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Effect-compartment equilibrium rate constant (keo) for propofol during induction of anesthesia with a target-controlled infusion device

Lim TA, Wong WH, Lim KY

J Anesth, 2006;20(2):153-5.
PMID: 16633780

The effect-compartment concentration (C(e)) of a drug at a specific pharmacodynamic endpoint should be independent of the rate of drug injection. We used this assumption to derive an effect-compartment equilibrium rate constant (k(eo)) for propofol during induction of anesthesia, using a target controlled infusion device (Diprifusor). Eighteen unpremedicated patients were induced with a target blood propofol concentration of 5 microg x ml(-1) (group 1), while another 18 were induced with a target concentration of 6 microg x ml(-1) (group 2). The time at loss of the eyelash reflex was recorded. Computer simulation was used to derive the rate constant (k(eo)) that resulted in the mean C(e) at loss of the eyelash reflex in group 1 being equal to that in group 2. Using this population technique, we found the k(eo) to be 0.57 min(-1). The mean (SD) effect compartment concentration at loss of the eyelash reflex was 2.39 (0.70) microg x ml(-1). This means that to achieve a desired C(e) within 3 min of induction, the initial target blood concentration should be set at 1.67 times that of the desired C(e) for 1 min, after which it should revert to the desired concentration.

Matched MeSH terms: Infusion Pumps
Chemo-port insertion: A cause of vocal cord palsy

Alazzawi S, Hindi K, Malik A, Wee CA, Prepageran N

Laryngoscope, 2015 Nov;125(11):2551-2.
PMID: 26108861 DOI: 10.1002/lary.25422

We describe extremely rare cases of vocal cord palsy following surgical insertion of a chemo port. Our cohort consisted of patients with cancer who developed hoarseness immediately after central venous line placement for the administration of chemotherapy, with vocal cord palsy confirmed with flexible laryngoscopy. Given the timing, central venous line placement appears to be the most likely cause.

Matched MeSH terms: Infusion Pumps, Implantable*
Sedation with dexmedetomidine versus propofol during regional anaesthesia: comparing haemodynamic parameters, respiratory rates and offset times

Nadia, M.N., Samsul Johari, M.A., Muhammad, M., Raha, A.R., Nurlia, Y.

Journal of Surgical Academia, 2012;2(2):15-20.
MyJurnal

This study aimed to compare dexmedetomidine and propofol, in terms of haemodynamic parameters, respiratory rates and offset times, when used for sedation in patients undergoing elective orthopaedic and surgical procedures under regional anaesthesia. This was a prospective, randomised, single-blind study where 88 patients were recruited. Patients were randomised into two groups to receive either dexmedetomidine or propofol infusion. Central neuraxial blockade (spinal, epidural or combined spinal epidural) was performed. After ensuring an adequate block and stable haemodynamic parameters, dexmedetomidine was infused 15 minutes later at 0.4 μg/kg/hr, and propofol, at a target concentration of 2.5 μg/ml. Both drugs were titrated to achieve a bispectral index score of 70 before surgery commenced. Sedation level was monitored using the bispectral index score and assessed by the Observer Assessment of Alertness Scale score. Drug infusion was adjusted to maintain bispectral index scores ranging between 70-80 during surgery. Both groups showed reductions in mean arterial pressure and heart rate from baseline readings throughout the infusion time. However there was no significant reduction in the first 15 minutes from baseline (p > 0.05). Haemodynamic parameters and respiratory rate between both groups were not significantly different (p > 0.05). No patient demonstrated significant respiratory depression or SpO2 ≤ 95%. Offset times were also not significantly different between both groups (p = 0.594). There were no significant differences in haemodynamic parameters, respiratory rates and offset times between dexmedetomidine and propofol used for sedation in patients undergoing elective orthopaedic and surgical procedures under regional anaesthesia.

Matched MeSH terms: Infusion Pumps
Stability of dobutamine in continuous ambulatory delivery devices

Al Madfai F, Valah B, Zaidi STR, Wanandy T, Ming LC, Peterson GM, et al.

J Clin Pharm Ther, 2018 Aug;43(4):530-535.
PMID: 29500838 DOI: 10.1111/jcpt.12674

WHAT IS KNOWN AND OBJECTIVE: Continuous infusion of dobutamine plays an important role in the management of patients with end-stage heart failure. Home infusion of dobutamine using a continuous ambulatory delivery device (CADD) facilitates the management of patients in their home, avoiding complications associated with long-term hospitalization. However, the stability of dobutamine in CADD is currently unknown. Therefore, this study investigated the physicochemical stability of dobutamine in CADDs at three different temperatures over various time points.
METHODS: Six CADDs (three containing dobutamine 10 mg/mL in 0.9% sodium chloride and three containing dobutamine 10 mg/mL in 5% glucose) were prepared and stored at 4°C for 7 days, followed by 12 hours at 35°C and then for another 12 hours at 25°C. An aliquot (n = 3) was withdrawn aseptically at 0, 24, 48, 72, 96, 120, 144 and 168 hours when stored at 4°C, and at 0, 6 and 12 hours when stored at the other two temperatures. Each sample was analysed for dobutamine concentration using a stability-indicating high-performance liquid chromatography. All the samples were also evaluated for change in pH, colour and for particle content.
RESULTS AND DISCUSSION: No evidence of particle formation, colour or pH change was observed throughout the study period. Dobutamine, when admixed with 0.9% sodium chloride or 5% glucose, was found to be chemically stable for at least 168 hours at 4°C and for another 12 hours at 35°C and for another 12 hours at 25°C.
WHAT IS NEW AND CONCLUSIONS: Our findings will allow health professionals to provide a weekly supply of dobutamine-containing CADDs to patients for home infusions. Continuous infusion over a 24-hour period using one CADD per day will also decrease the number of exchanges required and thus reduce the risk of catheter-related bloodstream infections.

Matched MeSH terms: Infusion Pumps