In the early 1950’s, Prof. William Wellesley Mapleson from University of Wales, Cardiff, classified the several breathing systems around depending on what components they contained and what position they took in the system. Magill system (Mapleson A) The Mapleson A or Magill system is good for spontaneous breathing patients, so […]

Mapleson Systems

This is a valve which allows the exhaled gases and excess FGF to leave the breathing system It does not allow room air to enter the breathing system.

APL Valve

Anesthetic gas exits the anesthesia machine via the common gas outlet to enter the breathing circuit. The function of the circuit is 1) To deliver oxygen and anesthetic gases to the patient 2) To eliminate carbon dioxide. The Carbon dioxide may be eliminated by gas inflow or by Soda lime […]

Breathing Circuits

Overview of Pneumonia —Pneumonia is an inflammation of the lungs caused by infection. Initial diagnosis is usually based on clinical findings and chest x-ray . Causes, symptoms, treatment, preventive measures, and prognosis differ depending on whether the infection is bacterial, viral, fungal, or parasitic; whether it is acquired in the […]

Pneumonia in the immunocompromised

According to The American-European Consensus Conference Committee 1994 to 2012 The Acute Respiratory Distress Syndrome (ARDS) was defined as  Acute onset of respiratory failure . Bilateral infiltrates on chest radiograph . Hypoxemia as defined by a PaO2/FIO2 ratio <200 mmHg . With  no evidence of left arterial hypertension or pulmonary capillary pressure <18mmHg to rule out cardiogenic […]


Hypovolemic (decreased preload) • Causes: o 3rd spacing o Inadequate intraop fluid replacement (esp. bowel prep/abd surgeries) o Bleeding (+/- significant blood loss) o Sympathetic blockade (spinal/epidural) o Increased capillary permeability (sepsis, burns, transfusion related lung injury) • Treatment: usually responsive to fluid administration Cardiogenic (intrinsic pump failure) • Causes: […]

Acute Post Operative Hypotension

Hyponatremia is an important and common electrolyte abnormality that can be seen as isolated problem  or, as most often as a complication of other medical illnesses (eg, heart failure, liver failure, renal failure, pneumonia). The normal serum sodium level is 135-145 mEq/L. Hyponatremia is defined as a serum sodium level of […]


Serum Osmolality Sodium (Na): mmol/L (optional) Potassium (K): mmol/L BUN: mg/dl Glucose: mg/dl Serum Osmolality = mOsm/kg Normal Range = 285 – 295 mOsm/kg Serum Osmolality = (2 x (Na + K)) + (BUN / 2.8) + (glucose / 18) Created by: Charles Hu & Gary Barnas M.D. Created: Saturday, […]

Serum Osmolality

Tetanus is caused by a neurotoxin released by Clostridium tetani, a spore-forming anaerobic bacterium. It occurs throughout the world and remains an important cause of death with an estimated annual mortality of 800 000–1 000 000. Over half of these deaths are in neonates. Tetanus is a clinical diagnosis. Individuals with symptoms and signs […]


In healthy adults the normal PO2 is 80-100 mmHg . Hypoxemia can be defined as diminished amount of oxygen in the arterial blood, shown by decreased partial pressure of oxygen (PO2) and reduced saturation in arterial blood sample . PO2 values less than 80 mmHg is considered hypoxemia, however, with advancing age […]


Halothane is a halogenated alkane a colourless liquid with a relatively pleasant smell. It is decomposed by light. The addition of 0.01% thymol and storage in amber colored bottles keep it stable. Although it is decomposed by soda lime, it may be used safely with this mixture. It corrodes metals […]


In theory second gas effect phenomenon should speed the onset of anesthetic induction. Because nitrous oxide is insoluble in blood, its rapid absorption from alveoli results in an abrupt rise in the alveolar concentration of the accompanying volatile anesthetic. However, even at high concentrations (70%) of nitrous oxide, this effect accounts […]

Second gas effect