Cardiovascular and arousal responses to laryngoscopy and tracheal intubation in patients with complete spinal cord injury

Dose requirements of alfentanil to eliminate autonomic responses during rapid-sequence induction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg

STUDY OBJECTIVE

Opioids are integral part of anesthesia induction, but information on optimal dosing is limited. We aimed to determine doses of alfentanil needed to eliminate increases in 5 autonomic response variables (plasma concentrations of epinephrine, norepinephrine and vasopressin, arterial blood pressure [ABP], and heart rate) during rapid-sequence induction of anesthesia with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.

DESIGN

Prospective, randomized, observer-blinded, interventional clinical study.

SETTING

Large academic institution.

PATIENTS

Eighty-four healthy patients, aged 18 to 55 years, received 1 of 7 assessor-blinded doses of alfentanil (0, 10, 20, 30, 40, 50, and 60 μg/kg) together with thiopental 4 mg/kg and rocuronium 0.6 mg/kg, administered in rapid succession (15 seconds). Laryngoscopy was initiated 40 seconds after rocuronium, and tracheal intubation was concluded within 15 seconds thereafter.

MEASUREMENTS

An indwelling radial artery catheter was used for hemodynamic monitoring and blood sampling. Relationships between alfentanil dose and response variables were tested with linear regression, and the influence of covariates (sex, body weight, and age) was determined. Alfentanil dose needed to prevent increases in ABP >10% above baseline with 95% probability was estimated with logistic regression.

MAIN RESULTS

Significant relationships were determined between alfentanil dose and response variables. Clinically interesting influence of covariates was not found. Alfentanil 55 μg/kg was needed to prevent increases in ABP postintubation >10% above baseline with 95% probability. One individual needed a bolus of vasopressor postintubation.

CONCLUSIONS

Optimal control of autonomic responses during rapid-sequence induction was achieved with clinically relevant doses of alfentanil in healthy patients anesthetized with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.

Effects of Esmolol on the Prevention of Haemodynamic Responses to Tracheal Extubation after Craniotomy Operations

OBJECTIVE

The aim of this study was to evaluate the effects of esmolol infusion on the prevention of haemodynamic responses to tracheal extubation in patients undergoing elective craniotomy.

METHODS

With approval from the Medical School Ethics Committee at Marmara University and the patients' written consent, 30 patients between 20-65 years of age undergoing elective craniotomy were randomly placed in either the Group Esmolol (n=15) or the Group Control (n=15). Anaesthesia was induced with 5-7 mg kg(-1) thiopental sodium, 1 μg kg(-1) remifentanil, and 0.1 mg kg(-1) vecuronium bromide iv, and was maintained with 1 MAC sevoflurane in oxygen-air mixture (50:50) and 0.25 μg kg(-1) min(-1) remifentanil infusion. At the end of the operation, patients inhaled 100% oxygen after the discontinuation of the anaesthetic agents. For Group Esmolol, 5 min before extubation 2 mg kg(-1) esmolol in 50 mL was infused over 10 min (0.2 μg kg(-1) min(-1)), while for Group Control, 50 mL saline was infused over 10 min. The quality of extubation was evaluated with a 5 point scale, recording heat rate, systolic, diastolic, and mean arterial pressures before infusion, 1 min after infusion, during extubation, and at 1, 3, 5, and 10 min after extubation.

RESULTS

In the esmolol group, systolic, diastolic, and mean arterial pressures, as well as heart rate, decreased significantly after esmolol infusion and were significantly lower than in the control group after extubation (p<0.05). The ratio of patients with an extubation score of one was significantly higher in the esmolol group than in the control group (p<0.05).

CONCLUSION

We concluded that 2 mg kg(-1) esmolol infusion before extubation can prevent hypertension and tachycardia caused by extubation in patients undergoing elective craniotomy.

Thiopental dose requirements for induction of anaesthesia and subsequent endotracheal intubation in patients with complete spinal cord injuries

BACKGROUND

Dose requirements of thiopental depend on patient characteristics and infusion rate. We determined thiopental dose requirements for induction of anaesthesia, and the effects of remifentanil on cardiovascular and bispectral index (BIS) responses to tracheal intubation in spinal cord-injured (SCI) patients undergoing general anaesthesia.

METHODS

Twenty patients with traumatic complete SCI undergoing elective surgery were enrolled. Twenty patients without SCI served as control. Anaesthesia was induced with thiopental, followed by remifentanil 1 μg/kg and rocuronium 0.8 mg/kg, and maintained with 2% sevoflurane and 50% nitrous oxide in oxygen after tracheal intubation. Thiopental was administered at a rate of 50 mg/15 s until abolition of the eyelash reflex. Thiopental doses, BIS values, systolic arterial blood pressure (SAP), heart rate (HR) and plasma catecholamine concentrations were measured.

RESULTS

Total thiopental dose required to abolish the eyelash reflex based on total body weight (BW) (5.26 ± 0.87 vs. 3.91 ± 1.07 mg/kg, P < 0.001) or lean BW (6.56 ± 1.37 vs. 5.24 ± 1.36 mg/kg, P < 0.01) were significantly smaller in the SCI group than in the control. SAP was decreased by induction of anaesthesia with thiopental and remifentanil, and increased by tracheal intubation in both groups. However, the peak SAP after intubation was smaller in the SCI patients. HR increased significantly above baseline values following intubation in both groups with no significant intergroup differences. Hypertension was more frequent in the control group. Norepinephrine concentrations remained unaltered following intubation in both groups.

CONCLUSIONS

These results suggest that the dose requirements of thiopental for induction of general anaesthesia and subsequent tracheal intubation are reduced in the SCI patients.

Altered cardiovascular responses to tracheal intubation in patients with complete spinal cord injury: relation to time course and affected level

BACKGROUND

We determined cardiovascular responses to tracheal intubation in relation to the time since injury in patients with different levels of spinal cord injury.

METHODS

Two hundred and fourteen patients with complete cord injury were studied. They were either quadriplegics (>C7, n=71) or paraplegics (<T5, n=143), and were subdivided into six groups each according to the time since injury: <4 week (acute), 4 week-1 yr, 1-5, 5-10, 10-20, and >20 yr. Twenty patients with no cord injury served as controls. Systolic arterial pressure (SAP), heart rate (HR), and plasma catecholamine concentrations were determined.

RESULTS

Intubation did not affect SAP in the quadriplegics regardless of the time post-injury, but it significantly increased SAP in all paraplegics. Moreover, the pressor response was enhanced in the paraplegics who were 10 yr or more since injury (P<0.05). HR increased significantly in all groups; the magnitude of the increase was less only in acute quadriplegics compared with controls. Plasma concentrations of norepinephrine increased in every group except for the quadriplegics within 4 weeks of injury. The maximum increases in SAP, HR, and norepinephrine from awake baseline values were smaller in the quadriplegics than in the paraplegics (P<0.01).

CONCLUSIONS

The cardiovascular and catecholamine responses to intubation change as a function of the time elapsed and the level of the cord injury. In this study, the pressor response to tracheal intubation was abolished in the quadriplegics but not in paraplegics; indeed, it was enhanced at 10 yr or more since injury in this group.