Respired Gases in Patients Post Cardiac Surgery

Summary

Certain diseases relating to the heart can only be definitively treated with surgery. When untreated, these can lead to heart failure with a lack of supply of oxygen-rich blood to the tissues, leading to damage to other organs.

Adults who undergo heart surgery vary greatly in terms of age and relative health. This has significant implications when predicting outcomes in the aftermath of surgery. For example, a 90-year-old man with a variety of comorbidities such as diabetes and high cholesterol who requires a heart valve replacement may have an unfavourable chance of surviving the postoperative period when compared to an 18-year-old woman with no significant medical history undergoing the same procedure.

Almost invariably, patients are admitted to an Intensive Care Unit (ICU) following heart surgery. This is done to facilitate close monitoring of the patients' vital organ functions and to also provide organ support if needed. For the heart, this can include the administration of drugs to help a heart pump forcibly, cause blood vessels to contract and increase blood pressure. Patients who have undergone heart surgery have been placed on a mechanical ventilator, following a tube placed in their windpipe. This form of ventilation often continues in ICU for a period of time, depending on the patient's condition.

One specific type of ICU level monitoring that occurs in patients who have undergone heart surgery is cardiac output monitoring. This involves a thin tube, called a pulmonary artery catheter, that extends from the skin to the heart, via large blood vessels. Cardiac output monitoring is essential in this patient group to guide organ support and to provide information of how well the heart is functioning.

In this observational study, the investigators wish to study patients who have undergone cardiac surgery, are receiving mechanical ventilation and have pulmonary artery catheters inserted. The investigators will collect cardiopulmonary data in these patients and compare these data with values of exhaled and inhaled gases (oxygen and carbon dioxide) over the same time period. This will enable the investigators to investigate the link between cardiopulmonary data and respired gas values.

A better understanding of this link between cardiopulmonary function and oxygen/carbon dioxide values will then inform future studies aiming to determine the effect of various interventions in similar patient groups.

Conditions

• Critically Ill
• Cardiac Disease
• Mitral Valve Disease

Interventions

OTHER

Data collection using the Optical Gas Analyser

To allow the OGA to acquire certain physiological data during the study it will be necessary to slightly vary the tension of oxygen and carbon dioxide for short periods. The changes involved will be of a lesser magnitude than those often seen due to natural variation over time in critically ill patients. The FiO2 will be increased by around 20% from baseline for several minutes; this is a far more modest increase than is seen with the practice of pre-oxygenation - a transitory increase in fraction of inspired oxygen ( FiO2) to 100% - performed regularly in ICU patients to make certain routine interventions safer. The end-tidal CO2 level will also briefly (1-2 min) be altered by around 1 kPa by transient adjustment of the ventilator settings.

Sponsors & Collaborators

• University of Oxford

  lead OTHER

Principal Investigators

• Peter A Robbins, MBBS DPhil · University of Oxford

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2022-10-30

Primary Completion

2024-12-10

Completion

2025-03-01

Countries

• United Kingdom

Study Locations