Equipment and Patient Monitoring In Regional Anesthesia
Peripheral nerve blocks can be performed in a separate block-placement area or in the operating room. Regardless of where the actual procedures are performed, adequate space, equipment, and monitoring are imperative to ensure time-efficient care of the patient undergoing nerve block procedures. One of the key issues for successful implementation of nerve block is that supplies, drugs, and other equipment for the block procedure must be readily available in the room and prepared at the bedside. The physical size of the block room should allow for enough room for the proper monitoring, emergency access, and resuscitation of the patients. At the very minimum, proper lighting, oxygen administration, and emergency airway management with positive-pressure ventilation and suction must be available at all times.
Adverse effects and complications of peripheral nerve blocks are relatively rare. However, when they do occur, immediate and astute intervention is necessary to prevent severe complications. The block-placement area must be equipped with a source of oxygen, suction apparatus, and equipment for airway management and positive-pressure ventilation.
All drugs should be neatly organized in an immediately accessible drawer and checked on a daily basis for availability and expiration date. Emergency drugs in our practice are stored in a designated drawer in the nerve block carts along with the rest of the nerve block equipment. This way, they are immediately available throughout the nerve block procedure
Suggested Emergency Drugs RequiredDuring Nerve Block Procedures
| Drug | Suggested dose (70-kg adult) |
| Atropine | 0.2mg to 0.4mg IV increments |
| Ephedrine | 5mg to 10mg IV |
| Phenylephrine | 50µg to 200µg IV |
| Epinephrine | 10µg to 100µg IV |
| Midazolam | 2.0mg to 10mg IV |
| Propofol* | 30mg - 200mg IV |
| Muscle relaxant (succinycholine or mivacurium) | Succinycholine: 20-80mg IV |
* A short-acting barbiturate (e.g., thiopental, brevital) can be used instead of propofol, however, this requires dilution of the drug at the time when its prompt administration is of the utmost importance. In addition, the hypnotic and sedative effects of a barbiturate may be longer-lived than those of propofol. These drugs also require more intensive monitoring and airway management.
To perform successful nerve block anesthesia, appropriate equipment should be available, including needles, syringes, and the ancillary equipment necessary for the block. A needle of appropriate size should be chosen for each and every block technique to optimize precision and needle control and decrease the risk of complications. A needle that is too short will obviously not reach its targeted depth, whereas a needle of excessive length is much more difficult to control during advancement. In addition, excessively long needles tend to be inserted too deep and carry a higher risk of serious complications. The recommendations for the needle length provided in this chapter are based on our practice and should be regarded as general recommendations only.
| BLOCK TECHNIQUE | RECOMMENDED NEEDLE LENGTH |
| Cervical plexus block | 50 mm (2 in) |
| Interscalene brachial plexus block | 25 mm (1 in) to 50 mm (2 in) |
| Infraclavicular brachial plexus block | 100 mm (4 in) |
| Axillary brachial plexus block | 25 (1 in) to 50 mm (2 in) |
| Thoracic paraverterbral block | 90 mm (3.5 in - 4 in) |
| Lumbar paravertebral | 100 mm (4 in) |
| Lumbar plexus block | 100 mm (4 in) |
| Sciatic block posterior approach | 100 mm (4 in) |
| Sciatic block anterior approach | 150 mm (6 in) |
| Femoral block | 50 mm (2 in) |
| Popliteal block posterior approach | 50 mm (2 in) |
| Popliteal block lateral approach | 100 mm (4 in) |
Nerve injuries associated with peripheral nerve blocks occur due to three main factors. The first is direct injury of the nerve by the advancing needle. A second factor is injection of local anesthetic into the nerve or nerve sheath under high pressure (with resultant mechanical neural damage or ischemia of the nerve). Finally, injury can be caused by the combination of these factors, with possibly contributing toxic effects of the local anesthetic or its preservative. To decrease the risk of needle related injuries during nerve blockade, needles with short, blunt bevels are suggested by most expert anesthesiologists. Short-bevel needles are much less likely to penetrate nerves during needle advancement than the long (cutting) bevel needles.
To avoid tissue trauma and undue discomfort, it is important to use a relatively small needle diameter. The limitations of the small diameter designs include the difficulties in controlling the needle path due to bending of the needle, and the ability to inject local anesthetics and aspirate blood easily. In general, a 22-gauge needle is perhaps the smallest needle diameter suitable for major conduction blocks. With longer needles, the needle diameter must be increased (e.g., 21 gauge) to prevent bending of the needle alongside its shaft and retain control over the needle insertion path. On the other hand, needles of smaller internal diameter (e.g., 25-26 gauge) can be used for superficial and field blocks. It should be kept in mind that the high internal resistance of these needles during block injection makes it difficult to detect high pressures during injection, such as would occur in case of an intraneuronal injection. The future designs of nerve block needles may incorporate some means of pressure monitoring during injection to avoid inadvertent injection into the nerve itself.
Extension tubing attached to the needle is extremely useful for achieving proper needle stabilization. It often is included in the needle block kits with most currently marketed needle designs. Extension tubing also allows for an aspiration test for intravascular needle placement as well as a syringe change without moving the needle from its intended position.
When continuous infusion is planned, a wide variety of special needle designs with larger diameters, catheters, and infusion pumps are also available. Some designs incorporate styleted catheters for increased ease and control of insertion or the ability to attach the nerve stimulator to a built-in lead to stimulate nerves before securing the catheter.
Similarly, a number of different infusion pumps and systems have been recently introduced to allow continuation of infusion both for inpatients and outpatients. These systems can be either mechanical, spring or elastic balloon-driven or of an electric pump design.
The vast majority of peripheral nerve block procedures go smoothly and without any complications. However, the risk of an inadvertent intravascular injection or rapid absorption or channeling of local anesthetic into the systemic circulation with the consequent toxicity of local anesthetic is always present. For this reason, every patient receiving a major conduction nerve block should receive an intravenous infusion line and be adequately monitored to allow for timely detection of systemic toxicity of local anesthetic and immediate vascular access for its treatment.
The monitoring of patients undergoing major conduction blocks should consist of baseline level of consciousness, pulse oximetry, vital signs (blood pressure and heart rate), and ECG. Respiratory rate must also be monitored throughout the block procedure. After completion of the block procedure, all patients receiving larger doses of local anesthetic for major conduction or plexus blocks are routinely monitored for signs of local anesthetic toxicity for 30 minutes after block placement. Although a toxic reaction occurs during or immediately on injection of local anesthetic in almost all instances, the peak serum levels of local anesthetic typically occur 20 minutes following the injection.
Intraoperative monitoring of patients undergoing surgery under regional anesthesia is identical to that of patients having general anesthesia and consists of monitoring of arterial blood pressure, heart rate, respiratory rate, and continuous ECG monitoring. In minimally sedated and conversing patients, measurements of his or her temperature are not necessary.
Medical documentation pertaining to induction and maintenance of general anesthesia has been standardized in most countries. Such documentation not only collects the physiologic data, such as arterial blood pressure, heart rate, and oxygenation, but also the details of various procedures, such as endotracheal intubation, airway examination, laryngoscopy grades, and so forth. Similarly, documentation of neuraxial anesthesia procedures routinely includes comments on the level of the blockade, sterility precautions, choice of equipment and technique, presence or absence of CSF, blood or paresthesia during needle placement, and injection of local anesthetic. Thus, it is truly puzzling that although peripheral nerve blocks have the same potential for clinical applications as well as medico-legal connotations, at present, there are no standard documenting procedures.
The lack of such standardized documentation practice with peripheral nerve blocks has a number of drawbacks because it makes retrospective analyses, whether for the purpose of research, quality assurance, or medicolegal issues, almost impossible.
At the New York School of Regional Anesthesia, we use a nerve block documentation procedure that allows an easy and reasonably accurate retrospective review of a peripheral nerve block procedure. This documentation procedure is based on a computerized, record-keeping system and consists of the description of the type of block, sterility procedures, equipment, and some other relevant details:
- Nerve block procedure
- Approach used
- Premedication
- Skin preparation
- Equipment used (needle/nerve stimulator)
- Number of attempts
- Type of response obtained on nerve stimulation
- Current (mA) accepted
- Local anesthetic (type, concentration, additives, volume)
- Absence of abnormal pressure on injection
- Signs of block onset
Comments: Although not exhaustive, this documentation allows for a reasonably accurate review of the periblock events that may have lead to a failure or any other problems. In addition, such documentation helps trainees develop a consistent, organized approach to nerve blockade, which is a prerequisite for a successful, objective, and more scientific approach to practice of peripheral nerve blocks.
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