Preoperative Medication: Sedative Hypnotics and Other Agents and Issues

Preoperative Medication

• ³Patient Assessment-Estimating the extent and basis of patient anxiety

  •  The extent of anxiety appears to be associated with the particular procedure being performed:

    • 85.7% of patients were about to undergo cancer surgery and 79% of patients about to undergo major genitourologic procedures report anxiety

    • 57.2% of patients undergoing other procedures report anxiety

  •  Patient presurgical concerns (ranked in order):

    1. Blindness

    2. Cancer diagnosis

    3. Loss of an organ

    4. Absence of a diagnosis

    5. Postoperative pain {the anesthesia provider, using a variety of techniques and medications, can minimize the unphysiologic condition of pain.

       1. The presence of postoperative pain may be a contributing factor for postoperative cardiovascular morbidity.

• Psychological factors to consider

  • Appropriate levels of fear-the anesthesia provider may help set the patient's expectations:

    • Postsurgical dissatisfaction may be related to unrealistic presurgical expectations, possibly due to inadequate or incomplete preoperative discussion with the patient concerning the procedure and possible outcomes

  •  Presurgical explanations should take into account the anxiety-state of the patient, i.e. a very anxious patient may have even further anxiety as a result of such discussions 

  •  Anesthesia providers may aid the patient in coping with preoperative anxiety by suggesting that patients focus their attention to other more pleasing or at least distracting activities

  •  Examples of effect of coping mechanisms which can be promoted by the anesthesia provider

    1. Helping the patient view themselves as part of rather than separate from the health-care providing team.

       1. This type of "empowerment" reduces the likelihood of the patient regarding himself as an "victim" and can help the patient recognize their role in the decision-making process that led to surgery

    2. The anesthesia provider may help the patient assume a level of control concerning their environment and situation-for example use of breathing control in promoting relaxation. 

       1. Providing opportunities for control may be especially important for children and young adolescence -- for example allowing a child to choose on which finger the pulse oximeter is to be placed would be such an example

    3.  Relaxation methods: The anesthesia provider may suggest contraction/relaxation cycles of muscles in a small region, such  toes or ankles

    4.  Mental distraction-such  music, selective attention, etc.  approaches which promote relaxation may be useful.

• Time of administration: 1-2 hours before anesthesia induction

• Outpatient setting: IV premedication just before surgery

  • Typically drugs are given closer to the time of surgery, i.e. the patient may arrive at the surgical setting without being premedicated (possibly anxious) with the idea of receiving medication just before the procedure

• Primary goals for premedication (premedication agents may include antihistamines, antiemetics, α₂ adrenergic receptor agonists, antacids, histamine receptor (H₂) antagonists, opioids, benzodiazepines, gastrointestinal stimulants)

  • Anxiolytic effects:  reduction in patient anxiety with expected  reduction in circulating catecholamines

  • Sedation

  • Reduction in preoperative pain (analgesic effect)

  • Amnesia:  the use of an amnestic agent is common with midazolam (Versed) often employed. 

    • Midazolam (Versed) belongs to the benzodiazepine category of drugs

  • Reduction in secretion:  antisialagogue effect

  • Increase in gastric fluid pH with a decrease in gastric fluid volume

    • These effects are designed to reduce risk which may be associated with aspiration

  • Reduction of autonomic nervous system reflex responses.

    • To accomplish this effect sometimes antimuscarinic agents are used in as a consequence surgical stimulation of muscarinic receptors are less likely to provoke adverse cardiac effects (e.g. bradycardia, arrhythmias)

  • Reduction in required anesthetic amounts

    • Premedication with sedative-hypnotic agents and/or opioids to reduce the amount of anesthetic required to achieve a given level of anesthesia.  The advantages may include more rapid emergence upon completion of the case

  • Prophylaxis with respect to allergic reaction (e.g. antihistamines may be helpful)

• Additional premedication issues:

  • Reduced cardiac activity (e.g., an anticholinergic drug such as atropine may prevent bradycardia associated for example with surgical-induced stimulation of muscarinic receptors).

    • To manage cardiac vagal activity, antimuscarinic agent should be administered DURING surgery, just prior to the expected need or in response to vagal stimulation

  • Reduction/avoidance of postoperative nausea and vomiting

    • Facilitated with I. V. antiemetic drug administration JUST PRIOR to awakening (this approach is probably better than waiting for symptom developments and then treating the nausea)

  • Postoperative analgesia may be best approached by use of IV opioids or neuraxial opioids JUST PRIOR to symptom development-here administration may be best provided just before awakening or just before a painful surgical action

• Circumstances in which sedative-hypnotic (depressant) or some other pharmacological premedication would be warranted:

  1. Cardiac surgery

  2. Cancer surgery

  3. In the presence of pre-existing pain:

     • Pain management is extremely important in all perioperative phases.  

       • This point of view is consistent with the consideration that pain is "unphysiologic". 

       • Preoperative pain may cause hypertension and other effects which may cause cardiovascular problems.  

       • Similarly, inadequate post-operative pain management may contribute to postoperative cardiac morbidity/mortality

  4. Regional anesthesia

•  Some circumstances in which sedative-hypnotic (depressant) pharmacological premedication would NOT be warranted:

  1. In the hypovolemic patient

  2. In the presence of significant, severe pulmonary disease (additional respiratory depression associated with sedative-hypnotics would be ill-advised)

  3. Intracranial pathology

  4. Reduced level of consciousness

  5. Probably not in elderly patients

  6. Newborns (< 1 years of age)

• Factors that influence the choice those drugs for premedications and associated dosages

  • Whether the surgery is classified as "inpatient" or "outpatient"

  • Whether the surgery is being performed as an elective or emergency procedure

  • Concerns about the ability of the patient to tolerate the drug

  • Patient age & weight & physical status

  • Anxiety level of the patient-Recall that an anxious patient is likely to have elevation of circulating catecholamines which may cause a suboptimal cardiovascular preoperative state

  • Whether the patient has had an adverse response to the particular medication during a previous procedure-This consideration emphasizes how important an adequate history or chart review is in deciding medication choice.

• ³Routes of Administration:

  • Most common is intramuscular.

    • Complications associated with intramuscular administration:

      • Sciatic nerve injury.

      • Suboptimal drug absorption.

      • Frequently "intramuscular" injection is actually deposited in adipose tissue, not muscle (frequency = 95% for women; 85% for men).

  • Administration for children (children may find needles and rectal administration objectionable):

    • Intranasal administration for children may be best; intranasal route of administration results in more rapid onset (compared to oral) with for example midazolam (Versed) and is also  beneficial because the approach does not require patient cooperation

  • Incremental intravenous sedation -- problem

    • Enough time must be allowed for the drug to take effect before additional dosage delivery

  • Oral premedication -- problem

    • Peak effect may not be realized before induction and significant and prolonged drug presence may complicate emergence following short surgical procedures [residual premedication, taken orally, maybe removed by stomach suctioning after induction]

 

References