Acute Postoperative Pain Management in the Older Patient

Thor Hallingbye; Jacob Martin; Christopher Viscomi

Aging Health. 2011;7(6):813-828.

Abstract and Introduction

Abstract

Acute pain management in the older adult is both challenging and rewarding. This review addresses the difficulty with assessment of pain in the older adult, variations in the pain experience of older adults, physiological differences between the young and old, changes in pharmacokinetics and pharmacodynamics with age, and useful pharmacological treatments for acute pain in older adults. It then presents a few representative cases of pain management in older adults. The goal of this review is to provide relevant information that can be used to manage acute postoperative pain in the older adult.

Introduction

The United States Census Bureau predicts that the population of the USA will increase from 310 million in 2010 to 439 million by 2050. The baby boomer population (those born between 1946 and 1964) will begin to turn 65 years of age in 2011 and consequently the population of Americans who are 65 years old or older will grow from 13% in 2010 to 20.2% by 2050. In fact, centenarians will demonstrate a 437% growth in population over the next 40 years.^[201] In 2007, approximately 35% of surgical procedures were performed in patients 65 years and older.^[202] Approximately 42% of hospitalized older patients receive at least one procedure during admission, compared with only 10% in those less than 65 years of age.

Chronic health conditions, including chronic pain, are common in older adults. Chronic musculoskeletal pain from degenerative bone, joint and spine diseases is prevalent in the elderly population.^[1] Neuropathic pain, such as that experienced as a result of diabetic neuropathy, postherpetic neuralgia and poststroke or amputation pain is quite common. Chronic pain prevalence is estimated at 25–50% of community-dwelling older persons and probably up to 80% in elderly patients in nursing homes.^[2–4] Approximately 22% of elderly Americans are affected by some type of cancer and up to 80% of cancer patients experience pain related to their disease or disease treatment.^[5] Persistent pain in the older adult has been associated with increased healthcare utilization, sleep disturbances, decreased socialization and impaired ambulation.^[6] Between 8 and 20% of older patients display depressive symptoms, and depression has been associated with worsened pain.^[203]

Treating acute and/or chronic pain in the older patient can be challenging. Older patients typically have more medical comorbidities than their younger counterparts. They also take more prescription medications; on average two to five medications per person.^[7] Drug interactions are common and polypharmacy, as defined by regular use of five or more medications, is estimated at 20–40% in older patients.^[7] Additionally, inappropriate prescribing of medications places the older patient at risk for adverse reactions and preventable hospitalizations.^[8,9] Unfortunately, nearly 35% of medication trials exclude older patients based on age alone.^[10,11] Therefore, the effect of aging on pharmacokinetics and pharmacodynamics of drugs is incompletely characterized.

The risk of postoperative delirium (POD) and postoperative cognitive decline (POCD) increases with age.^[12,13] Hip fracture patients are at especially high risk of developing POD.^[14] Certain medications, such as tramadol, are associated with development of POD.^[15] Tramadol, while commonly used to treat acute and chronic pain in adults, will not be discussed further in this article as there is limited description of use in older adults in the literature. Please see the article by Lewis and Han for general information regarding tramadol.^[16] POD and POCD are also associated with preoperative cognitive impairment, vision impairment, depression and other common comorbidities, such as vascular disease and renal dysfunction.^[12] POCD is closely linked to delirium in the perioperative period, which is in turn related to acute pain and pain treatment, but risk for POCD may be independent of the type of anesthesia received.^[17,18] Although it may be assumed that general anesthesia and complex surgery would result in an increased likelihood of POCD, a recent study challenges this assumption.^[17] In this study, patients who received procedural sedation had the same risk of cognitive decline as those undergoing elective total hip joint replacement surgery or coronary artery bypass surgery. POD and POCD worsen the clinician's ability to assess pain and may lead to inappropriate treatment. The unfortunate result of POD and POCD is decreased level of function and increased morbidity and mortality.^[12]

This article will attempt to describe the assessment of pain in older patients, as well as differences in the pain experience between the old and young. Physiological and pharmacological differences will be described. In addition, focus will be turned on medication management in the acute setting. Unfortunately, many medications have not been studied well in the older population. Nonpharmacological approaches to postoperative pain management will not be discussed, although this would be an interesting topic for further discussion.

1 2 3 4 5 6 7 8 9

Next Section

Table 1. Pain assessment tools.
Tool	Description	Discussion
Visual Analogue Scale	A vertical or horizontal 100-mm line anchored by verbal descriptors such as 'no pain' and 'worst pain possible'. Patients make a mark on the line that represents their pain intensity	Requires abstract thought Difficult to use in cognitively or visually impaired May be less valid in older adults
Numerical Rating Scale	Available in a variety of scale ranges and anchors, such as 0–10, with 0 being 'no pain' and 10 being 'worst pain possible'	Requires abstract thought Valid in cognitively impaired Commonly recommended scale for pain assessment in older adults
Verbal Descriptor Scale	Available in a variety of scale types (e.g., pain thermometer, present pain intensity index and graphic rating scale)	Limited amount of choices Requires some command of language Highly preferred by older adults Low failure rate in cognitively impaired
Faces Pain Scale	Consists of seven faces ranging from neutral face (no pain) to grimacing face (worst pain possible)	Requires abstract thought Difficult to use in cognitively impaired May be less preferred by older adults
Behavioral Pain Scale	Observational assessment tool for nonverbal patients compiled by nurse or physician	Generally takes longer to complete Requires knowledge of how scale is used Better results if observer is very familiar with patient

Table 2. Physiologic changes in the older adult.
System	Older vs younger	Importance
Nervous system	Higher prevalence of cognitive impairment Decreased ability to assess pain if demented/delirious Decreases in neurotransmitters and receptors Decreased pain-transmitting nerve fiber function (Aδ and C)	May be worsened by pain medications Use behavioral scale to assess pain level Decrease in autonomic responsiveness (uncompensated hypotension following spinal or epidural anesthesia) Decreased capacity or speed of pain processing Increased pain threshold to short duration pain stimuli
Cardiovascular system	Decreased cardiac output by 1% per year after 30 years of age High frequency of cardiovascular disease	Higher peak arterial concentrations after intravenous dose of medication Severe consequence of untreated hypotension following spinal or epidural anesthesia
Pulmonary system	Decreased sensitivity to hypoxia/hypercarbia Increased incidence of sleep apnea	Postoperative treatment with oxygen Slow titration of opioids Longer interval between doses
Hepatic system	Decreased metabolism of drugs	Decrease dose, increase interval between doses
Renal system	Decreased GFR	Adjust medication dose according to GFR Cautious use of medications with renal toxicity risk (NSAIDs)

Table 3. Pharmacokinetic changes in older adults.
System	Older vs younger	Importance
*Drug absorption and bioavailability*
Gastric pH	5–10% of older patients have decreased gastric acid secretion Widespread PPI and H2 blocker therapy	Drugs requiring acidic environment are poorly absorbed (i.e., ketoconazole and/or iron salts)
Gastrointestinal motility	Delayed gastric emptying, peristalsis and colonic transit	Delay in time to achieve drug plasma levels Risk of constipation
Intestinal permeability	Probably no change in passive permeability
Gastrointestinal blood flow	Probably diminished flow	Limits absorption of highly permeable drugs
Gut wall drug metabolism	Probably diminished	May lead to higher bioavailability (i.e., morphine)
*Volume of distribution*
Serum protein binding of drugs	10% decrease in albumin concentration Increase in α-1-acid glycoprotein	Higher unbound fraction of some drugs (i.e., fentanyl, propofol, midazolam and/or naproxen) Decreased unbound fraction of some drugs (i.e., lidocaine)
Body fat	Increased 20–40%	Higher volume of distribution for lipophilic drugs (i.e., fentanyl and diazepam)
Body water	Decreased 10–15%	Lower volume of distribution for hydrophilic drugs (i.e., morphine)
*Hepatic metabolism*
Hepatic blood flow	Decreased up to 40%	May affect drugs with flow-limited metabolism (i.e., morphine)
Hepatic mass	Decreased up to 40%	May affect drugs with flow-limited metabolism
Phase I metabolism	Potential decrease in some CYP450 enzymes	May affect drugs with capacity-limited metabolism (i.e., theophylline)
Phase II metabolism	No reduction in hydrolysis, reduction or conjugation	Unaffected
*Renal clearance*
Glomerular filtration rate	Reduction by approximately 1 ml/min/year after middle age Wildly variable depending on comorbidities	May require large reductions in dose of renally excreted drugs with narrow therapeutic index and drugs with active metabolites
Renal mass	Decreased up to 25%

Box 1. Opioid dosing in the opioid-tolerant surgical patient.
Step 1: obtain accurate history of opioid consumption Step 2: convert outpatient oral opioids to equivalent dose of parenteral opioids Step 3: multiply the Step 2 dose by 200–400% to predict daily parenteral opioid needs immediately after surgery Step 4: if an intravenous patient-controlled analgesia device will be used, divide Step 3 calculation by 24 to determine hourly maximum dose of opioid to be delivered by patient-controlled analgesia pump

Sidebar

Executive Summary

Background

Acute and chronic pain are increasingly prevalent in the aging population of the USA. Treatment of pain is complicated by medical comorbidities and the risk of postoperative delirium and cognitive decline.

Challenges of assessing pain in the older patient

Numerous pain assessment scales have been validated in the older population. In cognitively intact older adults, self-report scales are very reliable. In cognitively impaired older adults, behavioral scales are more valid.

Pain experience in the older adult

Sex and age-related differences in pain experience probably exist, but the clinical significance is unclear. Misconceptions about pain experience expose older adults to the risk of undertreatment.

Physiological changes of aging

Aging produces physiological changes within the body. There is a higher prevalence of cognitive impairment, cardiac dysfunction and hepatic and renal impairment in the older population.

Pharmacokinetics & pharmacodynamics: application to drug dosing in the older adult

There are wide variations in pharmacokinetic and pharmacodynamic changes apparent between older individuals. Increased body fat composition leads to higher volume of distribution for fat-soluble drugs and lower volume of distribution for water-soluble drugs.
Decreased hepatic and renal function is probable, with the effect of renal impairment being more important on drug metabolism and elimination. Pharmacodynamic changes are prevalent in the central nervous and cardiac systems.

Analgesic drug classes

Opioids are the prototypical pain medication. They can be safely used in older adults, but there are risks, including side effects, tolerance and opioid-induced hyperalgesia.
Acetaminophen has significant opioid-sparing ability, is well tolerated and can be administered by multiple routes.
NSAIDs have significant opioid-sparing ability. Nonselective COX inhibitors have side effects that the clinician must be aware of. COX-2 inhibitors may decrease the risk of gastrointestinal side effects.
Gabapentinoids have been shown to decrease perioperative pain and risk for development of chronic incisional pain.
N-methyl-D-aspartate receptor antagonists have significant opioid-sparing ability, but their use can be limited by side effects.

Case presentations

Cases presented to illustrate evidence-based decision-making regarding perioperative analgesia.

Comments

Commenting is limited to medical professionals. To comment please Log-in.

Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.