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May 1997
The direction of the Whitacre needle aperture affects the extent and duration of isobaric spinal anesthesia.
Urmey WF, Stanton J, Bassin P, Sharrock NE;Anesth Analg 1997:84:337-41.
[ see abstract below ]
Isobaric spinals are commonly used for ambulatory anesthesia, and the Whitacre needle has become popular since it is associated with a lower incidence of postdural puncture headache. One concern, however, is the in-facility recovery time needed. This study assessed the effect of cephalad versus caudad direction of the 27 ga Whitacre needle aperture on the extent and duration of spinal anesthesia.
All patients received 60 mg 2% plain lidocaine via a midline approach for knee arthroscopic surgery, and sedation was limited to midazolam. The authors report that the group who received spinal anesthesia with a cephalad-directed needle had a higher sensory level [median T3 vs T7]. There was no difference in vasoactive drugs needed. They also had significantly shorter duration of lumbar sensory anesthesia [149 vs 178 min] and motor blockade [118 vs 150 min], resulting in significantly shorter times to spontaneous urination and to discharge [211 vs 243 min].
It should be noted that 3.5 hours from injection of the spinal to the time to discharge were observed for these procedures averaging 44 min operating time.
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ABSTRACT
The use of Whitacre spinal needles results in directional flow out of the needle aperture, diverting local anesthetic from the longitudinal axis of the needle. Thus, a change in orientation of the needle aperture would be expected to result in a different local anesthetic distribution in the subarachnoid space. We studied 40 outpatients undergoing elective knee arthroscopy under spinal anesthesia with 60 mg pain lidocaine 2% in a prospective, double-blind manner.
Patients were randomly assigned to either Group I (needle aperture oriented in a cephalad direction throughout intrathecal injection) or Group II (aperture directed caudally). Onset and offset of sensory and motor block were analyzed at frequent intervals. Times to completion of ambulatory milestones, including discharge, were recorded. Group I was characterized by a higher sensory level (T 3.4 +/- 1.3 vs T 6.6 +/- 2.8, P less than 0.001).
Group I had significantly shorter duration of lumbar sensory anesthesia (149.2 +/- 30.6 min vs 177.8 +/- 23.5 min vs 150.0 +/- 22.8 min, P less than 0.001). Mean time to outpatient discharge was approximately 32 min shorter in Group I. The orientation of the Whitacre needle aperture exerts a major influence on sensory level, as well as the duration of isobaric lidocaine spinal anesthesia.
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