Introduction

Positioning is an important aspect of the perioperative care in a neurosurgical patient. The prolonged duration of neurosurgical procedures and the need for precise localization of pathological lesions demands that the patient is in a physiologically optimal, physically safe and comfortable position which offers the best approach to the neurosurgeon and access to the anesthesiologist. It must also ensure that the neurosurgeon is able to approach the area of interest with ease and minimal injury to the normal brain. Often it is achieved by positions, which are a compromise between a comfortable position for the patient and the surgeon. It is also desirable that the intended position complements the anesthetic and surgical goals such as minimizing intracranial pressure (ICP), reduction of brain retraction, providing a clear and bloodless field, and avoiding venous obstruction. Meticulous positioning is critical in the overall planning and successful outcome of any neurosurgical procedure. Inadequate planning or execution during positioning can have serious consequences.

Historical Background

Sir Victor Horsley, the pioneer of neurological surgery described the use of a separate headrest for immobilizing the head for positioning during neurosurgical procedures. Although Harvey Cushing the father of neurosurgery did not feel the need for a separate headrest, he emphasized the need for elevating the head so as to decrease the venous pressure and described the use of pillows and loosely filled long sandbags to elevate the head end. Krause the German Neurosurgeon described the need for the head of the table to be able to change its position on its transverse axis in such a way should there be an excessive bleeding, it is possible to elevate the head end. Frazier introduced the use of headrest attached to the operating table for surgeries performed for cerebellar tumors in the prone position. Later, Cushing developed a horse shoe headrest for use in the prone position. In 1916, Dr. Martel, who pioneered in sitting position, introduced the special chair and head fixation holder for surgeries performed in the sitting position. Over the past century, a lot of positions have been tried by trial and error. Various adjuncts to positioning have also been tried and many refinements of these further the cause of safety. In 1950, Moore and Edmunds described the first prone position frame for use in spinal procedures following which multiple frames have been designed. Frank Mayfield and George Kees developed the Mayfield horseshoe and general purpose headrest to stabilize the head. Subsequently in 1973, the Mayfield Kees (MFK), three pins skull clamp which is the most common and widely used in neurosurgical practice to rigidly fix the patient’s head during craniotomy was introduced.

Principles of Positioning

A precise and scrupulous approach should be undertaken during positioning of the patient for neurosurgical procedures to avoid potential complications. Since neurosurgical procedures often involve positions which have multiple effects on the cardiopulmonary systems, it should be proceeded to in a gradual fashion with vigilant monitoring of the hemodynamic status of the patient. Moreover, the prolonged duration, varying hemodynamic status, mechanical pressure, preexisting weakness, and immobility makes the patient more vulnerable to tissue damage. It is also essential to assess patients at risk to see if they will tolerate the intended position. Preoperative radiographs and MRI may be helpful in deciding position of the neck.

Although the responsibility of positioning the patient is primarily shared by the neurosurgeon and the attending anesthesiologist, every member of the surgical team plays a vital role. Positioning is usually attended to by the circulating nurse, neurosurgeon, anesthesiologist, theater technologist, and anesthetic assistants. It is initiated soon after induction of anesthesia and placement of adequate venous access and essential monitoring devices.

The neurosurgeon decides the approach to the surgical site and position required for the same depending on the location of the tumor and the intended route for its approach. The anesthesiologist ensures adequate depth of anesthesia, hemodynamic stability, adequacy of oxygenation, securing the vascular and invasive accesses during and after positioning. They also ensure that all the detached monitoring cables are reconnected and checked to verify optimal performance. The circulating nurse safeguards the dignity and safety while ensuring comfort of the anesthetized patient. Although, these individual responsibilities may vary with each institution, it is usually the circulating nurse who is responsible for keeping the positioning devices and equipment ready and ensuring adequate personnel are available for the change in position. Each member of the team has a distinctive role, and it is important that there is a close coordination between the different members of the team to avoid potential mishaps during positioning.

The Conduct of Positioning

Once all the preparations are made and lines, catheter, monitors are secured, members of the team take their respective positions. IV lines, A-lines, endotracheal tube (ETT), monitoring cables are disconnected creating a blackout state and a period of hypoventilation. It is necessary that the period of blackout state is kept to the minimum and there is at least pulse oximetry ECG and blood pressure monitoring during this period. Patency of external ventricular drains and chest tubes should be maintained. The transfer should be swift, smooth, and coordinated.

After achieving the final desired position, adequate access, optimal function of the IV lines, A -lines and monitors are checked and confirmed. Special attention is paid to the hemodynamic stability and respiratory compliance in the newly achieved position. Normal alignment of the head and neck with the body should be maintained. The endotracheal tube migration (either in to the bronchus or outside) should be ruled out and then stabilized to avoid kinking. The cuff pressure needs to be rechecked in the new position as there may be changes and kept within the normal range. To ensure optimal safety, a repositioning checklist is ideal.

Table 10.1 describes a comprehensive repositioning checklist to be performed after achieving the desired position.

The anesthesiologist ensures that the eyes are free from direct pressure to minimize ocular damage. Optimal head end elevation is provided to reduce venous pressure. All potential pressure points (sacrum, ischium, trochanter, and heel) are well padded by the placement of viscoelastic (gel) pads so as to redistribute mechanical pressure. Any contact of the patient’s skin with metal surfaces should be avoided to prevent burns related to the use of diathermy. Since there is a rapid fall of temperature following induction of general anesthesia, active efforts should be undertaken to reduce fall in temperature by limiting the exposure of the skin to the minimum and use of temperature-regulating blankets or forced air warming devices. Warm and humidified inspired gas and fluids should be used combined with temperature monitoring. Since many of the neurosurgical patients have weakness related to immobility and use of anticoagulants is not preferred except under special circumstances, it is important to prevent thromboembolic complications. Thromboembolic deterrent stockings and sequential compression devices are applied in patients undergoing prolonged procedures. The operating table is an important accessory. The position and stability of the operating table should be checked by the operating nurse before the patient is placed on the table. Optimal functioning of the remote control should be confirmed since this is a vital adjunct for subsequent changes in position. It is important to ensure that no body part extends beyond the edge of the OR table or positioning devices. The OR table safety strap must not be secured in such a manner that it is not too tightly placed across the patient in order to avoid pressure. It must be possible to comfortably insert two fingers under the mid-section of the safety strap to ensure that it is safely applied. The final position of the patient should be acceptable to the surgeon and anesthesiologist, providing easy access to operating microscope, navigation systems, and radiological imaging.

Surgical Approach for Craniotomies

There are about six standard craniotomies described.

• •
  

  Pterional craniotomy (frontotemporal)

  
  
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  Temporal and subtemporal craniotomy

  
  
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  Anterior parasagittal and subfrontal approach

  
  
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  Posterior parasagittal craniotomy

  
  
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  Midline suboccipital craniotomy

  
  
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  Lateral suboccipital approach

Table 10.2 describes the standard surgical approach for craniotomies, their variants, and the various options of body positions for each approach.

Positioning for Craniotomy

Fixation of the Head for Craniotomy

Fixation of the head after deciding on the final position of the head is a crucial step in positioning the neurosurgical procedure. The head may be positioned on a variety of fixation devices depending upon the surgery. The common devices used are MFK head clamp, Sugita head frame assembly, horseshoe headrest.

Mayfield Kees Skull Fixation Device (Ohio Medical Instrument Co., Cincinnati, OH)

The Mayfield head holder ( Fig. 10.1A ) consists of a clamp with three sterile pins. It is inserted into the skull in a band-like area just above the orbits and the pinna. Special care is taken to avoid the frontal sinus and the temporal bone. It should be positioned such that it does not interfere with the cranial incision but facilitates the attachment of the halo self-retaining retractor. When the clamps are squeezed together, the gears slide until the pins are seated in the skull. The knob housing the tension spring and gauze is tightened. Each ring exerts a pressure of 20 lb. In the adults, up to 80 lb of pressure is allowable whereas in the pediatric population, 30–40 lb is the preferable limit. It is then clamped on to the head frame assembly which is attached to the table ( Fig. 10.1B ). The manufacturer recommends the use of specially designed pediatric pins for children less than 10 years of age but it is preferable to avoid using MFK in children less than 3 years.

(A) Mayfield Kees three-pin head holder, (B) Mayfield Kees with head frame assembly, (C) Sugita four-pin head holder, (D) Sugita pins with head frame assembly.

Problems associated with the use of Mayfield Kees

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  Pressure necrosis

  
  
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  Perforation/Fracture of skull

  
  
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  Injury to middle meningeal artery leading to hematoma or arteriovenous fistula​

  
  
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  Extradural hematoma remote from pin site

  
  
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  Scalp and eye laceration due to slippage of the head holder

  
  
• •
  

  Bleeding from the pin site

  
  
• •
  

  Air embolism

  
  
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  Malposition, poor fixation

  
  
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  Pin site infection

  
  
• •
  

  Cervical spine injuries due to inadvertent patient movement

Sugita Multipurpose Head Frame

Sugita multipurpose head frame devised by Dr. Sugita uses four head pins to position the patient’s head ( Fig. 10.1C ). It is ideal for procedures where maximum support is necessary. It allows for a full 360° rotation and adjustment of the angle of patient’s head during surgery if required. It consists of a robust head frame assembly and a head holder.

The head holder consists of four pins. The head frame assembly consists of a basal frame which is mounted on to the head holder ( Fig. 10.1D ). The self-retaining retractors are attached to the base frames using thumb screws which are spaced at 35° angles. At each end of the basal frame, there are two holes to support the hand rest and instrument receptacles. The angle and height of the hand rest are all adjustable to suit individual requirements. The semicircular bar mounted on the basal frame is used to attach the scalp hooks or the self-retaining retractors. There is an additional provision of a quarter frame such that it provides enough space to facilitate lateral suboccipital approach.

Horse Shoe Head Rest

It is a horseshoe-shaped headrest with both vertical and lateral adjustments which provide flexibility in patient positioning both in supine and prone position. It also has gel pads which make it comfortable for use. The pulley rod attachment for skeletal traction makes it an attractive option for cervical spine procedures. Precaution must be taken so as to avoid pressure on the face in the prone positions which may lead to necrosis of the forehead, injury to the eye. Scalp alopecia is a known complication in patients positioned supine on horseshoe headrest for prolonged duration.

Positions Used for Craniotomies

Supine Position or Dorsal Decubitus Position

It is the most commonly used position in neurosurgery. It does not require any special equipment for positioning and is often easily achievable because the patient is able to move into the bed by themselves thereby allowing most of the positioning to be completed before the induction of anesthesia. It is safe since it does not require disconnection of the ETT and other monitoring devices.

In this position, the stroke volume (SV), cardiac output (CO), and venous return are optimal, and there is minimal decrease of the mean arterial blood pressure. The functional residual capacity (FRC) and total lung capacity (TLC) are decreased due to atelectasis of the dependent lung zones causing ventilation–perfusion (V/Q) mismatch. Manikandan et al. have shown that the PaCO ₂ levels, 30 minutes after induction of anesthesia and positioning in the supine position, were elevated due to increased alveolar dead space. The CPP is maintained but the CSF drainage may be impaired. The head should be positioned above the level of the heart to promote venous drainage and to reduce cerebral edema. The head may be rotated up to 45° relative to the body but if more rotation is needed, a roll or pillow should be placed under the contralateral shoulder. This also causes mild displacement of the abdominal viscera downwards, improving the ventilation.

After the final positioning of the head either in the flexion or extension position, it is important to rule out endobronchial migration of the endotracheal tube. It is preferable to fix the ETT on the side opposite to the surgery to avoid accidental disconnections. Certain procedures such as the transoral approach to the odontoid requires tube placement at the center of lips. A bar across the table enables access to the tubes and allows for observation of the face after draping. Direct pressure on the globe is avoided by the placement of an attachment placed over the patients face to prevent the drapes falling over the eyes. It is important to avoid skin to metal contact. The head is positioned above the heart to facilitate venous return. The arm should be positioned so as to minimize the pressure on the ulnar groove. Neutral forearm position should be maintained when the arms are tucked inside. There must be adequate padding at the ulnar nerve to avoid ulnar neuropathy. Brachial plexus injury can occur if the arms are abducted more than 90°, where the head of the humerus acts as a fulcrum around which the nerves of the brachial plexus are stretched. Prolonged pressure on the peroneal nerve at the fibular head should be minimized by protective padding. Bony contact points at elbow, knee, occiput, sacrum, and heel must be padded. The patient is firmly secured to the operating table with safety straps, which are across the patient’s thigh so that the vessels are not occluded. The classical supine position leads to the loss of lateral lumbar lordosis and may cause postoperative back pain.

The supine positioning is often slightly modified either into a contoured position (lawn chair position) or reverse Trendelenberg position. The lawn chair or contoured position ( Fig. 10.2 ) is physiologically more favorable for the lumbosacral spine. A 15° angulation and flexion at the trunk, thigh, and knee is provided. The knee is kept flexed by a pillow under it. This position is also associated with improvement of the venous return from the lower extremities with optimal CSF and lymph drainage.

Lawn chair position.

The head-up tilt or reverse Trendelenberg position involves 10–15° tilt from the horizontal axis, and it improves the venous drainage from the heart.

Post positioning, the nurse assesses and documents that the pressure points such as the occiput, scapula, olecranon, elbows, popliteal space, and calcaneum are free of pressure. It is also important that these are rechecked and documented at the end of the procedure.

Lateral Position

In the lateral position, hemodynamic parameters are minimally changed with mild decrease in SV, CO, and increase in systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR). This leads to modest decreases in systolic blood pressure and mean arterial pressure (MAP) as compared to supine position. With regard to ventilation, there is mild increase in PaO ₂ as compared to the supine position with a normal value of PaCO ₂ . Perfusion is best in the dependent lung zone while the nondependent lung is better ventilated thereby causing a mild V/Q mismatch. However, since the abdominal excursions are free as compared to the supine position, its impact on oxygenation is limited.

With extreme neck flexion, there is a possibility of decreased jugular venous flow (JVF), jugular venous resistance (JVR), and ICP. A chest or axillary roll is placed under the thorax below the axilla to prevent axillary compression. When the head is on the MFK, the dependent shoulder is brought beyond the cephalad edge of the operating theatre table and the dependent arm is rested on a low padded arm rest which is inserted between the table and head fixation. In these cases, there is no need for an axillary roll. The nondependent arm is usually placed over the trunk on a pillow. It may also be positioned on the airplane arm rest. To monitor the blood flow to the dependent arm, it is prudent to place the saturation probe or arterial line on the dependent arm ( Fig. 10.3A and B ). The trunk is supported on lateral bolsters and secured by tapes. When the head is not fixed on MFK, it is important to support the patient’s head with a pillow to avoid angulation of the cervical spine. The lower limbs are positioned with pillow between the legs and the dependent extremities are flexed to avoid pressure over the fibula head and the peroneal nerve. Complications anticipated with lateral positioning are brachial plexus injury, vascular compromise to the dependent upper extremity, ear and eye injuries, and injury to the suprascapular nerve of the dependent shoulder.

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