William C. Culp Jr. M.D.

Culp, W.C., Jr. and Muse, K.W. (2021). “Preventing Operating Room Fires: Impact of Surgical Drapes on Oxygen Contamination of the Operative Field.” J Patient Saf 17(8): e1846-e1850.

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OBJECTIVE: The aim of the study was to measure underdrape oxygen pooling, surgical site oxygen contamination, and time to restoration of 21% oxygen concentration after cessation of oxygen delivery by measuring oxygen concentration under simulated clinical conditions with various drapes. METHODS: In a 2-part study, oxygen permeability of four differing surgical drapes was measured (Part A) and a mannequin was used to measure underdrape oxygen pooling and surgical site oxygen contamination (Part B). In Part A, a container of high concentration oxygen was sealed with a surgical drape. Oxygen concentrations on both sides of the drape were then measured over time to quantify drape oxygen permeability. Part B included a mannequin model draped for a hypothetical surgical site with oxygen administered by face mask. Oxygen concentration was measured at both the surgical site and under the drape nearest the surgical site. RESULTS: Oxygen permeability varied significantly between drapes tested. The surgical site oxygen concentration ranged from 20% to 58% (P = 0.0001). The commonly used woven 100% cotton operating room (OR) towel was highly permeable. The plastic occlusive drape created an impermeable barrier, which did not allow for any oxygen contamination but created the longest time to return to 21% oxygen concentration at the underdrape site after cessation of oxygen delivery. CONCLUSIONS: Surgical drapes have varying oxygen permeability and can lead to high concentration underdrape oxygen pooling. Oxygen contamination of the surgical site varies widely based on drape material and may reach dangerously high levels, especially with the cotton OR towel. Surgical drape selection may impact OR fire risk.

Pham, V., Nguyen, L., Hedin, R.J., Shaver, C., Hammonds, K.A.P. and Culp, W.C., Jr. (2021). “COVID-19: Anesthesia Machine Circuit Pressure During Use As An Improvised ICU Ventilator.” Anesth Analg Jan 12. [Epub ahead of print].

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BACKGROUND: Use of anesthesia machines as improvised ICU ventilators may occur in locations where waste anesthesia gas suction(WAGS) is unavailable. Anecdotal reports suggest as much as 18 cmH2O positive end-expiratory pressure(PEEP) being inadvertently applied under these circumstances, accompanied by inaccurate pressure readings by the anesthesia machine. We hypothesized that resistance within closed anesthetic gas scavenging systems(AGSS) disconnected from WAGS may inadvertently increase circuit pressures. METHODS: An anesthesia machine was connected to an anesthesia breathing circuit, a reference manometer, and a standard bag reservoir to simulate a lung. Ventilation was initiated as follows: Volume Control, TV 500 mL, respiratory rate 12, I:E 1:1.9, FiO2 1.0, fresh gas flow(FGF) rate 2.0 liters per minute(LPM), and PEEP 0 cmH2O. After engaging the ventilator, PEEP and peak inspiratory pressure(PIP) were measured by the reference manometer and the anesthesia machine display simultaneously. The process was repeated using prescribed PEEP levels of 5, 10, 15, and 20 cmH2O. Measurements were repeated with the WAGS disconnected and then were performed again at FGF of 4, 6, 8, 10, and 15 LPM. This process was completed on three anesthesia machines: Dräger Perseus A500, Dräger Apollo, and the GE Avance CS2. Simple linear regression was used to assess differences. RESULTS: Utilizing non-parametric Bland-Altman analysis, the reference and machine manometer measurements of PIP demonstrated median differences of -0.40 cmH2O (95%LOA: -1.00,0.55) for the Dräger Apollo, -0.40 cmH2O (95%LOA: -1.10, 0.41) for the Dräger Perseus, and 1.70 cmH2O (95%LOA: 0.80,3.00) for the GE Avance CS2. At FGF 2 LPM and PEEP 0 cmH2O with the WAGS disconnected, the Dräger Apollo had a difference in PEEP of 0.02 cmH2O (95%CI: -0.04,0.08; p=0.53); the Dräger Perseus A500, <0.0001 cmH2O (95%CI: -0.11 0.11; p=1.00); and the GE Avance CS2, 8.62 cmH2O (95%CI: 8.55,8.69; p<0.0001). After removing the hose connected to the AGSS and the visual indicator bag on the GE Avance CS2, the PEEP difference was 0.12 cmH2O (95%CI: 0.059,0.181; p=0.0002). CONCLUSIONS: Displayed airway pressure measurements are clinically accurate in the setting of disconnected WAGS. The Dräger Perseus A500 and Apollo with open scavenging systems do not deliver inadvertent CPAP with WAGS disconnected, but the GE Avance CS2 with a closed AGSS does. This increase in airway pressure can be mitigated by the manufacturer's recommended alterations. Anesthesiologists should be aware of the potential clinically important increases in pressure that may be inadvertently delivered on some anesthesia machines, should the WAGS not be properly connected.

Curley, J. M., D. P. Ciceri and W. C. Culp, Jr. (2020). “Sugammadex Administration to Facilitate Timely Neurologic Examination in the Traumatic Brain Injury Patient.” Neurocrit Care 32(3): 880-882.

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Neuromuscular blocking agents are frequently administered to traumatic brain injury patients during initial airway management; however, paralytics can delay diagnosis and treatment by impeding the neurologic examination. Sugammadex is a relatively new medication approved for reversal of amino-steroid paralytic agents such as rocuronium or vecuronium. We describe the use of sugammadex to reverse prolonged rocuronium-induced paralysis in a dialysis-dependent patient who suffered a traumatic brain injury. This reversal allowed for immediate evaluation by a neurosurgeon, neurosurgical intervention, and subsequent detection of patient neurologic deterioration by examination which otherwise may have been mistaken for prolonged paralysis. To the authors’ knowledge, the use of sugammadex for this purpose has not previously been reported. [No abstract; excerpt from article].