Water Accumulation in Amsorb Canister May Cause Inspiratory Flow Obstruction: A Case Report.

A patient received closed-circuit anesthesia from a General Electric Avance S/5 (GE Healthcare, Madison, WI) anesthesia machine during a robotic abdominal procedure. With return of spontaneous ventilation at the end of the procedure, the negative airway pressure alarm began to sound, and a negative airway pressure of 10-15 cm H2O was observed with each breath. Replacing the CO2 absorber resolved the problem. There was considerable condensation on the walls of the Amsorb canister, and on disassembly, the sponge at the bottom was wet. Experimentation with an empty canister revealed that as little as 30 mL of water in the sponge can reproduce our observations.

Quantification of Postmembrane Gaseous Microembolization During Venoarterial Extracorporeal Membrane Oxygenation.

Prolonged use of venoarterial extracorporeal membrane oxygenation (VA ECMO) may be complicated by end-organ dysfunction. Although gaseous microemboli (GME) are thought to damage end organs during cardiopulmonary bypass, patient exposures to GME have not been well characterized during VA ECMO. We therefore performed an observational study of GME in adult VA ECMO patients, with correlation to clinical events during routine patient care. After institutional review board (IRB) approval, we used two Doppler probes to detect GME noninvasively in extracorporeal membrane oxygenation (ECMO) circuits on four patients for 15 hours total while also recording patient care events. We then conducted in vitro trials to compare Doppler signals with gold-standard measurements using an Emboli Detection and Classification EDAC quantifier (Luna Innnovations, Inc. Roanoke, VA) (Terumo Cardiovascular, Ann Arbor, MI) during simulated clinical interventions. Correlations between Doppler and EDAC data were used to estimate GME counts and volumes represented by clinical Doppler data. A total of 503 groups of Doppler peaks representing GME showers were observed, including 194 statistically larger showers during patient care activities containing 92% of total Doppler peaks. Intravenous injections accounted for an estimated 68% of GME and 88% of GME volume, whereas care involving movement accounted for an estimated 6% of GME and 3% of volume. Overall estimated embolic rates of 24,000 GME totaling 4 µl/hr rivals reported GME rates during cardiopulmonary bypass. Numerous GME are present in the postmembrane circuit during VA ECMO, raising concern for effects on microcirculation and organ dysfunction. Strategies to detect and minimize GME may be warranted to limit embolic exposures experienced by VA ECMO patients.

Needleless connectors substantially reduce flow of crystalloid and red blood cells during rapid infusion.

Although needleless connectors (NC) are frequently used in the perioperative setting, the potential of modern NCs to slow delivery of IV fluids has not been thoroughly studied. We examined flow characteristics of 5 NC models during pressurized delivery of crystalloid and banked red blood cells from a Level 1 warmer through various IV catheters. Crystalloid flow rates were reduced by 29% to 85% from control in catheters >18 gauge, while red blood cell flow reductions ranged from 22% to 76% in these catheters (all P < 0.0050). We suggest that practitioners consider eliminating NCs when large IV catheters are inserted for rapid fluid administration.

Elimination of gaseous microemboli from cardiopulmonary bypass using hypobaric oxygenation.

BACKGROUND: Numerous gaseous microemboli (GME) are delivered into the arterial circulation during cardiopulmonary bypass (CPB). These emboli damage end organs through multiple mechanisms that are thought to contribute to neurocognitive deficits after cardiac surgery. Here, we use hypobaric oxygenation to reduce dissolved gases in blood and greatly reduce GME delivery during CPB. METHODS: Variable subatmospheric pressures were applied to 100% oxygen sweep gas in standard hollow fiber microporous membrane oxygenators to oxygenate and denitrogenate blood. GME were quantified using ultrasound while air embolism from the surgical field was simulated experimentally. We assessed end-organ tissues in swine postoperatively using light microscopy. RESULTS: Variable sweep gas pressures allowed reliable oxygenation independent of carbon dioxide removal while denitrogenating arterial blood. Hypobaric oxygenation produced dose-dependent reductions of Doppler signals produced by bolus and continuous GME loads in vitro. Swine were maintained using hypobaric oxygenation for 4 hours on CPB with no apparent adverse events. Compared with current practice standards of oxygen/air sweep gas, hypobaric oxygenation reduced GME volumes exiting the oxygenator (by 80%), exiting the arterial filter (95%), and arriving at the aortic cannula (∼100%), indicating progressive reabsorption of emboli throughout the CPB circuit in vivo. Analysis of brain tissue suggested decreased microvascular injury under hypobaric conditions. CONCLUSIONS: Hypobaric oxygenation is an effective, low-cost, common sense approach that capitalizes on the simple physical makeup of GME to achieve their near-total elimination during CPB. This technique holds great potential for limiting end-organ damage and improving outcomes in a variety of patients undergoing extracorporeal circulation.

Ultrasound-guided sciatic neuroma block for treatment of intractable stump pain.

A 61-year-old patient with severe stump pain required hospitalization and intravenous opioids for pain control. After evaluation by our anesthesia pain management service, we concluded that the patient had a neuroma at the site of sciatic nerve transection and that injection of a mixture of local anesthetic and corticosteroid at the site of the neuroma was the most appropriate management. Because the alternative methods of nerve localization (eg, motor stimulation, paresthesia) were unlikely to be successful, we felt that the most reliable way to accomplish this task was to use live ultrasound guidance. After a series of 4 ultrasound-guided blocks with bupivacaine and methylprednisolone acetate, the patient's pain was alleviated to the point at which it was managed with occasional doses of oral opioids.

Aromatherapy with peppermint, isopropyl alcohol, or placebo is equally effective in relieving postoperative nausea.

To determine whether aromatherapy can reduce postoperative nausea, the investigators studied 33 ambulatory surgery patients who complained of nausea in the PACU. After indicating the severity of nausea on a 100-mm visual analogue scale (VAS), subjects received randomized aromatherapy with isopropyl alcohol, oil of peppermint, or saline (placebo). The vapors were inhaled deeply through the nose from scented gauze pads held directly beneath the patients' nostrils and exhaled slowly through the mouth. Two and 5 minutes later, the subjects rated their nausea on the VAS. Overall nausea scores decreased from 60.6 +/- 4.3 mm (mean +/- SE) before aromatherapy to 43.1 +/- 4.9 mm 2 minutes after aromatherapy (P <.005), and to 28.0 +/- 4.6 mm 5 minutes after aromatherapy (P < 10(-6)). Nausea scores did not differ between the treatments at any time. Only 52% of the patients required conventional intravenous (IV) antiemetic therapy during their PACU stay. Overall satisfaction with postoperative nausea management was 86.9 +/- 4.1 mm and was independent of the treatment group. Aromatherapy effectively reduced the perceived severity of postoperative nausea. The fact that a saline "placebo" was as effective as alcohol or peppermint suggests that the beneficial effect may be related more to controlled breathing patterns than to the actual aroma inhaled.

Differences in systemic opioid use do not explain increased fever incidence in parturients receiving epidural analgesia.

BACKGROUND: It has been hypothesized that an increased incidence of fever in patients receiving epidural analgesia might result not from epidural per se, but rather from the antipyretic effect of opioids preferentially administered to women in the no-epidural group. If this were the case, then one would expect the incidence of fever in parturients who did not receive systemic opioids to be independent of whether they received epidural analgesia. METHODS: Using a cohort study design, the authors evaluated the records of 1,233 nulliparous patients whose labor analgesia was managed with (1) no medication (N = 170); (2) 10 mg intravenous systemic nalbuphine plus 10 mg intramuscular every 3 to 4 h as required (N = 327); (3) epidural analgesia with continuous infusion of 0.125% bupivacaine with 2 microg/ml fentanyl (N = 278); or (4) patients who received both systemic nalbuphine and epidural analgesia (N = 458). Fever was diagnosed if the maximum temperature during labor exceeded 100.4 degrees F (38 degrees C). RESULTS: The incidence of fever did not differ according to nalbuphine administration for women not receiving epidural analgesia (1% no nalbuphine, 0.3% with nalbuphine, P = 0.27) or for women receiving epidural analgesia (17% no nalbuphine, 17% with nalbuphine, P = 1.0). However, the incidence of fever differed significantly between patients who received no analgesia as compared to those who received epidural analgesia alone (1% vs. 17%, P = 10(-6)). Controlling for confounding did not alter these associations. CONCLUSIONS: Our findings suggest that an antipyretic effect of nalbuphine in patients who do not receive an epidural does not explain the greater incidence of fever observed in women who receive epidural analgesia for labor.