Life-threatening asthma in children: treatment with sodium bicarbonate reduces PCO2

Acute sodium bicarbonate administration improves ventilatory efficiency in experimental respiratory acidosis: clinical implications

Administering sodium bicarbonate (NaHCO3) to patients with respiratory acidosis breathing spontaneously is contraindicated because it increases carbon dioxide load and depresses pulmonary ventilation. Nonetheless, several studies have reported salutary effects of NaHCO3 in patients with respiratory acidosis but the underlying mechanism remains uncertain. Considering that such reports have been ignored, we examined the ventilatory response of unanesthetized dogs with respiratory acidosis to hypertonic NaHCO3 infusion (1 N, 5 mmol/kg) and compared it with that of animals with normal acid-base status or one of the remaining acid-base disorders. Ventilatory response to NaHCO3 infusion was evaluated by examining the ensuing change in PaCO2 and the linear regression of the PaCO2 vs. pH relationship. Strikingly, PaCO2 failed to increase and the ΔPaCO2 vs. ΔpH slope was negative in respiratory acidosis, whereas PaCO2 increased consistently and the ΔPaCO2 vs. ΔpH slope was positive in the remaining study groups. These results cannot be explained by differences in buffering-induced decomposition of infused bicarbonate or baseline levels of blood pH, PaCO2, and pulmonary ventilation. We propose that NaHCO3 infusion improved the ventilatory efficiency of animals with respiratory acidosis, i.e., it decreased their ratio of total pulmonary ventilation to carbon dioxide excretion (VE/VCO2). Such exclusive effect of NaHCO3 infusion in animals with respiratory acidosis might emanate from baseline increased VD/VT (dead space/tidal volume) caused by bronchoconstriction and likely reduced pulmonary blood flow, defects that are reversed by alkali infusion. Our observations might explain the beneficial effects of NaHCO3 reported in patients with acute respiratory acidosis.

Sodium bicarbonate therapy for acute respiratory acidosis

PURPOSE OF REVIEW

Respiratory acidosis is commonly present in patients with respiratory failure. The usual treatment of hypercapnia is to increase ventilation. During the recent surge of COVID-19, respiratory acidosis unresponsive to increased mechanical ventilatory support was common. Increasing mechanical ventilation comes at the expense of barotrauma and hemodynamic compromise from increasing positive end-expiratory pressures or minute ventilation. Treating acute respiratory acidemia with sodium bicarbonate remains controversial.

RECENT FINDINGS

There are no randomized controlled trials of administration of sodium bicarbonate for respiratory acidemia. A recent review concluded that alkali therapy for mixed respiratory and metabolic acidosis might be useful but was based on the conflicting and not conclusive literature regarding metabolic acidosis. This strategy should not be extrapolated to treatment of respiratory acidemia. Low tidal volume ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) has beneficial effects associated with permissive hypercapnia. Whether the putative benefits will be negated by administration of alkali is not known. Hypercapnic acidosis is well tolerated, with few adverse effects as long as tissue perfusion and oxygenation are maintained.

SUMMARY

There is a lack of clinical evidence that administration of sodium bicarbonate for respiratory acidosis has a net benefit; in fact, there are potential risks associated with it.

Insulin therapy in hyperglycemic children with severe acute asthma

OBJECTIVES

The aim of this study was to assess the effect of intravenous (IV) insulin administration in children with severe acute asthma (SAA) and hyperglycemia on IV salbutamol consumption and length of stay (LOS) in a pediatric intensive care unit (PICU).

METHODS

Retrospective, descriptive study of the clinical course before and after implementation of an insulin protocol for the treatment of hyperglycemia (i.e. blood glucose >8 mmol/L or 144 mg/dL, respectively) in the PICU of a tertiary care university hospital. Admissions between 1994 and 2010 were reviewed. The insulin protocol was introduced in 2006.

RESULTS

A total of 131 pediatric patients with SAA complicated by hyperglycemia requiring IV salbutamol were included. Severity of illness before and after implementation of the insulin protocol did not significantly differ. The insulin-treated patient group had significantly higher maximum blood glucose levels and higher cumulative IV salbutamol dose than the non-treated group. There were no differences between these groups in the duration of IV salbutamol administration and LOS.

CONCLUSIONS

In view of the lack of difference in outcomes and considering that the insulin protocol is labor-intensive, the question is whether this protocol is efficacious for the treatment of pediatric SAA associated with hyperglycemia.

Management of status asthmaticus in children

Recent literature on paediatric status asthmaticus (PSA) confirms an increasing percentage of admissions to paediatric intensive care units. PSA is a medical emergency that can be fatal and needs careful and prompt intervention. The severity of PSA is mainly determined by clinical judgement of signs and symptoms. Peak flow measurements and serial lung function measurements are not reliable in PSA. Validated clinically useful instruments are lacking. The three main factors that are involved in the pathophysiology of PSA, bronchoconstriction, mucus plugging and airway inflammation need to be addressed to optimise treatment. Initial therapies include supplementation of oxygen, repetitive administration of rapid acting β2-agonists, inhaled anticholinergics in combination with systemic glucocorticosteroids and intravenous magnesium sulphate. Additional treatment modalities may include methylxanthines, DNase, ketamine, sodium bicarbonate, heliox, epinephrine, non-invasive respiratory support, mechanical ventilation and inhalational anaesthetics.

Management of severe asthma exacerbation in children

BACKGROUND

Asthma is a common disease in children and acute severe asthma exacerbation can be life-threatening. This article aims to review recent advances in understanding of risk factors, pathophysiology, diagnosis and treatment of severe asthma exacerbation in children.

DATA SOURCES

Articles concerning severe asthma exacerbation in children were retrieved from PubMed. Literatures were searched with MeSH words "asthma", "children", "severe asthma exacerbation" and relevant cross references.

RESULTS

Severe asthma exacerbation in children requires aggressive treatments with β2-agonists, anticholinergics, and corticosteroids. Early initiation of inhaled β-agonists and systemic use of steroids are recommended. Other agents such as magnesium and aminophylline have some therapeutic benefits. When intubation and mechanical ventilation are needed, low tidal volume, controlled hypoventilation with lower-than-traditional respiratory rates and permissive hypercapnia can be applied.

CONCLUSIONS

Researchers should continue to detect the risk factors, pathophysiology, diagnosis and treatment of severe asthma exacerbation in children. More studies especially randomized controlled trials are required to evaluate the efficacy and safety of standard and new therapies.

Outcome of children with life-threatening asthma necessitating pediatric intensive care

OBJECTIVE

To report the outcome of children with life-threatening asthma (LTA) admitted to a university Pediatric Intensive Care Unit (PICU).

METHODS

Retrospective study between October 2002 and May 2010 was carried out. Every child with LTA and bronchospasm was included.

RESULTS

30 admissions of 28 patients (13 M, 17 F) were identified which accounted for 3% of total PICU admissions (n = 1033) over the study period. The majority of patients were toddlers (median age 3.1 years). Few had past history of prematurity, lung diseases, or neuro-developmental conditions. Approximately half had previous admissions for asthma and one-forth with history of non-compliance to recommended treatment for asthma. One patient had parainfluenza virus and one had rhinovirus isolated. None of these factors were associated with need for mechanical ventilation (n = 6 admissions). Comparing with patients who did not receive mechanical ventilation, ventilated children had significantly higher PIM2 score (1.65 versus 0.4, p < 0.001), higher PCO2 levels (9.3 kPa versus 5.1 kPa, p = 0.01) and longer PICU stay (median 2.5 days versus 2 days, p = 0.03) The majority of patients received systemic corticosteroids, intravenous or inhaled bronchodilators. There was one pneumothorax but no death in this series.

CONCLUSIONS

LTA accounted for a small percentage of PICU admissions. Previous hospital admissions for asthma and history of non-compliance were common. Approximately one quarters required ventilatory supports. Regardless of the need for mechanical ventilation, all patients survived with prompt treatment.

Enteric-coated solid dosage forms containing sodium bicarbonate as a drug substance: an exception from the rule?

Sodium bicarbonate (sodium hydrogen carbonate) is used as an oral medication in disorders such as mild metabolic acidosis and chronic kidney disease. The two commercial products on the German market, bicaNorm and Nephrotrans, and also newly developed multiple-unit pellet formulations, have been characterized in these investigations by in-vitro methods like disintegration and dissolution testing. Both marketed products containing sodium bicarbonate are of sufficient pharmaceutical quality according to the European Pharmacopoeia. However, they and the novel pellet preparations showed different drug release at moderately elevated pH values. Early drug release may cause dose dumping in the stomach and adverse drug effects from the developed carbon dioxide. The soft capsule preparation (Nephrotrans) released the smallest amount of sodium bicarbonate at pH 1 and 4.5 of all formulations tested. It appeared that oral dosage formulations of sodium bicarbonate were an exception to the rule: the monolithic soft capsule seemed to be superior to an enteric-coated tablet as well as to multiple-unit pellet formulations from the biopharmaceutical point of view. Our results correspond with individual reports on adverse effects from patients treated with the sodium bicarbonate products.