Acid-Base Disorders in the Critically Ill Patient

Acid-base disorders are common in the intensive care unit. By utilizing a systematic approach to their diagnosis, it is easy to identify both simple and mixed disturbances. These disorders are divided into four major categories: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. Metabolic acidosis is subdivided into anion gap and non-gap acidosis. Distinguishing between these is helpful in establishing the cause of the acidosis. Anion gap acidosis, caused by the accumulation of organic anions from sepsis, diabetes, alcohol use, and numerous drugs and toxins, is usually present on admission to the intensive care unit. Lactic acidosis from decreased delivery or utilization of oxygen is associated with increased mortality. This is likely secondary to the disease process, as opposed to the degree of acidemia. Treatment of an anion gap acidosis is aimed at the underlying disease or removal of the toxin. The use of therapy to normalize the pH is controversial. Non-gap acidoses result from disorders of renal tubular H + transport, decreased renal ammonia secretion, gastrointestinal and kidney losses of bicarbonate, dilution of serum bicarbonate from excessive intravenous fluid administration, or addition of hydrochloric acid. Metabolic alkalosis is the most common acid-base disorder found in patients who are critically ill, and most often occurs after admission to the intensive care unit. Its etiology is most often secondary to the aggressive therapeutic interventions used to treat shock, acidemia, volume overload, severe coagulopathy, respiratory failure, and AKI. Treatment consists of volume resuscitation and repletion of potassium deficits. Aggressive lowering of the pH is usually not necessary. Respiratory disorders are caused by either decreased or increased minute ventilation. The use of permissive hypercapnia to prevent barotrauma has become the standard of care. The use of bicarbonate to correct the acidemia is not recommended. In patients at the extreme, the use of extracorporeal therapies to remove CO 2 can be considered.

Half the V by 120: A practical approach to the prevention of the dialysis disequilibrium syndrome

The dialysis disequilibrium syndrome (DDS) results from osmotic shifts between the blood and the brain compartments. Patients at risk for DDS include those with very elevated blood urea nitrogen, concomitant hypernatremia, metabolic acidosis, and low total body water volumes. By understanding the underlying pathophysiology and applying urea kinetic modeling, it is possible to avoid the occurrence of this disorder. A urea reduction ratio (URR) of no more than 40%-45% over 2 h is recommended for the initial hemodialysis treatment. The relationship between the URR and Kt/V is useful when trying to model the dialysis treatment to a specific URR target. A simplified relationship between Kt/V and URR is provided by the equation: Kt/V = -ln (1 - URR). A URR of 40% is roughly equivalent to a Kt/V of 0.5. The required dialyzer urea clearance to achieve this goal URR in a 120-min treatment can simply be calculated by dividing half the patient's volume of distribution of urea by 120. The blood flow rate and dialyzer mass transfer coefficient (K₀ A) required to achieve this clearance can then be plotted on a nomogram. Other methods to reduce the risk of DDS are reviewed, including the use of continuous renal replacement therapy.

Icosapent ethyl reduces atherogenic markers in high-risk statin-treated patients with stage 3 chronic kidney disease and high triglycerides

Objective: Patients with chronic kidney disease (CKD) have increased cardiovascular disease (CVD) risk, likely driven by atherogenic and inflammatory markers beyond low-density lipoprotein cholesterol (LDL-C). The objective of this hypothesis-generating post hoc subgroup analysis was to explore the effects of icosapent ethyl at 2 or 4 g/day (prescription pure ethyl ester of the omega-3 fatty acid eicosapentaenoic acid [EPA]) on atherogenic lipid, apolipoprotein, inflammatory parameters (high-sensitivity C-reactive protein [hsCRP], lipoprotein-associated phospholipase A₂ [Lp-PLA₂]), and oxidative parameters (oxidized-LDL [ox-LDL]) in statin-treated patients from ANCHOR with stage 3 CKD.Methods: The 12-week ANCHOR study evaluated icosapent ethyl in 702 statin-treated patients at increased CVD risk with triglycerides (TG) 200-499 mg/dL despite controlled LDL-C (40-99 mg/dL). This post-hoc analysis included patients from ANCHOR with stage 3 CKD (estimated glomerular filtration rate [eGFR] ≤60 mL/min/1.73 m² for ≥3 months) randomized to icosapent ethyl 4 g/day (n = 19), 2 g/day (n = 30), or placebo (n = 36).Results: At the prescription dose of 4 g/day, icosapent ethyl significantly reduced TG (-16.9%; P = 0.0074) and other potentially atherogenic lipids/lipoproteins, ox-LDL, hsCRP, and Lp-PLA₂, and increased plasma and red blood cell EPA levels (+879% and +579%, respectively; both P < 0.0001) versus placebo. Icosapent ethyl did not significantly alter eGFR or serum creatinine. Safety and tolerability were similar to placebo.Conclusions: In patients with stage 3 CKD at high CVD risk with persistent high TG despite statins, icosapent ethyl 4 g/day reduced potentially atherogenic and other cardiovascular risk factors without raising LDL-C, with safety similar to placebo. These findings suggest prospective investigation may be warranted.

Partial Fanconi syndrome induced by ifosfamide

Ifosfamide-induced proximal tubular nephropathy can present as a spectrum of disease, from isolated hyperaminoaciduria to a partial or complete Fanconi syndrome. We report a case of ifosfamide-induced partial Fanconi syndrome in a man with metastatic progressive Ewing sarcoma and put forth a hypothesis on the mechanism.

Euvolemia-A critical target in the management of acute kidney injury

It has been clearly established that critically ill patients with sepsis require prompt fluid resuscitation. The optimal amount of fluid and when to taper this resuscitation is less clear. There is a growing evidence that fluid overload leads to acute kidney injury, and increased morbidity and mortality. A clinician's best intentions in resuscitating a patient can lead to too much of a good thing. Currently, there are several bedside tools to aid in determining a patient's response to a fluid challenge as well as in the assessment of the current volume status. Guidelines are not available on the exact rate of fluid overload removal and what medicinal or mechanical modality is most favorable. We discuss our experience and an examination of the literature on the problems with fluid overload, and how a patient may benefit from forced fluid removal.

Predictors of HIV-Infection in Older Adults

This article is a retrospective case-control study of patients from a Veteran’s Affairs Medical Center and an urban public hospital. Patients (53) older than 55 at the time of their HIV diagnosis were age- and gender-matched to 106 HIV-negative controls. Potential predictors of HIV-infection were abstracted from the medical records. HIV-positive patients were more likely to have a history of sexually transmitted diseases, have Hepatitis B+, and have significant differences in their mean globulin, serum sodium, albumin, and hemoglobin levels. The mean albumin to globulin ratio was also statistically, significantly different between the HIV-positive patients and the controls. These data suggest that for patients older than 55, certain medical history parameters may be useful in predicting risk of being HIV-positive. An albumin to globulin ratio < 1.0, especially when combined with a history of alcohol abuse or prior sexually transmitted disease, should prompt all physicians to screen their older patients for HIV.

Association Between Cognitive Impairment and Chronic Kidney Disease in Mexican Americans

Objectives

To analyze the association between chronic kidney disease (CKD) and mild cognitive impairment (MCI) in Mexican Americans and to determine whether there is a blood‐based proteomic profile linking CKD to MCI.

Design

Retrospective analysis of cohort study.

Setting

Health and Aging Brain among Latino Elders study.

Participants

Mexican Americans (N = 437, 105 men, 332 women).

Measurements

Data were analyzed to examine the link between estimated glomerular filtration rate (eGFR) and detailed neuropsychological functioning. Serum proteomic markers were also examined.

Results

Lower eGFR levels were associated with significantly poorer neuropsychological functioning across multiple domains. After adjusting for age, sex, education, and diabetes mellitus, participants with an eGFR less than 45 mL/min per 1.73 m² performed significantly worse than those with an eGFR from 45 to 59 mL/min per 1.73 m² or 60 mL/min per 1.73 m² and higher in processing speed (F = 14.1, P < .001), executive functioning (F = 4.5, P = .01), visuospatial skills (F = 4.8, P = .009), and global cognitive functioning (F = 6.2, P = .002). Participants with an eGFR less than 45 mL/min per 1.73 m² also performed significantly worse than those with an eGFR of 60 mL/min per 1.73 m² or greater on delayed memory (F = 3.8, P = .02). There was a trend toward lower eGFR levels being associated with greater risk of MCI (odds ratio (OR) = 2.4, 95% confidence interval (CI) = 0.91–6.1, P = .07), which was stronger for men (OR = 9.6, 95% CI = 1.3–74.3, P = .03). A serum proteomic profile consisting of Factor VII, interleukin‐10, C‐reactive protein, and fatty acid binding protein was 93% accurate in detecting CKD‐related MCI.

Conclusion

Lower eGFR was associated with significantly poorer neuropsychological functioning in Mexican Americans. A blood‐based profile was generated that was highly accurate in detecting CKD‐related MCI. A blood profile capable of predicting CKD‐related cognitive impairment would be of benefit for the design of clinical interventions.

A case report of defective endogenous vitamin D: a new clinical entity

OBJECTIVE

To report a case of defective endogenous vitamin D with excellent response to low dose calcitriol replacement therapy.

METHODS

We describe the patient's clinical presentation, biochemical workup, and clinical course.

RESULTS

The patient initially presented with severe symptomatic hypocalcemia and was diagnosed with pseudohypoparathyroidism type 1b at an outside hospital and started on calcitriol 2.25 mcg twice daily with good response but calcitriol was stopped later for cost concerns which led to recurrence of symptoms, worsening hypocalcemia and increased parathormone levels. On review of her case it was noted that her 1,25 dihydroxy: vitamin D level was within normal limits even before she started taking calcitriol, which is not consistent with pseudohypoparathyroidism type 1b. Restarting low dose calcitriol (0.25 mcg twice daily) improved the patient's calcium level to 10.1 mg/dl and decreased the parathormone level to 17 pg/ml and symptoms resolved. Conditions associated with low serum calcium and high parathormone include pseudohypoparathyroidism, vitamin D deficiency and vitamin D resistance. This patient does not fit into any of the known entities causing hypocalcemia and elevated parathormone.

CONCLUSIONS

We hypothesize that this patient had an inadequate number of vitamin D receptors that was corrected by exogenous administration of vitamin D.

Border-crossers' nephropathy: the risk of coming to America

Immigrants attempting to cross the border often wander for days without food or water, subsequently developing acute kidney injury (AKI) secondary to rhabdomyolysis. In this article, we describe our experience with myoglobinuric AKI in these border crossers. Records from all patients in the custody of the border patrol from 1 June 2010 to 30 June 2011, who had AKI defined by the Acute Kidney Injury Network (AKIN) criteria and a CK > 1000 IU/L, were reviewed. The age, gender, temperature, days in the desert, initial serum creatinine, CK on presentation, need for dialysis, length of hospital stay, and serum creatinine at discharge were recorded and analyzed. Forty-two patients developed myoglobinuric AKI with a mean age of 32.5 years. Among them, 38 were males and four females. There was a mean of 4.2 days in the desert. Seven had stage 1 AKI, 10 stage 2, and 25 stage 3. 5 patients required hemodialysis. Only one patient had a temperature >100.6ºF on arrival. CKs ranged between 1101 and 447,966 IU/L. Mean length of stay was 4 days. Two patients were discharged on hemodialysis and eight were discharged with serum creatinine levels of  >1.3 mg/dL. This is the largest series of myoglobinuric AKI reported in border crossers. The kidney injury is presumably due to the excessive heat combined with volume depletion. We have coined the term "border crossers' nephropathy" for this disorder. This is a serious problem that has both political and economic consequences on both sides of the border.

Continuous renal replacement therapy: cause and treatment of electrolyte complications

Continuous renal replacement therapy (CRRT) has become the modality of choice for critically ill patients. Although often hemodynamically better tolerated than intermittent dialysis, the continuous nature of this therapy may cause significant electrolyte complications. These complications commonly result from removal of electrolytes from the body without adequate replacement or because of the use of trisodium citrate as the anticoagulant. Both hypophosphatemia and hypokalemia frequently complicate prolonged treatment. These complications can be avoided by adding these electrolytes to the dialysate or replacement fluid. The use of citrate, especially if this anticoagulant is not used routinely following established protocols, can also result in several electrolyte abnormalities. Because citrate works by chelating calcium, hypo- and hypercalcemia occur because of under- or overreplacement of calcium. Because citrate is a base equivalent, if the bicarbonate concentration of the dialysate or replacement fluid is not decreased, a metabolic alkalosis may develop. Less commonly, in patients with severe liver dysfunction who cannot metabolize citrate back to bicarbonate, a metabolic acidosis may develop. Although CRRT may cause electrolyte complication it also can be the treatment of choice for the correction of certain electrolyte complications. In patients with acute or chronic renal failure who present with significant dysnatremias, intermittent hemodialysis may cause overly rapid correction of the serum sodium with serious neurologic sequelae. The ability to manipulate the sodium concentration of the dialysate or replacement fluid and the more sustained nature of the treatment allows for a slower correction thus avoiding complications.

Efficacy and safety of renal tubule cell therapy for acute renal failure

The mortality rate for patients with acute renal failure (ARF) remains unacceptably high. Although dialysis removes waste products and corrects fluid imbalance, it does not perform the absorptive, metabolic, endocrine, and immunologic functions of normal renal tubule cells. The renal tubule assist device (RAD) is composed of a conventional hemofilter lined by monolayers of renal cells. For testing whether short-term (up to 72 h) treatment with the RAD would improve survival in patients with ARF compared with conventional continuous renal replacement therapy (CRRT), a Phase II, multicenter, randomized, controlled, open-label trial involving 58 patients who had ARF and required CRRT was performed. Forty patients received continuous venovenous hemofiltration + RAD, and 18 received CRRT alone. The primary efficacy end point was all-cause mortality at 28 d; additional end points included all-cause mortality at 90 and 180 d, time to recovery of renal function, time to intensive care unit and hospital discharge, and safety. At day 28, the mortality rate was 33% in the RAD group and 61% in the CRRT group. Kaplan-Meier analysis revealed that survival through day 180 was significantly improved in the RAD group, and Cox proportional hazards models suggested that the risk for death was approximately 50% of that observed in the CRRT-alone group. RAD therapy was also associated with more rapid recovery of kidney function, was well tolerated, and had the expected adverse event profile for critically ill patients with ARF.

Fibromuscular Dysplasia: An Uncommon Cause of Secondary Hypertension

Fibromuscular dysplasia is a noninflammatory vascular disease that commonly affects the distal two thirds of the renal artery and branch vessels, but occasionally involves other arteries. Progression of stenosis occurs in 16%-38% of renal arteries. Although the etiology is unknown, genetic studies suggest a relationship to the angiotensin-converting enzyme I allele. Thin, young Caucasian women without a family history of hypertension are most commonly affected. An abdominal or flank systolic-diastolic bruit is an important clue for the diagnosis. Most noninvasive screening tests are not sensitive or reproducible to be used to rule out renal artery stenosis, but digital subtraction renal angiography usually confirms the diagnosis. Percutaneous renal artery angioplasty is the treatment of choice, but may not result in normalization of blood pressure if diagnosis is delayed. Since restenosis occurs, continued follow-up is necessary.

Lactic acidosis: from sour milk to septic shock

Lactic acidosis is frequently encountered in the intensive care unit. It occurs when there is an imbalance between production and clearance of lactate. Although lactic acidosis is often associated with a high anion gap and is generally defined as a lactate level >5 mmol/L and a serum pH <7.35, the presence of hypoalbuminemia may mask the anion gap and concomitant alkalosis may raise the pH. The causes of lactic acidosis are traditionally divided into impaired tissue oxygenation (Type A) and disorders in which tissue oxygenation is maintained (Type B). Lactate level is often used as a prognostic indicator and may be predictive of a favorable outcome if it normalizes within 48 hours. The routine measurement of serum lactate, however, should not determine therapeutic interventions. Unfortunately, treatment options remain limited and should be aimed at discontinuation of any offending drugs, treatment of the underlying pathology, and maintenance of organ perfusion. The mainstay of therapy of lactic acidosis remains prevention.

Using standardized patients to teach disease management skills to preclinical students: a pilot project

BACKGROUND

Physician adherence to practice guidelines has been poor. Exposure to such guidelines is not a routine part of medical school curricula.

PURPOSE

This study was designed to determine whether standardized patients could be used to teach preclinical students the skills to manage a patient with newly diagnosed diabetes mellitus.

METHODS

Students were assigned a standardized patient with hyperglycemia. The students were given guidelines on the management of diabetes and told to manage the patient appropriately. Patients' charts were reviewed to determine if all cardiovascular risks were managed appropriately.

RESULTS

Students successfully managed all cardiovascular risks according to published guidelines. Participants overwhelmingly believed this methodology was a valuable way to teach disease management.

CONCLUSION

Second-year students can use practice guidelines to successfully manage patients with diabetes. The students' performance exceeded the standards of care found in the published literature. This problem-based approach may be an ideal way to teach disease management.

Multiple myeloma associated with lactic acidosis

Type B lactic acidosis is rare among patients with malignant diseases. To date only one case report has documented lactic acidosis occurring in a patient with multiple myeloma (MM). Our patient, a 55-year-old black man, was diagnosed with stage IIIA immunoglobulin G-kappa (IgG-kappa) MM in September 1995. He was found to have severe lactic acidosis at the time of second relapse. During the terminal phase of his disease, he required multiple hospitalizations for management of lactic acidosis and other complications of his MM. No other cause of his elevated lactate levels was identified. Although type B lactic acidosis may more commonly occur in patients with leukemia or lymphoma, it may rarely present in patients with rapidly progressive and refractory MM.

Identification of cardiovascular risk factors in homeless adults

BACKGROUND

Cardiovascular disease is an important health problem among homeless adults; however, the common cardiac risk factors present in this population are unknown. This study was undertaken to identify the reversible cardiovascular risks present in the homeless.

METHODS

A retrospective chart review was performed randomly on 100 patients who were seen at a homeless clinic in New Orleans, Louisiana. These patients were compared with 200 matched nonhomeless patients who attended an inner-city primary care clinic. Each chart from the 2 groups was reviewed for the presence of hypertension, diabetes mellitus type 2, cigarette smoking, and hypercholesterolemia. Statistical comparisons were made between the homeless and the control subjects.

RESULTS

Hypertension was present in 65% of the homeless but only 52% of the nonhomeless [P < 0.05; odds ratio 1.78 (CI, 1.09 to 2.9)]. Smoking was far more common in the homeless than the nonhomeless, 75 versus 57%, respectively [P < 0.005; odds ratio 2.22 (CI, 1.27 to 3.88)]. There was no difference in the prevalence of diabetes or total cholesterol. Compared with national data hypertension, smoking and diabetes seem to be represented excessively in the homeless population.

CONCLUSIONS

Smoking and hypertension are significantly more prevalent in the homeless population than in a matched cohort. Educational and preventive programs are needed to reduce the prevalence of cardiovascular disease and reduce the overutilization of expensive healthcare resources.

Endocarditis and hemorrhagic stroke caused by Cunninghamella bertholletiae infection after kidney transplantation

Cunninghamella bertholletiae is a saprophytic fungus found in soil. Infection with this organism is extremely rare, occurring almost exclusively in immunosuppressed hosts. There have been only three previous cases of infection with this fungus reported in solid-organ recipients. We report an unusual case of disseminated Cunninghamella infection in a woman who had received a renal transplant. A 48-year-old woman received a living-related kidney transplant for focal segmental glomerulonephritis. She was treated with plasmapheresis and muromonab-CD3 (OKT3) for two episodes of rejection. Because of recurrent focal segmental glomerulonephritis with diuretic-resistant edema, she underwent transplant nephrectomy, was restarted on hemodialysis, and had her immunosuppression stopped. Shortly thereafter, the patient presented with pulmonary infiltrates and hemorrhagic stroke with a rapidly fatal course. Autopsy revealed widely disseminated C bertholletiae involving the central nervous system, lungs, and heart. This is the first reported case of endocarditis caused by this organism. Diagnosis of this fungal infection is often difficult. Because the few patients who have survived this infection seemed to have been diagnosed early, it is important for clinicians caring for transplant patients to be aware of this invasive infection. Successful treatment requires prompt diagnosis and high-dose amphotericin B.

Metabolic acidosis in the intensive care unit

Metabolic acidosis is a common occurrence in critically ill patients. Understanding the pathological mechanisms underlying the generation of protons will enable the clinician to quickly recognize these disorders and establish an acceptable treatment strategy. This article presents a logical approach to metabolic acidosis.

Respiratory complications of pregnancy

The pregnant woman is susceptible to a variety of respiratory complications. When a pregnant patient presents with an abnormal chest x-ray or a pulmonary complaint, an understanding of the pathophysiology of pregnancy will guide the clinician in establishing a diagnosis. Pregnancy brings about many changes to a woman's body. One of the more intriguing is a decrease in the T helper cells, resulting in a state of relative immunosuppression. Despite this, the prevalence of infectious pneumonia is not increased in pregnancy. Complications from pneumonia, however, are increased in the pregnant host. Most notably are increases in both mortality related to influenza infection and the risk for dissemination of coccidioidomycosis. Other physiologic changes predispose the pregnant woman to certain disease processes. Hypercoagulability associated with pregnancy results in a marked increase in the incidence of thromboembolic disease. Although rare, pregnancy is also associated with other embolic phenomena including amniotic fluid embolism, air embolism, and trophoblastic embolism. Because of the increases in intravascular volume and cardiac output that occur in pregnancy, women with underlying structural heart disease will frequently present for the first time or have an exacerbation of their disease. This is especially true of mitral stenosis. Peripartum cardiomyopathy also can occur, and for the majority of patients, the heart remains damaged for life. Finally, although uncommon, lymphangioleiomyomatosis will often present or become exacerbated during pregnancy. Patients with this disorder need to be counseled concerning the increased risk associated with pregnancy. This paper reviews the various respiratory complications associated with pregnancy.

Human immunodeficiency virus infection in elderly patients

BACKGROUND

The proportion of older individuals infected with the human immunodeficiency virus (HIV) is rising.

METHODS

We performed a retrospective case-control study of 58 patients more than 60 years old at the time of diagnosis of HIV infection and compared them with 232 controls (matched by CD4+ lymphocyte count). Clinical and demographic data were obtained from the Adult Spectrum of Diseases (ASD) database at the Medical Center of Louisiana.

RESULTS

Patients in the older age group were more likely to be male and African American or Hispanic. The most common risk factor for acquisition of HIV infection among the patients was homosexual contact (53%). Disease staging was similar in both groups as determined by CD4+ lymphocyte counts and history of opportunistic infections. There was no difference in the use of antiretroviral therapy. In a Cox proportional hazard model and regression models, age > or = 60 years was associated with shorter survival.

CONCLUSION

Patients who are older than 60 years at the time of diagnosis of HIV infection have a shorter survival than younger patients.

Residency program director evaluations do not correlate with performance on a required 4th-year objective structured clinical examination

BACKGROUND

Assessment of resident performance is a complex task.

PURPOSE

To correlate performance on a 4th-year objective structured clinical examination (OSCE) with residency program director assessment, class rank, and U.S. Medical Licensing Examination (USMLE) scores.

METHODS

We surveyed program directors about the performance of 50 graduates from our medical school chosen to represent the highest (OSCEHI) and lowest (OSCELO) 25 performers on our required 4th-year OSCE. Program directors were unaware of the OSCE scores of the graduates.

RESULTS

OSCE scores did not correlate with Likert scores for any survey parameter studied (r < .23, p > .13 for all comparisons). Similarly, program director evaluations did not correlate with class rank or USMLE scores (r < .26, p > .09 for all comparisons).

CONCLUSIONS

We concluded that program director evaluations of resident performance do not appear to correlate with objective tests of either clinical skills or knowledge taken during medical school. These findings suggest that more structured and objective evaluative tools might improve postgraduate training program assessment of trainees.

Reemergence of sucrose nephropathy: acute renal failure caused by high-dose intravenous immune globulin therapy

Sucrose nephropathy was first described more than 50 years ago. The disorder is characterized by acute renal failure caused by the uptake of sucrose by renal proximal tubule cells with subsequent cellular swelling and occlusion of the tubule lumen. Approximately 114 cases of renal failure have been associated with high-dose intravenous immune globulin (IVIG) therapy. Almost all cases were caused by preparations containing large amounts of sucrose. Clinicians should consider using IVIG preparations containing no sucrose in patients who are at high risk for renal failure. Risk factors include older age, baseline renal failure, and volume contraction.

Respiratory bronchiolitis: an unusual cause of pulmonary infiltrates in a pregnant woman

Numerous mechanical, biochemical, and immunologic changes occur during pregnancy. Because of these changes, pregnant women are more susceptible to infection, thromboembolic disease, exacerbation of underlying immunologic disease, and heart failure than women who are not pregnant. The differential diagnosis of diffuse pulmonary infiltrates in a pregnant woman is broad; thus, the work-up can be very challenging. If the patient fails to respond to conservative measures, such as antibiotics, the cause of the infiltrate must be aggressively evaluated because the treatment may be essential for the survival of the mother and fetus. We report a case of a pregnant woman who presented with diffuse bilateral infiltrates. After video-assisted thoracoscopic lung biopsy, this patient was found to have respiratory bronchiolitis, a disease not previously reported during pregnancy. Treatment with glucocorticoids resulted in a prompt improvement in symptoms.

Air embolism after intravenous injection of contrast material

Venous air embolism, though considered rare, occurs more frequently than it is recognized. We report the case of a 54-year-old man who was incidentally found to have air in the left brachiocephalic vein and right ventricle after contrast-enhanced computed tomography (CT). Air embolism has been noted to occur after contrast-enhanced CT examination in up to 23% of patients. Because these emboli are small to moderate size and are usually venous, the patients are usually asymptomatic. We review the pathophysiology of air embolization and the recommended treatment.

Anion gap acidosis

Although an anion gap at less than 20 mEq/L rarely has a defined etiology, significant elevations in the anion gap almost always signify presence of an acidosis that can be easily identified. Anion gap acidoses can be divided into those caused by lactate accumulation, ketoacid production, toxin/drugs, and uremia. Lactic acidoses caused by decreased oxygen delivery or defective oxygen utilization are associated with high mortality. The treatment of lactic acidosis is controversial. The use of bicarbonate to increase pH is rarely successful and, by generating PCO2, may worsen outcome. Ketoacidosis is usually secondary to diabetes or alcohol. Treatment is aimed at turning off ketogenesis and repairing fluid and electrolyte abnormalities. Methanol, ethylene glycol, and salicylates are responsible for the majority of toxin-induced anion gap acidoses. Both methanol and ethylene glycol are associated with severe acidoses and elevated osmolar gaps. Treatment of both is alcohol infusion to decrease formation of toxic metabolites and dialyses to remove toxins. Salicylate toxicity usually is associated with a mild metabolic acidosis and a respiratory alkalosis. Uremia is associated with a mild acidosis secondary to decreased ammonia secretion and an anion gap caused by the retention of unmeasured anions. A decrease in anion gap is caused by numerous mechanisms and thus has little clinical utility.

The teaching of cellular and molecular biology: a survey of program directors in internal medicine

PURPOSE

Although there has been an explosion in our knowledge of cellular and molecular biology, it is unclear if medical students entering internal medicine residency programs have been adequately trained in these basic sciences. To ascertain the perceived importance of these subjects to the practice of medicine and to determine if medical schools are properly training their students, a survey was sent to internal medicine program directors.

METHODS

A survey was sent to 401 internal medicine program directors. Repeat questionnaires were sent if no response was received within 6 months.

RESULTS

Questionnaires were returned by 309 program directors (77%). Only 41% of the program directors felt that their residents had received adequate training in cellular and molecular biology. Directors of university programs were significantly more likely to think that knowledge of these sciences was essential to the practice of medicine and that their residents were inadequately trained than directors from nonuniversity programs. Only 30% of programs offered any formal training in these sciences.

CONCLUSION

Medical schools need to reevaluate their curricula in order to integrate the basic sciences into all 4 years. Training in these sciences, however, should not stop with graduation. The importance of a knowledge of these sciences should be emphasized at all training programs.

Analysis of the costs and benefits of using standardized patients to help teach physical diagnosis

BACKGROUND

Although a majority of medical schools use standardized patients (SPs) for teaching or evaluating students, the costs and benefits of such programs have not been examined in depth. In 1992-93 the Tulane University School of Medicine reduced by 40% the faculty-precepted sessions in its physical diagnosis program in order to incorporate seven focused examinations using SPs to teach basic examination skills.

METHOD

Costs for the revised program included costs for SPs, staff, supplies, and faculty. Faculty cost was estimated at a minimum to equal hourly salary and at a maximum to equal this salary plus potential collectible billings. An objective structured clinical examination (OSCE) was used to assess the skill acquisitions of 150 second-year students in 1991-92, before SPs were used, and in 1992-93, when SPs were used. An unpaired t-test was then used to compare the OSCE performances of the two groups of students. Chi-square analysis was used to compare the evaluations of the physical diagnosis program by the 1992-93 and 1991-92 students.

RESULTS

The cost of incorporating SPs into the program was $43,800. The amount of time spent teaching by faculty was reduced by 608 hours, costing between $33 (salary) and $108 (salary plus potential revenue) per hour. Thus, the total savings in the cost of faculty time was between $20,064 and $65,664. Despite the reduction in faculty involvement, the students' performance on the OSCE did not change, and the students' evaluations of the course became significantly more favorable.

CONCLUSION

The incorporation of SPs as instructors in the physical diagnosis program was accomplished at a minimal cost and resulted in an increase in students' enthusiasm for the purpose, with no loss of skill acquisition as measured by the OSCE.

Comparison between acetate and bicarbonate dialysis for the treatment of lithium intoxication

Lithium is used to treat manic-depressive disorders, but toxic side effects commonly occur. The preferred treatment of severe lithium intoxication is hemodialysis. No data, however, exist comparing the effectiveness of acetate to bicarbonate dialysis for the removal of lithium. We present a case of lithium intoxication treated with both. During acetate dialysis, lithium removal occurred exclusively from the extracellular fluid space, while during bicarbonate dialysis, lithium removal occurred equally from both the extracellular and intracellular fluid spaces. We hypothesize that acetate but not bicarbonate activates the sodium-hydrogen antiporter on cell membranes, and that lithium, substituting for sodium, is driven into cells. This may explain the rebound in lithium levels commonly noted after conventional dialysis. We recommend bicarbonate hemodialysis as the therapy of choice for severe lithium intoxication.

Aldosterone-induced glycoproteins: further characterization

Aldosterone induces the synthesis of a group of glycoproteins (GP65,70) in toad urinary bladders which are potential effectors of the natriferic action of this hormone. The GP65,70 complex is composed of two molecular weight classes of proteins (Mr 65 and 70 kDa), each class being composed of several discrete proteins of varying isoelectric points (5.8-6.2). These proteins can be partially enriched (approximately 20-fold) using wheat germ agglutinin-sepharose affinity chromatography, are neuraminidase-resistant, and can be N-deglycosylated by endoglycosidase-H and N-glycanase. Treatment with N-glycanase leads to the appearance of a microheterogeneous group of proteins, all having the same Mr (approximately 40 kDa). From these studies it can be concluded that these particular aldosterone-induced proteins: (1) are heavily glycosylated, (2) contain multiple high mannose and hybrid oligosaccharides side chains, and (3) contain similar (if not identical) peptide backbones. Post-translational N-glycosylation accounts, at least in part, for their electrophoretic polymorphism (variation in Mr) but not for their electrophoretic microheterogeneity (variation in pI). The latter may reflect other types of post-translational modification (e.g. O-glycosylation, phosphorylation) or may be due to subtle differences in amino acid composition. The partial purification and biochemical characterization of GP65,70 should ultimately lead to a better understanding of the function of these putative "effectors" of aldosterone-stimulated Na+ transport.

Aldosterone-induced proteins: purification and localization of GP65,70

Aldosterone stimulates sodium transport in responsive epithelia by inducing "effector" proteins that control or modulate transcellular sodium flux. We have previously identified a group of electrophoretically microheterogeneous (pI 5.8-6.2) and polymorphic (Mr 65 and 70) glycoproteins that are specifically induced by aldosterone in toad urinary bladders (TUBs) and cultured toad kidney cells (A6 cell line). We raised a series of monoclonal antibodies (MAb) to these proteins and, using light and electron immunohistochemistry, localized the higher Mr glycoproteins (GP70) to the apical plasma membrane and subapical granules of the sodium-transporting cell of the TUB epithelium, the granular cell. GP70 appears to be discharged into the bladder lumen; this process is increased by phorbol myristate acetate, an agent known to induce granule exocytosis. These findings are consistent with the possibility that GP70 represent components or modulators of the "high-resistance" renal epithelial sodium channel. MAbs reactive against GP65 did not identify these glycoproteins within TUB epithelial cells; these lower Mr aldosterone-induced proteins may be incompletely processed forms of GP70.

Effect of renal impairment on disposition of pentopril and its active metabolite

Disposition of pentopril was studied in 15 male volunteers with varying renal functions. Mild to moderate compromise in renal function did not demonstrate any appreciable changes in plasma concentration of pentopril, the prodrug ester of the active angiotensin-converting enzyme (ACE) inhibitor CGS 13934. This is consistent with the known elimination pattern for pentopril, which is eliminated primarily by hydrolysis to the active inhibitor. In contrast, the plasma concentration of the active ACE inhibitor was sensitive to moderate changes in renal function. Because of the reciprocal relationship of AUC and clearance, AUC did not change to any appreciable extent until creatinine clearance (CLCR) dropped to about 50 ml/min. Below 50 ml/min of CLCR, AUC and half-life increased sharply with reduced kidney function. Because of the significant contribution of the renal secretion process to total renal elimination of both pentopril and the active metabolite, prediction of renal clearance from CLCR was poor at relatively normal kidney function (CLCR greater than 80 ml/min). However, renal secretory clearances for both pentopril and metabolite were well correlated to p-aminohippuric acid clearance. In patients with moderately compromised renal function (glomerular filtration rate less than 40 ml/min), tubular secretion rate of creatinine approaches its glomerular filtration rate and hence CLCR could be used as a predictor of renal clearance and other disposition parameters. Plasma ACE activity also demonstrated prolonged inhibition with decreased renal function. Based on the prolonged blockade of plasma ACE activity, some correction in dose or dosing interval is anticipated in patients with moderately compromised renal function (CLCR less than 50 ml/min).

Aldosterone-induced glycoproteins: electrophysiological-biochemical correlation

Aldosterone induces the synthesis of a group of glycoproteins (GP65,70) in toad urinary bladders which are potential effectors of the natriferic action of this hormone. In the present study we have confirmed that aldosterone produces a two-phase electrophysiological response. During the early phase (less than 3 h) short-circuit current and transepithelial conductance increase in parallel, while during the late phase (greater than 3 h) short-circuit current continues to increase without any further change in conductance. By biosynthetically labeling aldosterone-treated toad bladders with [35S]methionine either during the early (h 0-2 or 1-3) or the late (h 4-6 or 7-9) phases of the natriferic response, we have demonstrated that GP65,70 is synthesized as a late effect of aldosterone. Since synthesis of GP65,70 occurs at a time when the electromotive force of the Na+ pump is increasing, and since GP65,70 biochemically resembles the beta subunit of Na+/K+-ATPase, studies were undertaken to examine whether GP65,70 is the beta subunit. Purified amphibian renal beta subunit was analyzed by two-dimensional polyacrylamide gel electrophoresis and was found to have an isoelectric point and Mr value similar to those of GP65,70. However, when nitrocellulose blots containing wheat germ agglutinin-purified proteins from aldosterone-treated bladders were stained with monospecific polyclonal antibodies developed against the beta subunit, GP65,70 was not recognized, whereas a group of slightly more acidic proteins of similar Mr were recognized. Thus, GP65,70 is not the beta subunit of Na+/Ka+-ATPase. Further studies are needed to determine the cellular function of GP65,70.

Disorders of potassium homeostasis in critically ill patients

Disorders of potassium homeostasis can be life-threatening. This is especially true in critically-ill patients, in whom concurrent disorders may exacerbate the adverse effects of both hyper- and hypokalemia. Alterations in potassium balance are usually multifunctional in origin. Four broad categories encompass the most common diseases and syndromes seen in the intensive care setting: pharmacologic agents, acid-base disturbances, hypomagnesemia, and renal insufficiency. The various influences that disturb the serum potassium concentration may either potentiate or counter-balance one another. The most important clinical manifestations of disorders of potassium homeostasis are those involving the heart: both hyper- and hypokalemia can be associated with lethal arrhythmias. Neuromuscular, renal and metabolic effects are also seen. Severe hyper- and hypokalemia, irrespective of cause, should be treated as medical emergencies.