The metabolic and respiratory acidosis of acute pulmonary edema

Dialysis-associated hyperglycemia: manifestations and treatment

PURPOSE

Dialysis-associated hyperglycemia (DAH), is associated with a distinct fluid and electrolyte pathophysiology. The purpose of this report was to review the pathophysiology and provide treatment guidelines for DAH.

METHODS

Review of published reports on DAH. Synthesis of guidelines based on these reports.

RESULTS

The following fluid and solute abnormalities have been identified in DAH: (a) hypoglycemia: this is a frequent complication of insulin treatment and its prevention requires special attention. (b) Elevated serum tonicity. The degree of hypertonicity in DAH is lower than in similar levels of hyperglycemia in patients with preserved renal function. Typically, correction of hyperglycemia with insulin corrects the hypertonicity of DAH. (c) Extracellular volume abnormalities ranging from pulmonary edema associated with osmotic fluid shift from the intracellular into the extracellular compartment as a consequence of gain in extracellular solute (glucose) to hypovolemia from osmotic diuresis in patients with residual renal function or from fluid losses through extrarenal routes. Correction of DAH by insulin infusion reverses the osmotic fluid transfer between the intracellular and extracellular compartments and corrects the pulmonary edema, but can worsen the manifestations of hypovolemia, which require saline infusion. (d) A variety of acid-base disorders including ketoacidosis correctable with insulin infusion and no other interventions. (e) Hyperkalemia, which is frequent in DAH and is more severe when ketoacidosis is also present. Insulin infusion corrects the hyperkalemia. Extreme hyperkalemia at presentation or hypokalemia developing during insulin infusion require additional measures.

CONCLUSIONS

In DAH, insulin infusion is the primary management strategy and corrects the fluid and electrolyte abnormalities. Patients treated for DAH should be monitored for the development of hypoglycemia or fluid and electrolyte abnormalities that may require additional treatments.

Benefits of non-invasive ventilation in acute hypercapnic respiratory failure

Non-invasive ventilation (NIV) with bilevel positive airway pressure is a non-invasive technique, which refers to the provision of ventilatory support through the patient's upper airway using a mask or similar device. This technique is successful in correcting hypoventilation. It has become widely accepted as the standard treatment for patients with hypercapnic respiratory failure (HRF). Since the 1980s, NIV has been used in intensive care units and, after initial anecdotal reports and larger series, a number of randomized trials have been conducted. Data from these trials have shown that NIV is a valuable treatment for HRF. This review aims to explore the principal areas in which NIV can be useful, focusing particularly on patients with acute HRF (AHRF). We will update the evidence base with the goal of supporting clinical practice. We provide a practical description of the main indications for NIV in AHRF and identify the group of patients with hypercapnic failure who will benefit most from the application of NIV.

Hyperglycemic Crisis in an Anuric Peritoneal Dialysis Patient with Profound and Symptomatic Hypertonicity

An anuric peritoneal dialysis patient with diabetes mellitus, congestive heart failure, and anasarca developed severe hyperglycemia with hypertonicity causing profound neurological manifestations after prolonged and continuous use of hypertonic (4.25%) dextrose dialysate. She expired with hypotensive shock from a new myocardial infarction soon after completion of treatment with insulin infusion. The degree of the presenting hypertonicity far exceeded the value expected from the degree of hyperglycemia. We identified prolonged peritoneal dialysis with hypertonic solutions and profound extracellular volume expansion as the causes of the excessive hypertonicity. Hyperglycemia developing in diabetic patients treated for anasarca by peritoneal dialysis after continuous use of hypertonic dextrose dialysate is associated with the risk of excessive hypertonicity with severe clinical manifestations.

Respiratory failure in diabetic ketoacidosis

Respiratory failure complicating the course of diabetic ketoacidosis (DKA) is a source of increased morbidity and mortality. Detection of respiratory failure in DKA requires focused clinical monitoring, careful interpretation of arterial blood gases, and investigation for conditions that can affect adversely the respiration. Conditions that compromise respiratory function caused by DKA can be detected at presentation but are usually more prevalent during treatment. These conditions include deficits of potassium, magnesium and phosphate and hydrostatic or non-hydrostatic pulmonary edema. Conditions not caused by DKA that can worsen respiratory function under the added stress of DKA include infections of the respiratory system, pre-existing respiratory or neuromuscular disease and miscellaneous other conditions. Prompt recognition and management of the conditions that can lead to respiratory failure in DKA may prevent respiratory failure and improve mortality from DKA.

Severe but not mild hypercapnia affects the outcome in patients with severe cardiogenic pulmonary edema treated by non-invasive ventilation

Background

Patients with severe cardiogenic pulmonary edema (CPE) are frequently hypercapnic, possibly because of associated underlying chronic lung disease (CLD). Since hypercapnia has been associated with outcome, we aimed to identify factors associated to hypercapnia and its role on outcome of patients with CPE and no underlying CLD.

Methods

Observational cohort study using data prospectively collected over a 3-year period. After excluding patients with any CLD or obstructive sleep apneas, all patients treated by non-invasive ventilation (NIV) for severe CPE were included. Hypercapnia was defined as PaCO₂ >45 mmHg and non-rapid favorable outcome was defined as the need for intubation or continuation of NIV for more than 48 h.

Results

After excluding 60 patients with underlying CLD or sleep apneas, 112 patients were studied. The rates of intubation and of prolonged NIV were 6.3 % (n = 7) and 21.4 % (n = 24), respectively. Half of the patients (n = 56) had hypercapnia upon admission. Hypercapnic patients were older, more frequently obese, and were more likely to have a respiratory tract infection than non-hypercapnic patients. Hypercapnia had no influence on intubation rate or the need for prolonged NIV. However, patients with severe hypercapnia (PaCO₂ >60 mmHg) needed longer durations of NIV and intensive care unit (ICU) stay than the others.

Conclusions

Among the patients admitted for severe CPE without CLD, half of them had hypercapnia at admission. Hypercapnic patients were older and more frequently obese but their outcome was similar compared to non-hypercapnic patients. Patients with severe hypercapnia needed longer durations of NIV than the others without increase in intubation rate.

Hypercapnia in patients with acute heart failure

AIMS

Non-invasive positive pressure ventilation rapidly improves the symptoms of acute heart failure (AHF). A portion of patients, however, are forced to be intubated even though intubation is associated with serious complications, and hypercapnia is often observed in AHF requiring intubation. The purpose of this study is to examine the clinical profile and management of hypercapnia in AHF patients.

METHODS AND RESULTS

We examined the arterial blood gas analysis in 193 consecutive AHF patients (73 ± 12 years, 61% men) at admission. Many patients (n = 129, 66.8%) had already been treated with oxygen by the ambulance staff. Hypercapnia (PaCO2 at admission >45 mmHg) and hypocapnia (PaCO2  < 35 mmHg) were observed in 33.7% and 32.6%, respectively. Whereas 16 (24.6%) hypercapnic patients were intubated, there were only one (1.5%) normocapnic and no hypocapnic patients intubated. Patients with hypercapnia are more likely to be in the New York Heart Association Class IV (96.9% vs. 78.9%, P < 0.001), to have acute onset within 6 h (50.8% vs. 25.0%, P < 0.001), and to have radiographic pulmonary oedema (84.6% vs. 57.8%, P < 0.001) than those with hypo-normocapnia. Hypercapnia was more frequent in patients with acute cardiogenic pulmonary oedema than in those with acute decompensated heart failure (51.9% vs. 23.6%, P < 0.001). At discharge, hypercapnia was observed in 17.8% of patients who were hypercapnic at admission.

CONCLUSION

Hypercapnia emerged in AHF acutely and transiently, was associated with immediate airway intervention, and was possibly involved in the pathophysiology of acute pulmonary oedema. Patients with acute onset dyspnoea should have their respiratory status carefully managed. These pathophysiological findings are expected to be utilized in treating or preventing AHF.

Non-invasive ventilation in acute cardiogenic pulmonary oedema

Non-invasive ventilation (NIV) is the delivery of assisted mechanical ventilation to the lungs, without the use of an invasive endotracheal airway. NIV has revolutionised the management of patients with various forms of respiratory failure. It has decreased the need for invasive mechanical ventilation and its attendant complications. Cardiogenic pulmonary oedema (CPO) is a common medical emergency, and NIV has been shown to improve both physiological and clinical outcomes. From the data presented herein, it is clear that there is sufficiently high level evidence to favour the use of continuous positive airway pressure (CPAP), and that the use of CPAP in patients with CPO decreases intubation rate and improves survival (number needed to treat seven and eight respectively). However, there is insufficient evidence to recommend the use of bilevel positive airway pressure (BiPAP), probably the exception being patients with hypercapnic CPO. More trials are required to conclusively define the role of BiPAP in CPO.

Serum potassium and acid-base parameters in severe dialysis-associated hyperglycemia treated with insulin therapy

We analyzed the changes in serum potassium concentration ([K]) and acid-base parameters in 43 episodes of dialysis-associated hyperglycemia (serum glucose level > 33.3 mmol/L), 22 of which were characterized as diabetic ketoacidosis (DKA) and the remaining 21 as nonketotic hyperglycemia (NKH). All episodes were treated with insulin therapy only. Age, gender, initial and final serum values of glucose, sodium, chloride, tonicity and osmolality did not differ between DKA and NKH. At presentation, serum values of [K] (DKA 6.2 +/- 1.3 mmol/L; NKH 5.2 +/- 1.5 mmol/L) and anion gap [AG] (DKA 27.2 +/- 6.4 mEq/L; NKH 15.4 +/- 3.5 mEq/L) were higher in DKA, whereas serum total carbon dioxide content [TCO2 ] (DKA 12.0 +/- 4.6 mmol/L; NKH 22.5 +/- 3.1 mmol/L), arterial blood pH (DKA 7.15 +/- 0.09; NKH 7.43 +/- 0.07) and arterial blood PaCO2 (DKA 26.2 +/- 12.3 mm Hg; NKH 34.5 +/- 6.7 mm Hg) were higher in NKH. At the end of insulin treatment, serum values of [K] (DKA 4.0 +/- 0.7 mmol/L, NKH 4.0 +/- 0.5 mmol/L), [AG] (DKA 16.3 +/- 5.4 mEq/L, NKH 14.9 +/- 3.0 mEq/L), [TCO2 ] (DKA 23.5 +/- 5.0 mmol/L, NKH 24.1 +/- 4.2 mmol/L), arterial blood pH (DKA 7.42 +/- 0.09, NKH 7.51 +/- 0.14) and arterial blood PaCO2 (DKA 31.8 +/- 6.7 mm Hg, NKH 34.2 +/- 8.3 mm Hg) did not differ between the two groups. Linear regression of the decrease in serum [K] value during treatment, (Delta[K]), on the presenting serum [K] concentration,([K]2 ), was: DKA, Delta[K] = 2.78 - 0.81 x [K]2 , r = -0.85, p < 0.001; NKH, Delta[K] = 2.44 - 0.71 x [K]2 , r = -0.90, p < 0.001. The slopes of the regressions were not significantly different. Stepwise logistic regression including both DKA and NKH cases identified the presenting serum [K] level and the change in serum [TCO2 ] value during treatment as the predictors of Delta[K] (R2 = 0.81). Hyperkalemia is a feature of severe hyperglycemia (DKA or NKH) occurring in patients on dialysis. Insulin administration brings about correction of DKA and return of serum [K] concentration to the normal range in the majority of the hyperglycemic episodes without the need for other measures. The initial serum [K] value and the change in serum [TCO2 ] level during treatment influence the decrease in serum [K] value during treatment of dialysis-associated hyperglycemia with insulin.

Pharmacological therapy of acute cardiogenic pulmonary oedema in the emergency department

This paper critically reviews the major drug types that are currently used in the management of acute cardiogenic pulmonary oedema. As decompensated heart failure becomes an increasingly common problem in emergency departments in the developed world, optimization of emergency drug therapy for these critically ill patients is essential. The evidence base for 'routine therapy' in the ED is considered. The review also briefly considers emerging pharmacological therapies that may have an impact on future management of cardiogenic pulmonary oedema.

Risk factors for intubation as a guide for noninvasive ventilation in patients with severe acute cardiogenic pulmonary edema

OBJECTIVE

Noninvasive ventilation may reduce the endotracheal intubation rate in patients with acute cardiogenic pulmonary edema. However, criteria for selecting candidates for this technique are not well established. We analyzed a cohort of patients with severe acute cardiogenic pulmonary edema managed by conventional therapy to identify risk factors for intubation. These factors were used as guide for indications for noninvasive ventilation.

DESIGN AND SETTING

Observational cohort registry in the ICU and emergency and cardiology departments in a community teaching hospital.

PATIENTS

. 110 consecutive patients with acute cardiogenic pulmonary edema, 80 of whom received conventional oxygen therapy.

INTERVENTIONS

Physiological measurements and blood gas samples registered upon admission.

MEASUREMENTS AND RESULTS

Twenty-one patients (26%) treated with conventional oxygen therapy needed intubation. Acute myocardial infarction, pH below 7.25, low ejection fraction (<30%), hypercapnia, and systolic blood pressure below 140 mmHg were independent predictors for intubation. Conversely, systolic blood pressure of 180 mmHg or higher showed to be a protective factor since only two patients with this blood pressure value required intubation (8%)], both presenting with a pH lower than 7.25. Considering systolic blood pressure lower than 180 mmHg, patients who showed hypercapnia presented a high intubation rate (13/21, 62%) whereas the rate of intubation in patients with normocapnia was intermediate (6/23, 26%). All normocapnic patients with pH less than 7.25 required intubation. No patient with hypocapnia was intubated regardless the level of blood pressure.

CONCLUSIONS

Patients with pH less than 7.25 or systolic blood pressure less than 180 mmHg associated with hypercapnia should be promptly considered for noninvasive ventilation. With this strategy about 40% of the patients would be initially treated with this technique, which would involve nearly 90% of the patients that require intubation.

Blood gas analysis

Evaluation of both arterial and central venous blood can be valuable in monitoring the critically ill veterinary patient. The traditional approach, which concentrates on arterial blood analysis only, may miss important aspects of oxygen delivery to tissues, especially in patients with poor perfusion. The advances that have resulted in affordable bedside blood gas analyzers have created a clinical situation in which blood gas analysis should be an integral part of critical care monitoring. Following basic principles of interpretation, blood gas analysis, which has traditionally been viewed as a complex method of monitoring, should become more useful. Assessing both the arterial and central venous samples should result in more efficient and higher quality care for veterinary patients.

Fatal postoperative pulmonary edema: pathogenesis and literature review

STUDY OBJECTIVES

Pulmonary edema is a known postoperative complication, but the clinical manifestations and danger levels for fluid administration are not known. We studied (1) 13 postoperative patients (11 adult, 2 pediatric) who developed fatal pulmonary edema, and (2) one contemporaneous year of inpatient operations at two university teaching hospitals to determine the clinical manifestations, causes, epidemiology, and guidelines for fluid administration.

DESIGN

Retrospective analysis of 13 patients with fatal postoperative pulmonary edema and one contemporaneous year of major inpatient surgery.

PATIENTS AND METHODS

Thirteen patients had net fluid retention of at least 67 mL/kg in the initial 24 postoperative hours and developed pulmonary edema. Ten were generally healthy while three had serious associated medical conditions.

MEASUREMENTS AND RESULTS

There was no measurement, laboratory value, or clinical finding predictive of impending pulmonary edema. The most common clinical manifestation following the onset of pulmonary edema was cardiorespiratory arrest (n = 8). Patients had metabolic acidosis (pH = 7.15 +/- .33), hypoxia (PO2 = 45 +/- 18 mm Hg), and normal electrolytes. The diagnosis of pulmonary edema was established by chest radiograph and confirmed by autopsy and pulmonary artery pressure (21 +/- 4 mm Hg). The mean net fluid retention was 7.0 +/- 4.5 L (90 +/- 36 mL/kg/d) and exceeded 67 mL/kg/d in all patients. Autopsy revealed pulmonary edema with no other cause of death. Among 8,195 major operations, 7.6% developed pulmonary edema with a mortality of 11.9%. Extrapolation to the 8.2 million annual major surgeries in the United States yields a projection of 8,000 to 74,000 deaths.

CONCLUSIONS

Pulmonary edema can occur within the initial 36 postoperative hours when net fluid retention exceeds 67 mL/kg/d. There are no known predictive warning signs and cardiorespiratory arrest is the most frequent clinical presentation. The monitoring systems currently in use neither detect nor predict impending pulmonary edema, and as yet, there are no known panic values for excessive fluid administration or retention.

Nitrate therapy is an alternative to furosemide/morphine therapy in the management of acute cardiogenic pulmonary edema

BACKGROUND

Nitrates are superior to furosemide in the management of acute pulmonary edema associated with myocardial infarction; however, their role in the absence of infarction is unclear.

METHODS AND RESULTS

A randomized comparison was undertaken of the relative effectiveness of primary therapy with either intravenous morphine/furosemide (men/women; n = 32) or nitroglycerin/N-acetylcysteine (NTG/NAC; n = 37) in consecutive patients with acute pulmonary edema. The primary end point was change in PaO2/FIO2 over the first 60 minutes of therapy. Secondary end points were needed for mechanical respiratory assistance (ie, continuous positive airway pressure via mask or intubation and ventilation) and changes in other gas exchange parameters. Both treatment groups showed improvement in oxygenation after 60 minutes of therapy; however, this reached statistical significance only with NTG/NAC therapy. There was no significant difference between groups in the assessed parameters (95% CI for differences in Pao2/FIO2: furosemide/morphine -12 to 23 and NTG/NAC 4 to 44), a finding also confirmed in 32 patients presenting with respiratory failure. Only 11% of the study group required mechanical ventilatory assistance (continuous positive airway pressure in 4 patients and intubation and ventilation in 3 patients).

CONCLUSIONS

NTG/NAC therapy is as effective as furosemide/morphine in the initial management of acute pulmonary edema, regardless of the presence or absence of respiratory failure. The necessity for mechanical ventilatory assistance is infrequent in these patients, regardless of the initial medical treatment regimen.

Flow diagrams for the diagnosis of acid-base disorders

This article discusses flow diagrams and tables intended to provide a systematic approach to the rapid laboratory differential diagnosis of acid-base disorders in the emergency department.

Pulmonary complications of hyponatremic encephalopathy. Noncardiogenic pulmonary edema and hypercapnic respiratory failure

OBJECTIVE

To determine the causes of hypoxia in patients with hyponatremic encephalopathy.

DESIGN

Retrospective cohort study.

SETTING

Consultation and referral service of two university medical centers and community hospitals.

PATIENTS

Forty adults with postoperative hyponatremic encephalopathy and hypoxia of whom 30 had noncardiogenic pulmonary edema and 10 had hypercapnic respiratory failure.

MAIN MEASUREMENTS

We evaluated the chest radiographs and measured plasma electrolytes, arterial blood gas values, pulmonary artery pressure, pulmonary capillary wedge pressure (PCWP), cardiac output, and net fluid retention.

RESULTS

Forty patients with hyponatremic encephalopathy had hypoxia (arterial PO2 below 70 mm Hg), of whom 30 had pulmonary edema and 10 had hypercapnia (PCO2 above 50 mm Hg). Among the 30 patients with pulmonary edema, the serum sodium (+/- SD) was 114 +/- 7 mmol/L, arterial pH was 7.24 +/- 0.16, PCO2 was 45 +/- 15 mm Hg, and PO2 was 42 +/- 16 mm Hg. The cardiac index was 3.6 +/- 0.4 L/min/M2, pulmonary artery pressure was 26/16 mm Hg, and PCWP was 12 +/- 6 mm Hg. There was pulmonary edema, with normal heart size. The hypoxic patients who did not have pulmonary edema had significant hypercapnia (PCO2 = 91 +/- 29 mm Hg, p < 0.001).

CONCLUSIONS

Patients with postoperative hyponatremic encephalopathy can develop hypoxia by at least two different mechanisms: noncardiogenic pulmonary edema or hypercapnic respiratory failure.

Respiratory muscle fatigue from functional upper airway obstruction

A case of functional upper airway obstruction is presented. The case is unusual because even though no identifiable organic cause could be found for dyspnea and stridor, the patient developed respiratory failure from respiratory muscle fatigue.

Acid-base disorders in hyperglycemia of insulin-dependent diabetic patients on chronic dialysis

The authors studied hyperglycemia occurring in insulin-dependent diabetic patients on chronic dialysis to determine the types of associated acid-base disorders, their treatment, and any differences from hyperglycemia in diabetic patients with intact renal function. Eighty-eight episodes of serum glucose greater than 25 mmol/L were observed, 23 in hemodialysis patients and 65 in patients on continuous peritoneal dialysis. Treatment consisted of low-dose insulin in 77 episodes and low-dose insulin plus saline in 11; no base was administered. Seventeen episodes (19%) presented with ketoacidosis. Arterial blood gas determinations were carried out at presentation in 37 of the episodes without ketoacidosis. Of these, 12 had respiratory alkalosis, six had respiratory acidosis and severe pulmonary edema, 14 had other single or mixed acid-base disorders, and only five had normal acid-base status. Insulin corrected the ketoacidosis in all instances and both pulmonary edema and respiratory acidosis in five of six instances. In eight cases metabolic alkalosis developed during treatment, without external acid loss. At the completion of treatment respiratory alkalosis was present in half the cases. No difference was noted between patients treated with hemodialysis or peritoneal dialysis. Insulin alone is sufficient for the management of hyperglycemia in dialysis patients. Certain acid-base disorders persist, but do not need further treatment. Hyperglycemia in patients on dialysis is characterized by infrequent development of metabolic acidosis and frequent presentation with respiratory alkalosis, by respiratory acidosis that is corrected by insulin, and by metabolic alkalosis developing during treatment without external cause.

Pathophysiology of type A hypoxic lactic acidosis in dogs

Hypoxic lactic acidosis (HLA) was induced in dogs by ventilating them with a hypoxic gas mixture of 8% O2-92% N2. The animals were studied both in the control state and after development of HLA, where arterial lactate was above 5 mM, pH was below 7.2, bicarbonate was below 12 mM, and arterial PO2 was between 26 and 30 Torr. After hypoxia had been present for 90 min, most of the increase in arterial lactate vs. control was due to increased lactate production from gut and carcass in the presence of a decreased capacity of the liver to extract lactate. The capacity of the liver to extract lactate in the normoxic state was evaluated in another group of six dogs after infusion of L-lactic acid such that arterial pH, lactate, and bicarbonate were similar to hypoxic values. In these experiments it was found that the capacity of the liver to extract lactate was 14.8 +/- 1.7% of the delivered load vs. 4.9 +/- 1.3% observed in hypoxic animals. The decreased liver lactate extraction in HLA was probably secondary to both a decrease in liver oxygen uptake and a decrease in liver intracellular pH and was paralleled by an increase in liver tissue lactate levels. Cardiac output, in contrast to other forms of lactic acidosis, was increased by 40% vs. control and femoral artery flow by 35%, whereas liver blood flow was unchanged and renal blood flow decreased. Hypoxic lactic acidosis thus is the consequence of overproduction of lactate by both gut and carcass, in the presence of impaired utilization of lactate by the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Hospital and long-term survival of patients with acute pulmonary edema associated with coronary artery disease

Cardiogenic acute pulmonary edema (APE) associated with coronary artery disease was diagnosed in 44 patients admitted over a 1-year period to a general university hospital. The patients' clinical characteristics at presentation were variable. Acute myocardial infarction (AMI) was present in 26 patients (59%). The hospital mortality rate was 46% (12 of 26 patients) in the presence of AMI and 6% (1 of 18) in its absence (p = 0.006). Long-term follow-up of all hospital survivors revealed that 8 of 30 (27%) had died at 1 year and that 21 of 30 patients (70%) had died at 6 years. However, there was no significant difference in subsequent survival between the AMI and non-AMI groups. A history of congestive heart failure was selected as the most important predictor of increased mortality risk by univariate analysis of the clinical characteristics of the hospital survivors (p = 0.02). The mortality rate at 6 years of follow-up was 85% (17 of 20 patients) in the presence of a history of congestive heart failure and 40% (6 of 10) in its absence.

Evidence for a detrimental effect of bicarbonate therapy in hypoxic lactic acidosis

Lactic acidosis, a clinical syndrome caused by the accumulation of lactic acid, is characterized by lactate concentration in blood greater than 5 mM. Therapy usually consists of intravenous sodium bicarbonate (NaHCO3), but resultant mortality is greater than 60 percent. The metabolic and systemic effects of NaHCO3 therapy of hypoxic lactic acidosis in dogs were studied and compared to the effects of sodium chloride or no therapy. Sodium bicarbonate elevated blood lactate concentrations to a greater extent than did either sodium chloride or no treatment. Despite the infusion of NaHCO3, both arterial pH and bicarbonate concentration decreased by a similar amount in all three groups of dogs. Additional detrimental effects of NaHCO3 were observed on the cardiovascular system, including decreases in cardiac output and blood pressure that were not observed with either sodium chloride or no treatment. Thus there is evidence for a harmful effect of NaHCO3 in the treatment of hypoxic lactic acidosis.

The mechanism of CO2 retention in cardiac pulmonary edema

We studied a 58-year-old woman during an acute episode of cardiac pulmonary edema complicated by carbon dioxide (CO2) retention. As pulmonary wedge pressure became greater, metabolic production of CO2 increased by 38 ml/min and minute ventilation by 1.53 L; by contrast, alveolar ventilation remained unchanged due to a concomitant rise in physiologic dead space and, as a result, arterial CO2 tension increased up to 61 mm Hg. With treatment, all these variables returned to baseline values. Subsequent measurement of mouth occlusion pressure (p 0.1) during a CO2 rebreathing trial showed that neuromuscular inspiratory drive response to CO2 was preserved, but that ventilatory response was markedly reduced, presumably because of the severe restrictive and obstructive ventilatory defect and of the loss of inspiratory muscle force demonstrated in the patient. We conclude that CO2 retention in cardiac pulmonary edema involves a combination of: (1) increased CO2 production, (2) rise in physiologic dead space, and (3) severe respiratory mechanical impairment.

Out-of-hospital pulmonary edema: diagnosis and treatment

Sixty-two patients diagnosed by paramedics as having acute cardiac pulmonary edema out of the hospital were studied. The paramedic prehospital diagnosis as confirmed by an emergency physician, chest film, and hospital admission evaluation was correct in 55 of 62 patients (89%). In the group with acute cardiac pulmonary edema, 64% demonstrated cardiac dysrhythmias, including cardiac arrest, prior to the patient's hospitalization. Therapy administered by the paramedics was beneficial in that most patients had improved on arrival at the hospital. Six of the 10 patients (60%) sustaining cardiac arrest were successfully resuscitated. Acute cardiac pulmonary edema occurring outside the hospital is commonly associated with significant complications, including life-threatening arrhythmias. Well-trained paramedics are capable of quickly diagnosing and treating acute cardiac pulmonary edema outside the hospital setting.

Cardiogenic pulmonary edema

Cardiogenic pulmonary edema is a medical emergency and must be treated quickly and aggressively with oxygen and intravenous medications. Hemodynamic improvement may precede clinical improvement by several hours.

Compensatory hypoventilation in metabolic alkalosis

Although hyperventilation is a well-known compensatory mechanism in metabolic acidosis, compensatory hypoventilation has been inconsistent and controversial in metabolic alkalosis. Six healthy subjects were studied under baseline conditions and during steady-state metabolic acidosis (seven episodes) and alkalosis (14 episodes). Minute ventilation (VE) fell in metabolic alkalosis and rose in metabolic acidosis. These changes in ventilation were entirely due to reduction and elevation of tidal volume (VT) respectively, while respiratory frequency (f) remained unchanged. Alveolar ventilation fell during metabolic alkalosis and resulted in elevation of arterial PCO2 in all subjects. The ventilatory response to arterial PCO2 in all subjects. The ventilatory response to CO2 breathing was also diminished. There was a linear relationship between PaCO2 and plasma [HCO-3] in metabolic acidosis and alkalosis which was defined as PaCO2 (mm Hg = 0.7 [HCO-a] + 20 (+/- SEM), r = 0.95. Although arterial PO2 and plasma [K+] fell during metabolic alkalosis, minute ventilation did not change upon breathing oxygen and there was no correlation between changes in plasma [K+] and plasma H+ regulation.

Kinetic disposition and diuretic effect of frusemide in acute pulmonary oedema

The kinetic disposition and diuretic effect of frusemide was assessed in 16 patients with acute pulmonary oedema utilizing a specific gas-liquid chromatographic assay for the drug. Serum frusemide concentrations decayed biexponentially with wide variation in both alpha half-life (range 15-79 min) and beta half-life (range 127-1190 min). The beta phase half-life was inversely related to creatine clearance. The apparent volume of distribution varied greatly among the patients (range 0.085-0.818 l/kg), and patients with an acute myocardial infarction had a larger peripheral kinetic compartment. Patients with acute myocardial infarction excreted less unchanged drug and had a lesser urinary excretion of sodium and volume compared to patients without infarction. The urinary excretion of sodium, chloride, calcium and volume was linearly related to the urinary excretion of unchanged frusemide.

Increases in plasma oncotic pressure during acute cardiogenic pulmonary edema

Colloid osmotic pressure (COP) was measured in 95 patients with clinical and radiological evidence of acute cardiogenic pulmonary edema. Fifty patients who were admitted for coronary observation but in whom acute myocardial infarctin was excluded, and 21 patients who had sustained acute myocardial infarction without evidence of left ventricular failure served as controls. Significantly higher values of COP, total plasma protein, and hematocrit were observed in patients with pulmonary edema. Increases in COP during pulmonary edema were best explained by transudation of hypooncotic fluid into extravascular spaces. Following treatment of pulmonary edema in 76 patients with furosemide, morphine, and oxygen, pulmonary edema was reversed in 65 patients. Reabsorption of hypooncotic fluid from extravascular sites with a significant decline in COP, total protein and hematocrit followed reversal of pulmonary edema. No significant changes in these parameters were observed in patients who failed to respond to therapy. These observations implicate filtration of hypooncotic fluid from the intravascular compartment during onset of cardiogenic pulmonary edema and reabsorption of hypooncotic fluid into the intravascular compartment during reversal of pulmonary edema.

Arterial blood gases in acute pulmonary edema

Arterial blood gas and pH measurements in 82 patients with acute pulmonary edema of cardiogenic origin entering the emergency department varied widely and were unpredictable using clinical examination. The mean arterial oxygen tension (PaO2) measured in 71 patients breathing room air was 59 mm Hg. Fourteen of the 82 patients were acidemic; 35, alkalemic and 33 had a pH in the normal range. The acidemic group had markedly lower PaO2, all under 60 mm Hg. Oxygen and furosemide were used in all cases and effectively corrected the hypoxia and reduced pulmonary congestion. Other drugs used included aminophylline (14 patients), morphine sulfate (9 patients) and digoxin (3 patients). Five of the nine patients who received morphine were hypercarbic initially but the CO2 retention did not worsen. No patient died during the initial 48 hours. This study reiterates the importance of directing therapy at ventilatory and cardiac abnormalities and points out the value of arterial blood gas monitoring to assess the initial status, monitor the patient's course, and to select drug therapy.