There is accumulating evidence to implicate the importance of N-methyl-d-aspartate (NMDA) receptors to the induction and maintenance of central sensitization during pain states. However, NMDA receptors may also mediate peripheral sensitization and visceral pain. NMDA receptors are composed of NR1, N

The role of N-methyl-D-aspartate (NMDA) receptors in pain: a review.

Efficacy of antiseptic-impregnated central venous catheters in preventing catheter-related bloodstream infection. A Meta-analysis

https://emcrit.org/wp-content/uploads/2011/10/Preox-annals-article.pdf

Preoxygenation and Prevention of Desaturation During Emergency Airway Management

Background: Class III obese patients have altered respiratory mechanics, which are further impaired in the supine position. The authors explored the hypothesis that preoxygenation in the 25° head-up position allows a greater safety margin for induction of anesthesia than the supine position. Methods: A randomized controlled trial measured oxygen saturation and the desaturation safety period after 3 min of preoxygenation in 42 consecutive (male:female 13:29) severely obese (body mass index > 40 kg/m 2 ) patients who were undergoing laparoscopic adjustable gastric band surgery and were randomly assigned to the supine position or the 25° head-up position. Serial arterial blood gases were taken before and after preoxygenation and 90 s after induction. After induction, ventilation was delayed until blood oxygen saturation reached 92%, and this desaturation safety period was recorded. Results: The mean body mass indexes for the supine and 25° head-up groups were 47.3 and 44.9 kg/m 2 , respectively (P 0.18). The group randomly assigned to the 25° head-up position achieved higher preinduction oxygen tensions (442 104 vs. 360 99 mmHg; P 0.012) and took longer to reach an oxygen saturation of 92% (201 55 vs. 155 69 s; P 0.023). There was a strong positive correlation between the induction oxygen tension achieved and the time to reach an oxygen saturation of 92% (r 0.51, P 0.001). There were no adverse events associated with the study. Conclusion: Preoxygenation in the 25° head-up position achieves 23% higher oxygen tensions, allowing a clinically significant increase in the desaturation safety period— greater time for intubation and airway control. Induction in the 25° head-up position may provide a greater safety margin for airway control.

Preoxygenation Is More Effective in the 25° Head-up Position Than in the Supine Position in Severely Obese Patients

• We prospectively studied the results of 714 attempts at central venous catheterization during an eight-month period in our intensive care department. We compared the rates of failure of catheterization and early complications among three percutaneous approaches: subclavian, anterior jugular, and posterior jugular veins. The procedures were performed by experienced staff or resident physicians and inexperienced interns and residents under teaching supervision. Overall rates of failure and complication were similar for each percutaneous approach within each group of physicians. Overall failure rate was 10.1% for the experienced group and 19.4% for the inexperienced. The complication was 5.4% for experienced and 11% for inexperienced. Among inexperienced physicians, the success rate was 86.7% and the complication rate 7.6% in unconscious patients, whereas in conscious patients these rates were 70.5% and 13.8%, respectively. The inexperienced physicians caused fewer complications in mechanically ventilated than in spontaneously breathing patients. We suggest that inexperienced physicians should first attempt central vein catheterizations in unconscious and mechanically ventilated patients. (Arch Intern Med1986;146:259-261)

Central Vein Catheterization. Failure and Complication Rates by Three Percutaneous Approaches

Background: Hypoxemia during the induction of general anesthesia for the morbidly obese patient is a major concern of anesthesiologists. The etiology of this pathophysiological problem is multifactorial, and patient positioning may be a contributing factor. The present study was designed to identify optimal patient positioning for the induction of general anesthesia that minimizes the risk of hypoxemia in these patients. Methods: 26 morbidly obese patients (body mass index - BMI 56±3) were randomly assigned to one of three positions for induction of anesthesia: 1) 30° Reverse Trendelenburg; 2) Supine-Horizontal; 3) 30° Back Up Fowler. Mask ventilation, full neuromuscular paralysis and direct laryngoscopy were performed. Any airway difficulties were noted. After endotracheal tube placement, subjects were ventilated for 5 minutes with 1% isoflurane in a mixture of 50% oxygen / 50% air and then disconnected from the ventilation circuit.The time required for capillary oxygen saturation (SaO2), as measured by pulse oximeter, to decline from 100% to 92% was noted and identified as the safe apnea period (SAP). Ventilation was then immediately re-established.The lowest SaO2 after resuming ventilation and the time from that nadir to an SaO2 of 97% were also recorded. Results: BMI and hip-waist ratios of patients in groups 1, 2 and 3 did not significantly differ. There were no differences in airway difficulties between the different groups. The SAP in groups 1, 2 and 3 was 178±55, 123±24 and 153±63 seconds, respectively. The SaO2 of patients in the reverse Trendelenburg position dropped the least and took the shortest time to recover to 97%. Conclusions: In morbidly obese patients, the 30° Reverse Trendelenburg position provided the longest SAP when compared to the 30° Back Up Fowler and Horizontal-Supine positions. Since on induction of general anesthesia morbidly obese patients may be difficult to mask ventilate and/or intubate, this extra time may preclude adverse sequelae resulting from hypoxemia. Therefore, Reverse Trendelenburg is recommended as the optimal position for induction.

A preliminary study of the optimal anesthesia positioning for the morbidly obese patient.

Background: The effect of ketamine as a treatment of visceral pain is not known. The current study investigated the effect of ketamine on spinal dorsal horn neurons excited by urinary bladder distension (UBD). The effect of other clinically available N-methyl-D-aspartate receptor antagonists on these responses was also studied. Metbods: Extracellular recordings of neurons located in the L6-S2 spinal dorsal horn of cervical spinal cord-transected, decerebrate female rats were obtained. Cutaneous receptive fields of neuronal units excited by UBD were characterized for responses to segmental noxious and nonnoxious stimuli. Nonsegmental noxious stimuli were also applied, and neurons were classified as type I (inhibited) and type II (noninhibited) by the stimulus. The effect of intravenous ketamine (1, 3, and 10 mg/kg), dextromethorphan (5 mg/kg), and memantine (16 mg/kg) on neuronal responses of these units was measured. Results: Spontaneous and evoked neuronal activity to UBD was reduced in a dose-dependent fashion by ketamine. Responses to nonnoxious cutaneous stimuli were also significantly reduced after treatment. Dextromethorphan inhibited neuronal activity evoked by UBD in type I neurons. A similar selective effect of treatment on type I versus type II neurons was observed after intravenous ketamine and memantine. Conclusions: Intravenous ketamine produces dose-dependent inhibition of the spinal cord neuronal responses evoked by UBD. All three N-methyl-D-aspartate receptor antagonists showed selective effects on spinal cord neurons subject to counterirritation. This neurophysiologic evidence supports a spinally mediated analgesic effect of ketamine in this model of urinary bladder nociception, an effect likely caused by N-methyl-D-aspartate receptor antagonism.

Ketamine, an N-methyl-D-aspartate receptor antagonist, inhibits the reflex responses to distension of the rat urinary bladder.

Spinal neurophysiologic correlates of the analgesic actions of intravesical dimethyl sulfoxide and capsaicin in the rat.

Acute bladder inflammation differentially affects rat spinal visceral nociceptive neurons.

/pdf/abordaje-medio-para-cateterizacion-central-de-la-vena-ism8ewxn3q.pdf

Pablo Castromán

Papers

A preliminary study of the optimal anesthesia positioning for the morbidly obese patient.

Ketamine, an N-methyl-D-aspartate receptor antagonist, inhibits the reflex responses to distension of the rat urinary bladder.

Spinal neurophysiologic correlates of the analgesic actions of intravesical dimethyl sulfoxide and capsaicin in the rat.

Acute bladder inflammation differentially affects rat spinal visceral nociceptive neurons.

Abordaje medio para cateterización central de la vena Yugular Interna.