The Effect of Guanfacine on Delirium in Critically Ill Patients

Delirium is a common problem in critically ill patients with a reported prevalence in the ICU ranging from 11% to 83%. Delirium has been associated with worse clinical outcomes including increased days on mechanical ventilation, length of hospital stay, cost of care, self-removal of important devices (endotracheal tubes, central venous catheters), use of physical restraint, long-term cognitive impairment, readmission, and mortality. The etiology of delirium is multifactorial, and risk factors include advanced age, substance abuse, metabolic derangements, and sleep disturbances.

Unfortunately, evidence-based strategies for treatment of ICU delirium do not exist. Even with the lack of strong evidence, both non-pharmacologic and pharmacologic therapies are used as standard care in clinical practice. Non-pharmacologic strategies considered as standard care include removal of causative factors, sleep maintenance, reorientation during the day, early mobilization activities, timely removal of catheters and physical restraints, and use of a scheduled pain management protocol. In combination with these non-pharmacologic strategies, ICU patients are treated with pharmacologic agents to render the patient safe and manageable and to promote sleep and normal circadian cycle. Despite lack of an FDA approved drug for treating delirium and clear-cut efficacy of any drug, various pharmacologic agents standardly used to treat delirium in the ICU include dopamine antagonists, acetylcholinesterase inhibitors, melatonin, antipsychotics, alpha-2 agonists, and glutamate antagonists. Antipsychotics, such as haloperidol, have been most commonly used. However, the effectiveness of routinely using antipsychotics in managing delirium has been questioned given the potential for adverse effects, medication interactions, and unproven benefit. Haloperidol can cause serious side effects including Q-T prolongation, sedation, and extrapyramidal symptoms. For this reason the use of haloperidol is less than ideal in the elderly patient population. Recent studies have looked at the perioperative use of dexmedetomidine in mechanically ventilated patients experiencing hyperactive delirium. Dexmedetomidine is a centrally-acting alpha 2 adrenergic receptor (α2-AR) agonist that generally quiets noradrenergic activity, producing sedative, analgesic and antihypertensive effects. When compared to haloperidol, patients receiving dexmedetomidine have fewer ventilation days, shorter ICU length of stay, less need for tracheostomy, and quicker resolution of delirium symptoms. Unfortunately, dexmedetomidine is expensive and delivered as an intravenous infusion.

Guanfacine, an alpha-2A antihypertensive agent with a safe pharmacodynamic profile, has also been reported as treatment of ICU delirium. It has found use as an adjunct therapy in the management of Attention Deficit Hyperactivity Disorder (ADHD). Compared to dexmedetomidine, guanfacine is a pure alpha-2A agonist with higher selectivity for the dorsolateral PFC structures leading to improved neuronal function by enhancing short-term memory. Noting a similarity between the inattention and hyperactivity of emergence and ADHD itself, clinicians have started using guanfacine to manage young, healthy males who were commonly at risk for emergence delirium after anesthesia. In this context, the drug has gained popularity for its off label use perioperatively in a wide variety of patients with anxiety issues, known or predicted to have potential for combative or difficult emergence.

Compared to dexmedetomidine, guanfacine may have a more unique and specific mechanism of behavior modification that could be beneficial as a treatment in delirium. Furthermore, oral guanfacine is cheaper and easier to use, with the ability to continue it outside the ICU. From a pharmacokinetic standpoint, guanfacine is absorbed with peak onset over 1-4 hour and has a half-life of 16 hours. The long half-life allows once-daily dosing before sleep. Maximal drug levels at night promote sleep, with some drug remaining during the day to provide a lesser degree of sedation. Outpatient studies have detected a ceiling effect on the antihypertensive effect of guanfacine, wherein doses of 1 mg, 2 mg, or 3 mg all have the same effect on blood pressure. This implies that up-titrating the guanfacine dose beyond 1 mg daily might increase sedative/hypnotic effects, without increasing hemodynamic instability. Maldonado et al at Stanford has utilized guanfacine for delirious/withdrawing patients (0.5-3 mg total daily dose). A recent case report by Dr. Habib Srour and colleagues described successful use of guanfacine (1 mg q12hr) to control refractory agitation in an ICU patient with a history of opioid misuse.

The investigators propose to perform a pilot trial to evaluate protocol adherence, estimate recruitment rates, and evaluate the safety and efficacy of guanfacine with standard care, compared to standard care alone, on delirium in ICU patients. Before testing other drugs compared with guanfacine, evidence needs to be collected to investigate if guanfacine is more effective than placebo in treating delirium in ICU patients. The control intervention is therefore chosen to be placebo along with standard or usual care. Given the literature and our own experience with the drug for ICU delirium, the investigators plan to use a dose of 2 mg nightly for efficacy and minimization of side effects. The investigators will withhold guanfacine or placebo if a patient does not have delirium for four consecutive assessments or for safety reasons. The investigators will permanently discontinue guanfacine or placebo for any life-threatening, serious adverse event that was related to the intervention. The trial drug or placebo will be discontinued after the 14-day intervention period or at ICU discharge, whichever occurs first.