J. Ross Renew

Frequency and outcomes of severe hyperlactatemia after elective cardiac surgery

BACKGROUNDnHyperlactatemia is relatively common in the cardiac surgical patient and is usually considered a marker of illness severity. The frequency and impact of severe hyperlactatemia after elective cardiac surgery has not been described, and prognosis may be different compared with that for other surgical or medical critically ill patient populations.nnnMETHODSnWe conducted a retrospective study to evaluate the hospital course and outcomes of patients who developed severe postoperative hyperlactatemia (SPHL; lactate >10 mmol/L) after elective cardiac surgery, from January 1, 2008 to December 31, 2012, at a large, academic, tertiary referral center.nnnRESULTSnOf 9580 cardiac surgical patients who met inclusion criteria, 121 (1.26%) developed SPHL. The most common cause was cardiogenic shock (53.8%). In-hospital mortality was 40.5% but varied widely based on the cause of the SPHL. All patients with definite mesenteric ischemia (n = 5) or extremity compartment syndrome (n = 6) at the time of SPHL died in the hospital. Forty patients (33.1%) were discharged to home, whereas 32 (26.4%) were discharge to a skilled-care facility.nnnCONCLUSIONSnSevere postoperative hyperlactatemia is rare after elective cardiac surgery. Although this phenomenon continues to be associated with mortality, >50% of patients survived to hospital discharge, a more favorable prognosis, compared with other patient populations based on lactate levels alone. Important exceptions were patients who had extremity compartment syndrome or mesenteric ischemia, which were associated with in-hospital death in all cases. In all other etiologic groups, a substantial proportion of patients were discharged to home.

Clinical Pharmacology of Drugs Acting at the Neuromuscular Junction

Since the first administration of d-tubocurarine in 1942 by Harold Griffith to facilitate muscle relaxation during an appendectomy, neuromuscular blocking drugs (NMBDs) have been a class of medications utilized by anesthesiologists and intensivists to facilitate the performance of invasive and painful procedures. NMBDs are administered to improve the quality of intubating conditions and decrease the incidence of vocal cord injury during airway instrumentation. Furthermore, the use of NMBDs to relax major skeletal muscle groups during intra-cavitary operations significantly improves surgical conditions. The utility of NMBDs is not limited to the perioperative arena; they can be used to facilitate mechanical ventilation in patients with poor pulmonary compliance in the intensive care unit.

Preparing for the unexpected: special considerations and complications after sugammadex administration

Sugammadex, a modified gamma-cyclodextrin, has changed clinical practice of neuromuscular reversal dramatically. With the introduction of this selective relaxant binding agent, rapid and reliable neuromuscular reversal from any depth of block became possible. Sugammadex can reverse neuromuscular blockade without the muscarinic side effects typically associated with the administration of acetylcholinesterase inhibitors. However, what remained unchanged is the incidence of residual neuromuscular blockade. It is known that sugammadex cannot always prevent its occurrence, if appropriate dosing is not chosen based on the level of neuromuscular paralysis prior to administration determined by objective neuromuscular monitoring. Alternatively, excessive doses of sugammadex administered in an attempt to ensure full and sustained reversal may affect the effectiveness of rocuronium in case of immediate reoperation or reintubation. In such emergent scenarios that require onset of rapid and reliable neuromuscular blockade, the summary of product characteristics (package insert) recommends using benzylisoquinolinium neuromuscular blocking agents or a depolarizing agent. However, if rapid intubation is required, succinylcholine has a significant number of side effects, and benzylisoquinolinium agents may not have the rapid onset required. Therefore, prior administration of sugammadex introduces a new set of potential problems that require new solutions. This novel reversal agent thus presents new challenges and anesthesiologists must familiarize themselves with specific issues with its use (e.g., bleeding risk, hypermagnesemia, hypothermia). This review will address sugammadex administration in such special clinical situations.

Red Blood Cell Disorders: Perioperative Considerations for Patients Undergoing Cardiac Surgery

Disorders affecting red blood cells (RBCs) are uncommon yet have many important physiologic considerations for patients undergoing cardiac surgery. RBC disorders can be categorized by those that are congenital or acquired, and further by disorders affecting the RBC membrane, hemoglobin, intracellular enzymes, or excessive RBC production. A foundational understanding of the physiologic derangement for these disorders is critical when considering perioperative implications and optimization, strategies for cardiopulmonary bypass, and the rapid recognition and treatment if complications occur. This review systematically outlines the RBC disorders of frequency and relevance with an emphasis on how the disorder affects normal physiologic processes, a review of the literature related to the disorder, and the implications and recommendations for patients undergoing cardiac surgery.

Quantitative Neuromuscular Monitoring: Current Devices, New Technological Advances, and Use in Clinical Practice

Purpose of ReviewThe purpose of this review is to summarize various quantitative neuromuscular monitoring modalities and describe strategies to implement them into routine practice. We will contrast these objective modalities with unreliable clinical tests and subjective techniques that expose patients to unnecessary risk associated with postoperative residual weakness.Recent FindingsAs major specialty societies publish guidelines and consensus statements urging anesthesiologists to utilize quantitative monitors, clinicians must familiarize themselves with this equipment. Furthermore, new monitors are emerging as the industry tries to address the need for user-friendly, reliable monitors.SummaryClinical assessment is an unacceptable technique to guide neuromuscular blockade management in patients receiving neuromuscular blocking agents. The use of a peripheral nerve stimulator can provide some information regarding the level of neuromuscular blockade in patients; however, it cannot reliably confirm adequate recovery. The use of objective, quantitative monitoring is an essential practice that helps guide the administration of neuromuscular blocking agents and excludes deleterious postoperative residual weakness.

The Effect of Quantitative Neuromuscular Monitoring on the Incidence of Residual Neuromuscular Blockade and Clinical Outcomes

Neuromuscular blocking agents (NMBAs) are useful perioperative medications. Despite this utility, their administration is associated with increased morbidity due to residual neuromuscular blockade. Clinical testing prior to tracheal extubation is subjective, dependent on the patient’s cooperation, and not predictive of adequate respiratory function to prevent the occurrence of postoperative critical respiratory events. The use of peripheral nerve stimulators may improve detection of residual weakness; however, this technique does not reliably detect residual paralysis, as it requires the subjective (and imperfect) assessment of fade in response to train-of-four (TOF) stimulation. Quantitative neuromuscular monitoring can be accomplished through a variety of modalities and remains as the most effective and reproducible method of detecting residual paralysis after NMBA administration. In this review, we will discuss the various techniques that are used clinically to assess depth of block and adequacy of reversal, with a focus on quantitative (objective) neuromuscular monitoring.