 µg/kg, if visual analogue score (VAS) score was more than 3.
The primary outcome of our study was total nalbuphine consumption during the first 24 h postoperatively based on VAS score. The VAS was measured 30 min after recovery, and at 2 h, 4 h, 6 h, 12 h and 24 h postoperatively.
Secondary outcomes were; frequency of PONV in the first 24 h after extubation. Nausea was assessed at the same as of VAS via a scoring system (0 = none, 1 = mild, 2 = moderate, 3 = severe). Patients suffering from vomiting or who rated their nausea at level 2 or more were given inj. ondansetron 4 mg IV.
Sedation was also assessed at the same intervals of VAS by a scale (0 = alert, 1 = quietly awake, 2 = asleep but easily aroused and 3 =deep sleep).
Hemodynamic parameters; mean arterial blood pressure (MAP) and heart rate (HR) were recorded prior to induction of anesthesia as a baseline reading (Tb), immediately after intubation (Ti), before pneumoperitoneum (P0), then every 10 min till 30 min (P10, P20, and P30) and after extubation (Tex). Also, incidents of bradycardia, hypotension and hypertension were recorded. Bradycardia was described as: HR ≤ 50 bpm. Hypotension was described as a decline in systolic blood pressure less than 20% of the baseline value. Hypertension is described as a rise in systolic blood pressure more than 20% of the baseline value.
Intraoperative hypotension was managed by ephedrine 5–10 mg IV bolus, then titrated as needed. hypertension was handled by increasing isoflurane MAC to 2 or 3%, or a bolus of fentanyl 25 µg IV, then nitroglycerin infusion 1 µg /kg/min was added if still needed. Bradycardia was handled by a bolus of atropine 0.01 mg/kg, repeated as required.
Statistical Analysis
PASS11 program was used for sample size calculation, setting alpha error at 5%. Elfiky M. and his colleagues (2018), showed that the total analgesic requirement during the first postoperative 24 h was (2.34 ± 1.08) for IV group versus (1.26 ± 0.78) for IP group. Based on these findings, a sample size of 50 patients per group
| Table 2: Assessment of groups regarding hemodynamic adverse events | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Adverse event | IV group
(n=50) |
IP group
(n=50) |
X2 | p- value | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Hypotension | 21 (42%) | 10 (20%) | 4.7 | 0.03* | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Hypertension | 24 (48%) | 26 (52%) | 0.04 | 0.84 | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Bradycardia | 17 (34%) | 7 (14%) | 4.4 | 0.035* | ||||||||||||||||||||||||||||||||||||||||||||||||||||
| Data expressed as proportion, x2= chi square, * significant P-value. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Data were analyzed using Statistical package for Social Science (SPSS) version 22.0. Mean ± standard deviation
(SD) were used for quantitative data. Frequency and percentage were used for qualitative data.
Independent-samples t-test of significance was utilized for two means comparison. Chi-square (X2) test of significance was utilized for proportions comparison between two qualitative parameters. Mann Whitney U test compared two-groups in non-parametric data. The confidence interval was set to 95% and the margin of error accepted was set to 5%. P ≤ 0.05 was considered significant.
Results
One hundred patients were enrolled, 50 patients in each group. The two groups were comparable in demographic data (in terms of age, sex, BMI and ASA) and duration of surgery and there were no statistically significant difference between groups (P > 0.05) (Table 1).
IV group was lesser than IP group as regard MABP, and a significant difference was observed before pneumoperitoneum, 10 min, 20 min, 30 min after pneumoperitoneum and after extubation (P = 0.03, 0.03, 0.047, 0.003 and 0.002 respectively) (Figure 1).
Regarding HR, a significant difference was observed before pneumoperitoneum, and at 10 min, 20 min and 30 min after pneumoperitoneum (P = 0.048, 0.006, 0.021, and 0.007) respectively, HR change was small in the IV group as compared to IP group (Figure 2).
Regarding HR, a significant difference was observed before pneumoperitoneum, and at 10 min, 20 min and 30 min after pneumoperitoneum (P = 0.048, 0.006, 0.021, and 0.007) respectively, HR change was small in the IV group as compared to IP group (Figure 2).
| Table 3: Assessment of groups regarding visual analogue scale and total dose of nalbuphine consumption. | ||||
| Time | IV group
(n=50) |
IP group
(n=50) |
Mann-Whitney test | |
| z | p-value | |||
| 30 min | 3 (1-4) | 1 (0-1) | 5.9 | < 0.001* |
| 2 h | 3 (3-5) | 1 (1-2) | 7.04 | < 0.001* |
| 4 h | 5 (4-6) | 3 (2-4) | 5.9 | < 0.001* |
| 6 h | 2 (1-4) | 1 (1-3) | 2.6 | 0.01** |
| 12 h | 4 (2-4) | 4 (1-4) | 1.89 | 0.059 |
| 24 h | 1 (0-1) | 1 (0-1) | 0.8 | 0.42 |
| Postoperative nalbuphine consumption (mg) | 12 ± 3.03 | 8.3 ± 2.8 | 6.4 | < 0.001* |
| Data expressed as Median (IQR): Inter quartile range, * significant P-value, ** highly significant P-value. | ||||
0.03 and P = 0.035) respectively. Although IV group showed less hypertension episodes. but the difference was statistical not significant (Table 2).
| Table 4: Comparative assessment of groups regarding PONV | |||||
| Time | PONV score | IV group
(n=50) |
IP group
(n=50) |
X2 | p-value |
| 30 min | 0 | 20 (40%) | 40 (80%) | 17.2 | <0.001* |
| 1 | 18 (36%) | 5 10%) | |||
| 2 | 9 (18%) | 3 (6%) | |||
| 3 | 3 (6%) | 2 (4%) | |||
| 2 h | 0 | 26 (52%) | 40 (80%) | 8.88 | 0.03** |
| 1 | 13 (26%) | 6 (12%) | |||
| 2 | 9 (18%) | 3 (6%) | |||
| 3 | 2 (4%) | 1 (2%) | |||
| 4 h | 0 | 27 (54%) | 41 (82%) | 9.48 | 0.02** |
| 1 | 12 (24%) | 6 (12%) | |||
| 2 | 8 (16%) | 2 (4%) | |||
| 3 | 3 (6%) | 1 (2%) | |||
| 6 h | 0 | 24 (48%) | 38 (76%) | 10.2 | 0.017** |
| 1 | 16 (32%) | 6 (12%) | |||
| 2 | 8 (16%) | 3 (6%) | |||
| 3 | 2 (4%) | 3 (6%) | |||
| 12 h | 0 | 44 (88%) | 45 (90%) | 1.01 | 0.8 |
| 1 | 4 (8%) | 2 (4%) | |||
| 2 | 1 (2%) | 2 (4%) | |||
| 3 | 1 (2%) | 1 (2%) | |||
| 24 h | 0 | 49 (98%) | 48 (96%) | 0.34 | 0.56 |
| 1 | 1 (2%) | 2 (4%) | |||
| Data expressed as proportion, x2= chi square, * highly significant P-value, ** significant P-value. | |||||
The IP group showed less PONV with significant difference at 30 min, 2 h, 4 h and 6 h postoperatively (P < 0.05). Otherwise there was no statistical difference between two groups (Table 4).
The IP group showed less sedation than the IV group with significant difference at 30 min and 2 h postoperatively. Otherwise there was no statistical difference between two group (Table 5).
Discussion
Magnesium is considered the second most frequent intra-cellular cation with a chief function to preserve homeostasis. Magnesium is an essential factor for cell signaling, the normal function of enzymes and neurotransmission. Studies show that magnesium has an antagonist effect on NMDA receptors, which could affect pain sensitivity and extent.5 The usage of magnesium for perioperative analgesia was
| Table 5: Comparative sedation scores in the groups | |||||
| Time | Sedation score | IV group
(n=50) |
IP group
(n=50) |
X2 | p-value |
| 30 min | 0 | 3 (6%) | 39 (78%) | 54.4 | < 0.001* |
| 1 | 15 (30%) | 6 (12%) | |||
| 2 | 27 (54%) | 4 (8%) | |||
| 3 | 5 (10%) | 1 (2%) | |||
| 2 h | 0 | 35 (70%) | 49 (98%) | 14.7 | < 0.001* |
| 1 | 11 (22%) | 1 (2%) | |||
| 2 | 4 (8%) | 0 (0%) | |||
| 4 h | 0 | 48 (96%) | 50 (100%) | 2 | 0.15 |
| 1 | 2 (4%) | 0 (0%) | |||
| 6 h | 0 | 50 (100%) | 50 (100%) | 0 | 1 |
| 12 h | 0 | 50 (100%) | 50 (100%) | 0 | 1 |
| 24 h | 0 | 50 (100%) | 50 (100%) | 0 | 1 |
| Data expressed as proportion, x2= chi square, * highly significant P-value. | |||||
Pre-emptive analgesia has been a popular practice among anesthetists and its role in the pain management has been widely discussed. It is aimed to avoid CNS sensitization to following stimuli that intensify pain signals.7 Postoperative pain perception has a harmful impact on recovery, hemodynamics, respiration, ambulation, and it prolongs the hospital stay. Unfortunately, it is known that opioid-based analgesia in obese patients is accompanied with critical side effects like apnea, hypoxemia, sleepiness, ileus, delayed ambulation, and so increased mortality rates.1 Although MgSO4 causes mild sedation, it decreases anesthetic needs; this is useful in decreasing residual anesthetic effects in bariatric patients, decreasing risk of postoperative apnea.2
In our study, MABP and HR there were significantly lower in IV group before pneumoperitoneum, 10 min, 20 min, 30 min after pneumoperitoneum and after extubation (Figure 1 and 2). IV group had more frequency of hypotension and bradycardia. We found that attenuation of the hemodynamic changes associated with pneumoperitoneum was better with IV group than IP group. IP group was better in events of bradycardia and hypotension than IV group. This might be due to rapid rise in magnesium levels and ithus onset of action with IV administration.
Our results were similar to those reported by El Mourad and Arafa about the benefits of IV and IP intake of MgSO4 in attenuating the hemodynamic alterations created due to pneumoperitoneum.2 Paul et al. demonstrated a significant decline in HR and MAP throughout pneumoperitoneum for laparoscopic cholecystectomy after administration of 30 mg/kg MgSO4 IV.8 Ali et al. instilled 20 ml MgSO4 10% IP following pneumoperitoneum in laparoscopic cholecystectomy and reported a reduction of unwanted hemodynamic changes in comparison to the controls.9 The IP intake of local anesthetics with or without adjuvant was reported to be efficient in enhancing perception of pain during different laparoscopic surgeries. This might be caused by blockage of visceral afferent pain transmission. Furthermore, absorption from the huge surface like peritoneum might also add to analgesia.2
In our study, the IP group patients expressed less pain perception, and less postoperative nalbuphine utilization than the IV group. Magnesium affects the influx of calcium into the cells and moreover antagonizes NMDA receptors, which affect neuronal signaling and pain processing in the central nervous system. By these receptors blockage, it causes blockage of both somatic and visceral pain fibers and so decreases postoperative pain.10 Similar results in patients undergoing laparoscopic cholecystectomy were shown by other researchers.1,2,5,11,12
A systematic review by Lysakowski et al. did not identify a significant systemic impact of MgSO4 on pain management postoperatively. That might be explained by less clinical trials in addition to fewer participants (n = 778) in comparison with meta-analysis reported by De Oliveira et al. Besides, Lysakowski et al. assessed patients undergoing dissimilar modes of anesthesia, including neuraxial blocks, while De Oliveira et al. limited their study to patients, who underwent operations under general anesthesia.5,13
In our study, the IP group showed less PONV with significant difference at 30 min, 2h, 4h and 6h postoperatively. Similar results were reported by El Mourad and Arafa.2 They explained that by the anesthetic / analgesic sparing actions of MgSO4 had led to reduced frequency of PONV; another clarification was the NMDA antagonist action of MgSO4 on receptors situated in the common pathway of nausea and vomiting. Nevertheless, there is no current information available on the direct effect of MgSO4 on PONV.2,9 On the other side, Kizilcik et al. reported that the prevalence of unfavorable side effects like PONV in addition to shivering was almost similar between the patients, who received IV MgSO4 and control group although morphine consumption was reduced.1
In our study, the IP group showed less sedation with significant difference at 30 min and 2 h postoperatively. In accordance to our results, Elfiky et al. reported that patients receiving IV magnesium needed more time to achieve an Alderete score of 9 to be fit for discharge from PACU; and had higher sedation score in the first 2 h postoperatively than IP group.11 Ali et al. also reported that sedation score was significantly higher in patients receiving IV MgSO4 in comparison with controls during the first 3 h postoperatively.9
The timing of instillation of local anesthetic and adjuvant through the procedure is still debatable. Barczynski et al. recommended early instillation of intraperitoneal local anesthetics before creation of pneumoperitoneum to provide better hemodynamic response and postoperative pain management in comparison with infusion within the closing stages of the procedure. More studies are required to establish the ideal time and the route of administration of MgSO4 for laparoscopic procedures.
Conclusions
Intraperitoneal instillation of MgSO4 is a safe technique that has better results than intravenous infusion in attenuation of hemodynamic response with pneumoperitoneum, and offers reduced postoperative pain and PONV with laparoscopic mini gastric bypass patients.
Limitations
It is not obvious whether magnesium has to be administrated along with the actual or ideal bodyweight in obese patients due to the inadequate information on the usage of MgSO4 in bariatric candidates. We calculated MgSO4 dosage using actual body weight as was done in several earlier studies. Moreover, the timing of the instillation of the local anesthetic and adjuvants remains to be deduced with clear criteria.
Ethics approval and consent to participate
This study was approved by the research ethics committee at the faculty of medicine, Ain Shams University (FMASU M D 235/2020) and registered with Pan African Clinical Trial Registry, identifier: PACTR202111620456298. Written informed consent was obtained from all patients.
Availability of data
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
Competing interests
The authors declare no conflicts of interest.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors.
References
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