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The article discusses the clinical implications of morbid obesity (MO) in bariatric medicine. It suggests that the anesthetic management of the MO patient requires careful preoperative evaluation to ensure that preexisting disease processes are accounted for in the anesthetic management plan. The article reveals that the common perception that all MO patients are "full stomach" may be in error, and that new approaches to preoxygenation may lessen the likelihood of desaturation during apnea.

Background: Effective O2 delivery and accurate end-tidal CO2 (ETCO2) sampling are essential features of nasal cannulae (NCs) in patients with compromised respiratory status. We studied 4 NC designs: bifurcated nasal prongs (NPs) with O2 delivery and CO2 sensing in both NPs (Hudson), separate O2/CO2 NPs (Salter), and CO2 sensing in NPs with cloud O2 delivery outside the NPs via multi vents (Oridion) and dual vents (Medline). We hypothesized that design differences between NCs would influence O2 delivery and ETCO2 detection., Methods: Forty-five healthy volunteers, 18 to 35 years, participated in an unrestricted, randomized block design, each subject serving as their own control in a 4-period crossover study design of 4 NCs during one session. Monitoring included electrocardiogram, posterior pharynx O2 sampling from a Hauge Airway (Sharn Anesthesia Products, Tampa, FL), and NC ETCO2. In 11 volunteers, radial artery blood was sampled from a catheter for partial pressures of O2 and carbon dioxide (PaO2 and PaCO2) determination. Per randomization, each NC was positioned, and data were collected over 2 minutes (ETCO2, pharyngeal O2, PaO2, and PaCO2) during room air and during O2 fresh gas flows (FGFs) of 2, 4, and 6 Lpm. Statistical analyses were performed with SAS Analytics Pro, Version 9.3, and JMP Statistical Software, Version 11 (SAS Institute Inc., Cary, NC), significance at P < 0.05., Results: Blood gas analyses indicated PaCO2 during steady state at each experimental time period remained unchanged from physiologic baseline. PaO2 did not differ between NC devices at baseline or 2 Lpm O2. The PaO2 at 4 Lpm from the separate NPs and bifurcated NCs was significantly higher than the multi-vented NC. Pharyngeal O2 with the NC with separate NPs was significantly higher than multivented and dual-vented cloud delivery NCs at 2, 4, and 6 Lpm FGF. Pharyngeal O2 with the NC with bifurcated NPs was significantly higher than the multi-vented NC at 2 Lpm, and higher than cloud delivery NCs at 4 and 6 Lpm FGF. ETCO2 was significantly lower with the NC with bifurcated NPs compared to the other 3 NCs, consistent with errant CO2 tracings at higher FGF., Conclusions: NCs provide supplemental inspired O2 concentrations for patients with impaired pulmonary function. Accurate measures of ETCO2 are helpful in assessing respiratory rate and determining whether CO2 retention is occurring from hypoventilation. These findings suggest the NC with separate NPs was the most effective in delivering O2 and the most consistent at providing reliable CO2 waveforms at higher FGFs.

The Accreditation Council for Graduate Medical Education is transitioning to a competency-based system with milestones to measure progress and define success of residents. The confines of the time-based residency will be relaxed. Curriculum must be redesigned and assessments will need to be precise and in-depth. Core anesthesiology faculty will be identified and will be the "trained observers" of the residents' progress. There will be logistic challenges requiring creative management by program directors. There may be residents who achieve "expert" status earlier than the required 36 months of clinical anesthesia education, whereas others may struggle to achieve acceptable status and will require additional education time. Faculty must accept both extremes without judgment. Innovative new educational opportunities will need to be created for fast learners. Finally, it will be important that residents embrace this change. This will require programs to clearly define the specific aims and measurement endpoints for advancement and success.

Background: Practitioners often presuppose that obesity will increase neuraxial technique difficulty in pregnant patients, but few investigators have systematically examined this population for risk factors associated with difficult epidural or spinal needle placement. We designed this study to prospectively identify factors that predict neuraxial technique difficulty in pregnant patients., Methods: Using a prospective, observational format, pregnant patients were examined for multiple potential risk factors for neuraxial technique difficulty, including current body mass index, ability to palpate spinous processes, maximum back flexion, scoliosis, and experience of the practitioner. Neuraxial technique difficulty was then assessed using two measures: 1) the number of needle passes needed to reach the desired space, and 2) the placement time from skin infiltration to either spinal injection or epidural catheter threading. Predictors of total needle passes were determined by fitting the data to a generalized linear model with negative binomial error. Predictors of neuraxial anesthetic time were determined by fitting a linear model to the log of neuraxial anesthetic placement time. A survival model was used to account for bias introduced when attending physicians intervened in resident physician procedures., Results: Neuraxial procedures in 427 pregnant patients were studied. For both the number of needle passes and the neuraxial anesthetic placement time, the significant predictors of difficulty were the practitioner's ability to palpate the patient's bony landmarks and the patient's ability to flex her back. Obesity, as measured by body mass index, was not an independent predictor of either end point. Obesity did, however, strongly predict both the ability to palpate landmarks and flex the back., Conclusions: Despite concerns that obesity may cause difficulty with neuraxial technique, some obese patients have surprisingly easy neuraxial block placements. When approaching any neuraxial anesthetic in a pregnant patient, and especially in the obese parturient, back flexion and landmark palpation predict neuraxial technique difficulty.

Sufentanil is a potent opioid that occasionally has been associated with hypotension. The mechanism behind this hypotension is unclear. We hypothesized that sufentanil had a direct effect on vascular smooth muscle to cause vasodilation. Sufentanil was infused into the brachial artery of 10 young, healthy volunteers at rates of 0.083, 0.167, 0.333, and 0.833 microg/min. Forearm blood flow was measured in both the experimental and control arms with venous occlusion plethysmography. The forearm blood flow in the infused arm increased in a dose-dependent fashion from 3.2 to 5.2 mL/min per 100 mL of tissue whereas simultaneous measurements in the control (non-infused) arm did not increase. Heart rate and mean arterial blood pressure were unchanged during the infusions. Furthermore, respiratory rate did not change at any infusion level and sedation did not occur. Thus, the data support that significant systemic "spillover" of sufentanil did not occur. We conclude that sufentanil has a direct, vasodilatory effect on human vascular tissue that is likely independent of a neurogenic or systemic mechanism.

Unlabelled: Thirty-four patients scheduled for elective inpatient surgery were randomized equally to receive either dexmedetomidine (initial loading dose of 1- microg/kg over 10 min followed by 0.4 microg. kg(-1). h(-1) for 4 h) or morphine sulfate (0.08 mg/kg) 30 min before the end of surgery. We determined heart rate (HR), mean arterial blood pressure (MAP), respiratory rate (RR), sedation and analgesia (visual analog scale), and use of additional morphine in the postanesthesia care unit (PACU) and up to 24 h after surgery. Groups were similar for patient demographics, ASA physical status, surgical procedure, baseline hemodynamics, and intraoperative use of drugs and fluids. Dexmedetomidine-treated patients had slower HR in the PACU (by an average of 16 bpm), whereas MAP, RR, and level of sedation were similar between groups. During Phase I recovery, dexmedetomidine-treated patients required significantly less morphine to achieve equivalent analgesia (PACU dexmedetomidine group, 4.5 +/- 6.8 mg; morphine group, 9.2 +/- 5.2 mg). Sixty minutes into recovery only 6 of 17 dexmedetomidine patients required morphine in contrast to 15 of 17 in the morphine group. The administration of dexmedetomidine before the completion of major inpatient surgical procedures significantly reduced, by 66%, the early postoperative need for morphine and was associated with a slower HR in the PACU., Implications: The use of dexmedetomidine for postoperative analgesia resulted in significantly less additional pain medication (morphine) and slower heart rates than a control group receiving only morphine. These outcomes may prove advantageous for patients who might be placed at higher risk by tachycardia or large doses of morphine.

Unlabelled: We explored the possible mechanisms of hypotension during the administration of sedation-analgesia doses of remifentanil in young (ASA physical status I) volunteers (n = 24). Cardiorespiratory and sympathetic variables were collected at baseline and at plasma concentrations of remifentanil (2 and 4 ng/mL). Monitoring included electrocardiogram, heart rate (HR), direct blood pressure, muscle sympathetic nerve activity, and forearm blood flow (FBF). A cold pressor test (1-min hand immersion in ice water) quantified analgesia effectiveness (visual analog scale, 0-100). Visual analog scale to the cold pressor test (62 at baseline) decreased to 27 and 18 during remifentanil infusions. Respiratory rate decreased and end-tidal carbon dioxide (ETCO(2)) increased with increasing doses of remifentanil; HR, direct blood pressure, muscle sympathetic nerve activity, SpO(2) remained unchanged, but FBF increased compared with placebo. In a second study (n = 7), timed respiration was used to maintain ETCO(2) during remifentanil, but FBF still increased. In a third study (n = 11), direct effects of remifentanil on vascular tone were determined with progressive infusions from 1 to 100 micro g/h into the brachial artery; FBF increased significantly from 3.5 to 4.3 mL/min per 100 mL of tissue (approximately 13%-18% increase). Sedative doses of remifentanil resulted in analgesia but no changes in neurocirculatory end-points except FBF. Direct effects of remifentanil on regional vascular tone may play a role in promoting hypotension., Implications: Remifentanil occasionally has been associated with hypotension, the mechanism of which is unclear. This study found that remifentanil directly causes the forearm arterial vasculature to dilate.

Unlabelled: We evaluated the cardio-respiratory effects of equi-sedative doses of dexmedetomidine and propofol for intraoperative sedation. Secondary comparison end points were time to achieve and terminate sedation and postoperative analgesia and psychomotor performance. Forty patients scheduled for elective surgery provided informed consent and were randomized equally to receive either dexmedetomidine (1 microg/kg initial loading dose for 10 min; maintenance, 0.4-0.7 microg. kg(-1). h(-1)) or propofol (75 microg. kg(-1). min(-1) x 10 min; maintenance, 12.5-75 microg. kg(-1). min(-1)). Hemodynamic variables (heart rate and mean arterial blood pressure), sedation (visual analog scale and Observer Assessment of Alertness/Sedation), bispectral index score of sedation, ventilation (respiratory rate, O2 sat, and ETCO2), psychomotor performance (digital symbol substitution test), and pain (visual analog scale) were determined during surgery and up to 95 min after surgery. Intraoperative sedation levels were targeted to achieve a bispectral index score of 70-80. Patient demographics, ASA class, surgical procedure, and baseline cardio-respiratory variables were similar between groups. Sedation was achieved more rapidly with propofol but was similar between groups 25 min after initiating infusions. The average infusion rate for dexmedetomidine was 0.7 microg. kg(-1). h(-1) and 38 microg. kg(-1). min(-1) for propofol. There were no differences between groups in psychomotor performance and respiratory rate during recovery. The previous use of dexmedetomidine resulted in more sedation, lower blood pressure, and improved analgesia (less morphine use) in recovery., Implications: Dexmedetomidine may be useful for perioperative sedation. It has a slower onset and offset of sedation compared with propofol. Dexmedetomidine was associated with improved analgesia and less morphine use in the postoperative period.

Unlabelled: Compared with equi-minimum alveolar anesthetic concentration (MAC) isoflurane, desflurane is associated with greater levels of sympathetic nerve activity in humans but similar reductions in blood pressure. To explore these divergent effects, we evaluated vascular alpha(1)-adrenoceptor responses in the human forearm during isoflurane and desflurane anesthesia to determine if alpha(1)-adrenoceptor responses were more substantially attenuated during desflurane administration. Bilateral forearm venous occlusion plethysmography was used to examine arterial blood flow and to determine changes in forearm vascular resistance during brachial artery infusions of saline and phenylephrine (0.2, 0.4, 0.8, and 1.6 microg/min) in 22 conscious subjects and during anesthesia with 0.65 and 1.3 MAC isoflurane or desflurane. Infusion of phenylephrine into the brachial artery increased the forearm vascular resistance in a dose-dependent manner. The arterial response to phenylephrine was significantly attenuated by 0.65 and 1.3 MAC desflurane and similarly attenuated during 1.3 MAC isoflurane (P < 0.05). Impaired arterial alpha(1)-adrenoceptor responsiveness occurred during desflurane. However, this effect was statistically similar (P > 0.05) to the impaired responses during isoflurane. Blood pressure decreases during volatile anesthesia may be, in part, caused by decreased alpha(1)-adrenoceptor responsiveness., Implications: alpha-receptors on blood vessels regulate constriction and dilation and therefore modulate blood pressure. This research indicates that vasoconstriction via the alpha(1)-receptor vascular response is impaired during isoflurane and desflurane anesthesia.