Transport of oxygen is one of the most important functions of blood. How oxygen moves from the air, where its partial pressure is about 150 mm Hg to mitochondria, where it drops down to a single digit is an evolutionary marvel. In this article, we discuss the physiology of oxygen transport from the alveoli to the tissue, the alveolar gas equation and the oxyhemoglobin dissociation curve. In the applied physiology section, we discuss the impact of high altitude, hyperbaric conditions, carbon monoxide poisoning on the transport of oxygen. Some common pitfalls in the interpretation of pulse oximetry and arterial blood gas are also discussed. Finally, we talk about the methods of increasing oxygen delivery, the compensation for hypoxia and some indications of venous oxygen saturation measurement.
Anemia of multifactorial etiology is common among critically ill patients and several arbitrary transfusion thresholds have been proposed. Transfusion of red blood cells has been well established to increase morbidity and even mortality among critically ill patients. Several randomized controlled studies have evaluated the use of a restrictive compared to a more liberal transfusion strategy in the critically ill. A transfusion threshold of 7 g/dL appears to be generally safe, especially in the younger age group without significant comorbidities. Besides, a restrictive transfusion strategy reduces the incidence of transfusion-related complications. However, the decision to transfuse needs to be individualized depending on the clinical situation, balancing putative benefits against possible complications.
Clotting catastrophies are rarely encountered challenges in the Intensive Care Unit (ICU) and their presentation and progress maybe devastating and fulminant. Dramatic onset and involvement of multiple vascular beds should alert the clinician to look for these disorders. Outcomes may be improved with rapid diagnosis and prompt institution of specific therapies and interdisciplinary liaison holds the key to success.
Blood transfusions are one of the most commonly prescribed interventions in the critically ill patients. Apart from being a life saving intervention, they can also be associated with life threatening complications. Despite multiple trials and guidelines, there is a wide variability and lack of adherence to the guideline\'s. Auditing transfusion practices help us in introspecting and modifying our prescriptions as per the recommended standards.
There has seen an increase in anticoagulant consumption worldwide over the past few decades. With this widespread utilization of anticoagulants, clinicians are increasingly likely to encounter situations where anticoagulants would need to be withheld. This includes emergency and elective procedures or surgeries as well as major or minor bleeding as a direct result of over anticoagulation or consequent to other intercurrent illnesses such as sepsis or trauma with multiorgan failure, where the anticoagulant may contribute to coagulation abnormalities. Clinicians are required to have a thorough understanding of the indications for anticoagulant prescription, drug interactions and monitoring, indications and options of reversal of anticoagulation and management of bleeding in the situations described above. Once the acute process is managed, the ongoing need and timing of reinitiation of anticoagulation is also crucial. This article provides an overview on the indications for reversal of anticoagulation, the agents used for reversal and the timing of reinitiation of anticoagulants.