Perhaps the most well-evaluated aspect of normal aging is the aging of the cardiovascular system. Conceptually, Lakkata and colleagues have determined that the primary alteration of the aging cardiovascular system is a decrease in the elasticity of the large vessels, specifically the aorta [4, 5]. The aorta expands slightly with every ejection during cardiac systole. The elasticity allows this expansion and absorbs some of the kinetic energy of systole. During diastole, the aorta returns to its normal size, transferring the kinetic energy back to the column of flowing blood. This action has been referred to as the Windkessel function of the aorta by German physiologists in the 1800s. Assuming a heart rate of 70 bpm, the aorta expands and contracts approximately 36.8 million times per year or 2.58 × 10⁹ times in 70 years. Over the course of years, the elastic properties of the aorta deteriorate. This is frequently noted as calcification, enlargement, and uncoiling of the aorta on chest radiographs. The transition has two major effects (Fig. 2.4). The first is that the left ventricle experiences an increase in afterload as it is ejecting blood into a stiffer conduit. In addition, there is a reflected wave that adds to pressure in the aortic root [4]. Much as an expanding ring of waves in a still pond is reflected back when the wave impacts a solid object, arterial flow encounters multiple bifurcations of the arterial tree and each creates a reflected wave that is transmitted retrograde to the aortic root. In a young and elastic arterial system, this reflected wave arrives during diastole, increasing diastolic pressure. In the elderly, the entire arterial tree is more rigid, and the reflected wave travels significantly faster, arriving while systole is still in progress. This reflected wave adds additional pressure to systole, further increasing the afterload. A significant increase in systolic pressure is easily noted when the aorta is catheterized during percutaneous coronary interventions, where systolic pressures in excess of 250 mmHg are common. Over time, these deteriorations result in concentric hypertrophy of the left ventricle. Even healthy elderly patients manifest a degree of left ventricular hypertrophy. Due to the strain of the left ventricle, the ability to increase cardiac output through increase in stroke volume is limited, i.e., there is a decrease in the reserve function.

The chronotropic capacity of the heart also decreases. Maximum heart rate decreases – so the ability to increase cardiac output through chronotropic means is limited. Various formulas have been used to predict maximum heart rate. The long-standing equation of 220-age has been found to have little basis.² Perhaps the best currently available is
which provides a general estimate but, as noted above, does not define any specific patient [13]. The cardiac output of a normally aging individual at rest is essentially normal and adequate for most activities. The combination of muscular change in the ventricle and a limited ability to increase heart rate results in a clinical situation in which the left ventricle is very sensitive to end-diastolic volume. Thus, while cardiac output at rest is normal, the ability to increase cardiac output in response to stress is limited. For the patient with no other cardiovascular disease that might alter the approach, the anesthesiologist is advised to pay additional attention to volume replacement and appreciate that increase in heart rate is both limited as a compensatory mechanism and unlikely to have the same physiologically impact that would be seen in a younger patient [14]. Therefore, adjusting fluid administration to give adequate but not excess volume may require additional monitoring.

Coronary artery disease is so common in the elderly that many anesthesiologists strive to avoid high heart rates in all elderly patients. Many patients are maintained on beta blockers; however, adequate blockade for surgery is not assured and should not be assumed by the anesthesiologist. In recent years, the identification of diastolic heart failure [15] in elderly patients has supported this idea, providing adequate time during each cardiac cycle for relaxation of the ventricle. This leaves the clinical anesthesiologist managing the Starling forces of the left ventricle to maintain adequate cardiac output during a procedure. Adequate but not excessive intravenous fluid is typically managed by clinical assessment, including an assessment of pulse pressure variation or the use of a noninvasive monitor of stroke volume. However, when maintenance of normal physiology is challenging, early resort to investigations such as echocardiography can provide vital information regarding the function of the elderly heart such as ventricular filling status and contractile function.

Pulmonary function gradually changes in the elderly [16]. Even patients with serious exercise regimens manifest some decrease in aerobic capacity. Chest wall compliance and static elastic recoil decrease with aging [17]. There is some decrease in the strength of respiratory muscles [18]. The response to hypercapnia and hypoxia are less robust than in younger patients. The ability to increase respiration significantly in response to a challenge is markedly limited; however, resting respiratory capacity is generally adequate in most elderly patients. Breathing patterns of elderly patients frequently involve smaller tidal volumes and slight increases in respiratory rate. Recalling that individual variation is quite high, the anesthesiologist can estimate the PaO₂ of an elderly patient with the following equation [19]:

This equation indicates a significant relationship between PaO₂ and alterations of the body mass index (BMI) and PaCO₂ that occur from approximately 40 years of age until the mid-70s. PaO₂ remains relatively stable around 83 mmHg after age 75. For patients with a normal BMI and PaCO₂, this formula can be simplified to

Closing capacity nears functional residual capacity in the elderly [20]. Denitrogenation (preoxygenation) typically takes longer than for a younger patient, and desaturation following discontinuation of ventilation happens with some speed. Although the elderly have a decreased functional residual capacity, rapid desaturation following apnea is thought to be a result of an increased shunt fraction [21]. Thus, it is important to thoroughly denitrogenate an elderly patient before beginning laryngoscopy to avoid the rapid development of hypoxia. Achieving this state almost always requires more than four vital capacity breaths.

Respiratory complications account for approximately 40% of the perioperative deaths in patients over 65 years of age [12]. Elderly patients may manifest a decreased ability to clear secretions and therefore have an increased susceptibility to aspiration secondary to deterioration of protective coughing and swallowing mechanisms [21]. The basis for a decrease in upper-airway reflexes has been postulated to result from an age-related peripheral deafferentation along with a general decrease in central nervous system reflex activity. The clinical conundrum for the anesthesiologist is when to extubate a patient emerging from general anesthesia. Elderly patients tend to emerge from general anesthesia more slowly and purposeful reactions to verbal stimuli may be delayed, bearing in mind that they may also have preexisting hearing impairment. The tendency to remove an endotracheal tube before full wakefulness has to be tempered by concerns regarding upper-airway reflexes. Extubation in a slightly upright rather than supine position may be helpful, although no data exists to support such a practice. Oxygen supplementation following the end of general anesthesia is a good practice.

Much like other functions, alteration of renal function is highly variable. On average, renal function, as measured by glomerular filtration rate (GFR), decreases by over 50% by 80 years of age [22]. Creatinine levels are relatively normal; however, this is thought to represent a combination of a decreased GFR and a decrease in creatinine associated with a decrease in muscle mass. However, if one looks at the original data used to create this formula, some patients had significantly larger decreases in GFR and some were almost normal. The GFR measures that frequently accompany standard laboratory blood tests are calculated, not measured, and therefore associated with the same limitations as described for the equations above. An accurate assessment of renal function requires an assessment of GFR. For most procedures requiring anesthesia, the impact of a decreased GFR is limited. It is probably best to consider the possibility of decreased renal function in the elderly, but not to assume that is the case. Many intravenous anesthetic agents have some dependence on renal clearance such that a significant alteration in GFR may prolong the effect of these medications (see section below on anesthetic management). When intravenous agents are to be used in long cases, an actual measure of GFR by means of a timed urine collection may help in adjusting infusion rates.

Sarcopenia, the loss of muscle mass, occurs in all aging individuals even in the face of significant exercise. However, this loss of muscle, while notable, should not rise to the level of functional limitation. Significant sarcopenia is one of the hallmarks of frailty. This syndrome was extensively defined by Fried to include loss of muscle mass, weakness, weight loss, low exercise tolerance and energy, and low activity [6]. From a surgical perspective, frailty is thought to define a state of clinical vulnerability to stressors [7]. There is a lack of consensus on the actual definition of frailty and even some concern that frailty is not a distinct and definable syndrome, as opposed to just being a state of advanced aging.

Frailty, as measured in various ways, has been identified as an independent risk factor for major morbidity and mortality [7, 23]. The potential value of assessing frailty lies in the opportunity to assess risk and perhaps to adjust or mitigate that risk through preoperative interventions, such as preoperative exercises. A recent review of frailty in the surgical population explores many of the issues of frailty as a useful concept in the perioperative period [24]. Although it is difficult to ascribe a specific role to the assessment of frailty at the moment, it is highly likely that some type of measure will become a standard part of an assessment of elderly patients.

The elderly can be difficult to position due to limitations of movement in various joints or pain syndromes associated with arthritic entities. Joint replacements or fixations may also limit movement. The surgical team should attempt to determine the limitations of movement, particularly for artificial joints, before a patient is anesthetized. Although under anesthesia it may be possible to move a joint in a way that would not be possible in the absence of anesthesia, there is a high likelihood that such manipulation will result in significant postoperative pain for the patient. Therefore, when joint limitations are identified, it is best to position the patient on the operating table, if possible, before the initiation of anesthesia.

Elderly patients have a high potential for skin breakdown and the development of pressure or decubitus ulcers due to a loss of elasticity of tissue, diminution of collagen content of the skin. These complications can even occur following prolonged operations. Attention to minimizing pressure points and additional padding may help to prevent early tissue breakdown.