Supine

This is the most common surgical position, but there are many associated variations, such as Trendelenburg, reverse Trendelenburg, or variations of chair positions.

Preventive measures

Protect pressure points

• Arms either with hands supinated <90degree (prevent Brachial Plexus injury from stretch) or alongside with hands facing inward towards the body
• Pad to prevent ulnar nerve injury – hands supinated or facing inward towards the body
• Possible pillow under knees if the history of back pain, which maintains a lordotic curve in the spine and prevents tension on the sciatic nerve
• Prevent alopecia with padding of head - increased incidence with hypothermia and hypotension
• Heels off mattress for more prolonged procedures

Anesthetic considerations

• Check eyes - always tape to prevent corneal abrasion
• Keep the head in a neutral position
• Massage/reposition the head during lengthy procedures to prevent alopecia
• CNS: blood/cerebrospinal fluid drainage is gravity-dependent, valve-less
  • When supine = increased ICP, which decreases cerebral perfusion pressure (CPP= MAP-ICP/or CVP)
• FRC and total lung capacity are decreased compared to the sitting position
  • Increased intra-abdominal pressure
  • Elevated BMI - difficulty maintaining tidal volumes due to body weight pressing down on the chest
• Zone 3 (a-v-A) in the dorsal portion of the lungs
• Minimal hemodynamic changes in the horizontal position