Anaesthetics intravenous

Diethyl ether Epilepsy Enflurane All volatile anaesthetics Intravenous anaesthetics... 

The general anaesthetics may be divided into three groups based solely on the method of administration. These are inhalation anaesthetics intravenous anaesthetics and basal anaesthetics. 

CifiHijClNj. White plates m.p. 125 C. Diazepam is one of several benzodiazepines which are very widely used as minor tranquillizers for allaying anxiety, as hypnotics or, in sufficiently high dosage given intravenously, as pre-anaesthetic sedatives. 

Class IB drugs like lidocaine, phenytoin or mex-iletine preferentially bind to the inactivated state. Lidocaine, a local anaesthetic, can be used intravenously for antiarrhythmic treatment. It is one of the classical dtugs used in emergency medicine for the... 

The other method used is infusion of intravenous anaesthetics such as propofol, etomidate (for induction) and the barbiturates such as thiopental and pentobarbital. Investigations into the mechanism of anaesthesia have made use of all these compounds in order to identify a common mode of action linked to likely mechanisms within the CNS. 

These observations, while implicating steroids in brain function and behaviour, cannot be taken as a reliable indicator of their actual effect on neuronal function. Nevertheless, some neurosteroids produce CNS depression with a rapid inhibition of neuronal excitability and one progesterone derivative, alphaxalone (3a-hydroxy-5a pregnane-11, 20 dione, see Fig. 13.5) has been used effectively as an intravenous anaesthetic in humans. 

Figure 4.4. Plasma histamine levels in response to NT given at t = 0. Rats were anaesthetized and NT (5 nmol/kg) or saline (0-3 ml) given intravenously. Blood was collected at the indicated times. Mean S.E.M. of mean of n values (in parentheses). Horizontal arrow is the histamine level before NT.

Naunyn-Schmiedeberg s Archives of Pharmacology Figure 10. Blood pressure and heart frequency in an anaesthetized cat with sectioned vagi and pretreatment with atropine (1 mg/kg). Decrease of blood pressure and heart rate in beats/min (S/min) after intracisternal (i.ci.) and intravenous (i.v.) injection... 

Figure 13. Mean blood pressure in anaesthetized rabbits (0.75 g/kg urethan i.p. and 30 mg Nembutal i.v.) under the influence of St 91 given either intravenously (i.v.) or intracistemally (i.ci.)...

Figure 7.4. Antagonism by ondansetron of the von Bezotd Jarisch reflex in the anaesthetized cat induced by the administration of 2-methyl-5-HT. Symbols indicate the time course of antagonism following intravenous administration of ondansetron at I ( 9 ), 3 ( O ), 10 ( M ) or 30 itgikg f j. Each set of data points represents data from a single animal. Experiments were performed as described by Butler et al. [7].

Propanidid seems, therefore, to possess many advantages over former intravenous anaesthetics. In particular, procedures of short duration (especially under out-patient conditions [158] and induction in many poor-risk patients), seem particularly suitable for exploitation of its properties. 

Noradrenaline and adrenaline are the classic catecholamines and neurotransmitters in the sympathetic nervous system. Noradrenaline stimulates the following subtypes of adrenoceptors P, a, U2. It has positive inotropic and chronotropic activities as a result of /3i-receptor stimulation. In addition, it is a potent vasoconstrictor agent as a result of the stimulation of both subtypes (ai,a2) of a-adrenoceptors. After intravenous infusion, its effects develop within a few minutes, and these actions disappear within 1-2 minutes after stopping the infusion. It may be used in conditions of acute hypotension and shock, especially in patients with very low vascular resistance. It is also frequently used as a vasoconstrictor, added to local anaesthetics. Adrenaline stimulates the following subtypes of adrenoceptors /3i, P2, oil, 0L2. Its pharmacological profile greatly resembles that of noradrenaline (see above), as well as its potential applications in shock and hypotension. Like noradrenaline, its onset and duration of action are very short, as a result of rapid inactivation in vivo. Both noradrenaline and adrenaline may be used for cardiac stimulation. Their vasoconstrictor activity should be kept in mind. A problem associated with the use of /3-adrenoceptor stimulants is the tachyphylaxis of their effects, explained by the /3-adrenoceptor downregulation, which is characteristic for heart failure. 

Hypotensive activity. Tincture of the gland, administered intravenously to rabbits, was active " """. Water extract of the dried gum resin, administered intravenously to dogs at variable doses, was active " """. Gum extract, administered to anaesthetized rats at doses of 0.3-2.2 mg/100 g body weight, significantly reduced the mean arterial blood pressure " """. 

Eilers H, Niemann C. Clinically important drug interactions with intravenous anaesthetics in older patients. Drugs Aging 2003,20 969-980. 

Norberg L, Wahlstrom G, Backstrom T The anaesthetic potency of 3a-hydroxy-5a-pregnan-20-one and 3a-hydroxy-5b-pregnan-20-one determined with an intravenous EEG-threshold method in male rats. Pharmacol Toxicol 61 42-47, 1987 Nordberg A Human nicotinic receptors-their role in aging and dementia. Neurochem Int 25 93-97, 1994... 

Intravenous anaesthetics are mainly used for rapid induction of anaesthesia, which is then maintained by an inhalational agent. They also serve to reduce the amount of maintenance anaesthetics. 

It is an oily liquid eugenol derivative and less potent than thiopentone. It is a very short acting intravenous anaesthetic and specially used for very short outpatient operations and dental procedures. 

It is a new non-barbiturate anaesthetic agent and pharmacologically related to phencyclidine, a hallucinogen. Intravenous ketamine produces unconsciousness and analgesia within 30 seconds. It can be given by intramuscular route also. It acts on the cerebral cortex and subcortical areas. 

It is a new intravenous anaesthetic agent with poor analgesic property. It has a briefer duration of action than thiopentone. It produces little cardiovascular and respiratory depression. A single intravenous dose produces loss of consciousness within 10 seconds and a state of anaesthesia. 

Figure 2.8 Context-sensitive half-times for some intravenous anaesthetic drugs. Note the different half-time scale for die two panels.

Figure 3.1 Graph showing the ratio between inspired (FJ) and alveolar (FA) end-tidal concentrations of the agents shown. The least soluble agents approach equilibrium (FA/FI=1) the most rapidly. Also, since both inhalation and intravenous anaesthetic drugs tend to reduce cardiac output, they facilitate the uptake of volatile agents. It follows that any inhaled anaesthetic drug must be given with great caution to patients in shocked states, e.g. hypovolaemia, arrhythmias, myocardial infarction.

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