Failure of corticosteroid therapy for experimental acid aspiration

Early death after acid aspiration results from hypoxia and hypovolemic shock. Pharmacologic doses of methylprednisolone sodium succinate (CS) are alleged to be beneficial in the early therapy of aspiration. Aspiration pneumonia was simulated in 27 mongrel dogs. Hydrochloric acid 0.1 N (pH ≤ 1) was instilled intratracheally (1.0 ml/kg). Controls (N = 7) received acid alone. Group 1 dogs (N = 10) received acid followed 5 min later by methylprednisolone sodium succinate (CS) (30 ml/kg iv). Group 2 (N = 10) received CS 20 min before aspiration. Femoral artery and pulmonary artery catheters were inserted for pressure and cardiac output monitoring and for blood sampling. Dogs received saline solution (4 ml/kg/hr iv) for the 6 hr of the experiment. Systemic and pulmonary arterial and wedge pressures were monitored and cardiac index (CI) was calculated. Intrapulmonary shunt ($\text{Q}{}_{\mathrm{<mtext>s</mtext>}}\text{Q}{}_{\mathrm{<mtext>t</mtext>}}$) was calculated with Berggren's equation. Lung water as a percentage of lung weight (%LW) was calculated for excised lungs. Baseline and 6-h values were tabulated. Depression of CI and increased $\text{Q}{}_{\mathrm{<mtext>s</mtext>}}\text{Q}{}_{\mathrm{<mtext>t</mtext>}}$ were observed in controls. Treated animals maintained CI but shunting was not improved. Increased %LW indicated pulmonary edema in all animals. Even when given before acid aspiration, CS failed to control shunting and edema.     

Evaluation of criteria for discontinuing mechanical ventilatory support.

Thirty-three patients who required short-term postoperative mechanical ventilatory support were studied to compare different criteria established to initiate weaning from mechanical ventilation. Intermittent mandatory ventilation criteria (i.e., decreasing mechanical respirator rate as long as the arterial (pHa) remains above 7.35) and conventional criteria (ie, vital capacity greater than 15 ml/kg and peak negative pressure greater than 20 cm H2O) were compared to determine which would more rapidly predict a patient's ability to sustain total spontaneous respiration. All patients were eventually weaned from mechanical ventilation and had their tracheas extubated. Twenty-one patients maintained a pHa of greater than 7.35 during total spontaneous ventilation before they would, or could, meet conventional criteria for initiating a trial of spontaneous respiration (P less than .001). Seven patients simultaneously met both criteria for maintaining total spontaneous ventilation and the remaining five patients met conventional criteria before intermittent mandatory ventilation criteria. In the latter group, the pHa decreased below 7.35 during spontaneous respiration but in only one patient did it fall below 7.30. Our findings suggest that a patient's ability to maintain a pHa of greater than 7.35 while decreasing the frequency of mechanical ventilator breaths is more accurate than peak negative pressure and vital capacity for predicting ability to sustan adequate spontaneous respiration.     

Prophylaxis and therapy of the acid aspiration syndrome

The best prevention of the aspiration syndrome begins with early identification of any patient at risk. Reduction of gastric volume and elevation of gastric pH can be achieved by premedication with glycopyrrolate (0.3 mg i.m.) and preoperative administration of H2-receptor antagonists (150 mg ranitidine p.o. 6-8 h and 80 mg i.m./i.v. 60 min before induction). Transportation of stomach contents into the duodenum can further be accelerated by 10 mg metoclopramide i.v. 20-40 min before induction. Metoclopramide will also elevate lower esophageal sphincter tone. Rapid elevation of gastric pH can be achieved by oral administration of 15-30 ml 0.3 mol sodium citrate. Induction of anesthesia should be performed as a "rapid sequence induction". Manual compression of the esophagus (Sellick manoever) may prevent gastric regurgitation. In cases of pulmonary aspiration, consequent therapy has to be initiated as soon as possible to limit broncho-alveolar damage. After endotracheal intubation the upper respiratory tract should be cleared of stomach contents by suction. Further efforts should include artificial ventilation with a high FiO2 and low PEEP (5-10 cm H2O) as well as vigorous volume substitution to maintain cardiovascular stability. Corticosteroids (200 mg Hydrocortisone i.v. may have a beneficial effect if given within 5 min after aspiration. Severe bronchospasm may respond to aminophylline (5 mg/kg i.v. as an initial bolus) or inhalation of beta-adrenergics (terbutaline 0.75-1.5 mg/inh). Bronchial lavage will rather damage than improve broncho-alveolar integrity and cannot be recommended.(ABSTRACT TRUNCATED AT 250 WORDS)     

Outcome of acid ingestion related aspiration pneumonia.

BACKGROUND: The objective of this study is to assess the incidence and long-term results of a rarely discussed medical problem -- aspiration pneumonia resulting from the intentional ingestion of acid. MATERIALS AND METHODS: The medical records of 370 patients treated at one tertiary care institution for corrosive acid injury during a 12-year period were reviewed retrospectively. The study subjects included any patients who were found to have acid ingestion related aspiration pneumonia confirmed by chest film within 24h of injury. All available data of these patients with or without aspiration pneumonia were analyzed. RESULTS: Of the 370 patients with corrosive acid injury, 15 (4.2%) had acid-aspiration pneumonia which was related to their intentional ingestion of a strong acid, hydrochloric acid (pH<1). The data for 14 patients with aspiration pneumonia and 268 without aspiration pneumonia was complete and available for analysis. Patients with aspiration pneumonia were found to be significantly older (52.2+/-6.2 to 41.7+/-0.9 years old, P=0.017), had a higher incidence of nasogastric tube irrigation (35.7-6.0%, P=0.000), had more conscious disturbance (50.0-17.5%, P=0.016), and required more endotracheal tube intubation (50.0-3.0%, P=0.000). Aspiration pneumonia was found to significantly increase the mortality rate in acid injured patients who required emergency abdominal surgery (87.5-32.0%, P=0.000) and in those who did not (28.5-5.1%, P=0.05). Two of the six survivors of aspiration pneumonia later developed laryngeal sequelae. CONCLUSIONS: Aspiration pneumonia rarely occurs as a consequence of acid ingestion. When it does occur, it greatly increases the mortality rate of those involved. For those who survive, physicians can expect some laryngotracheal sequel in long-term follow-up.     

Steriod therapy for pneumonitis induced in rabbits by aspiration of foodstuff.

The instillation of gastric contents, 0.5 ml/kg (pH 4.3), containing small food particles into the left diaphragmatic lobe of the lungs of 49 rabbits caused severe aspiration pneumonitis. Administration of methylprednisolone, 30 mg/kg, intramuscularly, every eight hours for three days to 26 of the 49 rabbits did not alter the rate of roentgenographic resolution of the pneumonitis. Corticosteroids did decrease the fibroblastic response of the lung to the aspirate, but also interfered with healing of granulomatous lesions.     

Evaluation of fine-needle aspiration cytology for renal masses

OBJECTIVE: To evaluate the accuracy and use of fine-needle aspiration (FNA) cytology for the diagnosis of renal masses because with the improved quality and increasing use of ultrasonography and computed tomography (CT), asymptomatic renal masses, particularly small (< 5 cm) tumours, are being discovered more frequently. PATIENTS AND METHODS: Between 1995 and 1997, 49 patients (mean age 67.5 years, range 42-88, 34 men and 14 women) underwent FNA of a solid or complex cystic mass under radiological guidance. All masses were further evaluated and staged by CT. Solid masses were divided according to size (< 5 cm and >/= 5 cm). Patients were followed up to the determination of a final diagnosis on tissue histology, after nephrectomy where possible. RESULTS: Thirty-six patients had histologically confirmed carcinoma at nephrectomy, and nine had presumed carcinoma (four unfit for surgery, five with advanced malignancy). The remaining four patients had benign diagnoses. FNA produced insufficient sample in eight cases (16%). The sensitivity was 89% for large (>/= 5 cm) solid masses, 64% for small (< 5 cm) solid masses and 50% for complex cysts. CONCLUSION: FNA does not contribute to the diagnosis of malignancy in large (> 5 cm) masses, as good radiological imaging is nearly always diagnostic. For smaller (< 5 cm) masses and complex cysts, FNA can occasionally confirm malignancy, but lack of diagnostic yield and low sensitivity means that FNA is unreliable as a diagnostic tool and will rarely help in the routine management of these patients.     

Evaluation of a new system for ventilatory administration of nitric oxide

A new system for delivery of nitric oxide (NO) to inspiratory gas consisting of two mass flow regulators and a soda–lime absorber for scavenging of nitrogen dioxide (NO₂) is described. The system was evaluated using three different techniques for NO analysis (infrared, chemi–luminescence and electro–chemical fuel cell technique). The electro–chemical fuel cell was less sensitive to humidity in the sample and is suitable for clinical routine use. The infrared analyser was very sensitive to humidity and the gas sample must be dried by silica gel, which absorbs NO₂ and will cause falsely low NO₂ values. NO₂ was analysed with ultra–violet methodology. NO₂ is highly toxic and the highest recommended occupational health and safety level for inhalation is 5 ppm. The highest values of NO₂ in our system were detected before the absorber in the inspiratory limb of the breathing system, being 5 ppm at 100% oxygen and 100 ppm NO using “infant” respiratory settings (3 1/min in ventilation, frequency of 30/min). The corresponding value for “adult” respiratory settings (10 1/min in ventilation, frequency of 15/min) was 3.2 ppm. The absorber reduced these levels to well below 1 ppm. When clinically relevant levels of NO were used (20 ppm), no NO₂ could be detected after the absorber, irrespective of oxygen concentration in the breathing gas. It was observed that gas cylinders with NO mixed in nitrogen may initially have a high NO₂ concentration (around 12 ppm) and should be flushed thoroughly before use.     

Omeprazole for prophylaxis of acid aspiration in elective surgery

The aim of the study was to determine whether a single oral dose of omeprazole 40 mg is effective in increasing the pH of gastric residue above 2.5 at the time of anaesthetic induction in adult patients scheduled for elective gynaecological surgery. The patients were allocated to receive either chlorazepate dipotassium 25 mg alone or omeprazole 40 mg and chlorazepate dipotassium 25 mg on the night before surgery. Gastric volume and pH were measured after induction of anaesthesia. Patients who received omeprazole had a higher mean pH than control patients (p less than 0.001). The pH was less than 3.5 in 50% of patients in the control group, but in only 4.5% of those who received omeprazole (p less than 0.01). Mean (SEM) volume of gastric fluid was 15.2 (2.7) ml in the control group and 9.2 (1.8) ml in the omeprazole group, but the results were not statistically significant. A single dose of 40 mg omeprazole significantly decreased the number of patients at risk of aspiration pneumonitis.     

Ranitidine and single-dose antacid therapy as prophylaxis against acid aspiration syndrome in obstetric practice

The efficacy of the non-particulate antacid 0.3 M sodium citrate in single and multiple dose regimes was investigated in 156 obstetric patients, both emergency and elective, who required operative delivery under general anaesthesia. Failure of either of these regimes to elevate the intragastric pH consistently to an acceptable level (greater than 3) led to investigation of a regime combining the histamine H2-receptor antagonist, ranitidine, and a single pre-anaesthetic dose of 0.3 M sodium citrate in a further 170 patients. Satisfactory pH values (greater than 3) were achieved in all patients studied. The results from the first 99 cases were analysed statistically by comparison with the multiple dose sodium citrate regime and showed a very significant improvement in the ranitidine group for intragastric pH and volume. No untoward side-effects were discovered in either mother or baby and the 6-hourly administration of ranitidine, which was easily complied with, had no effect on the progress of labour or operative delivery rate.     

Prophylaxis against acid aspiration syndrome

We have compared famotidine 40 mg, ranitidine 300 mg and placebo given in a single oral dose at 2200 hours as the sole means of prophylaxis in 286 patients who underwent elective surgery the following day. Standardised premedication was administered and anaesthesia induced. Gastric contents were aspirated by nasogastric suction and the pH and volume measured. Median values of pH after famotidine, ranitidine and placebo were 6.17, 6.74 and 2.45 respectively; median aspirate volumes were 8, 8 and 10 ml respectively. The proportions of patients considered 'not at risk' (pH greater than 2.5) were 90% after famotidine, 91% after ranitidine and 52% after placebo. We conclude that the administration of a potent H2-antagonist in a single oral dose at night offers a convenient routine means of providing extensive prophylactic cover in patients scheduled to undergo elective surgery the following day.     

Granulomatous renal mass during endovesical BCG therapy for bladder carcinoma. Diagnosis by fine-needle aspiration

One case of pseudotumoral granulomatous renal mass during endovesical bacillus Calmette-Guérin (BCG) therapy for superficial bladder neoplasm is reported. Such an adverse effect is exceptional and is clearly related to a vesicorenal reflux in our patient. In this case ultrasound-guided fine-needle aspiration was able to settle the diagnosis and avoid surgery. The patient responded to triple antituberculous therapy.