Scalp Lead Placement Periprocedural Care

Updated: Dec 28, 2015
  • Author: Michael G Ross, MD, MPH; Chief Editor: Christine Isaacs, MD  more...
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Periprocedural Care

Equipment

The most common fetal scalp electrode consists of a single ECG electrode in the form of a spiral needle. This is attached to paired wires that extend out of the mother’s vagina and are inserted into a ground plate that is typically placed on the maternal thigh. A cable from the ground plate then transmits the ECG signal to the fetal monitor. For placement, the electrode is placed within an introducer, a tube that protects the mother’s vagina from the needle. A device is available that allows the operator to rotate the electrode from outside the vagina, penetrating the fetal scalp with the needle. See the image below.

Parts of a fetal scalp electrode (elements that re Parts of a fetal scalp electrode (elements that remain after introduction of the electrode are 2, 3 and 11, marked with a star (*) 1: Overall electrode with introducer 2: Electrode hub* 3: Spiral electrode* 4: Knob (used to turn the electrode assembly during application) 5: Sheath (transmits turning motion to the electrode hub) 6: Connection between sheath and hub 7: Tube (protects maternal tissues during electrode introduction) 8: Direction of motion of tube during introduction 9: Direction of rotation to set electrode 10: Direction of motion for removal of introducer after electrode is seated 11: Electrode wires*

Embedding the needle in the fetal scalp retains the electrode in place. Other models of scalp electrodes (eg, clip) have also been used.

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Complications

Placement of a fetal spiral electrode rarely may be associated with complications in the mother, the fetus, or the medical practitioner.

Mother

The fetal electrode may lacerate the maternal vagina or cervix during placement or if inadvertently placed on the mother rather than the fetus. In experienced hands, this complication is rare.

The use of internal monitors may also increase the risk to the mother of chorioamnionitis or endometritis, although this is more likely to be associated with internal uterine pressure monitors. A special concern is when a fetal electrode is pulled from the vagina into the operative field at the time of cesarean delivery. Exposure of this type may be reduced by attention to removing the electrode at the time of incision, but some electrodes are difficult to remove; in an emergency, removal of the electrode prior to delivery may not be possible.

Estimating the magnitude of this risk is difficult because mothers undergoing fetal scalp monitoring have various risk factors for infection, especially when followed by cesarean delivery. The incremental risk is likely small. In general, patients delivering after internal monitoring are managed the same as other patients. Those delivering vaginally are observed, whereas prophylactic antibiotic administration is recommended for all patients who undergo cesarean delivery.

Fetus

The fetal electrode may lacerate the fetal scalp. In addition, misplacement of the electrode has resulted in penetration of the fetal eye [3] and use of a fetal scalp electrode has been associated with a fetal cerebrospinal fluid (CSF) leak. [4] Finally, the needle electrode can break, with retention of a portion of the needle in the fetal scalp. [5] These complications are rare, and only case reports appear in the literature.

The placement of a fetal electrode is associated with an increased, although very low, risk of neonatal infection. Newborn scalp abscesses have been described due to Escherichia coli [6] and gonococcus, [7] as well as necrotizing fasciitis of the scalp due to group A streptococcus. [8]

In older literature, placement of a fetal electrode increased the risk of death from neonatal sepsis due to group B streptococcus (GBS); in a study performed before universal GBS screening, the risk was 8 times higher in the electrode group. [9] Placement of a fetal electrode has been associated with an increased risk of fetal transmission of maternal viral agents, including HIV [10] and active genital herpes, [11] and electrode use should be avoided if these infections are present.

Practitioner

The electrode tip may penetrate the glove, and even the hand, of the examiner either at the time of placement or if the electrode becomes dislodged, causing exposure to maternal body fluids. Attention to technique reduces the likelihood of injuries related to electrode placement. Dislodged electrodes should be completely removed if at all possible.

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