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August 1, 2017 Circulation. 2017;136:e60–e122. DOI: 10.1161/CIR.0000000000000499 e88

6.2 Dehydration and Drugs: Recommendations

Syncope related to medication becomes prevalent particularly in older adults, who frequently have multiple comorbidities requiring treatment and are prone to polypharmacy effects.488–490 Cessation of offending medications is usually key for symptomatic improvement, but often feasibility of cessation of medications is limited by the necessity of the treatments.491–493 Dehydration may manifest along a spectrum of symptoms, ranging from tachycardia to shock, depending on whether a person has compensated or uncompensated hypovolemia.494 Orthostatic tolerance worsens with dehydration and is exacerbated by heat stress, which promotes vasodilation.495–497 Rehydration, whether by intravenous or oral formulation, should include sodium supplementation for more rapid recovery.21,498–501

Recommendations for Dehydration and Drugs

COR LOE Recommendations

I C-LD Fluid resuscitation via oral or intravenous bolus is recommended in patients with syncope due to acute dehydration.438,499,501–504

See Online Data Supplements 36 and 37. Fluid resuscitation is recommended for syncope secondary to both dehydration and exercise-associated hypotension. The latter is likely due to peripheral vasodilation and vasovagal physiology.438,495,504,505 Both dehydration and heat stress worsen orthostatic tolerance.495–497 Oral fluid bolus may require less volume than intravenous fluid infusion to have a similar treatment effect because oral fluid loading has a pressor effect.398,438,440–444,502 Beverages with increased sodium concentration (closer to normal body osmolality) rehydrate faster than beverages with lower sodium concentration or increased osmolality (eg, because of glucose content).498–501,503,506

IIa B-NR Reducing or withdrawing medications that may cause hypotension can be beneficial in selected patients with syncope.488–490,492,507–510

See Online Data Supplements 36 and 37. Syncope is a commonly reported adverse drug reaction, often resulting in hospital admission.488,489 The prevalence of medication-related syncope appears higher in older patients.491,492,507,510 Several drug classes have been implicated in syncope, including diuretics, vasodilators, venodilators, negative chronotropes, and sedatives.488–490,492,507–510 Close supervision during adjustment of medications is frequently required because of potential worsening of preexisting supine hypertension or cardiac arrhythmias.491–493,511 Other factors to consider include frailty, HF and/or cardiac dysfunction, and the use of a large number of medications causing adverse effects because of drug-drug interactions.488,507,511–513

IIa C-LD In selected patients with syncope due to dehydration, it is reasonable to encourage increased salt and fluid intake.396,498–501,503

See Online Data Supplements 36 and 37. In patients with dehydration, sodium supplementation improves plasma volume and improves orthostatic tolerance.396,499,503 This additional dietary sodium may be provided as sodium tablets or sodium already dissolved in beverages.396,498–500,503 Higher-sodiumcontent beverages with osmolality comparable to normal body osmolality may rehydrate faster than lower-sodium-content beverages.498–501,503 This treatment option is not appropriate for patients with cardiac dysfunction or HF, uncontrolled hypertension, or chronic kidney disease.19

7 ORTHOSTATIC INTOLERANCE

Orthostatic intolerance is a general term referring to frequent, recurrent, or persistent symptoms that develop upon standing (usually with a change in position from sitting or lying to an upright position) and are relieved by sitting or lying.38 Most commonly, the symptoms include lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, exercise intolerance, and fatigue. These symptoms may be accompanied by hemodynamic disturbances, including blood pressure decrease, which may or may not meet criteria for OH, and heart rate increase, which may be inadequate or compensatory.38 The pathophysiology is quite varied. One condition of note is POTS, in which upright posture results in an apparently inappropriate tachycardia, usually with heart rates >120 bpm.24 Although syncope occurs in patients with POTS, it is relatively infrequent, and there is little evidence that the syncope is due to POTS.24,514 Treatments that improve symptoms of POTS might decrease the occurrence of syncope, although this is unknown.24,514–523 For further guidance on the management of POTS, we refer readers to the HRS consensus statement.24

8 PSEUDOSYNCOPE: RECOMMENDATIONS

Psychogenic pseudosyncope is a syndrome of apparent loss of consciousness occurring in the absence of impaired cerebral perfusion or function. Psychogenic pseudosyncope is believed to be a conversion disorder—in essence, an external somatic manifestation or response to internal psychological stresses. It is an involuntary response and should not be confused with malingering or Munchausen syndrome. Psychogenic pseudosyncope and pseudoseizures may be the same condition. The clinical distinction between the two is based on whether prominent jerky muscle movements simulating seizure activity are reported by witnesses. In the absence of associated jerky movements, the patient is likely to be referred for evaluation of syncope.30,229,524 Psychogenic pseudosyncope does not

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