EVALUATION OF RELATIONSHIP BETWEEN ARTERIAL BLOOD PRESSURE CHANGES AND INDICES OF PULSE OXYMETRIC PLETHYSMOGRAM
Abstract
Introduction: Pulse oxymetry has been used as a standard and assential perioperative and intensive care unit Monitoring. this device also displays a particular pulse wave known as finger plethysmography. In a previous study the effects of minimal blood volume reduction on the appearance of plethysmogram have been evaluated as a change in delta - down component of this wave and in this way they concluded that the pulse oxymetric plethysmography can be used as an indicator of hypovolemia.
Although in that study the blood pressure remained unchanged, however hypovolemia may be associated with some degree of hypotension. The hypotension perse may be due to different factors including hypovolemia, pump problems, vasodilation etc. Since the effects of hypotension on plethysmogram have not been described clearly, the value of delta-down changes for detection of hypovolemia can not be ascertained definitely. This study was carried out to evaluate the effects of hypotension on indices pulse oxymetric plethysmography on a sample of adult patients undergoing general Anesthesia with controlled hypotension.
Method & Materials: Thirty three ASAI adult patients eschaduled electively for mastoidectomy requiring Induced hypotension to a mean blood pressure of 60 mmHg with sodium Nitroprosside infusion were included in the study. Various indices of plethysmogram were correlated to different levels of blood pressure using linear regression analysis.
Results: Delta-down and VSV of plethysmogram were correlated significantly with systoloc blood pressure. Other Indices were not correlated with blood pressure.
Discussion: In this study the effect of hypotension on pulse oxymetric plethysmography has been evaluated with the result similar to the effects of hypovolemia on the plethysmogram. It can be concluded that in the presence of pharmacologic hypotension, coexisting hypovolemia can not be detected with the plethysmographic wave changes such as delta-down.
Although in that study the blood pressure remained unchanged, however hypovolemia may be associated with some degree of hypotension. The hypotension perse may be due to different factors including hypovolemia, pump problems, vasodilation etc. Since the effects of hypotension on plethysmogram have not been described clearly, the value of delta-down changes for detection of hypovolemia can not be ascertained definitely. This study was carried out to evaluate the effects of hypotension on indices pulse oxymetric plethysmography on a sample of adult patients undergoing general Anesthesia with controlled hypotension.
Method & Materials: Thirty three ASAI adult patients eschaduled electively for mastoidectomy requiring Induced hypotension to a mean blood pressure of 60 mmHg with sodium Nitroprosside infusion were included in the study. Various indices of plethysmogram were correlated to different levels of blood pressure using linear regression analysis.
Results: Delta-down and VSV of plethysmogram were correlated significantly with systoloc blood pressure. Other Indices were not correlated with blood pressure.
Discussion: In this study the effect of hypotension on pulse oxymetric plethysmography has been evaluated with the result similar to the effects of hypovolemia on the plethysmogram. It can be concluded that in the presence of pharmacologic hypotension, coexisting hypovolemia can not be detected with the plethysmographic wave changes such as delta-down.