Blood transfusion may be required in the perioperative period for patients who have lost or actively losing blood. In order to manage this scenario, it is essential you know the patient’s circulating blood volume (based on their weight and age) and be able to estimate how much blood has been lost, which is not always straightforward, as some blood loss may be concealed. A blood loss of less than 10% of total blood volume does not usually require a transfusion; blood loss of greater 30% of total blood volume invariably requires transfusion.

Laboratory and/or point of care testing can be invaluable to guide to both blood transfusion and other blood components such as FFP platelets. Every hospital will have a major haemorrhage protocol.

There are many complications associated with blood transfusion including fever, hypothermia, circulatory overload and lung injury, immunological reactions, acid–base disturbances, hyperkalaemia and hypocalcaemia. In addition, infections may be transmitted such as HIV and hepatitis. Finally a serious error is to transfuse the wrong blood to a patient caused by errors including blood bottle mislabelling, or not checking the blood against the patient’s wristband.

Placenta previa is a common and potentially life-threatening complication of pregnancy. Transvaginal ultrasound is the best method for diagnosis, and delivery should be via cesarean delivery. Women with uncomplicated placenta previa should be delivered at 36–37 weeks. Antepartum bleeding is a common presentation, during which maternal stabilization is paramount, followed by a decision for delivery based on the maternal and fetal clinical statuses. Placenta previa is also a risk factor for placenta accreta syndrome and should be considered at time of delivery. Postpartum hemorrhage is also common in these deliveries, and various techniques can be employed to diminish the blood loss, including uterotonics, uterine artery embolization, intrauterine balloon, and hysterectomy. Proper identification of blood loss at every stage and proper utilization of blood products is essential to good outcomes.

Intravenous fluids are routinely given to children when the enteral route is not sufficient or it’s not an option, such as during surgery and anaesthesia. Lack of understanding of the composition of fluids and the appropriate rate to administer them has been associated with serious morbidity and mortality in children. Recent evidence has shown that giving children isotonic fluids with a sodium concentration similar to plasma decreases the risk of hyponatraemia without an increase in adverse effects. This has led to a change in guidelines, which now recommend that isotonic fluids are used in children along with regular monitoring of fluid balance and electrolytes. Current evidence supported by several anaesthesia societies across the world recommend that children are allowed and should be encouraged to drink clear fluids up to one hour before elective surgery. Evidence is starting to emerge from enhanced recovery programmes in children of improved outcomes from individualised perioperative fluid therapy and avoidance of prolonged preoperative fasting. Strategies to reduce blood transfusion in children having surgery include treatment of preoperative iron deficiency, acceptance of low transfusion thresholds, cell salvage and tranexamic acid administration.

Upper gastrointestinal bleeding (UGIB) is bleeding proximal to the ligament of Treitz (esophageal, gastric or duodenal source). More common than lower gastrointestinal bleeding (LGIB; approximately 70% of GIB). Most common cause is peptic ulcer disease. LGIB is bleeding distal to the ligament of Treitz. Lower gastrointestinal bleeding is less common than UGIB (approximately 30% of GIB). LGIB has lower mortality rate than UGIB. The most common cause is diverticular disease.

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

Overview of cardiac complicationsincluding arrhythimias, heart failure, acute coronary syndrome, disseminated intravascular coagulation, hyperviscosity syndrome, and pulmonary embolism

While great emergencies are fortunately rare and certainly devastating, the upside is that they are often accelerators of progress. Wars, pandemics, and emergencies have been catalysts for medical innovation out of necessity - a desperate attempt to compensate for the circumstances. They bend the trajectory of discovery in new directions and increase the rate at which certain medical discoveries are made. Chapter 16 is thus about how wars, outbreaks, and other emergencies influence the rate and direction of medical progress. It explores how both World Wars, the pandemic of 1918, and COVID-19 have altered the trajectory of discovery.