Preventing Positioning Injuries: An AnesthesiologistsPerspectives Sarah Gerken, MD

Every member of the operating room team faces both individual and group challenges whencaring for patients. A common concern is proper positioning of patients to prevent injury.

Patient injuries due to surgical positioning can take many forms, from end organ damage due tohypoxia or hypotension to direct nerve injury due to compression or traction. This articlediscusses various forms of positioning injuries incurred by patients in common orthopaedicsurgical positions and illustrates the spectrum of complications that may occur.

When considering positioning injuries, it is important to be aware of patients who are at higherrisk. Patients at increased risk of positioning injuries, specifically peripheral nerve injury,include obese patients and those with diabetes, peripheral vascular disease, hereditaryperipheral neuropathy, or an anatomic variable (eg, cervical rib). Thin patients may also havean increased risk of sustaining peripheral nerve injury during surgery.

Peripheral nerves appear to be particularly vulnerable to injury during positioning. According toinformation from the American Society of Anesthesiologists (ASA) Closed Claims Database, asignificant number of anesthesia-related claims involve nerve damage. Of more than 1,500claims reviewed, 15 percent were for anesthesia-related nerve injury.

Ulnar nerve, brachial plexus, spinal cord, and lumbosacral nerve root injuries were the majorcategories of nerve injury resulting in a medical liability claim against an anesthesiologist. Eachposition can expose various nerves to potential for injury and it is important to be aware ofthem while positioning the patient.

Supine position risksThe supine position, the most commonly used position for all surgical procedures, is generallythe safest position and not associated with dramatic or catastrophic positioning injuries. Eventhis position, however, can lead to postoperative ulnar neuropathy, the most commonposition-related nerve injury.

Ulnar neuropathy accounts for approximately one third of post-positioning nerve injuries and ismore common in men. The larger tubercle of the ulnar coronoid process in men maycompromise the resistance of the ulnar nerve to injury. Pronation of the forearm exerts morepressure on the ulnar nerve, while supination decreases pressure.

The ASA has developed a Practice Advisory for the Prevention of Perioperative PeripheralNeuropathies that includes recommendations for positioning the upper extremity in the supineposition (see sidebar). In general, the recommendations cover the use of padded armboards,limiting arm abduction to 90 degrees, and keeping the forearm in a neutral or supinatedposition.

Hip arthroscopies, which are generally performed in a supine position with traction, haveincreased in numbers over the years. The unique positioning requirements for hip arthroscopy,aspects of which are similar to positioning on the hip fracture table, may result in injuriestypically not encountered in other orthopaedic procedures.

The mechanical traction necessary for surgical exposure leads to the most commonly reportedcomplications of hip arthroscopy. Injuries associated with traction of the operative extremity aswell as those secondary to counter-traction against the perineal post have been reported.

Compression injury may include edema, hematoma, and pressure necrosis to the scrotum/labiamajora, as well as neurapraxia of the pudendal nerve. Limiting the duration of traction to lessthan 2 hours and generous padding of the perineal post to more than 9 cm in diameter havebeen recommended to help decrease the incidence of perineal injury during hip arthroscopy.

Beyond physical injury, patients, particularly morbidly obese patients, can decompensate in thesupine position. Fatal cardiorespiratory problems, known as Obesity Supine Death Syndrome,can develop in morbidly obese patients who are placed in the supine position. Moving an obesepatient from a semi-sitting or sitting position to a supine position can result in increases inoxygen consumption, cardiac output, and pulmonary artery pressure that push the limits of thepatients cardiac reserve. It is therefore necessary to be conscientious of positioning the obesepatient, even in the supine position.

Beach Chair position risksShoulder surgery presents risks for significant injury whether the patient is in the lateraldecubitus or beach chair position. The beach chair position has risks associated with thenegative pressure gradient between the surgical site and the heart. This situation predisposesthe patient to a rare, but potentially fatal, venous air embolism; if a significant amount of air isentrained in the venous circulation, sudden and complete cardiovascular collapse can occur.

The upright position can also lead to potential cerebral injury due to hypotension. Consider ascenario where a blood pressure cuff is placed on either the arm or, even worse, the leg. Whenthe patient is in an upright position, pressure measurements should be performed at the levelof the brain, because a large hydrostatic gradient exists between the brain and the site of blood

pressure measurement.

For each inch of height difference between the blood pressure cuff and the brain, there is acorresponding drop in blood pressure of approximately 2 mm Hg (10). When this is taken intoconsideration, it is easy to see that a mean arterial blood pressure measurement taken at theupper arm, or more dramatically at the lower leg, does not accurately reflect the mean arterialpressure at the level of the brain.

If, for example, a surgeon requests hypotension to be induced to aid in visualization, the endresult may be inadvertent cerebral hypoxia. A safer solution is to control bleeding by raising thearthroscopic pump pressure.

Studies have demonstrated that a 49 mm Hg difference between the systolic blood pressureand the pressure within the subacromial space can provide a safe and clear operative field. Thiscan be achieved by either raising the arthroscopic pump pressure or inducing hypotension.Whether intentional or not, hypotension in the beach chair position has the consequence ofdecreased cerebral blood flow and all of the associated potential damage, including ischemicbrain damage and possible vision loss.

Less serious, but still concerning, are positioning injuries secondary to incorrect headpositioning in the beach chair position. Case reports of cutaneous neurapraxias involving thelesser occipital and greater auricular nerves have been attributed to direct compression of thenerves from the head rest holder. It is not uncommon practice for the anesthesia team to placeprotective goggles over the eyes of the patients undergoing shoulder surgery; pressure on thesupraorbital nerve, either from goggles or restraints, could result in injury to this nerve,resulting in eye pain, forehead numbness, and photophobia.

Sarah Gerken, MD, is an assistant professor in the Department of Anesthesiology at theUniversity of Toledo Medical Center.

Editors Note: This is the first of two articles on preventing injuries due to positioning duringorthopaedic surgery. This article covers risks for the supine and beach chair positions; the nextarticle will cover the lateral and prone positions.

Recommendations from the ASAII. Specific Positioning Strategies for the Upper Extremities

Arm abduction in supine patients should be limited to 90.

Patients who are positioned prone may comfortably tolerate arm abduction greater than 90.

Supine Patient with Arm on an Arm Board

The upper extremity should be positioned to decrease pressure on the postcondylar grooveof the humerus (ulnar groove).

Either supination or the neutral forearm positions facilitates this action.

Supine Patient with Arms Tucked at Side

The forearm should be in a neutral position.

Flexion of the elbow may increase the risk of ulnar neuropathy, but there is no consensus onan acceptable degree of flexion during the perioperative period.

Prolonged pressure on the radial nerve in the spiral groove of the humerus should be avoided.

Extension of the elbow beyond the range that is comfortable during the preoperativeassessment may stretch the median nerve.

Periodic perioperative assessments may ensure maintenance of the desired position.

Excerpted with permission from American Society of Anesthesiologists Task Force on Preventionof Perioperative Peripheral Neuropathies. Practice Advisory for the Prevention of PerioperativePeripheral Neuropathies. Anesthesiology 2011;114:11.

References:

Stoelting RK: Postoperative ulnar nerve palsy: Is it a preventable complication? AnesthAnalg 1993;76(1):79

1.

Kroll DA, Caplan RA, Posner K, Ward RJ, Cheney FW: Nerve injury associated withanesthesia. Anesthesiology 1990;73:202207.

2.

Cheney FW, Domino KB, Caplan RA, Posner KL: Nerve injury associated with anesthesia: Aclosed claims analysis. Anesthesiology 1999;90:10621069.

3.

Schubert, Armin: Positioning injuries in anesthesia: An update. Advances in Anesthesia2008;26:3165.

4.

Prielipp RC, Morell RC, Walker FO, et al: Ulnar nerve pressure: Influence of arm position andrelationship to somatosensory evoked potentials. Anesthesiology 1999; 91(2):345354.

5.

Practice advisory for the prevention of perioperative peripheral neuropathies: A report bythe American Society of Anesthesiologists Task Force on Prevention of PerioperativePeripheral Neuropathies. Anesthesiology 2000;92(4):11681182.

6.

Pohl A, Cullen DJ: Cerebral ischemia during shoulder surgery in the upright position: A caseseries. J Clin Anesth 2005;17:463469.

7.

Morrison DS, Schaefer RK, Friedman RL: The relationship between subacromial spacepressure, blood pressure and visual clarity during arthroscopic subacromial decompression. Arthroscopy 1995;11:557560.

8.

Bhatti MT, Enneking FK: Visual loss and ophthalmoplegia after shoulder surgery. AnesthAnalg 2003;96:899902.

9.

Rains DD, Rooke G, Wahl, CJ: Pathomechanisms and complications related to patientpositioning and anesthesia during shoulder arthroscopy. Arthroscopy 2011; 27:532541.

10.

Park TS, Kim YS: Neuropraxia of the cutaneous nerve of the cervical plexus after shoulderarthroscopy. Arthroscopy 2005; 21:631.e1631.e3.

11.

Winfree CJ, Kline DG: Intraoperative positioning nerve injuries. Surg Neurol 2005;63:518.12.

Klein AH, France JC, Mutschler TA, Fu FH: Measurement of brachial plexus strain inarthroscopy of the shoulder. Arthroscopy 1987;3:4552.

13.

Tuncali BE, Tuncali B, Kuvaki B, et al: Radial nerve injury after general anaesthesia in thelateral decubitus position. Anaesthesia 2005; 60(6):602604.

14.

Garland H, Moorhouse D: Compressive lesions of the external popliteal (common peroneal)nerve. Br Med J 1952;2:13731378.

15.

Newton G, White E: Anaesthesia 2010;65:863.16.

Papavasiliou AV, Bardakos NV: Complications of arthroscopic surgery of the hip. Bone andJoint Research 2012;1(17):131144.

17.

Lee LA, Roth S, Posner KL, et al: The American Society of Anesthesiologists postoperativevisual loss registry: Analysis of 93 spine surgery cases with postoperative visual loss.Anesthesiology 2006;105(4):652659.

18.

Tsueda K, Debrand M, Zeok SS, et al: Obesity supine death syndrome: reports of twomorbidly obese patients. Anesth Analg 1979; 58: 345347

19.

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