19 Special Features of Peripheral Nerve Blocks
19.1 Advantages of Peripheral Nerve Blocks
According to a meta analysis of Rodgers et al (2000) central neuraxial blocks (CNB) are associated with a reduction in postoperative mortality and morbidity. There are no comparable studies regarding peripheral nerve blocks. However, it can be inferred that peripheral nerve blocks offer advantages in at-risk patients compared with general anesthesia and also compared with neuraxial blocks.
While peripheral blocks are performed quite frequently on the upper limb, they are still not used as frequently for operations on the lower limb. One reason for this may be that parts of both the lumbar and sacral plexuses always have to be anesthetized for a complete block of the lower limb (two injections).
Considerable drops in blood pressure can occur with central neuraxial blocks. The major advantage of peripheral nerve blocks is therefore the lower interference with the circulation. Thus, cardiac arrest was seen significantly less often after peripheral blocks than after spinal anesthesia (Auroy et al 1997). Furthermore, possible complications (infections, hemorrhage, nerve injury) are less serious than the complications of CNB blocks.
While intact coagulation is an absolute requirement for neuraxial blocks, the criteria for peripheral nerve blocks are less strict. Normal coagulation clinically and in the patient′s medical records is usually sufficient for performing a peripheral nerve block (see below).
Under certain circumstances, peripheral blocks are the procedure of choice for surgical anesthesia. In the nonfasting patient, regional anesthesia procedures should be preferred; for the upper limb, only peripheral nerve blocks should be considered.
Many patients with rheumatic diseases have severely limited mouth opening, often combined with extreme deformity of the entire spine. Both general anesthesia and neuraxial blocks are associated with considerable technical difficulties and risks in these patients.
Postoperative nausea and vomiting (PONV) often poses unbearable problems for patients in the perioperative phase, caused for the most part by intra- and postoperative application of opioids, but also by cardiovascular instability resulting from regional blocks in the locality of the spinal cord. Small amounts of remifentanil (e.g., 0.05 µg/kg/min) in addition to peripheral regional anesthesia evidently do not increase a patient′srisk of nausea and vomiting. Peripheral blocks have been shown to significantly reduce the rate of PONV, especially when applied in postoperative pain management (Borgeat et al 2003).
In the outpatient sector, peripheral blocks offer numerous benefits compared to other anesthesia procedures, for example, a patient recovers from surgery more quickly (Hadzic et al 2005).
Thanks to the development of the (single-use) elastomer pump, continuous blocks can now also be performed in an outpatient setting. This means that procedures that could formerly be performed in an outpatient setting to a limited extent only because of expected postoperative pain can now be performed on outpatients due to adequate pain therapy (Ilfeld and Enneking 2005).
In general, continuous regional anesthesia should always be part of a multimodal concept for postoperative pain control (Meier 2005).