Thomas E. Shaughnessy, M.D.
Assistant Professor of Anesthesia and Perioperative Care
UCSF Medical Center San Francisco, CA 94143-0648
shaughnt@anesthesia.ucsf.edu

Within the next decade, it is estimated that 20-40 percent of anesthetic cases may be performed outside the operating room. Patient demand has also influenced this trend, with surveys showing the elderly preferring more ambulatory settings.¹ In addition, Medicare also favors outpatient protocols for certain procedures.

This expansion of outpatient procedures for the elderly must be viewed with caution because perioperative complications increase with age. The etiology of this observation is controversial but is probably more a function of associated concurrent diseases than age in and of itself.² In addition, liability claims for adverse events associated with sedation have substantially increased. Levels of injury are comparable with general anesthetics, with those injured tending to be older, more debilitated and performed on an outpatient basis.

One must appreciate that geriatric patients have limited physiologic reserves. There is less heart rate responsiveness in response to hypotension.³ Ventilatory responses to hypoxia and hypercarbia are reduced, with greater risks for apnea. Impairments in thermoregulation and water balance increase vulnerability for hypovolemia and hypothermia. Changes in volume of distribution, bioavailability and receptor sensitivity lead to alterations in pharmacodynamics for most drugs. Limitations in renal clearance and hepatic function require attenuation of dosage. Since many elderly have prolonged circulation time, longer periods are required for interval dosing. Thus, titration to effect is an important principle in applying clinical judgment to the geriatric patient.⁴

Delirium may occur in a high percentage of elderly surgical patients.⁵ This should give rise to caution for similar potential in the sedated geriatric patient. Procedures in remote locations often have anesthetic requirements that rival many operating room procedures. The risk of delirium may be increased with agents such as midazolam, meperidine and anticholinergics. Immobilization and prolonged nothing by mouth (NPO) status are prominent contributing factors for periprocedure delirium. Because of increased sensitivity to medications, patients with any baseline disorientation should be insured of overnight observation. There is evidence that interventions such as repeated orientation, maintaining sensory aids and familiar family contacts are key factors in delirium prevention.⁵

When sedating the geriatric patient, the agent of choice should have a short half-life, with minimal active metabolites and limited side effects. One should avoid using standard dosages calculated on a mg/ kg basis. These boluses frequently produce unwanted respiratory depression and hypotension. Likewise, slower administration of an agent and allowing more time for peak effects often achieves the desired goals with less overall dose.

Midazolam and fentanyl are a common combination used for conscious sedation. Due to increased sensitivity in the elderly and decreased clearance of these agents, smaller doses and more delayed increments must be used. Propofol also has a reduced clearance in the elderly. Older patients require lower doses for any given effect, in many cases as little as 50 percent of the expected "standard" dose.⁶

Remifentanil is the newest ultra short-acting agent on the market and its use is currently being explored. It offers potent, rapid analgesia, but its rapid offset may be a double-edged sword in cases involving prolonged discomfort. In the elderly, its use appears to be associated with an increased incidence of hypoventilation.⁷ While clearance is quite rapid and independent of age, the dosage required for clinical effect in the elderly is at most 50 percent of package insert guidelines. Its utility as a sedative needs to be more thoroughly evaluated, but at this time there appears to be only modest enthusiasm compared to other currently available agents.

Safe sedation of elderly patients also includes maintaining appropriate practice standards in all areas where these agents are administered. The Joint Commission on Accreditation of Healthcare Organizations addressed this issue by mandating that institutions develop protocols for conscious sedation. While they do not set specific standards for practice, they state that institutions should have polices dealing with evaluation, personnel, equipment, monitoring and recovery. They also require evidence of monitoring for compliance. Anesthesiologists should be involved in the establishment of these protocols because they optimize patient safety through identification of patients who require care beyond the scope of conscious sedation.

Among various logistic considerations, geriatric patients take longer to accomplish many tasks. Thus, more time must be allowed for preprocedure preparation. Also, older patients' skin may be fragile, so adhesive tape should be used with caution to avoid torn skin. Extra padding should be used on procedure tables to prevent compression sores. The elderly are less agile and may require equipment aids (e.g., chair raisers or footstools). Many elderly are hearing impaired, so verbal and written post-procedure instructions may foster comprehension.

Several novel approaches to sedation have recently evolved, and a few may prove useful in enhancing the care of geriatric patients undergoing procedures in remote locations. Similar to patient controlled analgesia, the concept of patient controlled sedation is now being explored. Several studies have demonstrated its safe and efficacious use for conscious sedation in the operating room.^8,9 However, one study, which used Propofol in the treatment of the elderly, found an increased incidence of profound sedation.⁹ The boundaries of this technique have yet to be defined.

Bispectral index monitoring (BIS) is currently being evaluated as a level of consciousness monitoring. The processed EEG signal is quantitated and used as an indicator of sedation level. It may allow the titration of sedatives by minimizing usage of agents, thus speeding up recovery time.¹⁰

For anesthesia departments noting increased usage of conscious and deep sedation outside their operating rooms, we may see the advent of formal anesthesia sedation services available throughout a hospital community. Advantages of such a service include providing a hospital with timely, reliable, high-quality service with an optimization of recovery and turnaround time.

In summary, sedation of the geriatric patient in remote locations requires appreciation of their physiologic limitations and underlying co-morbid conditions. The clinician must pay attention to periprocedural care, including use of short acting agents, in conjunction with a judicious dosing strategy.

References:

1. Koska MT. Ambulatory surgery gets high marks from the elderly. Hospitals. 1990; 64:55.
2. Tiret L, Desmonts JM, Hatton F, Vourc'h G. Complications associated with anaesthesia--a prospective survey in France. Can Anaesth Soc J. 1986; 33:336-344
3. Larsen B, Buch U, Wilhelm W, Larsen R. [Effects of propofol and fentanyl on the baroreceptor reflex in geriatric patients]. Anasthesiol Intensivmed Notfallmed Schmerzther. 1994; 29:408-412.
4. Darling E. Practical considerations in sedating the elderly. Crit Care Nurs Clin North Am. 1997; 9:371-380.
5. O'Keeffe ST, Ni Chonchubhair A. Postoperative delirium in the elderly. Br J Anaesth. 1994; 73:673-687.
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10. Glass PS, Bloom M, Kearse L, Rosow C, Sebel P, Manberg P. Bispectral analysis measures sedation and memory effects of propofol, midazolam, isoflurane, and alfentanil in healthy volunteers. Anesthesiology. 1997; 86: 836-847.