pCO 2 gap (central venous-arterial carbon dioxide difference) as a guide to adequacy of fluid resuscitation in postoperative high risk surgical patients and prediction of prognosis

BACKGOUND

The high mortality due to circulatory shock necessitate the need for early biomarkers to assess

tissue perfusion which could provide important information about prognosis and help guide

resuscitation efforts. The PCO 2  gap is difference between partial pressure of CO 2  in venous blood

(PvCO 2 ) and arterial blood (PaCO2)as blood lactate and venous oxygen saturation (SvO2) are

commonly used but it has many limitations .Raised pCO2 gap has been recognized as a marker

of poor outcome during circulatory shock and it should therefore be part of our clinical

evaluation to guide fluid administration in the early phases of resuscitation. An increase in

pCO2 gap(PcvCO2- PaCO2) >6mm of Hg suggests a shock that may be responsive to fluid

resuscitation. We aim to calculate pCO2 gap in postoperative high risk patients as it will aide as

a guide to adequacy of resuscitation and outcome of such patients.

Aims and objectives

Primary objective

1.To access the correlation of pCO 2 with adequacy of fluid resuscitation in postoperative high

risk surgical patients

2. To access correlation of pCO 2 gap (central venous-arterial carbon dioxide difference) with

fluid resuscitation in postoperative high risk surgical patients

Secondary objectives

1. Comparing pCO2 gap with serum lactate levels, SvO2 levels

2. Correlation of pCO 2 with 28 day mortality in postoperative high risk surgical patients

Patients and Methods

In post operative period following high risk surgery, patients who are in shock and mechanical

ventilation, arterial blood gas will be done to evaluate pCO 2 , lactate, pO 2 , and simultaneous

central venous sample to evaluate the same will be done at onset of shock, following fluid

resuscitation, 2hrs, 6 hrs, 24 hours. The PCO 2 gap will be calculated by the difference between

central venous partial pressure of carbon dioxide and arterial partial pressure of carbon dioxide. ,

routine laboratory tests were obtained by intermittent blood sampling immediately after

admission At ICU admission, data on demographics (age, sex, weight), type of surgical

procedure, Simplified Acute Physiology Score (SAPS) II, and inotropic support will be recorded

in all patients. The study population will be divided into two groups according to fluid

responsiveness. The pCO2, Central and arterial CO2 gaps, SVO2 and lactate level will be

accessed pre and post fluid resuscitation. Postoperative complications will be defined in

accordance with defined criteria until hospital discharge or death as follows: postoperative sepsis

(pneumonia, intraperitoneal abscess, wound infection, peritonitis and urinary tract infection),

acute renal and cardiac failures, postoperative hemorrhage, ischemic events, and postoperative

mortality. Patients will be followed up till hospital discharge or death.