55 year old female a known case of thryotoxicosis in control posted for abdomino perinea] resection during surgery there was sudden drop in B.P., and end tidal CO2 decreased from 40 to 10 mmHg. On auscultation there was a mill wheel murmur, what is the diagnosis aEUR'
Air embolism [Ref Lee Synopsis of Anaesthesia 12rh/e p. 2741 Presence of Mill wheel murmur and decrease in End tidal CO2 during surgery suggests Air enzbolism:- "If air enters the vein in sufficient amount, it will go to the right hea and lung causing on air-lock obstruction in the pulmonary aery. This may result in a found continuous precordial murmur, the so called "Mill wheel murmur". Two conditions must exist for venous air embolism to occur : - A direct communication between a source of air and the vasculature and - A pressure gradient ouring the passage of air into the circulation. Air embolism can occur whenever a blood vessel is open and a pressure gradient exists ouring entry of gas. Because the pressure in most aeries and veins is greater than atmospheric pressure an air embolus does not always happen when a blood vessel is injured. In the veins above the hea, such as in the head and neck, the pressure is less than atmospheric and an injury may let air in. This is one reason why surgeons must be paicularly careful when operating on the brain. The key factors determining the degree of morbidity and moality in venous air emboli are ? The volume of the gas entrapped. The rate of accumulation and The patient's position at the time of event. Generally small amounts of air are broken up in the capillary bed and absorbed from the circulation without producing symptoms. Traditionally it has been estimated that more than 5 ml/kg of air displaced into the intravenous space is required for significant injury (shock or cardiac arrest to occu). It a large amount of air gets lodged in the hea; it stops the flow of the blood from the right ventricle to the lungs. This results in significant rise in pulmonary aery pressures. This increase in pulmonary aery pressures can lead to right ventricular outflow obstruction and fuher compromise pulmonary venous return to the left hea. The diminished pulmonary venous return will lead to decreased left ventricular preload with resultant decreased cardiac output and eventual systemic cardiovascular collapse. In patients with patent foramen ovale the air entrapped can travel to the left side of the hea and on to the brain or coronary aeries. This can lead to most serious of air embolism symptoms. Diagnosis Dopple ultrasounddeg is the most sensitive noninvasive method to detect air embolism. Transesophageal echocardiography is more sensitive than Doppler ultrasound but is also more invasivedeg and technically more difficult to place and to interpret. The pulmonary aery catheter is the next most sensitive monitor. Mass spectrometry.for end tidal nitrogen is as sensitive as the pulmonary aery catheter. End tidal carbon di-oxide measurement decreases during air embolism. - But decrease in ETCO2 is not specific for air embolism. Hypoventilatiorz, low cardiac output, other types of emboli and COPD can also decrease ETCO2. The least sensitive method to detect air embolism is the precordial or esophageal stethoscope. On stethoscope - "mill wheel murmur" is detected Clinical signs of Air embolism Abrupt fall in end tidal CO2 is usually the first sign Hypotension Tachycardia Cyanosis Mill wheel murmur Cardiovascular collapse
Thyroid storm
Bleeding
Hypoxia
Air embolism