Imagine you are sleeping soundly in your warm bed when a tingling in your arm awakens you. In a haze of sleep, you reposition your arm, roll over, and fall back asleep. The tingling, the result of compression of a nerve or blood vessel, caused you to change positions to decrease pressure, maintain blood flow, stop pain, and avoid injury. Patients undergoing surgical procedures under general, regional, or sedation anesthesia cannot perform this function and are susceptible to peripheral nerve injuries. Imagine the reaction of a patient awakening from surgery only to find a new, disabling injury, which might have been prevented. The circulating nurse, with guidance from the anesthesia provider and the surgeon, is responsible for positioning the surgical patient in a manner that prevents injury.^1,2 This module aims to add to the OR nurse’s body of knowledge about lower extremity nerve injury prevention.

The lower extremity nerves that are most susceptible to injury are the lumbosacral plexus, the femoral nerve, the common peroneal nerve, and the sciatic nerve. Understanding where these nerves are located is the first step in preventing their injury. The primary means of preventing these injuries is to avoid stretch and pressure on these nerves.

The lumbosacral plexus is made of nerves from the ventral rami of T12 to L4 and branches to the femoral, obturator, ilioinguinal, iliohypogastric, genitofemoral, and lateral femoralcutaneous nerves. The sacral plexus is made up of nerves from the ventral rami of the S1 to S3 spinal nerves and forms the sciatic, pudendal, posterior femoral cutaneous, and muscular branches to the pelvis. Many of the injuries to this plexus are a result of trauma during total hip arthroplasty.³ The other most common injuries of this plexus are a result of suture placement, compression, and ischemia.³

The femoral nerve is formed within the psoas major muscle by posterior divisions of the second, third, and fourth lumbar nerves. It emerges from the lateral border of the psoas muscle to descend in the groove between the psoas and iliacus major muscles and enters the thigh by passing beneath the inguinal ligament lateral to the femoral artery and divides into multiple branches.  This nerve serves the anterior muscles and skin of the thigh from the inguinal ligament to the knee.³

The femoral nerve can be injured by compression with self-retaining retractors during abdominal hysterectomies; pressure and stretch in lithotomy position with excessive hip abduction and external rotation; inadvertent suturing; aortic cross-clamp-induced ischemia; and high tourniquet pressure compressing the nerve.⁴

The sciatic nerve is made of two divisions that travel in the same sheath. These divisions are the tibial and peroneal nerves. The tibial nerve is made up of the anterior branches of L4 to S3 and the peroneal nerve is made up of the posterior branches of L4 to S3. This sheath leaves the pelvis through the greater sciatic foramen and descends between the ischial tuberosity and the greater trochanter down the posterior thigh, where it divides into the tibial and common peroneal nerves at the level of the knee.³

The sciatic nerve can be injured by improper surgical positioning. This injury occurs when the nerve is put under tension in the lithotomy position when the hip is flexed and knee straightened or when the flexed hip and flexed knee are excessively rotated. Ischemia during cardiac surgery can also cause injury to the sciatic nerve, especially in patients with existing vascular disease.

Of the branches of the sciatic nerve, injury occurs most often in the common peroneal nerve <www.nlm.nih.gov/medlineplus/ency/article/000791.htm>, usually the result of positioning during surgery. The common peroneal nerve is vulnerable to direct pressure at the fibular neck when surgery is performed in the lateral decubitus position or in lithotomy position with inadequate padding between the fibular neck and a stirrup or leg strap.⁴

The five mechanisms

There are five mechanisms for perioperative peripheral nerve injuries: stretch, compression, generalized ischemia, metabolic derangement, and surgical section.⁵ Stretch and compression can be avoided by proper positioning. Stretch can be prevented by positioning the patient while he or she is awake, before being returned to a position that facilitates induction of anesthesia. If a position is uncomfortable while the patient is awake, it can cause injury when maintained for a long period of time under anesthesia. Nerve damage can occur with just a 10% to 15% stretch of a nerve fiber.⁵ A similar rule of thumb applies for compression injuries. If the patient experiences discomfort while awake, injury can occur if the nerve(s) are compressed for extended time periods. Proper padding of boney areas, avoiding excessive length of time that a tourniquet is applied, and preventing OR personnel from leaning on the patient will help avoid pressure injuries.⁵

A 2001 study found that lithotomy position is associated with changes in intracompartmental pressure in the lower extremities, depending on the method used to support the legs.⁶ If pressure is placed on the knee or calf to support the lower extremity (using stirrups and a knee support device), it can result in placing pressure on the nerves within the compartment and can cause nerve injury. Elevating the lower extremity using a sling support at the ankle decreases intracompartmental pressure. Constant external compression, like that applied by antithrombosis stockings, does not decrease the intracompartmental pressure in the lower extremities. The use of intermittent external compression (e.g., pneumatic compression stockings), however, significantly reduces this pressure increase and decreases the likelihood of nerve injury from increased intracompartmental pressure.⁶

Metabolic diseases, such as diabetes, pernicious anemia, alcoholism, arteriosclerosis, drug use, heavy metal exposure, and polio can also cause neuropathies <www.ninds.nih.gov/disorders/peripheralneuropathy/detail_peripheralneuropathy.htm>. It is important to assess these patients and document any preexisting neuropathies to avoid legal action for preexisting conditions. Tobacco users are more likely to suffer nerve injuries because of the vasoconstrictive effects of nicotine, so care must be taken in positioning these patients as well as patients with metabolic diseases. Extremes of body weight and length of surgery also increase the risk of lower extremity nerve injury, especially when the patient undergoes surgery in the lithotomy position.¹

Early neurologic consultation with motor neuropathies is also recommended to prevent nerve injury <www.asahq.org/publicationsAndServices/PractAdvis.pdf>.^1,7

Electromyographic studies — electrical recordings of muscle activity that aid in the diagnosis of neuromuscular disease — can be helpful in determining the location of the lesion and may provide information on the potential reversibility of any nerve deficit. Sensory neuropathies, in contrast, are often transient and initial treatment may be all that is needed.⁵ It’s important to note that de-generation potentials are unlikely to appear until three weeks after injury. So immediately after surgery, degeneration potentials can indicate preexisting injury.⁷ In any case, perioperative personnel seldom are able to follow a patient in the long term, and so neurologic evaluation helps provide continuity of care.

Grades 1 to 3

Peripheral nerve injuries can be graded based on the degree of injury, with Grade 1 being the least severe and Grade 3 the most severe. This grading system approximates the prognosis for each grade of injury.⁸ Generally, the higher the grade, the less favorable the prognosis.

A Grade 1 injury is a response to blunt force or compression where there is a temporary dysfunction but only slight evidence of demyelinization without nerve degeneration. This occurs, for example, when crossing the legs for too long a time or in motor paralysis that follows excessive pressure from a pneumatic tourniquet. Sensation remains intact for the affected area.

In a Grade 2 injury, destruction of the nerve axons occurs, including the myelin sheath, but without damage to the supporting matrix. In this kind of injury, symptoms occur distal to the injury, but function can eventually be restored through nerve regeneration. This kind of injury is caused by either interrupted endoneural blood supply or hypoxia.⁸

A crushed, avulsed, or severed nerve defines a Grade 3 nerve injury. There is a loss of function in the area served by the nerve. Unless the injury is identified and the nerve can be excised and the severed ends of the nerves closely approximated, there is usually little or no return of function. In addition to loss of function, painful neuromas can result from disorganized regeneration of the axons at the fibrous, endoneural scar.⁸

Regional anesthesia has been undeservedly notorious for causing nerve damage. Neurologic complications may coincide temporally with but not be caused by a regional anesthetic. In one study of 4,185 patients receiving thoracic epidurals, 24 patients experienced transient neurologic complications. Fourteen of these patients had peroneal nerve palsy and all 14 had been operated on in the lithotomy position.⁷

Another area of concern is transient neurologic symptoms. These are symptoms with pain or dysthesia in the gluteal area or legs after resolution of a spinal anesthetic but within 24 hours of surgery. Sixteen percent of patients receiving lidocaine in their spinal anesthetic suffered transient neurologic symptoms, and no patients receiving bupivicaine suffered transient neurologic symptoms. This phenomenon seems to be explained by the stretch of the lumbosacral nerve roots in the lithotomy position combined with the lidocaine causing the temporary symptoms.⁷

Nerve injuries can be caused by needle trauma, intraneural injection, local anesthetic toxicity, and local anesthetic additives. Each of these causes is more under the control of the anesthesia provider involved in the case, but the OR nurse should be aware that patient complaints of paresthesia during block placement, high-concentration local anesthetics, and the preservative-containing solutions (with sodium bisulfate, chlorobutanol, for example) make nerve injury from regional and peripheral nerve blocks more likely.

Documentation serves as a record of what steps were taken in a patient’s care and when the need to examine that care arises. Careful and detailed documentation can lead to proof of or lack of liability in case of patient injury. However, documentation serves another important purpose: to remind the provider of steps that need to be taken in a patient’s care.

Documentation of nursing activities not only provides a record of the steps taken to safeguard the patient during positioning and outcomes of those steps, it also focuses the perioperative nurse’s attention on specific aspects of patient positioning to prevent injury to the lower extremities and provides information that can be used to refine patient positioning in the future.^9,10 (See sidebar for aspects to include in documentation.)

Six practices

The Association of periOperative Registered Nurses (AORN) recommends six practices with regard to positioning the patient in the perioperative setting.¹⁰ Outcomes of these guidelines include optimal exposure of the surgical site, proper access for airway management, proper ventilation, proper monitoring access for anesthesia personnel, physiologic safety of the patient, and maintenance of patient dignity by controlling unnecessary exposure. The six practices are —

• Preoperative assessment for positioning needs should be made before transferring the patient to the procedure bed. The preoperative interview should include questions to determine patient tolerance to the planned position. The OR nurse should assess both patient and intraoperative factors. Patient factors include age, body build, skin condition, nutritional status, preexisting conditions, and mobility limits. Intraoperative factors include anesthetic concerns, length of the planned procedure, and position required for the planned procedure.¹⁰
• Positioning devices should be readily available, clean, and in proper working order before placing the patient on the procedure bed. Properly functioning equipment and devices contribute to patient safety and help provide adequate exposure of the surgical site. Selection criteria for positioning equipment includes its availability in a variety of sizes and shapes; durability; ability to maintain normal capillary interference pressure
  (32 mmHg or less); resistance to moisture and microorganisms; radiolucency; fire resistance; nonallergenic properties; ease of use; cleaning; storage, and retrieval; and cost-effectiveness.¹⁰
• The perioperative nurse should actively participate in monitoring patient body alignment and tissue integrity based on sound physiologic principles. Use of the proper number of personnel for patient positioning decreases the risk of positioning injury. Catheters, tubes, and cannulas can be accidentally pulled out if too few personnel are used. Maintaining proper body alignment and supporting the extremities also decreases the chance of injury during and due to positioning.¹⁰
• After positioning, the perioperative nurse should evaluate the patient’s body alignment and tissue integrity. This evaluation should include but not be limited to the respiratory, circulatory, neurologic, musculoskeletal, and integumentary systems. Unusual findings in any of these areas can lead to lower extremity nerve injury if not corrected.¹⁰
• Documentation of surgical positioning should be consistent with AORN’s “Recommended practices for documentation of perioperative nursing care.” This documentation includes the nursing assessments, interventions and treatments, and evaluations of the quality of the care delivered. Documentation of care activities provides a picture of the care delivered and its outcomes.¹⁰
• Policies and procedures related to positioning should be developed and reviewed annually, revised as necessary, and be available in the practice setting. These policies and procedure should include but not be limited to: assessment and evaluation criteria and documentation; anatomic and physiologic considerations; safety interventions; documentation of patient position and/or repositioning, positioning devices, and personnel positioning the patient; and positioning device care and maintenance.¹⁰

The role of tourniquets

Tourniquets are often used in lower extremity surgeries to reduce blood loss and to increase visibility for the operating practitioner. This is particularly true for orthopedic procedures. Before the tourniquet is inflated, the operative extremity is exsanguinated by wrapping it from the distal end and working proximally with an eschmark. The tourniquet pressure needs to be 50 mmHg above the patient’s systolic blood pressure to ensure a blood-free field. The inflation and deflation times for the tourniquet and the tourniquet pressure are recorded on the anesthesia record.¹¹

The accepted time for tourniquet inflation is two hours. The anesthetist or other operating room personnel need to notify the operating practitioner when the tourniquet has been inflated for one hour and when it has been inflated for two hours. If the procedure takes longer than two hours, the tourniquet is usually deflated for 15 minutes, the extremity reexsanguinated, and the tourniquet reinflated.

Tourniquets stop blood flow to the operative extremity. This lack of blood flow stops delivery of oxygen and nutrients, as well as the removal of carbon dioxide and other metabolites. This lack of transport can damage the nerve cells serving the extremity. Improper tourniquet placement can, by itself, also cause lower extremity nerve injury. If a tourniquet compresses a nerve between the tourniquet edge and a firm surface (bone), the inflation pressure can cause a compression injury to the nerve. The nurse placing the tourniquet must pay careful attention to its location.

The lumbosacral plexus, femoral nerve, common peroneal nerve, and sciatic nerve are susceptible to injury in the OR. Stretch, compression, generalized ischemia, metabolic derangement (such as diabetes, pernicious anemia, alcoholism, arteriosclerosis, drug use, heavy metal exposure, and polio), and surgical section are the primary mechanisms of injury for these nerves. Knowledge of proper follow-up recommendations, grades of injury, and likely outcomes is useful for the perioperative nurse in dealing with patients with a lower extremity nerve injury. Careful positioning, along with knowledge of anatomy and careful documentation, can greatly reduce the incidence of lower extremity nerve injury in the OR.

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