Donald E. Hancock

Effect of injection site on circulation times during cardiac arrest.

Cardiopulmonary resuscitation requires effective, prompt drug administration. In order to analyze Advanced Cardiac Life Support (ACLS) recommendations for site of drug administration, we studied dye circulation times after central, femoral, and peripheral venous injection during both closed and open chest CPR using a canine arrest model. Measurements of circulation times were made after injection of indocyanine green dye at femoral, central, and peripheral venous sites. Circulation times during closed chest CPR were 62.7 +/- 19.6 sec after central injection, 86.6 +/- 23.5 sec after femoral injection, and 93.6 +/- 17.9 sec after peripheral injection (p less than .001). During closed chest CPR, peak dye concentration after central injection was significantly higher than that after peripheral injection (4.0 +/- 1.3 vs. 3.1 +/- 0.8 mg/L, p less than .01). Circulation times were significantly shorter during open chest CPR with times again shortest after central injection. This animal model suggests that prompt drug delivery during CPR is enhanced by central venous injection of medication. There appears to be no advantage in femoral over peripheral injection.

A comparison of venous blood gases during cardiac arrest

Previous reports have advocated the use of mixed venous blood gases to estimate arterial pH and as a reflection of tissue acid-based balance. However, true mixed venous samples are difficult to obtain during cardiac arrest as they require a pulmonary artery catheter. The purpose of this study was to determine whether central or femoral venous samples could be used in place of pulmonary artery samples. Blood gases from these sites were drawn at intervals during experimental cardiac arrest in dogs. The PO2, PCO2, and pH from the pulmonary artery samples were strongly correlated with those from the central venous (r = .93, .99, and .99, respectively) and from the femoral venous samples (r = .73, .93, and .97, respectively). There were no significant differences in the pulmonary artery, central, or femoral venous gases. This animal model suggests that femoral and central venous samples mirror true mixed venous blood gases from the pulmonary artery and could be used in their place.

Taping methods and tape types for securing oral endotracheal tubes.

PurposeTo evaluate tapes and taping methods with respect to the minimum force required to dislodge endo tracheal tubes (ETTs).MethodsA simulated face model consisting of a section of PVC pipe was used. The ETT was attached to a piezo-electric force transducer and pullout force was manually applied in a vertical, right or left direction. Five tape types were tested: Curity. Leukosilk, Hy.tape. Leukopore, and Transpore. Seven taping methods were used to secure the ETT The methods differed with respect to tape width and whether the tape was split along its longitudinal axis. Each taping condition was replicated 20 times (7 methods x 3 tapes x 3 directions) for a total of 2100 pullout tests.ResultsMinimum forces to dislodge ETTs were higher (P < 0.05) with Cunty tape (mean ± SD: 135 ± 75 N) than with the other tapes (Leukosilk: 93 ± 51 N, Hy.tape: 78 ± 34 N, Leukopore: 47 ± 32, and Transpore: 37 ± 23 N). The most secure taping method was achieved by taping the ETT, using 2.5 cm wide Cunty tape, in a circumferential fashion to both the upper and lower borders of the simulated mouth opening, and reinforcing these tapes with two strips applied longitudinally across the borders of the mouth opening (method 7). Taping methods which involved splitting the tape along its longitudinal axis resulted in lower minimal pullout forces when-ever the pullout force was directed towards the side of attachment (P < 0.05vs right and vertical direction).ConclusionThere are differences in ETT pullout forces and mechanisms of dislodgement depending on taping method and tape type.RésuméObjectifÉvaluer les rubans adhésifs et leurs modes d’ancrage par rapport à la force minimale requise pour déloger un tube endotrachéal (TET).MéthodesUn modèle de face simulé constitué d’une section de tube en CPV a été utilisé. Le TET était relié à un transducteur de force piézo-électrique et on appliquait sur le tube une traction verticale, vers la droite ou vers la gauche. Cinq marques de ruban adhésif ont été testées: Cunty. Leukosilk, Hy.tape, Leukopore et Transpore. Sept méthodes d’ancrage ont été utilisées pour la rétention du TET conformément à la largeur du ruban et selon qu’il était divisé sur son axe longitudinal ou non. Chaque méthode d’ancrage était mise à l’épreuve 20 fois (7 méthodes x 5 rubans x 3 directions) pour un total de 2100 tests.RésultatsAvec le ruban Cunty, la traction minimale requise pour déloger le tube était plus élevée (P < 0,05) (moyenne ± ET: 135 ± 75 N) qu’avec les autres rubans (Leukosilk 93 ± 52 N. Hy.tape 78 ± 34 N, Leukopore 47 ± 32 N et Transpore 37 ± 23 N). La méthode la plus efficace pour l’ancrage du TET consistait à faire le tour du tube avec deux rubans Cunty de 2.5 cm de large et de les fixer à la commissure du modèle buccal et de les renforcer avec deux rubans appliquées logitudimalement à travers les limites de l’ouverture buccale (méthodes 7). Les méthodes d’ancrage consistant à séparer le ruban en deux sur son axe longitudinal ont été les moins efficaces lorsque que la force d’extraction était dirigée du côté de l’attache (P < 0,05vs direction droite ou verticale).ConclusionLa force requise pour déloger un TET et les mécanismes de déplacement sont différents selon la méthode d’ancrage et le type de ruban adhésif utilisé.

The effect of bolus injection on circulation times during cardiac arrest

Previous investigations have shown that peripheral injection of medication during cardiac arrest leads to prolonged circulation times and low peak drug levels. Current Advanced Cardiac Life Support guidelines suggest that administering a bolus of flush solution after injection of medication may hasten drug delivery, but there is little evidence to support this. The purpose of this study is to investigate the effect of peripheral bolus injection on circulation times during cardiac arrest. Measurements of circulation times were made following injection of indocyanine green dye both with and without a bolus of 20 mL saline flush into a peripheral vein of mongrel dogs. There was no difference in systolic, diastolic, or coronary perfusion pressures during the injections with or without bolus injection. Similarly, there was no difference in end-tidal CO2 or in arterial-venous PO2, PCO2, or pH gradient. The circulation time without bolus injection was 77.7 +/- 42.7 seconds while circulation time with the saline flush was 48.3 +/- 20.9 seconds (P less than .001). Peak dye concentration without saline flush was 3.0 +/- 1.0 mg/L, and peak dye concentration with saline flush was 3.8 +/- 0.9 mg/L (P less than .001). We conclude that a bolus injection of 20 mL of saline enhances dye circulation times and peak levels during cardiac arrest in this animal model. The clinical application of this technique warrants further investigation.

Hemodynamic effects of the intra-aortic balloon pump during experimental cardiac arrest☆

The low flow states and limited coronary perfusion provided by conventional cardiopulmonary resuscitation (CPR) have prompted investigations into alternative, more invasive, methods of resuscitation. Previous case reports and limited animal evidence have suggested that the intra-aortic balloon pump (IABP) may have a role in resuscitation. We used a canine cardiac arrest model to study the hemodynamic effects of the IABP during closed-chest CPR. A sensor attached to the chest plate of a Thumper was used to time a Datascope Model 3520 ventricular assist console such that the balloon inflated on the upstroke and deflated on the downstroke of the Thumper. There was no increase in systolic blood pressure with the balloon pump. Diastolic blood pressure and coronary perfusion pressure were significantly higher with the IABP. Circulation times were shorter and end-tidal CO2 was higher with the IABP. It was concluded that the IABP improves hemodynamic parameters during experimental cardiac arrest.

The influence of tape type and of skin preparation on the force required to dislodge angiocatheters.

The study evaluated the effects of different techniques used to secure intravenous (iv) catheters. An angiocatheter attached to standard iv tubing was taped to human forearm using a standard taping method. A calibrated piezoelectric force transducer was attached to the iv tubing. The force applied along the longitudinal axis to pull out the taped catheter was measured and recorded on paper. Three tape types, Curity, Leukopor and Transpore, were evaluated alone, with benzoin skin pretreatment and with mastisol pretreatment. A randomized 3 × 3 block design with 20 replications per block was utilized, and a total of 180 pullout tests were performed on two adult volunteers. Without pretreatment, the forces required to dislodge catheters were (means ± SEM) 46 ± 2, 37 ± 2 and 38 ± 2 Newtons for Curity, Leukopor and Transpore tape, respectively. Corresponding values for mastisol pretreatment (64 ± 1,64 ± 3 and 52 ± 3 Newtons) were greater (P < 0.05) for each tape compared with benzoin (54 ± 3, 53 ± 2 and 40 ± 2 Newtons) and no pretreatment. The most frequent failure mode for Transpore tape was by tape fracture, for Curity tape was by separation from the skin of tape and catheter as a single unit, and for Leukopor tape was by catheter separation while tape remained attached to skin (P < 0.001). The data suggest that the application of mastisol prior to taping iv catheters with Curity or Leukopor tape helps to minimize the risk of accidental dislodgement.RésuméCette étude vise à évaluer l’efficacité de différentes méthodes de fixation à la peau des canules iv. Un canule veineuse reliée a une tubulure ordinaire est fixée avec un ruban adhésif sur l’avant-bras selon une méthode standard. Un transducteur piézo-électrique calibré est attaché à la tubulure. La force appliquée sur l’axe longitudinal de la canule nécessaire pour l’enlever est mesurée et enregistrée sur papier. Trois type de rubans adhesifs Curity, Leukopor et Transpore sont évalués seuls et apres preparation de la peau au benjoin et au mastisol. Un schema randomisé de blocs 3 × 3 avec 20 répliques par bloc est utilisé, et un total de 180 tests d’extraction sont pratiqués sur deux volontaires adultes. Sans préparation de la peau, la force requise pour déloger la canule est (moyenne ± SEM) 46 ± 2, 37 ± 2 et 38 ± 2 newtons respectivement pour les rubans adhésifs Curity, Leukopor et Transpore. Les valeurs correspondantes pour la préparation au mastisol (64 ± 1, 64 ± 3 et 52 ± 3 newtons) sont plus élevées (P < 0,05) pour chacun des rubans adhésifs comparativement au benjoin (54 ± 3, 53 ± 2 et 40 ± 2 newtons) et à l’absence de préparation. Pour le ruban Transpore, la source la plus importante d’échec a été le bris du ruban, pour le ruban Curity la séparation du ruban et du cathétr en un seul bloc, et pour le ruban Leukopor par la séparation du cathéter alors que le ruban demeure collé à la peau (P < 0,001). Ces données suggèrent que l’application de Mastisol avant la fixation de la canule avec du ruban adhésif Leukopor ou Curity en diminue le risque de déplacement.

Evaluation of different methods of securing intravenous catheters: measurement of forces during simulated accidental pullout

The purpose of the study was to compare the relative effectiveness of several combinations of tapes and taping methods with respect to the force required to pull out intravenous catheters. A simulated forearm model consisting of a section of firm PVC pipe was used for the first and second series of experiments. In the third experiment, one method of taping catheters was compared in the PVC model and in volunteers. Pull-out forces were measured with a force transducer and recorded on paper. In the first experiment, catheters secured with Curity tape resisted pullout to a greater extent than those with Transpore tape and provided approximately twice the force advantage (P < 0.05). In the second experiment using Curity tape, minimum forces to dislodge the catheters were (means ± SD) 53 ± 13, 82 ± 13, 113 ± 29, 124 ± 24, 176 ± 29 and 141 ± 46 N, for methods 1–6, respectively. In the third series, the minimum pullout forces were higher for Curity than with Transpore tape for both the human and simulated PVC forearm surfaces (63 ± 11 and 55 ± 12 N vs 52 ± 7 and 44 ± 12 N, P < 0.01), and the pullout forces were higher for the simulated vs the human skin surface for both tape types (P < 0.01). Compared with Curity tape, Transpore tape was more likely to fail by tape fracture in both the simulated and human skin surfaces (P < 0.05). The data suggest that there are important differences in pullout forces and mechanisms of dislodgement depending on taping method and tape type. Curity tape, using method 5 or 6, was superior to Transpore tape and the other taping methods in resisting pullout.RésuméCette étude vise à comparer l’efficacité relative de différentes combinaisons de ruban adhésif et méthodes de fixation par rapport à la force requise pour extraire une canule intraveineuse. Un modèle factice d’avant-bras composé d’une section de tube en CPV est utilisé pour la première et la deuxième série d’expériences. Pour la troisième série, la comparaison de la méthode de fixation de la canule se fait entre le modèle en CPV et des volontaires. La force nécessaire pour l’extraction est mesurée avec une jauge de contrainte et enregistrée sur papier. Au cours de la première expérience, les canules fixées avec du ruban Curity résistent environ deux foix mieux à l’extraction que celles qui sont fixées avec le ruban Transpore (P < 0,05). Au cours de la deuxième expérience avec le ruban Curity appliqué à la surface du membre factice, les forces minimales requises pour déplacer la canule sont respectivement de (moyenne ± SD) 53 ± 13, 82 ± 13, 113 ± 29, 124 ± 24, 176 ± 29 et de 141 ± 46 N avec les méthodes 1 à 6. Dans la troisième série, les forces minimales d’extraction sont plus élevées pour le ruban Curity que pour le Transpore tant sur la peau humaine que sur le membre factice (63 ± 11 et 55 ± 12 N vs 52 ± 7 et 44 ±12 N, P< 0,01); avec les deux rubans, la force d’extraction est plus élevée sur le bras factice que sur la peau humaine (P < 0,01). Comparativement au ruban Curity, le ruban Transpore est plus susceptible de se briser tant sur le bras factice que sur la peau humaine (P < 0,05). Ces données suggèrent que les méthodes de fixation et les types de ruban adhésif sont des facteurs déterminants sur les forces d’extraction et les mécanismes de déplacements des canules. Avec les méthodes 5 et 6, le ruban Curity résiste mieux à l’extraction que le ruban Transpore et que les autres méthodes.

Beat frequencies in high-frequency positive-pressure ventilation

Amplitude modulation of the waveforms of several cardiovascular variables was investigated during high-frequency (1.3 to 3.3 Hz) positive-pressure ventilation (HFPPV). The amplitude modulation of the pulmonary artery pressure wave was most prominent and its beat frequency (BF) was equal to the difference between the heart rate and the ventilation rate. Spectral analysis of the pulmonary artery pressure demonstrated well-defined peaks associated with the BF. No significant physiologic changes in either cardiovascular or pulmonary function were attributable to the presence of the beat phenomenon.

High-frequency positive-pressure ventilation with the MA-1 ventilator.

A conventional, low-frequency ventilator was modified to ventilate dogs at high frequencies of 85 to 185 cycle/min while cardiovascular and pulmonary variables were monitored. Although gas transport was adequate, cardiac output was diminished when compared to lowfrequency ventilation. The addition of an in-line pneumotachograph markedly increased PaCO2 during highfrequency ventilation. Carbon dioxide transport was primarily dependent upon the magnitude of the tidal volume at all high frequencies tested.

Dye circulation times during cardiac arrest

Dye dilution curves have been used to calculate cardiac output under conditions of normal circulation. Unfortunately, these curves cannot be integrated easily to determine cardiac output under the low flow states of CPR. The time to initial dye appearance (circulation time), may be useful in judging relative changes in flow when studying experimental resuscitation techniques. The purpose of this study was to investigate the relationship between dye circulation times and other hemodynamic measures during CPR. Repeated measurements of coronary perfusion pressure, dye circulation times, blood gases, and end-tidal CO2 (ETCO2) were made in dogs undergoing CPR. Dye circulation time was significantly associated with the systolic, diastolic, and coronary perfusion pressures. The correlation between circulation time and ETCO2 was -0.70 (P less than 0.0001). There was no correlation with the arterial-venous PO2 gradient. There were significant correlations between the circulation time and both the A-V PCO2 and the A-V pH gradients. We conclude that dye circulation times may be used to gauge relative changes in blood flow during CPR, particularly in laboratory investigations involving repeated measurements.