Comparison Between NICOM-Cheetah and Flotrac-Vigileo for Cardiac Output Monitoring.

Cardiac output (CO) monitoring is an important tool in critically ill patients with haemodynamic instability. Traditionally, this has been accomplished using the pulmonary artery catheter (PAC). However, its use has been associated with various complications such as pneumothorax, arrhythmia, infection, pulmonary valve injury and embolism. This has led to the development of various minimally invasive cardiac output monitoring devices such as the oesophageal Doppler, PiCCO®, NiCCO® and FloTrac®. These devices however have their inherent limitations and though minimally invasive, are still not without risks to the patient. More recently a completely non-invasive CO monitoring device, NICOM Cheetah® has been introduced. Its use is based on thoracic bioreactance and it involves placement of 4 electrodes on either side of the thorax and it analyses changes in the phase of electrical voltage signal to the current applied across the thorax. Initial validation studies on the NICOM Cheetah® device revealed promising results. This study intends to compare cardiac output monitoring capabilities of the NICOM Cheetah® device using the FloTrac® CO monitor as a reference.

This will be a single centre prospective observational study. 50 consecutive patients admitted to the surgical intensive care unit (SICU) who are deemed to require cardiac output monitoring by the treating intensivist will be studied. Data collection is planned to be carried out over 2 consecutive years. Inclusion criteria are: 1) Patients who are deemed to require cardiac output monitoring. 2) Patients 21 years old and above. 3) American Society of Anesthesiologist (ASA) physical status 1 to 4. Exclusion criteria are: 1) Patients who are not on mechanical ventilation. 2) Patients who are not in sinus rhythm. 3) Patients with allergy to adhesive tapes. Patients will be treated as per department protocols and no additional intervention will be performed. Each patient will have an arterial catheter inserted as per our usual practice. All patients will have the FloTrac® connected to the arterial catheter (standard of care in CGH SICU) and the NICOM Cheetah® electrodes placed on the skin across the anterior thoracic wall. The FloTrac CO monitor is the current standard of care for cardiac output monitoring in the SICU of CGH. All patients deemed to require cardiac output monitoring will receive the FloTrac (as per departmental practice). The NICOM CO monitor involves the application of non-invasive sensor strips. In this study, it will be applied to patients receiving the FloTrac (standard of care), on top of the standard care of monitoring with Flotrac. For each patient, standard demographic and SICU data (age, gender, comorbidities, ASA score, admission diagnosis, type of surgery, cause of haemodynamic instability, mean arterial pressure (MAP) and central venous pressure (CVP) at the time of instituting cardiac output (CO) monitoring, use of inotropic support, presence of renal replacement therapy, presence of mechanical ventilation and APACHE II score) will be collected. Cardiac Index (CI) values simultaneously recorded by the NICOM Cheetah® and FloTrac® on a 15-minutely basis for the first 10-hour period will also be collected. These data will be automatically recorded by the FloTrac® Vigilance monitor and the Cheetah NICOM monitor and transcribed to a data entering/analysis software by the principal and co-principal investigators for data analysis.

Eligibility Criteria:
Inclusion Criteria:

* Patients who are deemed to require cardiac output monitoring.
* Patients 21 years old and above
* American Society of Anesthesiologist (ASA) physical status 1 to 4

Exclusion Criteria:

* Patients who are not on mechanical ventilation.
* Patients who are not in sinus rhythm.
* Patients with allergy to adhesive tapes