The Case

A 36-year-old woman with class 2 obesity but no chronic illnesses required laparoscopic hysterectomy, which was difficult and prolonged, lasting about three hours. The operation was performed in the lithotomy position, with a steep head down (Trendelenburg) position for part of the operation. Intermittent pneumatic compression devices were placed on both calves to prevent venous thrombosis, but placement was difficult because her legs were large and muscular. On awakening from general anesthesia, the patient complained of severe pain in the right leg. After examining her, the gynecologist made a presumptive diagnosis of deep vein thrombosis and put her on subcutaneous dalteparin at therapeutic dosing, to start later that evening if no bleeding. She was given acetaminophen and oral morphine for pain relief.

Through the evening after surgery, the patient continued to complain of severe pain and paresthesias in her right calf, not relieved by morphine. A doppler ultrasound scan of the right leg was negative for venous thrombosis. On the second postoperative day, the orthopedic on-call team was consulted; they diagnosed compartment syndrome of the right leg. The patient required fasciectomy of the right leg and excision of necrotic muscle tissue, with a prolonged hospital stay.

The Commentary

by Christian Bohringer MB BS and Gustavo Chavez MD

Background

The lithotomy position is used frequently in gynecological, colorectal, and urological operations because it allows simultaneous access to both the abdomen and the perineum (Figure 1). However, it is associated with several positioning injuries. The common peroneal nerve can be injured if it is compressed between the stirrup and the fibula.¹ The legs should therefore be placed on the outside of the stirrup rather than on the inside to prevent this potential complication. The patient’s fingers are also at-risk during lithotomy because they can be crushed by the operating table when the foot-end is flexed or extended. Positioning the hands on an arm board rather than tucking them close to the body eliminates this risk.

Optimal positioning is an interdisciplinary task that requires diligent cooperation among professionals from different disciplines.² Operating room (OR) nurses, scrub technicians, robotic technicians, anesthesiologists, and surgeons must all work together to optimize positioning for every patient, based on their individual needs. Patients with a body mass index (BMI) of less than 20 or greater than 30, patients with diabetes, and patients who are older than 70 years of age or have impaired mobility are at increased risk for positioning injuries.^3,4,5.

In the exaggerated lithotomy position, the legs are elevated significantly higher above the heart, compared with the standard lithotomy position. This situation reduces blood flow to the calf muscles unless blood pressure is augmented to compensate for the drop in lower extremity hydrostatic pressure generated by this position. For each centimeter that the ankles are elevated above the heart, the arterial pressure in the calf muscles decreases by 0.78 mm Hg.⁶ Anesthesia care providers are very mindful of this gravity-induced hydrostatic pressure drop when they anesthetize patients undergoing brain surgery in the sitting position. They elevate the pressure transducer of the arterial line to the level of the ear to measure and record blood pressure at the brain rather than at the heart level. The calf muscles, however, are not given the same priority as the brain. In rare circumstances, significant hypoperfusion with ischemic injury to the calf muscles may result in leg edema, increased intra-compartmental pressure, and subsequent necrosis of muscles and nerves.

Figure 1. Lithotomy Position Variations

Source: The ultimate guide to lithotomy position. Steris Healthcare. [Available at]

Compartment syndrome occurs because the calf muscles are enveloped by inelastic connective tissue fascia, which forms several different compartments in the lower leg (Figure 2). When muscles swell, the pressure inside the fascial compartment can become so high that perfusion remains inadequate even after the legs have been taken out of lithotomy position and the blood pressure has been augmented with intravenous fluids and vasopressor medications. Emergent surgical decompression of the compartment by cutting the fascia then becomes the only option for re-establishing perfusion to the lower leg. This phenomenon (i.e., acute lower limb compartment syndrome in the absence of trauma) is now well recognized and has been labeled “well leg compartment syndrome”.^7,8,9 It is thought to occur in about 1 in 8,700 operations in the lithotomy position,¹⁰ but this might be an underestimate if some cases go unrecognized and thus unreported.¹¹

Figure 2. Compartments in the Lower Leg

Source: Gill M, Fligelstone L, Keating J, et al. Avoiding, diagnosing and treating well leg compartment syndrome after pelvic surgery. Br J Surg. 2019;106(9):1156-1166. [Free full text]

When the patient is placed in the exaggerated lithotomy and steep Trendelenburg position, retaining devices must be used to support both shoulders to prevent the patient from sliding down the operating table in a cephalad direction. A significant portion of the patient’s body weight should be supported by these shoulder braces. The braces not only prevent sliding but also help maintain blood flow to the legs by reducing popliteal artery compression, because the calf muscles no longer need to support the patient’s entire body weight. Exaggerated lithotomy position also increases strain on the lumbar spine. Therefore, anesthesiologists are often reluctant to administer spinal or epidural anesthetics to patients placed in this position because postoperative back pain may be incorrectly attributed to the anesthetic procedure. Epidural anesthesia may also mask pain from compartment syndrome, contributing to delay in making the diagnosis.

Compartment syndrome is a rare but severe complication of operations performed in the lithotomy position.¹² It can be difficult to recognize,¹³ but the diagnosis is usually made clinically by eliciting symptoms of unexpected severe pain in the calf, swelling, numbness and weakness. The pain is typically severe and does not respond to standard amounts of postoperative pain medications. The lower leg may or may not be pale, and foot pulses may or may not be absent. The presence of foot pulses does not exclude the diagnosis. This syndrome is most often associated with lower limb fractures. Compartment syndrome is especially difficult to diagnose in the OR.¹⁴ Anesthesia providers and other staff in the OR should inspect the feet and lower legs regularly for signs of inadequate perfusion as long as the legs remain elevated in the lithotomy position. If the legs become pale or foot pulses become weak or absent, the legs should be lowered and the mean arterial pressure should be augmented. Patients with obesity are more prone to suffer this complication than patients with normal BMI.^15,16 The syndrome can also be caused by infiltrated intravenous and intraosseous catheters.^17,18

An urgent consultation by an orthopedic or trauma surgeon should be obtained to rule out compartment syndrome, as these surgeons have experience measuring compartment pressures and evaluating whether fasciotomy is necessary. There are multiple compartments in the lower limb and not all compartments may have elevated pressure. The exact pressure that requires fasciotomy depends on the clinical circumstances and the evolution over time. Pressures above 30 mm Hg are worrisome, but the diagnosis can be easily missed if the pressure is measured in the wrong compartment.

When clinicians fail to make the diagnosis of compartment syndrome in a timely manner, the patient ends up with muscle necrosis, nerve damage and loss of function. After the compartment is decompressed, dead skeletal muscle is again perfused, leading to washout of potassium and myoglobin from dead muscle. Hyperkalemia needs to be treated urgently.¹⁹ A urinary catheter should be inserted to monitor for the classic “machine oil urine”. The urine color turns dark brown when myoglobin is excreted by the kidneys. Dark urine after fasciotomy should therefore be interpreted as a sign of potential rhabdomyolysis. Serum creatinine kinase and urinary myoglobin should be measured to confirm the diagnosis. The patient should be given generous amounts of intravenous fluids,²⁰ and intravenous sodium bicarbonate may be helpful to reduce the chance of myoglobin precipitating in the kidney and causing acute kidney failure.

After fasciotomy, the affected patient is frequently left with foot drop, ankle deformities and claw foot.²¹ In severe cases hemodialysis for renal failure and amputation of the affected limb may become necessary. The fasciotomy procedure also has its own complications, such as bleeding and infection, and skin grafts may be needed to close the skin defect.

Approaches to Improving Patient Safety

Minimize the time and degree of both lithotomy and Trendelenburg positions

Every patient who has their legs elevated is at risk, especially when the patient is placed in the head-down position at the same time. The incidence is higher with operations lasting more than three hours. Changing from the lithotomy to the open leg position, limiting leg elevation, and horizontally repositioning the OR table every three hours are interventions that have been shown to reduce the incidence of “well leg compartment syndrome” after operations performed in lithotomy position.²² Perfusion of the legs should be checked regularly while in lithotomy position. If the legs look pale or blue or the foot pulses become weak or non-palpable, the legs should be lowered. In this situation, the surgeon should consider completing the operation without returning to the lithotomy position.

Augment blood pressure when the legs are elevated 

Pressure in the lower legs decreases 0.78 mm Hg for each centimeter that the ankles are elevated above the heart.⁶ If the calves are 80 cm above the heart, for example, the mean arterial pressure at the calves is then reduced by 62 mm Hg. The more extreme the lithotomy and Trendelenburg positions, the higher the blood pressure needed for adequate perfusion of the calf muscles.

Maintaining adequate blood pressure is particularly difficult when the patient has an epidural catheter that has been dosed with local anesthetic solution. Epidural anesthesia attenuates sympathetic tone and reduces blood pressure in the lower extremities. It also eliminates postoperative pain, which is the main symptom of compartment syndrome, and can delay the diagnosis until it progresses to necrosis. Maintaining adequate intravascular fluid volume and administering an appropriate vasopressor dose is important. Blood loss needs to be replaced to maintain optimal perfusion. The importance of blood pressure is confirmed by cases of compartment syndrome that occurred after deliberate hypotension to reduce blood loss during facial surgery, even though the legs were not elevated during surgery.²³

Avoid wrapping the legs tightly with restraining or calf compression devices

Placement of the intermittent pneumatic calf compression device used to prevent deep venous thrombosis was reported as difficult in this patient, as the device may have been too small to fit her calves properly. It is possible that her right calf was wrapped more tightly than the left, which might explain why she suffered compartment only in her right leg. Most cases are unilateral but bilateral compartment syndrome has been reported after colectomy and massive transfusion.^24,25 Meticulous attention is required during positioning to avoid excessive pressure to the legs that can impair perfusion.

Shoulder support bolsters should be used for steep Trendelenburg position

Shoulder braces help to support the patient’s body weight and take pressure off the patient’s calves, preventing popliteal artery compression. When introduced in a unit performing cytoreductive surgery in the lithotomy position, they eliminated all cases of compartment syndrome.²⁶ Taking some weight off the popliteal fossa may also help prevent deep venous thrombosis, although this hypothesis has not been confirmed.

Avoid hard supports at the level of the knee or calf

Careful positioning of the legs is crucial when leg holders are used.²⁷ The entire body weight of the patient should not be suspended by the calves and knees because this circumstance can cause compression of the popliteal arteries.

Every member of the team is responsible for preventing positioning injuries

All members of the surgical team including the scrub nurse, the scrub tech, the robotic technician, the anesthesia care provider as well as the surgeon are responsible for positioning the patient properly under anesthesia.²⁸ Anesthetized patients cannot move and protect themselves from the effects of poor positioning. Every team member should be encouraged to speak up and voice any concerns about the patient’s position before starting the procedure. Injuries from suboptimal positioning are especially common after long procedures and staff need to be particularly diligent in this situation.

The diagnosis of compartment syndrome should be considered early

Well leg compartment syndrome is uncommon and there is often a delay in making the correct diagnosis. It is more common after long operations and laparoscopy.²⁹ Staff therefore need to be particularly vigilant during and after this type of procedure. This patient was misdiagnosed as having a deep venous thrombosis and was anticoagulated unnecessarily. Full therapeutic anticoagulation so soon after a hysterectomy presented a significant risk of postoperative hemorrhage in this patient.

The feature of this case that pointed most strongly to the diagnosis of compartment syndrome was the severe ongoing right calf pain that had to be treated with morphine. Venous thrombosis is usually not associated with such severe pain. When the calf hurts more than the surgical site, then the diagnosis of compartment syndrome must be considered. Pallor and reduced temperature, reportedly not checked in this case, would support the diagnosis.³⁰ After the doppler ultrasound scan of the right leg failed to show a venous thrombosis, an orthopedic or trauma surgeon should have been consulted immediately and the patient should not have been aggressively anticoagulated.

Early orthopedic referral for expert evaluation

If an orthopedic or trauma surgeon had been consulted immediately after the calf pain was noticed, the patient may have been spared a lot of pain and may not have needed debridement of necrotic muscle tissue. The incidence of permanent disability after this syndrome ranges from 30%-100%.³¹ Early diagnosis by measuring compartment pressures and expediently performing a fasciotomy offer the best potential to prevent permanent disability.

Take Home Points

• Compartment syndrome in the lower leg can occur after operations in the lithotomy and steep Trendelenburg positions, especially long operations and laparoscopic procedures.
• Elevating the legs above the heart reduces leg perfusion, so blood pressure should be augmented when using radical lithotomy and steep Trendelenburg positions.
• All team members must work together to prevent positioning injuries.
• Legs should not be wrapped tightly and should be placed level with the heart every three hours to improve perfusion.
• Shoulder support bolsters must be used for the steep Trendelenburg position
• Pain and swelling in the calf after surgery are important warning signs, and should not be attributed to venous thrombosis without considering compartment syndrome.
• Early evaluation and fasciotomy by an orthopedic or trauma surgeon are key to preventing permanent injury.

Christian Bohringer, MBBS
Consulting Editor, AHRQ's Patient Safety Network (PSNet) 
Professor of Clinical Anesthesiology
Department of Anesthesiology and Pain Medicine
UC Davis Health
chbohringer@ucdavis.edu

Gustavo Chavez, MD
Anesthesiology Resident
Department of Anesthesiology and Pain Medicine
UC Davis Health
guscha@ucdavis.edu

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