===== Hemodynamic Stability =====

**Hemodynamic stability** refers to the maintenance of adequate blood circulation and perfusion pressure to vital organs, particularly the brain, heart, and kidneys. It is a critical parameter during **perioperative care**, **critical illness**, and **trauma resuscitation**.

==== Key Parameters ====
Hemodynamic status is typically assessed by monitoring:

  * **Blood pressure (BP)**: systolic, diastolic, mean arterial pressure (MAP)
  * **Heart rate (HR) and rhythm**
  * **Cardiac output (CO) and stroke volume (SV)**
  * **Central venous pressure (CVP)**
  * **Peripheral perfusion**: capillary refill, skin temperature, lactate
  * **Urine output**: indirect marker of renal perfusion

==== Definitions ====
  * **Stable**: Adequate BP (MAP ≥ 65 mmHg), normal HR, good perfusion signs
  * **Unstable**: Hypotension (MAP < 60–65 mmHg), tachycardia or bradycardia, signs of hypoperfusion (oliguria, confusion, mottling)

==== Causes of Instability ====
  * **Hypovolemia**: hemorrhage, dehydration
  * **Cardiogenic**: myocardial infarction, arrhythmias
  * **Distributive**: sepsis, anaphylaxis
  * **Obstructive**: tension pneumothorax, cardiac tamponade, pulmonary embolism

==== Clinical Importance ====
  * Guides fluid therapy, vasopressor/inotrope use, and monitoring strategies
  * Essential for safe anesthesia and surgical outcomes
  * Unstable hemodynamics increase risk of **organ failure**, **stroke**, or **death**

==== Management Strategies ====
  * **Fluids**: crystalloids, colloids, blood products
  * **Vasopressors**: norepinephrine, phenylephrine, vasopressin
  * **Inotropes**: dobutamine, epinephrine
  * **Monitoring**: invasive BP, arterial line, echocardiography, advanced hemodynamic devices (e.g. PiCCO, FloTrac)

==== Example: Craniotomy and Hemodynamics ====
In neurosurgical patients:
  * Sudden increases in BP may raise **intracranial pressure (ICP)**
  * Scalp block or adequate analgesia helps maintain stability during craniotomy
  * Hypotension should be avoided to preserve cerebral perfusion pressure (CPP = MAP - ICP)