Comparison of double intravenous vasopressor automated system using nexfin versus manual vasopressor bolus administration for maintenance of haemodynamic stability during spinal anaesthesia for caesarean delivery: A randomised double-blind controlled trial

Performance of closed-loop systems for intravenous drug administration: a systematic review and meta-analysis of randomised controlled trials

Closed-loop drug delivery systems are autonomous computers able to administer medication in response to changes in physiological parameters (controlled variables). While limited evidence suggested that closed-loop systems can perform better than manual drug administration in certain settings, this technology remains a research tool with an uncertain risk/benefit profile. Our aim was comparing the performance of closed-loop systems with manual intravenous drug administration in adults. We searched MEDLINE, CENTRAL, and Embase from inception until November 2022, without restriction to language. We assessed for inclusion randomised controlled trials comparing closed-loop and manual administration of intravenous drugs in adults, intraoperatively or in the Intensive Care Unit. We identified 32 studies on closed-loop administration of propofol, noradrenaline, phenylephrine, insulin, neuromuscular blockers, and vasodilators. Most studies were at moderate or high risk of bias. The results showed that closed-loop systems reduced the duration of blood pressure outside prespecified targets during noradrenaline (MD 14.9%, 95% CI 9.6-20.2%, I2 = 66.6%) and vasodilators administration (MD 7.4%, 95% CI 5.2-9.7%, I2 = 62.3%). Closed-loop systems also decreased the duration of recovery after propofol (MD 1.3 min, 95% CI 0.4-2.1 min, I2 = 58.6%) and neuromuscular blockers (MD 9.0 min, 95% CI 7.9-10.0 min, I2 = 0%). The certainty of the evidence was low or very low for most outcomes. Automatic technology may be used to improve the hemodynamic profile during noradrenaline and vasodilators administration and reduce the duration of postanaesthetic recovery.Registration: This systematic review was registered with PROSPERO (CRD42022336950) on the 7th of June 2022.

Evaluating an advanced double intravenous vasopressor automated system to treat hypotension during spinal anesthesia for cesarean delivery: a randomized controlled trial

BACKGROUND

The optimal treatment of hypotension during spinal anaesthesia is uncertain. A novel double intravenous vasopressor automated (DIVA) system reduces hypotension compared to standard care, and was subsequently modified to an advanced-DIVA (ADIVA) system. The primary objective was to compare ADIVA versus DIVA on incidence of hypotension (systolic BP (SBP) < 80% baseline).

METHODS

We conducted a randomized-controlled trial in women undergoing elective cesarean delivery under spinal anesthesia. SBP and heart rate were measured continuously using a Nexfin monitor. ADIVA delivered 25 μg phenylephrine (heart rate > 60 beats.min^-1) or 2 mg ephedrine (heart rate < 60 beats.min^-1) at SBP 90 to 110% of baseline, 50 μg phenylephrine or 4 mg ephedrine at SBP 80 to 90%, and 75 μg phenylephrine or 6 mg ephedrine at SBP < 80%. ADIVA calculated the trend of SBP; vasopressors were administered rapidly if SBP trended downward, or 30 s if SBP trended upward. In contrast, DIVA delivered 25 μg phenylephrine or 2 mg ephedrine at SBP 90 to 100% of baseline, and 50 μg phenylephrine or 4 mg ephedrine at SBP < 90%. Boluses were followed by a 10-s lockout. Other outcomes included hypertension (SBP > 120% baseline), vasopressor consumption, clinical outcomes, and performance measures from spinal anesthesia to fetal delivery.

RESULTS

We analyzed 94 parturients (ADIVA: n = 46, DIVA: n = 48), with no difference in the incidence of hypotension between ADIVA (78.3%) and DIVA (83.3%, p = 0.677). ADIVA had significantly higher proportion of hypotensive SBP readings, lower phenylephrine consumption and higher umbilical arterial pH. There was no difference in hypertension, bradycardia, ephedrine consumption, intravenous fluid volume, nausea/vomiting, Apgar scores, and umbilical venous pH or lactate. ADIVA maintained SBP higher above baseline with greater fluctuation than DIVA.

CONCLUSION

ADIVA was associated with a greater proportion of hypotensive SBP readings, reduced phenylephrine consumption, and increased umbilical arterial pH than DIVA. Further research is needed to determine the optimal method of vasopressor delivery in parturients undergoing cesarean delivery.

TRIAL REGISTRATION

This study was registered on Clinicaltrials.gov registry (NCT03620942) on 08/08/2018.

An advanced double intravenous vasopressor automated system to treat hypotension during spinal anaesthesia for caesarean section: A pilot study

BACKGROUND

During spinal anaesthesia for caesarean section, haemodynamic instability may lead to maternal and foetal complications. We developed a novel advanced double intravenous vasopressor automated system (ADIVA) by using a continuous blood pressure and heart rate monitor. Treatment of hypotension was based on three criteria: the drug (phenylephrine or ephedrine) according to the heart rate; the dose of vasopressor determined by the degree of hypotension; a fast or slow bolus of vasopressor administered depending on whether there was a negative or positive gradient of SBP changes, respectively.

OBJECTIVE

The aim of this pilot study was to investigate the feasibility of the ADIVA algorithm.

DESIGN

A prospective pilot study.

SETTING

Single obstetrics and gynaecology centre in Singapore.

PATIENTS

Women undergoing elective caesarean delivery under spinal anaesthesia.

INTERVENTION

Automated administration of ephedrine or phenylephrine based on changes in blood pressure and heart rate (via the ADIVA algorithm) detected on continuous noninvasive haemodynamic monitoring using noninvasive continuous haemodynamic monitor (Nexfin).

MAIN OUTCOME MEASURES

The primary outcome was the incidence of hypotension, defined as SBP less than 80% of baseline. The secondary outcome measures were reactive hypertension, total vasopressor requirement, maternal and neonatal outcomes and system performance.

RESULTS

Forty-five women were recruited. Thirty-one women (69.9%) had at least one reading of hypotension. SBP was within ±20% of the baseline in a mean ± SD of 79.7 ± 17.6% of measurements. Forty-four (97.8%) women required phenylephrine before delivery, while 15 (33.3%) required ephedrine. No rescue medications were required. Three women (6.7%) had nausea and two (4.4%) vomiting. All neonates had APGAR scores of 9 at 5 min.

CONCLUSION

The ADIVA system, with noninvasive continuous haemodynamic monitoring, was able to maintain maternal SBP within ±20% of baseline for the vast majority of the measurements. This system had good maternal and foetal outcomes with minimal intervention from the attending anaesthetist.

TRIAL REGISTRATION

NCT03620942.

Intraoperative Vasopressor Usage in Free Tissue Transfer: Should We Be Worried?

BACKGROUND

 The role of vasopressors has long been a subject of debate in microsurgery. Conventional wisdom dictates the avoidance of vasopressor use, due to concerns such as peripheral vasoconstriction, inducing vasospasm of the anastomoses, and leading to failure in perfusion. It has since become common practice in some centers to avoid intraoperative vasopressor use during free tissue transfer surgery. Recent studies have suggested that this traditional view may not be supported by clinical evidence. However, none of these studies have separated vasopressor use by method of administration.

METHODS

 We conducted a retrospective review of our experience of vasopressor use in free flap surgery at a single high-volume center. The outcome measures were flap failure, flap-related complications and overall postoperative complications (reported using the Clavien-Dindo classification). Groups were compared using Chi-square or Fisher's Exact test where appropriate.

RESULTS

 A total of 777 cases in 717 patients were identified. 59.1% of these had vasopressors administered intraoperatively. The overall failure rate was 2.2%, with 9.8% experienced flap-related complications. There was no difference in flap loss when vasopressors were administered, but an increased rate of microvascular thrombosis was noted (p = 0.003). Continuous administration of vasopressors was associated with reduced venous congestion, whereas intermittent boluses increased risk of microvascular thrombosis.

CONCLUSION

 Our study confirms previous findings that intraoperative vasopressor use in free flap surgery is not associated with increased failure rate. Administering vasopressors continuously may be safer than via repeated boluses.

Heart rate variability and haemodynamic factors associated with hypotension during spinal anaesthesia for caesarean delivery: A case-control study

BACKGROUND

Hypotension frequently occurs during spinal anaesthesia for caesarean delivery, with potential adverse effects.

OBJECTIVE

To investigate heart rate variability and haemodynamic factors associated with spinal anaesthesia-induced hypotension.

DESIGN

Secondary case-control analysis of a randomised study.

SETTING

Single obstetric centre.

PATIENTS

Data were obtained from 230 healthy term singleton parturients who underwent elective caesarean delivery under spinal anaesthesia.

INTERVENTION

With parturients at rest, continuous haemodynamic measurements were recorded using a Nexfin cardiac monitor. Baseline pre-operative values were defined as the average of five minutes of continuous measurements. After initiation of standardised spinal anaesthesia, vasopressors were administered to maintain SBP within 10% of pre-operative values. Hypotension was defined as any 10 seconds average SBP less than 80% of pre-operative values from initiation of spinal anaesthesia to foetal delivery. Parturients were classified into cases (hypotensive) or controls (normotensive), and both univariate and multivariable logistic regression models were used to identify independent factors associated with hypotension.

MAIN OUTCOME MEASURES

Pre-operative standard deviation of the interbeat interval (SDNN), root mean square of successive interbeat difference, low-frequency to high-frequency ratio, SD1, SD2, approximate entropy, sample entropy, mean arterial pressure, SBP, stroke volume variation and systemic vascular resistance index were recorded, as were sensory block height, intravenous fluid volume and vasopressor use between spinal anaesthesia and foetal delivery.

RESULTS

Of 230 parturients, 113 (49.1%) experienced hypotension. Pre-operative lower SDNN [odds ratio (OR) 0.87, 95% confidence interval (CI) 0.78 to 0.97], higher SD2 (OR 25.06, 95% CI 2.41 to 261.06), and lower SBP (OR 0.98, 95% CI 0.97 to 1.00) were independently associated with hypotension. Between spinal anaesthesia to foetal delivery, lower sensory block height (OR 0.76, 95% CI 0.65 to 0.90) and higher intravenous fluid volume (OR 0.98, 95% CI 0.96 to 0.99 per 15 ml change) were associated with a lower incidence of hypotension. Area under the receiver operating characteristic curve was 0.701.

CONCLUSION

Pre-operative higher SD2, lower SDNN and lower SBP were associated with hypotension during spinal anaesthesia for caesarean delivery.

TRIAL REGISTRATION

NCT02277730.