Total Intravenous Anesthesia - Indications and Advantages

Introduction:

Total intravenous anesthesia provides general anesthesia (GA) through intravenous agents (TIVA). Because of the pharmacokinetic and pharmacodynamic properties of Propofol, as well as the availability of short-acting synthetic opioids, TIVA has gained popularity over the last 20 years. The use of TIVA to retain general anesthesia has a variety of theoretical benefits over inhalational agents. Drugs used for TIVA reduce the risk of general anesthesia side effects such as postoperative nausea and vomiting (PONV) and help avoid environmental pollution due to inhalational agents. Regarding these and other potential benefits, TIVA usage remains relatively low. Concerns about the increased probability of patient awareness of TIVA versus inhalational agents with end-tidal agent concentration monitoring have been expressed. TIVA is highly successful in inducing a deep plane of anesthesia. As a result, this method should be used with caution in patients who are compromised by the aging population or poor American society of anesthesiologist status. However, it still provides a benefit in terms of recovery profile.

What Are the Advantages of TIVA?

• The onset of nausea and vomiting after surgery is drastically decreased.

• There is decreased inhalational gas pollution in the operating room, and the greenhouse effect is significantly lowered ultimately.

• TIVA improves hemodynamic stability.

• The hypoxic pulmonary vasoconstriction remains.

• There is a decrease in intracranial pressure.

• Ultimately, there is a lower risk of toxicity of organs, as demonstrated by Halothane, which has a possibility of liver damage, and Sevoflurane at the flow rate, which has a chance for deterioration of the kidney function.

What Are the Specific Indications of TIVA?

• Patients at potential danger of malignant hyperthermia.

• Patients at risk of malignant hyperthermia.

• Patients with prolonged QT (a wave in electrocardiogram) syndrome.

• Patients undergoing ENT (ear, nose, and throat) and thoracic surgery, especially for ‘tubeless’ procedures.

• Patients with previous episodes of postoperative nausea and vomiting.

• Patients with previously expected difficult intubation or extubation.

• To restrict intracranial volume in neurosurgery cases.

• Surgery involving neurophysiological monitoring.

• Myasthenia gravis or neuromuscular abnormalities and conditions where neuromuscular agents are prevented.

• Remote location anesthesia.

• There is a need for shifting regular patients between environments.

• Daycare surgical intervention.

• Patient preference.

What Are the Properties of an Ideal Anesthetic Agent?

• An ideal anesthetic agent includes the following characteristics: sudden onset and offset; fast emergence; quick recovery to baseline; analgesia at subanesthetic concentrations; antiemetic effect; very little respiratory and cardiovascular depression; lack of active metabolites; independent organ metabolism; easily titratable; no connection with neuromuscular blocking drugs; no harmful effects on other organs; antioxidant, anti-inflammasomes, no allergic reactions, histamine release,

• None of the agents presently available fulfill all of these criteria. On the other hand, TIVA with Propofol has various potential benefits over inhalational agents.

Goals of TIVA

• Smooth induction.

• Reliable and titratable anesthesia maintenance.

• Rapid emergence from the effects of the infused drug once the infusion is stopped.

What Are the Drugs Used for TIVA?

• Hypnotics such as Propofol, Ketamine, Benzodiazepines, Etomidate, and Barbiturates.

• Analgesics such as Fentanyl, Remifentanyl, Sufentanil, and Alfentanyl.

• Muscle relaxants such as Atracurium and Vecuronium.

What Are Targeted Controlled Infusions?

• A microprocessor in a targeted controlled infusions (TCI) pump is programmed with pharmacokinetic models for appropriate drugs.

• The anesthetist chooses the drug and pharmacokinetic model that will be implemented by the targeted controlled infusions (TCI) pump and enters patient variables (covariates) such as the age of the patient and the body weight, as well as the target plasma or 'brain' (effect-site) concentration, with the pump deciding on the initial bolus and subsequent infusion rates.

• Marsh and Schnider are the two most frequently used adult Propofol models.

What Are Manual Infusions?

• When administering TIVA manually (without the assistance of a TCI pump), a complete analysis of the pharmacokinetics of the drugs is required.

• Based on the prior administration rate and infusion duration, a fixed infusion rate may result in rising, declining, or stable concentrations, posing the risk of inadequate- or excessive drug dosage.

• Even when utilizing drugs with the fastest pharmacokinetic profiles, a simple change in infusion rate results in a significant delay before plasma concentrations alter noticeably. This lag is even more pronounced in the case of effect-site concentrations and clinical effects.

• When a Propofol infusion is started at a fixed rate without the need for an initial bolus, concentrations rise very slowly and reach near steady-state levels but after many hours.

• If no loading dose is ingested, administration through a fixed infusion rate will result in insufficient concentrations.

• However, the concentrations may reach elevated levels at a constant infusion rate. Similarly, lowering the infusion rate causes a slow alteration in plasma concentrations.

• On the other hand, Remifentanil reaches approximately 75 percent of steady-state concentration after five minutes, with 100 percent achieved after fifteen to twenty minutes.

How Is Infusion Started?

• The situation becomes less clear when an effect-targeting Propofol model is combined with Remifentanil in a plasma-targeted fashion.

• If the drugs are initiated simultaneously, the Propofol effect-site concentration will rise much faster than the Remifentanil effect-site concentration, making functional synergy of action challenging to achieve soon.

• Another alternative is to begin the Remifentanil first and allow for equilibration at the effect site before starting the Propofol.

• Because anesthesia is accomplished at relatively low Propofol effect-site concentrations, successive induction is accelerated. As a result, apnea is a severe risk, and effective pre-oxygenation must be supplemented by patient reminders to breathe deeply.

• When both plasma-targeted infusions are initiated simultaneously, Remifentanil begins at the effect site much faster than Propofol. Therefore, unless the Propofol target is considerably 'over-pressured,' this can lead to an apnoeic but potentially aware patient.

• This latter method is analogous to an extensive manual bolus, with the possibility of undesirable cardiovascular effects. Therefore, permitting Remifentanil to begin at the effect site before starting Propofol administration is a helpful method.

How Is the Patient Monitored during TIVA?

Propofol plasma concentrations cannot currently be assessed minute by minute practically. Clinical calculation of the individual patient even before "knife-to-skin" can be accomplished by mentioning increments in effect-site concentrations that show:

• Lack of response to shaking and shouting;

• Loss of hemodynamic responses or movement of the limb with forceful jaw thrusting.

• Absence of an increase in the heart rate or even decrease in the heart rate with laryngoscopy and intubation.

Conclusion:

For the prevention of postoperative nausea and vomiting, TIVA is superior to inhalational anesthesia and should be used as part of a multimodal treatment plan in all high-risk individuals with postoperative nausea and vomiting. The data on anesthesia recovery and TIVA are mixed, and TIVA does not seem to produce a substantial improvement in wakeup. The opioid used is possibly more crucial than the type of anesthesia used, with Remifentanil allowing for a faster comeback to consciousness. A significant risk of awareness is likely due to a lack of knowledge and training in this technique. Targeted controlled infusions use of Propofol and Remifentanil, as well as sticking to simple guidelines, will eliminate most of this risk.