Thomas G. Rainey

Hypocalcemia in critically ill patients

PurposeTo review calcium regulation, causes of hypocalcemia during critical illness, clinical features and treatment of hypocalcemia, hemodynamic effects of calcium administration, calcium-catecholamine interactions, and the role of calcium in ischemic injury. DesignRepresentative articles from the medical literature are used to support the discussion of selected aspects of calcium metabolism which are important to the practice of critical care medicine. SubjectsResults from both animal and human investigations and both in vitro and in vivo studies are discussed. ResultsCirculating calcium levels are best measured using ionized calcium electrodes. Ionized hypocalcemia is common in critically ill patients and usually results from impaired parathyroid hormone secretion or action, impaired vitamin D synthesis or action, or calcium chelation/precipitation. Ionized hypocalcemia most commonly presents as cardiovascular or neuromuscular insufficiency. Mild ionized hypocalcemia (>0.8 mmol/L) is usually asymptomatic and frequently does not require treatment. Moderate-to-severe ionized hypocalcemia is best treated with iv calcium in the critically ill patient. The majority of studies report no increase in cardiac output but a significant increase in BP after iv calcium administration. When administered with β-adrenergic agonists, calcium frequently impairs their cardiovascular actions. Intracellular calcium dysregulation is common during ischemic and shock states. Agents which increase intracellular calcium may be harmful during cellular ischemia. ConclusionsAlterations in calcium regulation and calcium concentrations are common during critical illness. Optimal management of altered calcium concentrations requires an understanding of the pathophysiology behind these alterations.

Sympathetic nervous system "switch off" with severe hypothermia.

Hypothermia occurs frequently in the critically ill patient, yet little is known about the endogenous cate-cholamine response to this stress. To study this problem, we measured heart rate (HR), mean arterial blood pressure (MAP), and plasma levels of norepinephrine (NE) and epinephrine (Epi) in subhuman primates (baboons) during progressive hypothermia from 37° to 29°C and then during rewarming to 37°C. As the core temperature decreased from 37° to 33°C, HR and MAP increased significantly (p < 0.05), but as core temperature further decreased from 33° to 29°C, the HR and MAP fell to prehypothermic levels. Plasma concentrations of NE and Epi increased significantly (p < 0.01) as core temperature fell from 37° to 31°C, but as core temperature dropped from 31° to 29°C, plasma NE and Epi levels decreased towards prehypothermic concentrations. These findings indicate that the sympathetic nervous system (SNS) responds quickly to hypothermia but may be “switched off” at a threshold temperature of about 29°C. We speculate that hypotensive patients with temperatures ° 29°C may benefit from infusions of exogenous catecholamines, especially if there have been only minimal benefits achieved with conventional therapy such as fluids, and an increase in ambient temperature.

Critical care delivery: The importance of process of care and ICU structure to improved outcomes: An update from the American college of critical care medicine task force on models of critical care

In 2001, the Society of Critical Care Medicine published practice model guidelines that focused on the delivery of critical care and the roles of different ICU team members. An exhaustive review of the additional literature published since the last guideline has demonstrated that both the structure and process of care in the ICU are important for achieving optimal patient outcomes. Since the publication of the original guideline, several authorities have recognized that improvements in the processes of care, ICU structure, and the use of quality improvement science methodologies can beneficially impact patient outcomes and reduce costs. Herein, we summarize findings of the American College of Critical Care Medicine Task Force on Models of Critical Care: 1) An intensivist-led, high-performing, multidisciplinary team dedicated to the ICU is an integral part of effective care delivery; 2) Process improvement is the backbone of achieving high-quality ICU outcomes; 3) Standardized protocols including care bundles and order sets to facilitate measurable processes and outcomes should be used and further developed in the ICU setting; and 4) Institutional support for comprehensive quality improvement programs as well as tele-ICU programs should be provided.

Plasma, urine, and CSF catecholamine concentrations during and after ketamine anesthesia

Ketamine has been reported to increase plasma catecholamine concentrations. Prior investigations have only studied plasma catecholamine levels for short periods after iv ketamine. Because ketamine is one of the most frequently used anesthetic agents in critical care research, we evaluated ketamines effect on catecholamines over a longer period of time. Plasma, urine, and CSF epinephrine (E) and norepinephrine (NE) concentrations were serially measured during a 2-h ketamine infusion and a subsequent 2-h “wake-up” period. No changes in heart rate, mean arterial blood pressure or urine, plasma, and CSF NE concentrations were noted during the 4-h study period, whereas there were significant (p < 0.005) increases in urine, plasma, and CSF E levels during ketamine infusion but not during the wake-up period. An unexpected finding was that the baboons had very high basal plasma E levels versus those in humans.It is concluded that ketamine is a useful anesthetic agent for critical care research involving measurements of sympathetic nervous system activity. The interesting observation of high plasma E levels in the baboon warrants further investigation.

Iatrogenic hyperphosphatemia: a metabolic consideration in critical care medicine.

Hypophosphatemia and its consequences have received considerable attention due to their frequency and occurrence in a wide spectrum of clinical disorders.1–7 The cardiac, pulmonary, neurological, and hematological complications of hypophosphatemia offer ample justification for implementing therapy in the setting of phosphorus depletion. However, the goals of such therapy are poorly defined because serum phosphate levels may not reflect total body stores of phosphorus.8 Despite its popularity, little comment has been made in the medical literature concerning adverse reactions of phosphate therapy. In this regard, two case histories are presented to illustrate the potential complications of overgenerous phosphate therapy.

“Bovine ketosis” in a nondiabetic postpartum woman

A 19-yr-old woman developed ketoacidosis 7 wk after the delivery of her first child. Despite breast feeding, she had been on a weight reduction diet resulting in a loss of 12 kg/body wt. With the development of a urinary tract infection, the patient became dehydrated and was found to be in ketoacidosis (arterial pH was 7.25 and PaCO2 was 17 mm Hg). The patient did not use alcohol and was nondiabetic. Therapy with adequate calories, intravenous fluids, and an appropriate antimicrobial agent resulted in prompt normalization of the laboratory abnormalities and resolution of the patients symptoms. The hypothesis is advanced that the postpartum status of the patient put her at particular risk for development of ketoacidosis and that this may represent the first reported episode of “bovine ketosis” in a human.

Bedside blood glucose determinations in critical care medicine: A comparative analysis of two techniques

The accuracy of a new reagent test strip (Chemstrip BG) for the quantitative estimation of whole blood glucose concentration was compared to that of a widely used test strip (Dextrostix). To perform the comparative study, venous blood specimens were obtained from 133 patients. Interpretations of reagent strip glucose readings were made by three observers who separately recorded their impressions from the two strips on each patient. These estimated levels were compared to quantitative (glucose oxidase) concentrations measured from the same specimen. Although there were significant correlations (p less than 0.001) between both reagent strips and the measured values, the Chemstrip BG results more closely approximately measured values for the range of glucose concentrations encountered (10-600 mg/dl). In addition, Chemstrip BG was easier to read and measured a wider range of values than Dextrostix and, unlike Dextrostix, Chemstrip BG strips could be stored for review at a later time. This new glucose test strip accurately and rapidly determines whole blood glucose concentration at the bedside.

Postcraniotomy diabetes insipidus. Who's at risk?

Diabetes insipidus (DI) is thought to be a relatively common complication after craniotomy procedures. To identify subsets of patients at risk for this problem, the postoperative courses of 135 consecutive patients undergoing craniotomy were scrutinized retrospectively. All patients received similar anesthetic management and all were hospitalized in the ICU postoperatively. DI developed in 9 (5 transient, 4 permanent) of 135 patients (6.7%). All 9 patients developing DI had undergone craniotomy for treatment of a pituitary disorder. It is concluded that postcraniotomy DI is a problem almost exclusively observed in patients with pituitary/hypothalamic disease and that DI rarely occurs in patients with other types of intracranial pathology.

Increased circulating plasma norepinephrine concentrations in noncardiac causes of pulmonary hypertension.

Sympathetic nervous system (SNS) activity and circulating norepinephrine (NE) levels may play roles in the elevated pulmonary vascular resistance (PVR) found in patients with pulmonary hypertension. To study the relationship between plasma NE levels, pulmonary NE metabolism, and pulmonary hypertension, we studied 9 patients, suspected of having noncardiac causes of pulmonary hypertension, before and after vasodilator therapy with phentolamine, nitroglycerin, oproterenol, or hydralazine. Patients were admitted to the ICU and studied using pulmonary artery thermodition catheters. Seven of 9 patients had noncardiogenic pulmonary hypertension whereas 2 patients did not have hemodynamic evidence of pulmonary hypertension. Simultaneous pulmonary and radial artery samples were analyzed for plasma NE and epinephrine (EPI) content before and after various vasodilator agents. Baseline pulmonary artery (PA) and radial artery NE concentrations correlated (r = .72) with PVR, PA pressures, and PA minus pulmonary capillary wedge (WP) pressures and were increased compared to the 2 patients with normal pulmonary pressures (p < .01). The normal pulmonary extraction of circulating NE was absent in the 7 patients with pulmonary hypertension. PVR decreased significantly in all 7 patients with each vasodilator (p < .05); however, the decrease was independent of any change in plasma NE concentration and therapy had no effect on the pulmonary extraction of circulating NE. These data indicate that elevations in plasma NE are coincident with the presence of noncardiogenic pulmonary hypertension and that acute pharmacologic reduction of PVR does not normalize the loss of pulmonary NE metabolism.

Critical care medicine for the 21st century.

T he long awaited report on the “Current and projected workforce requirements for care of the critically ill: Can we meet the requirements of an aging population?” has been published (1). COMPACCS (Committee on Manpower for Pulmonary and Critical Care Societies was initiated in 1995 to address the physician workforce requirements for the care of the critically ill. The group recognized from the beginning that critical care is a unique discipline. It is practiced by physicians from a range of primary specialties (internal medicine, surgery, anesthesiology, and pediatrics) and includes internists with training in pulmonary or other subspecialties, as well as general internal medicine. In addition, the practice of critical care crosses traditional boundaries (e.g., internal medicineor anesthesiatrained critical care physicians often work in mixed medical-surgical or surgical intensive care units [ICUs]). Reflective of the membership composition of the three societies, the study addressed the workforce requirements of both pulmonary practice and critical care practice. Our comments will focus on critical care. The results of this landmark work are remarkable on a number of fronts. a) Methodology: although other specialty workforce studies have been performed, this is the only one to extend the horizon beyond the year 2010 and, therefore, register the impact of aging of the population. Of note, the study confirmed the increased utilization of ICU resources by the elderly. Although adults younger than 65 yrs incurred 37 ICU days per year per 1000 population, those aged 65–85 yrs incurred five to six times that rate. It is the projected care demand created by the aging of the “boomers” that drives the demand to supply imbalance revealed by this work. This imbalance only begins to become apparent after the year 2010. By extending the timeline beyond 2010, the authors identified a major shortfall in the supply of critical care physicians (intensivists) and rung the alarm about similar implications for other specialties/subspecialties in medicine. b) Cooperation: this joint project marks the first significant collaborative venture among the three sponsoring societies. In this venture, they have proven to themselves that they are able to put aside long-held differences to work together to serve the best interests of medicine and, ultimately, the care of the patient. In fact, the collaboration has worked so well that subsequent joint efforts such as the Pulmonary Artery Catheter consensus conference, the joint Board Review courses, and the regular meetings between executive committees have evolved. In our view, that type of partnering makes much more sense than does escalation of intermedicine squabbling and intersociety competition for members’ loyalty, grant money, and positioning. Congratulations. c) Results and implications for patient care: The data provide a wake-up call to all of us. Fully 63% of patients are managed with no designated consulting intensivist, whereas only 37% of the time is there a full-time or consultant intensivist involved. Given current trends, intensivist management will further erode, such that only 30% of critically ill patients in 2020 are treated by intensivists. By 2030, the situation will have further eroded, such that only 24% of critically ill patients are cared for by an intensivist. Since the initiation of this study in 1995, the landscape has changed considerably. The assumption that there would be a declining requirement for physician specialists has been proven faulty. The related assumption that managed care would decrease patient demand has also not materialized as consumer dissatisfaction has driven managed care to liberalize specialist consultation. In fact, data in the current workforce reports indicate an increase in demand for intensivist services under managed care. Most significantly, there is now a compelling body of information that describes intensivists’ central role in achieving medicine’s Holy Grail: increasing the quality of care while simultaneously reducing cost. Available data indicate that the presence of intensivists dramatically reduces ICU mortality, length of stay, and resource utilization (2-4) and is the single strongest predictor of ICU performance (5). Practical experience as demonstrated by the Institute for Healthcare Improvement’s Breakthrough Series on Outcomes Improvement and Cost Reduction in Intensive Care reveals remarkable successes (reduction in length of stay on mechanical ventilation and ICU length of stay by 30%; reduction in cost of sedative medication by 50%) in which intensivist-led teams organize to improve ICU performance (personal communication). Those of us who practice critical care medicine understand that the ICU is an inherently unsafe place for patients— often a necessary place, but a risky one, nonetheless. The patient safety issues that recently received national attention from the Institute of Medicine’s report are unfortunately rampant in our ICUs, and intensivist-led teams are in the best position to effectively address the problems. Under the spotlight placed on safety and cost issues in medicine, patients and payors have recognized the important role of the intensivist. Recently, the Leapfrog Group, a consortium of large companies (including GM and GE among others) announced medical reforms they require for hospitals that treat their beneficiaries. One of the three requirements is that a hospital must staff its ICUs with intensivists if they want to care for employees of companies of the Leapfrog Group. This is a clear wake-up call. Deaths are prevented when intensivists care for critically ill patients; yet currently, only 37% From Critical Care, Suburban Hospital, Bethesda, MD (Dr. Rainey); and Surgery and Anesthesia, St. Louis University, St. Louis, MO (Dr. Shapiro).