Richard Arbour, BSN, CCNS, CCRN, CNS
Critical Care Clinical Nurse Specialist
Temple University Hospital
Philadelphia, Pennsylvania
Disclosure information not submitted.
Title: Ventilator Autotriggering Consequent to Stroke Volume and Recoil with Veno-arterial ECMO
Case Report Body
Introduction: Ventilator autotriggering risks auto-PEEP, alters intrathoracic pressures, interferes with flow during mechanical circulatory support (MCS) and confounds brain death testing. MCS flow, recoil and cardiac stroke volume may cause pressure/flow waveform artifacts. Ventilator autotriggering caused by MCS/cardiac stroke volume and sensitive ventilator trigger mode/sensitivity may be mistaken for intrinsic respiratory drive, inappropriately treated with sedative/hypnotics or neuromuscular blockade (NMB) and delay brain death testing with implications for patient/family care, resource utilization and organ donation.
Description: A 32-year-old patient was admitted to the Cardiac ICU (CICU) postoperatively following aortic repair surgery. He experienced severe hemorrhage and hypotension for which he received copious blood product and clotting factor administration. Postoperatively he required veno-arterial ECMO. He received controlled ventilation and required multiple inotropic and vasoactive agents in addition to MCS to maintain cardiac output. On transfer his pupils were pinpoint and sluggishly and he maintained a minimal cough reflex. He received sedation/analgesia and NMB. By ICU day 3, his pupils were fixed/dilated and midpoint, necessitating neurological evaluation. NMB followed by sedation/analgesia were discontinued. He overbreathed ventilator set rate, delaying brain death testing. He had an unchanged flaccid, areflexic neurological examination and likely severe brain injury. Ventilator graphics analysis revealed pressure and flow waveform oscillations matching stroke volume/MCS artifact. Ventilator settings were changed from flow trigger at 3 L/min to pressure trigger at a threshold of -2 cm H20, eliminating autotriggering and delay in formal brain death testing. He was pronounced dead by neurologic criteria and medically unsuitable for organ donation. Physiologic support was discontinued following family dialogue.
Discussion: Autotriggering consequent to MCS/stroke volume assist may go unrecognized, and erroneously delay brain death testing. When patients are encountered as described, immediate evaluation of ventilator graphics in context with clinical history and neurological evaluation should be performed and appropriate adjustments made to ventilator triggering mode and sensitivity.