Anesthesia, an indispensable practice for eliminating pain during surgical operations, plays a key role in variations in blood pressure. This vital parameter of cardiovascular health can experience significant fluctuations under anesthesia, directly impacting clinical risks.

It is essential to monitor the effects of anesthesia on blood pressure, especially as strong variations can lead to serious complications such as hypotension or, more rarely, hypertension. These consequences are particularly important under general or locoregional anesthesia.

Patients should be informed of the potential effects on their blood pressure. Associated management is essential to ensure adequate management and reduce risks.

Understanding blood pressure and anesthesia

What is blood pressure?

Blood pressure, also known as arterial pressure, quantifies the force that blood exerts against the walls of the arteries. This force is essential for maintaining blood circulation throughout the body, ensuring the supply of oxygen and nutrients to each cell. Blood pressure is broken down into two measurements: systolic pressure, when the left ventricle of the heart contracts, and diastolic pressure, when the heart is at rest between beats.

The role of anesthesia in pain management

Anesthesia is central to pain management before, during, and after surgical procedures. Anesthesiologists, experts in this medical discipline, develop and administer the type of anesthesia best suited to each situation.

They employ different methods such as local anesthesia, conscious sedation, regional anesthesia, and general anesthesia to ensure patient comfort and reduce their pain and anxiety throughout the procedure. Regional anesthesia, for example, involves injecting a local anesthetic around the targeted nerves, causing a temporary loss of movement and pain sensation. General anesthesia, on the other hand, causes a state of total unconsciousness, allowing the patient to undergo surgery without pain.

Anesthesiologists also take care of postoperative pain control, adapting analgesic treatments to the specific needs of each patient.

Effects of anesthesia on blood pressure

Decreased blood pressure under anesthesia

Just as spinal anesthesia affects our perception of pain, anesthesia, particularlygeneral anesthesia, is responsible for a marked drop in blood pressure. Clinically termedarterial hypotension, this condition results from a variety of mechanisms. Anesthetic agents promote relaxation of vascular smooth muscle, leading to significant vasodilation and, consequently, a reduction in blood pressure.

Moreover, general anesthesia increases venous compliance and decreases effective circulating blood volume, thus reducing venous return to the heart - all factors that contribute to this arterial hypotension. In some contexts, the induction of hypotension is even desired (deliberate hypotension) in order to limit bleeding and improve operative visibility.

However, the application of this method is not without risks, as it can promote the appearance of cerebral lesions, thromboses, or cerebral ischemia, especially if the mean arterial pressure (MAP) falls below critical thresholds, often established between 60 and 70 mmHg.

Factors influencing blood pressure changes

The variability of blood pressure under anesthesia depends on several factors. Anesthetic substances, such as propofol, can have various effects on blood pressure. Propofol, for example, is likely to cause hypotension due to its vasorelaxant action and its ability to decrease cardiac output.

Patient configuration during the operation is also a critical parameter. The half-seated position can lead to a drop in arterial pressure due to the effect of gravity on venous return and intracranial pressure. In these conditions, it is vital to maintain sufficient arterial pressure to prevent brain damage and ensure adequate cerebral perfusion.

Neuroendocrine reactions to anesthesia and nociceptive stimuli during and after surgery can also affect blood pressure. In hypertensive patients, the combined effect of these factors can lead to significant blood pressure fluctuations, increasing the risk of cardiovascular complications during and after the operation. Furthermore, the duration of arterial hypotension proves to be a determining criterion.

Research shows that arterial hypotension, even of short duration, can be linked to acute renal and cardiac damage, while prolonged hypotension significantly increases the risk of postoperative mortality at 30 days.

Management and clinical implications

Monitoring blood pressure during anesthesia

The monitoring of blood pressure is an important measure integrated into the standards of care in anesthesia. This continuous monitoring is essential for detecting and rapidly managing blood pressure variations that may occur during anesthesia.

Anesthesiologists should use standard monitoring equipment, such as invasive or non-invasive blood pressure monitors, to track the patient's hemodynamic parameters in real time. The frequency of monitoring varies depending on the patient's risk and the complexity of the procedure.

For high-risk patients, particularly those classified as ASA 3 or higher, continuous and meticulous monitoring is necessary. This includes regular verification of blood pressure, cardiac output, oxygen saturation, and other vital parameters.

Strategies for minimizing risk

To minimize the risks associated with blood pressure variations during anesthesia, several strategies are implemented. Preparation and planning are essential; this includes checking the anesthesia and monitoring equipment before each procedure, as well as ensuring that the team is well-coordinated and familiar with emergency protocols. The use of checklists and standardized protocols helps to reduce medical errors and improve team efficiency.

For example, regular monitoring of the patient's health status, every 5 minutes for healthy patients and continuously for at-risk patients, is a recommended practice. In addition, proactive management of antihypertensive treatments and anesthetic agents is essential.

Anesthesiologists must be prepared to adjust the doses and types of anesthetics according to the patient's hemodynamic responses, and to use vasoactive agents such as adrenaline to correct episodes of arterial hypotension.

Implications for patients with hypertension

Patients with chronic hypertension present particular challenges in the perioperative period. Hypertension can increase the risk of cardiovascular complications, such as hypertensive episodes, episodes of myocardial ischemia, and congestive heart failure, due to reduced adaptation to volemic variations and increased sensitivity to nociceptive stimuli. It is essential to properly assess the state of hypertension before surgery.

This includes determining the persistence and balance of hypertension, as well as adjusting antihypertensive treatments if necessary. Anesthesiologists must also be prepared to manage perioperative blood pressure variations, using strategies to maintain blood pressure within acceptable limits and prevent cardiovascular complications.

Optimization of care before, during, and after anesthesia

Preoperative assessment and medication adjustments

Preoperative assessment is an essential pillar in optimizing patient treatment before anesthesia. This rigorous step revolves around a thorough examination of the patient's health, including their chronic treatments and the use of medical devices. It is essential to preserve the continuity of the patient's usual treatments as far as possible, to prevent pathological imbalances, rebound effects, and withdrawal syndromes.

The anesthesia team is responsible for weighing the pros and cons of interrupting, replacing, or continuing each medication. Beta-blockers and calcium channel blockers, for example, should generally be maintained unless there is a specific contraindication, in order to maintain the patient's hemodynamic stability. Similarly, special attention is required for patients on anticoagulants or antiplatelet agents.

The discontinuation of these medications should be strategically planned based on the nature of the surgery and the risk of thromboembolism or hemorrhage, and their resumption organized as soon as possible after the operation.

Intraoperative management

Intraoperative management plays a determining role in the safety and effectiveness of anesthesia during surgery. It includes optimizing volemia, meticulous monitoring of hemodynamics, and adjusting anesthetic agents according to the patient's specific reactions.

Advanced technological solutions, such as those offered by the Diane Consult and Diane Op ecosystem, contribute significantly to improving this management. These tools offer customization of anesthesia protocols, real-time monitoring of vital parameters, and adaptive medication management, thus facilitating the responsiveness and precision of treatment.

Smooth communication between care teams and traceability of interventions are essential. Integrated monitoring and documentation systems facilitate the coordination of interventions and ensure irreproachable continuity of care.

Postoperative monitoring and resumption of usual medication

Postoperative monitoring is a crucial phase for a safe and rapid patient recovery. It is imperative for anesthesiologists to closely monitor vital parameters, such as blood pressure, heart rate, and oxygen saturation, in order to detect any potential complications as early as possible.

The resumption of the patient's usual medications must be meticulously organized. It is essential to reinstate chronic treatments as soon as possible after the procedure, taking into account the resumption of the oral route and the objectives of care.

If the oral route is not possible, parenteral alternatives should be considered, as for treatments with beta-blockers or calcium channel blockers. In addition, patients should be assessed for potential risk of withdrawal syndrome or rebound effect following temporary cessation of their medication. Precise planning and coordination with postoperative care teams are key to ensuring a smooth transition and optimal patient recovery.

Conclusion

In summary, managing the effects of anesthesia on blood pressure requires constant vigilance to ensure patient safety and comfort. Continuous monitoring of blood pressure, coupled with a thorough preoperative assessment and judicious medication adjustments, is essential to mitigate the risks associated with potential hypotension or hypertension.

It is imperative that patients, especially those with hypertension, receive accurate information and are well prepared before, during, and after the anesthesia procedure. Strict adherence to standardized protocols and maintenance of fluid and effective communication between care teams are essential for optimal management.

By adopting such strategies, it is possible to significantly reduce complications and promote a safe and rapid recovery.

FAQ

What are the main factors influencing blood pressure during general anesthesia?

The main factors that influence blood pressure during general anesthesia include the effects of anesthetic agents, neuroendocrine responses to narcosis, and nociceptive stimuli during and after surgery. Anesthesia can decrease blood pressure, particularly by reducing blood pressure regulation mechanisms. In addition, the patient's position, such as the semi-seated position, and the use of vasopressors or fluids to counteract hypotension are also important.

In hypertensive patients, these factors can amplify variations in blood pressure, increasing cardiovascular risk.

How can perioperative hypotension affect patient morbidity and mortality?

Perioperative arterial hypotension can significantly affect patient morbidity and mortality in several ways. It is associated with an increase in postoperative complications, particularly cardiovascular, renal, and cerebral complications. Deep and prolonged hypotension increases the risk of acute renal failure, ischemic myocardial and cerebral lesions, and is linked to increased mortality at 30 days and 1 year postoperatively.

Arterial hypotension, particularly when mean arterial pressure (MAP) is below 80 mmHg for more than 10 minutes, exacerbates organ damage and increases the frequency of complications. In hypertensive patients, the risk is even higher due to their lower blood pressure threshold.

What are the physiological mechanisms involved in the decrease in tone of the capacitive system under the effect of anesthesia?

During anesthesia, the decrease in tone of the capacitance system (venous system) is mainly due to the activation of the sympathetic system and the renin-angiotensin-aldosterone system (RAAS). The decrease in blood pressure and venous return secondary to relative or true hypovolemia stimulates baroreceptors, which increases peripheral sympathetic activity.

This sympathetic activation leads to venous vasoconstriction, thus mobilizing the capacitive venous system to increase venous return and cardiac output.

What strategies do anesthetists use to correct and prevent arterial hypotension during surgical procedures?

Anesthesiologists use several strategies to correct and prevent arterial hypotension during surgical procedures. They start with systematic monitoring of blood pressure and individualization of blood pressure targets based on patient risk and surgical risk.

For low-risk patients, a mean arterial pressure (MAP) of 60 mmHg may be sufficient, while for high-risk patients, a MAP of 80 mmHg or a maximum variation of 10 to 20% from the baseline value is recommended. They first rule out an overdose of hypnotic agents, then correct cardiac output by adjusting stroke volume and heart rate. In case of a decrease in systemic vascular resistance, they introduce vasopressor treatment, favoring noradrenaline and ephedrine, often administered as a continuous infusion to maintain stable blood pressure.