Intratracheal milrinone in severe ards increases stroke volume assessed by carotid doppler and the fick principle but not thermodilution

SESSION TITLE: Critical Care Global Case Report Posters 1 SESSION TYPE: Global Case Reports PRESENTED ON: 10/10/2023 12:00 pm - 12:45 pm INTRODUCTION: Determining stroke volume change (SV∆) is important. SV can be measured from a pulmonary catheter (PAC) via both thermodilution (TD) and the indirect Fick (IF) method; furthermore, novel metics from the carotid artery Doppler pulse (e.g., the corrected flow time (ccFT)) may serve as SV surrogates. We describe a patient with ARDS and refractory end-organ hypo-perfusion who received intratracheal (IT) instillation of milrinone while monitored by both a PAC and a wireless, wearable Doppler ultrasound system worn over the common carotid artery. CASE PRESENTATION: 63-year-old man with COVID and severe cardiomyopathy and AKI developed shock and progressive respiratory failure requiring mechanical ventilation. Point of care ultrasound revealed moderate RV dysfunction and severe LV dysfunction. A trial of intra-tracheal milrinone was done to determine if pulmonary vasodilator therapy may be beneficial.Prior to instillation of IT milrinone: heart rate (HR) 118 beats per minute (bpm), blood pressure of 107/61 (pulse pressure 46) with a mean arterial pressure (MAP) of 75 mmHg. Pulmonary artery systolic, diastolic and mean pressures of 61, 39 and 46 mmHg, respectively. Cardiac output by TD was 5.2 L/min and SV was 44 mL/beat. Central venous oxygen saturation was 67% and arterial oxygen saturation was 94% giving a calculated indirect Fick cardiac output of 6.5 L/min and SV of 55 mL/beat. Prior to IT milrinone the mean ccFT was 269 milliseconds. 10 minutes following instillation of IT milrinone: HR 119 bpm, MAP of 128/68 (pulse pressure 60, +30%) with a mean arterial pressure of 85 mmHg (+13%). Pulmonary artery systolic, diastolic and mean pressures of 66, 40 and 49 mmHg, respectively. Cardiac output by TD was 5.2 L/min and SV was 44 mL/beat. Central venous oxygen saturation was 72% and arterial oxygen saturation was 89% giving a calculated Fick cardiac output of 10.3 L/min (+58%) and SV of 87 mL/beat (+58%); the mean ccFT was 331 milliseconds (+23%). DISCUSSION: From the PAC, SV can be obtained via TD as well via the IF principle; from the wearable Doppler ultrasound, the ccFT is used as a surrogate for SV. Previously, we have shown that the slope correlating ccFT∆ and SV∆ intimates that the observed +23% ccFT∆ approximates a +55% SV∆, which is consistent with the Fick calculation (i.e., +58% SV∆), but not TD (i.e., no change). Also supporting increased SV were the clinically-significant increases in MAP and systemic pulse pressure by +13% and +30%, respectively, following IT milrinone. Reasons for discrepancy between TD and IF are manifold and include: assumptions about oxygen consumption, presence of intra-cardiac shunt, tricuspid regurgitation (TR), vena cava backwards flow (VCBF) and TD technique (e.g., volume, temperature and timing of the saline injection). VCBF is common during mechanical ventilation and can cause cardiac output underestimation by TD by blunting of the temperature-time curve; this effect could have played a role here given the patient's reduced RV function and mechanical ventilation. CONCLUSIONS: The reference standard for SV∆ in the ICU is elusive as there are caveats for both TD and IF. Novel, non-invasive technologies may offer useful SV∆ surrogates. REFERENCE #1: Fares WH, Blanchard SK, Stouffer GA, Chang PP, Rosamond WD, Ford HJ, Aris RM. Thermodilution and Fick cardiac outputs differ: impact on pulmonary hypertension evaluation. Can Respir J. 2012 Jul-Aug;19(4):261-6. REFERENCE #2: Kenny JS, Barjaktarevic I, Mackenzie DC, Elfarnawany M, Yang Z, Eibl AM, Eibl JK, Kim CH, Johnson BD. Carotid Doppler ultrasonography correlates with stroke volume in a human model of hypovolaemia and resuscitation: analysis of 48 570 cardiac cycles. Br J Anaesth. 2021 Aug;127(2):e60-e63. REFERENCE #3: Jullien T, Valtier B, Hongnat JM, Dubourg O, Bourdarias JP, Jardin F. Incidence of tricuspid regurgitation and vena caval backward flow in mechanically ventilated patients. A color Doppler and contrast echocardiographic study. Chest. 1995 Feb;107(2):488-93 DISCLOSURES: No relevant relationships by Korbin Haycock Owner/Founder relationship with Flosonics Medical Please note: 2018-present Added 02/07/2023 by Jon-Emile Kenny, source=Web Response, value=Ownership interest No relevant relationships by Philippe Rola