HeartSmartTM: A New Method of Assessing Hydration in Neurosurgical Patients
Warring-Davies, Kenneth J.
Bland, John M.
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Background: Maintenance of normal fluid homeostasis is challenging in neurosurgical patients. Consequently, we studied hydration assessment in neurosurgical intensive care patients. Methods: Pulmonary artery catheter thermodilution (PACTD) is the conventional method for measuring cardiac index (CI) and mean pulmonary artery occlusion (MPAOP) or wedge pressure (MPWP). We compared values from this technique with those derived from continuous cardiac dynamic monitoring (CCDM)-HeartSmart®, a new, less invasive, software-based technique. Over 4 years, we undertook an audit of 101 paired sets of data from 21 patients with sub-arachnoid hemorrhage who had pulmonary artery flotation catheters inserted as part of their treatment. Measured values of CI and MPWP were obtained retrospectively from patients’ charts and compared with values calculated using CCDM-HeartSmart® software. Results: Using the Bland-Altman method for comparing two measurement techniques, there was good agreement between measured and calculated MPWP (mean of differences –1.81, SD 3.97, SE 0.39, 95% CI –2.59 to 2.04 l/min/m2 ; two-sided p < 0.0001). The measured and calculated values of CI were also in good agreement (mean of differences 0.36, SD 1.30, SE 0.13, 95% CI 0.109 - 0.619; two-sided p = 0.0055, 95% limits of agreement –2.1 to 2.91 l/min/m2 ). This indicates that, when estimating CI and MPWP in critically ill neurosurgical patients, CCDM-HeartSmart® provides values close to those generated using PACTD. Conclusions: The CCDM-HeartSmart® could prove invaluable for optimizing response to fluid replacement and for guiding cardiovascular support in neurosurgical patients. This new, simple technology may help to facilitate routine adoption of perioperative optimization of blood flow using early goal-directed therapy.