New 20 Gauge Thin Tip Needle Reduces Pain During Oocyte Retrieval

Over the past two decades, ultrasound-guided transvaginal aspiration has emerged as the gold standard for oocyte retrieval in IVF. Pain experienced during the procedure is influenced by factors such as anxiety, type of analgesia, type and amount of additional IV analgesia, needle sharpness and diameter, pain threshold of the patient, and the doctor’s skills. A prospective, randomized, comparative, multi-centre study reports significant pain reduction, without any delay in the retrieval process or effect on retrieval rate with a newly designed, thinner-tipped reduced needle (RN) in contrast to the thicker standard needle (SN).

The SN has an outer diameter of 1.4 mm (17 gauge) and an inner diameter of 1 mm across the entire length of the needle. Matts Wikland, Department of Obstetrics and Gynaecology, Göteborg University, Sweden, and coworkers compared SN with RN, which had an outer and inner diameter similar to the SN except for a length of 50 mm from the tip, where the outer diameter was 0.9 mm (20 gauge) and inner diameter was 0.6 mm. The study published in the journal Human Reproduction, included 257 patients (SN=128; RN=129) who self-evaluated and recorded their pain experience immediately after oocyte aspiration on a visual analogue scale (VAS) which ranged between
• 0 mm=no pain
• 100 mm=unbearable pain

Regardless of whether the data were evaluated per intention-to-treat (ITT) or per protocol population (PP), there were no variations in the patient characteristics among the two groups. Similar aspiration time, number of good quality embryos and embryos for freezing, additional IV analgesia, oocyte recovery, fertilization, cleavage rate, and pregnancy rate were achieved with the use of both the needles. The researchers concluded that use of the RN results in a significant reduction in overall pain and lesser than expected vaginal bleeding (Table 1), without any detrimental effects on the oocyte or the IVF outcome.

Outcomes measured

RN

SN

P value

95% CI

Pain during oocyte retrieval

21.0±17.5 (Mean±SD)

26.0±19.9 (Mean±SD)

0.040

9.7 to -0.4

Vaginal bleeding

32%

19%

0.03

1.7 to 23.0

Earlier, Miller et al (Fertility Sterility, 2004) conducted a prospective randomized single-blinded study comparing two different 17-gauge follicle aspiration needles for efficiency and tolerance in a large IVF program. They included 300 women blinded to Echotip® (standard needle; n=149) or follicle aspiration set (FAS; n=151) during transvaginal ultrasound-guided oocyte retrieval. An evaluation of the number of eggs retrieved, and pain or cramping scores (at 30 mins and 24 hours, post-retrieval) showed no difference between the two needles. The researchers concluded that FAS is equally effective and as well tolerated as the standard needle.

To determine the best approach for reducing pain in patients undergoing transvaginal oocyte retrieval, a review by Kwan et al (Cochrane Database Systemic Review, 2005) compared the efficiency of analgesia and conscious sedation with other techniques of reducing pain and arrived at the following:
• No specific method could be considered superior in decreasing pain during oocyte retrieval.
• Subjective and objective approaches should be utilized to assess pain.
• Methods to assess pain and its timing during and following the procedure requires greater consensus.

Since the introduction of the transvaginal ultrasound-guided oocyte retrieval, thin needles are being used. Although associated with reduced pain, thin needles can increase the aspiration time or injure the oocyte-cumulus complex with a drift from their puncture line. According to the current study findings, the reduced diameter of the last 40-50 mm of the needle, which penetrates the wall of the vagina and into the ovary, does help significantly to decrease pain during oocyte retrieval. However, larger clinical trials are needed to substantiate these findings.

References

1. Wikland M, Blad S, Bungum L, Hillensjö T, Karlström PO, Nilsson S. A randomized controlled study comparing pain experience between a newly designed needle with a thin tip and a standard needle for oocyte aspiration. Hum Reprod. 2011 Jun;26(6):1377-83.

2. Miller KA, Elkind-Hirsch K, Benson M, Bergh P, Drews M, Scott RT. A new follicle aspiration needle set is equally effective and as well tolerated as the standard needle when used in a prospective randomized trial in a large in vitro fertilization program. Fertil Steril. 2004 Jan;81(1):191-3.

3. Kwan I, Bhattacharya S, Knox F, McNeil A. Conscious sedation and analgesia for oocyte retrieval during in vitro fertilisation procedures. Cochrane Database Syst Rev. 2005 Jul 20;(3):CD004829.

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