Severe Hypoxemia Prevents Spontaneous and Naloxone-induced Breathing Recovery after Fentanyl Overdose in Awake and Sedated Rats.

BACKGROUND: As severe acute hypoxemia produces a rapid inhibition of the respiratory neuronal activity through a nonopioid mechanism, we have investigated in adult rats the effects of hypoxemia after fentanyl overdose-induced apnea on (1) autoresuscitation and (2) the antidotal effects of naloxone. METHODS: In nonsedated rats, the breath-by-breath ventilatory and pulmonary gas exchange response to fentanyl overdose (300 µg · kg · min iv in 1 min) was determined in an open flow plethysmograph. The effects of inhaling air (nine rats) or a hypoxic mixture (fractional inspired oxygen tension between 7.3 and 11.3%, eight rats) on the ability to recover a spontaneous breathing rhythm and on the effects of naloxone (2 mg · kg) were investigated. In addition, arterial blood gases, arterial blood pressure, ventilation, and pulmonary gas exchange were determined in spontaneously breathing tracheostomized urethane-anesthetized rats in response to (1) fentanyl-induced hypoventilation (7 rats), (2) fentanyl-induced apnea (10 rats) in air and hyperoxia, and (3) isolated anoxic exposure (4 rats). Data are expressed as median and range. RESULTS: In air-breathing nonsedated rats, fentanyl produced an apnea within 14 s (12 to 29 s). A spontaneous rhythmic activity always resumed after 85.4 s (33 to 141 s) consisting of a persistent low tidal volume and slow frequency rhythmic activity that rescued all animals. Naloxone, 10 min later, immediately restored the baseline level of ventilation. At fractional inspired oxygen tension less than 10%, fentanyl-induced apnea was irreversible despite a transient gasping pattern; the administration of naloxone had no effects. In sedated rats, when PaO2 reached 16 mmHg during fentanyl-induced apnea, no spontaneous recovery of breathing occurred and naloxone had no rescuing effect, despite circulation being maintained. CONCLUSIONS: Hypoxia-induced ventilatory depression during fentanyl induced apnea (1) opposes the spontaneous emergence of a respiratory rhythm, which would have rescued the animals otherwise, and (2) prevents the effects of high dose naloxone.

Type of Prior Operation Does Not Predict Surgical Intervention for Small Bowel Obstruction.

Background: Patients with prior abdominal surgeries are at higher risk for intra-abdominal adhesive tissue formation and subsequently higher risk for small bowel obstruction (SBO).Purpose: In this study, we investigated whether surgical intervention for SBO was more likely following specific types of abdominal surgeries.Research Design: With retrospective chart review, we pooled data from 799 patients, ages 18 to 89, admitted with SBO between 2012 and 2019. Patients were evaluated based on whether they underwent surgery or were managed conservatively. They were further compared with regard to past surgical history by way of type of abdominal surgery (or surgeries) undergone prior to admission.Results: Of the 799 patients admitted for SBO, 206 underwent surgical intervention while 593 were managed nonoperatively. There was no significant difference in number of prior surgeries (2.07 ± 1.56 vs 2.36 ± 2.11, P = .07) or in number of comorbidities (2.39 ± 1.97 vs 2.65 ± 1.93, P = .09) for surgical vs non-surgical intervention. Additionally, of the operations evaluated, no specific type of abdominal surgery predicted need for surgical intervention in the setting of SBO. However, for both surgical and non-surgical intervention following SBO, pelvic surgery was the most common type of prior abdominal surgery (45% vs 43%). There are significantly more female pelvic surgeries in both the operative (91.4% vs 8.6%, P < .0001) and nonoperative groups (89.9% vs 10.2%, P < .0001).Conclusion: Ultimately, no specific type of prior operation predicted the need for surgical intervention in the setting of SBO.

Indications for Readmission for Small Bowel Obstruction: A Comparison of Medical vs Surgical Service Admission.

Small bowel obstruction (SBO) impacts the health care system and patient quality of life. Previously, we evaluated differences between medical and surgical admissions in the management of SBO. This study investigates indications for readmission based on original admission to medical (MS) or surgical services (SS). A retrospective chart review was performed for 799 patients aged 18 to 89 admitted between 2012 and 2019 with a diagnosis of SBO. Patient characteristics examined included length of stay (LOS), prior abdominal operations, prior SBO, use of small bowel follow through imaging, operative intervention, mortality, and 30-day readmission. There was no difference in readmission rates in patients originally admitted to MS or SS (13.2% vs 12.7%, P = .86). Patients admitted to SS were more likely to be readmitted for recurrent SBO (39% vs 8.6%, P = .006). Patients admitted to MS were more likely to be readmitted for other reasons (73.9% v. 40.2%, P = .004). In the MS cohort, 30.4% (7 patients) had surgery during their initial admission for SBO, and none of those patients were readmitted for recurrent SBO (rSBO). In the SS cohort, 23% had surgery during their initial admission and 31.6% were readmitted for rSBO (P = .002). Patients admitted to SS were more likely to be readmitted for rSBO and to require surgery. Patients admitted to MS were more likely to be readmitted for other reasons. None of the MS patients who had surgery were readmitted for SBO. 31.6% of SS patients who had surgery were readmitted for SBO.

Outcomes of Small Bowel Obstructions by Admitting Specialty and Hospital Type.

BACKGROUND: Small bowel obstructions (SBOs) account for a significant burden on the health care system. Should the ongoing trend of regionalizing medicine extend to these patients? We investigated if there is a benefit to admitting SBOs to larger teaching hospitals and to surgical services. METHODS: We performed a retrospective chart review of 505 patients admitted to a Sentara Facility between 2012 and 2019 with a diagnosis of SBO. Patients between the ages of 18 and 89 were included. Patients were excluded if they required emergent operation. Outcomes were evaluated based on patient's admission either to a teaching or community hospital as well as the admitting service's specialty. RESULTS: Of 505 patients admitted with a SBO, 351 (69.5%) were admitted to a teaching hospital. 392 (77.6%) patients were admitted to a surgical service. The average length of stay (LOS) (4 vs 7 days, P < .0001) and cost ($18,069.79 vs $26,458.20, P < .0001) were lower at teaching hospitals. The same trends in LOS (4 vs 7 days, P < .0001) and cost ($18,265.10 vs $29 944.82, P < .0001) were seen with surgical services. The 30-day readmission rate was higher in teaching hospitals (18.2% vs 11%, P = .0429), and no difference was seen in operative rate or mortality. DISCUSSION: These data would suggest that there is a benefit to admitting SBO patients to larger teaching hospitals and to surgical services with regard to LOS and cost, suggesting that these patients might benefit from treatment at centers with emergency general surgery (EGS) Services.

Diatrizoate (Gastrograffin®) Small Bowel Follow Through for Small Bowel Obstructions: Timing and Outcomes.

INTRODUCTION: The advent of the Gastrograffin® small bowel follow through (G-SBFT) has resulted in a decreased rate of operative intervention of small bowel obstructions (SBO); however, there is no data to suggest when G-SBFT should be performed. METHODS: We retrospectively reviewed 548 patients, admitted to 1 of 9 hospitals with a diagnosis of SBO. Patients were divided into two categories with regards to timing of G-SBFT: before (early) or after (late) 48 hours from admission. Primary outcomes were length of stay (LOS) and total cost. Secondary outcomes were operative interventions and mortality. RESULTS: Of the reviewed patients, 71% had the G-SBFT ordered early. Comparing early versus late, there were no differences in patient characteristics with regards to age, sex, or BMI. There was a significant difference between LOS (4 vs 8 days, P < 0.05) and total cost ($17,056.19 vs $33,292.00, P < 0.05). There was no difference in mortality (1.3% vs 2.6%, P = 0.239) or 30-day readmission rates (15.6% vs 15.9%, P = 0.509). Patients in the early group underwent fewer operations (20.7% vs 31.9%, P = 0.05). DISCUSSION: Patients that had a G-SBFT ordered early had a decreased LOS, total cost, and operative intervention. This suggests there is a benefit to ordering G-SBFT earlier in the hospital stay to reduce the overall disease burden, and that it is safe to do so with regards to mortality and readmissions. We therefore recommend ordering a G-SBFT within 48 hours to reduce LOS, cost, and need for an operation.

Evidence for the emergence of an opioid-resistant respiratory rhythm following fentanyl overdose.

Breathing resumes within one to two minutes following fentanyl overdose induced apnea in spontaneously breathing rats. As this regular rhythm is produced at a time wherein fentanyl concentrations and receptor occupancy are likely to be extremely high, the mechanisms initiating and sustaining such a respiratory activity remain unclear. Forty-four un-anesthetized adult rats were studied in an open-flow plethysmograph. Regardless of the dose of fentanyl that was used, i.e. 50 µg.kg-1 (n = 8), 100 µg.kg-1 (n = 8) or 300 µg.kg-1 (n = 7), all rats developed an immediate central apnea followed by a depressed regular rhythm that was produced 118, 97 and 81 s (median) later, respectively. Only one rat did not recover. This inspiratory and regular activity consisted of a low frequency and tidal volume pattern with a significant reduction in V̇E/V̇CO2 ratio, which persisted for at least 30 min and that was not different between 100 or 300 µg.kg-1. The time at which this respiratory rhythm emerged, following the highest dose of fentanyl, was not affected by 100 % O2 or 8% CO2/15 % O2. The absolute level of ventilation was however higher in hypercapnic and moderately hypoxic conditions than in hyperoxia. When a second injection of the highest dose of fentanyl (300 µg.kg-1) was performed at 10 min, ventilation was not significantly affected and no apnea was produced in major contrast to the first injection. When a similar injection was performed 30 min after the first injection, in a separate group of rats, an apnea and breathing depression was produced in 30 % of the animals, while in the other rats, ventilation was unaffected. We conclude that the depressed regular respiratory activity emerging during and following fentanyl overdose is uniquely resistant to fentanyl.