Extubation

It is difficult to predict if a neurologically injured patient will successfully be extubated. Salam et alstudied 88 patients prospectively, measuring cough peak flow (CPF), endotracheal secretions, and the ability to complete four simple tasks prior to extubation. In patients who failed extubation, they had a lower CPF p = 0.03), higher amount of secretions (RR 3.0, 95% Cl 1.0-8.8), and diminished ability to complete the four simple tasks (RR 4.3, 95% Cl 1.8-10.4). 

Salam A, Tilluckdharry L, Amoateng-Adjepong Y, Manthous CA. Neurological status, cough, secretions and extubation outcomes. Intensive Care Med 2004 30(7) 1334 1339. 

Tube displacement Self-extubation Vomiting or coughing Inadequate fixation (jejunostomy)... 

Draw four twitches at 0.5 s intervals with each being lesser in amplitude than its predecessor. In the example, the TOFR is 20% as T4 gives 20% of the response of Tl. Explain that this patient would be suitable for reversal as all four twitches are present. However, had this trace been elicited after the administration of a reversal agent, the pattern would represent an inadequate level of reversal for extubation (TOFR < 90%). 

Postoperative shivering following mild hypothermia has been associated with increased myocardial oxygen demand, which may lead to myocardial ischemia (48). It can also cause increased intracranial pressure (49). In addition, shivering may result in metabolic acidosis secondary to increased carbon dioxide production. Shivering can be minimized by careful rewarming of the patient before extubation and by using low-dose meperidine or clonidine. 

After collecting the last sample (90 min after intrathecal administration of test substance) the catheters were removed, and all incisions were sutured. Isoflu-rane was discontinued, and the lungs were ventilated with 100% oxygen. Extubation of the trachea was performed when adequate spontaneous ventilation occurred. The animals were allowed to recover with infusion of Ringer s solution and antibiotic treatment. 

In a Canadian multicenter, open, randomized trial in 156 patients to determine whether sedation with propofol would lead to shorter times to tracheal extubation and length of stay in ICU than sedation with midazolam, the patients who received propofol spent longer at the target sedation level than those who received midazolam (60 versus 44% respectively) (10). Propofol allowed clinically significantly earlier tracheal extubation than midazolam (6.7 versus 25 hours). However, this did not result in earlier discharge from the ICU. 

CALCIUM CHANNEL BLOCKERS OPIOIDS Diltiazem prolongs the action of alfentanil Diltiazem inhibits CYP3A4-mediated metabolism of alfentanil Watch for the prolonged action of alfentanil in patients taking calcium channel blockers case reports of delayed extubation in patients recovering from anaesthetics involving large doses of alfentanil in patients on diltiazem... 

A 35-year-old man developed recurrent respiratory depression after being given alfentanil 0.0125 mg/kg for vitreoretinal surgery (5). General anesthesia was induced with a combination of propofol, rocuronium, and alfentanil, subsequent inhalation of isoflurane, and three additional doses of alfentanil (total 0.04 mg/kg over 2 hours). The pulse oxygen saturation fluctuated and was as low as 89% 180 minutes after extubation. 

Diltiazem reduces the elimination of alfentanil and prolongs the time to tracheal extubation (SEDA-21, 86) erythromycin may do the same (14). 

There have been two studies of doxapram in very low birth weight infants before extubation. In one it was concluded that doxapram did not increase the likelihood of successful extubation. In the other there was an increase in systolic blood pressure along with much higher plasma doxapram concentrations than expected (9,10). 

Barrington KJ, Muttitt SC. Randomized, controlled, blinded trial of doxapram for extubation of the very low birthweight infant. Acta Paediatr 1998 87(2) 191. ... 

In a prospective randomized study of 120 day-surgery patients, desflurane and sevoflurane were associated with shorter times to awakening, extubation, and orientation than propofol infusion (27). Average times to awakening at the end of anesthesia were 5, 5, and 8 minutes respectively. There were no significant differences in time-to-home readiness or actual discharge times. A review of 436 patients undergoing either sevoflurane or propofol-based anesthesia showed no difference in similar recovery end-points (19). 

A 38-year-old woman took 60 tablets of levetiracetam 500 mg. She vomited 4 hours later, and 2 hours after that was obtunded with respiratory depression. Her levetiracetam serum concentration was 400 pg/ml at 6 hours, 72 pg/ml at 18 hours, and 60 pg/ml at 20.5 hours (target serum concentration 10-37 pg/ml). The half-life was 5.1 hours, similar to the usually reported half-life. She was extubated the next day and recovered without sequelae. 

A 71-year-old man complained of difficulty in breathing and was desaturated on pulse oximetry for 5 minutes after cervical plexus blockade (89). He required tracheal intubation, was ventilated for 110 minutes, and was then successfully extubated. It was thought that the most likely diagnosis was cardiorespiratory failure exacerbated by phrenic nerve blockade. 

A 67-year-old man developed transient hemiparesis and facial nerve palsy before becoming unconscious and apneic 10 minutes after a right cervical plexus block (89). His trachea was intubated without the need for anesthetic drugs and he was ventilated. Hypotension was treated with intravenous ephedrine. He woke up, started breathing, and was extubated 75 minutes later. The authors postulated brainstem anesthesia following accidental injection of local anesthetic into a dural cuff as a cause of loss of consciousness. 

A 68-year-old man developed total spinal anesthesia after the administration of 20 ml of ropivacaine 1% without a prior test dose via an epidural catheter, which was inadvertently placed intrathecally (83). Initial aspiration of both the Touhy needle and the catheter failed to identify the intrathecal position of the catheter. The patient noted weakness in his right leg immediately after the end of the injection. This was followed by weakness in his right arm, asystole, apnea, and loss of consciousness. Ventricular escape beats were noted and sinus rhythm returned after mask ventilation with 100% oxygen and the administration of atropine 1 mg and ephedrine 50 mg. He was able to open his eyes, but remained apneic and was therefore intubated and ventilated. Cardiovascular stabihty was maintained with incremental boluses of ephedrine to a total of 60 mg. He regained consciousness and was successfully extubated 145 minutes later. AH sensory and motor deficits had resolved within 8 hours and no neurological deficit or transient neurological symptoms were detected 5 days later. 

Total spinal anesthesia was suspected in a 46-year-old man who was found unconscious and apneic with no palpable cardiac output 20 minutes after a high thoracic (T2/3) epidural injection of 3 ml hdocaine 1% and 3 ml bupivacaine 0.125% (141). Following initial cardiopulmonary resuscitation he was admitted to the intensive care unit, where treatment included mechanical lung ventilation, thiamylal infusion, and cooling to a core temperature of 33-34 C. The thiamylal was withdrawn after 17 days and he was warmed and successfully extubated the next day. He was discharged after a further 4 months of rehabihtation with no relevant neurological consequences. 

A 2-month-old child given perioperative phenylephrine drops during cataract extraction developed ventricular extra beats, very severe hypertension, and pulmonary edema requiring intensive therapy (5). Extubation was possible within 3 hours, and she recovered with no untoward consequences. 

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