Introduction
To allow access to various surgical operations, different patient positions are needed. Every position affects ventilation and hemodynamics and exposes patients to potential risks, including pressure sores and nerve damage. The surgeon, the anesthesiologist, and the operating room nurses are all responsible for positioning the patient for a surgical procedure. The chosen position might cause physiologic abnormalities and soft tissue damage, such as pressure-induced injury, nerve injury, ulceration, and compartment syndrome. The anesthetist is crucial in reducing the risks involved with posture like supine, lithotomy, lateral prone, and sitting.
What Is the Patient Positioning Technique During Anesthesia?
The patient positioning technique during anesthesia are broadly distinguished into seven types are:
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Supine: Most surgical operations are performed when the patient is supine. Although, the supine placement impacts breathing because it causes the anesthetized patient's functional residual capacity (FRC) to be significantly reduced. The closure capacity may be greater than the FRC when the FRC decreases, which could result in a V/Q mismatch and subsequent hypoxia. The higher incidence of these complications is seen in elderly individuals who have higher closure capacity, patients who are obese or pregnant and who already have low FRCs. The use of positive end-expiratory pressure can decrease the effect (PEEP).
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Lithotomy: Many treatments utilize the lithotomy posture, including gynecological and urological surgery. Trendelenburg position is frequently paired with the lithotomy position, which may worsen the effects on the heart and lungs. However, care must be taken to ensure that the endotracheal tube does not dislodge or shift with any change in position. The blood volume in the leg veins is diminished when the legs are in the lithotomy position; by this position, the blood volume is distributed more evenly throughout the body and boosts venous return to the heart. As a result, increasing the peripheral blood volume can cause pulmonary edema in individuals who are susceptible to it. Usually, blood will continue to refill the legs' venous system when placed back in the supine position after the treatment. The venous return may decline, causing the cardiac output to decline. Hypotension may occur when baroreceptor reflexes are triggered. Hence blood pressure should be monitored carefully.
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Lateral: The dependent lung is generally under-ventilated and over-perfused in the anesthetized patient, whereas the non-dependent lung is over-ventilated and under-perfused. This causes an increase in ventilation-perfusion disparity that is typically well tolerated but may result in hypoxemia in people with compromised health. When a patient is positioned laterally, access to the airway is not ideal. Hence, the airway device must be securely attached to avoid accidental dislodging while performing the treatment. Multiple surgical procedures, including thoracic, hip, and shoulder surgeries, are performed using the lateral position. In the lateral position, most of the patients may result in hypoxia.
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Prone: Lying in a prone position impacts the airway. Hence, care must be taken to maintain it. Care should be taken while turning the patient because the tube is susceptible to movement and should be clinically checked after turning. Ventilation may even get better when lying prone compared to the supine position. However, the abdomen should not be put under strain, and patients should be supported on bony areas using supports across the chest (just below the clavicle) and the pelvis. The prone position creates difficulties for cardiopulmonary resuscitation and makes it challenging to place defibrillator pads. Considering the application before turning the patient prone to high-risk situations is advised. According to studies, lying on one's back reduces cardiac output. Reduced venous return, effects on arterial filling, and lower left ventricular resistance are based on elevated intra-thoracic pressures. Although, abdominal pressure can make this worse by compressing the IVC and reducing venous return. However, compression of the IVC after spinal surgery may potentially cause minor errors like the unstable return of blood to the heart via the IVC, which will instead be diverted through the venous plexus of the spinal column, increasing the amount of blood in the operating room.
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Sitting: In some intracranial procedures, particularly those involving the posterior fossa, the shoulder surgeon will frequently adopt the sitting or beach-chair position. When the patient is sitting, it may lead to hypotension. Sitting up will cause the baroreceptors in an awake patient to activate the sympathetic nervous system and increase the systemic vascular resistance, which controls blood pressure. Patients should be gently raised, and hypotension should be treated with volume resuscitation and vasopressors.
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Trendeleberg: The "Trendelenburg" is when the patient is inclined to head down by at least 15 degrees. Oedema of the face and larynx can result in prolonged Trendelenburg positioning. In cases with steep posture or evidence of facial edema, this should be evaluated before extubation using a cuff leak test. Keeping the IV fluid administration to a minimum throughout the case can assist in minimizing the risk of this complication. During placement, the endotracheal tube tip may shift laterally, which could result in endobronchial intubation. Because of the diaphragm's continued cephalad migration, the Trendelenburg position causes a further decrease in FRC compared to the supine position. Patients may require higher airway pressures to attain adequate tidal volumes because Trendelenburg increases the risk of airway obstruction and reduces respiratory compliance. Having a high peak inspiratory pressure might cause barotrauma.
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Reverse Trendeleberg: Compared to supine, FRC is higher in the reverse Trendelenburg position. Positive pressure breathing requires caution when managing lung volumes because it may lead to lung compliance. To avoid cerebral hypoperfusion, the anesthetist should consider the hydrostatic gradient between the blood pressure cuff and the brain when putting the patient in reverse Trendelenburg.
What Is the Complication Associated With the Position of the Patient in Anesthesia?
The general complication involved in positioning patients are:
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Transferring Unconscious Patients: Potential damage experienced during anesthesia depends on the maneuvering and the final position. Before any movement, intravascular lines, endotracheal tubes, and urine catheters should be secure and free to move. After repositioning, all equipment's position and function must be reviewed.
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Peripheral Nerve Injuries: These remain undiagnosed for a few days following surgery. A recent prospective review found no appreciable difference in the incidence of ulnar neuropathy. It is one of the most common preoperative nerve injuries in patients receiving general anesthesia, regional anesthesia, or sedation. However, this contradicts the long-held belief that avoiding general anesthesia can prevent or reduce these injuries.
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Ocular Injuries: Although ocular injuries during anesthesia and surgery occur relatively rarely (less than 0.1% of anesthetics), their severity can range from minor discomfort to total blindness. The most frequently reported injury is a corneal abrasion. They are brought on by direct foreign object trauma to the cornea and a reduction in basal tear production due to general anesthesia. The use of eye tape can significantly reduce the risk of these injuries. However, eye ointment has little impact.
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Pressure Sores: All patient positions result in abnormally high pressure applied to relatively limited areas of the body's surface. A decrease in perfusion can cause tissue ischemia, tissue deterioration, and the emergence of pressure sores.
Conclusion
To maximize surgical access, various patient positions are necessary, but each position has consequences and potential hazards that need to be considered. To reduce the danger of nerve injury in all situations, special attention must be paid to padding pressure points and anatomically positioning limbs.
