Acute hypotension is an extremely common condition seen in a wide variety of patients and is defined as a condition in which the blood pressure is decreased to a point that is inadequate for normal tissue perfusion and oxygenation.
Hypotension may be a sign of shock or may progress to a ‘shock’ state. Its causes are multifactorial with etiologies such as fluid volume deficits (hypovolemic), decreased cardiac output (cardiogenic), inadequate intravascular volume (vasodilatory), or iatrogenic effects of certain classes of medications. The severity of the condition is related to the amount of circulating blood. If blood does not reach vital organs, perfusion is compromised, resulting in tissue hypoxia and damage to the vital organs of the brain, heart and kidneys.
The mortality rate for shock is extremely high, reaching 60% to 80% in cardiogenic shock. For this reason, it is imperative that interventions target resolving severe hypotension or shock as quickly and effectively as possible. One intervention commonly used to manage severe hypotension is Trendelenburg positioning, defined as a position in which the head is low and body and legs are on an inclined or raised plane.
Theoretically, it shifts abdominal organs upward and out of the pelvis and increases blood flow to the brain in case of hypotension or shock. However, use of this intervention is controversial, and many experts in the medical and nursing field question its efficacy. In addition, some clinicians and nurses concede that the intervention has harmful effects that may actually worsen patient outcomes. [Trendelenburg Positioning to Treat Acute Hypotension: Helpful or Harmful. Clinical Nurse Specialist: July/August 2007 – Volume 21 – Issue 4 – pp 181-187]
It is important to seek answers to the questions surrounding the efficacy of Trendelenburg positioning because it is frequently used by nurses and health care givers, who are patient advocates and are often the first to recognise a deteriorating patient condition. Trendelenburg positioning is used by nurses and health care givers because it is believed to improve patients’ outcomes.
The support for this intervention is anecdotal and can be traced to the 1800s. The position is named for the surgeon who originally coined it’s use in 1890, Dr. Friedrich Trendelenburg who studied medicine in Scotland and Berlin before becoming a professor of surgery and surgeon-in-chief in Leipzig, Germany. His fascination with urology linked his name to the positioning technique, now commonly known as the Trendelenburg position or head-down-tilt (HDT) position.
Dr. Trendelenburg used this head down, elevated body position to surgically manage strangulated hernias, bladder stones, and various gynaecological problems. Friedrich Adolf Trendelenburg placed patients supine with the head of the bed tilted 45 degrees downward to aid visualisation of abdominal organs for surgical procedures.
However, it was not until World War I that Walter Cannon, an American physiologist, introduced the position as a treatment of shock. He promoted the technique as a way to increase venous return to the heart, increase cardiac output, and improve blood flow to vital organs.
Today, some clinicians use this position, now called the Trendelenburg position, to treat hypotensive episodes. They believe this position shifts intravascular volume from the lower extremities and abdomen to the upper thorax, heart, and brain, improving perfusion to these areas.
But as far back as the 1960s, researchers found undesirable effects of the Trendelenburg position, including decreased blood pressure, engorged head and neck veins, impaired oxygenation and ventilation, increased aspiration risk, and greater risk of retinal detachment and cerebral oedema.
Evidence shows that while this position shifts fluid, it adversely engorges the right ventricle, causing it to become dilated, which further reduces cardiac output and blood pressure. It also impairs lung function by compromising pulmonary gas exchange. Abdominal contents shift upward, increasing pressure on and limiting movement of the diaphragm and reducing lung expansion. Lung compliance, vital capacity, and tidal volumes decrease while the work of breathing increases. The result is impaired gas exchange—hypercarbia and hypoxemia. Evidence also suggests that when obese patients are placed in Trendelenburg position, lung resistance increases significantly and pulmonary gas exchange worsens.
The Trendelenburg position has little, if any, positive effect on cardiac output and blood pressure. It impairs pulmonary gas exchange and increases the aspiration risk. The evidence doesn’t support its use to treat hypotension. However, evidence-based practice does support elevating the lower extremities—without using a head-down tilt position—to mobilize fluid from the lower extremities to the core during hypotensive episodes. Sometimes called a modified Trendelenburg position, this position has been found to support blood pressure without the negative consequences of the traditional Trendelenburg position.
An extensive search on Ovid Medline, CINAHL, and Evidence-Based Medicine Review Multifile was conducted to identify pertinent articles. The inclusionary criteria were, the use of HDT of greater than, or equal 10̊, and patients under general anesthesia. Six articles were identified and critically appraised. The data compiled in this systematic review suggest there is an increase in cardiac preload with no consequent increase in cardiac output or performance. The data suggest there are multiple negative consequences of HDT on pulmonary function including a decrease of functional residual capacity, an increase of atelectasis, and a decrease in oxygenation. This systematic review concluded, there is a lack of clear evidence to support the use of HDT as a treatment for acute hypotension. In the controlled environment of the surgical setting, head-down tilt should be utilized judiciously and for as short a duration as possible. HDT position should be avoided in patients who are obese, have pre-existing obstructive pulmonary disorders, have New York Heart Association class III heart failure, or other significant cardiopulmonary dysfunction.[Carter, Aaron T., “The Cardiopulmonary Consequences of the Trendelenburg Position in Patients Under General Anesthesia” (2010). School of Physician Assistant Studies. Paper 214. http://commons.pacificu.edu/pa/214]
Ensuring that healthcare practices are based on the best evidence can improve patient safety. To safely and effectively manage acutely ill patients, clinicians must evaluate traditional practices and systems.
Reference: Questioning Common Nursing Practices
What Does the Evidence Show? Am Nurs Today. 2013;8(3). http://www.medscape.com/viewarticle/780771_4