Correlation of Pulse oximetry with SOFA scores for evaluation of tissue perfusion in emergency surgery patients

Abstract

Introduction - Worldwide, every year, millions of people require emergency abdominal surgeries, which are urgent and time-critical to treat high-mortality diseases. Post-operatively, patients require continuous monitoring of the vitals and early diagnosis of post-operative complications and management for suitable outcomes of the patient. Pulse oximetry is a noninvasive method of monitoring a person’s oxygen saturation.
Physiologic compensatory mechanisms such as peripheral vasoconstriction limit the use of heart rate and blood pressure measurement as indicators for mild central tissue hypoperfusion and hypoxia in early settings. Hypotension is a late marker of hypoperfusion and almost 30% of circulatory volume may be lost before hypotension occurs. Therefore, early recognition of tissue hypoperfusion and hypoxia before the onset of tachycardia or hypotension is of prime importance in the prevention of hypoperfusion and hypoxia-induced organ failure.
AIM - Serial correlation between SpO2, perfusion index and SOFA score both preoperatively and post-operatively with the ultimate outcome of the patient.
Method - A total of 48 patients requiring emergency abdominal surgery of non-traumatic cause were considered. Vital parameters were assessed and documented. Blood samples were collected under aseptic conditions and deposited in the hospital lab. ABG was done using an ion-selective electrode in an ABG analyzer. SOFA scores of individual patients were calculated.
In our study, patients with uneventful recovery had a mean pre-operative SpO2 value of 95.75% and SOFA score value of 1.5 and post-operative value 97% and 1.13, respectively. On the other hand, patients who died (n = 7) in the post-operative period had mean pre-operative SpO2 values of 87.71% and SOFA scores of 7.29 and post-operative values of 86.57% and 13.71, respectively, at the end of 72 hours.
Result - Preoperatively, compared to uneventful recovery, the mean SOFA score was significantly high in patients who require reservoir bag (p ≤0.001), invasive ventilation (p = 0.028), only ionotropic support (p <0.001), ionotropic support plus ventilation (p <0.001), requiring renal replacement therapy (p <0.001) and in patients who died (p <0.001).
Preoperatively, compared to uneventful recovery, mean SpO2 was significantly low in patients who require reservoir bag (p = 0.002), invasive ventilation (p = 0.003), only ionotropic support (p = 0.003), ionotropic support plus ventilation (p = 0.003), required renal replacement therapy (p <0.001) and in patients who died (p <0.001).
Post-operatively, the mean SOFA score, compared to uneventful recovery, was significantly high in patients who require reservoir bag, invasive ventilation, only ionotropic support, ionotropic support plus ventilation, required renal replacement therapy and in patients who died.
Conclusion - Pulse oximetry is widely used for monitoring peripheral oxygen saturation (SaO2). By alerting the surgeon about the onset of hypoxemia or diminished perfusion, pulse oximetry can lead to the rapid institution of supportive treatment even before organ dysfunction begins to happen. Derangements of pulse oximetry parameters will occur several before the SOFA score is raised. Therefore, on the basis of pulse oximetry findings, quick corrective measures can be undertaken to prevent possible serious complications.
Physiologic compensatory mechanisms such as peripheral vasoconstriction limit the use of heart rate and blood pressure measurement as indicators for mild central tissue hypoperfusion and hypoxia in early settings. Hypotension is a late marker of hypoperfusion and almost 30% of circulatory volume may be lost before hypotension occurs. Therefore, early recognition of tissue hypoperfusion and hypoxia before the onset of tachycardia or hypotension is of prime importance in the prevention of hypoperfusion and hypoxia-induced organ failure.

In the pathophysiology of sepsis-generated organ dysfunction, the basic flaw lies in poor tissue perfusion and cellular oxygenation.
This sets off the cascade of metabolic and biochemical events which leads to organ dysfunction after a few hours or days. The key
to successful management of such patients lies in controlling the sepsis source and the earliest possible recognition of perfusion
and oxygenation deficit before organ dysfunction starts to take place.