Awake endotracheal intubation can be achieved using a variety of equipment, such as video laryngoscopes, optical stylets, and fiber-optic scopes. Appropriate anesthesia of the airway and sedation can enable any of these techniques to be used successfully.
The commonest method used to perform an awake endotracheal intubation is with a flexible fiberscope, and an awake fiber-optic intubation is regarded as the gold standard for the endotracheal intubation of patients with an anticipated difficult airway. This procedure requires skills and knowledge that should be familiar to all anesthesiologists.
Recently, there have been many advances in regional anesthesia, allowing for more complicated and innovative procedures to be done under regional block techniques; however, not all of these cases can be done solely under regional anesthesia. Often, a combination of regional and general anesthesia is required; therefore, all anesthesiologists must be familiar with awake intubation techniques, especially if the patient has an anticipated difficult airway. Anesthetizing patients with an anticipated difficult airway is often a source of anxiety and trepidation, but appropriate airway topicalization and sedation techniques can create the appropriate conditions for a safe and stress-free procedure for both the patient and the anesthesiologist.
It is difficult to give precise figures on the incidence of difficult airways due to a variety of reasons, including population differences, operator skill variation, operator reporting, and an inconsistency in the definition of a difficult airway. In the general population, the approximate figures for the incidence of Cormack and Lehane laryngoscopy grades 3 and 4 is 10%, difficult intubation is 1%, and difficult bag mask ventilation is 0.08%–5%.
Endotracheal intubation is usually performed under general anesthesia, but if a difficult airway is anticipated, then this should ideally be done under regional anesthesia (with or without sedation) as this allows the patient to breathe spontaneously, maintain airway patency, and cooperate with the operator. If any untoward difficulties are experienced, then the procedure can be abandoned with minimum risk to the patient. There are obvious exceptions to performing an awake intubation, such as patient refusal, young children, and uncooperative patients (due to confusion or learning disabilities).
To successfully perform an awake endotracheal intubation, one should be familiar with the following:
- Sensory innervation of the upper airway
- Agents available for topicalization
- Application techniques available to topicalize the airway
- Regional anesthesia techniques, landmark or ultrasound-guided
- Safe sedation techniques
Traditionally, lumbar plexus block (LPB) is performed using surface anatomical landmarks to identify the site for needle insertion and eliciting quadriceps muscle contraction in response to nerve electrolocalization, as described in the nerve stimulator-guided chapter. The main challenges in accomplishing LPB relate to the depth at which the lumbar plexus is located and the size of the plexus, which requires a large volume of local anesthetic for success.(1) Due to the deep anatomical location of the lumbar plexus, small errors in landmark estimation or angle miscalculations during needle advancement can result in needle placement away from the plexus or at unwanted locations. Therefore, monitoring the needle path and final needle tip placement should increase the precision of the needle placement and the delivery of local anesthetic. Although computed tomography and fluoroscopy can be used to increase precision during LPB, these technologies are impractical in the busy operating room environment, costly, and associated with radiation exposure. It is only logical, then, that ultrasound (US)-guided LPB be of interest because of the ever-increasing availability of portable machines and the improvement in the quality of the images obtained.(2,3)
Caudal anesthesia was described at the turn of last century by two French physicians, Fernand Cathelin and Jean-Anthanase Sicard. The technique pre-dated the lumbar approach to epidural block by several years.(1) Caudal anesthesia, however, did not gain in popularity immediately following its inception. One of the major reasons caudal anesthesia was not embraced is the wide anatomical variations of sacral bones and the consequent failure rate associated with attempts to locate the sacral hiatus. The failure rate of 5% to 10% made caudal epidural anesthesia unpopular until a resurgence of interest in the 1940s, led by Hingson and colleagues, who used it in obstetrical anesthesia. Caudal epidural anesthesia has many applications, including surgical anesthesia in children and adults, as well as the management of acute and chronic pain conditions. Success rates of 98%–100% can be achieved in infants and young children before the age of puberty, as well as in lean adults.(1) The technique of caudal epidural block in pain management has been greatly enhanced by the use of fluoroscopic guidance and epidurography, in which high success rates can be attained.
Unfortunately, clinical indications, and especially therapeutic interventions for the relief of chronic pain in individuals with failed back surgery syndrome, are often most prevalent in patients with difficult caudal landmarks. It has been suggested that traditional lumbar peridural block should not be attempted employing an approach requiring needle placement through a spinal surgery scar due to the likelihood of tearing the dura and the possibility of inducing hematoma formation over the cauda equina when blood from the procedure becomes trapped between the layers of scar and connective tissues.(2) Under these circumstances, it is recommended that fluoroscopically guided caudal epidural block be performed in lieu of the traditional palpation approach. Alternatively, the use of ultrasound may be appropriate to identify the sacral hiatus, and this technique has recently been described. The second resurgence in popularity of caudal anesthesia has paralleled the increasing need to find safe alternatives to conventional lumbar epidural block in selected patient populations, such as individuals with failed back surgery syndrome.
INTRODUCTION AND DEFINITION OF ELDERLY
Healthcare providers have become increasingly focused on providing effective management of acute perioperative pain in all patients, but especially older adults, as the size of this patient population has steadily increased in recent years.(1) Advances in anesthetic and surgical techniques, an improved understanding of the pathophysiology of pain, the development of new opioid and nonopioid analgesic drugs, the incorporation of regional techniques that reduce or eliminate reliance on traditional opioid analgesics, and novel methods of drug delivery have all led to greater numbers of older patients undergoing major surgery.(2,3) An increased prevalence of chronic medical conditions among older individuals may also lead to higher degrees of acute and chronic pain (including acute-on-chronic pain). For instance, acute exacerbations of arthritis, osteoporotic fractures of the spine, cancer pain, and pain from acute medical conditions (eg, ischemic heart disease, herpes zoster, peripheral vascular disease) must be properly addressed in order to maximize multimodal perioperative pain management.(4) In addition, older individuals are adopting more active lifestyles that can predispose them to trauma and orthopedic injuries that require surgery.
The term elderly encompasses both chronologic and physiologic factors. Chronologic age is the actual number of years an individual has lived, whereas physiologic age refers to functional capacity or reserve within organ systems defined in pathophysiologic parameters. The chronologic component can be divided into two separate groups: the “young old” (65 to 80 years of age) and the “older old” (greater than 80 years of age).(5) Physiologic reserve describes the functional capacity of organ systems to compensate for acute stress and traumatic derangements. When present, comorbid disease states such as diabetes mellitus, arthritis, renal insufficiency, ischemic heart disease, and chronic obstructive pulmonary disease (COPD) can all decrease a patient’s physiologic reserve making it difficult for him or her to recover from traumatic or surgical injury.
There are a host of additional factors that may compromise the ability to provide optimal and effective acute pain management to older patients. A consequence of the comorbid diseases that afflict this patient population with increased frequency is the medications used in treatments for such diseased conditions, along with a subsequent increased risk of drug-to-drug and disease-to-drug interactions. An improved understanding of age-related changes in physiology, pharmacodynamics, and pharmacokinetics must be incorporated into any acute pain medicine care plan for older individuals. Altered responses to pain among the elderly population along with difficulties in pain assessment for certain individuals with cognitive dysfunction are potential problems that must also be considered.
Several theories have been advocated to describe the multi-dimensional aspects and consequences of aging that underscore the complexities and difficulties encountered in developing optimal regional anesthetic and analgesic choices for elderly patients. Therefore, the focus of this chapter is to outline the physiologic and pharmacologic implications of aging on surgical anesthesia and acute pain management, as well as the potential risks and benefits of neuraxial blockade along with peripheral nerve/nerve plexus blockade in geriatric patients.