Surgical Anatomy and Evaluation of Patient for Thoracic Surgery

Thoracic Duct

It rises into the chest through the aortic hiatus and lies behind the esophagus in the right chest between the aorta and the azygous vein. It begins in the abdomen from the cisterna chyli at L2 in the midline. 

It passes through the aortic hiatus in the diaphragm running to the right of the aorta. The thoracic duct changes direction from right to left at the T4/T5 level and entering the posterior left mediastinum leaves the thoracic intake and ends at the internal jugular vein or subclavian vein intersection. The thoracic duct's primary job is to move fat, different proportions of protein, and lymphatic material. 

Fitness Assessment For Major Thoracic Surgery

The risk of perioperative cardiac event, risk of perioperative death, and third, perioperative dyspnea, are all included in the tripartite risk assessment approach that the British Thoracic Society recommends. 

Also Read: Anatomy Of The Lungs

Risk Of Perioperative Mortality

The thoracic surgery scoring system (Thoracoscore) is mostly used to evaluate it. The most popular scoring system is this one. Age, sex, ASA grade, performance status, operation priority, surgery extent, dyspnea score, malignant diagnosis, and composite comorbidity score are its nine variables.

Also Read: Pleura And Mediastinum 

Risk Of Perioperative Myocardial Event

Proceed with an ECG and clinical assessment. Seek for the risk elements.  Keep an eye out for any current cardiac conditions, such as heart failure, triple vessel disease, or angina.

UK national Institute for Health and Care Excellence (NICE) recommendations for assessing fitness for treatment with curative intent (including surgery).

Circulatory system operation. Evaluate cardiac functional capability and risk variables. Steer clear of surgery if MI occurs within 30 days.
In cases of stable angina, consider revascularization prior to surgery. If there are three or more risk factors, poor cardiac functional capacity, or an active cardiac condition, seek a review from a cardiologist. If there are two or fewer risk factors and good cardiac functional capacity, offer surgery. Talk to the patient about perioperative platelet therapy if they have a coronary stent.

Also Read: Rapid Acquisition Of Key Concepts- Cardiothoracic And Vascular Surgery

Risk Of Postoperative Dyspnea

A thorough assessment of the respiratory system.  Get an ABG, a chest X-ray, and an oxygen saturation test (unreliable). One crucial test is the pulmonary function test. It assesses the patient's response to treatment, the degree of lung disease, and their functional ability. One widely used technique for this is spirometry. It gauges the volume or flow rate—the amount or rate at which air can be inhaled or expelled. There are differences in values based on height, race, and gender. It can be stated as the expected percentage of the normal value or as an absolute value.  Differences exist in height, race, and gender. 

The ideal tidal volume, or the volume of air we inhale or exhale during regular breathing, is between 450 and 500 milliliters. Inspiratory reserve volume is the amount of excess air that is breathed with extra effort above the tidal volume. Inspiratory capacity is defined as tidal volume plus inspiratory reserve. The air that remains after the tidal volume has been exhaled is known as functional residual capacity (FRC). 

Expiratory reserve volume (ERV) is the amount of air that has expired above the tidal volume with exertion. Residual volume refers to the air that remains after ERV and FRC procedures.
ERV + RV = FRC
The maximum amount of air that can be exhaled following a voluntary maximal intake is known as vital capacity. TV plus IRV plus ERV equals vital capacity. Total lung capacity is equal to TV + IRV + ERV + VC.

Also Read: Knowing Venous Diseases and How to Treat Them

Other Parameters

PEFR

Peak expiratory flow rate is the highest flow rate that may be obtained when the maximal amount of force is applied during expiration. 

FEV1
Forced expiratory volume in one second is known as FEV1. 

FVC
The amount of air that may be forcefully shifted from a maximum inspiration to a maximum expiration is known as forced vital capacity, or FVC. 

 A patient with a FEV1 greater than 60% has good lung function. Also, there is little perioperative danger. Further testing is necessary for this patient if it is less than 60%. Post-operative projected FEV1 is one crucial extra test. The most crucial post-operative metric for determining pulmonary reserve is this one. The number of lung segments that can be resected is the basis for calculation. 

FEV1 (L)/FEV1 (%) x The amount of residual bronchopulmonary segment following surgery. Since PPO-FEV1 = 19-6/19 x X in L, 6BPS, FEV1 - XL. There is little perioperative danger and optimal function if the PPO-FEV1 ratio is 35–40%. If the perioperative risk is high (PPO-FEV1 < 30%).

Also Read: High Yield Cardiothoracic and Vascular Surgery Questions

Diffusion Capacity Of The Lung

The purpose of this test is to assess the lung's alveolar capillary surface area integrity for gas exchange or transfer. Another name for it is a transfer factor. To do this, carbon monoxide is used. This test measures the speed at which carbon monoxide molecules enter the alveolar space and attach to the red blood cells (RBCs) in the capillaries. It is performed as a single breath test and cannot be performed at the patient's bedside.

Determined by subtracting the expired air from the inspired air. Diffusion capacity will be decreased in emphysema patients due to alveolar wall damage. Patients with lung fibrosis will have less diffusion capacity due to thicker alveolar membranes. Diffusion capacity > 40–50% indicates an adequate function.  Higher perioperative risk if diffusion capacity is less than 40.

Exercise Testing

CPET (Cardiopulmonary Exercise Testing)

Patients with low diffusion capacity and low post-operative projected FEV1 are candidates for this procedure. Calculate heart rate, oxygen uptake per minute, and record ECG. Determine the maximum oxygen consumption (VO2) per minute. 

A satisfactory function is indicated if the VO2 is greater than 15 ml/kg/min. 11 to 15 ml/kg/min in the case of CPET suggests a higher risk of surgery. A CPET of less than 10 ml/kg/min suggests a high surgical risk. CT scanning is performed not just when spirometry results are normal, but also when a person appears impaired, exhibits respiratory distress, or exhibits dyspnea.

Shuttle Walk Test

A good function is indicated if the patient can walk for more than 400 meters.

Six-Minute Walk Test 

A good function is also indicated if the patient can walk more than 1000 ft in six minutes.

Sniff Test

Sniff test: It assesses any diaphragmatic movement that appears contradictory. Ultrasonography or fluoroscopy. Request that the patient sniff so you can watch how the diaphragm moves. The diaphragm will either contract or retract in response to the rise in thoracic pressure, or it may relocate downward. The diaphragm will exhibit paradoxical movement, as seen by the raised hemidiaphragm and visible diaphragm retraction on the other side. 

Hope you found this blog helpful for your Cardiothoracic and Vascular Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.