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Methods

We chose an ex vivo model for conducting the tests. Circular samples of fresh pork skin (thickness, approximately 19 mm) were made with use of a stamping tube. Then, 2‐mL samples of fresh, human whole blood were obtained by using the Sarstedt Monovette system, and sodium citrate was added to the samples to prevent coagulation during the subsequent tests. The blood sample for each test was obtained from the same person performing the test to rule out any risk of infection.

First, 1.5 mL of blood was pipetted from the available sample and was mixed with approximately 1 μL of highly radioactive (approximately 15 MBq/μL) Technetium solution (⁹⁹Tc). The activity in the 1.5‐mL radioactive blood sample was gauged by using an activimeter (Isomed 2000) and was recorded.

To simulate the percutaneous injuries, the samples were mounted in a holder, and a single finger from a medical glove (Biogel; Mölnlycke) was stretched over the sample. The patented double‐gloving technique with indicator (BiogelEclipse Indicator; Mölnlycke) was used to test blood contact with double‐gloved hands. This double‐gloving technique involves use of a green inner glove that is an approximately half‐size larger than necessary and that is worn with a straw‐colored outer glove.

We only conducted tests with at least 1 layer of latex, because it is no longer common to perform operations without sterile gloves. Each test configuration was repeated 40 times under identical conditions.

To simulate punctures with surgical suturing needles, we first applied 3 μL of blood with a dosing pipette (Brand Transferpette 20 μL; accuracy, 0.02%) to the outside of each test glove. Then, preloaded safety lancets (Owen Mumford Unistik3 Normal, 21G; depth of puncture, 2.4 mm ) were used to pierce the glove through the applied blood. By using preloaded safety lancets, we were able to ensure that each puncture took place under identical conditions (ie, the same duration and depth of puncture). Injuries caused by sharp objects such as bone fragments and scissor tips were also simulated with an automatic lancet (Owen Mumford Unistik2 Neonatal, 18G; depth of puncture, 1.8 mm) equipped with a blade‐shaped needle (Figure 1). These tests were also conducted by puncturing a glove with 3 μL of preapplied blood.

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Figure 1.  The 2 automated lancets used in the study: Unistik Normal (left) and Unistik Neonatal (right).

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Punctures with scalpel blades (Otto Rüttgers KG Mini Blades [used for microsurgery]; material thickness, 0.6 mm) were made by using a specially constructed automated puncturing device (Figure 2). The scalpel blades were immersed in blood at a depth of 10 mm for 30 seconds; then, the puncturing device performed identical punctures (depth, 3 mm). We originally developed the puncturing device for measuring blood volume transfers with cannule punctures. The device reproducibly and constantly maintains the testing parameters, such as puncture depth, duration, and speed.

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Figure 2.  Automated puncturing device with which scalpel blade injuries were simulated.

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Each sample was then gauged by using a γ well‐counter connected to a computer (Maestro MCB 129). The transferred blood volume was calculated according to the radioactive decay determined 1 minute after blood contamination. Before taking measurements, the gauge was calibrated daily to the energy region of the Technetium activity with use of 2 different emitters (¹³¹I and ⁹⁹Tc). The region of interest was calibrated to 10 MeV greater than and 10 MeV less than the mean β‐decay energy (141 MeV) of the ⁹⁹Tc isotope. The data were analyzed using SPSS, version 14 (SPSS).

Results

A mean volume of 0.064 μL of blood (median, 0.037 μL; standard error of the mean [SEM], 0.012 μL) was transferred in punctures with the Unistik3 Normal automatic lancet at a depth of 2.4 mm through 1 layer of latex. With the double‐gloving indicator technique, a mean volume of only 0.011 μL of blood (median, 0.007 μL; SEM, 0.003 μL; ) was transferred; thus, use of 2 pairs of gloves, the transferred volume of blood was reduced by a factor of 5.8.

Punctures with the blade‐shaped Unistik2 Neonatal lancet through a single layer of latex transferred a mean volume (±SD) of μL of blood (median, 0.113 μL; SEM, 0.011 μL), which was considerably more than the amount transferred when punctures were made with the needle‐shaped Unistik3 Normal lancet, even though the puncture depth of the Unistik2 Neonatal lancet was only 1.8 mm. When punctures were made through a double layer of latex, the transferred mean volume (±SD) decreased to μL (median, 0.027 μL; SEM, 0.005 μL; ), which resulted in a factor of protection of 3.8.

Needlestick injuries through a single layer of latex simulated with blood‐contaminated mini‐blades resulted in a mean transferred volume of blood (±SD) of μL (median, 0.141 μL; SEM, 0.016 μL); through a double layer of latex, the mean transferred volume of blood (±SD) was μL (median, 0.028 μL; SEM, 0.005 μL; ). Double gloving resulted in a factor of protection of 4.6 (Figure 3).

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Figure 3.  Box plot showing the transferred blood volume in ex vivo tests with 3 different automated puncture devices and with single and double gloving. Grey boxes, interquartile range (IQR); black lines within the boxes, median values; horizontal lines outside boxes, range excluding outliers and extreme values; black circles, outliers (values >1.5 and <3 times the IQR from the 75th percentile); stars, extreme values (values >3 times the IQR from either the 25th or the 75th percentiles).

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All punctures of the double layer of latex were clearly identifiable by the green coloring of the puncture site. This coloring is the result of fluids entering the space between the gloves through the puncture site, which causes the green inner glove to show through the straw‐colored outer glove.

Discussion

A series of studies has been conducted worldwide on the risk of surgical personnel being exposed to blood‐borne pathogens.³ In those studies, blood contact and/or injury was usually detected by inspecting the latex gloves worn during surgical procedures. The glove puncture rate was most frequently determined by filling the gloves with water or by using electrical measuring methods similar to those used for condom testing.⁴ In every study, the glove puncture rate depended on the type of surgical procedure (ie, there is an increased the risk of blood contact during longer procedures⁵); operations that required great effort and involved bones^6,7or deep locations⁸ resulted in glove puncture rates of up to 70%. The risk of blood contact during endoscopic procedures was significantly lower, with a puncture rate of approximately 9%.^9–11 The lead surgeon and the assisting personnel have the highest risk of injury.^12,13

Improved protection against infection can be achieved by wearing 2 pairs of gloves. Many studies have proven the benefits of double gloving in preventing blood contact. Studies from the United States^14,15 determined that double gloving can reduce the risk of blood contact by a factor of 10. Two other studies found that use of doubled surgical gloves reduced the rate of blood contamination among surgeons from 70% (in both studies) to 13% (in one study) and 2% (in the other study).^16,17 The rate of blood contamination was minimized despite a puncture in the outer glove, because the inner glove remained intact in up to 82% of cases.^18–20

Protection against infection can be increased even more by double gloving with an indicator glove. This gloving technique includes a colored inner glove and an outer glove that is neutral in color. If the outer glove is punctured during the operation, the fluids present in all procedures will appear as a clearly visible spot at the site of the puncture. Once such a spot is noticed by any member of the surgical team, the glove can be replaced, thus minimizing the risk of an infection that results from continuing with the operation.

To date, the studies conducted on early detection of glove punctures during surgical procedures have revealed that indicator gloves are very effective. Compared with complicated electronic indicator systems that often tend to sound the alarm because of changes in the conductivity of the latex gloves,^21,22 indicator gloves enable the detection of up to 100% of punctures immediately after they occur.^23,24

A meta‐analysis of the 18 studies conducted on glove safety worldwide found that double gloving led to 3 times fewer contacts with blood, compared with using a single pair of gloves. No concentrations of punctures on the outer glove were found that could indicate a reduction in hand sensitivity or dexterity.³

Although the protective effect of double gloving is very evident, it is not yet routine practice. This is mainly attributable to the alleged reduction in dexterity and sense of touch through the double layer of latex. A study conducted at the University of Wuppertal (Wuppertal, Germany), in which participants underwent a standard neurological 2‐point discrimination test and a “dice test” (in which the blindfolded participant had to determine the number of pips on dice of various sizes), found no significant reductions in the sense of touch in those wearing 2 pairs of gloves.²⁵ A US study that tested both sense of touch and dexterity found that 2 pairs of gloves had an adverse effect only on the surgeons who normally operated with a single pair of gloves; within a short period, however, even these surgeons became accustomed to using 2 pairs of gloves.²⁶

Our tests prove that double gloving also has a positive effect on the blood volumes transferred by surgical needlestick injuries. Use of 2 pairs of gloves led to a significant reduction in transferred blood volume in all of the tests.

Therefore, it has been established that double gloving provides a significant reduction in the risk of blood exposure to surgical personnel. Indicator systems have the added advantage of preventing the infection of unnoticed injuries, which can occur with glove punctures that are difficult to detect. The aforementioned double‐gloving techniques already exist, and their benefits, compared with single gloving, are known in the field of surgery. In conclusion, double gloving should be recommended for all surgical procedures and should be required for procedures for patients with known infections or for patients who have not yet been tested for infections.