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Resuscitative Endpoints

Introduction

Resuscitative endpoints can be categorised into three hierarchical levels:

1. Basic endpoints–macroscopic vital signs and simple outputs such as blood pressure, heart rate, urine output and mentation.
2. Macrohaemodynamic targets–functional assessments of cardiac performance and preload responsiveness (e.g., cardiac index, dynamic preload indices).
3. Microcirculatory and perfusion targets–measures of global tissue perfusion (e.g., lactate, central venous oxygen saturation, veno‑arterial CO₂ gap) and regional perfusion (e.g., near‑infrared spectroscopy, sublingual capnometry).

Basic Endpoints

Blood Pressure

• Advantages: readily available via non‑invasive or invasive methods; provides continuous waveform monitoring; low cost.
• Limitations: non‑invasive oscillometric measurements may be unreliable in patients with significant vasodilatation; systemic arterial pressure does not directly reflect tissue flow; individualised mean arterial pressure (MAP) targets (e.g., permissive hypotension in haemorrhage) may be required.

Heart Rate and Shock Index

• Heart Rate: easily measured and continuous but affected by medications, autonomic tone, pain and arrhythmias.
• Shock Index (SI = HR/SBP): SI values >0.9 are associated with significant haemodynamic instability, need for massive transfusion and higher mortality.
• Limitations: influenced by confounders such as beta‑blockade, atrial fibrillation and pacemakers; cannot guide therapy in isolation.

Urine Output

• Advantages: simple indicator of renal perfusion; widely available.
• Limitations: intermittent and delayed; affected by diuretics and chronic renal dysfunction; oliguria may not indicate ongoing shock if renal autoregulation is intact

Mentation

• Altered consciousness suggests cerebral hypoperfusion but is confounded by sedation, intoxication and neurological injury.

Macrohaemodynamic Targets

Preload Responsiveness

• Static variables (e.g., central venous pressure, pulmonary artery occlusion pressure) have poor predictive value for fluid responsiveness and are not recommended as sole guides.
• Dynamic variables reliably predict response to fluid loading in mechanically ventilated patients:
  • Pulse Pressure Variation (PPV): thresholds >13% predict fluid responsiveness.
  • Stroke Volume Variation (SVV): thresholds >10–12% predictive.
  • Plethysmographic Variability Index (PVI): also useful in selected settings.
  • Passive Leg Raise (PLR) Test: an increase in stroke volume or cardiac index ≥10% during PLR indicates fluid responsiveness without administering fluid.
  • End‑Expiratory Occlusion Test: a transient increase in cardiac output during a 15‑second ventilator hold suggests preload dependence.

Cardiac Output

• Aim for a cardiac index between 2.2 and 4.0 L min⁻¹ m⁻² in the perioperative and critical care setting

Microcirculatory and Perfusion Targets

Global Perfusion

• Central Venous Oxygen Saturation (ScvO₂) reflects the balance between oxygen delivery and consumption; target ScvO₂ >70% though not central in recent sepsis bundles favouring lactate clearance.
• Lactate levels >2 mmol L⁻¹ indicate hyperlactataemia; aim for ≥10% reduction within 2 h of resuscitation onset.
• Base Deficit stratification (mild 2–5 mmol L⁻¹, moderate 6–14 mmol L⁻¹, severe >15 mmol L⁻¹) correlates with shock severity and resuscitation requirements.
• Venous–Arterial PCO₂ Gap (ΔPCO₂): difference between central/mixed venous and arterial PCO₂; values >6 mmHg suggest inadequate flow and are associated with worse outcomes.

Regional Perfusion

• Sublingual Capnometry: elevated tissue CO₂ relative to arterial CO₂ indicates local hypoperfusion.
• Near‑Infrared Spectroscopy (NIRS): measured at the thenar eminence or other sites; persistent tissue oxygen saturation (StO₂) <75% and attenuated occlusion/reperfusion slopes are linked to adverse outcomes in shock.
• Sidestream Dark Field (SDF) Microscopy: research tool visualising sublingual capillary flow; target >80% perfused vessels in experimental protocols.

Goal‑Directed Therapy Algorithm for Major Surgery

1. Baseline optimisation: ensure SpO₂ ≥94%; haemoglobin ≥80 g L⁻¹; normothermia (temperature ≥36 °C).
2. Assess fluid responsiveness using PPV, SVV, PVI or PLR:
   • If preload responsive, administer 250–500 mL crystalloid boluses and reassess.
3. Evaluate cardiac index:
   • If <2.2 L min⁻¹ m⁻², consider inotropic support.
4. Maintain MAP ≥65 mmHg with vasopressors as required.
5. Monitor global and regional perfusion indices, repeating the cycle as patient condition evolves.

Links

• Resus end targets in shock
• Polytrauma and haemorrhagic shock
• Maternal sepsis
• Inotropes
• Infection and antibiotics
• Acute Respiratory Distress Syndrome (ARDS)
• Lactate

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References:

1. Englehart, M. S. and Schreiber, M. A. (2006). Measurement of acid–base resuscitation endpoints: lactate, base deficit, bicarbonate or what?. Current Opinion in Critical Care, 12(6), 569-574. https://doi.org/10.1097/mcc.0b013e328010ba4f
2. Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Intensive Care Med. 2021;47(11):1181–1247.
3. Monnet X, Marik PE, Teboul JL. Prediction of fluid responsiveness. What’s new? Ann Intensive Care. 2022;12:44.
4. Veiga‑Fernandes AI, Mesquita PS, de Assis FM, et al. Assessment of fluid responsiveness using pulse pressure variation and other dynamic indices: a systematic review and meta‑analysis. Crit Care. 2024;28(1):50.
5. Monnet X, Teboul JL. Passive leg raising for the prediction of fluid responsiveness: five rules. Crit Care. 2017;21(1):18.
6. American College of Surgeons Committee on Trauma. Advanced Trauma Life Support Student Course Manual. 10th ed. Chicago, IL; 2018.
7. Dubin A, Pozo MO. Venous minus arterial carbon dioxide gradients in the monitoring of tissue perfusion and oxygenation: a narrative review. Medicina. 2023;59(7):1262.
8. Varis V, Rinne R, Kreivanen J, et al. Near‑infrared spectroscopy in adult circulatory shock: a systematic review. Crit Care. 2025;29:125.
9. End point of resuscitation. FCA Part II Anaesthetic Refresher Course 2013: University of the Witwatersrand Dr Ahmad Alli.
10. Connelly CR, Schreiber MA. Endpoints in resuscitation. Curr Opin Crit Care. 2015 Dec;21(6):512-9. doi: 10.1097/MCC.0000000000000248. PMID: 26418760.

Summaries:

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© 2025 Francois Uys. All Rights Reserved.

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