Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1999
No risk of metal toxicity in combined spinal-epidural anesthesia.
Using the single level needle-through-needle technique for combined spinal-epidural anesthesia (CSE) may introduce very fine metal particles abraded by the spinal needle from the inner ground edge of the Tuohy needle into the patient. Either the local anesthetic administered epidurally or the peridural catheter may also pass intrathecally through the hole in the dura made by the spinal needle. To examine these concerns, the needle-through-needle technique was simulated in an in vitro model (18-gauge Tuohy needle; 27- or 29-gauge Quincke needle). The presence of abraded metal particles was identified by atomic absorption spectrography (AAS). The needles were then examined under an electron microscope. Metal particles could not be identified by using AAS in the needle-through-needle technique after normal clinical use, nor could traces of use be revealed by using an electron microscope to examine the Tuohy needle. With intentionally rough handling and caudal orientation of the spinal needle tip, minimal scratches could be seen by using an electron microscope, but there were no metal particles detected by AAS. In an anatomical preparation, the possible passage of the epidural catheter anesthetic through the dural puncture hole into the cerebrospinal fluid compartment was investigated endoscopically. Neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy. We conclude that the needle-through-needle-technique is an acceptable way of performing CSE anesthesia. Endangering the patient by an unintentionally intrathecal misplacement of the epidural catheter seems to be very unlikely based on our in vitro model if small spinal needles (27- or 29-gauge) are used. ⋯ Atomic absorption spectrography shows no contamination of the intrathecal compartment by abraded metal particles from the Tuohy needle by combined spinal-epidural anesthesia with the needle-through-needle technique. In vitro, neither passage of dyed epidural local anesthetic nor penetration of the epidural catheter into the cerebrospinal fluid compartment could be demonstrated by endoscopy.
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Anesthesia and analgesia · Feb 1999
The risk of persistent paresthesia is not increased with repeated axillary block.
Neurologic deficits are noted on physical examination in approximately 0.2%-19% of patients after regional anesthetic techniques. Laboratory and clinical studies suggest that a subclinical neuropathy occurs much more often. Performing a regional anesthetic technique during this period may result in additional nerve trauma. We evaluated the frequency of neurologic complications in patients undergoing repeated axillary block. A total of 1614 blocks were performed on 607 patients. The median number of blocks per patient was two (range 2-10 blocks). The median interval between blocks was 12.6 wk, including 188 (31%) patients who received multiple blocks within 1 wk. Sixty-two neurologic complications occurred in 51 patients for an overall frequency of 8.4%. Of the 62 nerve injuries, 7 (11.3%) were related to the anesthetic technique; the remaining 55 (88.7%) were a result of the surgical procedure. Patient age and gender, the presence of preexisting neurologic conditions, a surgical procedure to a nerve, and total number of blocks did not increase the risk of neurologic complications. No regional anesthetic technique risk factors, including elicitation of a paresthesia, selection of local anesthetic, or addition of epinephrine, were identified. The success rate was higher with the paresthesia technique than with nerve stimulator technique or transarterial injection, and with use of mepivacaine versus bupivacaine. We conclude that the frequency of neurologic complications in patients undergoing repeated axillary block is similar to that in patients receiving a single regional technique. These patients are not likely to be at increased risk of neurologic complications. ⋯ The risk of neurologic complications was not increased in patients who underwent multiple axillary blocks, even within a 1-wk interval. No risk factors for anesthetic-related complications were identified. However, block success rate was increased with the paresthesia technique and the injection of mepivacaine versus bupivacaine.
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Anesthesia and analgesia · Feb 1999
Predicting the size of a double-lumen endobronchial tube using computed tomographic scan measurements of the left main bronchus diameter.
We investigated the use of chest computer tomographic (CT) scan measurement of the left mainstem bronchial diameter to predict the correct left-sided double-lumen endobronchial tube (DLT) size in Asian patients who may require smaller DLT sizes. Fifty consecutive Asian adults aged 17-80 yr with preoperative chest CT scans undergoing elective thoracic surgery were entered into the study. The measurements of the left main bronchus diameter were made by using the electronic calipers of the spiral scanner to the nearest millimeter. The sizes of DLT selected were 32F, 35F, 37F, 39F, and 41F for left main bronchus diameters of <10 mm, 10 mm, 11 mm, 12 mm, and >12 mm, respectively. All DLT placements were confirmed and positioned by using fiberoptic bronchoscopy. The tracheas of all patients were successfully intubated with the predicted DLT sizes. Thirty-four patients (68%) were predicted to require smaller DLTs (37F or smaller). Six patients were correctly predicted to receive 32F DLTs. Twelve patients (24%) received an oversized DLT, but none received an undersized DLT. The overall positive predictive value for the male and female patients was 84.4% and 61.1%, respectively. Our study showed that CT scan measurements of the diameter of the left bronchus were especially useful in choosing smaller DLTs. ⋯ We used computer tomographic scans to measure the diameter of the left mainstem bronchus, then selected the size of the left-sided double-lumen endobronchial tube (DLT) accordingly. We found that we could predict the sizes of the DLT fairly accurately, especially the smaller DLTs.