Differential effect of glucocorticoids on pulmonary responses and eosinophils

Respiratory complications in the pediatric postanesthesia care unit

This article focuses on common respiratory complications in the postanesthesia care unit (PACU). Approximately 1 in 10 children present with respiratory complications in the PACU. The article highlights risk factors and at-risk populations. The physiologic and pathophysiologic background and causes for respiratory complications in the PACU are explained and suggestions given for an optimization of the anesthesia management in the perioperative period. Furthermore, the recognition, prevention, and treatment of these complications in the PACU are discussed.

Postoperative pulmonary complications

PURPOSE OF REVIEW

Postoperative pulmonary complications, including pneumonia, bronchospasm, respiratory failure and prolonged mechanical ventilation, occur commonly and are a significant source of morbidity and mortality. This review will discuss the etiology of postoperative pulmonary complications and the interventions that reduce their risk.

RECENT FINDINGS

General anesthesia and surgery produce changes in the respiratory system and are responsible, along with underlying conditions, for postoperative pulmonary complications. Risk factors include upper abdominal or thoracic surgery, cigarette smoking, chronic respiratory disease, emergency surgery, anesthetic time of 180 min or more, age greater than 70 years, renal failure, poor nutritional status, and significant intraoperative blood loss. The inhibition of phrenic nerve output results in postoperative diaphragmatic dysfunction. Sleep-disordered breathing occurs after surgery even in patients without obstructive sleep apnea, but patients with obstructive sleep apnea may have a worsening of their disease after surgery. A clear advantage of one anesthetic technique over another in reducing postoperative pulmonary complications has not been demonstrated. Conflicting results have been obtained regarding the value of epidural analgesia in preventing postoperative pulmonary complications. Incentive spirometry decreases rates of postoperative pulmonary complications and hospital lengths of stay.

SUMMARY

Understanding risk factors for the development of postoperative pulmonary complications allows targeted interventions aimed at reducing their frequency and severity. Further research is needed to define the role of regional analgesic and anesthetic techniques in reducing postoperative pulmonary complications, and also to define the nature of risk factors and develop better predictive models of patients at risk of developing postoperative pulmonary complications.

Preoperative assessment: pulmonary

Understanding the risk factors for the development of PPCs allows targeted interventions aimed at reducing the frequency and severity of PPCs. The broad categories of what increases the likelihood of developing a PPC are understood but specific understanding of how individual risk factors act to cause PPCs is lacking,and there is little information regarding the interaction or synergy between risk factors. Further research is needed to define the nature of risk factors and develop better predictive models of patients at risk for developing PPCs. It is clear that anesthetic agents produce significant changes in the respiratory system but further information is needed to define how such changes contribute, if at all, to the subsequent development of PPCs. The ongoing controversy regarding the value of regional analgesia or anesthetic techniques, especially epidural analgesia and anesthesia, in reducing or preventing PPCs requires well-done randomized clinical trials. Further research is also needed in the area of postoperative care such as interventions in patients with OSA or the use of inventive spirometric techniques.

Unguided bronchoalveolar lavage techniques and residual effects in dogs

OBJECTIVES

To investigate the use of unguided bronchoalveolar lavage techniques in dogs without fibreoptic bronchoscopy, using an adapted single vascular catheter and a double-lumen catheter made from two single vascular catheters.

ANIMALS

Sixty-nine dogs were examined with the single-catheter technique and 110 dogs with the double-catheter technique.

DESIGN

A prospective study.

PROCEDURE

Sixty-nine and 220 samples, collected with the single catheter and the double catheter respectively, were examined cytologically. Lungs of 69 dogs were examined grossly and histologically. Radiographic examination was performed on 11 dogs.

RESULTS

The double-catheter technique produced samples with significantly higher cellularity (P < 0.01) and fewer red blood cells (P < 0.01) than the single-catheter technique. Repeat samples collected with a double catheter were not significantly different (P > 0.01) in any value. A reference range for nucleated cell counts of 62 to 1210 x 10(6)/L was calculated from 57 clinically and histologically normal dogs. The major residual effects of the technique were localised pulmonary oedema, and alveolar distension with collapse and congestion of distant parenchyma. Thoracic radiographs revealed increased lung opacity for at least up to 7 h after the procedure.

CONCLUSIONS

The cellularity of the bronchoalveolar lavage fluid obtained was adequate and sufficient fluid was retrieved when the single catheter was located in a proper position. However, the double catheter obtained better samples more quickly and easily, with less damage to the respiratory tract.

Corticosteroid withdrawal restores responses to calcium chelators and enhances cholinergic responsiveness

To investigate the importance of the inflammatory response in acute peripheral airway constriction, we measured peripheral airway responses to calcium chelators and acetylcholine in anesthetized Basenji-Greyhound (BG) dogs before, during, and after chronic corticosteroid treatment. A wedged bronchoscope technique was used to measure peripheral airway resistance before and after aerosol challenge with 4% Na2EDTA or acetylcholine (10 micrograms/ml) in contralateral lungs. After the initial measurements, five BG dogs received long-term treatment with methylprednisolone (2 mg/kg/d, subcutaneously), and five dogs were not treated and served as controls. Four weeks of methylprednisolone treatment almost totally abolished responses to Na2EDTA, but responses to acetylcholine did not change significantly. After discontinuing corticosteroid therapy, responses to Na2EDTA returned to levels found before corticosteroid treatment; responses to acetylcholine were significantly enhanced. We conclude that chronic corticosteroid treatment reduces acute response to calcium chelators and that withdrawal of corticosteroid therapy is associated with enhanced cholinergic responsiveness.