Clinical Trials: A Practical Approach

Summary Problems with tracheal intubation are infrequent but are the most common cause of anaesthetic death or brain damage. The clinical situation is not always managed well. The Difficult Airway Society (DAS) has developed guidelines for management of the unanticipated difficult tracheal intubation in the non-obstetric adult patient without upper airway obstruction. These guidelines have been developed by consensus and are based on evidence and experience. We have produced flow-charts for three scenarios: routine induction; rapid sequence induction; and failed intubation, increasing hypoxaemia and difficult ventilation in the paralysed, anaesthetised patient. The flowcharts are simple, clear and definitive. They can be fully implemented only when the necessary equipment and training are available. The guidelines received overwhelming support from the membership of the DAS. Disclaimer: It is not intended that these guidelines should constitute a minimum standard of practice, nor are they to be regarded as a substitute for good clinical judgement.

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Difficult Airway Society guidelines for management of the unanticipated difficult intubation

The purpose of this article is to review the literature on the side effects of intrathecal and epidural opioids. English-language articles were identified through a MEDLINE search and through review of the bibliographies of identified articles. With the increasing utilization of intrathecal and epidural opioids in humans during the 1980s, a wide variety of clinically relevant side effects have been reported. The four classic side effects are pruritus, nausea and vomiting, urinary retention, and respiratory depression. Numerous other side effects have also been described. Most side effects are dose-dependent and may be more common if the opioid is administered intrathecally. Side effects are less common in patients chronically exposed to either intrathecal, epidural, or systemic opioids. Some side effects are mediated via interaction with specific opioid receptors while others are not. It is concluded that the introduction of intrathecal and epidural opioids marks one of the most important breakthroughs in pain management in the last two decades. However, a wide variety of clinically relevant non-nociceptive side effects may occur. All physicians utilizing intrathecal and epidural opioids must be aware of these side effects, for while most are minor, others are potentially lethal.

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Side effects of intrathecal and epidural opioids.

Uptake of local anesthetics injected into the subarachnoid space determines which neuronal functions are affected during spinal anesthesia. Elimination of local anesthetics from the subarachnoid space determines the duration of these effects. Distribution of local anesthetics within cerebrospinal fluid (CSF) determines the extent of altered neuronal function. Uptake and elimination have been reviewed previously (1). The present review deals with distribution, the determinant of the level of spinal anesthesia. Studies of drug distribution usually rest upon measurements of concentrations of the drug as a function of time after administration. Technical and ethical considerations make it impossible to take multiple samples of CSF at different levels of the subarachnoid space in patients. Reliance must, therefore, be placed upon estimates of distribution of local anesthetics in CSF not by measuring drug concentrations in CSF but, instead, by measuring the extent of neurologic responses to local anesthetics in CSF. The neurologic response that will be relied upon in this review, for estimation of local anesthetic distribution in CSF, is the spinal segmental level of anesthesia. Anesthesia is defined (for the present purposes only) as loss of pinprick sensation. This definition of anesthesia is employed because it is the definition most widely used by clinicians in determining the level to which local anesthetic solutions have spread. Differences between the levels of anesthesia as thus defined and levels of analgesia, somatic motor paralysis, sympathetic denervation, and other forms of neuronal impairment are not dwelt upon. These other forms of

Distribution of local anesthetic solutions within the subarachnoid space.

The PROSPECT Working Group, a collaboration of anaesthetists and surgeons, conducts systematic reviews of postoperative pain management for different surgical procedures (http://www.postoppain.org). Evidence-based consensus recommendations for the effective management of postoperative pain are then developed from these systematic reviews, incorporating clinical practice observations, and transferable evidence from other relevant procedures. We present the results of a systematic review of pain and other outcomes following analgesic, anaesthetic and surgical interventions for total knee arthroplasty (TKA). The evidence from this review supports the use of general anaesthesia combined with a femoral nerve block for surgery and postoperative analgesia, or alternatively spinal anaesthesia with local anaesthetic plus spinal morphine. The primary technique, together with cooling and compression techniques, should be supplemented with paracetamol and conventional non-steroidal anti-inflammatory drugs or COX-2-selective inhibitors, plus intravenous strong opioids (high-intensity pain) or weak opioids (moderate- to low-intensity pain).

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2044.2008.05565.x

A procedure-specific systematic review and consensus recommendations for postoperative analgesia following total knee arthroplasty

The current study was initiated to evaluate the epidural anesthetic properties of 0.5%, 0.75%, and 1.0% ropivacaine, a new local anesthetic agent structurally similar to bupivacaine. Fifteen patients scheduled for lower limb orthopedic surgery were enrolled in the study. As the concentration of ropivacaine increased from 0.5% to 1.0%, the time to onset of sensory anesthesia decreased from 6.4 +/- 1.7 (SD) min to 2.4 +/- 0.6 min and the maximum level of sensory anesthesia increased from T6 to T1. These changes were not statistically significant. Time to regression of anesthesia to T12 increased from 255 +/- 73 min with the 0.5% solution to 356 +/- 75 min with 1.0% ropivacaine (P less than 0.05). The degree of motor blockade using the Bromage scale varied with the concentration. When the 0.5% concentration was used, only one patient (20%) had greater than 1+ motor blockade. However, all of the patients receiving the 0.75% or 1.0% solution had at least 2+ motor blockade. Sensory anesthesia was adequate for surgery in 14 of the 15 patients. The mean peak plasma concentration of ropivacaine (Cmax) increased from 0.65 +/- 0.15 micrograms/mL with the 100-mg dose to 1.30 +/- 0.43 microgram/mL with the 200-mg dose. No adverse effects were noted in any patient in the study. These initial studies in humans suggest that ropivacaine provides satisfactory sensory anesthesia with minimal motor blockade at a concentration of 0.5%. An increase in concentration resulted in a more profound motor blockade. The Cmax of ropivacaine in this study was below levels associated with toxicity in animal studies.

A new local anesthetic, ropivacaine. Its epidural effects in humans.

A randomized double-blind study was conducted in 50 orthopedic patients to determine the effect of epinephrine and phenylephrine on the anesthetic properties of intrathecally administered tetracaine. Two doses of each vasoconstrictor agent were studied: 0.2 mg of epinephrine, 0.3 mg of epinephrine, 1 mg of phenylephrine, and 2 mg of phenylephrine. The results show that both vasoconstrictor agents in the doses used significantly prolong duration of sensory anesthesia and motor blockade produced by the subarachnoid administration of tetracaine. At equipotent doses no differences existed between the ability of epinephrine and phenylephrine to prolong the duration of spinal anesthesia produced by tetracaine.

Vasoconstrictors in spinal anesthesia with tetracaine--a comparison of epinephrine and phenylephrine.

25%, severe global hypokinesis, and moderate mitral regurgitation. The patient also had a history of hypertension, atria1 fibrillation (AF), and noninsulin-dependent diabetes. His preoperative medications included digoxin, furosemide, enalapril, nitroglycerin patch, and glyburide. He had no known drug allergies. On physical examination, the patient was 180 cm in height and weighed 62 kg. Heart rate (HR) and blood pressure (BP) were 74 bpm and 120/70 mm Hg, respectively. Head and neck evaluation was significant for a Mallampati class II airway and decreased range of motion of the neck. The cardiac examination revealed an irregularly irregular heart beat with a grade 3/6 systolic murmur. The lungs were clear to auscultation. The electrocardiogram (ECG) revealed AF with a ventric

Continuous spinal anesthesia with invasive hemodynamic monitoring for surgical repair of the hip in two patients with severe aortic stenosis.

Pregnancy is associated with a wider dermatomal spread of local anesthetics after epidural and spinal anesthesia. This phenomenon also exists in the immediate postpartum period. The mechanism of this observation is unresolved. However, an increase in progesterone concentration in pregnancy has been implicated as one of the factors. Although plasma progesterone concentrations in humans have been well-documented, the cerebrospinal fluid (CSF) progesterone levels, which may also be important in this regard, have not been determined. Therefore, this study was undertaken to measure plasma and CSF progesterone in the nonpregnant, term parturient and in the immediate postpartum patient and also to determine the relationship between the CSF progesterone concentration and the intrathecal spread of lidocaine used for spinal anesthesia. The plasma progesterone concentrations in 12 nonpregnant, 21 term and eight postpartum patients were 2.3 +/- 61 (SEM) ng/ml, 122 +/- 8 ng/ml and 16 +/- 2.2 ng/ml, respectively. The CSF progesterone concentrations in term parturients (3 +/- 0.28 (SEM) ng/ml) and postpartum patients (1.03 +/- 0.16 ng/ml) were eight and three times greater than that of nonpregnant women (0.39 +/- 0.01 ng/ml). Significantly less lidocaine was needed (P less than 0.05) for comparable segmental levels of spinal anesthesia in term and postpartum patients than in nonpregnant individuals. These data suggest that high CSF, plasma progesterone concentrations, or both may augment the anesthetic spread of lidocaine.

Plasma and cerebrospinal fluid progesterone concentrations in pregnant and nonpregnant women.

We reviewed the records of 128 patients who had a total of 128 consecutive posterior operations on the cervical spine for problems related to rheumatoid arthritis. Our purpose was to examine perioperative complications related to the airway. The patients were divided into two groups for analysis on the basis of the technique of intubation that had been used. An upper-airway obstruction developed after extubation in eight (14 per cent) of the fifty-eight patients who had been intubated without fiberoptic assistance compared with one (1 per cent) of the seventy patients who had been intubated fiberoptically (p = 0.02). The two groups had similar characteristics with regard to age, sex, severity of the myelopathy, American Rheumatology Association classification, American Society of Anesthesiologists physical status classification, cigarette use, duration of the arthritis, use of preoperative traction, use of steroids (both preoperatively and intraoperatively), size of the endotracheal tube, duration of the operation, total duration of the anesthesia, intraoperative fluid balance, and type of immediate immobilization of the neck. The only significant difference between the groups was the time to extubation, which averaged 17.9 hours in the fiberoptic group and 10.6 hours in the non-fiberoptic group (p = 0.02). Logistic regression analysis showed that non-fiberoptic intubation was the significant risk factor, even when allowance was made for the difference in the lengths of time to extubation. We concluded that this life-threatening complication can be minimized with fiberoptic management of the airway.

Upper-Airway Obstruction and Perioperative Management of the Airway in Patients Managed with Posterior Operations on the Cervical Spine for Rheumatoid Arthritis.

Mercedes Concepcion

Papers

A new local anesthetic, ropivacaine. Its epidural effects in humans.

Vasoconstrictors in spinal anesthesia with tetracaine--a comparison of epinephrine and phenylephrine.

Continuous spinal anesthesia with invasive hemodynamic monitoring for surgical repair of the hip in two patients with severe aortic stenosis.

Plasma and cerebrospinal fluid progesterone concentrations in pregnant and nonpregnant women.

Upper-Airway Obstruction and Perioperative Management of the Airway in Patients Managed with Posterior Operations on the Cervical Spine for Rheumatoid Arthritis.