Abstract ID: A26

Abstract Title: Peripheral Nerve Blocks in Heavily Sedated Patients

Poster Type: Either


ABSTRACT BODY

Introduction:
Premedicating patients prior to PNBs is often advised against because it is believed that pain as one of the indicators of intraneural injection may be missed. Recent data indicates that injection pressure can serve as an indicator of intraneural needle placement. This is because high injection pressure (>20 psi) is required to overcome the limited intraneural compliance and initiate intraneural injection. Our hypothesis is that PNBs in deeply sedated patients do not carry a high risk of neurologic complications when injection pressures >15 psi are avoided.

Materials and Methods:
Following IRB approval and informed consent, 221 patients scheduled to receive PNBs for their surgeries were enrolled in the study. All patients were given intravenous sedation with midazolam and alfentanil, titrated to light sleep throughout the block performance (a score of 3 on the sedation-agitation scale - rouses to stimuli). After nerve localization with a current of 0.2 to 0.5 mA (0.1 msec, 2Hz) and single-stimulation technique, 20-45 mL of local anesthetic was injected through 21-22 G Stimuplex (B Braun Medical) needle. Injection pressure was monitored throughout injection using a simple, disposable in-line pressure manometer (BSmart, Macosta, Italy) attached to the syringe (Figure 1).

Injection pressure was kept below 15 psi until the completion of the block. Patients were followed postoperatively through our QA surveillance system and through the routine follow-up with the surgeons.

Results:
221 patients were studied, Table 1. In 206 cases (93%) the block was deemed successful for surgical anesthesia. In 24 patients, initial pressure readings were >15 psi; in these situations, injection was halted, the needle was withdrawn and the nerve re-localized. No patient developed neurologic complication.

Discussion:
Premedication before PNBs is almost always desirable for greater patient acceptance and comfort as well as for additional safety by raising the seizure threshold in case of high plasma level of local anesthetic. Using objective injection pressure monitoring, we have successfully performed a series of PNBs in deeply sedated patients without neurologic complications. Although this study is underpowered to determine the actual safety of this practice, the results suggest that PNBs in premedicated patients can be performed with a low risk of neurologic complications when high injection pressures are avoided through objective monitoring.

1.Anesthesiology 2000;93:1541-4
2.Pain 2000;85:283-6
3.Reg Anesth Pain Med 2004;29(5):417-23
4.Reg Anesth Pain Med 2004;29(3):201-5
5.Crit Care Med 1999;27:1325-29
6.Anesthesiology 2001;95:875-80

ATTACHED FILES



A26_Beklan Inguinal hernia Abstract 5 (TABLE1).DOC



Reg Anesth Pain Med 2004; 29(2):A26