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INTRODUCTION

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Controlled or deliberate hypotension is practitioner-initiated reduction of an anesthetized patient’s blood pressure (BP) to achieve a specific therapeutic purpose. The hypotensive state under hypotensive anesthetic sustains tissue perfusion with adequate blood flow.

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INDICATIONS

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As shown in Table 19-1, controlled hypotension can be useful in a variety of surgical situations. The main indications are (1) decreasing blood loss and subsequent transfusion requirements; and (2) facilitating operative conditions by improving visualization of the operative field. Controlled hypotension can be used alone or as part of a larger blood conservation regimen that may include RBC salvage, antifibrinolytics, normovolemic hemodilution, and/or positioning to reduce blood loss and transfusion requirements.

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TABLE 19-1Uses for Controlled Hypotension
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Controlled hypotension has a role in procedures not associated with significant blood loss through improved visualization. For example, during thoracic aortic endovascular interventions, brief periods of controlled hypotension may facilitate an accurate positioning of the endovascular graft. Hypotension at the time of graft deployment minimizes graft migration risk.

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CONTRAINDICATIONS

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Patients at risk for ischemia or with impaired autoregulation are poor candidates for controlled hypotension. Frequently excluded conditions listed in Table 19-2 avoid exacerbating the patient’s pre-existing disease. Many conditions are relative contraindications, based on the patient’s condition, type of surgery, monitoring used, and the technique for achieving hypotension.

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TABLE 19-2Contraindications to Controlled Hypotension
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A list of absolute contraindications might include cerebrovascular disease with severe carotid stenosis, symptomatic or severe aortic or mitral stenosis, and stage IV chronic kidney disease. Patients with less severe forms of these conditions may benefit from controlled hypotension, but the decision to proceed with should be made with consideration for the heightened risk their comorbid conditions present and possible alternatives.

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MONITORING

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In addition to standard monitors, the use of invasive BP monitoring is appropriate when providing controlled hypotension. Since hypocarbia decreases cerebral blood flow, maintenance of normocarbia is important for preserving cerebral perfusion during hypotension. The monitoring of BP in patients in nonhorizontal positions deserves special attention. There can be a significant discrepancy in height between the brain and the site of BP measurement, resulting in low cerebral perfusion pressure. This can be minimized by placing the transducer at the level of the external auditory meatus in patients whose BP is being monitored with ...

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