Regional anesthesia for acute pain management in elderly patients

Table 1 Pharmacokinetics alterations with aging[5,7]

Organ system	Deficits with aging
Liver	Decrease in hepatic blood flow will result in reduction of first pass elimination, phase I metabolism affected earlier than phase II
Kidneys	Reduction in renal blood flow cause decrease in both creatinine clearance, glomerular filtration rate and tubular secretion activities
Plasma drug-binding proteins	Decrease in albumin or other binding proteins will result in higher fraction of plasma free drug
Fluid distribution	Decrease in total body water and muscle, and increase in total body fat may results in smaller effective dose and longer duration of drug effect, especially for lipophilic drugs

Table 2 List of older patient considerations related to regional anesthesia/analgesia

Indications	Contraindications
Poor cardiac reserve in patients who may not tolerate general anesthesia	Patient refusal
Poor pulmonary reserve: general anesthesia may result in prolonged mechanical ventilation	Sepsis, systemic infection and local infection are relative contraindications, and need to be assessed individually
Known history of adverse cognitive effects due to opioids and/or general anesthesia	Sedation and agitation may place patients at risk during PNB procedures
Severe hepatic insufficiency	Coagulopathy; relative contraindication with superficial PNB where bleeding can be easily controlled by compression
Severe renal insufficiency	Pre-existing neurological disease needs to be documented well and assess risk/benefit ratio
Difficult airway such as in elderly with cervical disk injury/pathology	Hypovolemia and severe aortic stenosis are relative contraindications for neuroaxial blocks, but not for PNBs
Chronic pain patients	Concern that PNB may mask compartment syndrome (controversial), however, collaboration between anesthesiologist and surgeon is necessary
Multiple rib fractures	Allergy to local anesthetics (rare)

PNB: Percutaneous needle biopsy.

Table 3 Nervous system changes in the elderly[11,13-15]

Structural changes: gross and molecular level	Neuronal axon loss and pathology (more than seen with glial cells)
	Neural cytoskeleton changes resulting in neurofibrillary tangles and neuritic plaques (induces glial cell-mediated inflammation)
	Loss of dendrite components and decrease in neural synaptic activity
	Amyloidoses due to amyloid protein accumulation
Biochemical changes	Neurotransmitter imbalance: mostly involves changes in serotonin, dopamine, norepinephrine, acetylcholine
	Circulatory changes: multi-infarct senile dementia; increased BBB permeability
	Metabolic disturbances: atherosclerosis and associated blood flow and O2 consumption decreases
Functional sequelae	Gait changes
	Sleep and wakefulness alterations and EEG changes
	Cognitive impairment
	Decreased balance stability/physical equilibrium

BBB: Blood-brain barrier; EEG: Electroencephalograph.

Table 4 Types of cognitive dysfunction

MCI (4 subtypes associated with causes of dementia)	Concept to describe transitional level of neurocognitive impairment
	MCI is a predictor of future dementia
	Diagnosis by neuropsychological testing and clinical observation
	Divided into 4 subtypes (based on presence of: (1) memory impairment plus; (2) number of other cognitive domains affected)
	Preoperative MCI may result in postoperative delirium
Delirium	Fluctuating consciousness, develops over hour to days
	Altered perception and cognition (not associated with dementia)
	In hospital predictors of delirium include:
	Bladder catheters
	↓ Functional status
	Male gender
	Malnutrition
	Infection
	Depression
	3 or more medications
	H2 antagonists
	Age
	Opioids
	Iatrogenic events
	Benzodiazepines
	Alcohol + drug abuse
POD[74]	Develops on postoperative day 1-3, can be sustained > 1 wk
	Age associated central cholinergic deficiency as a positive predictor
	Two types of postoperative delirium:
	Hypoactive form (more common and more commonly overlooked)
	Hyperactive type
	Perioperative use of benzodiazepines are associated with POD
	Postoperative in-dwelling perineural catheters reduce incidence of POD
Emergence Delirium	Present upon regaining consciousness following general anesthesia
	Predicts postoperative delirium
POCD	Condition in which patients have difficulty in performing cognitive tasks following surgery that they could perform prior to surgery
	Occurs frequently in and following: carotid endarterectomy, hip fracture repair surgery and cardiac surgery patients (most frequent)
	ISPOCD: developed criteria of POCD based on pre- and post-operative neuropsychological testing scores
	Predictors of POCD 1 wk postoperatively include:
	Duration of anesthesisa
	Age (predictor of POCD at 3 mo)
	Postoperative infection
	Low level of patient education
	Pulmonary complications
	Need for a second operation
Dementia Alzheimer’s disease (most common form), vascular dementias, frontal lobe, reversible, senile, Lewy body, and Parkinson-associated	Apathy and personality changes occur early
	Behavioral changes appear as the condition progresses
	Psychotic symptoms are late signs (typically difficult to control)
	Multiple cognitive deficits
	Clinical findings are associated with:
	Problems with social activities
	Decline from a previous status
	Problems of occupational activities
	Gradual and progressive loss of mental abilities
	Dementia often results in postoperative delirium

POCD: Postoperative cognitive dysfunction; ISPOCD: International study of postoperative cognitive dysfunction; MCI: Mild cognitive impairment; POD: Postoperative delirium.

Table 5 Cardiovascular changes associated with the aging process[12]

Cardiac changes	Coronary artery disease due to atherosclerosis
	Changes in CNS innervations of the cardiovascular system: increase in sympathetic and decrease in parasympathetic activity
	Diminished response to beta-receptor stimulation
	Increase in apoptosis resulting in muscle mass loss, compensatory hyperplagia of remaining cells, abnormal cardiac function that can eventually lead to diastolic and systolic heart failure
	Increase in microtubule component of cytoskeleton of cardiocytes results in contraction dysfunction
Vascular system changes	Decreased blood flow due to increased cell adherence, micro-thrombogenic events, atherosclerosis
	Increased vasoconstriction and vascular wall stiffening
	Impaired endothelium integrity and ability to repair

CNS: Central nervous system.

Table 6 Pulmonary changes and the elderly patient[6]

Structural aging	Increase of lung parenchymal compliance due to degeneration of elastic fibers
	Loss of respiratory muscle mass resulting in less endurance and less respiratory reserve
	Increased alveolar permeability, which results in bronchial fluid with increased neurophils and increased ratio of CD4/CD8 cells
	Decreased surface area for oxygen exchange
Functional aging	Chest wall rigidity
	Reduced maximum breathing capacity
	A greater in difference between alvelolar and arterial oxygen concentration
	Increase in closing capacity
	Less effective coughing
	Impaired swallowing with high risk of aspiration pneumonia