Charles W. Buffington

Wearing the Wrong Size Latex Surgical Gloves Impairs Manual Dexterity

Universal precautions mandate that health care workers wear gloves when dealing with patients, often in situations requiring a high level of technical skill. Although it seems obvious that wearing the wrong size gloves could impair or prolong tasks involving manual dexterity, the issue has not been formally studied. We tested the hypothesis that wearing the wrong size gloves impairs manual dexterity. We administered a grooved pegboard test to 20 healthy, paid, volunteer health care workers. The subjects performed the test with bare hands and while wearing their preferred size of latex surgical gloves, gloves that were a full size smaller, and gloves that were a full size larger. Each subject did three runs with each size glove and three runs with bare hands. The time necessary to insert pegs was measured with a stopwatch. Peg insertion time was not affected by wearing preferred size gloves (vs. bare-handed) but was increased 7–10% by gloves that were either too small or too large (both effects: P < 0.05 vs. preferred size; both P < 0.001 vs. bare-handed). The subjects reported that the too-small gloves limited hand motion or hurt their hands, whereas the too-large gloves were clumsy but comfortable. Health care workers should wear gloves that fit properly when doing tasks that require manual dexterity. If the preferred size is unavailable, wearing gloves that are too large seems the best alternative.

Prediction of blood loss during surgery on the lumbar spine with the patient supported prone on the Jackson table.

BACKGROUND CONTEXT To date, many studies have examined the effects of one or several factors on blood loss during lumbar spine surgery. The nature and extent of the operation, patient position, blood pressure, and a variety of factors related to patient size have been touted as predictors of blood loss. PURPOSE To measure multiple factors implicated as determinants of blood loss and develop a multivariable statistical model capable of predicting blood loss. STUDY DESIGN An observational study of patients undergoing lumbar spine surgery in the prone position on the Jackson table. PATIENT SAMPLE A total of 71 healthy adult men and women undergoing lumbar spine surgery in a university hospital setting. OUTCOME MEASURE Blood loss during surgery. METHODS We observed 35 surgeries and recorded demographic and body habitus data on each patient as well as surgical variables, blood pressure, and peripheral venous pressure. We measured bladder pressure intermittently as a surrogate for intra-abdominal pressure. We constructed a statistical model with the results and validated that model in a separate set of 36 subjects. RESULTS The Jackson table supported all our patients regardless of body dimensions without causing an increase in bladder pressure. Blood loss during surgery averaged 1,167±998 mL (mean±1 standard deviation, range 32-3,745). The statistical model was able to account for about 75% of the variability in blood loss using four variables: the number of laminectomies, whether bone was harvested from the iliac crest, experience of the surgeon doing the initial exposure and closure, and distension of the epidural veins. Data on these variables that were collected in the validation study found a multiple correlation coefficient (R(2)) of 0.66 between predicted and observed blood loss. CONCLUSIONS This is the first study to build a successful multivariable predictive model of blood loss during spine surgery. The Jackson table was effective in supporting patients with different body sizes and shapes, thus removing raised intra-abdominal pressure as an important factor.

Hydrodynamics of the spinal epidural space in pigs determined by constant-flow methods.

Background and Objectives: Impressive quantities of fluid can be infused into the epidural space of the spine without causing dramatic or sustained increases in pressure. The epidural space is considered “leaky,” but questions remain about how fluid leaves the epidural space. We used constant-flow infusions of saline to gain insight into the hydrodynamics involved. Methods: We infused saline at a constant rate into the lumbar epidural space of 6 anesthetized pigs while measuring pressure at the adjacent interspace. Three or 4 infusions were performed at different flow rates in each animal. Results: Epidural space pressure in the absence of flow was consistently 2 to 3 mm Hg above right atrial pressure. During each infusion, pressure increased slowly to a steady plateau value between 15 and 70 mm Hg. When flow was stopped, pressure declined exponentially to the starting pressure. The presence of a plateau indicates that fluid leaving the epidural space ends up in a structure with high capacitance. Plateau pressures were linearly related to flow rate in each animal, indicating constant resistance to outflow. The flow-pressure relation showed neither a critical opening pressure nor moderating pressures with increased flow. Conclusions: Fluid leaves the porcine spinal epidural space through channels that are open at baseline rather than being recruited as epidural pressure increases. This behavior is inconsistent with the view that the epidural space behaves like a Starling resistor.

Body position affects manual dexterity.

To evaluate the relationship between posture and psychomotor efficiency, 20 anesthesia providers performed a test requiring manual dexterity and eye-hand coordination while seated, kneeling, and standing bent forward at the waist. Performance on the Grooved Pegboard Test improved 6%–10% (P < 0.005) when subjects were seated compared to kneeling and standing bent at the waist, positions that the subjects rated as more painful and less comfortable than sitting. Sitting improved manual dexterity more in subjects with poor scores than it did in subjects with good performance. This study demonstrates improved manual dexterity in subjects seated in a comfortable position.

Direct connections between the spinal epidural space and the venous circulation in humans.

Background and Objectives: Our previous studies in pigs indicate that direct connections exist between the spinal epidural space and the venous circulation. We wondered if similar connections occur in humans and have extended our investigations to human cadavers awaiting autopsy. Methods: We studied 10 recently dead human bodies. We inserted 2 Tuohy needles into the epidural space of the lower thoracic spine at adjacent interspaces. We infused saline with a constant-flow pump into 1 needle and measured the resulting pressure through the other. Epidural pressure increased to a steady plateau during fluid infusion, and this value was recorded at several flow rates. The pressure decay after flow stopped was also recorded. Then we infused radiopaque contrast, removed the needles, and obtained a computed tomographic scan of the spine from the foramen magnum to the coccyx. Results: Pressure in the epidural space increased to a plateau during saline infusion. Higher flow rates produced higher plateau pressures. Plots of plateau pressure versus infusion rate were linear in all bodies. The slope of the flow-pressure plot gave a steady-state resistance (543 ± 638 mm Hg·s/mL). The time constant of the pressure decay curve allowed calculation of initial capacitance (0.090 ± 0.062 mL/mm Hg). Contrast could be identified in veins around the spinal column in all bodies. Contrast was found most commonly in the deep veins of the neck (7 bodies) and in veins originating in the area of the brachial plexus (7 bodies). Contrast was found less commonly and in smaller amounts in veins draining into the azygous system (5 bodies) and the lumbar veins (5 bodies). No contrast was found in veins in the sacral area. Conclusions: A direct connection between the spinal epidural space and the venous circulation has been demonstrated in human cadavers. The connection is most commonly found in the cervical and upper thoracic spine.

Brand and size matter when choosing a syringe to relieve pressure in a tracheal tube cuff.

We studied the use of an inline syringe as a pressure relief valve for tracheal tube cuffs during exposure to nitrous oxide to see if the technique works. Bench testing was done to determine the stick and slip characteristics of syringes of different brands and sizes. Cuffs were inflated with 20 mL of air, producing a cuff pressure of 100–120 mm Hg. Then the plunger of the syringe was allowed to passively rebound to a steady pressure at which the plunger stopped (“stick pressure”). After several minutes, pressure in the syringe was forcibly increased with a second syringe until the plunger started moving again (“slip pressure”). Stick pressure varied from 18 to 82 mm Hg depending on the brand and size of syringe used. Slip pressures exceeded stick pressures by 20–120 mm Hg. Cuff pressure increased in a linear fashion during nitrous oxide exposure, and no syringe demonstrated automatic pressure reduction. We conclude that a syringe attached to the pilot balloon connector can be used to control tracheal tube cuff pressure during nitrous oxide anesthesia. However, not all syringes are suitable for this purpose: large syringes are better than small syringes, and the Terumo brand is more suitable than BD or Monoject. The system does not work automatically, and intermittent compression of the syringe plunger to overcome static friction is required to avoid overdistension

Effects of intracoronary calcium chloride on the postischemic heart in pigs.

Whether calcium chloride (CaCl2) should be used to reverse myocardial dysfunction during cardiac operations remains a controversial issue. Calcium chloride may reduce, rather than increase, myocardial contractility and may produce exaggerated vasoconstriction in postischemic vessels in which the endothelium has been damaged. These possibilities were investigated in an open-chest porcine model that allowed control of systemic hemodynamics. Incremental doses of CaCl2 (1, 3, and 10 mg/min) were infused directly into a coronary artery before and after 10 or 15 minutes of ischemia followed by 15 minutes of reperfusion. Calcium chloride increased regional contraction, coronary blood flow, and oxygen consumption before ischemia, whereas oxygen and lactate extraction were unchanged. After ischemia and reperfusion, contraction was impaired and lactate extraction was reduced, but a similar response to CaCl2 was observed. Contraction returned to baseline values promptly after CaCl2. Thus, CaCl2 exerts a positive inotropic effect both in normal and in postischemic myocardium. Calcium chloride does not cause direct coronary constriction nor does it worsen myocardial stunning after a short period of normothermic myocardial ischemia.

Wearing Ambidextrous Vinyl Gloves Does Not Impair Manual Dexterity

Universal precautions mandate that health care workers wear gloves to prevent the unintended spread of bloodborne pathogens. Gloves may affect manual dexterity, generally delaying task completion. Our previous study showed that wearing the wrong size latex surgical glove degraded manual dexterity. The use of non-sterile and non-latex gloves may limit certain risks and be more cost-effective. However, such gloves may produce different results. We hypothesized that ambidextrous vinyl examination gloves would degrade manual dexterity compared with bare hands. We studied 20 random subjects from a medical environment. Subjects performed a standard battery of Grooved Pegboard tasks while bare-handed, wearing ambidextrous non-sterile vinyl gloves that were their preferred size, a size too small, and a size too large. The order was randomized with a Latin Square design to minimize the effects of time, boredom, and fatigue on the subjects. Subjects were also invited to comment on the fit of different size gloves. Wearing vinyl gloves of both the preferred size and a size up or down failed to affect manual dexterity vs. bare hands on time to insert pegs, and pegs dropped during insertion or removal. In contrast, the time to remove pegs was reduced by wearing preferred size vinyl gloves compared with performing the task with bare hands (P < 0.05). Subjects reported a generally poor fit in all sizes. Vinyl gloves that were too small caused significant hand discomfort. Vinyl gloves surprisingly do not degrade manual dexterity even when worn in ill-fitting sizes. Wearing a preferred size vinyl glove vs. bare hands may improve dexterity in selected tasks. Choosing a comfortable, large size seems the best strategy when the preferred size is unavailable. Thinner vinyl gloves may improve grip and may not degrade touch as much as latex surgical gloves and may thus represent a reasonable choice for selected tasks.

Regional Contraction Improves, then Declines After Reperfusion of Ischemic Myocardium in the Dog

Myocardial ischemia occurs during cardiac surgery and coronary artery angiopiasty. If ischemia is short‐term or the heart is protected, cellular necrosis can be avoided. Nevertheless, myocardial stunning occurs and can reduce cardiac performance in the hours after ischemia. Such stunning is preceded by a short period of normal or above normal contraction immediately after reperfusion. The time course of this phenomenon was investigated in six anesthetized dogs subjected to a 10‐minute total coronary occlusion. Regional contraction was measured in the ischemic zone and In a remote zone of the heart with a sonomicrometer. Remote zone contraction increased during ischemia, returned toward baseline values after reperfusion, and was stable for the next hour, indicating little effect of time on the experimental preparation. In contrast, ischemic zone contraction was abolished by 10 minutes of coronary occlusion, returned to baseline or greater levels within 1 to 3 minutes following release of the occlusion, then gradually declined over 10 to 20 minutes to a level about 40% below baseline values, indicating myocardial stunning. These findings support the notion that a honeymoon period of normal or above normal function exists during early reperfusion, and that stunning manifests later. This reperfusion “honeymoon” may create a false sense of security.