Features of Oxygen Extraction Ratio and Temperature Homeostasis during Early Postoperative Period after Major Abdominal Surgery

In some situations, tissue hypoxia may exist despite normal values obtained by conventional haemodynamic monitoring such as arterial blood pressure, central venous pressure, heart rate, and urine output. The study was performed in early postoperative period after major abdominal surgery in 160 patients and was conducted in the following stages: 1admission from operating room; 2 in 1-3 hours; 3 4-7 hours; 4 8-12 hours; 5 after 13-24 hours after the surgery. Depend on rate of oxygen extraction index (ERO2) patients was divided in four groups depending on ERO2 on admission: group 1 (n=44) low ERO2 (< 21%) followed by recovery to normal levels to stage 2-3 (ERO2 = 22-32%), group 2 (n=42) normal level ERO2 (22-32%) in all the stages, group 3 (n=40) high levels ERO2 (>33%) with recovery to normal levels to stage 2, group 4 (n=34) high ERO2 (> 35%) in all the stages. Central hemodynamic, gas exchange, metabolic rate and temperature parameters were assessed. Maintaining an adequate tissue oxygenation is the cornerstone of metabolic response and postoperative recovery in patient after major abdominal surgery. Oxygen extraction index at admission to ICU after surgery can be normal (26.25% of patients), reduced (27.5% of patients) or high (46.25% of patients). When oxygen extraction ratio is reduced metabolic recovery occurs classically after 4-7 hours; when ERO2 is elevated after 8-12 hours. For patients with high oxygen extraction ratio marked venous hypoxemia is typical, which recovery to 4-12 hours post-surgery. Core temperature improvement is connected with the restoration of oxygen homeostasis. So, under normal and reduced ERO2 even mild central hypothermia after surgery were not observed, and at an elevated ERO2 moderate hypothermia after surgery was observed with only to 4-7 hours post-surgery restoration. Research Article Features of Oxygen Extraction Ratio and Temperature Homeostasis during Early Postoperative Period after Major Abdominal Surgery Musaeva TS Kuban State Medical University, Russia, Krasnodar, Russia Dates: Received: 27 December, 2016; Accepted: 11 January, 2017; Published: 19 January, 2017 *Corresponding author: Musaeva TS, Assistant of Anesthesiology, Intensive Care and Transfusiology Department, Kuban State Medical University, Krasnodar, Russia, Tel. +78612224845, E-mail: https://www.peertechz.com


Introduction
About 100 years ago, the German physiologist Pfl üger stated that the cardio-respiratory system fulfi ls its physiological task by guaranteeing cellular oxygen supply and removing waste products of cellular metabolism. In his opinion, everything else is of secondary importance: arterial oxygen content, arterial pressures, blood fl ow velocity, mode of cardiac work, and mode of respiration, all are incidental and subordinate; they all combine their actions only in service to the cells. Although the modern technology of the 21st century, we are mostly monitoring parameters which Pfl üger called "unanticipated and dependent", insuffi cient lighting oxygen homeostasis complex changes, particularly during and after major surgery. medicine. The aim of cardiovascular monitoring is the early recognition of impending tissue hypoxia. In some situations, tissue hypoxia may exist despite normal values obtained by conventional haemodynamic monitoring such as arterial blood pressure, central venous pressure, heart rate, and urine output [1][2][3].
That is why we think it is important to establish a particular change of oxygen, temperature homeostasis and central hemodynamics after major abdominal surgery under combined epidural anesthesia.

Materials and Methods
Prospective study examined 160 patients who underwent major abdominal surgery over a 12-month period from Patients were eligible if they were planned for major surgery, could give informed consent, and did not have disseminated cancer disease. We excluded the pregnant or lactating women, chronic lung disease, septic shock and major bleeding. The trial was approved by the ethical committees of Kuban State Medical University.
Statistical analysis was performed using Friedman test and Kruskal -Wallis test by Statistica 6. Data are presented as medians and percentiles (p25 and p75).

Results
Variety of hemodynamic, microcirculation and blood gas changes during the major surgery are occurred. As listed in Table 1 group 1 had normal core temperature, mild tachycardia, normal parameters of systemic hemodynamics, moderate, not much pronounced decline of oxygen delivery, consumption and oxygen extraction index, supranormal oxygen tension in the arterial blood and its normal tension in the venous blood.
Statistically signifi cant differences between groups in terms of DO 2 and VO 2 and PaO 2 were not observed. We should also mention the main differences between the other groups. In groups 3 and 4 pronounced disorders of temperature homeostasis, increased oxygen extraction index and reduced SvO 2 , compared with group 2 were observed,  In the other groups tendency of stabilization of systemic hemodynamics (stroke index and cardiac index) was observed, although vascular tone remained higher than in group 1. In the groups 3 and 4 central hypothermia was remained; in group 3oxygen extraction index returned to normal ranges, and group 4 -continued to grow.
Within 4-7 hours after the surgery (Table 2) in group 1 stable normal state of homeostasis was remained. In group 2 -high system vascular resistance was persisted. In group 3 -central temperature recovery and improvement of systemic hemodynamics was observed. The group 4 the core temperature was normal, but a steady decline of venous oxygen saturation, reduced delivery and increased oxygen consumption was observed.
Within 13-24 hours after surgery in group 1 normal homeostatic function were remained. In group 2 all patient homeostatic parameters were observed with maintaining vasoconstriction as a result of decrease in oxygen delivery.
In group 3 reduced oxygen consumption and low oxygen extraction ratio were remained Table 3.
Our data show that the postoperative period might be associated with a reduction or elevation in tissue ability to extract oxygen.
Restoration of global oxygen delivery is an important goal in early resuscitation as tissue hypoxia may exist despite normal values obtained by conventional hemodynamic monitoring.

Conclusion
Maintaining an adequate tissue oxygenation is the cornerstone of metabolic response and postoperative recovery in patient after major abdominal surgery. Oxygen extraction index at admission to ICU after surgery can be normal (26.25% of patients), reduced (27.5% of patients) or high (46.25% of patients). When oxygen extraction ratio is reduced metabolic recovery occurs classically after 4-7 hours; when ERO 2 is elevated -after 8-12 hours. For patients with high oxygen extraction ratio marked venous hypoxemia is typical, which recovery to 4-12 hours post-surgery.
Core temperature improvement is connected with the restoration of oxygen homeostasis. So, under normal and reduced ERO 2 even mild central hypothermia after surgery were not observed, and at an elevated ERO 2 moderate hypothermia after surgery was observed with only to 4-7 hours post-surgery restoration.