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The Effects of Handed Bias of Physicians and the Laterality of Recumbent Position of Patients on the Success Rate of Lumbar Puncture.

To JNA Readers: Lumbar puncture (LP) is a common procedure performed in medicine. In this procedure, the lateral recumbent position may be preferred by physicians more than the sitting position. In the lateral recumbent position, patients may face toward the left or the right; however, during LP, for reasons, patients sometimes cannot face the side as required by physicians. We designed this study to test the relationship between the handed bias of physicians and the patient’s position to the success rate of LP. Three hundred patients who had undergone head surgeries and developed a fever (>37.51C for >24h) after operations were enrolled in group R. This group was managed by a righthanded neurosurgeon, with >5 years of LP experience (>700 successful cases). Group L contained another 300 patients who were about to take spinal anesthesia, and patients in this group were managed by a left-handed anesthetist, with >5 years of LP experience (>700 succeed cases). We enrolled male and female patients (aged between 18 and 40y). Pregnant women and patients who had lumbar spine disease or spine trauma were excluded. Patients in each group were randomized to face the left or the right (150 for each). The free flow of cerebrospinal fluid upon first attempt was considered to be evidence of a successful LP. No significant differences were noted in ages, sex, height, and weight between the 2 groups (Table 1). Total success rates of LP showed no significant differences between the 2 groups (278 of 300 and 274 of 300, P=0.547, Fisher exact test, P=0.652). In group L, the success rate of the right lateral recumbent position (145 of 150) was significantly higher than that of the left (133 of 150) (P=0.008, Fisher exact test, P=0.013). In group R, the left lateral recumbent position (143 of 150) showed a statistically higher success rate than the right (131 of 150) (P=0.014, Fisher exact test, P=0.022). Several factors were considered to determine the success of LP, such as older age, the patients’ position, and spinal anatomic landmarks of spinal distance. We found that both the laterality of recumbent position of patients and the handed bias of physicians affected the success of LP. During LP, the needle is inserted horizontally into the skin and parallel to the floor in an interspace between adjacent spinous processes and laminae.3 When the patient was in the left lateral recumbent position, the righthanded physician found it easier to insert the needle as required, whereas the left-handed physician had more difficulty. For in this position, our left-handed physician had to move his bias hand greater, even his body caudad, to maintain the needle parallel to the interspace between adjacent spinous processes and laminae than did a right-handed physician. In addition, a right-handed physician will face the same difficulty when the patient is in the right lateral recumbent position. These actions may contribute to the decrease in success rate of LP. However, our study was limited by the fact that only 2 physicians participated, and therefore the hypothesis needs to be tested with more physicians participating. In this limited study based on the results found with a right-handed and left-handed physician, the success rate of LP depended on the position of the patient in the left (right)-lateral recumbent position for the right (left)handed physician.