A brief literature review on hemodynamic responses to laryngoscopy and intubation and the role of LMA

Awake Intubation (procedure in brief)

Burstein et al (1950) induced anaesthesia with various combinations of cyclopropane, ether, N₂O, Pentothal sodium and cocaine in a study of 106 cases. They found substantial increase in pulse rate during laryngoscopy and endotracheal intubation in most of the cases. A deepening of plane of anaesthesia reduced the magnitude of this response (1).

King BD et al (1951) observed the cardiovascular changes with laryngoscopy and tracheal intubation in 46 patients who required GA for surgical procedures. Laryngoscopy was usually completed in 15 seconds. The average rise of systolic blood pressure, diastolic blood pressure and heart rate (HR) after laryngoscopy and tracheal intubation were 53 mm Hg, 34 mm Hg and 23 bpm respectively. They returned to pre-laryngoscopic level within 5 mins. With deepening of anaesthesia to 2^nd or 3^rd plane, intubation induced average rise in systolic blood pressure, diastolic blood pressure and heart rate were 16 mm Hg, 10 mm Hg and 13 bpm respectively.

They concluded that during light GA, direct laryngoscopy and endotracheal intubation is capable of producing circulatory effects characterized by a rise in BP and HR. These changes initiated by the laryngoscope passing on the base of tongue or lifting the epiglottis are independent of the type of laryngoscope blade used. Deeper anaesthesia abolishes these phenomena (2).

Prys-Roberts C et al (1971) studied the electrocardiographic and haemodynamic responses during the induction of anaesthesia followed by laryngoscopy and tracheal intubation in a group of 16 untreated hypertensive patients and in a group of 20 patients receiving antihypertensive therapy upto and including the day of surgery. They compared five different induction agents – thiopentone, methohexitone, propanidid, diazepam and neurolept analgesia induced by combination of phenoperidine and droperidol.

They came to the conclusion that prophylactic blockage of β-adrenergic receptors was necessary to prevent hypertensive crisis during laryngoscopy and tracheal intubation in both treated and untreated hypertensive patients (3).

Kautto UM (1982) studied the effects of fentanyl on arterial pressure and heart rate during laryngoscopy and intubation in 45 normotensive, surgical patients, who were randomly allocated to three groups receiving 2 or 6 micrograms/kg of fentanyl or saline in a double-blind fashion before anaesthetic induction with thiopental.

The result showed that fentanyl supplementation with 2 micrograms/kg significantly attenuated the arterial pressure and heart rate increases during laryngoscopy and intubation, and fentanyl, 6 micrograms/kg, completely abolished these responses (4).

Derbyshire DR et al (1983) measured plasma adrenaline and noradrenaline concentrations in 24 patients during the induction of anaesthesia and the subsequent tracheal intubation. The patients received either suxamethonium 1 mg/kg or pancuronium 0.1 mg/kg to facilitate tracheal intubation.  Mean arterial pressure (MAP) increased in both groups following laryngoscopy and tracheal intubation and there were concomitant increases in the plasma catecholamine concentrations, the changes being more marked in the suxamethonium group.

There was a significant correlation between MAP and plasma catecholamine concentrations in the suxamethonium group. Measurement of plasma catecholamine concentrations in samples obtained simultaneously from central venous, peripheral venous and arterial sites were in broad agreement; the greatest changes occurred in central venous samples (5).

Shribman AJ et al (1987) compared the catecholamine and cardiovascular responses to laryngoscopy alone with those following laryngoscopy and intubation in 24 patients allocated randomly to each group. Following induction with fentanyl and thiopentone, atracurium was administered and artificial ventilation undertaken via a facemask for 2 min with 67% nitrous oxide in oxygen. Following laryngoscopy, the vocal cords were visualized for 10 s. In one group of patients, ventilation was then re-instituted via a facemask, while in the second group the trachea was intubated during the 10-s period and ventilation of the lungs maintained. Arterial pressure, heart rate and plasma noradrenaline and adrenaline concentrations were measured before and after induction and at 1, 3 and 5 min after laryngoscopy.

There were significant and similar increases in arterial pressure and circulating catecholamine concentrations following laryngoscopy with or without intubation. Intubation, however, was associated with significant increases in heart rate, which did not occur, in the laryngoscopy-only group (6).

Braude N et al (1989) compared the pressor response of tracheal intubation with that of laryngeal mask insertion in two groups of 24 and 23 healthy patients respectively. All patients were anaesthetized with thiopentone, nitrous oxide, enflurane and paralysed with atracurium.

They showed a similar, but attenuated pattern of response associated with Laryngeal mask insertion in comparison with laryngoscopy and intubation; significant differences between the groups were evident in arterial diastolic blood pressure immediately after insertion and again 2 minutes later.  They concluded that use of the laryngeal mask may offer some limited advantages over tracheal intubation in the anaesthetic management of patients where the avoidance of the pressor response is of particular concern (7).

Hickey S et al (1990) investigated the cardiovascular effects related to insertion of the Brain laryngeal mask airway and compared these effects with those after insertion of a Guedel oral airway. Arterial pressure and heart rate in 100 patients were measured using an Ohmeda 2300 Finapres arterial pressure monitor. Arterial pressure decreased significantly (P<0.001) and heart rate increased significantly (P<0.001) after induction of anaesthesia with 2.5 mg/kg of propofol. A significant increase in arterial pressure (P<0.02) and in heart rate (P<0.001) followed insertion of the laryngeal mask and the Guedel airway, with no difference between the two groups at any time. The changes in arterial pressure and heart rate returned to 'at insertion' levels within 60 seconds of the stimulus (8).

Hassan HG et al (1991) studied the relationship between the intensity of the stimulus exerted against the base of the tongue during direct laryngoscopy and the magnitude of associated hemodynamic and catecholamine responses in 40 ASA I or II patients. Laryngoscopy lasting 40 s was performed with a size 3 Macintosh blade connected to a force-displacement transducer. The intensity of the stimulus exerted during laryngoscopy was expressed by the product of its average force (N) and duration (s) and given as impulse in Ns. Highly significant relationships were found between the impulse during laryngoscopy and the maximal hemodynamic and catecholamine responses. Also, when laryngoscopy was followed by orotracheal intubation, significant relationships were found with steeper slopes of the regression lines for systolic blood pressure, heart rate and plasma epinephrine concentrations. A more rapid regression of hemodynamic data was seen in intubated patients, whereas their plasma catecholamine concentrations regressed more slowly. The mechanisms of the responses to laryngoscopy and orotracheal intubation were proposed to be by somato-visceral reflexes. Stimulation of proprioceptors at the base of the tongue during laryngoscopy induced impulse-dependent increases of systemic blood pressure, heart rate and plasma catecholamine concentrations. Subsequent orotracheal intubation recruited additional receptors that elicit augmented hemodynamic and epinephrine responses as well as some vagal inhibition of the heart (9).

Wilson IG et al (1992) compared the cardiovascular responses induced by laryngoscopy and intubation with those produced by insertion of a laryngeal mask in 40 healthy patients. Anaesthesia was induced with thiopentone and maintained with enflurane and nitrous oxide in oxygen. Vecuronium was used for muscle relaxation. Arterial pressure was measured with a Finapres monitor. The mean maximum increase in systolic arterial pressure after laryngoscopy and tracheal intubation was 51.3% compared with 22.9% for laryngeal mask insertion (p less than 0.01). Increases in maximum heart rate were similar, (26.6% v 25.7%) although heart rate remained elevated for longer after tracheal intubation. They concluded that insertion of the laryngeal mask airway was accompanied by smaller cardiovascular responses than those after laryngoscopy and intubation and that its use may be indicated in those patients in whom a marked pressor response would be deleterious (10).

Brimacombe J (1995) performed a meta-analysis on randomized prospective trials comparing the laryngeal mask airway (LMA) with other forms of airway management to determine if the LMA offered any advantages over the tracheal tube (TT) or facemask (FM). Of the 858 LMA publications identified to December 1994, 52 met the criteria for the analysis. Thirty-two different issues were tested using Fisher's method for combining the P values. The LMA has 13 advantages over the TT and four over the FM. The LMA had two disadvantages over the TT and one over the FM. There were 12 issues where neither device had an advantage.

Advantages over the TT included: increased speed and ease of placement by inexperienced personnel; increased speed of placement by anaesthetists; improved haemodynamic stability at induction and during emergence; minimal increase in intraocular pressure following insertion; reduced anaesthetic requirements for airway tolerance; lower frequency of coughing during emergence; improved oxygen saturation during emergence; and lower incidence of sore throat in adults.

Advantages over the FM included: easier placement by inexperienced personnel; improved oxygen saturation; less hand fatigue; and improved operating conditions during minor paediatric otological surgery.

Disadvantages over the TT were lower seal pressures and a higher frequency of gastric insufflation. The only disadvantage compared with the FM was that oesophageal reflux was more likely (11).

Fujii Y et al (1995) studied the effects of laryngeal mask airway (LMA) insertion and tracheal intubation on circulatory responses in normotensive (n = 24) and hypertensive (n = 22) patients. In a randomized, double-blind manner, LMA insertion or tracheal intubation was performed after induction of anaesthesia with thiopentone and muscle relaxation with succinylcholine. In both normotensive and hypertensive patients, heart rate (HR), mean arterial pressure (MAP) and rate-pressure product increased after tracheal intubation or LMA insertion compared with baseline (P < 0.05).

The haemodynamic changes were greater after intubation than after LMA insertion (P < 0.05). Following intubation of the trachea or insertion of the LMA, HR increased more markedly in hypertensive patients than in normotensive patients (P < 0.05). Plasma adrenaline and noradrenaline concentrations after tracheal intubation or LMA insertion increased compared with baseline values (P < 0.05) in normotensive and hypertensive patients. The increase in noradrenaline concentration after tracheal intubation was greater than that after LMA insertion (P < 0.05). No patient revealed ECG evidence of myocardial ischaemia. They concluded that insertion of LMA is associated with less circulatory responses than tracheal intubation in both normotensive and hypertensive patients (12).

Upadhye SM et al (1996) compared the haemodynamic responses to endotracheal intubation and Laryngeal Mask Airway insertion in 50 adult patients of ASA Grade I undergoing various elective surgical procedures. With similar anaesthesia technique, they observed haemodynamic response of the patients in the form of increases in heart rate, systolic, diastolic and mean blood pressure at similar intervals during intubation and LMA insertion. The increase in heart rate, systolic blood pressure and mean blood pressure was significantly (p<0.01) more in the ETT groups compared to the LMA group. Hence, they concluded that use of LMA might offer some advantage in patients where avoidance of pressor response is of particular concern (13).

Jain MK et al (2010) – Their aim was to see if there was any problem regarding controlled ventilation of patients during Laparoscopic cholecystectomy using PLMA. For this, 10 patients between 21-42 years of age belonging to ASA I-II undergoing elective Laparoscopic Cholecystectomy were selected. Pulse rate, systolic/diastolic/mean blood pressure, ETCO₂, SPO₂, ABG (Na+, K+, Ca++, Cl-1, Glucose, pH, PO₂, PCO₂, HCOзˉ, BEB, An Gap, O₂ content, a/A, PO₂/FiO₂)and peak airway pressure were monitored preoperatively (as base line), just after insufflations of CO₂, 30 min. after insufflations of CO₂, after drain out of CO₂ and after removal of PLMA.

It was seen that all studied variables and ABG mean increased from preoperative point of time to 30 min after insufflations and then slightly decreases from 30 min after insufflations point and remained high during the period of pneumoperitoneum, which came to baseline after gas removal (removal of PLMA point) for almost all the variables except in case of peak airway pressure. They concluded that PLMA can be used as airway maintaining device in case of laparoscopic cholecystectomies (14).

Russo SG et al (2009) examined to see if LMA-ProSeal is an adequate tool for elective postoperative care in the intensive care unit (ICU) and potentially associated with less hemodynamic alteration during extubation in the ICU environment compared to an endotracheal tube. For the study, forty-eight patients were enrolled. The study was planned as a prospective randomized, controlled trial and patients were allocated to either control (ICU-T) or study group (ICU-P). In the ICU-P group, the endotracheal tube was replaced by a PLMA at the end of surgery.

They found that cardiovascular parameters increased significantly less in the ICU-P group: systolic blood pressure increased by 18.10 ± 5.57 mmHg versus 34.65 ± 5.63 mmHg (P < 0.05), mean arterial blood pressure increased by 11.23 ± 3.25 mmHg versus 22.65 ± 3.36 mmHg (P < 0.05), and heart rate increased by 9.3 ± 2.9 versus 12.9 ± 2.2 min (P < 0.05). Ventilation via the PLMA during transfer from the operation room to the ICU as well as during ICU stay was successful and without any adverse events.

They concluded that removal of the PLMA after recovery from anaesthesia was associated with less cardiovascular change compared to the endotracheal tube. Ventilation was possible without reported adverse events during the entire trial. Elective endotracheal tube replacement by the PLMA may be a useful procedure in selected patients (15).

References:

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1.	Burstein C, Lo Pinto F, Newman W. Electrocardiographic studies during endotracheal intubation. I. Effects during usual routine techniques. Anesthesiology. 1950 Mar; 11(2): p. 224-37.
2.	King B, Harris Jr L, Greifenstein F, Elder Jr J, Dripps R. Reflex circulatory responses to direct laryngoscopy and tracheal intubation performed during general anesthesia. Anesthesiology. 1951 Sept; 12(5): p. 556-66.
3.	Prys-Roberts C, Greene L, Meloche R, Foëx P. Studies of anaesthesia in relation to hypertension. II. Haemodynamic consequences of induction and endotracheal intubation. Br J Anaesth. 1971 Jun; 43(6): p. 531-47.
4.	Kautto U. Attenuation of the circulatory response to laryngoscopy and intubation by fentanyl. Acta Anaesthesiol Scand. 1982 Jun; 26(3): p. 217-21.
5.	Derbyshire D, Chmielewski A, Fell D, Vater M, Achola K, Smith G. Plasma catecholamine responses to tracheal intubation. Br J Anaesth. 1983 Sep; 55(9): p. 855-60.
6.	Shribman A, Smith G, al e. Cardiovascular and catecholamine responses to laryngoscopy with and without tracheal intubation. Br. J. Anaesth. 1987; 59(3): p. 295-299.
7.	Braude N, Clements E, Hodges U, Andrews B. The pressor response and laryngeal mask insertion. A comparison with tracheal intubation. Anaesthesia. 1989 Jul; 44(7): p. 551-4.
8.	Hickey S, Cameron A, Asbury A. Cardiovascular response to insertion of Brain's laryngeal mask. Anaesthesia. 1990 Aug; 45(8): p. 629-33.
9.	Hassan H, El-Sharkawy T, Renck H, al e. Hemodynamic and catecholamine responses to laryngoscopy with vs. without endotracheal intubation. Acta Anaesthesiologica Scandinavica. 1991 July; 35(5): p. 442–447.
10.	Wilson I, Fell D, Robinson S, Smith G. Cardiovascular responses to insertion of the laryngeal mask. Anaesthesia. 1992 Apr; 47(4): p. 300-2.
11.	Brimacombe J. The advantages of the LMA over the tracheal tube or facemask: a meta-analysis. Canadian Journal of Anaesthesia. 1995 November; 42(11): p. 1017-1023.
12.	Fujii Y, Tanaka H, Toyooka H. Circulatory responses to laryngeal mask airway insertion or tracheal intubation in normotensive and hypertensive patients. Can J Anaesth. 1995 Jan; 42(1): p. 32-6.
13.	Upadhye S, Behl S, Kulkarni A, Shah S. Comparison of hemodynamic responses to laryngeal mask airway insertion and endotracheal intubation. Journal of Anaesthesiology Clinical Pharmacology. 1996 Oct; 12(4): p. 279-81.
14.	Jain M, Venugopal M, Tripathi C. Use of proseal LMA (PLMA) for laparoscopic cholecystectomies: An ABG analysis. J Anaesth Clin Pharmacol. 2010; 26(1): p. 87-90.
15.	Russo S, Goetze B, Troche S, Barwing J, Quintel M, Timmermann A. LMA-ProSeal for elective postoperative care on the intensive care unit: a prospective, randomized trial. Anesthesiology. 2009 Jul; 111(1): p. 116-21.