Frequency of Intraoperative Hypotension After the Induction of Anesthesia in Hypertensive Patients with Preoperative Angiotensin-converting Enzyme Inhibitors

Population Pharmacokinetic Modelling of Norepinephrine in Healthy Volunteers Prior to and During General Anesthesia

BACKGROUND

Intraoperation hypotension (IOH) is commonly observed in patients undergoing surgery under general anesthesia, and even a brief episode of IOH can lead to unfavorable outcomes. To reduce the risk, blood pressure is closely measured during general anesthesia, and norepinephrine (NE) is frequently administered if hypotension is detected. Despite its routine application, information on the dose-exposure-response relationship of NE remains limited. Additionally, quantification of the influence of general anesthesia on the pharmacokinetics (PK) of NE is lacking.

OBJECTIVE

In this study, we aimed to describe NE PK in healthy volunteers and the influence of general anesthesia on its PK.

METHODS

A single-center, cross-over study was conducted in healthy volunteers. The volunteers received a step-up NE dosing scheme (0.04, 0.08, 0.12, 0.16 and 0.20 mcg-1/kg-1/min-1) first in the awake state and then under general anesthesia. General anesthesia was administered using a propofol/remifentanil Eleveld target-controlled infusion. During general anesthesia, a 30-second electrical stimulus was given as surrogate for surgical incision to the volunteers at each dosage step. Blood samples were drawn before the initial dosing and after each dosing step, and plasma NE, propofol and remifentanil concentrations were subsequently determined. A population PK model was developed using non-linear mixed effects modelling. Simulations were conducted to predict the plasma NE concentration in patients at different measured propofol concentrations.

RESULTS

A total of 1219 samples were analyzed from 36 volunteers. A two-compartment model with a first-order elimination best described the data. Weight, age, and session effect (awake vs general anesthesia) were identified as relevant covariates on the clearance (CL) of NE. A 10% decrease in NE CL was observed after general anesthesia induction. This difference between sessions is better explained by the measured concentration of propofol, rather than the anticipated impact of cardiac output. The estimated post-stimulation NE concentration is 0.66 nmol/L-1 (95% CI 0.06-1.20 nmol/L-1) lower than the pre-stimulation NE concentration. Model simulation indicates that patients at a higher measured propofol concentration (e.g., 6 mcg/mL-1) exhibited higher NE concentrations (95% PI 18.10-43.89 nmol/L-1) than patients at a lower measured propofol concentration (e.g., 3 mcg/mL-1) (95% PI 16.81-38.91 nmol L-1).

CONCLUSION

The NE PK is well described with a two-compartment model with a first-order elimination. NE CL exhibiting a 10% decrease under general anesthesia, with this difference being attributed to the measured concentration of propofol. The impact of stimulation on NE PK under general anesthesia is very limited.

CLINICAL TRIALS REGISTRATION NUMBER

NL9312.

Renal safety and survival among acutely ill hospitalized patients treated by blockers of the Renin-Angiotensin axis or loop diuretics: a single-center retrospective analysis

BACKGROUND

Concern exists regarding the renal safety of blocking the renin-angiotensin system (RAS) during acute illness, especially in the presence of volume depletion and hemodynamic instability.

METHODS

We explored the impact of loop diuretics and RAS blockers on the likelihood of developing acute kidney injury (AKI) or acute kidney functional recovery (AKR) among inpatients. Adjusted odds ratio for AKI, AKR and mortality was calculated, using logistic regression models, with subgroup analysis for patients with estimated glomerular filtration rate (eGFR) <30 ml/min/1.73 m2, corrected for blood pressure measurements.

RESULTS

53,289 patients were included. RAS blockade was associated with reduced adjusted odds ratio for both AKI (0.76, CI 0.70-0.83) AKR (0.55, 0.52-0.58), and mortality within 30 days (0.44, 0.41-0.48), whereas loop diuretics were associated with increased risk of AKI (3.75, 3.42-4.12) and mortality (1.71, 1.58-1.85) and reduced AKR (0.71, 0.66-0.75). Comparable impact of RAS blockers and loop diuretics on renal outcomes and death was found among 6,069 patients with eGFR < 30 ml/min/1.73m2. RAS inhibition and diuretics tended to increase the adjusted odds ratios for AKI and to reduce the likelihood of AKR in hypotensive patients.

CONCLUSIONS

Reduced blood pressure, RAS blockers and diuretics affect the odds of developing AKI or AKR among inpatients, suggesting possible disruption in renal functional reserve (RFR). As long as blood pressure is maintained, RAS inhibition seems to be safe and renoprotective in this population, irrespective of kidney function upon admission, and is associated with reduced mortality.

Systolic Blood Pressure Less Than 120 mmHg is a Safe and Effective Method to Minimize Bleeding After Facelift Surgery: A Review of 502 Consecutive Cases

BACKGROUND

Hematoma is the most common complication after facelift surgery. Hypertension is the major risk factor for hematoma following facelift. Measures taken to reduce systolic blood pressure perioperatively significantly reduce the risk of hematoma. There is evidence that treating systolic blood pressure of 140 mmHg or above reduces hematoma; there were no studies to date in which systolic blood pressures below 120 mmHg had been evaluated.

OBJECTIVES

To assess the safety and efficacy of maintaining systolic blood pressures of 120 mmHg or less postoperatively to reduce hematoma after facelift.

METHODS

A retrospective chart review of a single surgeon's series of facelift procedures from January 2004 to July 2018 was undertaken. Implementation of a more stringent perioperative blood pressure protocol (maintaining a systolic blood pressure of less than 120 mmHg postoperatively) was initiated in January of 2013, dividing patients into 2 groups.

RESULTS

A total of 502 consecutive patients who underwent a facelift by F.N. were included in the study. A total of 319 patients underwent a facelift before 2013, and a total of 183 patients underwent a facelift in 2013 or later. Overall, a total of 13 hematomas occurred during the entire 15-year study period (2.59%), of which 12 occurred before the implementation of a strict blood pressure regimen (3.76%), and only 1 occurred after the new protocol (0.5%). There were no adverse events related to the lower blood pressure.

CONCLUSIONS

Treating systolic blood pressure greater than 120 mmHg postoperatively is a safe and effective method for reducing the risk of hematoma after facelift.

Formaldehyde causes an increase in blood pressure by activating ACE/AT1R axis

Previous studies suggest some link between formaldehyde exposure and harmful cardiovascular effects. But whether exposure to formaldehyde can cause blood pressure to rise, and if so, what the underlying mechanism is, remains unclear. In this study, C57BL/6 male mice were exposed to 0.1, 0.5, 2.5 mg/m³ of gaseous formaldehyde for 4 h daily over a three-week period. The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP) and heart rate (HR) of the mice were measured by tail-cuff plethysmography, and any histopathological changes in the target organs of hypertension were investigated. The results showed that exposure to formaldehyde did cause a significant increase in blood pressure and heart rate, and resulted in varying degrees of damage to the heart, aortic vessels and kidneys. To explore the underlying mechanism, a specific inhibitor of angiotensin converting enzyme (ACE) was used to block the ACE/AT1R axis. We observed the levels of ACE and angiotensin II type 1 receptor (AT1R), as well as the bradykinin (BK) in cardiac cytoplasm. The data suggest that exposure to formaldehyde induced an increase in the expression of ACE and AT1R, and decreased the levels of BK. Strikingly, treatment with 5 mg/kg/d ACE inhibitor can attenuate the increase in blood pressure and the pathological changes caused by formaldehyde exposure. This result has improved our understanding of whether, and how, formaldehyde exposure affects the development of hypertension.

Angiotensin-converting enzyme inhibitor activity of peptides derived from Kacang goat skin collagen through thermolysin hydrolysis

Background and Aim:

Angiotensin-converting enzyme (ACE) is one of the inhibitory enzymes isolated from animals for the treatment of hypertension. ACE inhibitor (ACE-I) peptides can be obtained by hydrolyzing proteins from various animal tissues, including muscle and connective tissues. However, the study on ACE-I activity from collagen of Kacang goat skin has not been conducted. This study explores the potency of collagen from Kacang goat skin as a source of an antihypertensive agent through ACE inhibition. Thermolysin will hydrolyze collagen and produce the peptide classified antihypertensive bioactive peptides. This study aimed to determine the potential of thermolysin to hydrolyze collagen of Kacang goat skin for ACE-I peptide production and to identify the production of ACE-I peptides.

Materials and Methods:

Collagen from Kacang goat skin was hydrolyzed with thermolysin and incubated at 37°C for 1 h. Molecular weight (MW) evaluation was performed by SDS PAGE; fractionation peptides at <5 kDa, 3-5 kDa, and <3 kDa were performed by ultrafiltration and ACE-I activity determined by IC₅₀ measurement.

Results:

Collagen was hydrolyzed by thermolysin, resulting in protein with MW of 117.50-14.60 kDa. The protein content of fractionation at >5 kDa was 3.93±0.72 mg/mL, content of 3-5 kDa was 3.81±0.68 mg/mL, and that of <3 kDa was 2.33±0.38 mg/mL. Fractionation was performed 3 times and one of the results was selected for the ACE-I test. The selected fraction was tested by IC₅₀ measurement with three repetitions and it showed an average enzyme activity at 0.83 mg/mL or 82.94 mg/mL.

Conclusion:

Thermolysin hydrolysis of collagen from Kacang goat skin showed the potential to produce bioactive peptides, such as ACE-I.