Benefits of N-acetylcysteine on liver functions in living donor hepatectomy.

BACKGROUND AND AIMS: The proportion of patients undergoing living donor liver transplantation is high especially in countries without or with limited cadaver organ sharing programs. The aim of this study was to evaluate the post-hepatectomy effect of using N-Acetylcysteine (NAC) infusion in living donors undergoing donor hepatectomy.
METHODS: In a prospective randomised non-blinded study, 50 healthy donors were enrolled; following hepatectomy patients were randomised into 2 groups: Group NC receiving NAC 150 mg/kg diluted in 100 ml glucose 5% over 40 minutes, followed by NAC 12.5 mg/kg in 500 ml glucose 5% over 4 hours. This was followed by NAC 6.25 mg/kg for 2 post-operative days, Group C (Control group) received ringer acetate infusion at same rate for 2 days. The primary outcome was serum lactate levels. Secondary outcomes were liver function tests, serum creatinine and urine output on intensive care unit (ICU) admission (0 hr.), after 24 hours and 48 hours, length of ICU stay.
RESULTS: Our study revealed significant reduction in serum lactate in Group NC at 0, 24 and 48 hours compared to C group (P = 0.017, 0.002, 0.014). INR values showed significant reduction after 48 hours in Group NC compared to Group C (P = 0.049). Total Bilirubin, ALT, and Creatinine, urine output and ICU stay showed no statistical difference between the 2 groups.
CONCLUSION: The NAC protocol is a safe, cost-effective tool for improvement of post hepatectomy liver function and early stabilisation of the metabolic profile. Copyright:

INTRODUCTION

By the end of 2018, Egypt will have an average 3000 registered patients for living donor liver transplantation, which means that there will be same number of donors who will be voluntary donors especially when an established cadaveric programme for organ donation is not established. Thus there is an increased risk related to liver resection in these healthy donors which magnifies the importance of ensuring optimal graft size and function to maintain the donor safety.[1] In our centre, Ain Shams Specialized Hospital we advocate a separate team for donors' evaluation and assessment of fitness in all medical, surgical and psychological fields.[2] One of the most dramatic complications following donors' hepatectomy is postresection liver failure which is dependant on several factors, such as the extent of resection, vascular injury and ischaemic/reperfusion injury (IRI).[345] In our practice, for the past 10 years, we have noticed a transitional impairment of liver function (elevated liver enzymes, total and direct bilirubin, and elevated serum lactate levels) following donor liver resection. Several drugs have been investigated for liver regeneration,[678] with proven benefit of N-Acetylcysteine (NAC) on rats with steatohepatitis.[9] There have been several uses of NAC in treatment of acetaminophen toxicity and prevention of post radiocontrast renal injury, sepsis and cardiac surgeries.[1011] Being a rich source of sulfhydryl (SH) group, this increases the free radical scavenger glutathione (GSH) stores; NAC also plays an important role in decreasing the toxic damage induced by free radicals associated with impaired liver function following hepatic resection.[12]

We conducted this study aiming to study the effects of using NAC post hepatic resection in donors and its possible benefit to the post-operative liver functions.

METHODS

The liver transplantation programme at Ain Shams University Hospitals relies on living related donors. Extra care during anaesthetic management of the donor is warranted because of clear ethical considerations.

This prospective randomised non-blinded study complies with declaration of Helsinki, performed after obtaining approval from the ethical committee of the Ain Shams University FWA 000017585, FMASU R10/2018. All participants provided written informed consent prior to entering the study. The trial was registered at Clinicaltrials.gov with reference number NCT03634566. This study was performed at Ain Shams University Specialized Hospital during the period of April 2018 and April 2019. The authors hypothesised that immediate post hepatic resection use of NAC will improve the liver function tests (ALT, Bilirubin, INR, Serum Lactate) reduce post-operative intensive care admission rates, in addition to lower rates of post-operative hepatic complications.

Sample size calculation was done using PASS programme (PASS version 2011, NCSS, LLC. Kaysville, Utah, USA) setting -1 error (alpha) at 0.05 and the power (1- β) at 0.8. Based on result from a previous study[13] showed that the serum lactate level on day 1 among NAC group was 26.2 ± 7.7 mg/dL, while for the control group, it was 36.3 ± 15 mg/dL. Calculation according to these values produced a minimal sample size of 22 cases per group, with considering a 10% drop out rate. The sample was decided as 25 cases per group. Sample of 50 consecutive healthy adult more than 21 years ASA I or II donors' candidate for right lobe hepatectomy for living donor liver transplantation (LDLT) were included and written informed consent was taken.

All donors have the right to abort and refrain from donation any time during their preparation till the morning of operation. Detailed explanation of the surgical hazards, hospitalisation, medication needs, and mortality rates (which is less than 0.5%) was done by a senior surgical staff. Exclusion criteria included reported allergy to NAC, All patients received conventional pre-operative assessment according to unit protocol to exclude any comorbidities or contraindication to donation. Potential donors were assessed in three phases as per Ain Shams Center of Organ Transplantation (ASCOT) protocol.[14] Standard anaesthetic technique started with routine monitoring tools, including invasive arterial blood pressure through left radial artery catheter, urine output hourly.

Donor operation consisted of right lobe hepatectomy with or without middle hepatic vein; intraoperative abdominal duplex ultrasound was done to delineate the middle hepatic vein and its tributaries and line of dissection.

Following hepatectomy patients were randomised using a computer generated list into two groups: Group NC received NAC 150 mg/kg diluted in 100 ml glucose 5% over 40 minutes followed by 12.5 mg/kg in 500 ml glucose 5% over 4 hours, and later 6.25 mg/kg for first 2 post-operative days. Group C (Control group) received ringer acetate continuous infusion at same rate for 2 days. At the end of operation all patients were fully recovered and transferred to surgical ICU for post-operative care.

Perioperative standard care including the anaesthetic technique, surgical team, dissection and intensive care management were set to avoid any heterogeneity in the study and to assure adequate standardisation of care.

All donors received standard post-operative care in the ICU, including full monitoring of haaemodynamics, urine output, and routine laboratory profile done daily. Initiation of therapy included antibiotics, antiemetic, and analgesia in addition to continuation of NAC infusion. Fluid management consisted ringer acetate 40-60 ml/kg/day to maintain urine output of 100-200 ml/hr.

Generally, patients were started on liquid diet on day one post-operatively, care taken to achieve normovolemic balance with minimal urine output of 1 ml/kg/hr during the ICU stay.

The primary outcome was serum lactate levels. Secondary outcomes were liver function tests (Total Bilirubin, ALT levels, INR), serum creatinine and urine output in ml/hr recorded on ICU admission (0 hr.), and after 24 hours and 48 hours, length of ICU stay, post-operative morbidity or mortality.

50 patients' data were collected, revised, coded and entered to the Statistical Package for Social Science (IBM SPSS) version 23 (Chicago, USA). The quantitative data were presented as mean, standard deviations and ranges when their distribution found parametric. Also qualitative variables were presented as number and percentages. The comparison between groups regarding qualitative data was done by using Chi-square test. The comparison between two independent groups with quantitative data and parametric distribution were done by using Independent t-test. The confidence interval was set to 95% and the margin of error accepted was set to 5%. So, the P value was considered significant at the level of <0.05.

RESULTS

The enrollment period started in April 2018 till April 2019. Herein, we included 50 patients' scheduled for right lobe hepatectomy for living donor liver transplantation (22 males and 28 females) of mean age 26 years and weight 78 kilograms, Table 1 describes the donor characteristics in both NC and C groups with no significant statistical differences. The intraoperative period was uneventful in all patients, with no recorded haemodynamic instability, no blood products given, no need for inotropic support and no mortality recorded, all patients were successfully extubated and transferred to SICU.

Table 1

Demographic date age, sex and weight

Parameter		No=25		Test	P
		Group C	Group NC
Sex (%)	Female	10 (40.0%)	12 (48.0%)	0.325*	0.569
	Male	15 (60.0%)	13 (52.0%)
Age (years)	Mean±SD	26.84±3.94	26.80±3.46	0.038•	0.970
	Range	22-35	21-33
Weight (Kg)	Mean±SD	78.00±4.35	75.88±5.13	1.575•	0.122
	Range	70-85	70-84

P>0.05: Non significant; P<0.05: Significant; *Chi-square test; •Independent t-test

Upon admission to ICU serum lactate, ALT, total bilirubin, Creatinine and international normalisation ratio (INR) were recorded. Our results revealed significant reduction in serum lactate in Group NC at 0, 24, 48 hours compared to group C (P = 0.017, 0.002, 0.014). Similarly INR values also showed significant reduction after 48 hours in Group NC as compared to Group C (P = 0.049) [Table 2 and Figure 1].

Table 2

Lactate, ALT, Total bilirubin and INR at 0, 24, and 48 h

Parameter		No=25		Test•	P
		Group C	Group NC
Lactate 0 h (mmol/l)	Mean±SD	7.12±1.45	6.04±1.62	2.482	0.017
	Range	4-10	4-9
Lactate 24 h (mmol/l)	Mean±SD	4.60±1.08	3.56±1.19	3.231	0.002
	Range	3-7	2-6
Lactate 48 h (mmol/l)	Mean±SD	2.36±0.55	1.88±0.76	2.540	0.014
	Range	1.5-3	1-3
ALT 0 h (U/L)	Mean±SD	696.00±240.62	694.92±180.65	0.018	0.986
	Range	200-1000	200-900
ALT 24 h (U/L)	Mean±SD	479.28±157.93	493.12±126.94	-0.342	0.734
	Range	150-656	150-650
ALTn 48 h (U/L)	Mean±SD	240.40±72.65	207.20±62.02	-1.738	0.089
	Range	80-400	80-300
Bilirubin 0 h (mg/dl)	Mean±SD	2.15±0.32	2.20±0.43	-0.449	0.655
	Range	1.5-2.5	1.5-3
Bilirubin 24 h (mg/dl)	Mean±SD	1.80±0.37	1.75±0.28	-0.513	0.610
	Range	0.8-2.2	1.2-2.2
Bilirubin 48 h (mg/dl)	Mean±SD	1.45±0.46	1.30±0.31	-1.297	0.201
	Range	0.6-2	0.8-1.8
INR 0 h	Mean±SD	1.99±0.34	1.90±0.29	-1.021	0.313
	Range	1.5-2.7	1.5-2.5
INR 24 h	Mean±SD	1.60±0.31	1.50±0.28	-1.149	0.256
	Range	1.2-2	1.2-2
INR 48 h	Mean±SD	1.34±0.31	1.17±0.25	-2.019	0.049
	Range	1-1.8	1-1.8

P>0.05: Non significant; P<0.05: Significant; •Independent t-test

Figure 1

Serum lactate (mmol/l) at 0, 24, and 48 h

Regarding other parameters such as total bilirubin, ALT, and Creatinine there we no statistical difference between the two groups (P > 0.05) similarly urine output also did not show any statistical difference between two groups [Table 3]. With respect to the average ICU stay; there was no difference between the two groups (P = 0.286) [Figure 2] with average 2.4 days.

Table 3

Serum Creatinine and urine output (UOP) at 0, 24, and 48 h

Parameter	Group C NO=25	Group NC NO=25	Test•	P
Creatinine 0 h (mg/dl)
Mean±SD	0.96±0.15	0.93±0.19	0.760	0.451
Range	0.8-1.2	0.8-1.3
Creatinine 24 h (mg/dl)
Mean±SD	0.90±0.10	0.92±0.09	-0.584	0.562
Range	0.8-1	0.8-1
Creatinine 48 h (mg/dl)
Mean±SD	0.83±0.09	0.85±0.07	-0.931	0.356
Range	0.7-1	0.7-1
UOP 0 h (ml/h)
Mean±SD	147.60±47.90	148.80±45.31	-0.091	0.928
Range	80-250	80-250
UOP 24 h (ml/h)
Mean±SD	119.20±32.65	132.80±49.37	-1.149	0.256
Range	80-200	80-250
UOP 48 h (ml/h)
Mean±SD	126.40±38.18	127.60±37.45	-0.112	0.911
Range	90-200	90-200

P>0.05: Non significant; P<0.05: Significant; •Independent t-test

Figure 2

ICU stay (days) in the two groups

There was no recorded post-operative morbidity or mortality during the hospital stay, neither patients required post-operative surgical neither intervention nor ICU re-admission.

DISCUSSION

Donors' safety is one of the main priorities as an anaesthetic team in management of living donor liver transplantation especially on a programme relying only on living donation. Post hepatectomy liver impairment is one of the serious complications following donation; which depends on several factors such as extent of resection, hepatic parenchymal status and prolonged ischaemia to the hepatic tissues. NAC being an antioxidant agent may reduce this insult, but no randomised controlled trial (RCT) is available to support of use of NAC in donor hepatectomy. Studies performed on the recipients showed that NAC is of benefit regarding the hepatic protection in Orthotopic LT.[1516] The Liver is the primary organ responsible for clearance of serum lactate and impairment of lactate clearance is strongly associated with hepatic impairment and dysfunction.[1718]

In the process of liver resection in donors' hepatectomy we observed elevated levels of lactate which reflects mitochondrial dysfunction and causes further acid base disturbances and acidosis. The consequences of lactic acidosis may affect the hepatic function in the post-operative period as described in several studies.[1920] Effective lactate clearance post hepatectomy is associated with lower morbidity and mortality rates.

In our study starting the intraoperative infusion of NAC after liver resection significantly improved the lactate clearance values [Table 2 and Figure 1] compared to control group. Although lactate measurement as a single marker is not the ideal method for assessment of liver dysfunction,[21] early rise in serum lactate indicates accelerated hepatic dysfunction and gross pathological changes.

With respect to our donors' characteristics [Table 1] our results are similar to another study performed in Italy.[22] We did not find post-operative hepatic dysfunction in any of our patient. One of the reason may be that our center is not accepting donors with extended donor criteria. Other European centers[23] assessed the use of NAC protocol in recipients of LT which differ from our study in allocation of MELD scores and graft survival as we concentrated on the post-operative donors' hepatic function. However, if we added together these demographic considerations, it would provide good results for the NC group which favors the effect of NAC protocol.

All earlier studies focused on the impact of NAC on recipients of LT and they have thus failed to express clinical benefit.[2425] The reason that we used NAC protocol was because of a previous trial performed at King's college[15] on Orthotopic LT focusing on the haemodynamic parameters and oxygen delivery. In this study, Bromely et al. proved that the significance of improvement of oxygen transport following the loading dose with no effect observed on the graft function, sepsis, or any other complication.

In our study, the use of NAC improved post-operative Lactate clearance levels by the first day in the ICU in addition to significant reduction of INR by the second day post operatively (P = 0.049) compared to control group not receiving NAC, which reflects the improvement of synthetic function of the liver, but no effects were observed on the other liver function tests such as total bilirubin, ALT. We feel that these values were due to the effect of intraoperative infusion of NAC; as it gives a potential time for the donor's liver to replenish its own metabolic stores of GSH minimising the toxic effects of the free radicals.[26]

The benefits of NAC on the renal function following contrast agents is well known.[10] Our study did not show any effect on post-operative serum Creatinine levels and urine output during the ICU stay [Table 3], although nephrotoxic agents were not used. The adequate safety of the NAC, in addition to its low costs, positive effect as an antioxidant drug following hepatectomy in living donors' LT makes the establishment of NAC protocol cost-effective especially in developing countries with average total cost of living donor LT of 15,000 $.

The limitations of the current study are the single center experience. Therefore, our results should be cautiously considered until further studies are conducted on living donor hepatectomy.

So what is the impact of this study on LDLT? Our study suggests that NAC could be beneficial in improving post-operative hepatic function by reducing serum lactate levels and stabilising the acid/base status of the living related donors, thereby optimising metabolic profile.

CONCLUSION

In a center that relies only on living organ living transplantation and where rendering donors' safety a top priority, the NAC protocol is a safe anda cost-effective tool for improvement of post-hepatectomy liver function and stabilisation of the metabolic profile.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.