Intraoperative hypotension: position, perfusion and decisions
A drop in pressure requires attention to the number and understanding its context. The surgical position, anesthesia, and timing of the procedure can combine different mechanisms. This reading connects our scientific publication with the evidence and with our pages on prone, beach chair, and post-arrest care.
All intraoperative hypotension is not created equal - Position the sixth phenotype
Diego Escarramán Martínez; Manuel A. Guerrero Gutiérrez; Gerardo A. Solís-Pérez; Jorge M. Antolinez-Mota; Arturo Vázquez Peralta; Rafael Herrera-Elizalde. J Clin Anesth. 2023;88:111128.
The surgical position as a dimension that deserves attention. Our letter proposes considering the patient's position as a sixth phenotype of hypotension. It discusses changes in venous return and mechanical factors. It is a physiological and editorial proposal; it does not validate a diagnostic classification nor demonstrate that a positional intervention improves outcomes for all patients.
Consult original publication ↗Why is this topic part of REASEL?
Recognizing deterioration also belongs to perioperative preparation. Hypotension and cardiac arrest are distinct situations. Understanding the first helps organize patient assessment and connect scenarios we have already addressed: changes in position, resuscitation under special conditions, and continuity after ROSC. This page organizes consultable knowledge; it does not present a validated therapeutic sequence.
Three questions to read the problem
What are we measuring?
The quality, method, and context of measurement matter.
What changed?
Induction, bleeding, position, or evolution of the procedure.
How does it evolve?
A single value does not describe the entire clinical trajectory.
Editorial reading map. It is not a diagnostic algorithm nor a mandatory treatment sequence.
The same value can accompany different mechanisms.
POQI 2024 recommends directing treatment to the presumed causes, which may coexist. These categories help organize interpretation; they do not automatically assign a drug or a volume load.
Vasodilation
Vascular tone may change. The drop in pressure alone does not identify a decrease in blood volume.
Hypovolemia
Circulating volume is another dimension. It must be interpreted along with the context, including bleeding, and not deduced exclusively from the pressure.
Bradycardia
Heart rate also plays a role. The rhythm and its temporal relationship with deterioration are part of the assessment.
Low cardiac output
Function and flow require context. Recovering a pressure alone does not demonstrate normalization of all perfusion variables.
Position is part of the hemodynamic context.
Prone and beach chair connect this reading with special situations. Our letter describes how positioning can affect venous return and how abdominal compression may contribute to deterioration in the prone position. Effects depend on supports, technique, patient, and procedure; not every position causes the same change. Physiological data on gravity in healthy volunteers do not equate to clinical outcomes in anesthetized patients.
Checking the position is part of reasoning. It does not replace the search for other causes nor does it turn a postural change into a universal maneuver.
Anesthetic induction: avoid a single explanation
Propofol can modify more than one circulatory component. De Wit and colleagues studied cardiac output, venous return, and resistances during anesthesia with propofol. Saugel and colleagues observed mechanisms after induction with sufentanil, propofol, and rocuronium. These studies help discuss physiology; they do not allow attributing all hypotension to myocardial depression or automatically choosing a treatment for a different patient.
Pressure targets: read recommendations and trials together
A general recommendation does not constitute an individual guarantee. POQI 2024 recommends maintaining a mean arterial pressure of at least 60 mmHg in at-risk patients and considers higher targets when venous or compartment pressures are elevated. This recommendation does not define a threshold that ensures protection of all organs in every scenario.
What IMPROVE-multi (2025) adds
It did not demonstrate superiority of the individualized strategy studied. In high-risk adults undergoing major abdominal surgery, the trial compared targets based on previous nighttime mean pressure with routine management aimed at a mean pressure of 65 mmHg or more. It did not reduce the primary composite outcome of acute kidney injury, acute myocardial injury, non-fatal cardiac arrest, or death at seven days. It does not demonstrate equivalence nor that hypotension can be ignored.
Deepen with our Substacks
Physiology, decisions, and perioperative context. Scientific publications and their limits remain the foundation; Substacks expand the discussion. Full access depends on the conditions of each publication.
Propofol and hypotension
Pump, circuit, and mechanisms. A reading to discuss what changes during induction without reducing the entire explanation to a single mechanism.
Read on Substack ↗Venous return without mythology
Volume, pressure and context. Conceptual deepening on venous return. It does not constitute a fluid protocol nor demonstrate a clinical outcome.
Read on Substack ↗The heart does not push pressure: it delivers energy
A perspective to discuss physiology. Supplementary reading of a narrative review. The editorial title does not replace the assessment of pressure, flow, and perfusion.
Read on Substack ↗There is no more ephedrine. Now what?
The choice of vasopressor requires context. Supplement on perioperative pharmacology; no automatic substitution between drugs is proposed nor are doses reproduced here.
Read on Substack ↗Cardiac arrest doesn’t wait for you to lower the beach chair.
Preparation for a different scenario. Connects hemodynamic deterioration with the organization of the response when a cardiac arrest occurs in a non-supine position.
Read on Substack ↗Can I keep operating? The forgotten link of intraoperative cardiac arrest
After ROSC, evaluation continues. Reflection on the surgical decision and the patient’s destination for ongoing care. These questions are not a validated scale.
Read on Substack ↗Continue in our clinical library
Scientific sources and scope
- All intraoperative hypotension is not created equal - Position the sixth phenotype ↗
Own letter/comment. Full text of two pages cross-checked in Zotero. Proposes a positional phenotype; it is neither a diagnostic validation nor an outcomes trial.
- POQI international consensus statement on perioperative arterial pressure management (2024) ↗
2024 International Consensus. Reference for presumed causes and general pressure recommendations; maintains its conditions of application.
- The effect of propofol on haemodynamics (2016) ↗
Physiological study on propofol and hemodynamics. The indexed abstract was verified; its results do not become a universal therapeutic rule.
- Mechanisms contributing to hypotension after anesthetic induction (2022) ↗
Observational study of induction with a specific anesthetic combination. It does not isolate all effects of a single drug.
- Individualized Perioperative Blood Pressure Management — IMPROVE-multi (2025) ↗
Randomized trial IMPROVE-multi. Population, comparator and primary outcome were matched in the indexed abstract. Results from supplements not verified are not attributed.
- Adaptation of Systemic and Pulmonary Circulation to Acute Changes in Gravity and Body Position (2019) ↗
Physiological study in eight healthy male volunteers with changes in gravity and position. Does not study surgery outcomes nor validate the proposed phenotype.
- Energy, flow and pressure in the cardiovascular system: a narrative review (2026) ↗
Narrative review of physiology. Complementary conceptual framework; this is not a trial demonstrating the efficacy of a therapeutic strategy.
REASEL educational synthesis for health professionals. Accompanies the original sources and does not replace complete guidelines, individual assessment, or decisions of the treating team. Selection of mechanisms and questions is editorial; it is not a validated algorithm. Sources reviewed on October 23, 2026.