Comparison of Bromocriptine and Hydroxyethyl Starch for Reducing Ohss in in Vitro Fertilization Patients: A Retrospective Study

Background: The ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening complication associated with controlled ovarian hyperstimulation (COS) during assisted reproductive technology (ART) treatment, and effective preventive measures are urgently needed. The dopamine agonist can mitigate OHSS incidence through a decreased vascular permeability via reduced vascular endothelial growth factor (VEGF) production. This study evaluated the clinical effectiveness of bromocriptine, an alternative DA, for prevention of OHSS in high risk women. Methods: The retrospective study population consisted of women undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycles with GnRH antagonist protocols, at risk of OHSS. The study group included 52 women given 2.5 mg bromocriptine daily by rectal insertion for 5 days beginning on the day of oocyte retrieval; the control group included 52 women given 500 ml intravenous (I.V.) hydroxyethyl starch (HES) daily for 5 days also beginning on the day of oocyte retrieval. The outcomes of ovarian stimulation, incidence and severity of OHSS, blood-related indicators, biochemical indicators (liver and renal function), and coagulation and �brinolytic activities were compared. Results: The groups were not signi�cantly different in age, estradiol concentration on the day of human chorionic gonadotropin injection, or number of retrieved oocytes. The occurrence of mild (13.46% vs 15.48%) and moderate (7.69% vs 5.77%) OHSS were not signi�cantly different between bromocriptine and HES groups (P>0.05). No cases of severe or late OHSS were recorded in either group. Only hemocratin levels were signi�cantly higher and activated partial thromboplastin time was signi�cantly lower in the bromocriptine group (P<0.05) compared to the HES group on Day 5 after oocyte retrieval. No difference in liver or renal function was found between groups. Conclusions: Prophylactic rectal administration of bromocriptine was as effective as I.V. HES for prevention of OHSS.


Introduction
Assisted reproductive technology (ART) therapy may be accompanied by the development of ovarian hyperstimulation syndrome (OHSS), a complication that is connected to controlled ovarian hyperstimulation (COS), which can be potentially fatal in some circumstances.During OHSS, the ovaries become enlarged and an acute shift in uids occurs from the intravascular to the third space, sometimes resulting in uid accumulation in the peritoneal and thoracic cavities, with subsequent hemoconcentration, elevated hematocrit, and decreased organ perfusion [1][2][3].Kidney failure, respiratory distress, and death are all complications associated with OHSS [4].
As much as 20-33% of in vitro fertilization (IVF) cycles may be affected by mild OHSS, whereas moderate to severe OHSS can reportedly occur in 3% to 8%, respectively, during ART cycles, the proportions are likely to be substantially higher among women with polycystic ovaries, high oocyte yield from OPU, or other high risk factors [5].Some studies have proposed that OHSS-related uid accumulation may develop in high-risk women due to greater vascular permeability associated with stimulation by ovarian steroids and treatment with human chorionic gonadotropin (hCG).Moreover, several hormones and factors have been identi ed as potential etiological agents in OHSS, including prostaglandins, inhibin, the renin-angiotensin-aldosterone system, as well as several in ammatory factors [6], with vascular endothelial growth factor (VEGF) serving as the primary mediator of this syndrome [7] [2,8].
A systematic literature review and meta-analysis revealed that prophylactic administration of dopamine agonist (DA) can lead to signi cantly reduced incidence of OHSS among high-risk patients, most substantially so among early onset cases [9].A growing number of studies have evaluated cabergoline as a pharmacological agent to reduce OHSS incidence and severity.However, cabergoline is unavailable in many parts of the world, including mainland China.An alternative DA, bromocriptine, which is widely available, has also been previously reported to attenuate OHSS, but has received less research attention [10].This study aimed to compare the prophylactic effectiveness of rectal bromocriptine administration with that of hydroxyethyl starch (HES) infusion in the prevention of OHSS among high risk women receiving ART.

Subject recruitment
This retrospective study was performed at the Department of Human Reproductive Medicine, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing.We enrolled 104 infertile women at high risk of developing OHSS from among the patient population with IVF or intracytoplasmic sperm injection (ICSI) cycles between February 2019 and December 2020 in our clinic."High risk of OHSS" was de ned as serum estradiol (E 2 ) levels >3000 pg/ml at the time of trigger, and/or retrieval of 20 or more oocytes [11].The exclusion criteria were patients with a history of cancer, only one ovary, as well as coasting cases.The Institutional Review Board and Ethical Committee of Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing approved this retrospective study.

OHSS preventive treatment administration
One-hundred and four patients at high risk of OHSS were eligible: the study group (n = 52) received 2.5 mg bromocriptine through daily rectal administration for 5 days, starting on the day of oocyte retrieval (i.e., Day 0), while the control group (n = 52) received a slow intravenous (I.V.) infusion of 500 ml HES daily for 5 days, beginning on the day of oocyte retrieval.

Assessment of ovarian hyperstimulation syndrome
OHSS was diagnosed and classi ed as previously described by Humaidan et al [13].Patients were assessed for clinical symptoms, signs, and laboratory data of OHSS at 5 days after oocyte retrieval."early OHSS" was de ned as occurring ≤9 days after oocyte retrieval, while presentation of OHSS later than 9 days was classi ed as "late OHSS'' [14].
In both groups, hematological tests were performed before ovarian stimulation (i.e., baseline) and on the 5th day after oocyte retrieval (i.e., Day 5) to determine the white blood cell (WBC) and platelet (PLT) counts, hematocrit (HCT) content, liver and renal function, and coagulation and brinolytic parameters.

Statistical analysis
Statistical analysis was performed using SPSS (Version 16, SPSS Inc., Chicago, IL, USA).Results of the study were expressed as means±standard deviation (S.D.) or number (percentage).Chi-square test or student t-test were performed to evaluate the statistical differences between the variables.P<0.05 was considered signi cant.

Baseline characteristics
The patients' baseline characteristics and clinical features are shown in Table 1.There were no signi cant differences between the two groups with regard to age, BMI, duration of infertility, basal serum follicle stimulating hormone (FSH) levels, basal luteinizing hormone (LH) levels, basal E 2 levels, or type of infertility.In addition, their characteristics related to OHSS risk factors, including ovarian antral follicle count (AFC) and anti-Müllerian hormone (AMH) levels were also similar between in the study or control groups (Table 1).

Ovarian stimulation outcomes
No signi cant differences were found between the rectal bromocriptine administration or I.V. HES groups in terms of their duration of ovarian stimulation in days (P>0.05),total amount of gonadotropin (Gn) dose (P>0.05), and endometrial thickness on the day of trigger (P>0.05).The subjects' characteristics were also similar between groups in relation to OHSS-associated risk factors including E 2 levels on the day of trigger, on the day of ovum pick-up (OPU), and on the 5th day after oocyte retrieval, as well as in the number of retrieved oocytes (Table 2).Day 0: on the day of ovum pick-up (OPU) Day 5: on the 5th day after oocyte retrieval OHSS Outcomes o signi cant differences were observed in the incidence of mild or moderate OHSS between the bromocriptine and HES groups.Moderate OHSS was observed in 4 patients in the bromocriptine group, while 3 cases occurred in the HES group (7.69% vs 5.77%), with no signi cant differences in the two groups.These cases were all categorized as "early OHSS", and no severe OHSS or late OHSS were observed in either the study or control groups (Table 3).There were no signi cant differences found between the two groups in their baseline HCT, WBC, and PLT counts (i.e., before ovarian stimulation).However, on the 5th day after oocyte retrieval, WBC counts were signi cantly higher in both groups compared with their baseline WBC (P <0.05).Furthermore, WBC count and HCT were both signi cantly higher in the bromocriptine group compared to the HES group (P <0.05) on the 5th day after oocyte retrieval (Table 4).On Day 5: on the 5th day after oocyte retrieval There were no statistically signi cant differences in coagulation and brinolytic parameters before ovarian stimulation between patients who received bromocriptine versus HES; only the activated partial thromboplastin time (APTT) was lower in the bromocriptine group than in the HES group on the 5th day after oocyte retrieval (P< 0.05).FIB, TT and D-D were signi cantly higher in both groups compared with their baseline levels (all P <0.05) (Table 5).Baseline: before ovarian stimulation On Day 5: on the 5th day after oocyte retrieval In assays for liver and kidney function, we found no signi cant difference between the two groups, either at baseline prior to ovarian stimulation or on the 5th day after oocyte retrieval (P >0.05).Both groups showed signi cantly higher transaminase activities, including ALT and AST, on the 5th day after oocyte retrieval compared with baseline (P <0.05) (Table 6).Baseline: before ovarian stimulation On Day 5: on the 5th day after oocyte retrieval In addition, the medication was well-tolerated by all patients in the study group, with no obvious side effects recorded in either the bromocriptine or HES groups.

Discussion
This retrospective study evaluated the effectiveness and physiological effects of rectal bromocriptine administration in OHSS prevention among high risk women undergoing IVF treatment.When compared with I.V. HES, a similar proportion of patients given bromocriptine experienced moderate OHSS, and in all cases the rectal bromocriptine was well-tolerated with no recorded adverse events, avoiding infection of vaginal administration after OPU.Overall, rectal administration of bromocriptine is an effective, safe, convenient, and relatively economical approach to OHSS prevention.
Estradiol levels and number of retrieved oocytes are the two most commonly used risk markers for OHSS during COS for IVF.A number of reports have shown that the rate of OHSS incidence increases along with elevated serum estradiol [15], [14,[16][17][18], although there is currently a lack of consensus on an appropriate threshold cut-off for estradiol-associated risk.By contrast, the number of oocytes retrieved following follicular aspiration can serve as a more precise marker for risk of OHSS development [19].According to Papanikolaou et al. [20], a threshold of ≥18 follicles ≥11 mm in diameter and/or serum estradiol ≥5000 pg/ml yielded an 83% sensitivity rate with a speci city of 84% for predicting severe OHSS cases.In some studies, the patients were included if ≥20 oocytes could be retrieved and/or E 2 levels were >3000 pg/ml on the day of hCG [21,22], which were the standards adopted for inclusion in our study.
Several recent innovative approaches have addressed the need to mitigate the risk and severity of OHSS in IVF/ICSI cycles [10].These strategies for OHSS prevention include [23] individualized COS, cancelling of the cycle, coasting [4,24], individualizing the hCG trigger doses, or administration of a GnRH agonist for patients receiving GnRH antagonist [13,25,26].In addition, aspirin in low doses has also been examined as a possible preventive measure for OHSS [27].Other approaches include the use of I.V. uids at the time of oocyte retrieval, such as albumin, HES [28, 29], and calcium [30], as well as embryo cryopreservation for later transfer during an unstimulated cycle.Ultimately, the discovery that the proangiogenic cytokine VEGF functions as the primary contributor in OHSS pathogenesis, followed by the insight that VEGF activity could be modulated via dopamine, together, have resulted in the broad of DAs for prevention of OHSS-associated events and symptoms.Speci cally, in vivo studies have shown that DAs post-transcriptionally regulate the secretion of VEGF in luteinised granulosa cells [31].Previous research in a rat ovarian hyperstimulation model showed that administration of low-dose DA can inhibit VEGF-mediated vascular hyperpermeability but does not affect VEGF receptor 2-dependent luteal angiogenesis [32].Notably, DAs can increase renal blood ow by affecting VEGF receptor, glomerular ltration, and sodium excretion, subsequently preventing development of ascites and facilitating cytokine secretion (e.g., VEGF), thus suggesting the potential utility of DAs in OHSS therapy [33].Among DAs, cabergoline has been reported as a reliable prophylactic treatment to limit OHSS incidence and severity among high risk patients [9] [24,[34][35][36][37][38][39][40].Bromocriptine has received attention for similar effects to cabergoline, although few clinical studies have explored its properties in the prevention of OHSS.Bromocriptine is an ergot alkaloid dopamine receptor agonist that is potent as an agonist of the dopamine-2 receptor, but also functions as a weak dopamine-1 receptor antagonist.An initial series of trials apparently show that bromocriptine is as effective as cabergoline against OHSS, but is considerably lower in cost [41].These current studies all used 2.5 mg bromocriptine daily, but vary in their starting time and duration of administration, with some beginning on the day of OPU [22,42], and others on the day of hCG [43], and have a maximum duration spanning 16 days.In our study, bromocriptine was administered for only 5 days, and appeared to result in good prevention of OHSS.One study reported contradictory results in which bromocriptine did not affect OHSS incidence.However, this study used an exceptionally low sample size of only 14 patients and fresh embryos were used for transplantation [43].I.V. HES is regarded as an effective approach in the reduction or attenuation of OHSS incidence among high risk patients(28), and is widely used among ART units for prevention of OHSS [13] [44].Since HES administration can lead to signi cantly increased vascular system volume [45], its administration therefore may also be accompanied by elevated osmotic pressure and decreased blood viscosity.Furthermore, the inhibition of platelet aggregation induced by HES can also reduce blood coagulation [46], thus circumventing hypovolemia and hemoconcentration [47].It also warrants mention that DAs inhibit the phosphorylation of VEGF receptor-2 [32,48].The activity of bromocriptine in decreasing vascular permeability and concurrent reduction in VEGF production can at least partially explain its mechanism of inhibiting OHSS.In this retrospective study, we observed no signi cant differences in the incidence of mild (13.46% vs 15.38%) and moderate (7.69% vs 5.77%) OHSS between the bromocriptine and HES groups (P>0.05), and no patient in either group developed severe OHSS and late OHSS.Our results indicated that rectal administration of bromocriptine was as effective as HES in reducing OHSS.In particular, the WBC counts and HCT values were higher in the bromocriptine group on Day 5 after oocyte retrieval than in the HES group, while APTT was shorter.Our study thus indicated that coagulation in the bromocriptine group did not improve as strongly as in the HES group.
Transaminase ALT and AST levels were also higher on Day 5 after oocyte retrieval than at the baseline prior to ovarian stimulation in both two groups, however, the values were within the normal range.This increase in ALT and AST may be related to the rise in estradiol levels in the patients during COS, which aggravates the burden on the liver.However, all transaminase levels were in the normal range for both groups.In addition, we found no signi cant difference in renal function between the baseline and Day 5 post oocyte retrieval for either group.These results show that bromocriptine is su ciently safe and does not appear to affect liver and renal function at these doses which are appropriate for OHSS prevention [43].
Disadvantages of bromocriptine include the known side effects of nausea, headaches, and orthostatic dysregulation [49].In one study, 24% of the patients displayed transient gastrointestinal intolerance to DA treatment [50].Notably, patients with OHSS may experience gastrointestinal symptoms including nausea and vomiting in the absence of treatment.Given that some clinical trials have used oral administration [42,43], which may have resulted in substantial aggravation of gastrointestinal reactions for patients with high-risk of OHSS.We therefore opted for bromocriptine administration via rectal insertion to avoid these side effects.Moreover, the relatively low dosage used in this study was apparently well-tolerated by our sample population, more convenient for patients than I.V. delivery.The lower price of bromocriptine compared with HES also provides a cost-saving bene t that is also appreciated by patients.

Conclusion
The present study showed that rectal administration of 2.5 mg bromocriptine daily for 5 days beginning on the day of oocyte retrieval was apparently as effective as I.V. HES for reducing OHSS in patients at high risk of developing OHSS during gonadotropin ovarian stimulation in the context of IVF/ICSI cycles.

Table 1
Baseline characteristics and clinical features of patients in two groups Note: Values represent means ± standard deviation (SD) or number (percentage)

Table 2
Ovarian stimulation outcomes in two groups Note: Values represent means ± standard deviation (SD)

Table 3
Incidence of OHSS in patients given bromocriptine or HES Note: Data are expressed as number (percentage)

Table 4
Blood-related parameters before ovarian stimulation and on the 5th day after oocyte retrieval * Compared to the I.V. HES group at the same period; # Compared to the same group at baseline before ovarian Haematocrit: HCT; White blood cell: WBC; platelet: PLT Baseline: before ovarian stimulation

Table 5
Coagulation and brinolytic parameters at baseline and on the 5th day after oocyte retrieval

Table 6
Liver and renal function before ovarian stimulation and on the 5th day after oocyte retrieval in the two groups Note: Values represent means ± standard deviation (SD) # Compared to the same group at baseline before ovarian ALT: alanine aminotransferase; AST: aspartate aminotransferase; GGT: glutamyl transpeptidase; BUN: blood urea nitrogen; UA: uric acid; CRE: creatinine; eGFR: estimated glomerular ltration rate.