TSRA Content:
Author: Anna Minasyan, MD, MSC
This is a revision and update from the previous edition of the TSRA Primer in Cardiothoracic Surgery written by Clayton Kaiser, MD and Zachary Brewer, MD
Overview
Postoperative bleeding is the bane of CT surgery. While a certain rate of operative re-exploration for bleeding is inevitable regardless of the amount of care taken, determining the amount of bleeding that is "acceptable" to close the chest is rugged.
Systemic heparinization (300-400 units/kg), platelet dysfunction due to CPB, and direct manipulation of high-pressure arteries create a perfect environment for excessive bleeding. Thus, one or more chest tubes are left in the mediastinum after every on-pump case to evacuate blood and prevent cardiac tamponade.
This chapter will discuss common pitfalls and strategies to handle postoperative bleeding.
The first question every cardiac surgeon should ask during the surgery is ¨When to close the chest¨?
As a resident, you must often independently determine when bleeding is low enough to close the chest. There is no magic formula here; with experience, these judgments become easier. For example, younger trainees may be surprised when the attending or senior resident closes the chest despite what might seem to be a high amount of active bleeding at the time of closure, and yet no postoperative issues follow. Conversely, one may re-explore a patient 3-4 hours after thinking there was hardly any bleeding at closure. One key to this decision is determining the difference between surgical and medical bleeding.
Surgical bleeding requires a direct operative intervention; medical bleeding requires correction of coagulopathy. Medical bleeding should not prohibit chest closure except on rare occasions. An effective strategy in a patient with medical bleeding is to close the sternum. During this period, pro coagulation agents (FFP, platelets, cryoprecipitate) should be administrated, and chest tube output should be monitored in OR for 10 to 15 minutes. The surgeon may gauge the likely hourly output and decide if it is necessary to re-open and search for a source of bleeding or take the patient to the ICU.
When the patient cannot tolerate sternal closure, the chest can be left open with a Silastic mesh sewn to the skin to cover the mediastinum. Chest tube output is monitored closely and replaced hourly, with the patient returning to the OR for re-exploration the next day.
The "take-back for bleeding" is one of the most common complications in cardiac surgery and is frequently the result of either a displaced clip from the internal mammary artery (IMA), soft tissue, vascular bleeding from the IMA bed, or disruption of the aortotomy closure. More frequently, no obvious source of bleeding is identified. In this setting, evacuation of the retained hematoma aids in correcting the local consumptive coagulopathy.
Transient bleeding from a sternal wire site is another frequent cause of significant postoperative bleeding. To prevent this, it is important to carefully inspect the wire exit sites on the underside of the sternum prior to closure. Electrocautery is often ineffective in stopping bleeding from wire sites. However, if the bleeding stops when the wire is pulled taught from both ends, the pressure on the wire after closure will likely control bleeding. A more effective approach is placing a figure of eight absorbable sutures around the wire exit site.
Post-Op Chest Tube Output
How Much Is Too Much? The trend and consistency of the chest tube output are more informative than the isolated volume output. A standard guideline is that chest tube output greater than 200 cc per hour generally requires re-exploration. However, by no means is this a hard and fast rule. For example, a healthy patient with normal coagulation and 220 cc per hour of thick, bloody chest tube output following a straightforward operation likely will need re-exploration. On the other hand, if a patient has undergone redo-sternotomy for a total arch replacement under hypothermic circulatory arrest with 340 minutes of cardiopulmonary bypass, 500-600 cc per hour output is tolerable.
Correcting the Coagulopathy
Before administrating blood clothing products, chest tubes should be checked for patency and gently milked, as ongoing drainage with occluded tubes leads to tamponade. The patient should be warmed to 37°C, as hypothermia impairs platelet function and suppresses the coagulation cascade. Hypertension, agitation, and shivering should be controlled, as they can potentially worsen bleeding. Microvascular bleeding can be reduced by increasing positive end-expiratory pressure on ventilator settings. However, this should be done cautiously, as PEEP impairs venous return to the heart and can put traction in the LIMA graft. The following paragraph lists the basics for monitoring the postoperative coagulation profile.
ACT - An elevated ACT suggests a problem with the intrinsic coagulation cascade or persistent heparin effect. If ACT > 130 in the setting of postoperative bleeding, additional protamine should be given.
PTT - Similar to ACT, an elevated PTT can suggest a problem with the intrinsic coagulation pathway or persistent heparin effect. If PTT > 1.5x NL, protamine should be given.
PT /INR - An elevated PT /INR suggests the need for clotting agents and can be improved by giving fresh frozen plasma (FFP). Product administration should always be given to treat the patient's clinical condition. If the first post-op INR is 2.1, but the patient is not excessively bleeding, FFP is probably unnecessary.