Monitoring of Organ Perfusion: Integrating PI, PPV, and SVV in Critical Care and Surgical Settings: A Narrative Review Volume 62- Issue 2

Macjones Mawunyo Semeko and Zhiming Zhang*

• Department of Anesthesiology, The First People’s Hospital of Chenzhou, The Affiliated Chenzhou Hosipital, Hengyang Medical School, University of South China, Chenzhou, Hunan, 423000, China

Received: April 20, 2025; Published: July 01, 2025

*Corresponding author: Zhiming Zhang, Department of Anesthesiology, The First People’s Hospital of Chenzhou, The Affiliated Chenzhou Hosipital, Hengyang Medical School, University of South China, Chenzhou, Hunan, 423000, China

DOI: 10.26717/BJSTR.2025.62.009726

Abstract PDF

Organ perfusion (OP) underpins physiological viability, requiring precise monitoring in high-risk settings. This review synthesizes evidence on OP indicators (Plethysmographic Index/PI, Pulse Pressure Variation/PPV), emphasizing their utility during anesthesia and surgery. Key findings highlight PI’s role as a non-invasive perfusion marker, modifiable by arterial catheterization techniques (e.g., flush temperature) and pharmacological agents (e.g., lidocaine-heparin interactions). Limitations include PI variability due to motion artifacts and insufficient data on vasoactive drug synergies. Future work should standardize PI acquisition protocols and explore real-time multimodal analytics. Integrating PI with dynamic measures (PPV/SVV) offers a robust framework for guiding fluid management, vasopressor use, and anticoagulant therapy, ultimately reducing perioperative ischemic complications.

Keywords: Organ Perfusion; Plethysmographic Index (PI); Hemodynamic Monitoring; Arterial Cannulation; Perfusion Pharmacology; Critical Care Outcomes

Abbreviations: OP: Organ Perfusion; SVV: Stroke Volume Variation; PPV: Pulse Pressure Variation; PI: Plethysmographic Index

Organ perfusion (OP) refers to the process by which blood circulates through the vascular system to supply oxygen and nutrients to tissues and organs [1]. This critical process is essential for maintaining the physiological function of all tissues, including the heart, brain, kidneys, and other vital organs [2]. Proper perfusion ensures that tissues receive sufficient oxygen to meet metabolic demands and removes metabolic waste products. If perfusion is inadequate, cells may become ischemic, leading to tissue damage and potentially organ failure [3]. In clinical practice, monitoring OP is crucial, especially in patients undergoing surgeries or those with critical illnesses, where perfusion might be compromised due to various factors like shock, cardiac arrest, or vascular disease [4]. It becomes particularly important during procedures like arterial catheterization, where maintaining optimal OP is necessary to ensure accurate monitoring of hemodynamic parameters [5]. Several factors can influence OP, including blood pressure, vascular resistance, blood volume, and the health of the vascular endothelium. In surgical settings, OP can be influenced by anesthesia, the use of vasodilators or vasoconstrictors, and medications such as anticoagulants [6]. The measurement of OP can be challenging due to the complexities involved in accurately assessing blood flow in real-time. For this reason, a variety of indicators and technologies, including the Plethysmographic Index (PI), Pulse Pressure Variation (PPV), and Stroke Volume Variation (SVV), are used to assess OP in critically ill patients [7].

Various internal and external factors influence organ perfusion, including physiological conditions, medical treatments, and surgical interventions. These factors can either enhance or reduce blood flow to organs, affecting the accuracy of OP monitoring and the effectiveness of therapeutic interventions [8]. Hemodynamic factors, such as blood pressure, cardiac output, and vascular resistance, are the primary determinants of organ perfusion. Low blood pressure, for example, can significantly impair blood flow to organs, particularly during surgery or in shock situations. On the other hand, high blood pressure may cause excessive vascular stress, leading to endothelial damage and reduced perfusion [9]. In addition, vascular tone plays a critical role in regulating organ perfusion. Conditions that lead to vasodilation or vasoconstriction, such as the use of certain medications or the onset of inflammation, can influence blood flow. Vasodilators, like nitroglycerin, are often used to treat conditions of reduced perfusion by relaxing blood vessel walls, whereas vasoconstrictors like norepinephrine may be administered in cases of severe hypotension to restore blood pressure and perfusion [10]. Temperature also has a profound effect on perfusion. Hypothermia, for instance, causes vasoconstriction, limiting blood flow to peripheral organs and tissues. Conversely, hyperthermia can cause vasodilation, which may increase blood flow but can also put stress on the cardiovascular system [11].

Medications, particularly those used in anesthesia and critical care, can also affect OP. For instance, heparin, an anticoagulant, is commonly used to prevent blood clots during surgical procedures, while lidocaine, a local anesthetic, can induce vasodilation and may influence vascular tone (Figure 1). The combined effect of these medications on organ perfusion remains an area of ongoing research, as their interactions may have clinical implications for patient care [12].

Figure 1

In critically ill patients or those undergoing surgery, accurate monitoring of organ perfusion is essential for managing patient outcomes. To assess OP, various indicators are used, including the Plethysmographic Index (PI), Pulse Pressure Variation (PPV), and Stroke Volume Variation (SVV). These indicators help clinicians evaluate the effectiveness of interventions and make informed decisions regarding patient management [13]. The Plethysmographic Index (PI) is a non-invasive measure that reflects the strength of peripheral blood flow. It is commonly obtained using a pulse oximeter, which measures the variation in blood volume in peripheral tissues. A low PI value can indicate poor perfusion or low cardiac output, while a high PI value typically signifies better perfusion. PI is particularly useful for monitoring changes in perfusion during surgeries, as it is sensitive to variations in blood flow [14]. Pulse Pressure Variation (PPV) and Stroke Volume Variation (SVV) are dynamic measures that assess the fluctuations in pulse pressure and stroke volume, respectively, during the respiratory cycle. These variations can provide valuable insights into a patient’s volume status and cardiovascular stability. High PPV or SVV values may indicate insufficient fluid resuscitation, while low values could suggest stable hemodynamics [15].

These indicators are often used in conjunction to provide a more comprehensive picture of OP, particularly in critically ill patients who are at risk of hemodynamic instability. They can help guide treatment decisions such as fluid administration, vasopressor use, and the management of anesthesia during surgery [16] (Table 1).

Table 1: Organ Perfusion Monitoring Indicators (PI, PPV, SVV) Comparison.

The Plethysmographic Index (PI) plays an essential role in assessing organ perfusion, particularly in clinical settings where accurate real-time data is critical. As a non-invasive measure of peripheral blood flow, PI can serve as an early warning signal of reduced perfusion, enabling healthcare providers to make timely interventions before the patient’s condition worsens [17]. PI monitoring is commonly used in patients undergoing major surgeries, including cardiac, vascular, and orthopedic procedures, where blood flow may be compromised due to anesthesia, surgical manipulation, or blood loss. It is also employed in critical care settings to monitor patients in shock, as well as in those undergoing long-term mechanical ventilation [18]. By continuously assessing PI, clinicians can gauge the efficacy of interventions aimed at improving perfusion, such as fluid administration, vasopressor therapy, and changes in the patient’s position [19]. Clinical studies have shown that decreased PI values can be indicative of impaired perfusion and may correlate with adverse outcomes, such as tissue hypoxia and organ failure [20]. For example, low PI values in cardiac surgery patients have been associated with poor myocardial perfusion and increased risk of postoperative complications.

Conversely, increased PI values have been linked to improved vascular tone and better perfusion, particularly in patients receiving appropriate fluid resuscitation and vasopressor therapy [21]. While PI is a valuable indicator of peripheral perfusion, it is important to consider its limitations. For instance, PI values may be influenced by external factors such as sensor placement, ambient temperature, and the patient’s skin tone, which could affect the accuracy of readings [22]. Additionally, PI may not always accurately reflect perfusion in certain organs, such as the brain or kidneys, which are more dependent on central hemodynamics. Thus, PI should be used in conjunction with other monitoring tools and clinical assessments to provide a more comprehensive evaluation of organ perfusion [23] (Table 2).

Table 2: Role of Plethysmographic Index in Organ Perfusion Monitoring.

Arterial cannulation is a common procedure performed to monitor blood pressure, obtain blood samples, and facilitate the administration of medications in critically ill patients. However, the process of inserting an arterial catheter can potentially affect PI measurements, as it may influence blood flow and vascular tone in the catheterized artery [24]. The insertion of an arterial catheter can cause local trauma to the vessel, leading to vascular spasm or increased resistance, which may temporarily alter the PI value. Additionally, the presence of the catheter itself may impede normal blood flow, particularly if the catheter is placed in a small or sensitive artery, such as the radial artery. These changes can result in lower PI values, potentially confounding the interpretation of perfusion status [25]. The flush of the arterial line with room temperature heparin solution is another factor that may influence PI readings. Arterial flush is typically performed to maintain patency of the catheter and prevent blood clotting. However, flushing with room temperature saline or heparin may cause vasodilation or vasoconstriction, depending on the volume and temperature of the solution used. This may lead to transient changes in blood flow and affect the PI value [26].

Studies have shown that temperature and composition of flush solutions can impact vascular tone, and researchers have explored ways to minimize the effects of flush solutions on PI readings. One approach has been the use of warm saline or heparin solutions, which are believed to cause less vasoconstriction than room temperature solutions. This practice is intended to reduce the impact of the flush on vascular tone and preserve more accurate PI readings during arterial catheterization [27].

Lidocaine is a widely used local anesthetic known for its ability to block sodium channels and inhibit nerve conduction. However, lidocaine also has a vasodilatory effect on blood vessels, which may influence vascular tone and blood flow, particularly in small arteries and veins. This vasodilatory effect may play a role in enhancing organ perfusion, especially in combination with anticoagulants like heparin [28]. The vasodilation induced by lidocaine can decrease vascular resistance, thereby improving blood flow and potentially increasing perfusion to tissues. This effect is particularly important during procedures like arterial catheterization, where ensuring adequate perfusion is critical for accurate monitoring of hemodynamics. Lidocaine may also enhance the effects of heparin by promoting better circulation through the catheterized artery, potentially improving the effectiveness of anticoagulation and reducing the risk of clot formation [29]. Research on the combined use of lidocaine and heparin is still limited, and further studies are needed to fully understand their synergistic effects on organ perfusion and vascular tone. However, early findings suggest that this combination may offer benefits in improving blood flow and minimizing complications during critical care interventions [30].

Despite advancements in OP monitoring, significant limitations persist: PI Variability: PI values are influenced by extrinsic factors (sensor placement, ambient temperature, skin pigmentation) and intrinsic factors (vascular tone, medication effects), reducing reproducibility across diverse populations. Dynamic Measures (PPV/SVV): Respiratory variation-based metrics (PPV/SVV) lose reliability in arrhythmias, spontaneous breathing, or low tidal volume ventilation. Drug Interactions: The combined effects of heparin and lidocaine on vascular tone and perfusion lack robust clinical validation, with most evidence derived from small-scale studies. Cannulation Artifacts: Arterial catheterization may alter local hemodynamics, and flush solutions (temperature/volume) can transiently distort PI readings. Organ-Specific Gaps: PI primarily reflects peripheral perfusion, with limited correlation to central organ perfusion (e.g., renal/splanchnic).

Future directions for OP research and clinical integration should include: 1st AI-driven integration of PI with PPV/SVV for intraoperative decision support. 2nd RCTs on temperature-controlled heparin flush solutions to minimize PI artifact. 3rd Pharmacodynamic studies of lidocaine-heparin dosing for catheter-related vasospasm.

Organ perfusion is a cornerstone of physiological integrity, with its monitoring pivotal in critical care and surgery. PI, PPV, and SVV provide valuable, non-invasive insights into perfusion status, yet their clinical utility requires contextual interpretation alongside hemodynamic and pharmacological variables. Arterial cannulation and adjunctive medications (e.g., heparin-lidocaine) demonstrate both therapeutic potential and confounding effects on perfusion metrics. Addressing current limitations—through standardized protocols, advanced technology, and rigorous drug-interaction studies—will refine OP assessment and intervention strategies. Ultimately, a multimodal approach to perfusion monitoring promises to reduce ischemic complications, guide resuscitation, and improve organ-specific outcomes in high-risk patients.

This work was supported by the General Program of the Medical and Health Science and Technology Development Research Center, National Health Commission (Grant No. WKZX2024CX301203) and the Medical Research Fund of Hunan Medical Association (No. HMA202101004).

All authors agree the publication of this article, and there was no conflicting of interest.

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