A randomized study to assess two different techniques of aspiration while performing transabdominal chorionic villus sampling

Intraoperative Needle Tip Tracking with an Integrated Fibre-Optic Ultrasound Sensor

Ultrasound is an essential tool for guidance of many minimally-invasive surgical and interventional procedures, where accurate placement of the interventional device is critical to avoid adverse events. Needle insertion procedures for anaesthesia, fetal medicine and tumour biopsy are commonly ultrasound-guided, and misplacement of the needle may lead to complications such as nerve damage, organ injury or pregnancy loss. Clear visibility of the needle tip is therefore critical, but visibility is often precluded by tissue heterogeneities or specular reflections from the needle shaft. This paper presents the in vitro and ex vivo accuracy of a new, real-time, ultrasound needle tip tracking system for guidance of fetal interventions. A fibre-optic, Fabry-Pérot interferometer hydrophone is integrated into an intraoperative needle and used to localise the needle tip within a handheld ultrasound field. While previous, related work has been based on research ultrasound systems with bespoke transmission sequences, the new system-developed under the ISO 13485 Medical Devices quality standard-operates as an adjunct to a commercial ultrasound imaging system and therefore provides the image quality expected in the clinic, superimposing a cross-hair onto the ultrasound image at the needle tip position. Tracking accuracy was determined by translating the needle tip to 356 known positions in the ultrasound field of view in a tank of water, and by comparison to manual labelling of the the position of the needle in B-mode US images during an insertion into an ex vivo phantom. In water, the mean distance between tracked and true positions was 0.7 ± 0.4 mm with a mean repeatability of 0.3 ± 0.2 mm. In the tissue phantom, the mean distance between tracked and labelled positions was 1.1 ± 0.7 mm. Tracking performance was found to be independent of needle angle. The study demonstrates the performance and clinical compatibility of ultrasound needle tracking, an essential step towards a first-in-human study.

More chorionic villi obtained at a single center compared to previously published reports

Abstract Objective: The chorionic villus sampling (CVS) technique is not standardized between institutions and can vary greatly between operators. Our goal was to (1) compare the amount of villi obtained by the transabdominal (TA) and transcervical (TC) CVS; (2) compare our single center yield of villi to previously published reports.

METHODS

Women undergoing CVS in a singleton pregnancy between 2009 and 2011 were retrospectively identified at a single center. TA CVS was performed using a 20 gauge spinal needle. TC CVS was performed using a 1.4-mm suction catheter. Milligrams of villi and blood from all TA (n=97) and TC (n=36) CVS were obtained. STATA software was used to perform statistical analysis.

RESULTS

The median amount of tissue obtained during a TC CVS [50 mg ; range (5-200 mg)] was higher than the median amount obtained from TA CVS [36 mg; range (8-140 mg)]; p=0.002. There was more blood contamination in the samples obtained using the TC approach (median=10 mg; range 5-40 mg) than in the samples from the TA approach (median=5 mg; range 0-27 mg); p<0.0001. The amount of villi obtained from our institution was significantly higher than has been previously reported [TC (p=0.0001) and TA (p<0.0001)].

CONCLUSIONS

TC CVS produced significantly more villi than the TA approach. However, both techniques generated enough villi for direct testing. This information may be useful when multiple genetic tests are being requested. Regardless of route of sampling, the volume of villi obtained was higher at our institution than previously reported. More information regarding amount of villi obtained and relationship to pregnancy complications is needed.

Instruments for chorionic villus sampling for prenatal diagnosis

BACKGROUND

Chorionic villus sampling (CVS) is the method of choice for obtaining fetal tissue for prenatal diagnosis before 15 weeks of pregnancy. CVS can be performed using either a transabdominal or transcervical approach. The type of instrument and technique used could have a significant impact on the outcome of the procedure. An ability to manoeuvre the instrument within the uterine cavity without puncturing the gestational sac, to see the tip of the instrument on ultrasound scanning and to minimise the number of instrument passes into the uterus are particularly important.

OBJECTIVES

To compare the efficacy and safety of different instruments and techniques used to obtain chorionic tissue in early pregnancy by the transabdominal or transcervical route. Primary outcomes included failure to obtain an adequate sample (greater than 5 mg of chorionic villi), need for reinsertion of the instrument, pain, and miscarriage following the procedure. Secondary outcomes included mean weight of tissue obtained, successful culture, difficult instrument insertion, poor visualisation of instrument, vaginal bleeding following the procedure and cost per procedure.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2012).

SELECTION CRITERIA

Randomised trials comparing different instruments (forceps, cannula, needle) or techniques for CVS using either transabdominal or transcervical approach.

DATA COLLECTION AND ANALYSIS

Two review authors assessed eligibility and trial quality.

MAIN RESULTS

For transcervical CVS, forceps and cannulae were evaluated in five trials involving 472 women. When a cannula was used, operators failed to obtain an adequate sample (greater than 5 mg of chorionic villi) more often (average risk ratio (RR) 3.81; 95% confidence interval (CI) 1.52 to 9.56). There was no difference in the need for reinsertion of instruments (average RR 2.44; 95% CI 0.83 to 7.20). However, inserting a cannula was more painful (RR 1.93; 95% CI 1.11 to 3.37). There was no difference in spontaneous miscarriage when the use of a cannula was compared with biopsy forceps (RR 1.00; 95% CI 0.14 to 6.96). One study reported the cost of the procedures and found CVS with a cannula to be more expensive (mean difference (MD) $183.7; 95% CI 152.62 to 214.78).When different types of cannulae for transcervical CVS were compared, a Portex cannula was more likely to result in an inadequate sample (RR 2.23; 95% CI 1.25 to 3.98) compared with the silver cannula and to result in a difficult (RR 3.26; 95% CI 1.38 to 7.67) or painful (RR 5.81; 95% CI 1.41 to 23.88) procedure when compared with the aluminium cannula.For transabdominal CVS, two trials comparing different needle techniques were included involving 285 women. One study using an ex vivo system of term placentae was excluded. The included trials compared different continuous negative pressure aspiration techniques with a discontinuous negative pressure system created by a syringe attached to a 20 gauge needle. The studies produced discrepant results. One study found there was no significant difference between groups in the mean weight of chorionic villi obtained (MD 0.40; 95% CI -2.25 to 3.05) or in failure to obtain an adequate sample (more than 5 mg of chorionic villi) on the first attempt (RR 1.02; 95% CI 0.54 to 1.93), whereas the other study found both of these outcomes to be significantly less favourable with the standard discontinuous technique using a syringe (mean weight of chorionic villi obtained: MD -14.80; 95% CI -21.71 to -7.89; failure to obtain an adequate sample on the first attempt: RR 2.73; 95% CI 1.08 to 6.92). There was no difference in rate of miscarriage following the procedure in either study (RR 7.15; 95% CI 0.37 to 136.50; RR 2.93; 95% CI 0.12 to 70.00). Perceived pain by the patient was similar between groups (MD 0.00; 95% CI -0.04 to 0.04) as was success of culture (no failed cases).

AUTHORS' CONCLUSIONS

For transcervical CVS, although there is some evidence to support the use of small forceps instead of cannulae, the evidence is not strong enough to support change in practice for clinicians who have become familiar with a particular technique. For transabdominal CVS, based on current evidence, there is no difference in clinically important outcomes with the use of a continuous compared with a discontinuous negative pressure needle aspiration system.

Technique modifications for reducing the risks from amniocentesis or chorionic villus sampling

BACKGROUND

Currently, the techniques for amniocentesis and chorionic villus sampling (CVS) tend to be described in local and national guidelines, but certain aspects, including the choice of instruments, is predominantly based upon the operator's personal preference. A survey of practice in the specialist UK centres revealed a wide variation of practice; therefore, standardising any element of technique could potentially influence the safety of the procedure.

OBJECTIVES

The objective of this review was to compare the safety and effectiveness of all techniques of performing both amniocentesis and CVS for prenatal diagnosis.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (11 April 2012).

SELECTION CRITERIA

We included all randomised comparisons of different methods of performing amniocentesis after 15 weeks' gestation, or CVS (transabdominal or transvaginal) with each other or with no testing. We excluded quasi-randomised studies (e.g. alternate allocation).

DATA COLLECTION AND ANALYSIS

Both review authors independently assessed for inclusion all the potential studies identified as a result of the search strategy. Both review authors independently assessed trial quality. Both review authors extracted data. Data were checked for accuracy.

MAIN RESULTS

We included five randomised studies with total of 1049 women evaluating five different technique modifications during either amniocentesis (three studies) or CVS (two studies).For amniocentesis three interventions were evaluated - intramuscular progesterone, hexoprenaline and selecting high or low puncture sites for late 'blind' procedure - each intervention in a single small study. There was no conclusive evidence of benefit for any of them. The same applies for terbutaline tocolysis and use of continuous vacuum aspiration during CVS.

AUTHORS' CONCLUSIONS

Overall, the quality of evidence summarised in this review is not of sufficient quality to change current clinical practice. In the absence of clear evidence, the operators should continue to use methods and technique modifications with which they are most familiar with.Any randomised trials of technique modifications that are performed to high standard with adequate safety outcomes and power to detect important clinical differences would be clearly welcome.

New device technologies for subcutaneous fat biopsy

PURPOSE

Subcutaneous fat biopsy is useful for the evaluation of amyloidosis, environmental contaminants, lipid metabolism, genetic studies and diabetes research. The present study examined new technologies for fat biopsy.

METHODS

Subcutaneous fat biopsy in 10 high-risk individuals was randomized to (i) a 10 ml reciprocating procedure device (RPD) mechanical syringe or (ii) a 60 ml vacuum syringe. Outcome measures included pain by the 10 cm Visual Analogue Pain Scale (VAS), adequacy of biopsied tissue, complications and diagnosis. The operator's ability to control syringes was quantitatively measured by the linear displacement method.

RESULTS

Both syringes permitted facile aspiration of subcutaneous fat with adequate sample without complications. The mechanical and the vacuum syringes enhanced control of the needle compared to conventional syringes, reducing unintended forward penetration by 75% (3.6 ± 0.5 mm) and 87% (12.0 ± 1.4 mm), respectively (p < 0.0001). Free adipose cells were obtained in abundance as well as columnar biopsies containing intact blood vessels and connective tissue septa permitting precise microhistological examination. One case of primary AL amyloidosis (κ light chain disease) was diagnosed in each group.

CONCLUSIONS

Subcutaneous fat biopsy by needle aspiration can be facilely achieved with new aspiration syringe technologies with improved needle control and enhanced patient safety.

Syringe and needle size, syringe type, vacuum generation, and needle control in aspiration procedures

PURPOSE

Syringes are used for diagnostic fluid aspiration and fine-needle aspiration biopsy in interventional procedures. We determined the benefits, disadvantages, and patient safety implications of syringe and needle size on vacuum generation, hand force requirements, biopsy/fluid yield, and needle control during aspiration procedures.

MATERIALS AND METHODS

Different sizes (1, 3, 5, 10, and 20 ml) of the conventional syringe and aspirating mechanical safety syringe, the reciprocating procedure device, were studied. Twenty operators performed aspiration procedures with the following outcomes measured: (1) vacuum (torr), (2) time to vacuum (s), (3) hand force to generate vacuum (torr-cm2), (4) operator difficulty during aspiration, (5) biopsy yield (mg), and (6) operator control of the needle tip position (mm).

RESULTS

Vacuum increased tissue biopsy yield at all needle diameters (P<0.002). Twenty-milliliter syringes achieved a vacuum of -517 torr but required far more strength to aspirate, and resulted in significant loss of needle control (P<0.002). The 10-ml syringe generated only 15% less vacuum (-435 torr) than the 20-ml device and required much less hand strength. The mechanical syringe generated identical vacuum at all syringe sizes with less hand force (P<0.002) and provided significantly enhanced needle control (P<0.002).

CONCLUSIONS

To optimize patient safety and control of the needle, and to maximize fluid and tissue yield during aspiration procedures, a two-handed technique and the smallest syringe size adequate for the procedure should be used. If precise needle control or one-handed operation is required, a mechanical safety syringe should be considered.

Instruments for chorionic villus sampling for prenatal diagnosis

BACKGROUND

Chorionic villus sampling (CVS) is the method of choice for obtaining fetal tissue for prenatal diagnosis before 15 weeks of pregnancy. CVS can be performed using either transabdominal or transcervical approach. The type of instrument used could have a significant impact on the success rate of the procedure. An ability to manoeuvre the instrument within the uterine cavity without puncturing the gestational sac, and to see the tip of the instrument on ultrasound scanning are particularly important.

OBJECTIVES

The objective of this review was to assess the effects of instruments used to obtain chorionic tissue in early pregnancy by transabdominal or transcervical route (chorionic villus sampling). The outcomes of interest were technical difficulties during the procedure, quality and quantity of obtained tissue, maternal adverse effects, pregnancy outcome and cost-effectiveness.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group trials register was searched. Date of last search: November 2002.

SELECTION CRITERIA

Randomised trials comparing different instruments (forceps, cannula, needle) for chorionic villus sampling using either transabdominal or transcervical approach.

DATA COLLECTION AND ANALYSIS

Eligibility and trial quality were assessed by two reviewers.

MAIN RESULTS

There were no trials comparing instruments for transabdominal CVS. Forceps and cannula were evaluated in five transcervical CVS trials involving 472 women. When a cannula was used, operators obtained an inadequate sample (less than 5 mg) more often (relative risk (RR) 4.21, 95% confidence interval (CI) 2.15 to 8.25). Compared with forceps, cannulae had to be re-inserted more often (RR 2.98, 95% CI 1.62 to 5.47). Also, inserting a cannula was more painful (RR 1.93, 95% CI 1.11 to 3.37). One study reported the cost of the procedures and found CVS with cannula to be more expensive (weighted mean difference $183.7, 95% confidence interval 152.62 to 214.78). When different types of cannulae were compared, Portex cannula was more likely to result in an inadequate sample and a difficult or painful procedure when compared with either the silver or aluminum cannula respectively.

REVIEWER'S CONCLUSIONS

Although there is some evidence to support the use of small forceps for transcervical chorionic villus sampling, the evidence is not strong enough to support change in practice for clinicians who have become familiar with aspiration cannulae.