Peripheral blood flow in the elderly during inhalational anaesthesia

Profile of sugammadex for reversal of neuromuscular blockade in the elderly: current perspectives

The number of elderly patients is increasing worldwide. This will have a significant impact on the practice of anesthesia in future decades. Anesthesiologists must provide care for an increasing number of elderly patients, who have an elevated risk of perioperative morbidity and mortality. Complications related to postoperative residual neuromuscular blockade, such as muscle weakness, airway obstruction, hypoxemia, atelectasis, pneumonia, and acute respiratory failure, are more frequent in older than in younger patients. Therefore, neuromuscular blockade in the elderly should be carefully monitored and completely reversed before awakening patients at the end of anesthesia. Acetylcholinesterase inhibitors are traditionally used for reversal of neuromuscular blockade. Although the risk of residual neuromuscular blockade is reduced by reversal with neostigmine, it continues to complicate the postoperative course. Sugammadex represents an innovative approach to reversal of neuromuscular blockade induced by aminosteroid neuromuscular-blocking agents, particularly rocuronium, with useful applications in clinical practice. However, aging is associated with certain changes in the pharmacokinetics of sugammadex, and to date there has been no thorough evaluation of the use of sugammadex in elderly patients. The aim of this review was to perform an analysis of the use of sugammadex in older adults based on the current literature. Major issues surrounding the physiologic and pharmacologic effects of aging in elderly patients and how these may impact the routine use of sugammadex in elderly patients are discussed.

The effect of age on the response of retinal capillary filling to changes in intraocular pressure measured by optical coherence tomography angiography

PURPOSE

To compare the effect of elevated intraocular pressure (IOP) on retinal capillary filling in elderly vs adult rats using optical coherence tomography angiography (OCTA).

METHODS

The IOP of elderly (24-month-old, N=12) and adult (6-8month-old, N=10) Brown Norway rats was elevated in 10mmHg increments from 10 to 100mmHg. At each IOP level, 3D OCT data were captured using an optical microangiography (OMAG) scanning protocol and then post-processed to obtain both structural and vascular images. Mean arterial blood pressure (MAP), respiratory rate, pulse and blood oxygen saturation were monitored non-invasively throughout each experiment. Ocular perfusion pressure (OPP) was calculated as the difference between MAP for each animal and IOP at each level. The capillary filling index (CFI), defined as the ratio of area occupied by functional capillary vessels to the total scan area but excluding relatively large vessels of >30μm, was calculated at each IOP level and analyzed using the OCTA angiograms. Relative CFI vs IOP was plotted for the group means. CFI vs OPP was plotted for every animal in each group and data from all animals were combined in a CFI vs OPP scatter plot comparing the two groups.

RESULTS

The MAP in adult animals was 108±5mmHg (mean±SD), whereas this value in the elderly was 99±5mmHg. All other physiologic parameters for both age groups were uniform and stable. In elderly animals, significant reduction of the CFI was first noted at IOP 40mmHg, as opposed to 60mmHg in adult animals. Individual assessment of CFI as a function of OPP for adult animals revealed a consistent plateau until OPP reached between 40 and 60mmHg. Elderly individuals demonstrated greater variability, with many showing a beginning of gradual deterioration of CFI at an OPP as high as 80mmHg. Overall comparison of CFI vs OPP between the two groups was not statistically significant.

CONCLUSIONS

Compared to adults, some, but not all, elderly animals demonstrate a more rapid deterioration of CFI vs OPP. This suggests a reduced autoregulatory capacity that may contribute to increased glaucoma susceptibility in some older individuals. This variability must be considered when studying the relationship between IOP, ocular perfusion and glaucoma in elderly animal models.

Anesthesia, microcirculation, and wound repair in aging

Age-related changes in skin contribute to impaired wound healing after surgical procedures. Changes in skin with age include decline in thickness and composition, a decrease in the number of most cell types, and diminished microcirculation. The microcirculation provides tissue perfusion, fluid homeostasis, and delivery of oxygen and other nutrients. It also controls temperature and the inflammatory response. Surgical incisions cause further disruption of the microvasculature of aged skin. Perioperative management can be modified to minimize insults to aged tissues. Judicious use of fluids, maintenance of normal body temperature, pain control, and increased tissue oxygen tension are examples of adjustable variables that support the microcirculation. Anesthetic agents influence the microcirculation of a combination of effects on cardiac output, arterial pressure, and local microvascular changes. The authors examined the role of anesthetic management in optimizing the microcirculation and potentially improving postoperative wound repair in older persons.

The effects of age on maintenance of intense neuromuscular block with rocuronium

BACKGROUND

Increasing age is associated with a longer duration of action of neuromuscular block. The aim of this study was to determine the influence of ageing on the recovery of the post-tetanic count (PTC) from rocuronium-induced neuromuscular block.

METHODS

Twenty-two younger (20-60 years) and 22 older (> 70 years) patients were enrolled in this study. After induction of anaesthesia with fentanyl and propofol, all patients initially received 1 mg/kg rocuronium and neuromuscular block were evaluated by contractions of the adductor pollicis muscle to ulnar nerve train-of-four stimulation using an acceleromyograph. Subsequently, intense rocuronium-induced block was determined every 6 min using the PTC during 1.0-1.5% sevoflurane and remifentanil anaesthesia. When the first response to the PTC stimulus was detected, 0.2 mg/kg rocuronium was additionally administered, and again, spontaneous recovery of neuromuscular function was monitored until the first response to the PTC reappeared.

RESULTS

Median values (range) of the times from the administration of 1 mg/kg and 0.2 mg/kg rocuronium until recovery of the first detectable PTC were significantly longer in the older [51.0 (27-100) min, P < 0.0001 and 30.0 (12-66) min, P = 0.0036, respectively] than the younger patients [31.5 (21-45) min and 18.0 (12-36) min, respectively].

CONCLUSION

The times from rocuronium injection to reappearance of the first response to PTC stimulation are approximately twofold longer and more variable in older than younger patients. Hence, the dosing interval of rocuronium should be adjusted using neuromuscular monitoring when maintaining intense neuromuscular block, especially in older patients.

Reversibility of rocuronium-induced profound neuromuscular block with sugammadex in younger and older patients

BACKGROUND

This study compared the reversibility of rocuronium-induced profound neuromuscular block with sugammadex in younger and older patients.

METHODS

Fifteen younger (20-50 yr) and 15 older (≥70 yr) patients were sequentially enrolled in this study. After induction of anaesthesia and laryngeal mask insertion, contraction of the adductor pollicis muscle in response to ulnar nerve stimulation was quantified using acceleromyography during 1.0-1.5% end-tidal sevoflurane and remifentanil anaesthesia. All patients initially received rocuronium 1 mg kg(-1), followed by 0.02 mg kg(-1) when a post-tetanic count (PTC) of 1 or 2 was observed. After completion of surgery, at reappearance of 1-2 PTC, the time required for a single bolus dose of 4 mg kg(-1) sugammadex to produce recovery to a train-of-four (TOF) ratio of 0.9 was recorded.

RESULTS

There were no differences in the total dose of rocuronium administered between the younger [mean (sd): 93.4 (17.5) mg] and the older [97.5 (32.2) mg] groups. In all patients, adequate recovery of the TOF ratio to 0.9 was achieved after administration of sugammadex, although it was significantly slower in the older [3.6 (0.7) min, P<0.0001] than in the younger group [1.3 (0.3) min]. There were no clinical events attributable to recurarization.

CONCLUSIONS

Sugammadex can adequately restore neuromuscular function in older patients, although a longer time is required to recover from profound rocuronium-induced neuromuscular block than in younger patients.

Database for physiologically based pharmacokinetic (PBPK) modeling: physiological data for healthy and health-impaired elderly

Physiologically based pharmacokinetic (PBPK) models have increasingly been employed in chemical health risk assessments. By incorporating individual variability conferred by genetic polymorphisms, health conditions, and physiological changes during development and aging, PBPK models are ideal for predicting chemical disposition in various subpopulations of interest. In order to improve the parameterization of PBPK models for healthy and health-impaired elderly (herein defined as those aged 65 yr and older), physiological parameter values were obtained from the peer-reviewed literature, evaluated, and entered into a Microsoft ACCESS database. Database records include values for key age-specific model inputs such as ventilation rates, organ volumes and blood flows, glomerular filtration rates, and other clearance-related processes. In total, 528 publications were screened for relevant data, resulting in the inclusion of 155 publications comprising 1051 data records for healthy elderly adults and 115 data records for elderly with conditions such as diabetes, chronic obstructive pulmonary disease (COPD), obesity, heart disease, and renal disease. There are no consistent trends across parameters or their associated variance with age; the gross variance in body weight decreased with advancing age, whereas there was no change in variance for brain weight. The database contains some information to inform ethnic and gender differences in parameters; however, the majority of the published data pertain to Asian (mostly Japanese) and Caucasian males. As expected, the number of records tends to decrease with advancing age. In addition to a general lack of data for parameters in the elderly with various health conditions, there is also a dearth of information on blood and tissue composition in all elderly groups. Importantly, there are relatively few records for alveolar ventilation rate; therefore, the relationship between this parameter and cardiac output (usually assumed to be 1:1) in the elderly is not well informed by the database. Despite these limitations, the database represents a potentially useful resource for parameterizing PBPK models for the elderly to facilitate the prediction of dose metrics in older populations for application in risk assessment.

Study of venous blood flow changes during laparoscopic surgery using a thermodilution technique

BACKGROUND

Many modalities exist to analyse those factors that contribute to venous stasis and deep venous thrombosis (DVT) during laparoscopic surgery. To the authors' knowledge intraoperative measurement of femoral venous blood flow has not yet been performed nor has the influence of sequential compression devices been assessed using this parameter.

METHODS

The thermodilution technique similar to that employed in cardiac output measurement was used to determine changes in blood flow in the right femoral vein during laparoscopic cholecystectomy. Deep venous thrombosis prophylaxis involved perioperative use of sequential compression devices and subcutaneous heparin 5000 U.

RESULTS

Pneumoperitoneum and the Trendelenburg position reduced femoral venous return in four of the six patients studied, but sequential compression devices failed to return blood flow to baseline in a predictable fashion.

CONCLUSIONS

Although the measurement of blood flow using thermodilution is regarded as a reliable technique, during general anaesthesia the results may be susceptible to haemodynamic variations related to the anaesthetic agents as well as to the laparoscopic procedure. In addition sequential compression devices (when used alone) may not provide adequate prophylaxis against DVT because they do not predictably increase femoral blood flow.

Understanding spontaneous output fluctuations of an amperometric glucose sensor: effect of inhalation anesthesia and use of a nonenzyme containing electrode

Implantable glucose sensors are often unstable in vivo. Possible causes include local oscillations of glucose or oxygen levels, fluctuation of interferants, and external electromagnetic interference. To better understand glucose versus nonglucose mediated fluctuations, we compared sensors fabricated with glucose oxidase versus blank electrodes without enzyme in rabbits. We also investigated the effect of general anesthesia. We used power spectral analysis to investigate transmitted signals from amperometric peroxide sensing devices 2-3 weeks after subcutaneous implantation. Fasted animals were studied for 90 minutes in the conscious state and for 90 minutes during halothane anesthesia. Animals exhibited almost no body movement during the studies. In the conscious state, enzyme active sensors demonstrated more oscillations than blank electrodes at almost all frequencies from 2 to > 8 cycles per hour. This finding suggested that the spontaneous fluctuations were secondary to local changes in glucose or oxygen. Because fluctuations were not seen in the blank electrode, periodic changes in interferant concentrations, electromyographic activity, or in external electromagnetic interference are unlikely. General inhalation anesthesia was associated with markedly reduced sensor output fluctuation at almost all frequencies in enzyme active sensors. We conclude that fluctuation of electrochemical glucose sensor output, unrelated to fluctuations in blood glucose, is likely secondary to spontaneous changes in the local concentration or vascular delivery of glucose or oxygen. Anesthesia may have stabilized blood flow, preventing normal spontaneous autoregulatory variation.

Cardiovascular homeostasis during inhalational general anesthesia: a clinical comparison between sevoflurane and isoflurane. On behalf of the Italian Research Group on sevoflurane

STUDY OBJECTIVE

To obtain more information on cardiovascular homeostasis and patient discharge from the recovery area after general anesthesia with either sevoflurane or isoflurane as the main anesthetic.

DESIGN

Prospective, randomized, multicenter study.

SETTING

Inpatient anesthesia at 13 University Departments of Anesthesia.

PATIENTS

247 ASA physical status I, II, and III patients, aged 18 to 85 years, receiving general anesthesia for elective urological, orthopedic, ENT, vascular, and low abdominal surgery.

INTERVENTIONS

General anesthesia was maintained using a 60% nitrous oxide in oxygen mixture with either isoflurane (n = 125) or sevoflurane (n = 122) adjusted according to hemodynamic variables.

MEASUREMENTS AND MAIN RESULTS

Occurrence of hypotension [systolic arterial blood pressure (SBP) decrease >30% from baseline], hypertension (SBP increase >30% from baseline), bradycardia [heart rate (HR) <50 bpm], or tachycardia (HR>100 bpm) provoked stepwise changes in the inspired concentration of the study drug. If this action proved to be ineffective after an adequate stabilization period, a specific treatment was given, and the need for pharmacological treatment was recorded as a hemodynamic side effect by an independent observer. No differences in duration of anesthesia were observed between sevoflurane (126 +/- 76 min) and isoflurane patients (139 +/- 60 min). Mean duration from anesthetic discontinuation to fulfillment of discharge criteria was shorter after sevoflurane (21 min; 25(th) to 75(th) percentiles: 27 to 13 min) than isoflurane (27 min; 25(th) to 75(th) percentiles: 17 to 35 min) (p < 0.0005). Hemodynamic side effects requiring therapy occurred in 18 sevoflurane patients (14.6%) and 26 isoflurane patients (20.8%) (p = NS). The risk for hemodynamic side effects increased with age (>50 vs. < or OFFyrs: odds ratio 2.5; 95% CI 1.2 to 5.4; p = 0.015) and ASA physical status (III vs. I and II: odds ratio 2.2; 95% CI 0.9 to 5.7; p = 0.048). When only patients over 50 years of age were considered (72 in the sevoflurane group and 79 in the isoflurane group), the incidence of hemodynamic side effects was higher with isoflurane (29.1%) than with sevoflurane (15.2%) (odds ratio 2.3; 95% CI 1.0 to 5.2; p = 0.04).

CONCLUSIONS

Sevoflurane provided equally safe and effective control of cardiovascular homeostasis as isoflurane, with a more rapid discharge from the recovery area. Interestingly, patients over 50 years of age showed a lower risk for hemodynamic side effects when receiving sevoflurane than isoflurane.