Perioperative care for cardiac surgery is undergoing rapid evolution. Many of the changes involve the application of novel technologies to tackle common challenges in optimizing perioperative management. Herein, we illustrate recent advances in perioperative management by focusing on a number of novel components that we judge to be particularly important. These include: the introduction of brain and somatic oximetry; transesophageal echocardiographic hemodynamic monitoring and bedside focused ultrasound; ultrasound-guided vascular access; point-of-care coagulation surveillance; right ventricular pressure monitoring; novel inhaled treatment for right ventricular failure; new approaches for postoperative pain management; novel approaches in specialized care procedures to ensure quality control; and specific approaches to optimize the management for postoperative cardiac arrest. Herein, we discuss the reasons that each of these components are particularly important in improving perioperative care, describe how they can be addressed, and their impact in the care of patients who undergo cardiac surgery.

For over fifty years, heparins, the true standard in antithrombotic prophy - laxis and treatment, have been widely used in clinical practice. However, heparin therapy is associated with 2 types of thrombocytopenia that are des- cribed as: heparin-associated thrombocytopenia types I and II. Heparin-induced thrombocytopenia (HIT) refers to type II. This immune thrombocytopenia, paradoxically, causes thrombosis and constitutes the most severe adverse event associated with heparin treatment. 1 In the absence of any absolute criteria, the diagnosis of HIT is established on the basis of a wide spectrum of clinical and laboratory markers combining a careful analysis of the patient's history and spe - cialized tests. Nevertheless, patient management remains urgent and should not be postponed because of pending test results. This issue of Anesthesiology Rounds reviews the epidemiology, pathology, clinical features, and diagnosis of HIT. The applicable tests that may help in diagnosing HIT are also examined and the treatment modalities outlined. THE DRAMATIC CLINICAL EXPRESSION OF HIT HIT is generally characterized by a precipitous diminution in platelet count with a relative fall of >50% of the initial value . 1 HIT is actually a state of acquired immune mediated hypercoagulability, which is associated with disseminated cell activation involving platelets, monocytes, and the vascular endothelium. As an acronym, from a clinical standpoint, HIT usually indicates H Heparin- IInduced TThrombosis. This state of acquired hypercoagulation persists even if heparin is discontinued. Therefore, the rate of thrombotic events is 5% to 10% per day during the first week, and reaches a cumulative incidence of >50% at 1 month. 2 The clinical setting and patient factors influence the incidence of such throm - botic events. Venous thromboembolic events occur particularly in surgical settings, and arterial events are more often described in patients with atherosclerosis. Intravas - cular devices such as stents, arterial lines, cardiac filters, or prosthetic cardiac valves are prone to thrombus formation and should be explored first. Venous thromboembolic adverse events (AEs) are usually distinct from the thrombotic event that originally required the initiation of heparin treatment. In >60% of patients, these thrombotic events exist at the time thrombocytopenia is dis - covered , 2 and their presence must be sought systematically . 3 Various locations for thromboembolic events have been described: proximal deep veins in the lower limbs (50%), pulmonary embo lism (25% of cases), mesenteric or portal veins, cerebral venous sinuses, and even the upper limbs, especially if a central venous catheter is in place (5%). The presence of thrombotic AEs is a negative outcome factor that quadruples the risk of mortality. Venous gangrene of the limbs with distal necrosis can occur in a limb with venous thrombosis. Most often, it is associated with oral anticoagulant therapy and a supratherapeutic International Normalized Ratio or INR >4, while heparin is discon - tinued and therapy is switched to a vitamin K antagonist (VKA).

1 Cette douleur est complexe car composée de plusieurs types de stimuli: un excès de nociception conduite par des fibres somatiques et viscérales, comme pour toute douleur post chirurgicale, auquel s'ajoute une composante neuropathique importante. De plus, cette douleur concerne plusieurs localisations : la paroi thoracique en regard de l'incision chirurgicale, la plèvre notamment si un drainage thoracique est laissé en place, et l'épaule ipsilatérale. Par ailleurs, les patients opérés en chirurgie thoracique présentent souvent de faibles réserves fonctionnelles cardiorespira- toires, ce qui aggrave les conséquences de la douleur aiguë post-thoracotomie sur la fonc- tion ventilatoire et cardiaque. La prise en charge des patients opérés d'une thoracotomie est un double défi, car le traitement de la douleur aiguë doit être optimal pour une bonne réhabilitation à court terme mais surtout pour prévenir l'apparition de douleur chronique.

L'évaluation préopératoire systématique du risque cardiovasculaire associé à une chirurgie non cardiaque est primordiale. En effet, les patients subissant ce type de chirurgie ne sont pas exempts d'un risque substantiel d'événements cardiaques. Annuellement, 500 000 à 900 000 patients au monde expérimenteront une complication cardiaque majeure en périopératoire : décès, infarctus du myocarde (IM) ou arrêt cardiaque non fatal 1 . Le nombre de patients

3 In such a context, locoregional analgesia (LRA) techniques are often used and are an important element of the recovery process. The anesthesiologist in charge of patients undergoing TKA must be familiar with these techniques. Successful postoperative analgesia requires early patient management that should begin at the time of preoperative consultation. This issue of Anesthesiology Rounds illustrates our view of the analgesic management of patients undergoing TKA. The topic is discussed chronologically, indicating the sequence of clinical decisions as they should be made. Innervation of the lower limb, together with the description of the techniques and their safety rules, are essential prerequisites found in numerous reference works and articles and, if necessary, should be con- sulted by the reader, since the details will not be discussed. 4

Preoxygenation has been a recognized technique since 1955. Its purpose is to increase the oxygen reserves in the body and thus prolong the safe period of apnea between induction of anesthesia and the moment the airway is secured. This extra time can be life-saving when ventilation and intubation are impossible - "cannot ventilate, cannot intubate" - or difficult. The first part of this update reviews the physiopathological mechanisms responsible for tissue oxygenation and the importance of preoxygenation. The second part reviews the effectiveness of preoxygenation in different settings, as well as the various techniques that allow optimal effectiveness. WHY PREOXYGENATE? Oxygen reserves in the body2 During the apneic period following induction of anesthesia, tissue oxygenation proceeds at the expense of the body's oxygen reserves. These reserves are quantitatively small and are located in 3 compartments: the lungs, the plasma, and the red cells (Table 1). Added to these three main reserve compartments is the oxygen, non-mobilizable during apnea, which is present in the interstitial space and that stored in myoglobin. Practically speaking, preoxy- genation increases the reserves of the body, mainly through the increase in oxygen concen- tration in the functional residual capacity (FRC). Replacement of nitrogen by oxygen during preoxygenation takes place rapidly at first, but slows down as the process continues. 3

1In onethird of these cases, aspiration occurred at induction of anesthesia and, in 64% of these cases, there was inadequate paralysis at the time of intubation. If a full stomach is suspected, pre-oxygenation is performed to avoid hypoxemia, should ventilation be impossible for several minutes. Then, one proceeds with rapid intravenous induction that includes a neuromuscular blocking agent to limit the interval between anesthesia induction and tracheal intubation to approximately 1 minute (Table 1). The goal is to reduce the time period during which aspiration of gastric contents is possible. However, this sequence of events is associated with 2 major disadvantages: first, the need to inject rapidly does not allow titration of anesthetic agents and, second, the technique carries the risk of failure of both intubation and ventilation (a “can’t intubate, can’t ventilate” scenario). To minimize the risk of aspiration, intubating conditions must be optimal. To achieve this, it is not realistic to depend on large doses of opioid and hypnotic drugs because of the risk of hypotension. In patients presenting for emergency surgery, optimal intubating conditions cannot be obtained unless adequate doses of neuromuscular blocking agents are given. In this issue of Anesthesiology Rounds, discussion is restricted to a case concerning an adult patient with a pre-operative airway exam that suggests no anticipated problems with tracheal intubation. The indications for rapid sequence induction are not discussed, but it is assumed that the anesthesiologist has determined that a rapid sequence induction with tracheal intubation is indicated. Specific cases, such as emergency surgery in children, in pregnant women, and in individuals with elevated intracranial pressure, open eye injuries, or cervical spine trauma, are not covered. HISTORY The relationship between anesthesia and aspiration pneumonia became clear in 1946, when Mendelson, an obstetrician, published a case series of pregnant patients, most of whom had been administered an anesthetic via face mask. This led to the widespread acceptance of pre-operative fasting rules, but this solution did not solve the problem of the patient with slow gastric emptying or when the surgical procedure cannot be delayed. The introduction of succinylcholine in 1951 was a major advance. However, in a British survey on perioperative mortality in the early 1950s, vomiting and regurgitation accounted for as much as 19% of the deaths attributable to anesthesia. 2

1 Since then, multiple randomized clinical trials have proven the efficacy and superiority of ICD therapy for both the secondary and primary preven- tion of sudden cardiac death. 2-6 Because the clinical indications for these devices are expanding, more patients with an ICD are likely to undergo surgical or obstetrical pro- cedures. This issue of Anesthesiology Rounds reviews the history, structure, function, and clinical indications for ICD technology, including a discussion of anesthetic man- agement strategies. HISTORY

patients. 1 While estimates of the incidence of postanesthesia shivering vary greatly, it is reported that from 5% to 65% of patients experience shivering following surgery and anesthesia. Although the precise origin of postoperative shiver- ing remains uncertain, a number of hypotheses have been advanced. In addi- tion to being a significant source of discomfort for patients coming out of surgery, it can cause other adverse effects. This issue of Anesthesiology Rounds endeavours to explain postoperative shivering and discuss preventive strate- gies and treatments.

The anesthesiologist assumes an important role when administering a blood transfusion. The indication for transfusing packed red blood cells in the perioper- ative phase has been the subject of many published articles. However, it may be time to re-examine this topic. In light of the literature published over a number of years, a threshold for starting a transfusion based on a double "trigger" (a dou- ble indication) is the most reasonable approach. The "therapeutic" threshold (anemia + an anemia-related physiopathological condition) is not directly linked to a minimum hemoglobin (Hb) level, but rather is a dynamic balance between the physiological state of a patient and his/her tolerance. The "preventive" trans- fusion threshold (anemia + estimated risk) is aimed at preventing an increase in morbidity and mortality that may result from perioperative anemia. This transfu- sion trigger calls for an Hb concentration of < 70 g/L according to prospective and randomized clinical trials. Based on retrospective studies, the appropriate "trig- ger" level is somewhere between 50 g/L and 70 g/L. We do not have sufficient information to establish guidelines for patient subgroups or even to identify patients at higher risk of perioperative complications. Giving a transfusion only on the basis of a low hemoglobin level is no longer justified if one evaluates the risk/benefit and availability/benefit ratios of allo- geneic blood products and such a practice is probably detrimental for many patient subgroups. Allogeneic blood products (ABP) are a natural therapeutic resource that must be constantly renewed. Some 60% to 70% of packed red blood cells are administered dur- ing hospitalization for surgery. The anesthesiologist plays a leading role in the area of perioperative transfusional medicine because his expertise enables him to evaluate the risks of, and tolerance to, anemia and the alternatives to giving a transfusion. He often takes on the role of transfusing physician. Different considerations will influence trans- fusion practice. First, there is always the fear that a shortage of ABPs will limit access to surgery. In addition, with the advent of many transfusion alternatives in the clinical setting, we must redefine our transfusion practice. Finally, despite all preventive measures, ABPs are always a source for potentially pathogenic agents.